CN108716433B - Engine thermal management system and control method thereof - Google Patents

Engine thermal management system and control method thereof Download PDF

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Publication number
CN108716433B
CN108716433B CN201810182660.4A CN201810182660A CN108716433B CN 108716433 B CN108716433 B CN 108716433B CN 201810182660 A CN201810182660 A CN 201810182660A CN 108716433 B CN108716433 B CN 108716433B
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engine
proportional valve
bypass
temperature
air
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CN108716433A (en
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刘汉辉
王辉
李明星
陆寿域
曹磊
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Guangxi Yuchai Machinery Co Ltd
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Guangxi Yuchai Machinery Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B29/00—Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04—Cooling of air intake supply
    • 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
    • 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
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B29/00—Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04—Cooling of air intake supply
    • F02B29/0493—Controlling the air charge temperature
    • 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)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

The invention discloses an engine heat management system, which comprises: engine intake pipe, engine air inlet manifold, intercooler and booster compressor, engine thermal management system still includes: the bypass pipeline for controlling the air inlet temperature is provided with a first bypass proportional valve, and the bypass pipeline for controlling the air inlet temperature realizes bypass of the flow rate of the intercooled air inlet with different flow rates by adjusting the position proportion of the first bypass proportional valve; the two ends of the bypass pipeline are respectively connected with the inlet of the compressor and the outlet of the compressor and are connected with the compressor of the supercharger in parallel, a second bypass proportional valve is arranged on the bypass pipeline for controlling the air inflow, and the air inflow requirements under different working conditions are realized by adjusting the opening degree of the second bypass proportional valve; and the temperature sensor is arranged on a pipeline of an engine air inlet main pipe and used for measuring the air inlet temperature entering the engine air inlet main pipe, and the ECU can acquire the measured value of the air inlet temperature.

Description

Engine thermal management system and control method thereof
Technical Field
The invention relates to the technical field of engine thermal management, in particular to an engine thermal management system and a control method thereof.
Background
With the increasing requirements of environmental protection and the stricter emission regulations, the requirement of ensuring that the specific NOx emission reaches the limit value is one part of the most difficult requirements of tail gas emission. The NOx of the novel diesel engine with the WHTC cycle is reduced by nearly 80% compared with the NOx of the traditional diesel engine, and if engineering margin is considered, the NOx is reduced to 0.35g/kwh or even lower, and the aspect puts higher requirements on the efficiency of the SCR catalyst. On the other hand, the exhaust temperature of the engine cannot be too low, and the too low exhaust temperature affects the hydrolysis rate of urea and the SCR reaction rate, so that the risks of high urea fuel consumption ratio and excessive urea crystallization and emission are caused.
However, in order to improve the competitiveness of the product, the oil consumption of the host factory is one of the main competitiveness, and the optimal oil consumption or the optimal combination of the oil consumption and the urea consumption is one of the main means for ensuring the competitiveness of the product while reaching the emission limit. The currently common means is to reduce the injection timing and rail pressure of the engine, or to raise the exhaust temperature by additional injection, these means can reduce the NOx emission or raise the exhaust temperature to a certain extent, but all achieve the goal based on the means of sacrificing the oil consumption, and the capability of raising the temperature is very limited. Researches show that the WHTC circulating temperature is low, mainly because the temperature of a small-load or inverted working condition is low, the exhaust temperature of an engine can be raised through the thermal management of the small-load engine, the control of the intake temperature after intercooling is an effective method, meanwhile, the control of the gas flow of the gas before intercooling passing through an intercooler can effectively raise the intake temperature after intercooling, the reduction of the intake flow can further raise the exhaust temperature from the combustion angle, and the effect of 'open source' on the SCR bed temperature is achieved.
However, as shown in fig. 1, the existing engine thermal management system mainly has the following disadvantages:
1. for an engine with good oil consumption, the exhaust temperature is generally low, and for the minimum power section, the exhaust temperature can be increased only in a limited way, so that the improvement of the conversion efficiency of the SCR catalyst is not obviously contributed, but the sacrifice on the oil consumption is large, and the principle of lowest oil consumption and urea consumption cannot be realized.
2. The heat, such as the compressor outlet temperature, cannot be fully utilized, and most of the heat is absorbed by the intercooler. Such as EGR exhaust gas heat, is mostly absorbed by the EGR cooler, etc.
3. Although the throttle valve can play a good role in throttling, the negative pressure is high, and the oil leakage causes the problems of large PM emission and the like.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide an engine thermal management system, so that the defects that heat cannot be fully utilized and throttle negative pressure is large in the prior art are overcome.
To achieve the above object, the present invention provides an engine thermal management system, comprising: engine intake pipe, engine exhaust pipe, engine cylinder body, engine air inlet manifold, intercooler, booster compressor and aftertreatment system, engine thermal management system still includes: the bypass pipeline for controlling the air inlet temperature is provided with a first bypass proportional valve, and the bypass pipeline for controlling the air inlet temperature can realize bypass of flow of intercooling air inlet flows with different flows by adjusting the position proportion of the first bypass proportional valve; the two ends of the bypass pipeline are respectively connected with the inlet of the compressor and the outlet of the compressor and are connected with the compressor of the supercharger in parallel, a second bypass proportional valve is arranged on the bypass pipeline for controlling the air inflow, and the air inflow requirements of different working conditions are realized by adjusting the opening degree of the second bypass proportional valve; and the temperature sensor is arranged on a pipeline of an engine air inlet main pipe and used for measuring the air inlet temperature entering the engine air inlet main pipe, and the ECU can acquire the measured value of the air inlet temperature.
In a preferred embodiment, the aftertreatment system comprises: and the ECU can compare the acquired measured value of the air inlet temperature with the maximum air inlet temperature limit value, compare the average bed temperature of the SCR catalyst with the target bed temperature of the SCR catalyst, compare the actual air-fuel ratio with the target air-fuel ratio, and drive the first bypass proportional valve and the second bypass proportional valve to adjust according to the comparison result and a corresponding control strategy.
In a preferred embodiment, the aftertreatment system further comprises a NOx sensor, the target SCR catalyst bed temperature is dependent on a target efficiency of the SCR catalyst, the target efficiency being calculated; target efficiency is (actual measured value of NOx sensor-NOx target value satisfying engineering margin)/actual measured value of NOx sensor.
The invention also provides a control method of the engine heat management system, and the control methodThe preparation method comprises the following steps: (1) defining the engine to be in an idling working condition, a back-dragging working condition, a cold start working condition and other working conditions; (2) firstly, judging whether the engine is in a working state, enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is in the working state, and not enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is not in the working state; when the engine is in a working state, judging which working condition of an idling working condition, a back-dragging working condition, a cold start working condition or other working conditions the engine is in; (3) determining action control strategies of the first bypass proportional valve and the second bypass proportional valve according to an idle working condition, a back-dragging working condition or a cold start working condition of the engine, or determining a primary open-loop control strategy based on boundary conditions and a secondary closed-loop control strategy based on delta T according to other working conditions of the engine, wherein the delta T is T according to a formulab-TtIs calculated to obtain, wherein, TbIs the average bed temperature, T, of the SCR catalysttIs the target SCR catalyst bed temperature; and (4) adjusting the position of the first bypass proportional valve and the opening of the second bypass proportional valve according to the action control strategy, the primary open-loop control strategy or the secondary closed-loop control strategy in the step (3) to realize temperature control of the engine thermal management system.
In a preferred embodiment, the first-stage open-loop control strategy mainly takes the intake air temperature of an intake manifold and the air-fuel ratio as boundary conditions; the two-stage closed-loop control strategy is to realize the control of the exhaust temperature of the engine thermal management system by comparing the average bed temperature of the SCR catalyst with the target bed temperature of the SCR catalyst, comparing the actual air-fuel ratio with the target air-fuel ratio, and comparing the measured value of the air inlet temperature of the air inlet main pipe with the maximum air inlet temperature limit value.
In a preferred embodiment, an engine thermal management system comprises: engine intake pipe, engine exhaust pipe, engine cylinder body, engine air inlet manifold, intercooler, booster compressor and aftertreatment system, engine thermal management system still includes: the bypass pipeline for controlling the air inlet temperature is provided with a first bypass proportional valve, and the bypass pipeline for controlling the air inlet temperature can realize bypass of flow of intercooling air inlet flows with different flows by adjusting the position proportion of the first bypass proportional valve; the two ends of the bypass pipeline are respectively connected with the inlet of the compressor and the outlet of the compressor and are connected with the compressor of the supercharger in parallel, a second bypass proportional valve is arranged on the bypass pipeline for controlling the air inflow, and the air inflow requirements of different working conditions are realized by adjusting the opening degree of the second bypass proportional valve; and the temperature sensor is arranged on a pipeline of an engine air inlet main pipe and used for measuring the air inlet temperature entering the engine air inlet main pipe, and the ECU can acquire the measured value of the air inlet temperature.
In a preferred embodiment, when the engine is in an idle condition or a reverse-dragging condition, the control strategy is specifically as follows: adjusting the first bypass proportional valve to be in a full-open position, wherein the pipe diameter of the bypass pipeline which flows through the intercooler is smaller than that of the bypass pipeline which controls the air inlet temperature, only part of gas before intercooling flows through the intercooler, and the other part of gas directly flows to an air inlet main pipe of the engine to improve the exhaust temperature; and adjusting the second bypass proportional valve to be fully opened, and bypassing part of the engine to intake air so as to reduce the cooling of the SCR catalyst by low-temperature gas.
In a preferred embodiment, when the engine is in other working conditions, the control strategy is specifically as follows: (1) when Δ T <0, and Δ λ>0 and measured value of intake air temperature<When the maximum air inlet temperature is limited, the first bypass proportional valve is adjusted to be close to full open, so that the gas at the outlet of the compressor directly flows to an air inlet main pipe of the engine to improve the air inlet temperature; meanwhile, the second bypass proportional valve is partially opened or fully opened so as to reduce the flow of after-intercooling gas and improve the exhaust temperature; (2) when Δ T <0, but Δ λ<0 or measured value of intake air temperature>When the maximum inlet air temperature is limited, adjusting the first bypass proportional valve to be in a partially closed or fully closed position so as to cool the air at the outlet of the compressor through the intercooler; meanwhile, the second bypass proportional valve is adjusted to be fully or partially closed so as to ensure sufficient air inflow; (3) when the delta T is larger than or equal to 0, adjusting the first bypass proportional valve and the second bypass proportional valve to be closed completely so as to maintain the normal air intake mode; wherein Δ T is according to the formula Δ T ═ Tb-TtIs calculated to obtain, wherein, TbIs the average bed temperature, T, of the SCR catalysttIs the target SCR catalyst bed temperature; Δ λ is according to the formula Δ λ ═ λr-λtIs calculated to obtain, whereinrTo actual air-fuel ratio, λtIs the target air-fuel ratio.
In a preferred embodiment, when the engine is in the cold start condition, the control strategy is specifically as follows: the first bypass proportional valve is adjusted to be in a full open position, and the second bypass proportional valve is adjusted to be fully closed simultaneously to increase the intake air temperature.
In a preferred embodiment, the maximum inlet air temperature limit is 50 ℃.
Compared with the prior art, the engine thermal management system has the following beneficial effects:
(1) the air inlet temperature of partial load can be improved, the air-fuel ratio is reduced to a certain extent, the air inlet flow is reduced, the NOx ratio emission is reduced, and the oil consumption of the partial load is reduced.
(2) The average bed temperature of the SCR catalyst can be improved to a great extent, particularly for vehicles needing WHTC authentication, the bed temperature of the catalyst is an important factor of the efficient reaction of the SCR catalyst, and the means for improving the exhaust temperature of the engine thermal management system provided by the invention does not sacrifice the oil consumption, namely, the oil consumption is better while the exhaust is easier to pass through.
(3) The temperature and the efficiency of the SCR catalyst are improved, and meanwhile, the urea injection amount, the ammonia leakage and the risk of urea crystallization can be reduced; the NO of the engine can be increased properlyXThe original emission value improves the fuel economy of the engine.
Drawings
FIG. 1 is a schematic representation of a prior art engine thermal management system;
FIG. 2 is a schematic structural diagram of an engine thermal management system according to the present disclosure; and
FIG. 3 is a flow chart of a control strategy for a control method of an engine thermal management system according to the present disclosure.
Description of the main reference numerals:
1-engine exhaust pipe, 2-exhaust gas inlet pipe, 3-EGR cooler, 4-supercharger turbine, 5-EGR cooler water inlet, 6-EGR cooler water outlet, 7-vortex exhaust pipe, 8-aftertreatment system, 9-supercharger compressor, 10-supercharger air inlet pipeline, 11-intercooler, 12-throttle valve, 13-EGR valve, 14-engine air inlet pipe, 15-engine air inlet manifold, 16-engine cylinder body, 17-inlet air temperature control bypass pipeline, 18-first bypass proportional valve, 19-inlet air flow control bypass pipeline and 20-second bypass proportional valve.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the specific embodiments.
Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
As shown in fig. 2, an engine thermal management system according to a preferred embodiment of the present invention includes: the system comprises an engine exhaust pipe 1, an EGR cooler 3, a supercharger turbine 4, an aftertreatment system 8, a supercharger compressor 9, a supercharger air inlet pipeline 10, an intercooler 11, an engine air inlet pipe 14, an engine air inlet manifold 15 and an engine cylinder block 16. The engine thermal management system further comprises: a control intake air temperature bypass line 17, a control intake air temperature bypass line 19, and a temperature sensor. The two ends of the control inlet air temperature bypass pipeline 17 are respectively connected with an intercooler inlet and an intercooler outlet and are connected with the intercooler 11 in parallel, the control inlet air temperature bypass pipeline 17 is provided with a first bypass proportional valve 18, and the bypass of the flow of the intercooler inlet air flow with different flows can be realized by adjusting the position proportion of the first bypass proportional valve 18. The two ends of the bypass pipeline 19 for controlling the air inflow are respectively connected with the inlet and the outlet of the compressor and connected with the compressor of the supercharger9 are connected in parallel, a second bypass proportional valve 20 is arranged on the bypass pipeline 19 for controlling the air inflow, and the air inflow requirements of different working conditions are realized by adjusting the opening degree of the second bypass proportional valve 20. The temperature sensor is arranged on a pipeline of the engine air inlet main pipe 15 and used for measuring the air inlet temperature entering the engine air inlet main pipe 15, and the ECU can acquire the measured value T of the air inlet temperature2。
It should be noted that the present invention utilizes the formula Δ T ═ Tb-Tt、Δλ＝λr-λtDefine Δ T and Δ λ, where TbIs the average bed temperature, T, of the SCR catalysttIs the target SCR catalyst bed temperature; lambda [ alpha ]rTo actual air-fuel ratio, λtIs the target air-fuel ratio. It should be noted that the air-fuel ratio disclosed in the present disclosure is calculated according to a velocity density method, and since the intake air temperature is increased, the intake air density is decreased, and the intake air amount is decreased, it must be considered that the decrease of the intake air amount does not cause the smoke intensity of the engine to become larger, and the appropriate decrease of the intake air amount and the increase of the intake air temperature in the partial load are favorable for fuel consumption. The invention defines the engine load rate, and the load below 50 percent is part load.
In the above solution, the aftertreatment system 8 comprises an SCR catalyst, and the ECU is capable of collecting the measured value T of the intake air temperature2Comparing with the maximum inlet air temperature limit value to obtain the average bed temperature T of the SCR catalystbBed temperature T of target SCR catalysttComparing the air-fuel ratio lambda with the actual air-fuel ratio lambdarTo a target air-fuel ratio lambdatAnd comparing, and driving the first bypass proportional valve 18 and the second bypass proportional valve 20 to adjust according to the comparison result and a corresponding control strategy. The aftertreatment system 8 further comprises a NOx sensor, the target SCR catalyst bed temperature depends on the target efficiency of the SCR catalyst, the target efficiency is calculated and is less than the SCR catalyst limit efficiency at a certain temperature and airspeed; target efficiency is (actual measured value of NOx sensor-NOx target value satisfying engineering margin)/actual measured value of NOx sensor.
The control method of the engine thermal management system comprises the following steps: (1) defining that the engine is in idle working condition and is in reverse dragging workConditions, cold start conditions, and other conditions; (2) firstly, judging whether the engine is in a working state, enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is in the working state, and not enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is not in the working state; when the engine is in a working state, judging which working condition of an idling working condition, a back-dragging working condition, a cold start working condition or other working conditions the engine is in; (3) determining action control strategies of the first bypass proportional valve 18 and the second bypass proportional valve 20 according to the idle working condition, the back-dragging working condition or the cold start working condition of the engine, or determining a primary open-loop control strategy based on boundary conditions and a secondary closed-loop control strategy based on delta T according to other working conditions of the engine, wherein the delta T is determined according to the formulab-TtCalculating to obtain; and (4) adjusting the position of the first bypass proportional valve 18 and the opening degree of the second bypass proportional valve 20 according to the action control strategy, the primary open-loop control strategy or the secondary closed-loop control strategy in the step (3) to realize temperature control of the engine thermal management system.
In the scheme, the primary open-loop control strategy mainly takes the air inlet temperature and the air-fuel ratio of an air inlet main pipe as boundary conditions; the two-stage closed-loop control strategy is realized by comparing the average bed temperature of the SCR catalyst with the target bed temperature of the SCR catalyst, comparing the actual air-fuel ratio with the target air-fuel ratio and measuring the measured value T of the air inlet temperature of an air inlet main pipe2With maximum inlet air temperature limit TmaxAnd comparing to control the exhaust temperature of the engine thermal management system.
The flow of the control strategy of the engine thermal management system under various working conditions of the engine is as follows:
when the engine is in an idling working condition or a back-dragging working condition, the control strategy is specifically as follows: adjusting the first bypass proportional valve 18 to be in a full-open position, wherein the pipe diameter of the bypass pipeline 17 for controlling the air inlet temperature is smaller than that of the intercooler 11, only part of air before intercooling flows through the intercooler 11, and most of air directly flows to the air inlet main pipe 15 of the engine to improve the exhaust temperature; the second bypass proportional valve 20 is adjusted to be fully opened, and the engine bypasses part of the intake air to reduce the cooling of the SCR catalyst by the low-temperature gas.
When the engine is in other working conditions, the control strategy is specifically as follows: (1) when Δ T <0, and Δ λ>0 and measured value T of intake air temperature2<Maximum inlet air temperature limit TmaxAt this time, it is explained that the average temperature of the bed temperature of the SCR catalyst is lower than the target temperature and the actual air-fuel ratio lambda is at this timerHigher than target air-fuel ratio lambdatThe problems of large smoke intensity, poor oil consumption and the like caused by the reduction of the air inflow can be avoided, the first bypass proportional valve 18 is adjusted to be close to full open, and the gas at the outlet of the compressor directly flows to the engine air inlet main pipe 15 as much as possible so as to improve the air inlet temperature; at the same time, the second bypass proportional valve 20 is partially or fully opened to reduce the flow of after-intercooled air, and a portion of the air flows back to the air inlet to increase the exhaust temperature. (2) When Δ T <0, but Δ λ<0 or measured value T of intake air temperature2>Maximum inlet air temperature limit TmaxAt this time, although the average bed temperature of the SCR catalyst at this time is lower than the target value, the measured value T of the intake air temperature2Above the maximum inlet temperature limit TmaxAir intake is not facilitated, and the whole combustion is also deteriorated due to overhigh air intake temperature; on the other hand, if the actual air-fuel ratio λrBelow target air-fuel ratio lambdatThe problems of large smoke intensity, poor oil consumption and even insufficient dynamic property can be caused. The first bypass proportioning valve 18 must therefore be adjusted to a partially closed or fully closed position to allow the compressor outlet gas to be cooled through the intercooler 11; at the same time, the second bypass proportional valve 20 is adjusted to be fully or partially closed to ensure a sufficient amount of intake air. (3) When Δ T ≧ 0, both the first bypass proportional valve 18 and the second bypass proportional valve 20 are adjusted to be fully closed to maintain the normal intake mode. Maximum inlet air temperature limit TmaxLess than or equal to 50 ℃. In a preferred embodiment of the present invention, as shown in FIG. 3, the maximum inlet temperature limit T ismaxIs 50 ℃.
When the engine is in a cold start working condition, the control strategy specifically comprises the following steps: the first bypass proportional valve 18 is adjusted to the full open position while the second bypass proportional valve 20 is adjusted to be fully closed to increase the intake air temperature.
In summary, the engine thermal management of the present inventionThe system has the following beneficial effects: (1) the air inlet temperature of partial load can be improved, the air-fuel ratio is reduced to a certain extent, the air inlet flow is reduced, the NOx ratio emission is reduced, and the oil consumption of the partial load is reduced. (2) The average bed temperature of the SCR catalyst can be improved to a great extent, particularly for vehicles needing WHTC authentication, the bed temperature of the catalyst is an important factor of the efficient reaction of the SCR catalyst, and the means for improving the exhaust temperature of the engine thermal management system provided by the invention does not sacrifice the oil consumption, namely, the oil consumption is better while the exhaust is easier to pass through. (3) The temperature and the efficiency of the SCR catalyst are improved, and meanwhile, the urea injection amount, the ammonia leakage and the risk of urea crystallization can be reduced; the NO of the engine can be increased properlyXThe original emission value improves the fuel economy of the engine.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims (5)

1. A control method of an engine thermal management system, comprising the steps of:
(1) defining the engine to be in an idling working condition, a back-dragging working condition, a cold start working condition and other working conditions except the working conditions;
(2) firstly, judging whether the engine is in a working state, enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is in the working state, and not enabling the control functions of the first bypass proportional valve and the second bypass proportional valve if the engine is not in the working state; when the engine is in a working state, judging which working condition of the idling working condition, the dragging-backward working condition, the cold start working condition or other working conditions except the working condition is the engine;
(3) determining action control strategies of the first bypass proportional valve and the second bypass proportional valve according to the idling working condition, the dragging working condition or the cold starting working condition of the engine, or determining a primary open-loop control strategy based on boundary conditions and a secondary closed-loop control strategy based on delta T according to other working conditions except the working condition of the engine, wherein the delta T is T according to a formulab-TtIs calculated to obtain, wherein, TbIs the average bed temperature, T, of the SCR catalysttIs the target SCR catalyst bed temperature; and
(4) adjusting the position of the first bypass proportional valve and the opening of the second bypass proportional valve according to the action control strategy, the primary open-loop control strategy or the secondary closed-loop control strategy in the step (3) to realize temperature control of the engine thermal management system;
wherein the engine thermal management system comprises: engine intake pipe, engine exhaust pipe, engine cylinder body, engine air inlet manifold, intercooler, booster compressor and aftertreatment system, engine thermal management system still includes: the two ends of the bypass pipeline for controlling the air inlet temperature are respectively connected with an intercooler inlet and an intercooler outlet and are connected with the intercooler in parallel, a first bypass proportional valve is arranged on the bypass pipeline for controlling the air inlet temperature, and the bypass of the flow of the intercooling forward air with different flows can be realized by adjusting the position proportion of the first bypass proportional valve; the two ends of the bypass pipeline are respectively connected with the inlet and the outlet of the compressor and connected with the compressor of the supercharger in parallel, a second bypass proportional valve is arranged on the bypass pipeline for controlling the air inflow, and the air inflow requirements of different working conditions are realized by adjusting the opening degree of the second bypass proportional valve; the temperature sensor is arranged on a pipeline of the engine air inlet main pipe and used for measuring the air inlet temperature entering the engine air inlet main pipe, and the ECU can acquire the measured value of the air inlet temperature;
and wherein the first-stage open-loop control strategy mainly takes the intake air temperature and the air-fuel ratio of an intake manifold as boundary conditions; the two-stage closed-loop control strategy is used for realizing the control of the exhaust temperature of the engine heat management system by comparing the average bed temperature of the SCR catalyst with the target bed temperature of the SCR catalyst, comparing the actual air-fuel ratio with the target air-fuel ratio and comparing the measured value of the air inlet temperature of the air inlet main pipe with the maximum air inlet temperature limit value.
2. The control method according to claim 1, characterized in that when the engine is in the idle condition or the tow-back condition, the control strategy is specifically: adjusting the first bypass proportional valve to be in a full-open position, wherein only part of gas before intercooling flows through the intercooler, and the other part of gas directly flows to the engine intake manifold to improve the exhaust temperature; and adjusting the second bypass proportional valve to be fully opened, and bypassing part of the engine to intake air so as to reduce the cooling of the SCR catalyst by low-temperature gas.
3. The control method according to claim 2, wherein when the engine is in other operating conditions than the above-mentioned operating condition, the boundary condition-based primary open-loop control strategy and the Δ T-based secondary closed-loop control strategy are specifically:
(1) when the delta T is less than 0, the delta lambda is greater than 0 and the measured value of the air inlet temperature is less than the maximum air inlet temperature limit value, the first bypass proportional valve is adjusted to be close to full opening, so that the air at the outlet of the air compressor directly flows to an air inlet main pipe of the engine to improve the air inlet temperature; meanwhile, the second bypass proportional valve is partially opened or fully opened so as to reduce the flow of after-intercooling air and improve the exhaust temperature;
(2) when Δ T <0, but Δ λ <0 or the measured value of the intake air temperature > the maximum intake air temperature limit, then adjusting the first bypass proportional valve to a partially closed or fully closed position to allow the compressor outlet air to be cooled by the intercooler; meanwhile, the second bypass proportional valve is adjusted to be fully or partially closed so as to ensure sufficient air inflow;
(3) when the delta T is larger than or equal to 0, adjusting the first bypass proportional valve and the second bypass proportional valve to be closed completely so as to maintain a normal air inlet mode;
wherein Δ T is according to the formula Δ T ═ Tb-TtIs calculated to obtain, wherein, TbIs the average bed temperature, T, of the SCR catalysttIs the target SCR catalyst bed temperature; Δ λ is according to the formula Δ λ ═ λr-λtIs calculated to obtain, whereinrTo actual air-fuel ratio, λtIs the target air-fuel ratio.
4. The control method according to claim 1, characterized in that when the engine is in a cold start condition, the control strategy is embodied as: and adjusting the first bypass proportional valve to be in a full-open position, and simultaneously adjusting the second bypass proportional valve to be fully closed so as to increase the intake air temperature.
5. The control method of claim 4, wherein the maximum intake air temperature limit is 50 ℃.
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