CN111980787B

CN111980787B - Engine exhaust heat management method and system

Info

Publication number: CN111980787B
Application number: CN201910440189.9A
Authority: CN
Inventors: 杜鑫; 胡佳富; 贾长亮
Original assignee: Beijing Foton Cummins Engine Co Ltd
Current assignee: Beijing Foton Cummins Engine Co Ltd
Priority date: 2019-05-24
Filing date: 2019-05-24
Publication date: 2021-11-19
Anticipated expiration: 2039-05-24
Also published as: CN111980787A

Abstract

The invention provides an engine exhaust heat management method, which comprises the following steps: under the working state of an engine, acquiring the exhaust temperature requirement value of an engine exhaust pipeline of the selective catalytic reduction reaction in real time; acquiring an actual exhaust temperature value of an engine exhaust pipeline in the selective catalytic reduction reaction process in real time; calculating a heating demand current value of an engine exhaust pipeline according to the difference value of the exhaust temperature demand value and the actual exhaust temperature value; and controlling a heating unit of the vehicle to heat the exhaust gas of the engine exhaust pipeline according to the heating demand current value. When the exhaust of the engine does not reach the target temperature of SCR catalysis, the heat control unit controls the heating unit to heat the exhaust in the exhaust pipeline, so that the temperature of the exhaust is improved, and the efficiency of SCR catalysis is ensured.

Description

Engine exhaust heat management method and system

Technical Field

The invention relates to the field of engine exhaust control, in particular to an engine exhaust heat management method of an engine exhaust aftertreatment system and an engine exhaust heat management system.

Background

With the development of social economy, the national attention On environmental protection is higher and higher, the national five-national standard of vehicle diesel oil is abandoned, the new national six-standard is implemented, and the new national six-emission regulation can strengthen the real-time monitoring of the vehicle exhaust exceeding standards by OBD (On-Board Diagnostics) while clearly defining the vehicle-mounted law, so as to ensure that the emission of an engine can be controlled in a full range.

TABLE 1

Table 1 is a comparison table of the fifth and sixth national standards, and it is clear from Table 1 that the sixth national standard has an increased weight for N₂O and NO_XAnd (4) pollutant emission requirements. Currently, SCR (Selective Catalytic Reduction)Catalytic reduction) technology for realizing the emission of tail gas N of a diesel engine₂O and NO_XThe main technical scheme of treatment is that the basic working principle of the SCR system is that urea aqueous solution is sprayed into an engine exhaust pipeline through a nozzle, and N in diesel engine exhaust is treated in an SCR catalyst₂O and NO_XDecomposing to generate N₂And H₂And O. However, because the SCR Catalyst has different activities at different temperatures, and when the temperature of the exhaust gas is too low, the catalytic conversion efficiency is greatly affected, at present, DOC (oxidative Catalyst) is mostly used in a scheme for dealing with a low-temperature working condition, so that NO and NO in the exhaust gas₂Is changed, i.e. NO is increased₂To achieve an improvement in reaction efficiency at low temperatures. The adaptability of the DOC scheme to different working condition points cannot be balanced, and NO is generated by oxidation₂The uncertainty of the total amount of (a) may result in that the NOx conversion efficiency cannot be accurately controlled at low temperatures. Some existing Engine products adopt a TMS (Engine Thermal management System) to ensure the exhaust temperature under a certain working condition, but the main function of the Engine is to ensure that the working temperature of the Engine is constant to achieve the optimal working efficiency, the Engine is not directed at the pollutant treatment of exhaust, and the exhaust temperature under the full working condition and the cold working condition of the Engine can not be ensured to achieve the national six standards.

Disclosure of Invention

In view of the problems in the prior art, an object of the present invention is to provide a solution for managing exhaust heat of an engine, so as to achieve the purposes of accurately controlling the temperature of the exhaust of the engine and ensuring the efficiency of SCR catalysis.

In order to achieve the above object, the present invention discloses the following steps:

an engine exhaust heat management method, comprising the steps of:

s1: under the working state of an engine, acquiring the exhaust temperature requirement value of an engine exhaust pipeline of the selective catalytic reduction reaction in real time;

s2: acquiring an actual exhaust temperature value of an engine exhaust pipeline in the selective catalytic reduction reaction process in real time;

s3: calculating a heating demand current value of an engine exhaust pipeline according to the difference value of the exhaust temperature demand value and the actual exhaust temperature value;

s4: and controlling a heating unit of the vehicle to heat the exhaust gas of the engine exhaust pipeline according to the heating demand current value.

Further, in step S1, the obtaining the exhaust temperature requirement of the engine exhaust pipe for the selective catalytic reduction reaction in real time includes:

the method comprises the steps of obtaining a current engine working condition parameter value sent by an ECU (electronic control unit) of a vehicle in real time, and obtaining an exhaust temperature demand value of an engine exhaust pipeline corresponding to the current engine working condition parameter value through a pre-stored mapping table of the engine working condition parameter and the exhaust temperature demand.

Further, in step S2, the obtaining an actual exhaust temperature value of an engine exhaust pipe in the course of the selective catalytic reduction reaction in real time includes:

s201: acquiring temperature information in an engine exhaust pipeline in real time;

s202: and estimating the actual exhaust temperature value of the engine exhaust pipeline in the selective catalytic reduction reaction process according to the acquired temperature information.

Further, in step S3, the calculating a heating demand current value of an engine exhaust pipe according to the difference between the exhaust temperature demand value and the actual exhaust temperature value includes:

calculating a heating demand current value of an engine exhaust pipeline through a PID logic unit arranged in a heating unit of a vehicle according to the difference value between the exhaust temperature demand value and the actual exhaust temperature value;

step S3 further includes:

and supplementing a first correction factor in the calculation of the PID logic unit, and performing correction compensation on the heating demand current value.

Further, in step S4, controlling a heating unit of the vehicle to heat exhaust gas of an engine exhaust pipe according to the heating demand current value includes:

s401: acquiring an actual current output value of a heating unit of a vehicle;

s402: calculating a difference value between the heating demand current value and the actual current output value, and calculating a PWM duty ratio for controlling current through a PID logic unit arranged in a heating unit of the vehicle;

s403: controlling a heating unit of the vehicle to heat exhaust gas of an engine exhaust conduit based on the PWM duty cycle.

Further, step S402 further includes:

and supplementing a second correction factor in the calculation of the PID logic unit, and performing correction compensation on the PWM duty ratio.

Further, the heat management method further comprises a heat recovery step:

the heat of the exhaust pipeline of the engine is recovered through a heat recovery unit of the vehicle, and the recovered heat is converted into electric energy to be stored in a storage battery of the vehicle, wherein the storage battery supplies power to a heating unit of the vehicle.

In another aspect, the present invention further discloses an engine exhaust heat management system, including a particle trap and a selective catalytic reduction unit, the particle trap is disposed in an engine exhaust conduit, the particle trap is configured to trap particulate pollutants, the selective catalytic reduction unit is configured to treat nitrogen oxide pollutants, and the heat management apparatus further includes:

the sensor module is arranged in the engine exhaust pipeline and used for acquiring temperature information in the engine exhaust pipeline in real time and transmitting the temperature information to the thermal control unit of the vehicle;

the thermal control unit is configured to:

acquiring a current engine working condition parameter value sent by an ECU (electronic control unit) of a vehicle in real time, and acquiring an exhaust temperature requirement value of an engine exhaust pipeline corresponding to the current engine working condition parameter value through a pre-stored mapping table of the engine working condition parameter and the exhaust temperature requirement;

estimating an actual exhaust temperature value of an engine exhaust pipeline in the selective catalytic reduction reaction process according to the temperature information from the sensor module;

calculating a heating demand current value of an engine exhaust pipeline according to the difference value of the exhaust temperature demand value and the actual exhaust temperature value, and controlling a heating unit of a vehicle to heat exhaust of the engine exhaust pipeline according to the heating demand current value;

the heating unit is used for heating the exhaust gas of the engine exhaust pipeline under the control of the thermal control unit.

Further, the thermal control unit obtains a current engine working condition parameter value sent by an ECU unit of the vehicle in real time through a CAN bus of the vehicle, and obtains an exhaust temperature demand value of an engine exhaust pipeline corresponding to the current engine working condition parameter value through a pre-stored mapping table of the engine working condition parameter and the exhaust temperature demand.

Further, the thermal control unit acquires temperature information in the engine exhaust pipeline collected by the sensor module in real time, and estimates an actual exhaust temperature value of the engine exhaust pipeline in the selective catalytic reduction reaction process according to the temperature information.

Further, a PID logic unit is arranged in the thermal control unit and used for calculating a heating demand current value of an engine exhaust pipeline according to the difference value of the exhaust temperature demand value and the actual exhaust temperature value;

wherein a first correction factor is added to the calculation of the PID logic unit to correct and compensate the heating demand current value.

Further, the thermal control unit is configured to obtain an actual current output value of the heating unit of the vehicle, calculate a difference between the heating demand current value and the actual current output value, calculate a PWM duty ratio for controlling current through a PID logic unit provided in the heating unit of the vehicle, and control the heating unit of the vehicle to heat exhaust gas in an engine exhaust pipe based on the PWM duty ratio.

Furthermore, a second correction factor is added in the calculation of the PID logic unit, and the PWM duty ratio is corrected and compensated

Further, the engine exhaust heat management system further includes:

the heat recovery unit is used for recovering heat of the engine exhaust pipeline and converting the recovered heat into electric energy;

and the storage battery is used for storing the electric energy converted by the heat recovery unit and supplying power to the heating unit.

Further, the sensor module includes: a temperature sensor unit and a NOx sensor unit in respective communicative connection with the ECU unit.

Further, the engine exhaust conduit of the vehicle is also provided with a diesel oxidation catalyst unit for treating the exhaust gas adjacent to the particle trap and an ammonia slip catalyst unit adjacent to the selective catalytic reduction unit.

The technical scheme can at least obtain the following beneficial effects:

by adopting the engine exhaust heat management method provided by the invention, when the exhaust of the engine does not reach the target temperature of SCR catalysis, the heat control unit controls the heating unit to heat the exhaust in the exhaust pipeline based on the difference value between the exhaust temperature demand value and the actual exhaust temperature value of the SCR catalytic reaction, so that the exhaust temperature is improved, and the SCR catalysis efficiency is ensured. The temperature of the exhaust gas may also be controlled for regeneration of the DPF.

Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:

FIG. 1 is a flow chart of an engine exhaust heat management method of an embodiment of the present invention;

FIG. 2 is a logical block diagram of engine exhaust thermal management according to an embodiment of the present invention;

FIG. 3 is a block diagram of an engine exhaust thermal management system according to an embodiment of the present invention;

FIG. 4 is a block diagram of an engine exhaust conduit according to an embodiment of the present invention;

fig. 5 is a radial sectional structural view of an engine exhaust pipe according to an embodiment of the present invention.

Description of the reference numerals

1-turbocharger 2-exhaust throttle valve

3-exhaust pipe

401-Engine outlet NOx sensor

402-DOC inlet temperature sensor

403-DPF inlet temperature sensor

404-DPF outlet temperature sensor

405-SCR inlet temperature sensor

406-SCR outlet temperature sensor

407-exhaust outlet nitrogen oxide sensor

5-DOC unit 6-DPF unit

701-Urea nozzle 702-SCR unit

8-ASC unit 9-heating wire

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.

As shown in fig. 1, an embodiment of the present invention provides an engine exhaust heat management method, including a method of heating exhaust gas, to ensure that selective catalytic reduction can be performed at an optimum temperature for maximum efficiency, which includes the following steps:

step S1: acquiring an exhaust temperature requirement value of SCR catalytic reaction (selective catalytic reduction reaction), wherein the exhaust temperature requirement value is a variable parameter which is greatly influenced by the working condition of an engine, and under the condition that a vehicle runs at different speeds, the total pollutant amount of the exhaust gas of the engine is different, so that the detection of the working condition of the engine is required to be maintained, and the exhaust gas is required to be updated in real timeThe temperature requirement value can finally meet the national six standards for NO_xRegulation of pollutant emissions.

As an alternative embodiment, the key to obtaining the exhaust temperature requirement is to calculate or derive the exhaust temperature requirement based on the current engine operating conditions, specifically, the thermal control unit of the vehicle obtains the engine operating condition parameter value sent by the ECU unit of the vehicle, and refers to a pre-stored mapping table of the engine operating condition parameter and the exhaust temperature requirement (engine operating condition MAP table) to obtain the exhaust temperature requirement corresponding to the engine operating condition parameter value, although the reference may be done by the ECU unit and the result is directly transmitted to the thermal control unit through the CAN bus. The ECU Unit is an important Control device in the vehicle and mainly comprises a Microprocessor (MCU), a memory (ROM, RAM), an input/output interface (I/O), an analog-to-digital converter (A/D), a shaping, a driving and other large-scale integrated circuits, CAN acquire parameter information of each part of the vehicle through a CAN bus and issue Control instructions, and meanwhile, has strong data processing capacity. The engine working condition MAP table is an electronic table obtained through experiments according to individual types of vehicles, and covers corresponding relations of all partial parameters of the vehicles, wherein the corresponding relations comprise corresponding relations of engine working condition parameter values and exhaust temperature required values, and the corresponding values are searched for through acquired information according to keys.

In the above alternative embodiment, the engine operating condition parameter value may be a rotation speed value and an engine indicated torque value, and the exhaust temperature demand value is obtained by processing data with reference to the engine operating condition MAP table after the rotation speed value and the engine indicated torque value transmitted by the ECU unit are received by the thermal control unit through the CAN bus.

Step S2: there are several specific methods for estimating the actual exhaust temperature during the SCR catalytic reaction, which are described below:

(1) a temperature sensor is provided directly at the SCR catalytic unit (or SCR unit),the temperature sensor uploads temperature information to the ECU unit through the CAN bus or directly to the thermal control unit when the engine exhausts. The mode has simple structure and can directly obtain the actual exhaust temperature value. However, the environment is complex during the internal catalytic reaction of the SCR catalytic unit, the accuracy of the measurement of the temperature sensor can be affected, the engine exhaust enters the SCR catalytic unit when the temperature is detected, and if the temperature does not reach the standard, the heating unit cannot heat the engine exhaust, so that NO is caused inevitably_XThe catalytic reaction is incomplete and cannot reach the national emission standard; in addition, a temperature sensor is added to the existing packaged SCR catalytic unit, and the refitting process is troublesome.

(2) The method comprises the steps of arranging a temperature sensor in an exhaust pipeline to detect temperature information of tail gas in the pipeline, estimating an actual exhaust temperature value in the SCR catalytic reaction process according to the temperature information, for example, according to a mapping relation between relevant engine parameters and the actual exhaust temperature obtained by a vehicle bench calibration experiment, and accurately estimating the exhaust temperature of an SCR catalytic reaction position according to the mapping relation and signals collected by the temperature sensor. The data obtained in this way are more accurate and easier to implement for the vehicle structure.

In order to obtain more accurate data, the method in (2) above may also be modified, for example, a parameter modification MAP table for modification is obtained in advance through a bench and a whole vehicle experiment, the ECU unit collects an ambient temperature signal from a whole vehicle atmospheric temperature sensor and then performs table lookup on the MAP to obtain a modification coefficient, and the actual exhaust temperature is modified.

Step S3: and calculating the difference value between the exhaust temperature demand value and the actual exhaust temperature value, and calculating the heating demand current value of the heating unit through a PID logic unit. The PID logic unit is often arranged in the existing devices such as a PID controller and the like, the PID logic unit processes data based on a PID algorithm, the PID algorithm is the most classical and simple algorithm which can reflect the feedback control idea in the control industry and is also commonly used for related control of direct current motor driving, similarly, the step can calculate the heating required current value based on the same principle of the PID algorithm, the current value can also be influenced by various parameters (such as resistance value and the like) of the characteristics of the heating unit, and therefore the required current value obtained through the PID logic unit is only matched with the heating unit corresponding to the moment. It should be noted that the PID logic unit belongs to the prior art, and those skilled in the art can also fine-tune the overall architecture thereof to obtain the desired result according to their own needs without creative efforts, and therefore, the PID logic unit and the PID algorithm are not described herein again.

Step S4: the heat control unit accurately controls the heating unit to heat the exhaust gas according to the heating demand current value, the heat generated by the larger current is larger, the temperature of the exhaust gas is higher, and finally the exhaust gas temperature reaches the exhaust gas temperature demand value set in the step S1, so that the dynamic balance of the SCR working efficiency is ensured. Preferably, the thermal control unit is integrated with a current controller capable of ensuring that the current is output at a value of the heating demand current value.

Thermal management of the engine exhaust gas has been completed through steps S1 to S4 of the above embodiment so that the engine exhaust gas meets the criteria of nation six.

As shown in fig. 2, in some embodiments of the present invention, the actual result and the estimated value calculated by the PID logic unit deviate due to the fact that the exhaust temperature is affected by many external conditions during actual vehicle operation. To solve this problem, a first correction factor may be added to perform correction compensation when the PID logic unit performs calculation using the PID algorithm in step S3, so as to obtain a more accurate heating demand current value. The first correction factor may be part or all of the following parameters: the engine intake temperature, the measured exhaust temperature, the atmospheric environment temperature and the nitrogen oxide emission value. The temperature values CAN be detected by temperature sensors arranged at corresponding positions, and the nitrogen oxide emission value CAN be detected by the existing nitrogen oxide sensors, uploaded to an ECU (electronic control unit) through a CAN (controller area network) bus and then sent to a heat control unit. Preferably, the parameters of the first correction factor may be obtained through a bench calibration experiment to obtain a MAP table corresponding to the input variables of the PID logic unit, and the PID calculation model is corrected and compensated by the thermal control unit in a manner of referring to the MAP table, so as to improve the accuracy of the calculation result.

In some embodiments of the invention, the heating demand current value is a standard quantity which in actual operation the thermal control unit also requires a control quantity which the thermal control unit can understand and control accordingly. Preferably, the control amount is a PWM duty for controlling the current, and the heating unit is controlled by the calculated PWM duty to change the heating temperature according to different situations and maintain the temperature of the exhaust gas to a target temperature. Therefore, step S4 preferably further includes the steps of:

s401: acquiring an actual current output value;

s402: calculating the difference value between the heating demand current value and the actual current output value and calculating by a PID logic unit to obtain a PWM duty ratio;

s403: the thermal control unit controls the heating unit to heat exhaust gas based on the PWM duty cycle.

The PID algorithm adopted by the PID logic unit in step S402 has the same principle as the PID algorithm in step S3, and is not described in detail.

As an embodiment of the present invention, the output current may be sampled and analyzed in real time by a single chip microcomputer C8051F410 disposed in the thermal control unit, a sampling value (actual current output value) is compared with a set value (heating demand current value), a DA output of the single chip microcomputer is adjusted by using a result of the comparison, a TL494 (switching power supply pulse width modulation control chip) adjusts a PWM duty ratio by using a voltage output by the DA output of the single chip microcomputer, and a purpose of constant current output is achieved by feedback control. Wherein, TL494 is a fixed frequency pulse width modulation circuit, has built-in linear sawtooth oscillator, and the oscillation frequency can be adjusted through an external resistance and a electric capacity, and its oscillation frequency is as follows:

the drive pulse generator, pulse width modulator, and various protection circuits are all completed by TL 494. The TL494 is internally composed of two comparators, two groups of error amplifiers, a 5V reference voltage source and the like, and the TL494 is widely applied to high-power switching power supplies.

In some embodiments of the present invention, the control of the heating unit by the thermal control unit is also greatly interfered by the external environment, so it is necessary to supplement the PID algorithm in step S402 with a second correction factor to obtain a more accurate calculation result, where the second correction factor may be part or all of the following parameters: the actual current output value, the regeneration state of the DPF in the exhaust passage, the temperature of the engine coolant, and the parameters of the above-mentioned second correction factor may be detected by corresponding sensors and transmitted to the ECU unit or the thermal control unit through the CAN bus. Preferably, the parameters of the second correction factor may be obtained through a bench calibration experiment to obtain a MAP table corresponding to the input quantity in the PID algorithm in step S402, and the PID calculation model is corrected and compensated by looking up the MAP table, so as to improve the accuracy of the calculated PWM duty ratio.

In addition to the above-described method of heating exhaust gas, the heat management method of the present invention further includes a heat recovery step of: the heat recovery unit recovers heat of the exhaust pipeline and converts the heat into electric energy to be stored in the storage battery. The heat recovery unit can adopt heat recovery systems such as a temperature difference power generation system, a Rankine cycle system and the like, and in the related technical field at present, the Cormins company applies waste gas waste heat recovery to a heavy diesel engine and is in the leading position in the world. The main technical characteristic is that the waste heat of the EGR and the exhaust of the diesel engine is used as a heat source for recycling, thereby improving the economic performance of the diesel engine. The recovered heat is stored by the storage battery, and when needed, the electric energy of the storage battery is converted into heat energy by the heating power supply to be used for heating and exhausting, so that the circulation of energy is realized, and good economic benefit and environmental protection value are generated.

In another aspect, an embodiment of the present invention further discloses an engine exhaust heat management system, which can implement the methods disclosed in the above embodiments, and as shown in fig. 3, the engine exhaust heat management system includes a DPF unit (particulate trap) and an SCR catalytic unit (selective catalytic reduction) disposed in an engine exhaust pipeline, and further includes the following parts:

(1) and the sensor module is used for acquiring exhaust state information and transmitting the exhaust state information to an ECU (electronic control unit) of the vehicle. For the present embodiment, the sensor module mainly detects the exhaust temperature and the pollutant concentration at each location, wherein the temperature of the engine exhaust before entering the SCR unit is detected by the temperature sensor in fig. 3, which is a precondition for obtaining the necessary parameters for the thermal control unit to accurately control the current, and the temperature sensor CAN directly send the temperature information to the thermal control unit, or upload the temperature information to the ECU unit through the CAN bus. The accuracy of the calculation of the necessary parameters can be improved more effectively by arranging a plurality of temperature sensors to detect the temperatures of different positions; the nitrogen oxide sensor can objectively reflect the pollutant concentration and the actual treatment effect of the exhaust gas, and can also be used as a first correction factor to correct and compensate the calculation of the PID logic unit so as to obtain a more accurate heating demand current value. One embodiment, as shown in fig. 4, includes an engine exhaust conduit provided with: the engine outlet nitrogen oxide sensor, the DOC inlet temperature sensor, the DPF outlet temperature sensor, the SCR inlet temperature sensor, the SCR outlet temperature sensor, and some other temperature sensors such as an ambient temperature sensor may also be disposed on the vehicle, but are not disposed at the engine exhaust duct position, and therefore are not shown in fig. 4, and these temperature sensors not shown are in communication connection with the ECU unit through the CAN bus, so that the thermal control unit CAN also obtain data detected by these temperature sensors through transmission by the ECU unit.

(2) And the heating unit is used for heating the exhaust gas in the exhaust pipeline. The principle of the exhaust heating device is that electric energy, particularly electric energy converted by waste heat recovery is converted into heat energy to heat low-temperature exhaust, the heating unit can be electrified by the heating wire to heat, the heating wire is electrically connected with the heat control unit, and the current of the heating wire is controlled by the heat control unit, so that the heating amount of the heating wire is not constant but changes in real time according to the change of the exhaust temperature caused by the working condition of an engine, the heating wire can be arranged outside the exhaust pipeline to wrap the exhaust pipeline, and can also be arranged inside the exhaust pipeline to heat the exhaust to the maximum extent, and the heating wire 9 can be arranged in an interlayer of the exhaust pipeline as shown in figure 5, so that the exhaust heating device can heat the exhaust with the maximum efficiency and cannot influence the flow of the exhaust.

(3) The heat control unit is connected with and controls the heating unit, preferably, a current controller is arranged in the heat control unit or externally connected with the heat control unit, the current of the heating unit CAN be controlled through the PWM duty ratio, the heat control unit is in communication connection with the ECU unit, information transmitted by the ECU unit CAN be received through a CAN bus, data are processed and calculated through a microprocessor of the heat control unit, a heating required current value and the PWM duty ratio are obtained by the heat control unit, meanwhile, correction compensation calculation of correction factors is also completed by the heat control unit, the microprocessor CAN adopt a commercially available control chip, and the heat control unit CAN also adopt a mature PLC device. The thermal control unit is internally provided with a PID logic unit for carrying out PID calculation to obtain the heating required current and the corresponding duty ratio.

(4) The heat recovery unit corresponds to the position of the exhaust pipeline and is used for recovering the heat energy of the exhaust and converting the heat energy into electric energy; the heat recovery unit may adopt a temperature difference power generation system, a rankine cycle system, and other heat recovery systems, and the implementation system of the above conventional heat recovery unit is known to those skilled in the art and will not be described in detail herein.

(5) The storage battery is used for storing the electric energy converted by the heat recovery unit and supplying power to the heating unit, the required storage battery can be arranged independently, and can also be an on-board storage battery of the vehicle, in this case, the recovered electric energy can be used for heating the exhaust gas and can also be supplied to other electric devices of the vehicle, and on the other hand, when the recovered electric energy is insufficient and the exhaust gas needs to be heated, the on-board storage battery with larger capacity can effectively ensure the normal operation of heating.

The exhaust heat management can be realized through the structure, and the specific working process is as follows:

firstly, the ECU unit detects the working condition of an engine in real time and obtains an exhaust temperature demand value by looking up an engine working condition MAP table, and the ECU unit sends the exhaust temperature demand value to the thermal control unit; then, the thermal control unit also receives sensor information transmitted by the ECU unit and/or directly transmitted by each sensor, and estimates the actual exhaust temperature value of the SCR catalytic reaction; then, the exhaust temperature required value and the actual exhaust temperature value are utilized through a PID algorithm, correction compensation of a first correction factor is added to obtain a heating required current value, and the PWM duty ratio can be further calculated for convenient control; the heat control unit controls the heating unit to heat the exhaust through the PWM duty ratio, so that the SCR catalytic reaction can be performed normally and efficiently, and the thermal management of the engine exhaust is realized.

For DPF (diesel oxidation catalyst) units, regeneration at high exhaust temperatures is required, and therefore the thermal management method and apparatus provided by the present invention can also be applied to DPF units, and the specific methods and procedures are described above with reference to fig. 1-5, and the specific work procedures described above.

The DPF unit and the SCR unit are in the same exhaust duct, and therefore the present invention provides an embodiment that ensures that DPF regeneration and SCR catalysis are performed simultaneously and efficiently by thermal management of the exhaust gas. For the SCR catalysis, the required temperature of DPF regeneration is the same as long as the required temperature is ensured within a certain temperature interval range, so that by using the method provided by the invention, the heating required current value range required by the SCR catalysis and the heating required current value range required by the DPF regeneration can be obtained, then the thermal control unit selects any point value of an overlapping region between the heating required current value range and the heating required current value range as a target heating required current value, and the corresponding PWM duty ratio is calculated through the PID logic unit, so that the DPF regeneration and the SCR catalysis can be simultaneously carried out efficiently.

In other embodiments, the thermal control unit is connected with a plurality of heating units, and the current amount of each heating unit can be separately controlled, so that different sections of the exhaust pipeline can be heated differently according to requirements, and the temperature requirements of different pollutant treatment devices can be met respectively.

The arrangement of the thermal control unit is convenient for modifying the existing vehicle system, but in other embodiments, the thermal control unit is an ECU unit of the vehicle, the processing, PID calculation and correction compensation of each sensor data are completed through the ECU unit, the ECU unit is connected with the current controller through a CAN bus, and the PWM duty ratio obtained through calculation controls the current controller so as to control the heating power of the heating wire.

As shown in fig. 4, a structure diagram of a complete engine exhaust pipe is shown, which includes: turbocharger 1, exhaust throttle valve 2, engine outlet nitrogen oxide sensor 401, DOC inlet temperature sensor 402, DPF inlet temperature sensor 403, DPF outlet temperature sensor 404, SCR inlet temperature sensor 405, SCR outlet temperature sensor 406, exhaust outlet nitrogen oxide sensor 407, DOC unit 5, DPF unit 6, urea nozzle 701, SCR unit 702, ASC unit 8.

For the newly-developed national six standards, it is not enough to pass through only the SCR catalytic unit and the DPF unit, and other devices are also needed to ensure the exhaust gas to reach the standard, and a DOC unit and an ASC unit (ammonia escape catalyst) for treating the exhaust gas are also arranged in the exhaust pipeline, wherein the DOC unit is adjacent to the DPF unit, and the ASC unit is adjacent to the SCR catalytic unit, wherein the DOC unit is a diesel Oxidation catalytic unit, so-called DOC (diesel Oxidation catalyst) technology, that is, Oxidation catalytic technology for after-treatment of the exhaust gas of the diesel engine. The DOC uses precious metals such as platinum (Pt) and palladium (Pd) as catalysts, and mainly reduces the content of SOF in the emission of the fine materials, thereby reducing the emission of PM. In the prior art, an ASC unit is used to treat ammonia-containing compounds in substances ejected from a urea nozzle in an SCR catalytic unit.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and the simple modifications all belong to the protection scope of the embodiments of the present invention.

It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention do not describe every possible combination.

Those skilled in the art will understand that all or part of the steps in the method according to the above embodiments may be implemented by a program, which is stored in a storage medium and includes several instructions to enable a single chip, a chip, or a processor (processor) to execute all or part of the steps in the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

In addition, any combination of various different implementation manners of the embodiments of the present invention is also possible, and the embodiments of the present invention should be considered as disclosed in the embodiments of the present invention as long as the combination does not depart from the spirit of the embodiments of the present invention.

Claims

1. An engine exhaust heat management method, comprising the steps of:

s1: under the working state of an engine, acquiring a current engine working condition parameter value sent by an ECU (electronic control unit) of a vehicle in real time, and acquiring an exhaust temperature requirement value of an engine exhaust pipeline corresponding to the current engine working condition parameter value through a pre-stored mapping table of the engine working condition parameter and the exhaust temperature requirement;

s3: calculating a heating demand current value of an engine exhaust pipeline through a PID logic unit arranged in a heating unit of a vehicle according to the difference value between the exhaust temperature demand value and the actual exhaust temperature value; supplementing a first correction factor in the calculation of the PID logic unit, and performing correction compensation on the heating demand current value; the first correction factor comprises at least one of an engine air inlet temperature, an actually measured exhaust temperature, an atmospheric environment temperature and a nitrogen oxide emission value;

2. The engine exhaust heat management method according to claim 1, wherein the step S2 of obtaining the actual exhaust temperature value of the engine exhaust pipeline in the selective catalytic reduction process in real time comprises:

3. The engine exhaust heat management method according to claim 1, wherein controlling a heating unit of a vehicle to heat exhaust gas of an engine exhaust pipe according to the heating demand current value in step S4 includes:

s401: acquiring an actual current output value of a heating unit of a vehicle;

4. The engine exhaust heat management method according to claim 3, characterized in that step S402 further comprises:

5. The engine exhaust heat management method of claim 1, further comprising a heat recovery step:

6. An engine exhaust heat management system comprising a particle trap and a selective catalytic reduction unit disposed in an engine exhaust conduit, the particle trap for trapping particulate pollutants and the selective catalytic reduction unit for treating nitrogen oxide pollutants, the heat management apparatus further comprising:

the thermal control unit comprising PID logic, the thermal control unit to:

calculating a heating demand current value of an engine exhaust pipeline according to the difference value of the exhaust temperature demand value and the actual exhaust temperature value through a PID logic unit, supplementing a first correction factor in the calculation of the PID logic unit, correcting and compensating the heating demand current value, and controlling a heating unit of a vehicle to heat exhaust of the engine exhaust pipeline according to the heating demand current value; the first correction factor comprises at least one of an engine air inlet temperature, an actually measured exhaust temperature, an atmospheric environment temperature and a nitrogen oxide emission value;

7. The engine exhaust thermal management system of claim 6, wherein the thermal control unit obtains a current engine operating condition parameter value sent by an ECU unit of the vehicle in real time through a CAN bus of the vehicle, and obtains an exhaust temperature demand value of the engine exhaust conduit corresponding to the current engine operating condition parameter value through a pre-stored mapping table of the engine operating condition parameter and the exhaust temperature demand.

8. The engine exhaust thermal management system of claim 6, wherein the thermal control unit obtains temperature information in the engine exhaust conduit collected by the sensor module in real time and estimates an actual exhaust temperature value of the engine exhaust conduit during the selective catalytic reduction reaction based on the temperature information.

9. The engine exhaust thermal management system of claim 6, wherein the thermal control unit is configured to obtain an actual current output value of the heating unit of the vehicle, calculate a difference between the heating demand current value and the actual current output value, and calculate a PWM duty cycle for controlling current through a PID logic unit provided in the heating unit of the vehicle, and control the heating unit of the vehicle to heat exhaust gas of an engine exhaust pipe based on the PWM duty cycle.

10. The engine exhaust thermal management system of claim 9, wherein a second correction factor is added to the calculation of the PID logic to correct and compensate the PWM duty cycle.

11. The engine exhaust heat management system of claim 6, further comprising:

12. The engine exhaust thermal management system of claim 6, wherein the sensor module comprises: a temperature sensor unit and a NOx sensor unit in respective communicative connection with the ECU unit.

13. The engine exhaust thermal management system of claim 6, wherein an engine exhaust conduit of a vehicle is further provided with a diesel oxidation catalyst unit for treating exhaust gas adjacent the particulate trap and an ammonia slip catalyst unit adjacent the selective catalytic reduction unit.