CN114720139A - Emission calibration method, device, equipment and medium based on power assembly rack - Google Patents
Emission calibration method, device, equipment and medium based on power assembly rack Download PDFInfo
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Abstract
The invention discloses an emission calibration method, device, equipment and medium based on a power assembly rack, which are applied to the technology of automobile engines, and the method comprises the following steps: on a power assembly rack, adjusting the working condition of an engine to a plurality of steady-state working condition points; collecting first discharge data of the exhaust system at each steady-state working condition point; and respectively taking each steady-state working condition point as a target steady-state working condition point, and calibrating the feedforward parameters and the feedback parameters of the target steady-state working condition points according to the first exhaust data of the exhaust system at the target steady-state working condition points. The invention solves the technical problem of lower emission calibration efficiency.
Description
Technical Field
The invention belongs to the technical field of automobile engines, and particularly relates to an emission calibration method, device, equipment and medium based on a power assembly rack.
Background
Under the influence of energy crisis and environmental problems, the research and development of energy-saving and emission-reducing technologies of engines are more and more important. However, at present, the emission calibration of the engine is developed based on the resources of the whole vehicle, so that the emission calibration efficiency is low, and the emission development test period of the whole vehicle is long.
Disclosure of Invention
In view of the technical problems in the prior art, embodiments of the present invention provide an emission calibration method, apparatus, device and medium based on a powertrain bench.
In a first aspect, an embodiment of the present invention provides an emission calibration method based on a powertrain bench, where the powertrain bench includes an engine and an exhaust system connected to an exhaust side of the engine, and the method includes: on the powertrain bench, adjusting the operating condition of the engine to a plurality of steady state operating points; collecting first discharge data of the exhaust system at each steady-state working condition point; and respectively taking each steady-state working condition point as a target steady-state working condition point, and calibrating a feedforward parameter and a feedback parameter for the target steady-state working condition point according to first exhaust data of the exhaust system at the target steady-state working condition point.
Optionally, the exhaust system includes an exhaust pipe connected to an exhaust side of the engine, on which a front oxygen sensor for detecting an excess air ratio of the engine is mounted, the method further including: taking each steady-state working condition point as a target steady-state working condition point;
determining the number of combustion cycles required by the engine when an actual measured value of an excess air factor reaches a target excess air factor at the target steady-state operating point, wherein the actual measured value of the excess air factor is detected by the front oxygen sensor; and calibrating the detection delay of the front oxygen sensor for detecting the excess air coefficient at the target steady-state working point according to the combustion cycle number.
Optionally, the exhaust system further includes a primary catalyst connected to the exhaust side of the engine through the exhaust pipe, and a post-oxygen sensor connected after the primary catalyst, and the collecting first emission data of the exhaust system at each of the steady-state operating points includes: adjusting the excess air coefficient of combustion in the engine cylinder to be small for multiple times in a preset step length at the target steady-state working point so as to enable the post-oxygen voltage detected by the post-oxygen sensor to be gradually increased in a preset voltage range; first exhaust data of the exhaust system is collected after each turndown of the excess air factor.
Optionally, the calibrating the feed-forward parameter and the feedback parameter for the target steady-state operating point according to the first exhaust data of the exhaust system at the target steady-state operating point includes: detecting a post-oxygen voltage by the post-oxygen sensor after the excess air coefficient is reduced at the target steady-state operating point each time; comparing the first discharge data acquired at each time at the target steady-state working condition point, and determining target discharge data according to a comparison result; when the target emission data is acquired, the excess air coefficient of the engine is calibrated to be a feedforward parameter of the target steady-state working condition point; and when the target emission data is acquired, the post-oxygen voltage detected by the post-oxygen sensor is calibrated as the feedback parameter of the target steady-state working point.
Alternatively, the determining the number of combustion cycles required for the engine when the measured excess air ratio value reaches the target excess air ratio may include: on the power assembly rack, adjusting the oil injection pulse width of the engine to a preset oil injection pulse width, wherein the preset oil injection pulse width corresponds to a target excess air coefficient; starting to count the combustion cycle of the engine at the moment when the oil injection pulse width of the engine reaches the preset oil injection pulse width, and detecting an excess air coefficient through the pre-oxygen sensor; and acquiring the number of combustion cycles of the engine when the measured value of the excess air factor detected by the front oxygen sensor reaches the target excess air factor.
Optionally, the method further comprises: on the power assembly rack, adjusting the working condition of the engine to a plurality of preset ignition working condition points; adjusting VVT angle combination for multiple times at each ignition working condition point, and acquiring combustion fluctuation data of the engine and second emission data of the exhaust system after adjusting the VVT angle combination every time; respectively taking each ignition working condition point as a target ignition working condition point, comparing combustion fluctuation data and second emission data obtained at each time of the target ignition working condition points, and selecting a target VVT angle combination according to a comparison result; and performing VVT air inlet calibration and VVT exhaust calibration on the target ignition working condition point based on the target VVT angle combination.
Optionally, the second emission data of the exhaust system comprises an amount of particulate matter emitted, the method further comprising: on the power assembly rack, adjusting the working condition of the engine to at least one preset transient working condition; at each transient working condition, adjusting at least one control parameter of the engine by adopting a plurality of different parameter adjusting modes respectively, and acquiring the quantity change of particulate matters discharged by the exhaust system under each parameter adjusting mode; respectively taking each transient working condition as a target transient working condition, comparing the quantity change of the particulate matters corresponding to different parameter adjustment modes under the target transient working condition, and determining a target parameter adjustment mode according to a comparison result; and calibrating the target parameter adjusting mode as the parameter adjusting mode of the target transient working condition.
In a second aspect, an embodiment of the present invention provides an emission calibration apparatus based on a powertrain bench, the powertrain bench including an engine and an exhaust system connected to an exhaust side of the engine, the apparatus including: the working condition adjusting unit is used for adjusting the working condition of the engine to a plurality of steady-state working condition points on the power assembly rack; the data acquisition unit is used for acquiring first exhaust data of the exhaust system at each steady-state working condition point; and the first calibration unit is used for respectively taking each steady-state working condition point as a target steady-state working condition point and calibrating the feedforward parameters and the feedback parameters of the target steady-state working condition point according to the first discharge data of the exhaust system at the target steady-state working condition point.
In a third aspect, an embodiment of the present invention provides an emission calibration apparatus based on a powertrain bench, where the powertrain bench includes an engine and an exhaust system connected to an exhaust side of the engine, and the emission calibration apparatus further includes: a processor and a memory coupled to the processor, the memory storing instructions that, when executed by the processor, implement the method of any of the embodiments of the first aspect.
In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the method described in any of the embodiments of the first aspect.
One or more technical solutions provided by the embodiments of the present invention at least achieve the following technical effects or advantages:
adjusting the working condition of the engine to a plurality of steady-state working condition points on the power assembly rack; collecting first discharge data of the exhaust system at each steady-state working condition point; each steady-state working point is respectively used as a target steady-state working point, and a feedforward parameter and a feedback parameter are calibrated for the target steady-state working point according to first exhaust data of an exhaust system at the target steady-state working point, so that the emission result of an I-type test of the whole vehicle can be effectively replaced only depending on an exhaust system carried by a power assembly rack on the premise of not having the resources of the whole vehicle, the emission calibration is completed on the power assembly rack, the calibration efficiency is improved, the resources of the whole vehicle are not limited, the emission development of the whole vehicle can be carried out in advance when only engine resources are available in the development process of the whole vehicle, and the development period of the whole vehicle is shortened.
And compared with the whole vehicle hub rotating resource, the rack resource has the advantages of lower cost, small operation difficulty, low labor cost and less material consumption.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic structural view of an exhaust system according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for emission calibration at steady state operating points based on a powertrain rig in an embodiment of the present disclosure;
FIG. 3 is an emissions calibration flow chart based on a powertrain skid for light-off conditions in an embodiment of the present disclosure;
FIG. 4 is a schematic representation of emission data and combustion fluctuation for different VVT angle combinations under transient conditions;
FIG. 5 is a flowchart of emissions calibration for transient conditions based on a powertrain rig in an embodiment of the present disclosure;
FIG. 6 is a schematic illustration of the rotational speed and cylinder density based on transient operating conditions of the powertrain rig in an embodiment of the present invention;
FIG. 7 is a functional block diagram of a powertrain bench based emission calibration apparatus in the practice of the present invention;
FIG. 8 is a schematic structural diagram of an emission calibration apparatus based on a powertrain cradle according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In a first aspect, embodiments of the present invention provide an emission calibration method based on a powertrain bench, which is used for calibrating emission of an engine based on the powertrain bench without depending on vehicle resources.
Referring to fig. 1, the hardware part of the powertrain mount according to the embodiment of the present invention includes an engine, and an exhaust system connected to an exhaust side of the engine, and the exhaust system includes an exhaust pipe connected to the exhaust side of the engine, and a front oxygen sensor mounted on the exhaust pipe for detecting an excess air ratio of the engine, and a first-stage catalyst or a plurality of stages of catalysts connected in series (for example, a first-stage catalyst and a second-stage catalyst connected in series) is connected to the other end of the exhaust pipe. The 1-stage catalyst is connected with the exhaust side of the engine through an exhaust pipe, and a silencer can be connected behind the last stage catalyst.
The front oxygen sensor is arranged in front of the 1-stage catalyst, and the front oxygen sensor adopts a linear oxygen sensor and is used for monitoring the excess air coefficient of an engine cylinder in real time, wherein the excess air coefficient is the ratio of the air quantity of fuel combustion actually supplied to the engine to the theoretical air quantity, and Lambda (Lambda) represents the excess air coefficient.
The rear oxygen sensor is arranged behind the first-stage catalyst, the rear oxygen sensor adopts a switch oxygen sensor and is used for monitoring the concentration of the mixed gas after passing through the first-stage catalyst in real time, and the voltage measured by the rear oxygen sensor (namely, rear oxygen voltage) represents the concentration of the mixed gas after passing through the first-stage catalyst.
In the specific implementation process, each stage of catalyst can adopt a three-way catalyst which is an important external purifying device in an exhaust system and can be used for purifying CO and HC (HC: (CO and HC)) exhausted from automobile exhaustHydrocarbon compound) And NOx(Nitrogen oxides) redox to harmless CO2Water and nitrogen. The three-way catalyst can simultaneously purify CO, HC and NOxThe λ window for more than 90% of the three contaminants is small and not symmetrical with respect to λ of 1.00, but is biased to the slightly concentrated side. The conversion efficiency of the catalyst can be greatly improved by finely controlling lambda in order to match with the three-way catalyst. Therefore, the calibration of λ is very important.
Based on the embodiment of the invention and the power assembly rack shown in FIG. 1, an emission calibration method based on the power assembly rack can be realized. Referring to FIG. 2, the powertrain bench based emission calibration method includes the steps of:
and S101, on the power assembly rack, adjusting the working condition of the engine to a plurality of steady-state working condition points.
It should be noted that the operating point of the engine is defined by the engine speed and the cylinder density. For example, the engine operating condition is adjusted to a steady state operating point where the engine speed is 1200rpm and the cylinder density is 250 mg/l. In the specific implementation process, each preset steady-state operating point can be sequentially operated from small to large until all steady-state operating points are operated.
S102, collecting first discharge data of the exhaust system at each steady-state working condition point.
Taking each steady-state working condition point as a target steady-state working condition point, and reducing the excess air coefficient of combustion in the engine cylinder for multiple times by a preset step length when the engine runs to the target steady-state working condition point so as to gradually increase the post-oxygen voltage detected by the post-oxygen sensor within a preset voltage range; after each reduction of the excess air ratio, first exhaust data of the exhaust system are collected.
It is understood that the first discharge data of each acquisition includes: CO, HC, NOxThe respective concentrations of these three air pollutants.
When the post-oxygen voltage is in the voltage range of 0.5V-0.8V, the exhaust system discharges CO, HC and NOxThe concentrations of the three air pollutants are low, and thus, the preset voltage range may be set to 0.5V to 0.8V.
The following description will illustrate the first exhaust data collection process of the exhaust system at a certain steady-state operating point (e.g., 1050rpm, 250mg/l cylinder density):
step 1: on a power assembly rack, the fuel injection pulse width of the engine is adjusted, and the post oxygen voltage detected by the post oxygen sensor is monitored in the process of adjusting the fuel injection pulse width until the post oxygen voltage reaches about 0.5V.
Step 2: waiting for the stable working condition after the post-oxygen voltage reaches 0.5V, and collecting and recording CO, HC and NO discharged by the primary exhaust system after the working condition is stable for a preset timexThe concentration of (c).
Then, step 3 is executed: continuously adjusting the oil injection pulse width of the engine, reducing lambda by 0.0005 by adjusting the oil injection pulse width, and collecting and recording CO, HC and NO discharged by the primary exhaust system after the working condition is stable for 5 minutesxThe concentration of (c).
For example, as shown in table 1, when λ is 0.9965, the post-oxygen voltage is 0.51V, which is CO, HC, and NO collected in the first strokexConcentration; the voltage is increased to 0.82V, and CO, HC and NO are collected for the last strokexThe concentration of (c).
Through the steps 1-3, the first discharge data can be collected for multiple times aiming at the same steady-state working condition point.
S103, taking each steady-state working condition point as a target steady-state working condition point, and calibrating a feedforward parameter and a feedback parameter for the target steady-state working condition point according to first exhaust data of the exhaust system at the target steady-state working condition point.
When the engine runs to a target steady-state working point, after the excess air coefficient is reduced by a preset step length each time, the post-oxygen voltage is detected by a post-oxygen sensor; comparing the first discharge data acquired each time under the target steady-state working condition point, and determining the target discharge data according to the comparison result; when the target emission data is acquired, calibrating the excess air coefficient of the engine as a feedforward parameter of a target steady-state working condition point; and when the target emission data is acquired, calibrating the post-oxygen voltage detected by the post-oxygen sensor as the feedback parameter of the target steady-state working condition point.
Specifically, according to the comparison result, one group of emission data with the relatively lowest emission concentration among all the groups of first emission data acquired at the target steady-state operating point may be used as the target emission data.
The following are exemplified as shown in table 1: at a steady state operating point: under the conditions that the engine speed is 1050rpm and the cylinder density is 250mg/l, when lambda is 0.9955, the emission concentration of three pollutants emitted by an exhaust system is relatively lowest comprehensively, and the post-oxygen is stabilized to be near 0.75V, therefore, the lambda is 0.9955 is set as a feed-forward parameter of a steady-state operating point of 1050rpm and 250mg/l of cylinder density, and 0.75V is set as a feedback parameter of the operating point of 1050rpm and 250 mg/l.
TABLE 1.200 rpm, first bleed data and post oxygen voltage for different lambda at 250mg/l operating point
| λ | Back oxygen voltage (V) | CO(ppm) | THC(ppm) | NOx(ppm) |
| 0.9965 | 0.51 | -4.634 | 58.714 | 5.486 |
| 0.996 | 0.54 | -4.703 | 2.611 | -1.961 |
| 0.9955 | 0.75 | -4.686 | 1.385 | -2.315 |
| 0.995 | 0.78 | -4.723 | -0.241 | 0.576 |
| 0.9945 | 0.82 | -4.663 | 231.488 | 32.21 |
For each steady-state operating point, calibration of the feedforward parameter and the feedback parameter can be completed through step S103, which is not described herein again. And after the calibration of the feedforward parameters and the feedback parameters of all steady-state working condition points is finished, filling the calibration tables into corresponding calibration tables. Specifically, if the feedforward parameter is λ and the feedback parameter is the post-oxygen voltage, the corresponding calibration tables of the feedforward parameter and the feedback parameter are shown in the following table 2:
TABLE 2 calibration chart for feedforward parameter and feedback parameter
Because the actual value of lambda burned in the cylinder of the engine has a delay from the actual value of lambda detected by the front oxygen sensor, the delay depends on the pipe line of the exhaust pipe and the position where the front oxygen sensor is installed. Therefore, at each steady state operating point, the detection delay of λ may also be calibrated.
Specifically, calibrating the detection delay of λ includes the following steps S104: taking each steady-state working condition point as a target steady-state working condition point; determining the number of combustion cycles required by the engine when the actual measured value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient at the target steady-state operating point, wherein the actual measured value of the excess air coefficient is detected by the front oxygen sensor; and (4) calibrating the detection delay of the excess air coefficient detected by the oxygen sensor at the target steady-state working point according to the number of the combustion cycles.
It should be noted that there is no sequence between step S104 and the foregoing steps S102 to S103, and the operating condition of the engine may be readjusted to each target steady-state operating condition.
In step S104, at a certain steady-state working point, on the power assembly rack, adjusting the oil injection pulse width of the engine to a preset oil injection pulse width, wherein the preset oil injection pulse width corresponds to the target excess air coefficient, so that the true value of lambda of in-cylinder combustion is equal to the target excess air coefficient; counting the combustion cycle of the engine when the oil injection pulse width of the engine reaches a preset oil injection pulse width, and detecting an excess air coefficient through a front oxygen sensor; and acquiring the number of combustion cycles of the engine when the measured value of the excess air coefficient detected by the front oxygen sensor reaches the target excess air coefficient. The number of combustion cycles that the engine has been subjected to is calibrated as the detection delay.
Specifically, when the engine is currently operating at the target operating point, the actual value of the excess air ratio burned in the engine cylinder can be made equal to the target excess air ratio by adjusting the fuel injection pulsewidth of the engine to a preset fuel injection pulsewidth, but since the front oxygen sensor has a detection delay, the engine needs to go through a certain combustion cycle from the time when the actual value of the excess air ratio burned in the engine cylinder is equal to the target excess air ratio to the time when the actual value of the excess air ratio detected by the front oxygen sensor is equal to the target excess air ratio.
Specifically, the target excess air ratio may be set to 1.1, the actual value of the excess air ratio burned in the engine cylinder is set to 1.1 by adjusting the fuel injection pulsewidth of the engine to a preset fuel injection pulsewidth, and from this point, after the engine has passed a certain number of combustion cycles, the actual value of the excess air ratio detected by the pre-oxygen sensor is set to 1.1, and the number of combustion cycles passed by the engine at this point is recorded.
Taking the steady state operating point of 1200rpm, 250mg/l as an example for adjusting the operating condition of the engine, the process of calibrating the detection delay of λ is exemplified as follows:
step A, on a power assembly rack, adjusting the working condition of an engine to a steady-state working condition point of 1200rpm and 250 mg/l;
b, adjusting the fuel injection pulse width of the engine to enable lambda to be 1.1 when the engine is combusted in a cylinder;
step C, starting from the time when the lambda actual value in the engine cylinder is 1.1, after the engine passes a certain number of combustion cycles, recording the lambda actual value obtained by actually measuring the lambda of the front oxygen sensor to be 1.1, starting from the time when the lambda of the engine cylinder is 1.1, and ending from the time when the lambda of the oxygen sensor is 1.1, wherein the number of combustion cycles of the engine is 30 in the process;
step D: the number of burning cycles recorded 30 was calibrated to be 1200rpm, 250mg/l, which is the steady state operating point detection delay.
Repeating the steps A to D for each steady-state working condition point, completing the detection delay calibration under all steady-state working condition points, and filling the detection delay calibration into corresponding calibration tables. The detection delay calibration table of λ is obtained, and is referred to as the following table 3.
TABLE 3 detection delay calibration table of lambda
After the emission calibration of all steady-state operating points is completed through the above S101 to S104, the obtained feedforward parameter and feedback parameter calibration table and the detection delay calibration table of λ are written into an ECU (Electronic Control Unit), so that the ECU controls the engine to continue emission calibration for the light-off operating condition and the transient operating condition.
Wherein, to the emission calibration of the working condition of igniting, specifically do: the method comprises a process of calibrating an intake VVT angle and an exhaust VVT angle of a VVT (variable valve timing) under different ignition working conditions based on a power assembly rack. Referring to fig. 3, the process of calibrating the intake VVT angle and the exhaust VVT angle of the engine under different ignition conditions includes the following steps S301 to S304:
s301, on the power assembly rack, adjusting the working condition of the engine to a plurality of preset ignition working condition points.
For example, a predetermined light-off condition point is defined as: the ignition rotating speed of the engine is 1200rpm, the air density of the air cylinder is 250gm/l, the ignition efficiency is set to be 0.6, and the water temperature of the engine is controlled to be 30 ℃ according to a circulating water system of the power assembly rack so as to better simulate the cold state of the whole vehicle.
And S302, adjusting the VVT angle combination of the engine for multiple times at each ignition working condition point, and acquiring combustion fluctuation data of the engine and second emission data of the exhaust system after adjusting the VVT angle combination every time.
Wherein, each VVT angle combination comprises: an angle of intake vvt (ivvt) and an angle of exhaust vvt (evvt). The combustion fluctuation data can be expressed by the amount of combustion fluctuation (COV), the size of the result can visually reflect the stability of the performance in the circulation process, and the second emission data comprises THC, CO and NOxThe concentrations of these three gas emissions and the amount of particulate matter (PN).
Specifically, the engine may be adjusted for the iVVT angle and the EVVT angle with reference to the respective VVT angle combinations shown in table 4. As shown in table 4 below, a unique number is set for each VVT angle combination, and the unique number is used for each VVT angle combination identified in one-to-one correspondence.
TABLE 4 VVT Angle combination correspondence numbering table
Referring to fig. 4, the emission data of the emission system and the combustion fluctuation amount of the engine under the 49 VVT angle combinations in table 4 are respectively collected, and the obtained emission data and combustion fluctuation amount are shown, where the unique number corresponding to each intake and exhaust combination in table 4 is the horizontal axis in fig. 4, and the vertical axis in fig. 4 is the corresponding gas pollutant emission concentration or combustion fluctuation amount.
For example, the VVT angle combination adjusted at a certain ignition operating point is: the angle of the intake VVT (iVVT) is 23 degrees, the angle of the exhaust VVT (EVVT) is-10 degrees, and after the preset time length of the VVT angle combination is adjusted (for example, after 5 minutes), the combustion fluctuation quantity of the engine and the THC, CO and NO are collected and recordedxConcentration of these three gas emissions, particulate matter number (PN).
And S303, respectively taking each ignition working condition point as a target ignition working condition point, comparing the combustion fluctuation data and the second emission data acquired at each time of the target ignition working condition point, and selecting a target VVT angle combination according to the comparison result.
Specifically, as the intake VVT increases, there is some deterioration in the THC concentration, CO concentration, and particulate matter amount, and NOxThe concentration is optimized to a certain extent; if the intake VVT is fixed, if the opening angle of the exhaust VVT is too large, the THC concentration, the CO concentration, and the amount of particulate matter also deteriorate, and at the same time, too large overlap angle of intake and exhaust causes large COV and unstable engine speed. Based on the balance consideration of the gas emissions and the rotation speed fluctuation, a plurality of candidate VVT angle combinations can be selected according to the comparison result, thereby narrowing the VVT angle combination range. Referring to fig. 4, the angle of the intake VVT ranges from 0 to 5 °, and the angle of the exhaust VVT ranges from 0 to 10 °, so that both the gas emissions and the combustion fluctuation amount can be considered (CoV lower than 50 can satisfy the requirement). And the amount of particulate matter is also optimized within this VVT angle range, the same VVT zone range may be selected.
Since the most appropriate VVT angle combination cannot be determined by the above-described steady-state operating condition sweep point method. Therefore, a circulation dynamic working condition sweeping point of the VVT angle combination is required to be performed on the power assembly rack based on a P1 stage of a WLTC (world Light-duty Test Cycle), the change of the amount of the discharged particulate matters is monitored in the sweeping point process of the circulation dynamic working condition, and a group of VVT angle combinations with optimal particulate matter discharge is obtained from each candidate VVT angle combination as a target VVT angle combination according to the change of the amount of the particulate matters. For example, to achieve both emissions and CoV, an intake VVT angle of 0 ° and an exhaust VVT angle of 3 ° may be selected.
And S304, carrying out VVT air inlet calibration and VVT exhaust calibration on the target ignition working condition point based on the target VVT angle combination.
And combining the selected target VVT angles to serve as the VVT control parameter of the target ignition working condition point. By definition, a decrease in the intake VVT angle, characterized by an increase in the physical angle; an increase in the exhaust VVT angle is characterized by an increase in the physical angle.
Through the process, the water temperature of the engine is controlled to be in a cold state based on the power assembly rack, the VVT angle range is selected according to the emission and the combustion stability of the engine, the dynamic working condition is adopted, and the optimal VVT combination is selected according to the emission of particulate matters.
The VVT angle combinations for other light-off operating points can be calibrated in the same manner (the water temperature and ignition efficiency of the engine are unchanged), as shown in table 5 below:
table 5.
Because the load change of the transient working condition is large, the air-fuel ratio fluctuates, the combustion is deteriorated, and the particulate matter emission is correspondingly higher at the moment. Therefore, the embodiment of the invention designs the transient working condition on the power assembly rack aiming at the WLTC transient working condition, and utilizes the repeated scanning point optimization of the rack to obtain a better control parameter combination aiming at the transient working condition.
Wherein the second emission data of the exhaust system comprises a particulate matter amount, and referring to fig. 5, the emission calibration for the transient operating condition comprises the steps of:
s401, on the power assembly rack, adjusting the working condition of the engine to at least one preset transient working condition. The preset transient operating conditions in the embodiment of the invention are all operating conditions with relatively high amount of discharged particulate matters.
For example, transient operating conditions are written directly on the powertrain skid for calibration optimization based on regions where WLTC transient operating conditions (P4 phase of WLTC) have high particulate matter emissions. As shown in fig. 6, the programmed transient operating conditions may be: the speed was increased from 1930rpm to 2300rpm for 3s and the cylinder density was increased from 1090mg/l to 2075mg/l for 3 s.
S402, under each transient working condition, at least one control parameter of the engine is adjusted by adopting a plurality of different parameter adjusting modes respectively, and the change of the quantity of the particulate matters discharged by the exhaust system under each parameter adjusting mode is obtained.
Specifically, the control parameters of the engine include injection angle, injection times, rail pressure, and transient fuel control. The parameter adjustment method may have the following four ways:
mode 1, adjusting only the number of injections of the engine: the injection ratio is adjusted to 2:1:1 from 2 to 3, and the improvement effect on the particulate matter emission is limited.
And 2, synchronously adjusting the injection times and the injection angle of the engine, adjusting the injection times from 2 to 3, and adjusting the oil injection ratio to 2:1: 1. The SOI (start of injection) angle is 270 and the EOI (end of injection) angle is 40 near compression top dead center to ensure that the fuel ignites just near delivery to the spark plug and particulate matter emissions trend downward.
Mode 4, on the basis of the injection frequency and the injection angle of the synchronous adjustment engine, the rail pressure is increased to 35Mpa, transient fuel oil is adjusted, and the quantity of particles is increased.
And S403, respectively taking each transient working condition as a target transient working condition, comparing the quantity change of the particulate matters corresponding to different parameter adjustment modes under the target transient working condition, and determining the target parameter adjustment mode according to the comparison result.
And S404, calibrating the target parameter adjusting mode as a parameter adjusting mode of the target transient working condition.
Specifically, the change of the number of the particulate matter under the four parameter adjustment modes is compared, and the minimum number of the particulate matter corresponding to the third parameter adjustment mode is determined, so that the third parameter adjustment mode can be determined as the target parameter adjustment mode and is calibrated as the parameter adjustment mode of the target transient working condition.
The ignition working condition and the transient working condition are areas where the emission of the whole vehicle is difficult to optimize, the emission accounts for more than 90% of the whole WLTC cycle, and the emission calibration efficiency can be improved by relying on the high repeatability of a power assembly rack.
Based on the foregoing emissions calibration procedures, and inputting these calibrations into the ECU software, WLTC cycle tests are performed on the powertrain bench. As can be seen from Table 6, the emission results of the bench test of the powertrain are far lower than the requirements of the national six-regulation, and the emission results meet the requirements.
Table 6.
After the emission calibration is carried out on the basis of the power assembly rack each time, the cooling water of the power assembly rack is adopted to rapidly cool the engine, so that the test times in one day are greatly improved and are far higher than the limit of one-time test of the rotating hub of the whole vehicle in one day.
The catalyst converter model selection based on the power assembly rack is experimental, and the control strategy of experimental boundary condition, engine is all more stable for the uniformity that the catalyst converter model selection was experimental to be discharged is higher, and simultaneously, the engine is experimental at the rack after, and the steerable cooling water system of rack cools off the engine fast, shortens the time that gets into next test, thereby has promoted the experimental efficiency of catalyst converter model selection greatly.
The method for calibrating the emission of the power assembly rack is established, the development of the emission of the rack is guided, evaluation indexes are established, and the working efficiency of the emission forward moving rack is improved.
Based on the same inventive concept, the invention relates to an emission calibration device based on a power assembly bench, which is shown in a reference figure 1, wherein the power assembly bench comprises an engine and an exhaust system connected with the exhaust side of the engine, and is shown in a reference figure 7, and the emission calibration device comprises:
a working condition adjusting unit 701, configured to adjust a working condition of the engine to multiple steady-state working condition points on the powertrain rack;
a data acquisition unit 702, configured to acquire first emission data of the exhaust system at each of the steady-state operating points;
the first calibration unit 703 is configured to take each steady-state operating point as a target steady-state operating point, and calibrate a feed-forward parameter and a feedback parameter for the target steady-state operating point according to first discharge data of the exhaust system at the target steady-state operating point.
In some embodiments, the exhaust system includes an exhaust pipe connected to an exhaust side of the engine, and a front oxygen sensor mounted on the exhaust pipe for detecting an excess air ratio of the engine, and the emission calibration apparatus further includes: a second calibration unit 704 for: taking each steady-state working condition point as a target steady-state working condition point; determining the number of combustion cycles required by the engine when an actual measured value of an excess air factor reaches a target excess air factor at the target steady-state operating point, wherein the actual measured value of the excess air factor is detected by the front oxygen sensor; and calibrating the detection delay of the front oxygen sensor for detecting the excess air coefficient at the target steady-state working point according to the combustion cycle number.
In some embodiments, the exhaust system further comprises a primary catalyst connected to the exhaust side of the engine via the exhaust pipe, and a post-oxygen sensor connected after the primary catalyst, the data acquisition unit 702 being configured to: adjusting the excess air coefficient of combustion in the engine cylinder to be small for multiple times in a preset step length at the target steady-state working point so as to enable the post-oxygen voltage detected by the post-oxygen sensor to be gradually increased in a preset voltage range; first exhaust data of the exhaust system is collected after each turndown of the excess air factor.
In some embodiments, the first calibration unit 703 is specifically configured to: detecting a post-oxygen voltage by the post-oxygen sensor after the excess air coefficient is reduced at the target steady-state operating point each time; comparing the first discharge data acquired at each time at the target steady-state working condition point, and determining target discharge data according to the comparison result; when the target emission data is acquired, the excess air coefficient of the engine is calibrated to be a feedforward parameter of the target steady-state working point; and when the target emission data is acquired, the post-oxygen voltage detected by the post-oxygen sensor is calibrated as the feedback parameter of the target steady-state working point.
In some embodiments, the second calibration unit 704 is specifically configured to: on the power assembly rack, adjusting the oil injection pulse width of the engine to a preset oil injection pulse width, wherein the preset oil injection pulse width corresponds to a target excess air coefficient; starting to count the combustion cycle of the engine at the moment when the oil injection pulse width of the engine reaches the preset oil injection pulse width, and detecting an excess air coefficient through the pre-oxygen sensor; and acquiring the number of combustion cycles of the engine when the measured value of the excess air factor detected by the front oxygen sensor reaches the target excess air factor.
In some embodiments, the apparatus further comprises a third calibration unit configured to: on the power assembly rack, adjusting the working condition of the engine to a plurality of preset ignition working condition points; adjusting the VVT angle combination for multiple times at each ignition starting working condition point, and acquiring combustion fluctuation data of the engine and second emission data of the exhaust system after adjusting the VVT angle combination every time; respectively taking each ignition working condition point as a target ignition working condition point, comparing combustion fluctuation data and second emission data obtained at each time of the target ignition working condition points, and selecting a target VVT angle combination according to a comparison result; and performing VVT air inlet calibration and VVT exhaust calibration on the target ignition working condition point based on the target VVT angle combination.
In some embodiments, the second emission data of the exhaust system comprises an amount of particulate matter emitted, and further comprising a fourth calibration unit for: on the power assembly rack, adjusting the working condition of the engine to at least one preset transient working condition; at each transient working condition, adjusting at least one control parameter of the engine by adopting a plurality of different parameter adjustment modes respectively, and acquiring the change of the quantity of particulate matters discharged by the exhaust system under each parameter adjustment mode; respectively taking each transient working condition as a target transient working condition, comparing the quantity change of the particulate matters corresponding to different parameter adjustment modes under the target transient working condition, and determining a target parameter adjustment mode according to a comparison result; and calibrating the target parameter adjusting mode as the parameter adjusting mode of the target transient working condition.
Based on the same inventive concept, an embodiment of the present invention provides an emission calibration apparatus based on a powertrain mount, as shown in fig. 1, where the powertrain mount includes an engine and an exhaust system connected to an exhaust side of the engine, and as shown in fig. 8, the emission calibration apparatus further includes: a processor 802 and a memory 804, wherein the memory 804 is coupled to the processor 802, and a computer program stored in the memory 804 and capable of running on the processor 802 is executed by the processor 802 to implement the emission calibration method based on the powertrain bench described in any of the above method embodiments, and for brevity of the description, the description is omitted here.
Wherein in fig. 8 a bus architecture (represented by bus 800), bus 800 may include any number of interconnected buses and bridges, bus 800 linking together various circuits including one or more processors, represented by processor 802, and memory, represented by memory 304. The bus 800 may also link together various other circuits such as peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore, will not be described any further herein. A bus interface 805 provides an interface between the bus 800 and the receiver 801 and transmitter 803. The receiver 801 and the transmitter 803 may be the same element, i.e., a transceiver, providing a means for communicating with various other apparatus over a transmission medium. The processor 802 is responsible for managing the bus 800 and general processing, and the memory 804 may be used for storing data used by the processor 802 in performing operations.
Based on the same inventive concept, embodiments of the present invention provide a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, implements the powertrain skid based emission calibration method described in any of the method embodiments above.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A method for emission calibration based on a powertrain skid, the powertrain skid comprising an engine and an exhaust system coupled to an exhaust side of the engine, the method comprising:
on the powertrain bench, adjusting the operating condition of the engine to a plurality of steady state operating points;
collecting first emission data of the exhaust system at each steady-state working condition point;
and respectively taking each steady-state working condition point as a target steady-state working condition point, and calibrating a feedforward parameter and a feedback parameter for the target steady-state working condition point according to first exhaust data of the exhaust system at the target steady-state working condition point.
2. The method of claim 1, wherein the exhaust system includes an exhaust pipe connected to an exhaust side of the engine, a front oxygen sensor mounted on the exhaust pipe for detecting an excess air ratio of the engine, the method further comprising:
taking each steady-state working condition point as a target steady-state working condition point;
determining the number of combustion cycles required by the engine when an actual measured value of an excess air factor reaches a target excess air factor at the target steady-state operating point, wherein the actual measured value of the excess air factor is detected by the front oxygen sensor;
and calibrating the detection delay of the front oxygen sensor for detecting the excess air coefficient at the target steady-state working point according to the combustion cycle number.
3. The method of claim 2, wherein the exhaust system further comprises a primary catalyst connected to the exhaust side of the engine through the exhaust pipe, and a post-oxygen sensor connected after the primary catalyst, and wherein collecting first exhaust data of the exhaust system at each of the steady-state operating points comprises:
adjusting the excess air coefficient of combustion in the engine cylinder to be small for multiple times in a preset step length at the target steady-state working point so as to enable the post-oxygen voltage detected by the post-oxygen sensor to be gradually increased in a preset voltage range;
first exhaust data of the exhaust system is collected after each turn down of the excess air factor.
4. The method of claim 3, wherein the calibrating the feed-forward parameter and the feedback parameter for the target steady-state operating point based on the first exhaust data of the exhaust system at the target steady-state operating point comprises:
detecting a post-oxygen voltage by the post-oxygen sensor after the excess air coefficient is reduced at the target steady-state operating point each time;
comparing the first discharge data acquired at each time at the target steady-state working condition point, and determining target discharge data according to the comparison result;
when the target emission data is acquired, the excess air coefficient of the engine is calibrated to be a feedforward parameter of the target steady-state working point;
and when the target emission data is acquired, the post-oxygen voltage detected by the post-oxygen sensor is calibrated as the feedback parameter of the target steady-state working point.
5. The method of claim 2, wherein determining the number of combustion cycles required for the engine when the measured excess air ratio reaches the target excess air ratio comprises:
on the power assembly rack, adjusting the oil injection pulse width of the engine to a preset oil injection pulse width, wherein the preset oil injection pulse width corresponds to a target excess air coefficient;
starting to count the combustion cycle of the engine at the moment when the oil injection pulse width of the engine reaches the preset oil injection pulse width, and detecting an excess air coefficient through the pre-oxygen sensor;
and acquiring the number of combustion cycles of the engine when the measured value of the excess air factor detected by the front oxygen sensor reaches the target excess air factor.
6. The method of claim 1, further comprising:
on the power assembly rack, adjusting the working condition of the engine to a plurality of preset ignition working condition points;
adjusting the VVT angle combination for multiple times at each ignition starting working condition point, and acquiring combustion fluctuation data of the engine and second emission data of the exhaust system after adjusting the VVT angle combination every time;
respectively taking each ignition working condition point as a target ignition working condition point, comparing combustion fluctuation data and second emission data obtained at each time of the target ignition working condition points, and selecting a target VVT angle combination according to a comparison result;
and performing VVT air inlet calibration and VVT exhaust calibration on the target ignition working condition point based on the target VVT angle combination.
7. The method of claim 1, wherein the second emission data of the exhaust system comprises an amount of particulate matter emitted, the method further comprising:
on the power assembly rack, adjusting the working condition of the engine to at least one preset transient working condition;
at each transient working condition, adjusting at least one control parameter of the engine by adopting a plurality of different parameter adjusting modes respectively, and acquiring the quantity change of particulate matters discharged by the exhaust system under each parameter adjusting mode;
respectively taking each transient working condition as a target transient working condition, comparing the quantity change of the particulate matters corresponding to different parameter adjustment modes under the target transient working condition, and determining a target parameter adjustment mode according to a comparison result;
and calibrating the target parameter adjusting mode as the parameter adjusting mode of the target transient working condition.
8. An emissions calibration device based on a powertrain skid, the powertrain skid including an engine and an exhaust system coupled to an exhaust side of the engine, the device comprising:
the working condition adjusting unit is used for adjusting the working condition of the engine to a plurality of steady-state working condition points on the power assembly rack;
the data acquisition unit is used for acquiring first exhaust data of the exhaust system at each steady-state working condition point;
and the first calibration unit is used for respectively taking each steady-state working condition point as a target steady-state working condition point and calibrating the feedforward parameters and the feedback parameters of the target steady-state working condition point according to the first discharge data of the exhaust system at the target steady-state working condition point.
9. An emission calibration apparatus based on a powertrain skid, the powertrain skid comprising an engine and an exhaust system coupled to an exhaust side of the engine, the emission calibration apparatus further comprising: a processor and a memory coupled to the processor, the memory storing instructions that when executed by the processor implement the method of any of claims 1-7.
10. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the method of any one of claims 1 to 7.
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| CN115628143B (en) * | 2022-09-07 | 2024-05-03 | 重庆金康赛力斯新能源汽车设计院有限公司 | Automobile emission control method, device, computer equipment and storage medium |
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