CN106948912B - Diesel engine post-treatment exhaust heat management method and device - Google Patents

Diesel engine post-treatment exhaust heat management method and device Download PDF

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Publication number
CN106948912B
CN106948912B CN201710203599.2A CN201710203599A CN106948912B CN 106948912 B CN106948912 B CN 106948912B CN 201710203599 A CN201710203599 A CN 201710203599A CN 106948912 B CN106948912 B CN 106948912B
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temperature
scr
doc
temperature raising
throttle valve
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CN106948912A (en
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苗垒
刘洋
袁俊
王鹏飞
刘法学
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Wuxi Weifu Lida Catalytic Converter Co Ltd
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Wuxi Weifu Lida Catalytic Converter Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/36—Arrangements for supply of additional fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0002—Controlling intake air
    • F02D41/0007—Controlling intake air for control of turbo-charged or super-charged engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D9/00—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits
    • F02D9/02—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits concerning induction conduits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2430/00—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics
    • F01N2430/06—Influencing exhaust purification, e.g. starting of catalytic reaction, filter regeneration, or the like, by controlling engine operating characteristics by varying fuel-air ratio, e.g. by enriching fuel-air mixture
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
    • F01N2900/1404—Exhaust gas temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D9/00—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits
    • F02D9/02—Controlling engines by throttling air or fuel-and-air induction conduits or exhaust conduits concerning induction conduits
    • F02D2009/0201—Arrangements; Control features; Details thereof
    • F02D2009/0222—Exhaust gas temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/0002—Controlling intake air
    • F02D2041/0022—Controlling intake air for diesel engines by throttle control
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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

Abstract

The invention relates to a method and a device for managing exhaust heat of diesel engine post-treatment, which is characterized by comprising the following steps: (1) releasing the SCR temperature raising requirement according to the SCR front temperature and the SCR front target temperature; (2) releasing DOC temperature raising requirements according to the DOC front temperature and the DOC front target temperature; (3) if the SCR temperature raising requirement comes, inquiring the opening MAP of an SCR temperature raising throttle valve according to the rotating speed and the torque of the engine to obtain the minimum allowable opening of the throttle valve under the current engine working condition, and controlling the throttle valve to act to reduce the air inflow; if the DOC temperature raising requirement comes, inquiring the DOC temperature raising throttle valve opening MAP according to the engine speed and the torque to obtain the minimum opening allowed by the throttle valve under the current engine working condition, and controlling the throttle valve to act to reduce the air inflow; if the temperature raising requirements from the SCR and the DOC are received simultaneously, the temperature raising requirement of the DOC is responded firstly, and DOC temperature raising throttle valve opening MAP is executed. The invention can effectively improve the exhaust temperature and is applied to the post-treatment system of the national six-stage diesel engine.

Description

Diesel engine post-treatment exhaust heat management method and device
Technical Field
The invention relates to a method and a device for managing exhaust heat of diesel engine aftertreatment, belonging to the technical field of diesel engine aftertreatment system control.
Background
The SCR post-treatment technology is used for reducing NO in tail gas of diesel enginexThe basic principle of the method is that ammonia gas formed by injecting urea through hydrolysis and atomization is injected into a catalyst to react with NO in exhaust gasxOxidation-reduction reaction occurs to generate harmless nitrogen.
With the further tightening of national emission standards, SCR aftertreatment systems have been applied in batches in the emission control stages of state four and state five. China plans to implement the national six-stage emission control standard of diesel engines in 2020, so that the emission of pollutants of the diesel engines is close to the zero emission level. In order to meet the national six-stage emission control requirements, in general, diesel aftertreatment devices are mainly DOC, DPF, and SCR. The DOC has the main functions of oxidizing exhaust pollutants such as HC, CO and soluble organic salt; second oxidation of NO to NO2Further improving the SCR conversion efficiency; thirdly, the oxidized diesel releases heat, and the exhaust temperature is rapidly increased, so that the DPF can be actively regenerated to eliminate carbon particles. The main function of a DPF is to trap carbon particles while performing periodic regeneration of the carbon particles. The main function of SCR is to eliminate NO in tail gas by spraying urea under the action of catalystxA contaminant.
In the sixth stage of China, emission regulations adopt WHSC and WHTC circulation which are closer to actual working conditions to test emission pollutants. The WHTC cycle comprises a cold WHTC cycle and a hot WHTC cycle. The exhaust temperature of an engine in a WHTC cycle is low, and the optimal conversion efficiency of a catalyst is difficult to achieve, so that in order to meet strict national six emission requirements, a reasonable exhaust heat management strategy is needed to increase the exhaust temperature of a diesel engine when the temperature needs to be raised, so that the optimal reaction temperature interval of an SCR catalyst is achieved, and the national six emission control requirements are met.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method and a device for managing exhaust heat of diesel engine post-treatment, which can effectively increase the exhaust temperature and are applied to a national six-stage diesel engine post-treatment system.
According to the technical scheme provided by the invention, the thermal management device for the exhaust gas after the diesel engine is characterized in that: the system mainly comprises an engine, a cooler, an air inlet pipe, a supercharger, an exhaust pipe, a throttle valve, a tail pipe oil injection system, a DOC front temperature sensor, a DPF front temperature sensor, an SCR rear temperature sensor and a post-processing control unit DCU; the air inlet end of the engine is connected with one end of a cooler, the other end of the cooler is connected with a supercharger through an air inlet pipe, a throttle valve is arranged on a pipeline between the engine and a cooling pipe, the exhaust end of the engine is connected with a DOC, a DPF and an SCR which are sequentially arranged through an exhaust pipe, and a tail pipe oil injection system is arranged at the exhaust pipe in front of the DOC; a DOC front temperature sensor is arranged at the front end of the DOC, a DPF front temperature sensor is arranged at the front end of the DPF, and an SCR front temperature sensor and an SCR rear temperature sensor are respectively arranged at the front end and the rear end of the SCR; and the control end of the post-processing control unit DCU is connected with a throttle valve and a tail pipe oil injection system, and the throttle valve and the tail pipe oil injection system are controlled to realize the regulation of the exhaust temperature of the engine.
The diesel engine post-treatment exhaust heat management method is characterized by comprising the following steps of:
(1) comparing the SCR front temperature with the SCR front target temperature, and releasing the SCR temperature raising requirement if the SCR front temperature is lower than the SCR front target temperature;
(2) comparing the DOC front temperature with the DOC front target temperature, and if the DOC front temperature is lower than the DOC front target temperature, releasing DOC temperature raising requirements;
(3) the exhaust heat management state machine judges whether the temperature raising requirement comes from SCR temperature raising or DOC;
if the SCR temperature raising requirement comes, inquiring the opening MAP of an SCR temperature raising throttle valve according to the rotating speed and the torque of the engine to obtain the minimum allowable opening of the throttle valve under the current engine working condition, reducing the air inflow by controlling the action of the throttle valve, and raising the exhaust temperature;
if the DOC temperature raising requirement comes, inquiring the DOC temperature raising throttle valve opening MAP according to the engine speed and the torque to obtain the minimum allowable opening of the throttle valve under the current engine working condition, and reducing the air inflow by controlling the action of the throttle valve to improve the exhaust temperature;
if the temperature raising requirements from the SCR and the DOC are received at the same time, the temperature raising requirement of the DOC is responded firstly, and the DOC temperature raising throttle valve opening MAP is executed; and only when the DOC temperature raising requirement is closed, the SCR temperature raising requirement is responded.
Furthermore, when the temperature of the throttle valve cannot meet the temperature raising requirement of the SCR, tail pipe oil injection is adopted to raise the temperature so as to further raise the exhaust temperature.
Further, the specific process of tail pipe oil injection temperature raising is as follows: firstly, calculating the required open-loop fuel injection quantity according to the exhaust flow, the DOC front temperature and the SCR target temperature; inquiring closed-loop correction MAP according to the target temperature before SCR and the current temperature before SCR to obtain a closed-loop correction coefficient; and multiplying the correction coefficient by the open-loop fuel injection quantity to obtain the closed-loop fuel injection quantity.
Further, after the SCR temperature raising requirement is subjected to delay filtering processing, the SCR temperature raising requirement is judged by an exhaust heat management state machine.
Further, after the DOC temperature raising requirement is subjected to delay filtering processing, the DOC temperature raising requirement is judged by an exhaust heat management state machine.
The invention has the following advantages:
(1) the invention can effectively improve the exhaust temperature of the diesel engine, thereby providing the optimal reaction temperature for the post-treatment SCR reaction;
(2) the invention can effectively improve the exhaust temperature of the diesel engine, thereby providing proper exhaust temperature for the regeneration of the post-treatment DPF;
(3) the invention can flexibly control the throttle valve and the tail pipe to spray oil to change the post-treatment exhaust temperature, and has no influence on the performance of the engine body;
(4) the invention utilizes an accurate temperature closed-loop control strategy, can carry out self-adaptive regulation on the exhaust temperature and ensures that the post-treatment system fully exerts the performance.
Drawings
FIG. 1 is a logical block diagram of a diesel aftertreatment exhaust heat management method of the present invention.
FIG. 2 is a logic block diagram of the SCR temperature demand module.
FIG. 3 is a logic block diagram of the DPF regeneration temperature demand module.
FIG. 4 is a logic block diagram of the throttle ramp module.
FIG. 5 is a logic block diagram of the tailpipe fuel injection temperature raising module.
FIG. 6 is a schematic diagram of a diesel aftertreatment exhaust heat management device of the invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 6, the thermal management device for exhaust gas after-treatment of the diesel engine mainly comprises an engine 1, a cooler 2, an air inlet pipe 3, a supercharger 4, an exhaust pipe 5, a throttle valve 6, a tail pipe fuel injection system 7, a DOC front temperature sensor 8, a DPF front temperature sensor 9, a SCR front temperature sensor 10, an SCR rear temperature sensor 11, an after-treatment control unit DCU12 and other components; the air inlet end of the engine 1 is connected with one end of a cooler 2, the other end of the cooler 2 is connected with a supercharger 4 through an air inlet pipe 3, a throttle valve 6 is arranged on a pipeline between the engine 1 and the cooling pipe 2, the exhaust end of the engine 1 is connected with a DOC, a DPF and an SCR which are sequentially arranged through an exhaust pipe 5, and a tail pipe oil injection system 7 is arranged at the exhaust pipe 5 in front of the DOC; a DOC front temperature sensor 8 is arranged at the front end of the DOC, a DPF front temperature sensor 9 is arranged at the front end of the DPF, and an SCR front temperature sensor 10 and an SCR rear temperature sensor 11 are respectively arranged at the front end and the rear end of the SCR; the post-processing control unit DCU12 controls the throttle valve 6 and the tail pipe fuel injection system 7 to regulate the temperature of the engine exhaust, so as to realize the management of the engine exhaust temperature.
As shown in fig. 1, the basic idea of the diesel engine aftertreatment exhaust heat management method of the present invention is to increase the exhaust temperature by adjusting the throttle valve and the tailpipe injection mechanism by the exhaust heat management state machine according to the SCR temperature increase requirement and the temperature requirement during DPF regeneration. When the system judges that the temperature of the DOC or the SCR needs to be raised, firstly, the throttle valve is adjusted, and the opening degree of the throttle valve is reduced, so that the air inflow of the engine is reduced, and the exhaust temperature can be effectively raised. If the temperature required by the SCR is difficult to reach only by adjusting the throttle valve, a tail pipe oil injection measure is needed for temperature increase. And a proper amount of diesel oil is sprayed through the tail pipe oil injection device to oxidize and release heat on the DOC, so that the SCR temperature is further increased, and the emission requirement is met.
As shown in fig. 1, the method for managing heat of exhaust gas after diesel engine treatment according to the present invention is mainly completed by the following modules: the system comprises an SCR temperature demand module, a DPF regeneration temperature demand module, a throttle valve temperature raising module and a tail pipe oil injection temperature raising module.
The specific control logic for each module is as follows:
(1) an SCR temperature demand module:
the SCR temperature increase requirement aims at rapidly increasing the exhaust gas temperature at the inlet of the SCR catalyst so as to enable the exhaust gas temperature to enter a catalyst optimum efficiency temperature range (about 250 ℃ ~ 400 ℃) and improve the conversion efficiency of the catalyst, as shown in FIG. 2, according to comparison between the SCR front temperature and the SCR front target temperature, if the SCR front temperature is lower than the target temperature, the SCR temperature increase requirement is released, in order to prevent occurrence of accidents, the SCR temperature increase requirement is subjected to delay filtering treatment, namely, a temperature increase requirement system continuously performs corresponding treatment only for a period of time.
(2) DPF regeneration temperature demand module:
the purpose of DPF regeneration temperature raising requirement is that when the temperature in front of DOC is lower (about < 250 ℃), the fuel sprayed onto DOC can not be oxidized by DOC to release heat, and the high temperature above 550 ℃ required by DPF active regeneration is difficult to reach, so when the DOC temperature is lower than 250 ℃, thermal management is required to rapidly raise DOC exhaust temperature. The same as the SCR temperature raising module, as shown in fig. 3, the DOC temperature raising requirement is released if the DOC front temperature is lower than the target temperature, according to the DOC front temperature and the DOC front target temperature. In order to prevent the occurrence of the accident, the DOC temperature raising requirement is subjected to delay filtering treatment, namely, the DOC temperature raising requirement is continuously met within a period of time, and the DOC temperature raising requirement is correspondingly met.
(3) The throttle valve temperature raising module:
as shown in fig. 4, it is determined whether the temperature request is from the SCR temperature increase or the DOC temperature increase according to the exhaust heat management state machine. If the SCR temperature raising requirement comes, inquiring the opening MAP of an SCR temperature raising throttle valve according to the rotating speed and the torque of the engine to obtain the minimum allowable opening of the throttle valve under the current engine working condition, reducing the air inflow by controlling the action of the throttle valve, and raising the exhaust temperature; similarly, if the DOC temperature raising requirement comes, the DOC temperature raising throttle opening MAP is inquired according to the rotating speed and the torque of the engine, the minimum allowable opening of the throttle under the current engine working condition is obtained, the air inflow is reduced by controlling the action of the throttle, and the exhaust temperature is improved. If the temperature raising requests from the SCR and the DOC are received simultaneously, the temperature raising request of the DOC is responded firstly, and DOC temperature raising throttle valve opening MAP is executed. And only when the DOC temperature rise request is closed, the SCR temperature rise request is responded.
(4) Tail pipe oil spout raises the temperature module:
when the temperature of the throttle valve cannot meet the temperature raising requirement of the SCR, a tail pipe oil injection temperature raising module is adopted to further raise the exhaust temperature. Generally, the six aftertreatment systems in China are mainly DOC-DPF-SCR, and the DOC is placed at the upstream of the SCR, namely exhaust firstly passes through the DOC and the DPF and then passes through the SCR and then is discharged. Therefore, when the aftertreatment exhaust gas is heated, the DOC and the DPF are first heated, and then the SCR is heated. Therefore, when the SCR is lower than the target temperature, the DOC temperature can already meet the temperature condition of the fuel injection oxidation heat release. Injecting proper diesel oil on the DOC for oxidation heat release can further increase the exhaust temperature before SCR. As shown in fig. 5, the required open-loop fuel injection amount may be calculated first based on the exhaust flow rate, the pre-DOC temperature, and the SCR target temperature. And inquiring closed-loop correction MAP according to the target temperature before SCR and the current temperature before SCR to obtain a closed-loop correction coefficient. And multiplying the correction coefficient by the open-loop fuel injection quantity to obtain the closed-loop fuel injection quantity, so that the SCR temperature raising requirement can be met.

Claims (5)

1. A method of diesel engine aftertreatment exhaust heat management comprising the steps of:
(1) comparing the SCR front temperature with the SCR front target temperature, and releasing the SCR temperature raising requirement if the SCR front temperature is lower than the SCR front target temperature;
(2) comparing the DOC front temperature with the DOC front target temperature, and if the DOC front temperature is lower than the DOC front target temperature, releasing DOC temperature raising requirements;
(3) the exhaust heat management state machine judges whether the temperature raising requirement comes from SCR temperature raising or DOC;
if the SCR temperature raising requirement comes, inquiring the opening MAP of an SCR temperature raising throttle valve according to the rotating speed and the torque of the engine to obtain the minimum allowable opening of the throttle valve under the current engine working condition, reducing the air inflow by controlling the action of the throttle valve, and raising the exhaust temperature;
if the DOC temperature raising requirement comes, inquiring the DOC temperature raising throttle valve opening MAP according to the engine speed and the torque to obtain the minimum allowable opening of the throttle valve under the current engine working condition, and reducing the air inflow by controlling the action of the throttle valve to improve the exhaust temperature;
if the temperature raising requirements from the SCR and the DOC are received at the same time, the temperature raising requirement of the DOC is responded firstly, and the DOC temperature raising throttle valve opening MAP is executed; and only when the DOC temperature raising requirement is closed, the SCR temperature raising requirement is responded.
2. The diesel aftertreatment exhaust heat management method of claim 1, wherein: when the temperature of the throttle valve cannot meet the temperature raising requirement of the SCR, tail pipe oil injection is adopted to raise the temperature so as to further raise the exhaust temperature.
3. The diesel aftertreatment exhaust heat management method of claim 2, wherein: the specific process of tail pipe oil injection and temperature raising is as follows: firstly, calculating the required open-loop fuel injection quantity according to the exhaust flow, the DOC front temperature and the SCR target temperature; inquiring closed-loop correction MAP according to the target temperature before SCR and the current temperature before SCR to obtain a closed-loop correction coefficient; and multiplying the correction coefficient by the open-loop fuel injection quantity to obtain the closed-loop fuel injection quantity.
4. The diesel aftertreatment exhaust heat management method of claim 1, wherein: and after the SCR temperature raising requirement is subjected to delay filtering processing, judging by an exhaust heat management state machine.
5. The diesel aftertreatment exhaust heat management method of claim 1, wherein: and after the DOC temperature raising requirement is subjected to delay filtering processing, judging by an exhaust heat management state machine.
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