CN110630365A - Tail gas treatment system and hydrocarbon conversion efficiency calculation method and fault diagnosis method thereof - Google Patents

Tail gas treatment system and hydrocarbon conversion efficiency calculation method and fault diagnosis method thereof Download PDF

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CN110630365A
CN110630365A CN201910899476.6A CN201910899476A CN110630365A CN 110630365 A CN110630365 A CN 110630365A CN 201910899476 A CN201910899476 A CN 201910899476A CN 110630365 A CN110630365 A CN 110630365A
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hydrocarbon
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doc
dpf
thd
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CN110630365B (en
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齐宝华
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Nanjing science and gain environment protection science and technology co Ltd
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Nanjing science and gain environment protection science and technology co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/008—Mounting or arrangement of exhaust sensors in or on exhaust apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Analytical Chemistry (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention discloses a tail gas treatment system and a DPF temperature control system and a control method thereof, and the system comprises a catalyst conversion device, wherein the catalyst conversion device comprises a tail gas channel, a conical necking, a DOC (catalyst control) and a DPF, the tail gas channel is connected with an external hydrocarbon injection device, the upstream of the DOC is provided with a first temperature sensor, the upstream of the DOC is provided with a first pressure difference sensor, the upstream and the downstream of the DPF are respectively provided with a second temperature sensor and a third temperature sensor, and the DPF is provided with a second pressure difference sensor for measuring the outlet pressure of the DPF and the pressure difference passing through the DPF; the controller is respectively and electrically connected with the internal combustion engine, the first temperature sensor, the second temperature sensor, the third temperature sensor, the first differential pressure sensor and the second differential pressure sensor. According to the invention, whether the tail gas treatment system has faults can be accurately judged according to the hydrocarbon conversion efficiency of the DOC and the DPF, the fault type is prepared to be judged, the maintenance is carried out, and the maintenance judgment time is shortened.

Description

Tail gas treatment system and hydrocarbon conversion efficiency calculation method and fault diagnosis method thereof
Technical Field
The invention relates to a tail gas treatment system, in particular to a tail gas treatment system and a hydrocarbon conversion efficiency calculation method and a fault diagnosis method thereof.
Background
Exhaust gas discharged from an engine has been identified as a main cause of air pollution, and an exhaust gas treatment system has been used in the prior art to remove air pollutants from the exhaust gas. In exhaust gas treatment systems, Diesel Particulate Filters (DPFs) are typically used to trap Particulate Matter (PM), which may include unburned hydrocarbon particles (soot) and small amounts of other particles, such as metal oxide particles (ash). Particulate matter accumulates in the DPF and requires a regeneration process to remove the accumulated soot before the accumulation causes the engine's backpressure to be too high.
Typically, during regeneration, heat-generating devices are used to raise the exhaust temperature to a level where soot can be efficiently oxidized by oxygen, which in the process is provided by the exhaust of a lean-burn engine. The high temperature exhaust gas generated during regeneration passes through the DPF to oxidize the accumulated soot therein into carbon dioxide and water. Temperature control of the exhaust gas is therefore a critical factor in the regeneration process, too low a temperature may result in insufficient oxidation of soot, while too high a temperature may damage the DPF.
A variety of heat generating devices are available for the regeneration process, among which the most widely used are (fuel) burners and diesel oxidation catalyst Devices (DOCs). In the burner, hydrocarbons are supplied by a hydrocarbon metering and injection device, which injects the hydrocarbons into the combustion chamber. Whereas in a DOC device, hydrocarbons may be provided by the engine fuel control system during post injection or injected directly into the catalyst. The outboard hydrocarbon metering injection device can provide a more accurate hydrocarbon injection rate because hydrocarbons are not combusted prior to entering the catalyst, as compared to engine post-injection, which can lead to engine oil dilution, which can cause engine reliability problems.
However, the hydrocarbon metering jets used in fuel burners and DOC devices can have clogging or caking problems that can cause nozzle section clogging, creating temperature control problems. The problem of eliminating the residues after the hydrocarbon metering injection process is complete and using a better design to reduce the possibility of caking at the nozzle is some of the solutions currently in use. However, these methods are not very reliable due to the lack of efficient hydrocarbon separation from the high temperature tail gas.
The temperature control of the exhaust gas is also affected by the hydrocarbon conversion efficiency of the heat generating device and DPF. Ideally, the hydrocarbons delivered to the exhaust treatment system should be fully oxidized to avoid hydrocarbon emissions caused by the exhaust treatment system itself. However, there is a hydrocarbon leak, limited by the hydrocarbon conversion efficiency of the heat generating device. The hydrocarbon leakage level must be below the regulation limit when the DPF is uncatalyzed, and if the DPF is catalyzed, allows the heat generating device to have a higher hydrocarbon leakage level since the DPF can lower the hydrocarbon level in the tailpipe. The hydrocarbon leakage limit and the hydrocarbon conversion efficiency of the heat generating device and DPF determine the upper limit of the hydrocarbon injection rate. When the hydrocarbon conversion efficiency of the heat-generating device or DPF is too low, the hydrocarbon injection command may be limited to a level insufficient to regenerate the DPF. In this case, a fault needs to be triggered to avoid further damage to the DPF.
The low carbon-to-hydrogen conversion efficiency may be a "real" inefficiency caused by problems in the heat generating device and DPF (e.g., plugged DOC, sulfur poisoning, catalyst particle accumulation in the DOC or DPF, etc.), or a "show" inefficiency caused by hydrocarbon dosing problems (e.g., inaccurate hydrocarbon dosing). For systems with "real" inefficiencies, the problem can be solved by servicing the components (such as generating high temperature exhaust from the engine or replacing the DOC and DPF). However, if the inefficiency is only "displayed," it can be compensated for as long as the system is still capable, such as where hydrocarbon dosing injection is still capable of providing the desired hydrocarbon flow.
In addition to low efficiency, too high a hydrocarbon conversion efficiency may also occur. Like low hydrocarbon conversion efficiency, too high a hydrocarbon conversion efficiency may be "indicative" of too high an efficiency caused by hydrocarbon transport problems, or may be "true" of too high an efficiency. "real" over-efficiency, which is mainly caused by engine fuel system failure (such as the release of large amounts of unburned hydrocarbons into the heat-generating device), or the evaporation of hydrocarbon deposits at high temperatures.
Thus, there is a need to solve the above problems.
Disclosure of Invention
The purpose of the invention is as follows: the first purpose of the invention is to provide an exhaust gas treatment system.
It is a second object of the present invention to provide a method for calculating hydrocarbon conversion efficiency based on an exhaust gas treatment system.
It is a third object of the present invention to provide a fault diagnosis method based on the hydrocarbon conversion efficiency of an exhaust gas treatment system.
The technical scheme is as follows: in order to achieve the above purpose, the invention discloses an exhaust gas treatment system, which comprises a catalyst conversion device positioned at an exhaust gas discharge port of an exhaust manifold of an internal combustion engine, wherein the catalyst conversion device comprises an exhaust gas channel, a conical necking, a DOC and a DPF which are arranged along the exhaust gas outlet direction, an external hydrocarbon injection device is connected on the exhaust gas channel, a first temperature sensor is arranged at the upstream of the DOC, a first differential pressure sensor for measuring the upstream pressure of the DOC and the differential pressure passing through the conical necking is arranged at the upstream of the DOC, a second temperature sensor and a third temperature sensor are respectively arranged at the upstream and the downstream of the DPF, and a second differential pressure sensor for measuring the outlet pressure of the DPF and the differential pressure passing through the DPF; the controller is respectively electrically connected with the internal combustion engine, the first temperature sensor, the second temperature sensor, the third temperature sensor, the first differential pressure sensor and the second differential pressure sensor; the external hydrocarbon injection device comprises a control manifold, a fuel oil electromagnetic valve, a fuel injector, a pressure sensor, a buffer device and a controller, wherein the control manifold is provided with four ports, the ports of the control manifold are communicated with each other to form a hollow chamber, the pressure sensor is used for detecting the pressure of the chamber of the control manifold, the buffer device is used for providing damping for the control manifold, the controller is respectively electrically connected with the fuel oil electromagnetic valve, the fuel injector and the pressure sensor, one port of the control manifold is connected with a hydrocarbon source through the fuel oil electromagnetic valve, one port of the control manifold is connected with the fuel injector, one port of the control manifold is connected with the pressure; the controller controls the fuel oil electromagnetic valve to be electrified and opened, the hydrocarbon source enters the control manifold through the fuel oil electromagnetic valve and then flows to the fuel injector and is injected, the pressure sensor detects the hydrocarbon pressure in the control manifold and feeds the pressure back to the controller, and the controller controls the flow of injected hydrocarbon through controlling the on-off time of the fuel injector.
The invention relates to a method for calculating hydrocarbon conversion efficiency according to a tail gas treatment system, which comprises the following steps:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the second temperature sensor167)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)167) Comparing with a set threshold value Thd _ T167, and judging R (T)163) < Thd _ T163? and R (T)167) If the result is less than Thd _ T167?, ending the operation;
(3) calculating hydrocarbon energy Ef, wherein the Ef is equal to Ef + DxDF xLHV xT, D is the hydrocarbon conveying speed, DF is a degradation factor value, LHV is the low heating value of the hydrocarbon, and T is a repetition period;
(4) calculating the change in enthalpy of gas Eg, Eg ═ Eg + (T)167-T163)×CP×Mfe×T，T167Temperature sensing value, T, obtained for the second temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating the average hydrocarbon conversion efficiency eta of the DOCd，ηd＝Eg/Ef；
(7) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
The method comprises the following steps:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the third temperature sensor169)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)169) Comparing with a set threshold value Thd _ T169, judging R (T)163) < Thd _ T163? and R (T)169) If not, the operation is ended, if the result is Thd _ T169?;
(3) calculating hydrocarbon energy Ef, wherein the Ef is equal to Ef + DxDF xLHV xT, D is the hydrocarbon conveying speed, DF is a degradation factor value, LHV is the low heating value of the hydrocarbon, and T is a repetition period;
(4) calculating gas enthalpy change Eg, Eg ═ Egt + (T)169-T163)×CP×Mfe×T，T169Temperature sensing value, T, obtained for the third temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating total average hydrocarbon conversion efficiency of DOC and DPF
Figure BDA0002211339760000041
Figure BDA0002211339760000042
(7) According to total average hydrocarbon conversion efficiency
Figure BDA0002211339760000043
And average hydrocarbon conversion efficiency of DOCCalculating average Hydrocarbon conversion efficiency of DPF
Figure BDA0002211339760000045
Figure BDA0002211339760000046
(8) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
The invention relates to a fault diagnosis method based on a calculation method of hydrocarbon conversion efficiency of a tail gas treatment system, which comprises the following steps:
(1) average hydrocarbon conversion efficiency of DOC
Figure BDA0002211339760000047
Average hydrocarbon with DPFConversion efficiency
Figure BDA0002211339760000048
Comparing the ratio with a set threshold value Thd _ RS, and judging
Figure BDA0002211339760000049
If not, the operation is finished;
(2) triggering a sulfur poisoning fault prompt and ending the operation.
The invention relates to a fault diagnosis method for a hydrocarbon injection device of a tail gas treatment system, which comprises the following steps:
(1) if the fuel electromagnetic valve is not powered off?, if the fuel electromagnetic valve is not powered off (12);
(2) setting a timer TMR1 ═ TMR1+ T, where the value of the timer TMR1 is a detection time from the power-off of the fuel solenoid valve and the power-on of the fuel injector to the current time of the program execution, and T is a repetition period;
(3) calculating the expected hydrocarbon flow Dr by the formula
Figure BDA00022113397600000410
Wherein C isiIs the nozzle bore flow coefficient of the fuel injector, AiIs the minimum cross-sectional area of the nozzle hole, ρ is the density of the hydrocarbon, and P is the current pressure value in the control manifold;
(4) calculating the amount DM of the hydrocarbon flowing out within the detection time by using the expected hydrocarbon flow Dr, wherein DM is DM + Dr multiplied by T;
(5) comparing the TMR1 value of the timer with a set threshold value Thd _ T1, and judging whether TMR1 is greater than Thd _ T1? or not, and ending the operation;
(6) the fuel injector is powered off, and the fuel electromagnetic valve is powered on;
(7) calculating a difference value between the initial pressure value P0 and the current pressure value P, namely a pressure change value in the detection time, wherein delta P is P-P0;
(8) calculating the mass change quantity delta M of the hydrocarbons in the lower chamber,
Figure BDA0002211339760000051
a is a buffer deviceThe cross section area of the surface of the piston is arranged, and K is the spring constant of the spring;
(9) the degradation factor value DF is calculated,
Figure BDA0002211339760000052
(10) comparing the degradation factor value DF with a set threshold value Thd _ DFL and Thd _ DFH, judging whether DF is more than Thd _ DFH? or DF is less than Thd _ DFL?, and ending the operation if not;
(11) triggering a fault prompt in the hydrocarbon injection device, and ending the operation;
(12) the fuel oil electromagnetic valve is powered off, and the fuel injector is powered on;
(13) a reset timer TMR1 and the amount of hydrocarbon DM, that is, TMR1 and DM are reset to 0;
(14) and assigning the current pressure value P detected by the pressure sensor as P0, namely P0 is equal to P, and ending the operation.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
the degradation factor value detected by the invention can also be used for detecting the hydrocarbon conversion efficiency of the DOC and the DPF in the tail gas treatment system, and the invention can accurately judge whether the tail gas treatment system has faults or not according to the hydrocarbon conversion efficiency of the DOC and the DPF, prepare to judge the fault type, carry out maintenance and shorten the maintenance and judgment time.
Drawings
FIG. 1 is a schematic view of the structure of an exhaust gas treatment system according to the present invention;
FIG. 2 is a first schematic structural diagram of an external hydrocarbon injection device according to the present invention;
FIG. 3 is a first schematic structural diagram of an external hydrocarbon injection device according to the present invention;
FIG. 4 is a first schematic structural diagram of a buffering device according to the present invention;
FIG. 5 is a second schematic structural view of a buffering device according to the present invention;
FIG. 6 is a schematic view of the assembly of the air solenoid valve and the damper device according to the present invention;
FIG. 7 is a schematic diagram of a fault diagnosis process of the external hydrocarbon injection apparatus of the present invention;
FIG. 8 is a schematic view of a start-up procedure of the external hydrocarbon injection apparatus according to the present invention;
FIG. 9 is a schematic view of a purge flow of the external hydrocarbon injection apparatus of the present invention;
FIG. 10 is a first schematic diagram of a DPF temperature control system of the present invention;
FIG. 11 is a second schematic diagram of a DPF temperature control system of the present invention;
FIG. 12 is a flowchart illustrating a method for controlling the compensation coefficient module according to the present invention;
FIG. 13 is a graph illustrating the calculation of the average hydrocarbon conversion efficiency of a DOC according to the present invention;
FIG. 14 is a graph illustrating the calculation of the average hydrocarbon conversion efficiency of the DOC in accordance with the present invention;
FIG. 15 is a third schematic diagram of a DPF temperature control system of the present invention;
FIG. 16 is a fourth schematic diagram of a DPF temperature control system of the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
As shown in fig. 1, an exhaust gas treatment system according to the present invention includes an internal combustion engine 100, a catalytic converter 160 located at an exhaust gas discharge port of an exhaust manifold 101 of the internal combustion engine, the catalytic converter 160 including an exhaust passage 166, a tapered constriction 165, a DOC161, a DPF162, an external hydrocarbon injection device, a first temperature sensor 163, a first differential pressure sensor 164, a second temperature sensor 167, a third temperature sensor 169, a second differential pressure sensor 168, and a controller 150. The exhaust passage 166, the tapered constriction 165, the DOC161, and the DPF162 are arranged along an exhaust outlet direction, exhaust generated in the internal combustion engine 100 enters the exhaust passage 166 through the exhaust manifold 101, and the controller is an ECU. An external hydrocarbon injection device is arranged on the exhaust gas duct, by means of which hydrocarbon can be injected into the exhaust gas. A first temperature sensor 163 is disposed upstream of DOC161 and is connected to ECU150 via line 155. A first differential pressure sensor 164 is disposed upstream of DOC161 and is connected to ECU150 by connection 154, first differential pressure sensor 164 being operable to measure the pressure upstream of DOC161 and the pressure differential across tapered constriction 165. A second temperature sensor 167 is disposed upstream of the DPF and is connected to the ECU150 by a connection line 156; a third temperature sensor 169 is disposed downstream of the DPF and is connected to ECU150 by connection 158. A second differential pressure sensor 168 is disposed on the DPF and is connected to the ECU150 by connection 157, the second differential pressure sensor 168 being operable to measure the DPF outlet pressure and the differential pressure across the DPF. According to the invention, the controller is used for controlling the fuel oil electromagnetic valve to be electrified and opened, the hydrocarbon source enters the control manifold through the fuel oil electromagnetic valve and then flows to the fuel injector and is injected, the pressure sensor detects the pressure of the hydrocarbon in the control manifold and feeds the pressure back to the controller, and the controller realizes accurate control of the flow of the injected hydrocarbon by controlling the power-on and power-off time of the fuel injector.
During normal operation, reducing substances, such as carbon monoxide (CO) and unburned hydrocarbons, etc., emitted from the internal combustion engine 100 are oxidized in the DOC and the DPF (if coated with a catalyst). Meanwhile, soot collected in the DPF is burned off in the high temperature exhaust gas generated by oxidizing hydrocarbons injected from the fuel injector 130 through the DOC during the DPF regeneration. As shown in FIG. 1, hydrocarbons are supplied to the nozzle 130 from a hydrocarbon source 120 through a fuel solenoid valve 210 and a control manifold 230. During DPF regeneration, hydrocarbons are forced from port 121 of hydrocarbon source 120 into port 145 of the fuel solenoid valve and further flow from port 144 of control manifold 230 into port 131 of fuel injector 130. In an external hydrocarbon injection device, pressure sensor 250 sends hydrocarbon pressure to ECU150 via port 142 and line 151, while ECU150 controls hydrocarbon flow to fuel injector 130 via line 152 which is connected to port 211. Air trapped in the external hydrocarbon injection device is returned to the hydrocarbon storage tank through port 172 of solenoid valve 260 and release of the trapped air is controlled by ECU150 through signal line 176 connected to port 261 of solenoid valve 260. After DPF regeneration, to prevent hydrocarbon coking on the fuel injector surfaces, hydrocarbon residues may be removed by using compressed air provided by the compressed air source 125 through port 141 of the air solenoid valve 240, the compressed air flow may be controlled by the ECU150 through line 159 connected to port 146.
During DPF regeneration, exhaust gas temperatures need to be controlled to a certain range, with too high temperatures potentially damaging the DPF, and too low temperatures not sufficient to burn off soot in the DPF, resulting in regeneration failure. To control the exhaust gas temperature, it is desirable to control the flow of hydrocarbons through the fuel injector 130. And the flow of hydrocarbons may be controlled by controlling the opening time of fuel injector 130 in repeated control cycles. As shown in fig. 1, the supply control module 144 is configured to supply a pressure sensor 250 in the external hydrocarbon injection device, and information obtained from the engine 100 via line 155, which may include exhaust gas mass flow, engine fuel injection rate, engine speed, vehicle speed, and engine operating conditions, based on sensed values obtained from a first differential pressure sensor 164, a first temperature sensor 163, a second temperature sensor 167, a second temperature sensor 168, and a third temperature sensor 169, the opening time of the third temperature sensor 130 being controlled by the ECU150 via line 153 connected to port 132 of the third temperature sensor 130.
As shown in FIGS. 2 and 3, the function of the external hydrocarbon injection device is to control the flow of hydrocarbon through fuel injector 130. The invention relates to an external hydrocarbon injection device which comprises a control manifold 230, a fuel electromagnetic valve 210, a fuel injector 130, a pressure sensor 250, a buffer device 220, an air electromagnetic valve 240 and an electromagnetic valve 260. Control manifold 230 has 5 ports, 5 of which are respectively port 231, port 232, port 233, port 144 and port 223, 5 of which are interconnected to form hollow chamber 235.
Port 231 of control manifold 230 is connected to lower vent 222 of cushion 220 and functions to provide damping for the pressure in control manifold 230. Port 232 of control manifold 230 is connected to port 213 of fuel solenoid valve 210, port 145 of fuel solenoid valve 210 is connected to port 121 of hydrocarbon source 120, and fuel solenoid valve 210 is controlled by ECU150 via line 152 connected to port 211 of fuel solenoid valve 210. A pressure sensor 250 is connected to port 233 of control manifold 230 and port 142 of pressure sensor 250 is connected to ECU150 via connection 151, pressure sensor 250 being adapted to sense the pressure in control manifold chamber 235. The port 144 of the control manifold 230 is connected to the port 131 of the fuel injector 130, and the fuel injector 130 is controlled by the ECU150 through a line 153 connected to the port 132 of the fuel injector 130, the fuel injector 130 is provided with a coolant inlet 133, a coolant outlet 134, and a coolant passage communicating the coolant inlet and the coolant outlet, and the fuel injector 130 is provided in an exhaust passage 166, and in order to prevent the fuel injector 130 from overheating, the coolant circulates in the fuel injector from the coolant inlet 133 to the coolant outlet 134. Port 223 of the control manifold 230 is connected to port 262 of the solenoid valve 260, while the solenoid valve 260 is controlled by the ECU150 via line 176 connected to port 261 of the solenoid valve 260, to port 172 of the solenoid valve 260 being connected to an external hydrocarbon storage tank; the electromagnetic valve 260 can be a normally open electromagnetic valve (closed by power supply and opened by power supply) or a normally closed electromagnetic valve (opened by power supply and closed by power supply), and under the control of the ECU, the electromagnetic valve 260 is opened to release the air accumulated in the buffer device 220 and the control manifold 230, and to release part of the residual hydrocarbon in the buffer device 220 and the control manifold 230 after the DPF regeneration is finished.
When fuel solenoid valve 210 is energized open, hydrocarbons flow into hollow chamber 235 through port 145, port 213 of fuel solenoid valve 210, and port 232 of control manifold 230 under pressure provided by hydrocarbon source 120, pressure sensor 250 may sense the pressure within hollow chamber 235, and when fuel injector 130 is energized open, the flow of hydrocarbons through fuel injector 130 is determined by the pressure within hollow chamber 235; therefore, by adjusting the energization time of the fuel injector 130 in the repeated cycle according to the pressure value obtained from the pressure sensor 250, the hydrocarbon flow rate can be controlled.
When the DPF regeneration process is complete, both the fuel solenoid valve 210 and the fuel injector 130 are de-energized. If hydrocarbons are still trapped in the hollow chamber 235 of the control manifold 230 at this time, the adjacent hydrocarbons may be exposed to high temperatures because the nozzle tip of the fuel injector must be exposed to the exhaust gases. While high temperatures can coke the hydrocarbons, preventing them from flowing and reducing their metering injection performance. To reduce the chance of coking, compressed air may be introduced into the hydrocarbon injection device after the hydrocarbon metering injection process is completed to purge the remaining hydrocarbons.
As shown in FIG. 2, in the present invention, the port 221 of the buffer device 220 may be connected to the port 242 of the air solenoid valve 240, the port 141 of the air solenoid valve 240 is connected to the port 126 of the compressed air source 125, the port 241 of the air solenoid valve 240 is exposed to the outside environment or connected to an external hydrocarbon storage tank, and the solenoid valve 240 is controlled by the ECU150 through the line 159 connected to the port 146; after the hydrocarbon injection is complete, the ECU controls the air solenoid valve 240 to be energized open and compressed air is purged through the damper 220 into the control manifold 230. Alternatively, as shown in FIG. 3, the port 242 of the air solenoid valve 240 may be connected to the port 213 of the fuel solenoid valve 210 and the port 232 of the control manifold 230 by a three way connection, the port 141 of the air solenoid valve 240 being connected to the port 126 of the compressed air source 125, the port 241 of the air solenoid valve 240 being exposed to the outside environment or being connected to an external hydrocarbon storage tank, the solenoid valve 240 being controlled by the ECU150 via line 159 connected to the port 146; after hydrocarbon injection is complete, the ECU controls the air solenoid valve 240 to be energized open and compressed air is admitted to the control manifold 230 for purging via port 232.
As shown in fig. 4, the damping device 220 adopted by the present invention comprises a cylindrical body 301, a cover 307 at one end of the cylindrical body, and a connecting assembly 310 at the other end of the cylindrical body for sealing and communicating with the control manifold 230, wherein the inner cavity of the cylindrical body 301 is provided with a piston 303 dividing the inner cavity into an upper cavity 320 and a lower cavity 330, the outer wall of the piston 303 is provided with a groove 306, and the groove 306 is internally provided with an O-ring 304 for sealing; the upper chamber 320 is internally provided with a spring 302 with two ends respectively abutting against the cover body 307 and the piston 303, the cover body 307 is provided with an upper vent hole 221 which is communicated with the upper chamber 320 and can be externally connected with a hydrocarbon storage tank, the chamber 320 is connected back to the hydrocarbon storage tank by the port 221 through a male thread adapter 316, and leaked hydrocarbon can be discharged back to the hydrocarbon storage tank under the condition that the seal of the piston 303 fails. The connecting component 310 includes a connecting column having a plurality of step surfaces, the outer wall of the first-step cylinder and the outer wall of the second-step cylinder of the connecting column are respectively provided with a groove 312 and a groove 314, the grooves 312 and 314 are respectively provided with an O-ring 311 and an O-ring 313 for sealing, and the connecting column is provided with a lower vent 222 communicated with the lower chamber 330 and the control manifold. Two mounting flanges 308 with holes 309 are provided on the cylindrical body 301 to secure the damper 220 to the control manifold 230.
In the hydrocarbon injection apparatus shown in fig. 3, the damper device has the structure shown in fig. 4, and the solenoid valve 260 is selected to be a normally closed solenoid valve, and when the air solenoid valve 240 is energized, the fuel solenoid valve 210 and the fuel injector 130 are closed, and at the same time, the solenoid valve 260 is energized to be opened, so that the compressed air can press part of the residual hydrocarbon in the control manifold 230 and the damper device 220 back to the hydrocarbon storage tank through the solenoid valve 260, and the early cleaning is completed. Fuel injector 130 may then be opened and purging of remaining hydrocarbons may be accomplished with compressed air, after which fuel injector 130 may be closed.
As shown in fig. 2, if the air solenoid valve 240 is selected for purging, the piston 303 of the damping device 220 of the present invention is provided with a check valve 350 for conducting the upper chamber 320 to the lower chamber 330 in a single direction, so that the compressed air is delivered from the upper chamber 320 to the lower chamber 330, as shown in fig. 5. The air solenoid valve 240 is a three-way solenoid valve as shown in fig. 6, and when the air solenoid valve 240 is energized, the upper chamber 320 of the buffer device 220 is connected to the compressed air source, and when de-energized, the air solenoid valve 240 connects the upper chamber 320 to the outside environment. In order to reduce air release noise when the air solenoid valve 240 is de-energized, in fig. 6, a muffler 410 may be further included, a port 411 of which is connected with a port 241 of the air solenoid valve 240, and a port 412 of which is exposed to the external environment or connected to a hydrocarbon storage tank.
If an air solenoid valve is selected for connection to compressed air, as shown in fig. 2 and 3, a further portion of the compressed air may be accumulated in the control manifold 230 after purging when the solenoid valve 260 is selected to be a normally closed solenoid valve. Under the action of compressed air, hydrocarbon is difficult to permeate into the control manifold 230 from the fuel solenoid valve 210, and is difficult to permeate into exhaust gas from the control manifold 230 through the fuel injector 130, so that the phenomenon that coking caused by hydrocarbon leakage influences injection precision can be greatly reduced. If the air solenoid valve connected with compressed air is not selected, the solenoid valve 260 may be a normally open solenoid valve. Thus, when regeneration is complete, solenoid valve 260 is de-energized and opened, control manifold 230 is in communication with the hydrocarbon storage tank, and hydrocarbons that have permeated into control manifold 230 flow back to the hydrocarbon storage tank through solenoid valve 260, thereby bleeding pressure therefrom and mitigating hydrocarbon leakage through fuel injector 130.
In the external hydrocarbon injection device shown in fig. 2, if the air solenoid valve connected to the compressed air is not selected but the damper device shown in fig. 4 is used, when the fuel solenoid valve 210 is energized, hydrocarbon flows into the air chamber 235 under the pressure of the hydrocarbon source 120, forming pressure therein; the pressure in the hollow chamber 235 causes the piston 303 to move upward such that the volume of the lower chamber 330 increases. When a pressure P is applied, if the cross-sectional area of the piston surface is a, the spring constant of the spring 302 is K, and the friction effect and the mass of the spring and piston are negligible, the volume change Δ V of the lower chamber 330 is proportional to the change Δ P of the pressure P, i.e., the change Δ P is proportional to the change Δ V of the pressure P
ΔP＝K×ΔV/A2 (1)
When fuel solenoid valve 210 is de-energized in the absence of trapped air, the change in volume Δ V of lower chamber 330 is caused only by hydrocarbon release resulting from energizing fuel injector 130, i.e.
ΔV＝∫(D/ρ)dt (2)
D is the hydrocarbon delivery rate, i.e. the flow rate of hydrocarbon injected by the fuel injector, and ρ is the density of the hydrocarbon; the relationship between the hydrocarbon delivery rate D and the pressure in the hollow chamber 235 can be derived from the equation above as
Figure BDA0002211339760000101
The equation relationship may be used to detect degradation in hydrocarbon metering injection.
The invention discloses a method for calculating a degradation factor value of a hydrocarbon injection device based on an exhaust gas treatment system, which comprises the following steps of:
(1) if the fuel electromagnetic valve is not powered off?, if the fuel electromagnetic valve is not powered off (12);
(2) setting a timer TMR1 ═ TMR1+ T, where the value of the timer TMR1 is a detection time from the power-off of the fuel solenoid valve and the power-on of the fuel injector to the current time of the program execution, and T is a repetition period;
(3) calculating the expected hydrocarbon flow Dr by the formula
Figure BDA0002211339760000102
Wherein C isiIs the nozzle bore flow coefficient of the fuel injector, AiIs the minimum cross-sectional area of the nozzle hole, ρ is the density of the hydrocarbon, and P is the current pressure value in the control manifold;
(4) calculating the amount DM of the hydrocarbon flowing out within the detection time by using the expected hydrocarbon flow Dr, wherein DM is DM + Dr multiplied by T;
(5) comparing the TMR1 value of the timer with a set threshold value Thd _ T1, and judging whether TMR1 is greater than Thd _ T1? or not, and ending the operation;
(6) the fuel injector is powered off, and the fuel electromagnetic valve is powered on;
(7) calculating a difference value between the initial pressure value P0 and the current pressure value P, namely a pressure change value in the detection time, wherein delta P is P-P0;
(8) calculating the mass change quantity delta M of the hydrocarbons in the lower chamber,a is the cross-sectional area of the piston surface of the buffer device, and K is the spring constant of the spring;
(9) the degradation factor value DF is calculated,
Figure BDA0002211339760000112
according to the invention, when the fuel electromagnetic valve 210 is powered off, since the hydrocarbon is only provided by the buffer device 220, the hydrocarbon amount DM is equal to the mass change Delta M of the hydrocarbon in the lower chamber 330, and therefore, the calculated Delta M value and DM value can detect the problem in the hydrocarbon metering injection. Problems that result in a mismatch between the Δ M and DM values include nozzle problems with the fuel injector, such as nozzle blockage of the fuel injector by coking hydrocarbons, failure of the damper, such as a piston stuck in the damper, and the use of impure hydrocarbons or non-hydrocarbons, such as mixtures of hydrocarbons with air or water. The inventive method for diagnosing a malfunction of a hydrocarbon injection device based on an exhaust gas treatment system can be activated during a normal hydrocarbon dosing process or during a special diagnosis at the end of a hydrocarbon dosing process.
The hydrocarbon injection device fault diagnosis method based on the exhaust gas treatment system can be periodically operated in the ECU150 by a repetition period T. As shown in fig. 7, the method for diagnosing the fault of the hydrocarbon injection device based on the exhaust gas treatment system comprises the following steps:
(1) if the fuel electromagnetic valve is not powered off?, if the fuel electromagnetic valve is not powered off (12);
(2) setting a timer TMR1 ═ TMR1+ T, where the value of the timer TMR1 is the detection time from when the fuel solenoid valve 210 is powered off and the fuel injector 130 is powered on to the current time of program execution, and T is the repetition period;
(3) calculating the expected hydrocarbon flow Dr by the formula
，
Wherein C isiIs the nozzle bore flow coefficient of the fuel injector, AiIs the minimum cross-sectional area of the nozzle hole, ρ is the density of the hydrocarbon, and P is the current pressure value in the control manifold;
(4) calculating the amount DM of the hydrocarbon flowing out within the detection time by using the expected hydrocarbon flow Dr, wherein DM is DM + Dr multiplied by T;
(5) comparing the TMR1 value of the timer with a set threshold value Thd _ T1, and judging whether TMR1 is greater than Thd _ T1? or not, and ending the operation;
(6) the fuel injector is powered off, and the fuel electromagnetic valve is powered on;
(7) calculating a difference value between the initial pressure value P0 and the current pressure value P, namely a pressure change value in the detection time, wherein delta P is P-P0;
(8) calculating the mass change quantity delta M of the hydrocarbons in the lower chamber,
Figure BDA0002211339760000121
，
a is the cross-sectional area of the piston surface of the buffer device, and K is the spring constant of the spring;
(9) the degradation factor value DF is calculated,
Figure BDA0002211339760000123
(10) comparing the degradation factor value DF with a set threshold value Thd _ DFL and Thd _ DFH, judging whether DF is more than Thd _ DFH? or DF is less than Thd _ DFL?, and ending the operation if not;
(11) triggering a fault prompt in the hydrocarbon injection device, namely triggering a fault label F1, and ending the operation;
(12) the fuel oil electromagnetic valve is powered off, and the fuel injector is powered on;
(13) a reset timer TMR1 and the amount of hydrocarbon DM, that is, TMR1 and DM are reset to 0;
(14) and assigning the current pressure value P detected by the pressure sensor as P0, namely P0 is equal to P, and ending the operation.
To prevent coking caused by hydrocarbon residue in air chamber 235 and fuel injector 130, an air solenoid valve in communication with compressed air may be used to purge the hydrocarbon residue, as shown in FIG. 2. When using the air solenoid valve 240 as shown in FIG. 6, the activation and purging of the hydrocarbon injection device of FIG. 2 may be controlled by a control routine running in the ECU 150.
As shown in fig. 8, the invention relates to a hydrocarbon injection device start preparation control method based on an exhaust gas treatment system, which comprises the following steps:
(1) first, the solenoid valve 260 is energized to open to release the air trapped in the damper device 220 and the control manifold 230;
(2) comparing the current pressure value P detected by the pressure sensor 250 with a set threshold value Thd _ LP, and judging that P is less than Thd _ LP
(3) After the accumulated air is released, that is, when the measured pressure value P is lower than the threshold value Thd _ LP, the fuel solenoid valve 210 is energized and opened, and after the delay Time _ delay1 reaches the point where the hydrocarbon is filled in the buffer device 220 and the control manifold 230, the solenoid valve 260 is de-energized;
(4) after fuel injector 130 is energized and opened and delay Time _ delay2 is reached, fuel injector 130 is de-energized until the air trapped in fuel injector 130 is completely released;
(5) and setting a measured hydrocarbon injection mark as Prime _ completed, and completing the starting preparation of the external hydrocarbon injection device.
As shown in fig. 9, the purge control method for a hydrocarbon injection device based on an exhaust gas treatment system according to the present invention includes the following steps:
(1) de-energizing fuel solenoid valve 210 to close and cut off hydrocarbon supply, and energizing solenoid valve to open to release some of the hydrocarbons trapped in snubber assembly 220 and control manifold 230;
(2) comparing the current pressure value P detected by the pressure sensor 250 with a set threshold value Thd _ Pmin, and judging that P is less than Thd _ Pmin
(3) When the current pressure value P is smaller than the set threshold value Thd _ Pmin, the electromagnetic valve is powered off;
(4) simultaneously electrifying and opening the fuel injector 130 and the air solenoid valve 240 to purge the residual hydrocarbon, and delaying the Time _ delay3 until the hydrocarbon accumulated in the external hydrocarbon injection device is completely released, and then powering off the fuel injector 130 and the air solenoid valve 240;
(5) and setting a hydrocarbon metering injection mark as pumping _ completed, and finishing the Purging of the external hydrocarbon injection device.
After the purge process is completed, compressed air is accumulated in the hydrocarbon injection device, which will prevent hydrocarbons from leaking through the fuel solenoid valve 210 when the accumulated air pressure is higher than the hydrocarbon supply pressure; thus, the possibility of coking is further reduced. In order to maintain the air pressure in the control manifold 230 above the hydrocarbon supply pressure, which may leak out and thus cause pressure loss, when the pressure sensing value obtained from the pressure sensor 250 is low, the air solenoid valve 240 may be refilled with compressed air by momentarily energizing the air solenoid valve 240 to control the pressure, but this pressure control is disabled during regeneration.
After the degradation factor value DF is detected by the fault diagnosis method of the hydrocarbon injection device based on the exhaust gas treatment system, the accuracy of the measured injection of the hydrocarbon can be compensated in the temperature control during the regeneration of the DPF. As shown in fig. 10, the DPF temperature control system based on the exhaust gas treatment system of the present invention includes a DOC target temperature calculation module 601, a change rate limiter 602, a feedforward controller 603, a PID controller 604, a PWM calculation module 605 and a compensation module 606; the DOC target temperature calculation module 601 calculates a DOC target temperature DOCT _ target according to the DPF target temperature DPFT _ target, the change rate limiter 602 calculates a DOC temperature command value according to the DOC target temperature DOCT _ target and the DOC outlet temperature measured by the second temperature sensor 167, the PID controller 604 calculates a PID control value according to an error value obtained by comparing the DOC temperature command value with the DOC outlet temperature, and the feedforward controller 603 calculates a feedforward control value according to the DOC temperature command value, the DOC inlet temperature measured by the first temperature sensor 163 and the tail gas mass flow value; the PWM calculation module 605 calculates a PWM command 610 by adding a calculated value obtained by multiplying the PID control value by the exhaust mass flow value after nonlinear compensation and a feed-forward control value and a hydrocarbon supply pressure value, the compensation module 606 calculates a PWM duty ratio by the PWM command and the degradation factor value DF, generates a PWM duty ratio value to control the flow rate of the hydrocarbon by controlling the fuel injector 130, the hydrocarbon injected from the fuel injector 130 is oxidized in the DOC161, and heats the exhaust temperature so that the DOC outlet temperature sensing value reaches the DOC temperature command value calculated by the change rate limiter 602.
As shown in fig. 10, the method for controlling the DPF temperature control system based on the exhaust gas treatment system of the present invention includes the following steps:
the DPF target temperature DPFT _ target is transmitted to a DOC target temperature calculation module 601, the DOC target temperature calculation module 601 calculates the DOC target temperature DOCT _ target according to the DPF target temperature DPFT _ target, and transmits the DOC target temperature DOCT _ target to a change rate limiter 602; the second temperature sensor 167 transmits the measured DOC outlet temperature to the change rate limiter 602, and the change rate limiter 602 calculates a DOC temperature command value according to the DOC target temperature DOCT _ target and the DOC outlet temperature measured by the second temperature sensor 167, and transmits the DOC temperature command value to the feedforward controller 603; transmitting an error value obtained by comparing the DOC outlet temperature with the DOC temperature command value to the PID controller 604, and calculating a PID control value by the PID controller 604 according to the error value; transmitting the DOC inlet temperature and the exhaust mass flow value measured by the first temperature sensor 163 to the feedforward controller 603, and calculating a feedforward control value by the feedforward controller 603 according to the DOC temperature command value, the DOC inlet temperature and the exhaust mass flow value; the calculated value obtained by adding the PID control value multiplied by the tail gas mass flow value and the feed-forward control value is transmitted to the PWM calculation module 605, the PWM calculation module 605 calculates a PWM instruction 610 according to the calculated value and the hydrocarbon supply pressure value, the PWM instruction 610 is transmitted to the compensation module 606, and the compensation module 606 calculates the PWM duty ratio according to the PWM instruction 610 and the degradation factor value DF.
As shown in fig. 11, another DPF temperature control system based on an exhaust gas treatment system according to the present invention includes a DOC target temperature calculation module 601, a change rate limiter 602, a feedforward controller 603, a PID controller 604, a PWM calculation module 605, and a compensation coefficient module 611; the DOC target temperature calculation module 601 calculates a DOC target temperature DOCT _ target according to the DPF target temperature DPFT _ target, the change rate limiter 602 calculates a DOC temperature command value according to the DOC target temperature DOCT _ target and the DOC outlet temperature measured by the second temperature sensor, the PID controller 604 calculates a PID control value according to an error value obtained by comparing the DOC temperature command value with the DOC outlet temperature, and the feedforward controller 603 calculates a feedforward control value according to the DOC temperature command value, the DOC inlet temperature measured by the first temperature sensor and the tail gas mass flow value; the PWM calculation module 605 calculates a PWM command according to a calculated value obtained by adding the PID control value multiplied by the exhaust gas mass flow value and the feedforward control value and a hydrocarbon supply pressure value, the compensation coefficient module 611 obtains a compensation factor according to the state vector value and the degradation factor value DF, and the PWM command is multiplied by the compensation factor to obtain a PWM duty ratio. The state vector value indicates the effectiveness of the external hydrocarbon injection device, the DOC inlet temperature, the DOC outlet temperature, the DPF outlet temperature and the tail gas mass flow value.
As shown in fig. 11, the method for controlling the DPF temperature control system based on the exhaust gas treatment system of the present invention includes the following steps:
the DPF target temperature DPFT _ target is transmitted to a DOC target temperature calculation module 601, the DOC target temperature calculation module 601 calculates the DOC target temperature DOCT _ target according to the DPF target temperature DPFT _ target, and transmits the DOC target temperature DOCT _ target to a change rate limiter 602; second temperature sensor 167 transmits the measured DOC outlet temperature to rate of change limiter 602, and rate of change limiter 602 calculates a DOC temperature command value according to DOC target temperature DOCT _ target and the DOC outlet temperature measured by second temperature sensor 167, and transmits to feedforward controller 603; transmitting an error value obtained by comparing the DOC outlet temperature with the DOC temperature command value to the PID controller 604, and calculating a PID control value by the PID controller 604 according to the error value; transmitting the DOC inlet temperature and the exhaust mass flow value measured by the first temperature sensor 163 to the feedforward controller 603, and calculating a feedforward control value by the feedforward controller 603 according to the DOC temperature command value, the DOC inlet temperature and the exhaust mass flow value; the calculated value obtained by adding the PID control value multiplied by the tail gas mass flow value and the feed-forward control value is transmitted to the PWM calculation module 605, the PWM calculation module 605 calculates according to the calculated value and the hydrocarbon supply pressure value to obtain a PWM instruction 610, the state vector value and the degradation factor value DF are transmitted to the compensation coefficient module 611, the compensation coefficient module 611 obtains a compensation factor according to the state vector value and the degradation factor value DF, and the PWM instruction 610 is multiplied by the compensation factor to obtain the PWM duty ratio.
The DOC target temperature calculation module 601, the feedforward controller 603 and the PWM calculation module 605 may be implemented by using a table lookup method, and the table therein may be determined by a calibration process. The function of the change rate limiter 602 is to provide a temperature profile for limiting the rate of change of temperature so that the temperature gradient and thermal stress in the DOC and DPF can be controlled to be low, and the change rate limiter 602 can be implemented using a table lookup and then cooperating with a change rate limiting algorithm, that is, when the change rate of the output value obtained by table lookup is greater than a certain set value, the final output value is equal to the table lookup output value changed at the set value. The PID controller 604 can be implemented using a conventional PID algorithm. The compensation module 606 compensates the PWM command with the DF value can be implemented in a variety of ways. In fig. 11, the degradation factor value DF is used together with a state vector value indicating the validity of the sensed values of the actuators, i.e., the hydrocarbon injection devices, and the sensors, including the sensed values obtained by the first temperature sensor 163, the second temperature sensor 167, and the third temperature sensor 169, and the mass flow rate sensed value, to calculate the compensation factor value. The compensation coefficient module 611 may be implemented by the control method shown in fig. 12. In the control method of the compensation coefficient module, the compensation factor is calculated only when the state vector values show that the sensed values of the actuator and the sensor are valid, that is, errors of the actuator and the sensor are not reported; if the state vector value indicates invalidity, the compensation factor is not calculated and only its previous value is used. The compensation factor value calculated in the compensation factor module 611 is multiplied by the PWM command 610 to generate a PWM duty cycle; while a simple method for calculating the compensation factor value is to use a look-up table with DF values as input.
As shown in fig. 12, the control method of the compensation coefficient module of the present invention includes the steps of:
(1) if the state vector value is judged to be valid?, turning to (3);
(2) obtaining a compensation factor according to a table look-up method with the degradation factor value DF as input;
(3) and assigning the previous value of the compensation factor as the current compensation factor.
In addition to being applied to temperature control, the degradation factor value DF may also be used to calculate the hydrocarbon conversion efficiency of the DOC. As shown in FIG. 1, the exotherm generated in DOC161 is primarily provided by oxygenated hydrocarbons, so the difference between the temperature sensing values obtained from first temperature sensor 163 and second temperature sensor 167 is a function of the amount of hydrocarbons in the exhaust stream:
(T167-T163)×CP×Mfe+mDOC×Cm×TDOC+Pe＝D×DF×ηd×LHV (6)
wherein T is167And T163Temperature sensing values, C, obtained from the first temperature sensor 163 and the second temperature sensor 167PIs the constant pressure heat capacity of the tail gas, MfeIs the mass flow of the tail gas, mDOCIs the mass of the DOC, CmIs the heat capacity of DOC, TDOCIs the mean temperature of the DOC, PeIs the heat exchange power between DOC and the environment, etadFor hydrocarbon conversion efficiency, LHV is the lower heating value of the hydrocarbon. In the above formula, in steady state, i.e. when the temperature T is negligible, the heat exchange between the DOC and the environment is negligibleDOCWhen held constant, the above equation can be simplified to:
(T167-T163)×CP×Mfee＝D×DF×ηd×LHV (7)
the hydrocarbon conversion efficiency eta can be calculateddIs etad＝D×DF×LHV/[(T167-T163)×CP×Mfe] (8)
The average hydrocarbon conversion efficiency may be calculated
Figure BDA0002211339760000161
As shown in fig. 13, the present invention may calculate the average hydrocarbon conversion efficiency of the DOC using a timer interrupt service routine that is periodically run, and the present invention relates to a method for calculating the hydrocarbon conversion efficiency of the DOC based on an exhaust gas treatment system, including the following steps:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the second temperature sensor167)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)167) Comparing with a set threshold value Thd _ T167, and judging R (T)163) < Thd _ T163? and R (T)167) If the result is less than Thd _ T167?, ending the operation;
(3) calculating hydrocarbon energy Ef, wherein Ef is equal to Ef + D multiplied by DF multiplied by LHV multiplied by T, D is the hydrocarbon conveying speed, DF is the degradation factor value, LHV is the low heat value of the hydrocarbon, T is the repetition period, namely the interruption time period, and the energy Ef is calculated once every T seconds;
(4) calculating the change in enthalpy of gas Eg, Eg ═ Eg + (T)167-T163)×CP×Mfe×T，T167Temperature sensing value, T, obtained for the second temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating the average hydrocarbon conversion efficiency of the DOC
Figure BDA0002211339760000171
Figure BDA0002211339760000172
(7) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
Efficiency of hydrocarbon conversion etadAnd average hydrocarbon conversion efficiency
Figure BDA0002211339760000173
Which is an indicator of DOC performance, the low carbon-to-hydrogen conversion efficiency of DOC may cause problems including hydrocarbon leakage leading to emission problems and low regeneration temperature of DPF, which in turn may cause uneven distribution of soot within DPF, leading to reliability problems. To avoid using problematic DOC regeneration, a fault needs to be reported once low carbon to hydrogen conversion efficiency is detected.
In the event of a low hydrocarbon efficiency failure being triggered, DPF regeneration needs to be disabled. However, the problem is not always solved by replacing the DOC. Possible causes of low carbon to hydrogen conversion efficiency include partial plugging of the DOC front face, poisoning and damage to the catalyst sulfur. Generally, DOC front face partial plugging and sulfur poisoning is recoverable, and at high temperatures, soot plugging the DOC front face and sulfur compounds that degrade DOC performance may be removed. However, catalyst damage, such as that caused by the aggregation of platinum catalyst particles at high temperatures, is not recoverable. These two different factors can be distinguished by using high temperature exhaust streams that can be generated by operating the engine in a high torque mode and/or combusting additional fuel in the engine using post injection techniques. After a period of time with the high temperature exhaust stream, if the conversion efficiency recovers, then the low carbon to hydrogen conversion efficiency is due to recoverable factors, otherwise the DOC needs to be replaced.
In addition to triggering a fault, the DOC hydrocarbon conversion efficiency value may also be used to limit the flow of hydrocarbons to avoid excessive hydrocarbon leakage or excessive temperature gradients in the catalyst coated DPF. The flow limit may be placed before the PWM control signal is generated. As shown in fig. 15, the DPF temperature control system based on the exhaust gas treatment system of the present invention includes a DOC limit calculation module 900, a feedforward controller 603, a PID controller 604, a minimum calculation module 905, and a PWM calculation module 610; the DOC limit value calculation module 900 calculates a hydrocarbon flow limit value according to the hydrocarbon content at the maximum allowable DOC outlet and the hydrocarbon conversion efficiency of the DOC, the feedforward controller 603 outputs a feedforward control value, the PID controller 604 outputs a PID control value, the PID control value is multiplied by the tail gas mass flow value and then added with the feedforward control value to obtain a calculated value, the minimum value calculation module 905 outputs the minimum value of the calculated value and the hydrocarbon flow limit value according to the calculated value and the hydrocarbon flow limit value, and the PWM calculation module 610 calculates a PWM instruction according to the minimum value and the hydrocarbon supply pressure value. The maximum allowable hydrocarbon content at the outlet of the DOC can be further determined by the maximum allowable hydrocarbon content at the outlet of the DPF and the working state of the DPF, and meanwhile, through the calculated DOC hydrocarbon conversion efficiency, the limiting value of the hydrocarbon flow can be determined according to the following formula:
，
wherein DmaxIs a limit value of the hydrocarbon flow, CHCDIs the highest allowable hydrocarbon content allowed at the DOC outlet.
As shown in fig. 15, the method for controlling the DPF temperature control system based on the exhaust gas treatment system of the present invention includes the following steps: the hydrocarbon content and the hydrocarbon conversion efficiency of the DOC at the maximum allowable DOC outlet are transmitted to a DOC limit value calculation module 900, the DOC limit value calculation module 900 calculates a hydrocarbon flow limiting value according to the hydrocarbon content and the hydrocarbon conversion efficiency of the DOC at the maximum allowable DOC outlet, and transmits the hydrocarbon flow limiting value to a minimum value calculation module 905; the feedforward controller 603 outputs a feedforward control value, the PID controller 604 outputs a PID control value, a calculated value obtained by adding a value obtained by multiplying the PID control value by the tail gas mass flow value and the feedforward control value is transmitted to a minimum value calculating module 905, the minimum value calculating module 905 outputs the minimum value of the calculated value and the hydrocarbon flow limiting value according to the calculated value and transmits the minimum value to the PWM calculating module 605, the hydrocarbon supply pressure value is transmitted to the PWM calculating module 605, and the PWM calculating module 605 calculates the PWM instruction 610 according to the minimum value and the hydrocarbon supply pressure value.
The calculated hydrocarbon conversion efficiency value may be higher than 100%, an excessively high hydrocarbon conversion efficiency indicating a high hydrocarbon level in the engine exhaust air, which may further indicate the presence of an additional hydrocarbon supply in the system. This additional hydrocarbon feed may be a fuel system problem for the engine (such as a fuel nozzle seizure problem) or may be a hydrocarbon deposit problem. The problem of hydrocarbon deposition arises because at low temperatures hydrocarbon droplets are retained by impingement on the inner walls of the exhaust pipe, and as the exhaust temperature increases, the retained hydrocarbons evaporate to produce an excess flow of hydrocarbons. Excessive hydrocarbon conversion efficiency due to deposited hydrocarbons only occurs during transients in exhaust gas temperature from low to high. If there is an excessive hydrocarbon conversion efficiency over a long period of time, a malfunction of the engine's fuel system is triggered. The detection of this failure may be achieved by detecting an excessively high hydrocarbon conversion efficiency for a long time using the DOC hydrocarbon conversion efficiency calculation method as shown in fig. 13. In this routine, the threshold value Thd _ Ef is the minimum hydrocarbon energy required to calculate the average hydrocarbon conversion efficiency value. If Thd Ef is set higher than the energy of the deposited hydrocarbons, an excessive hydrocarbon conversion efficiency indicates a long-term additional hydrocarbon supply, meaning that the engine system is malfunctioning.
As shown in fig. 1, if the heat exchange between the exhaust gas and the environment is negligible in the catalyst converter 160, according to equation (8), if the temperature sensing value T acquired from the third temperature sensor 169 is used169Instead of T167Meanwhile, the total hydrocarbon conversion efficiency eta of the DOC and the DPF is assumed that the heat released by burning the soot is negligible compared with the heat released by oxidizing the hydrocarbonaThe following formula can be used:
ηa＝(D×DF×LHV)/[(T169-T163)×CP×Mfe] (11)
total hydrocarbon conversion efficiency etaaAnd DOC Hydrocarbon conversion efficiency etadCan be further used to calculate the DPF hydrocarbon conversion efficiency eta according to the following formulaf：
ηf＝(ηa-ηd)/(1-ηd) (12)
The average total hydrocarbon conversion efficiency may be calculated using the DPF hydrocarbon conversion efficiency calculation method based on the exhaust gas treatment system as shown in fig. 14And the average DOC hydrocarbon conversion efficiency
Figure BDA0002211339760000192
Together, the average DPF hydrocarbon conversion efficiency is calculated according to equation (12)
Figure BDA0002211339760000193
Like DOC hydrocarbon conversion efficiency, DPF hydrocarbon conversion efficiency is an indication of DPF performance, and when low DPF hydrocarbon conversion efficiency is detected, a fault is triggered.
As shown in fig. 14, the method for calculating the DPF hydrocarbon conversion efficiency based on the exhaust gas treatment system of the present invention includes the following steps:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the third temperature sensor169)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)169) Comparing with a set threshold value Thd _ T169, judging R (T)163) < Thd _ T163? and R (T)169) If not, the operation is ended, if the result is Thd _ T169?;
(3) calculating hydrocarbon energy Ef, wherein Ef is equal to Ef + D multiplied by DF multiplied by LHV multiplied by T, D is the hydrocarbon conveying speed, DF is the degradation factor value, LHV is the low heat value of the hydrocarbon, T is the repetition period, namely the interruption time period, and the energy Ef is calculated once every T seconds;
(4) calculating gas enthalpy change Eg, Eg ═ Egt + (T)169-T163)×CP×Mfe×T，T169Temperature sensing value, T, obtained for the third temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating total average hydrocarbon conversion efficiency of DOC and DPF
Figure BDA0002211339760000201
Figure BDA0002211339760000202
(7) Reset Ef and Eg, i.e. Ef and Eg are reset to 0;
(8) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the second temperature sensor167)，
(9) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)167) Comparing with a set threshold value Thd _ T167, and judging R (T)163) < Thd _ T163? and R (T)167) If the result is less than Thd _ T167?, ending the operation;
(10) calculating hydrocarbon energy Ef, wherein Ef is equal to Ef + D multiplied by DF multiplied by LHV multiplied by T, D is the hydrocarbon conveying speed, DF is the degradation factor value, LHV is the low heat value of the hydrocarbon, T is the repetition period, namely the interruption time period, and the energy Ef is calculated once every T seconds;
(11) calculating the change in enthalpy of gas Eg, Eg ═ Eg + (T)167-T163)×CP×Mfe×T，T167Temperature sensing value, T, obtained for the second temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(12) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(13) calculating the average hydrocarbon conversion efficiency of the DOC
Figure BDA0002211339760000203
Figure BDA0002211339760000204
(14) According to total average hydrocarbon conversion efficiency
Figure BDA0002211339760000205
And average hydrocarbon conversion efficiency of DOC
Figure BDA0002211339760000206
Calculating average Hydrocarbon conversion efficiency of DPF
Figure BDA0002211339760000208
(15) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
The DPF hydrocarbon conversion efficiency may also be used to determine the maximum allowable hydrocarbon content at the DOC outlet to limit the flow of hydrocarbons. As shown in fig. 16, the DPF temperature control system based on the exhaust gas treatment system of the present invention comprises a DPF limit calculation module 910, a DOC limit calculation module 900, a feedforward controller 603, a PID controller 604, a minimum value calculation module 905, and a PWM calculation module 610; the DPF limit value calculation module 910 calculates the hydrocarbon content at the maximum allowable DOC outlet according to the hydrocarbon content at the maximum allowable DPF outlet and the hydrocarbon conversion efficiency of the DPF, the DOC limit value calculation module 900 calculates the hydrocarbon flow limit value according to the hydrocarbon content at the maximum allowable DOC outlet and the hydrocarbon conversion efficiency of the DPF, the feedforward controller 603 outputs a feedforward control value, the PID controller 604 outputs a PID control value, the PID control value is multiplied by the exhaust mass flow value and then added to the feedforward control value to obtain a calculated value, the minimum value calculation module 905 outputs the minimum value of the calculated value and the hydrocarbon flow limit value according to the exhaust mass flow value, and the PWM calculation module 605 calculates the PWM command 610 according to the minimum value and the hydrocarbon supply pressure value.
As shown in fig. 16, the method for controlling the DPF temperature control system based on the exhaust gas treatment system according to the present invention includes the steps of:
the hydrocarbon content at the maximum allowable DPF outlet and the DPF hydrocarbon conversion efficiency are transmitted to a DPF limit value calculation module 910, and the DPF limit value calculation module 910 calculates the hydrocarbon content at the maximum allowable DOC outlet according to the hydrocarbon content at the maximum allowable DPF outlet and the DPF hydrocarbon conversion efficiency and transmits the hydrocarbon content to a DOC limit value calculation module 900; the DOC hydrocarbon conversion efficiency is transmitted to a DOC limit value calculation module 900, the DOC limit value calculation module 900 calculates a hydrocarbon flow limiting value according to the hydrocarbon content at the maximum allowable DOC outlet and the DOC hydrocarbon conversion efficiency, and transmits the hydrocarbon flow limiting value to a minimum value calculation module 905; the feedforward controller 603 outputs a feedforward control value, the PID controller 604 outputs a PID control value, a calculated value obtained by adding a value obtained by multiplying the PID control value by the tail gas mass flow value and the feedforward control value is transmitted to a minimum value calculating module 905, the minimum value calculating module 905 outputs the minimum value of the calculated value and the hydrocarbon flow limiting value according to the calculated value and transmits the minimum value to the PWM calculating module 605, the hydrocarbon supply pressure value is transmitted to the PWM calculating module 605, and the PWM calculating module 605 calculates the PWM instruction 610 according to the minimum value and the hydrocarbon supply pressure value.
The DOC outlet maximum allowable hydrocarbon content input of the DOC limit calculation module 900 is provided by the DPF limit calculation module 910. The DPF limit calculation module 910 has two inputs, the maximum allowable DPF outlet hydrocarbon content and DPF hydrocarbon conversion efficiency, while the maximum allowable DPF outletHydrocarbon content CHCFThe following formula can be used for calculation:
Figure BDA0002211339760000211
the hydrocarbon conversion efficiency of the DOC and DPF can also be used to detect sulfur poisoning, the effect of sulfur on precious metal catalysts being mainly metal sulfide formation rendering the catalyst ineffective. The spent catalyst increases the light-off temperature for the hydrocarbons, which may result in a decrease in hydrocarbon conversion and thus a hydrocarbon leak. Sulfur poisoning of the catalyst has a process. Since the DOC is upstream of the DPF, the DOC can develop poisoning symptoms earlier than the DPF, i.e., the DOC has a much lower hydrocarbon conversion efficiency than the DPF. Therefore, by comparing the average efficiencies
Figure BDA0002211339760000221
And
Figure BDA0002211339760000222
can detect sulfur poisoning early to avoid hydrocarbon leakage or other problems.
In the course of detection of sulfur poisoning
Figure BDA0002211339760000223
And
Figure BDA0002211339760000224
after the value of (c), the two values are compared, if any:
，
the Thd _ RS is a threshold value, and triggers a sulfur poisoning fault, and after the sulfur poisoning fault is triggered, the DPF regeneration process needs to be terminated immediately, and a maintenance process is started.
The invention relates to a sulfur poisoning diagnosis method based on a tail gas treatment system, which comprises the following steps:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the third temperature sensor169)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)169) Comparing with a set threshold value Thd _ T169, judging R (T)163) < Thd _ T163? and R (T)169) If not, the operation is ended, if the result is Thd _ T169?;
(3) calculating hydrocarbon energy Ef, wherein Ef is equal to Ef + D multiplied by DF multiplied by LHV multiplied by T, D is the hydrocarbon conveying speed, DF is the degradation factor value, LHV is the low heat value of the hydrocarbon, T is the repetition period, namely the interruption time period, and the energy Ef is calculated once every T seconds;
(4) calculating gas enthalpy change Eg, Eg ═ Egt + (T)169-T163)×CP×Mfe×T，T169Temperature sensing value, T, obtained for the third temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating total average hydrocarbon conversion efficiency of DOC and DPF
(7) Reset Ef and Eg, i.e. Ef and Eg are reset to 0;
(8) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the second temperature sensor167)，
(9) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)167) Comparing with a set threshold value Thd _ T167, and judging R (T)163)＜Thd_T163? and R (T)167) If the result is less than Thd _ T167?, ending the operation;
(10) calculating hydrocarbon energy Ef, wherein Ef is equal to Ef + D multiplied by DF multiplied by LHV multiplied by T, D is the hydrocarbon conveying speed, DF is the degradation factor value, LHV is the low heat value of the hydrocarbon, T is the repetition period, namely the interruption time period, and the energy Ef is calculated once every T seconds;
(11) calculating the change in enthalpy of gas Eg, Eg ═ Eg + (T)167-T163)×CP×Mfe×T，T167Temperature sensing value, T, obtained for the second temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(12) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(13) calculating the average hydrocarbon conversion efficiency of the DOC
Figure BDA0002211339760000232
(14) According to total average hydrocarbon conversion efficiency
Figure BDA0002211339760000233
And average hydrocarbon conversion efficiency of DOC
Figure BDA0002211339760000234
Calculating average Hydrocarbon conversion efficiency of DPF
Figure BDA0002211339760000235
Figure BDA0002211339760000236
(15) Reset Ef and Eg, i.e. Ef and Eg are reset to 0;
(16) average hydrocarbon conversion efficiency of DOC
Figure BDA0002211339760000237
Average hydrocarbon conversion efficiency with DPF
Figure BDA0002211339760000238
Comparing the ratio with a set threshold value Thd _ RS, and judging
Figure BDA0002211339760000239
If not, the operation is finished;
(17) triggering a sulfur poisoning fault prompt and ending the operation.

Claims (5)

1. An exhaust gas treatment system, characterized in that: the catalyst conversion device comprises a tail gas channel, a conical necking, a DOC (catalyst control) and a DPF, wherein the tail gas channel is arranged along the tail gas outlet direction, an external hydrocarbon injection device is connected onto the tail gas channel, a first temperature sensor is arranged at the upstream of the DOC, a first differential pressure sensor used for measuring the upstream pressure of the DOC and the differential pressure passing through the conical necking is arranged at the upstream of the DOC, a second temperature sensor and a third temperature sensor are respectively arranged at the upstream and the downstream of the DPF, and a second differential pressure sensor used for measuring the outlet pressure of the DPF and the differential pressure passing through the DPF is arranged on the DPF; the controller is respectively electrically connected with the internal combustion engine, the first temperature sensor, the second temperature sensor, the third temperature sensor, the first differential pressure sensor and the second differential pressure sensor; the external hydrocarbon injection device comprises a control manifold, a fuel oil electromagnetic valve, a fuel injector, a pressure sensor, a buffer device and a controller, wherein the control manifold is provided with four ports, the ports of the control manifold are communicated with each other to form a hollow chamber, the pressure sensor is used for detecting the pressure of the chamber of the control manifold, the buffer device is used for providing damping for the control manifold, the controller is respectively electrically connected with the fuel oil electromagnetic valve, the fuel injector and the pressure sensor, one port of the control manifold is connected with a hydrocarbon source through the fuel oil electromagnetic valve, one port of the control manifold is connected with the fuel injector, one port of the control manifold is connected with the pressure; the controller controls the fuel oil electromagnetic valve to be electrified and opened, the hydrocarbon source enters the control manifold through the fuel oil electromagnetic valve and then flows to the fuel injector and is injected, the pressure sensor detects the hydrocarbon pressure in the control manifold and feeds the pressure back to the controller, and the controller controls the flow of injected hydrocarbon through controlling the on-off time of the fuel injector.
2. A method for calculating the hydrocarbon conversion efficiency of an exhaust gas treatment system according to claim 1, comprising the steps of:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the second temperature sensor167)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)167) Comparing with a set threshold value Thd _ T167, and judging R (T)163) < Thd _ T163? and R (T)167) If the result is less than Thd _ T167?, ending the operation;
(3) calculating hydrocarbon energy Ef, wherein the Ef is equal to Ef + DxDF xLHV xT, D is the hydrocarbon conveying speed, DF is a degradation factor value, LHV is the low heating value of the hydrocarbon, and T is a repetition period;
(4) calculating the change in enthalpy of gas Eg, Eg ═ Eg + (T)167-T163)×CP×Mfe×T，T167Temperature sensing value, T, obtained for the second temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating the average hydrocarbon conversion efficiency of the DOC
(7) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
3. The method for calculating the hydrocarbon conversion efficiency of the exhaust gas treatment system according to claim 2, comprising the steps of:
(1) calculating the change rate R (T) of the first temperature sensor163) And rate of change R (T) of the third temperature sensor169)，
(2) The rate of change R (T)163) Compares it with a set threshold value Thd _ T163 and compares the rate of change R (T)169) Comparing with a set threshold value Thd _ T169, judging R (T)163) < Thd _ T163? and R (T)169) If not, the operation is ended, if the result is Thd _ T169?;
(3) calculating hydrocarbon energy Ef, wherein the Ef is equal to Ef + DxDF xLHV xT, D is the hydrocarbon conveying speed, DF is a degradation factor value, LHV is the low heating value of the hydrocarbon, and T is a repetition period;
(4) calculating gas enthalpy change Eg, Eg ═ Egt + (T)169-T163)×CP×Mfe×T，T169Temperature sensing value, T, obtained for the third temperature sensor163Temperature sensing value, C, obtained for the first temperature sensorPIs the constant pressure heat capacity of the tail gas, MfeIs the tail gas mass flow;
(5) comparing the hydrocarbon energy Ef with a set threshold value Thd _ EF, and judging whether Ef is larger than Thd _ Ef? or not, and ending the operation;
(6) calculating total average hydrocarbon conversion efficiency of DOC and DPF
(7) According to total average hydrocarbon conversion efficiencyAnd average hydrocarbon conversion efficiency of DOC
Figure FDA0002211339750000024
Calculating average Hydrocarbon conversion efficiency of DPF
Figure FDA0002211339750000025
(8) And resetting Ef and Eg, namely resetting Ef and Eg to be 0, and ending the operation.
4. A failure diagnosis method of a calculation method of hydrocarbon conversion efficiency of an exhaust gas treatment system according to claim 3, characterized by comprising the steps of:
(1) average hydrocarbon conversion efficiency of DOC
Figure FDA0002211339750000026
Average hydrocarbon conversion efficiency with DPF
Figure FDA0002211339750000027
Comparing the ratio with a set threshold value Thd _ RS, and judging
Figure FDA0002211339750000028
If not, the operation is finished;
(2) triggering a sulfur poisoning fault prompt and ending the operation.
5. A method of diagnosing a malfunction of a hydrocarbon injection device of an exhaust gas treatment system according to claim 1, comprising the steps of:
(1) if the fuel electromagnetic valve is not powered off?, if the fuel electromagnetic valve is not powered off (12);
(2) setting a timer TMR1 ═ TMR1+ T, where the value of the timer TMR1 is a detection time from the power-off of the fuel solenoid valve and the power-on of the fuel injector to the current time of the program execution, and T is a repetition period;
(3) calculating the expected hydrocarbon flow Dr by the formula
Figure FDA0002211339750000031
Wherein C isiIs the nozzle bore flow coefficient of the fuel injector, AiIs the minimum cross-sectional area of the nozzle hole, ρ is the density of the hydrocarbon, and P is the current pressure value in the control manifold;
(4) calculating the amount DM of the hydrocarbon flowing out within the detection time by using the expected hydrocarbon flow Dr, wherein DM is DM + Dr multiplied by T;
(5) comparing the TMR1 value of the timer with a set threshold value Thd _ T1, and judging whether TMR1 is greater than Thd _ T1? or not, and ending the operation;
(6) the fuel injector is powered off, and the fuel electromagnetic valve is powered on;
(7) calculating a difference value between the initial pressure value P0 and the current pressure value P, namely a pressure change value in the detection time, wherein delta P is P-P0;
(8) calculating the mass change quantity delta M of the hydrocarbons in the lower chamber,a is the cross-sectional area of the piston surface of the buffer device, and K is the spring constant of the spring;
(9) the degradation factor value DF is calculated,
Figure FDA0002211339750000033
(10) comparing the degradation factor value DF with a set threshold value Thd _ DFL and Thd _ DFH, judging whether DF is more than Thd _ DFH? or DF is less than Thd _ DFL?, and ending the operation if not;
(11) triggering a fault prompt in the hydrocarbon injection device, and ending the operation;
(12) the fuel oil electromagnetic valve is powered off, and the fuel injector is powered on;
(13) a reset timer TMR1 and the amount of hydrocarbon DM, that is, TMR1 and DM are reset to 0;
(14) and assigning the current pressure value P detected by the pressure sensor as P0, namely P0 is equal to P, and ending the operation.
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