CN113374564B - Automobile exhaust after-treatment method - Google Patents

Automobile exhaust after-treatment method Download PDF

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CN113374564B
CN113374564B CN202110876190.3A CN202110876190A CN113374564B CN 113374564 B CN113374564 B CN 113374564B CN 202110876190 A CN202110876190 A CN 202110876190A CN 113374564 B CN113374564 B CN 113374564B
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temperature
dpf
scr
air inlet
pipe
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CN113374564A (en
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刘海峰
张晓腾
王灿
尧命发
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Tianjin University
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Tianjin University
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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
    • 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
    • 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
    • F01N13/0093—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 the purifying devices are of the same type
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
    • F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
    • F01N3/0253—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust adding fuel to exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • 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
    • F01N3/2013—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means
    • 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
    • F01N3/2046—Periodically cooling catalytic reactors
    • 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]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2892—Exhaust flow directors or the like, e.g. upstream of catalytic device
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • 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
    • F01N2250/00—Combinations of different methods of purification
    • F01N2250/02—Combinations of different methods of purification filtering and catalytic conversion
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/10—Carbon or carbon oxides
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/12—Hydrocarbons
    • 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
    • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
    • F01N2570/14—Nitrogen oxides
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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

Abstract

The invention discloses an automobile exhaust aftertreatment method, which comprises the steps of firstly adjusting a first cooler to enable a first DOC to be at the optimal working temperature, controlling the opening and closing of a bypass leading to a second DOC according to the concentrations of HC and CO behind the first DOC to ensure that the emission of HC and CO is lower than the limit value, then adjusting a fuel injection unit according to the temperature difference and the pressure difference between the front and the back of a DPF, enabling the inlet temperature of the DPF to reach the preset ignition temperature (during regeneration) or the preset working temperature (during non-regeneration) by the second cooler and the first heater, finally adjusting a third cooler and the second heater to enable the first SCR to be at the optimal working temperature, controlling the opening and closing of the bypass passing through the second SCR according to the concentration of NOx behind the first SCR to ensure that the emission of NOx is lower than the limit value, and additionally arranging a fan to improve the problem that the exhaust back pressure is obviously increased. The invention can effectively carry out high-temperature protection on each part, has long service life of the system, high purification efficiency and stable performance, and can be applied to automobile post-treatment systems with 6-stage or even higher emission requirements in China.

Description

Automobile exhaust after-treatment method
Technical Field
The invention relates to the field of vehicle exhaust emission post-treatment, in particular to an automobile exhaust post-treatment method.
Background
The automobile is used as a necessary vehicle for people to go out, and the keeping quantity of the automobile is increased year by year. But it generates more Hydrocarbon (HC), carbon monoxide (CO), soot (PM) and nitrogen oxide (NOx) emissions during operation, causing greater pollution to the environment. At present, an automobile aftertreatment system is generally composed of an oxidation type catalytic converter DOC, a particle trap DPF and a selective catalytic reducer SCR. DOC is the oxidation of CO and HC in automobile exhaust to pollution-free carbon dioxide (CO) by oxygen under the action of catalyst2) And water (H)2O). The DPF utilizes a filter body to capture the tail of the automobileA device for PM particulate matter in gas. SCR is the use of ammonia (NH) produced by the hydrolysis of urea3) Reducing nitrogen oxides (NOx) in automobile exhaust into nitrogen (N) under the action of catalyst2) The apparatus of (1). The DPF, along with its use, deposits PM particles, causing a dense ash layer to form on the walls and ends of the inlet passages of the filter, deteriorating the performance of the DPF and the engine. Regeneration of a DPF is typically facilitated by injecting unburned fuel in the cylinder of the engine or injecting unburned fuel in the tail pipe after the engine is later than the main combustion injection period to oxidize the unburned fuel with the DOC to generate heat to increase the inlet temperature of the DPF for burnout of the ash layer. However, the actual operation condition of the automobile is complex, if the operation load is low, the state of low exhaust temperature is continuous, in order to promote the DPF temperature to reach the combustion temperature of an ash layer, a large amount of unburned fuel is injected into the DOC upstream, the upstream side of the DOC is adhered by soluble deposits, soot and the like of the unburned fuel at the moment, the DOC is blocked, the exhaust back pressure is increased, the oil consumption is deteriorated, meanwhile, a large amount of unburned fuel leaks through the DOC to enter the DPF to be oxidized and emit heat, and the DPF is seriously burnt and damaged. In addition, the efficiency of the catalyst in DOC and SCR can be optimal only within a certain exhaust temperature range, the efficiency of the catalyst is not high when the exhaust temperature is low, the automobile is under a high load condition, and the catalyst is easy to sinter, deform in structure and even fail when the exhaust temperature is high. Compared with the national standard 5, the current national standard 6 basically reduces the emission indexes of various pollutants by more than 50%, and in order to meet the increasingly strict emission standard in the future, single-stage DOC and single-stage SCR cannot meet the requirements, so two-stage treatment needs to be added, but the obvious increase of the back pressure caused by the two-stage treatment is a big problem restricting the development of the DOC and SCR.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the automobile exhaust aftertreatment method which can effectively prolong the service life of each part and can automatically regulate the temperature according to different working conditions of an automobile so as to ensure that DOC, DPF and SCR are all at the optimal operating temperature and effectively improve the purification efficiency of an aftertreatment system.
In order to achieve the purpose, the invention provides the following technical scheme:
the invention relates to an automobile exhaust after-treatment method, which comprises the following steps:
the method comprises the following steps of firstly, improving the existing automobile tail gas aftertreatment system, wherein the improved automobile tail gas aftertreatment system comprises a first DOC, a second DOC, a DPF, a first SCR and a second SCR, an air inlet of the first DOC is fixedly connected with an exhaust pipe of an engine, the exhaust pipe close to one side of the engine is connected with an air inlet manifold of the engine through a solenoid valve, the exhaust pipe close to the air inlet of the first DOC is connected with a first cooler, a first temperature sensor and a fuel injection unit, and the first temperature sensor and the fuel injection unit are both arranged on the inner wall of the exhaust pipe close to the air inlet of the first DOC;
the exhaust port of the first DOC is sequentially connected with a rotatable first reversing valve, a rotatable second reversing valve, a rotatable first fan, a rotatable first heater, a rotatable second cooler and an air inlet of the DPF through a first connecting pipe, an HC sensor and a CO sensor are arranged on the inner wall of the first connecting pipe close to the exhaust port of the first DOC, a second temperature sensor and a first pressure sensor are respectively arranged on the inner wall of the air inlet of the DPF body, and a third temperature sensor and a second pressure sensor are respectively arranged on the inner wall of the exhaust port of the DPF body;
an air inlet of the second DOC is connected with the first connecting pipe through a first bypass air inlet pipe, an air outlet of the second DOC is connected with the first connecting pipe through a first bypass exhaust pipe, the first reversing valve can enable the first bypass air inlet pipe to be communicated or disconnected with the first connecting pipe through rotation, and the second reversing valve can enable the first bypass exhaust pipe to be communicated or disconnected with the first connecting pipe through rotation;
the air outlet of the DPF is sequentially connected with a second heater, a third cooler and an air inlet of a first SCR through a second connecting pipe, a fourth temperature sensor and a first urea injection unit are respectively arranged on the inner wall of the second connecting pipe close to the air inlet of the first SCR, the air outlet of the first SCR is sequentially connected with a rotatable third reversing valve, a fourth reversing valve and ambient air through a tail gas pipe, a NOx sensor is arranged on the inner wall of the tail gas pipe close to the air outlet of the first SCR, the air inlet of the second SCR is sequentially connected with the fourth cooler, the third heater, a second fan and the front end of the tail gas pipe close to the air outlet of the first SCR through a second bypass air inlet pipe, the air outlet of the second SCR is communicated with the tail end of the tail gas pipe communicated with the ambient air through a second bypass exhaust pipe, and a fifth temperature sensor is respectively arranged on the inner wall of the second air inlet pipe between the fourth cooler and the second SCR, The third reversing valve can enable the second bypass air inlet pipe to be communicated with or disconnected from the exhaust pipe through rotation, and the fourth reversing valve can enable the second bypass exhaust pipe to be communicated with or disconnected from the exhaust pipe through rotation;
the signal output ends of the first temperature sensor, the HC sensor, the CO sensor, the second temperature sensor, the first pressure sensor, the third temperature sensor, the second pressure sensor, the fourth temperature sensor, the NOx sensor, the fifth temperature sensor and the third pressure sensor are all connected with the signal input end of the ECU control unit through control lines, and the signal output end of the ECU control unit is respectively connected with the signal input ends of the first cooler, the fuel injection unit, the first reversing valve, the second reversing valve, the first fan, the first heater, the second cooler, the second heater, the third cooler, the first urea injection unit, the third reversing valve, the fourth reversing valve, the second fan, the third heater, the fourth cooler, the second urea injection unit and the electromagnetic valve through control lines;
step two, the ECU control unit obtains the exhaust temperature T discharged by the engine at the first DOC air inlet in real time through the first temperature sensor1If T is1Lower limit of catalyst failure temperature in first DOC or more
Figure BDA0003190402260000031
The ECU control unit opens the electromagnetic valve to enable part of exhaust gas in the exhaust pipe to flow through an engine intake manifold and enter an engine cylinder again to do work, and meanwhile, the ECU control unit starts the first cooler to further enable the exhaust gas temperature in the exhaust pipe to be reduced to a first DOC preset working temperature TDOC(ii) a If T1Less than catalyst failure in the first DOCLower limit of temperature
Figure BDA0003190402260000032
The system is not adjusted;
step three, the ECU control unit obtains the HC concentration and the CO concentration at the exhaust port of the first DOC in real time through the HC sensor and the CO sensor, and if the HC concentration exceeds the HC emission maximum limit value, HCmaxOr the CO concentration exceeds the maximum CO emission limit COmaxThe first reversing valve rotates by a certain angle, so that the exhaust gas of the engine can only enter the first bypass air inlet pipe through the exhaust pipe and is further purified by the second DOC, and meanwhile, the exhaust gas further purified by the second DOC enters the first connecting pipe through the first bypass exhaust pipe; HC if neither HC nor CO concentration exceeds the HC emission maximum limitmaxAnd maximum limit of CO emission COmaxWhen the first reversing valve rotates by a certain angle, the passage from the exhaust pipe to the first bypass air inlet pipe is closed, and meanwhile, the passage from the first connecting pipe to the first bypass exhaust pipe is closed by a certain angle of rotation of the second reversing valve, so that the exhaust gas only flows through the first connecting pipe;
step four, judging whether to regenerate the DPF, specifically comprising the following steps: the ECU acquires the temperature T at the air inlet of the DPF in real time through the second temperature sensor and the first pressure sensorinAnd PinAnd the temperature T at the exhaust port of the DPF is acquired in real time through a third temperature sensor and a second pressure sensoroutAnd PoutSubtracting the temperature value of the second temperature sensor from the temperature value of the third temperature sensor to obtain a DPF temperature change value delta TDPFAnd subtracting the pressure value of the first pressure sensor from the pressure value of the second pressure sensor to obtain a DPF pressure variation value delta PDPFThen, the following judgment is made:
step 41, if the temperature variation value Delta T of the DPFDPFAnd the pressure variation value DeltaPDPFAny one group exceeding the temperature change threshold
Figure BDA0003190402260000041
And a pressure variation threshold
Figure BDA0003190402260000042
Then, the DPF is regenerated, specifically: when the temperature T at the DPF air inlet obtained by the second temperature sensorinThe DPF regeneration temperature is exceeded, and the ECU controls the second cooler to work to enable the temperature T at the air inlet of the DPF to be exceededinCooling to the preset ignition temperature Tcom of the DPF; when the temperature T at the DPF air inlet obtained by the second temperature sensorinLower than the lower limit of the DPF operating temperature
Figure BDA0003190402260000043
At the moment, the ECU drives the fuel injection unit to work, and adjusts the fuel injection quantity of the fuel injection unit to be the maximum safe fuel quantity qmaxMeanwhile, the ECU drives the first heater to work so as to further heat the exhaust gas at the DPF air inlet to ensure that the temperature T of the DPF air inlet is enabledinReach the preset light-off temperature T of DPFcom(ii) a When DPF operating temperature lower limit
Figure BDA0003190402260000044
Temperature T of DPF air inlet obtained by the second temperature sensor is less than or equal toinWhen the regeneration temperature is less than or equal to the regeneration temperature, the ECU controls the unit to perform regeneration according to the temperature T at the air inlet of the DPFinAnd DPF a predetermined light-off temperature TcomAutomatically adjusting the fuel injection quantity of the fuel injection unit to enable the temperature T of the DPF air inletinReach the preset light-off temperature T of DPFcom；
Step 42, if the temperature variation value Delta T of the DPF is detectedDPFAnd the pressure variation value DeltaPDPFDo not exceed the temperature variation threshold
Figure BDA0003190402260000045
And a pressure variation threshold
Figure BDA0003190402260000046
The regeneration of the DPF is not performed, and the temperature T at the air inlet of the DPF obtained by the ECU control unit at this timeinIf it is higher than the preset working temperature T of DPFgzThen driving the second cooler to work to make the DPF inlet temperature TinCooling to DPF preset working temperature Tgz(ii) a If DPF inlet temperature TinLower than the preset working temperature T of DPFgzThen driving the first heater to work to make the DPF inlet temperature TinHeating to DPF preset working temperature Tgz(ii) a If DPF inlet temperature TinEqual to the preset operating temperature T of the DPFgzThe system is not adjusted;
step five, the ECU control unit obtains the pressure P at the DPF air inlet according to the first pressure sensorinJudging whether to carry out system adjustment, specifically: if pressure P at DPF inletinLess than the lower limit of DPF working pressure
Figure BDA0003190402260000047
The ECU starts the first fan to make the pressure P at the DPF air inletinBoost to DPF preset operating pressure Pgz; if pressure P at DPF inletinNot lower than the lower limit of the DPF working pressure
Figure BDA0003190402260000048
The system is not adjusted;
step six, the ECU control unit automatically adjusts the urea injection quantity of the first urea injection unit and simultaneously obtains a temperature value T 'at the air inlet of the first SCR according to the fourth temperature sensor'inAdjusting the inlet air temperature of the first SCR to the optimum working temperature T of the first SCRSCRThe method specifically comprises the following steps: if the ECU control unit obtains the first SCR air inlet temperature T'inIs higher than the preset working temperature T of the first SCRSCRAnd driving the third cooler to work to enable the first SCR inlet temperature T'inCooling to the preset working temperature T of the first SCRSCR(ii) a If first SCR air inlet temperature T'inLower than the preset working temperature T of the first SCRSCRAnd driving a second heater to work to enable the first SCR inlet temperature T'inHeating to the preset working temperature T of the first SCRSCR(ii) a If first SCR air inlet temperature T'inEqual to the preset working temperature T of the first SCRSCRThe system is not adjusted;
step seven, the ECU obtains the concentration of NOx at the exhaust port of the first SCR in real time through the NOx sensor, if so, the ECU controls the SCR to work in a way of detecting the concentration of NOx at the exhaust port of the first SCRNOx concentration exceeding NOx emission maximum limit NOxmaxWhen the third reversing valve rotates by a certain angle, the exhaust gas of the first SCR can only enter the second bypass air inlet pipe through the exhaust pipe, the exhaust gas is further purified through the second SCR, and the ECU acquires the pressure P at the air inlet of the second SCR through the third pressure sensor3If P is3Lower than the second SCR operating pressure lower limit
Figure BDA0003190402260000051
The ECU starts the second fan to make the pressure P at the air inlet of the second SCR3Boosting to a second SCR preset working pressure PSCR(ii) a If the pressure P at the second SCR inlet3Not lower than the lower limit of the working pressure of the second SCR
Figure BDA0003190402260000052
The second fan is not started, and meanwhile, the ECU control unit automatically adjusts the urea injection quantity of the second urea injection unit and obtains a temperature value T' at the air inlet of the second SCR according to the fifth temperature sensor "inAdjusting the temperature value at the air inlet of the second SCR to the optimal SCR working temperature T by adopting the method in the step sixSCR(ii) a The ECU control unit controls the rotation angle of the fourth reversing valve to enable the exhaust purified by the second SCR to enter the tail gas pipe from the second bypass exhaust pipe and then to be exhausted to the atmosphere; if the NOx concentration does not exceed the maximum NOx emission limit NOxmaxAnd if the third reversing valve rotates by a certain angle, closing the passage from the tail gas pipe to the second bypass gas inlet pipe, and simultaneously, closing the passage from the tail gas pipe to the second bypass gas outlet pipe by a certain angle of rotation of the fourth reversing valve, wherein the exhaust gas is purified by the first SCR and then directly discharged to the atmosphere by the tail gas pipe.
The invention has the following beneficial effects:
1. according to the invention, the first cooler, the second cooler, the third cooler, the fourth cooler, the first heater, the second heater and the third heater are arranged, so that the DOC, the DPF and the SCR in the tail gas aftertreatment system of the automobile under any working condition can be effectively protected at high temperature, the phenomena of sintering, volatilization, structural deformation and even failure of the catalyst and the like can be prevented, the service lives of all parts are effectively prolonged, and meanwhile, the system can automatically adjust the temperature according to different working conditions of the automobile so as to ensure that the DOC, the DPF and the SCR are all at the optimal operating temperature, so that the purification efficiency of the aftertreatment system is effectively improved.
2. The first cooler, the second cooler, the third cooler, the fourth cooler, the first heater, the second heater and the third heater are uniformly arranged on the outer wall of the pipeline, the air flow speed in the pipeline cannot be influenced, and the exhaust temperature is controlled while extra resistance to air flow is avoided.
3. According to the invention, the unburned fuel oil injected by the fuel oil injection unit is cooperated with the first heater, so that the DPF can be ensured to reach the regeneration temperature when the DPF is regenerated, and the phenomena that a large amount of unburned fuel oil is injected into the upstream of the DOC, the upstream side of the DOC is adhered by soluble deposits, soot and the like of the unburned fuel oil at the moment, the DOC is blocked, the exhaust back pressure is increased, and the oil consumption is deteriorated can be effectively prevented from being caused in order to promote the DPF temperature to reach the combustion temperature of an ash layer under the condition of too low exhaust temperature.
4. According to the invention, the plurality of baffling sheets are circumferentially arranged at the DOC and SCR air inlets, so that reactants are fully mixed before reaction, the residence time of the reactants in the catalyst is prolonged, and the DOC and SCR purification efficiency is improved.
5. According to the invention, by arranging the first bypass passage and the second bypass passage, when the first-stage DOC and the first-stage SCR cannot meet the emission purification requirements, the exhaust gas can be further purified through the second DOC and the second SCR through the bypass passage, so that the device can be applied to automobile aftertreatment systems with national 6-stage or even higher emission requirements, can also be used for solving the problem of serious deterioration of emission when an engine fails, and is additionally provided with the first fan and the second fan to solve the problem of remarkable increase of exhaust back pressure caused by the increase of exhaust gas flowing through parts.
Drawings
FIG. 1 is a front cross-sectional view of the overall structure of a system employed in an automobile exhaust aftertreatment method of the invention;
FIG. 2 is an enlarged view of the structure of FIG. 1 at A according to the present invention;
FIG. 3 is a functional block diagram of an automotive exhaust aftertreatment method of the present invention;
FIG. 4 is a system overview flow chart of a method for aftertreatment of automotive exhaust in accordance with the present invention;
the reference numbers in the figures are: 1. an engine intake manifold; 2. an engine; 3. an exhaust pipe; 4. a first cooler; 5. a first temperature sensor; 6. a fuel injection unit; 7. a first DOC; 8. an HC sensor; 9. a CO sensor; 10. a first direction changing valve; 11. a first connecting pipe; 12. the first bypass air inlet pipe; 13. a second DOC; 14. a first bypass exhaust pipe; 15. a second directional control valve; 16. a first fan; 17. a first heater; 18. a second cooler; 19. a second temperature sensor; 20. a first pressure sensor; 21. a DPF; 22. a third temperature sensor; 23. a second pressure sensor; 24. a second connecting pipe; 25. a second heater; 26. a third cooler; 27. a fourth temperature sensor; 28. a first urea injection unit; 29. a first SCR; 30. a NOx sensor; 31. a third directional control valve; 32. a tail gas pipe; 33. a fourth directional control valve; 34. a second fan; 35. a second bypass air inlet pipe; 36. a third heater; 37. a fourth cooler; 38. a fifth temperature sensor; 39. a third pressure sensor; 40. a second urea injection unit; 41. a second SCR; 42. a second bypass exhaust pipe; 43. an electromagnetic valve; 44. an ECU control unit; 45. a baffling sheet.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The conventional automobile exhaust aftertreatment system usually adopts the cooperation of the first DOC 7+ DPF 21+ and the first SCR 29 to purify automobile exhaust, and no measures are taken for performing high-temperature protection on the components and improving the efficiency of an internal catalyst in the use process, so that the aftertreatment efficiency is low, and the catalyst is easy to lose efficacy at high temperature.
As shown in fig. 1 to 4, the present invention provides a technical solution:
the invention relates to an automobile exhaust after-treatment method, which comprises the following steps:
step one, improve current automobile exhaust aftertreatment system, improved automobile exhaust aftertreatment system includes first DOC 7, second DOC 13, DPF 21, first SCR 29 and second SCR 41, the air inlet of first DOC 7 and 3 fixed connection of blast pipe of engine 2, the blast pipe 3 that is close to engine 2 one side links to each other with the air intake manifold 1 of engine 2 through solenoid valve 43, is connected with first cooler 4 on the blast pipe 3 that is close to first DOC 7 air inlet, first temperature sensor 5 and fuel injection unit 6 all set up on the inner wall of the blast pipe 3 that is close to first DOC 7 air inlet.
The exhaust port of the first DOC 7 is sequentially connected with a rotatable first reversing valve 10, a second reversing valve 15, a first fan 16, a first heater 17, a second cooler 18 and an air inlet of the DPF 21 through a first connecting pipe 11, an HC sensor 8 and a CO sensor 9 are arranged on the inner wall of the first connecting pipe 11 close to the exhaust port of the first DOC 7, a second temperature sensor 19 and a first pressure sensor 20 are respectively arranged on the inner wall of the air inlet of the DPF 21 body, and a third temperature sensor 22 and a second pressure sensor 23 are respectively arranged on the inner wall of the exhaust port of the DPF 21 body.
The air inlet of second DOC 13 is connected with first connecting pipe 11 through first bypass intake pipe 12, and the gas vent of second DOC 13 is connected with first connecting pipe 11 through first bypass blast pipe 14, first switching-over valve 10 can make first bypass intake pipe 12 and first connecting pipe 11 intercommunication or disconnection through the rotation, second switching-over valve 15 can make first bypass blast pipe 14 and first connecting pipe 11 intercommunication or disconnection through the rotation.
An outlet of the DPF 21 is sequentially connected to a second heater 25, a third cooler 26, and an inlet of the first SCR 29 through a second connection pipe 24, and a fourth temperature sensor 27 and a first urea injection unit 28 are respectively provided on an inner wall of the second connection pipe 24 adjacent to the inlet of the first SCR 29. An exhaust port of the first SCR 29 is connected to a rotatable third directional valve 31, a fourth directional valve 33, and ambient air in this order through an exhaust pipe 32. The inner wall of the exhaust pipe 32 close to the exhaust port of the first SCR 29 is provided with a NOx sensor 30, the air inlet of the second SCR 41 is sequentially connected with a fourth cooler 37, a third heater 36, a second fan 34 and the front end of the exhaust pipe 32 close to the exhaust port of the first SCR 29 through a second bypass air inlet pipe 35, the exhaust port of the second SCR 41 is communicated with the tail end of the exhaust pipe 32 communicated with ambient air through a second bypass exhaust pipe 42, and the inner wall of the second bypass air inlet pipe 35 between the fourth cooler 37 and the air inlet of the second SCR 41 is respectively provided with a fifth temperature sensor 38, a third pressure sensor 39 and a second urea injection unit 40. The third direction valve 31 can make the second bypass inlet pipe 35 and the exhaust pipe 32 connected or disconnected by rotating, and the fourth direction valve 33 can make the second bypass exhaust pipe 42 and the exhaust pipe 32 connected or disconnected by rotating.
Preferably, the first cooler 4, the second cooler 18 and the third cooler 26 are circular sleeves sleeved on the outer wall of the pipeline, cooling water or cooling media are introduced into the circular sleeves, the first heater 17, the second heater 25 and the third heater 36 are square hollow resistance boxes sleeved on the outer wall of the pipeline, a large number of resistance wires are arranged in the square hollow resistance boxes, the arrangement of the coolers and the heaters cannot influence the air flow velocity in the pipeline, and the exhaust temperature is controlled while no extra resistance is caused to the air flow.
Preferably, the first fan 16 and the second fan 34 are connected with the pipeline in a welding mode, and sealing rings are arranged around the first fan 16 and the second fan 34 to prevent gas leakage, blades of the first fan 16 and the second fan 34 are small enough, the total area of the blades is controlled not to exceed one third of the cross section area of the pipeline, and the number of the blades is only 6, so that the resistance of the blades to airflow flowing when the fans do not work is effectively reduced.
Preferably, a plurality of baffle plates are arranged on the first DOC 7, the second DOC 13, the first SCR 29 and the second SCR 41 close to the air inlet in a welding manner along the circumferential direction, taking the air inlet of the first DOC 7 as an example, as shown in fig. 2, the angle between the baffle plate 45 and the horizontal is 15 degrees, and the baffle plates are arranged to fully mix reactants before the reactants react and increase the residence time in the catalyst, so as to improve the purification efficiency of the DOC and the SCR.
The signal output ends of the first temperature sensor 5, the HC sensor 8, the CO sensor 9, the second temperature sensor 19, the first pressure sensor 20, the third temperature sensor 22, the second pressure sensor 23, the fourth temperature sensor 27, the NOx sensor 30, the fifth temperature sensor 38 and the third pressure sensor 39 are all connected with the signal input end of the ECU control unit 44 through control lines, and the signal output end of the ECU control unit 44 is respectively connected with the signal input ends of the first cooler 4, the fuel injection unit 6, the first reversing valve 10, the second reversing valve 15, the first fan 16, the first heater 17, the second cooler 18, the second heater 25, the third cooler 26, the first urea injection unit 28, the third reversing valve 31, the fourth reversing valve 33, the second fan 34, the third heater 36, the fourth cooler 37, the second urea injection unit 40 and the electromagnetic valve 43 through control lines.
The parts which are not involved in the automobile exhaust aftertreatment system are the same as or can be realized by adopting the prior art.
Step two, the ECU control unit 44 obtains the temperature T of the exhaust gas discharged by the engine 2 at the air inlet of the first DOC 7 in real time through the first temperature sensor 51If T is1Lower limit of catalyst failure temperature in the first DOC 7 or more
Figure BDA0003190402260000091
The ECU control unit 44 opens the electromagnetic valve 43 to make part of the exhaust gas in the exhaust pipe 3 flow through the engine intake manifold 1 and re-enter the cylinder of the engine 2 to do work, because the fuel in the exhaust gas has poor work-doing capability, the combustion temperature in the cylinder can be effectively reduced by using part of the exhaust gas to do work again, and then the exhaust gas temperature is reduced, and simultaneously the ECU control unit controlsUnit 44 activates first cooler 4 further reducing the temperature of the exhaust gases in exhaust pipe 3 to a preset operating temperature T of first DOC 7DOC(ii) a If T1Less than the lower limit of the catalyst failure temperature in the first DOC 7
Figure BDA0003190402260000092
The system does not adjust.
Step three, the ECU control unit 44 obtains the HC concentration and the CO concentration at the exhaust port of the first DOC 7 in real time through the HC sensor 8 and the CO sensor 9, and if the HC concentration exceeds the HC emission maximum limit valuemaxOr the CO concentration exceeds the maximum CO emission limit COmaxIf the rotation angle of the first reversing valve 10 is larger than the rotation angle of the second reversing valve 15, the exhaust gas of the engine 2 can only enter the first bypass intake pipe 12 from the exhaust pipe 3, and is further purified by the second DOC 13, and meanwhile, the exhaust gas further purified by the second DOC 13 enters the first connecting pipe 11 from the first bypass exhaust pipe 14; HC if neither HC nor CO concentration exceeds the HC emission maximum limitmaxAnd maximum limit of CO emission COmaxThe first direction change valve 10 is rotated to close the passage from the exhaust pipe 3 to the first bypass intake pipe 12, while the second direction change valve 15 is rotated to close the passage from the first connection pipe 11 to the first bypass exhaust pipe 14, so that the exhaust gas flows only through the first connection pipe 11.
Step four, judging whether to regenerate the DPF 21, specifically: the ECU control unit 44 acquires the temperature T at the air inlet of the DPF 21 in real time through the second temperature sensor 19 and the first pressure sensor 20inAnd PinAnd the temperature T at the exhaust port of the DPF 21 is acquired in real time by the third temperature sensor 22 and the second pressure sensor 23outAnd PoutSubtracting the temperature value of the second temperature sensor 19 from the temperature value of the third temperature sensor 22 to obtain the temperature variation value Delta T of the DPF 21DPFAnd subtracting the pressure value of the first pressure sensor 20 from the pressure value of the second pressure sensor 23 to obtain the pressure variation value DeltaP of the DPF 21DPFThen, the following judgment is made:
step 41, if the temperature variation value Delta T of the DPF 21DPFAnd the pressure variation value DeltaPDPFAny one groupExceeding a temperature change threshold
Figure BDA0003190402260000101
And a pressure variation threshold
Figure BDA0003190402260000102
The DPF 21 is regenerated, specifically: when the temperature Tin at the air inlet of the DPF 21 obtained by the second temperature sensor 19 has exceeded the DPF regeneration temperature, in order to avoid thermal damage to the DPF 21, the ECU control unit 44 controls the second cooler 18 to operate to cool the temperature Tin at the air inlet of the DPF 21 to the DPF preset light-off temperature Tcom; when the temperature Tin at the air inlet of the DPF 21 obtained by the second temperature sensor 19 is lower than the lower limit of the operating temperature of the DPF 21
Figure BDA0003190402260000103
At this time, the ECU control unit 44 drives the fuel injection unit 6 to operate, but at this time, because the exhaust temperature at the air inlet of the DPF 21 is too low, when the fuel injection unit 6 injects a large amount of fuel, the upstream side of the first DOC 7 is adhered by soluble deposits of unburned fuel, soot and the like, the first DOC 7 is blocked, the exhaust back pressure is increased, the fuel consumption is deteriorated, and simultaneously, a large amount of unburned fuel leaks through the first DOC 7 to enter the DPF 21 to be oxidized and released heat, and the DPF 21 is burned and damaged seriously, so that the fuel injection amount of the fuel injection unit 6 is adjusted to be the maximum safe fuel amount q at this timemax(the value is set according to the principle of avoiding the DOC from being blocked, namely the maximum safe fuel quantity is the maximum fuel quantity which can be injected to ensure that the DOC does not have the blocking phenomenon and can be obtained from the empirical value of the test data of the previous engine), and meanwhile, the ECU control unit 44 drives the first heater 17 to work so as to further heat the exhaust gas at the air inlet of the DPF 21 and further raise the temperature T of the air inlet of the DPF 21inReach the preset light-off temperature T of DPFcom(ii) a When the lower limit of the working temperature of DPF 21
Figure BDA0003190402260000104
Temperature T at the air inlet of the DPF 21 obtained by the second temperature sensor 19 is not more thaninWhen the temperature is lower than or equal to the regeneration temperature, the ECU control unit 44 controls the temperature T at the air inlet of the DPF 21inAnd DPF a predetermined light-off temperature TcomThe difference value of the temperature difference value is used for automatically adjusting the fuel injection quantity of the fuel injection unit 6 (the adjusting principle is that the ECU calculates the total heat quantity required for increasing the exhaust temperature from the existing temperature to the target temperature according to the difference value of the existing temperature and the target temperature, then the heat quantity which can be released by unit fuel is calculated according to the heat value of the injected fuel and the reaction efficiency of DOC, the total heat quantity is divided by the heat quantity which can be released by the unit fuel to be equal to the fuel injection quantity, and related calculating programs are widely integrated on the ECU control unit), so that the temperature T at the air inlet of the DPF 21 is enabled to be TinReach the preset light-off temperature T of DPFcom；
Step 42, if the temperature variation value Delta T of the DPF 21DPFAnd the pressure variation value DeltaPDPFDo not exceed the temperature variation threshold
Figure BDA0003190402260000111
And a pressure variation threshold
Figure BDA0003190402260000112
The regeneration of the DPF 21 is not performed and the temperature T at the air inlet of the DPF 21 obtained by the ECU control unit 44 at this timeinIf it is higher than the preset working temperature T of DPFgzThen the second cooler 18 is driven to work to make the DPF 21 inlet temperature TinCooling to DPF preset working temperature Tgz(ii) a If DPF 21 inlet temperature TinLower than the preset working temperature T of DPFgzThen, the first heater 17 is driven to operate to make the DPF 21 inlet temperature TinHeating to DPF preset working temperature Tgz(ii) a If DPF 21 inlet temperature TinEqual to the preset operating temperature T of the DPFgzThe system does not adjust.
Step five, the ECU control unit 44 obtains the pressure P at the air inlet of the DPF 21 according to the first pressure sensor 20inJudging whether to carry out system adjustment, specifically: if pressure P at the air inlet of DPF 21inLess than the lower limit of the working pressure of DPF 21
Figure BDA0003190402260000113
The ECU control unit 44 activates the first fan 16 to make the pressure at the air inlet of the DPF 21PinPressurizing to the preset working pressure P of DPF 21gz(ii) a If pressure P at the air inlet of DPF 21inNot lower than lower limit of DPF 21 working pressure
Figure BDA0003190402260000114
The system does not adjust.
Step six, the ECU control unit 44 automatically adjusts the urea injection quantity of the first urea injection unit 28 and simultaneously adjusts the temperature value T ' at the air inlet of the first SCR 29 according to the temperature value T ' obtained by the fourth temperature sensor 27 'inAdjusting the inlet air temperature of the first SCR 29 to the optimum working temperature T of the first SCRSCRThe method specifically comprises the following steps: first SCR 29 intake port temperature T 'obtained by ECU control unit 44'inIs higher than the preset working temperature T of the first SCRSCRThird cooler 26 is driven to operate to make first SCR 29 inlet temperature T'inCooling to the preset working temperature T of the first SCRSCR(ii) a If first SCR 29 air inlet temperature T'inLower than the preset working temperature T of the first SCRSCRAnd driving the second heater 25 to work to enable the first SCR 29 to have the air inlet temperature T'inHeating to the preset working temperature T of the first SCRSCR(ii) a If first SCR 29 air inlet temperature T'inEqual to the preset working temperature T of the first SCRSCRThe system does not adjust.
Step seven, the ECU control unit 44 obtains the NOx concentration at the exhaust port of the first SCR 29 in real time through the NOx sensor 30, and if the NOx concentration exceeds the maximum NOx emission limit valuemaxWhen the third reversing valve 31 rotates by a certain angle, the exhaust gas of the first SCR 29 can only enter the second bypass air inlet pipe 35 through the exhaust pipe 32, and is further purified by the second SCR 41, and the ECU control unit 44 obtains the pressure P at the air inlet of the second SCR 41 through the third pressure sensor 39 at this moment3If P is3Below the lower operating pressure limit of the second SCR 41
Figure BDA0003190402260000115
The ECU control unit 44 activates the second fan 34 to cause the pressure P at the inlet of the second SCR 413Is pressurized to the preset working pressure P of the second SCR 41SCR(ii) a If the pressure P at the inlet of the second SCR 413Not lower than the lower limit of the working pressure of the second SCR 41
Figure BDA0003190402260000121
The second fan 34 is not activated and the ECU control unit 44 automatically adjusts the urea injection amount of the second urea injection unit 40 (adjustment principle: calculating the NOx content to be reduced based on the existing NOx concentration and the specified NOx emission limit, and then the NOx is hydrolyzed by the NH generated by urea in the SCR under the action of the catalyst3Reduction to N2The required urea injection amount is automatically calculated according to the reaction equation, and related calculation programs are widely integrated on the ECU control unit), and meanwhile, the ECU control unit 44 obtains the temperature value T at the air inlet of the second SCR 41 according to the fifth temperature sensor 38 "inAdjusting the temperature value at the air inlet of the second SCR 41 to the SCR working optimal temperature T by adopting the method in the step sixSCR(ii) a The ECU control unit 44 controls the rotation angle of the fourth directional control valve 33, so that the exhaust gas purified by the second SCR 41 enters the exhaust pipe 32 through the second bypass exhaust pipe 42 and is then discharged to the atmosphere; if the NOx concentration does not exceed the maximum NOx emission limit NOxmaxWhen the third change valve 31 is rotated, the passage from the exhaust pipe 32 to the second bypass intake pipe 35 is closed, and when the fourth change valve 33 is rotated, the passage from the exhaust pipe 32 to the second bypass exhaust pipe 42 is closed, and the exhaust gas is purified by the first SCR 29 and then directly discharged to the atmosphere from the exhaust pipe 32.
In the method, the DOC, DPF and SCR set values are set according to the recommended values of manufacturers and the empirical values of the past engine test data, and the CO, HC and NOx emission threshold set values are set according to the applied specific emission regulation.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (4)

1. The automobile exhaust after-treatment method is characterized by comprising the following steps:
the method comprises the steps that firstly, an existing automobile tail gas aftertreatment system is improved, the improved automobile tail gas aftertreatment system comprises a first DOC (7), a second DOC (13), a DPF (21), a first SCR (29) and a second SCR (41), an air inlet of the first DOC (7) is fixedly connected with an exhaust pipe (3) of an engine (2), the exhaust pipe (3) close to one side of the engine (2) is connected with an air inlet manifold (1) of the engine (2) through an electromagnetic valve (43), a first cooler (4), a first temperature sensor (5) and a fuel injection unit (6) are connected to the exhaust pipe (3) close to the air inlet of the first DOC (7), and the first temperature sensor (5) and the fuel injection unit (6) are arranged on the inner wall of the exhaust pipe (3) close to the air inlet of the first DOC (7);
an exhaust port of the first DOC (7) is sequentially connected with a rotatable first reversing valve (10), a rotatable second reversing valve (15), a rotatable first fan (16), a rotatable first heater (17), a rotatable second cooler (18) and an air inlet of the DPF (21) through a first connecting pipe (11), an HC sensor (8) and a CO sensor (9) are arranged on the inner wall of the first connecting pipe (11) close to the exhaust port of the first DOC (7), a second temperature sensor (19) and a first pressure sensor (20) are respectively arranged on the inner wall of the air inlet of the DPF (21) body, and a third temperature sensor (22) and a second pressure sensor (23) are respectively arranged on the inner wall of the exhaust port of the DPF (21) body;
an air inlet of the second DOC (13) is connected with the first connecting pipe (11) through a first bypass air inlet pipe (12), an air outlet of the second DOC (13) is connected with the first connecting pipe (11) through a first bypass exhaust pipe (14), the first reversing valve (10) can enable the first bypass air inlet pipe (12) to be communicated with or disconnected from the first connecting pipe (11) through rotation, and the second reversing valve (15) can enable the first bypass exhaust pipe (14) to be communicated with or disconnected from the first connecting pipe (11) through rotation;
an air outlet of the DPF (21) is sequentially connected with a second heater (25), a third cooler (26) and an air inlet of the first SCR (29) through a second connecting pipe (24), a fourth temperature sensor (27) and a first urea injection unit (28) are respectively arranged on the inner wall of the second connecting pipe (24) close to the air inlet of the first SCR (29), an air outlet of the first SCR (29) is sequentially connected with a rotatable third reversing valve (31), a fourth reversing valve (33) and ambient air through a tail air pipe (32), an NOx sensor (30) is arranged on the inner wall of the tail air pipe (32) close to the air outlet of the first SCR (29), an air inlet of the second SCR (41) is sequentially connected with a fourth cooler (37), a third heater (36), a second fan (34) and the front end of the tail air pipe (32) close to the air outlet of the first SCR (29) through a second bypass air inlet pipe (35), an exhaust port of the second SCR (41) is communicated with the tail end of an exhaust pipe (32) communicated with ambient air through a second bypass exhaust pipe (42), a fifth temperature sensor (38), a third pressure sensor (39) and a second urea injection unit (40) are respectively installed on the inner wall of a second bypass air inlet pipe (35) positioned between a fourth cooler (37) and an air inlet of the second SCR (41), the third reversing valve (31) can enable the second bypass air inlet pipe (35) to be communicated with or disconnected from the exhaust pipe (32) through rotation, and the fourth reversing valve (33) can enable the second bypass exhaust pipe (42) to be communicated with or disconnected from the exhaust pipe (32) through rotation;
the signal output ends of the first temperature sensor, the HC sensor, the CO sensor, the second temperature sensor, the first pressure sensor, the third temperature sensor, the second pressure sensor, the fourth temperature sensor, the NOx sensor, the fifth temperature sensor and the third pressure sensor are all connected with the signal input end of an ECU control unit (44) through control lines, and the signal output end of the ECU control unit (44) is respectively connected with the signal input ends of a first cooler, a fuel injection unit, a first reversing valve, a second reversing valve, a first fan, a first heater, a second cooler, a second heater, a third cooler, a first urea injection unit, a third reversing valve, a fourth reversing valve, a second fan, a third heater, a fourth cooler and an electromagnetic valve through control lines;
step two, the ECU control unit obtains the exhaust temperature T discharged by the engine at the first DOC air inlet in real time through the first temperature sensor1If T is1Lower limit of catalyst failure temperature in first DOC or more
Figure FDA0003190402250000021
The ECU control unit opens the electromagnetic valve to enable part of exhaust gas in the exhaust pipe to flow through an engine intake manifold and enter an engine cylinder again to do work, and meanwhile, the ECU control unit starts the first cooler to further enable the exhaust gas temperature in the exhaust pipe to be reduced to a first DOC preset working temperature TDOC(ii) a If T1Less than the lower limit of the catalyst failure temperature in the first DOC
Figure FDA0003190402250000022
The system is not adjusted;
step three, the ECU control unit obtains the HC concentration and the CO concentration at the exhaust port of the first DOC in real time through the HC sensor and the CO sensor, and if the HC concentration exceeds the HC emission maximum limit value, HCmaxOr the CO concentration exceeds the maximum CO emission limit COmaxThe first reversing valve rotates by a certain angle, so that the exhaust gas of the engine can only enter the first bypass air inlet pipe through the exhaust pipe and is further purified by the second DOC, and meanwhile, the exhaust gas further purified by the second DOC enters the first connecting pipe through the first bypass exhaust pipe; HC if neither HC nor CO concentration exceeds the HC emission maximum limitmaxAnd maximum limit of CO emission COmaxWhen the first reversing valve rotates by a certain angle, the passage from the exhaust pipe to the first bypass air inlet pipe is closed, and meanwhile, the passage from the first connecting pipe to the first bypass exhaust pipe is closed by a certain angle of rotation of the second reversing valve, so that the exhaust gas only flows through the first connecting pipe;
step four, judging whether to judgeThe regeneration of the DPF is carried out, specifically: the ECU acquires the temperature T at the air inlet of the DPF in real time through the second temperature sensor and the first pressure sensorinAnd PinAnd the temperature T at the exhaust port of the DPF is acquired in real time through a third temperature sensor and a second pressure sensoroutAnd PoutSubtracting the temperature value of the second temperature sensor from the temperature value of the third temperature sensor to obtain a DPF temperature change value delta TDPFAnd subtracting the pressure value of the first pressure sensor from the pressure value of the second pressure sensor to obtain a DPF pressure variation value delta PDPFThen, the following judgment is made:
step 41, if the temperature variation value Delta T of the DPFDPFAnd the pressure variation value DeltaPDPFAny one group exceeding the temperature change threshold
Figure FDA0003190402250000031
And a pressure variation threshold
Figure FDA0003190402250000032
Then, the DPF is regenerated, specifically: when the temperature T at the DPF air inlet obtained by the second temperature sensorinThe DPF regeneration temperature is exceeded, and the ECU controls the second cooler to work to enable the temperature T at the air inlet of the DPF to be exceededinCooling to DPF preset light-off temperature Tcom(ii) a When the temperature T at the DPF air inlet obtained by the second temperature sensorinLower than the lower limit of the DPF operating temperature
Figure FDA0003190402250000033
At the moment, the ECU drives the fuel injection unit to work, and adjusts the fuel injection quantity of the fuel injection unit to be the maximum safe fuel quantity qmaxMeanwhile, the ECU drives the first heater to work so as to further heat the exhaust gas at the DPF air inlet to ensure that the temperature T of the DPF air inlet is enabledinReach the preset light-off temperature T of DPFcom(ii) a When DPF operating temperature lower limit
Figure FDA0003190402250000039
ECU controlThe unit is based on the temperature T at the DPF air inletinAnd DPF a predetermined light-off temperature TcomAutomatically adjusting the fuel injection quantity of the fuel injection unit to enable the temperature T of the DPF air inletinReach the preset light-off temperature T of DPFcom；
Step 42, if the temperature variation value Delta T of the DPF is detectedDPFAnd the pressure variation value DeltaPDPFDo not exceed the temperature variation threshold
Figure FDA0003190402250000035
And a pressure variation threshold
Figure FDA0003190402250000036
The regeneration of the DPF is not performed, and the temperature T at the air inlet of the DPF obtained by the ECU control unit at this timeinIf it is higher than the preset working temperature T of DPFgzThen driving the second cooler to work to make the DPF inlet temperature TinCooling to DPF preset working temperature Tgz(ii) a If DPF inlet temperature TinLower than the preset working temperature T of DPFgzThen driving the first heater to work to make the DPF inlet temperature TinHeating to DPF preset working temperature Tgz(ii) a If DPF inlet temperature TinEqual to the preset operating temperature T of the DPFgzThe system is not adjusted;
step five, the ECU control unit obtains the pressure P at the DPF air inlet according to the first pressure sensorinJudging whether to carry out system adjustment, specifically: if pressure P at DPF inletinLess than the lower limit of DPF working pressure
Figure FDA0003190402250000037
The ECU starts the first fan to make the pressure P at the DPF air inletinSupercharging to DPF preset working pressure Pgz(ii) a If pressure P at DPF inletinNot lower than the lower limit of the DPF working pressure
Figure FDA0003190402250000038
The system is not adjusted;
step six, ECU controlThe control unit automatically adjusts the urea injection quantity of the first urea injection unit and simultaneously obtains a temperature value T 'at the air inlet of the first SCR according to the fourth temperature sensor'inAdjusting the inlet air temperature of the first SCR to the optimum working temperature T of the first SCRSCRThe method specifically comprises the following steps: if the ECU control unit obtains the first SCR air inlet temperature T'inIs higher than the preset working temperature T of the first SCRSCRAnd driving the third cooler to work to enable the first SCR inlet temperature T'inCooling to the preset working temperature T of the first SCRSCR(ii) a If first SCR air inlet temperature T'inLower than the preset working temperature T of the first SCRSCRAnd driving a second heater to work to enable the first SCR inlet temperature T'inHeating to the preset working temperature T of the first SCRSCR(ii) a If first SCR air inlet temperature T'inEqual to the preset working temperature T of the first SCRSCRThe system is not adjusted;
step seven, the ECU obtains the NOx concentration at the exhaust port of the first SCR in real time through a NOx sensor, and if the NOx concentration exceeds the maximum NOx emission limit value NOxmaxWhen the third reversing valve rotates by a certain angle, the exhaust gas of the first SCR can only enter the second bypass air inlet pipe through the exhaust pipe, the exhaust gas is further purified through the second SCR, and the ECU acquires the pressure P at the air inlet of the second SCR through the third pressure sensor3If P is3Lower than the second SCR operating pressure lower limit
Figure FDA0003190402250000041
The ECU starts the second fan to make the pressure P at the air inlet of the second SCR3Boosting to a second SCR preset working pressure PSCR(ii) a If the pressure P at the second SCR inlet3Not lower than the lower limit of the working pressure of the second SCR
Figure FDA0003190402250000042
The second fan is not started, the ECU control unit automatically adjusts the urea injection amount of the second urea injection unit, and the ECU control unit obtains the temperature value T at the air inlet of the second SCR according to the fifth temperature sensor "inIn the sixth stepThe temperature value at the air inlet of the second SCR is adjusted to the optimal SCR working temperature TSCR(ii) a The ECU control unit controls the rotation angle of the fourth reversing valve to enable the exhaust purified by the second SCR to enter the tail gas pipe from the second bypass exhaust pipe and then to be exhausted to the atmosphere; if the NOx concentration does not exceed the maximum NOx emission limit NOxmaxAnd if the third reversing valve rotates by a certain angle, closing the passage from the tail gas pipe to the second bypass gas inlet pipe, and simultaneously, closing the passage from the tail gas pipe to the second bypass gas outlet pipe by a certain angle of rotation of the fourth reversing valve, wherein the exhaust gas is purified by the first SCR and then directly discharged to the atmosphere by the tail gas pipe.
2. The automobile exhaust after-treatment method according to claim 1, characterized in that: first DOC, second DOC, first SCR and second SCR are close to air inlet department and arrange a plurality of baffling piece with welding mode along circumference, and baffling piece and horizontal contained angle are 15 degrees.
3. The automobile exhaust gas after-treatment method according to claim 1 or 2, characterized in that: the first cooler, the second cooler and the third cooler are circular sleeves sleeved on the outer wall of the pipeline, cooling water or cooling media are communicated in the circular sleeves, the first heater, the second heater and the third heater are square hollow resistance boxes sleeved on the outer wall of the pipeline, and resistance wires are arranged in the square hollow resistance boxes.
4. The automobile exhaust gas after-treatment method according to claim 1 or 2, characterized in that: the first fan and the second fan are connected with the pipeline in a welding mode, sealing rings are arranged on the periphery of the first fan and the second fan to prevent gas leakage, the total area of blades of the first fan and the second fan is not more than one third of the cross section area of the pipeline, and the number of the blades is only 6.
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