CN110307063B

CN110307063B - DPF active regeneration air inlet control system and method utilizing SCR gas auxiliary structure

Info

Publication number: CN110307063B
Application number: CN201910428867.XA
Authority: CN
Inventors: 谭丕强; 王德源; 胡志远; 楼狄明
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2019-05-22
Filing date: 2019-05-22
Publication date: 2021-03-26
Anticipated expiration: 2039-05-22
Also published as: CN110307063A

Abstract

The invention relates to a DPF active regeneration air inlet control system and method utilizing an SCR gas auxiliary structure, wherein the method comprises the following steps: a signal acquisition step of acquiring acquisition signals of the sensor component, including a DOC front oxygen sensor signal Sig_O1Exhaust mass flow signal Sig_QmFront temperature sensor Signal Sig of DPF_T1Post DPF temperature sensor Signal Sig_T2DOC front temperature sensor signal Sig_T3And post SCR NO_xSensor signal Sig_NOx(ii) a Triggering; DOC front air supplement step; and (5) thermal management. Compared with the prior art, the invention has the advantages of promoting the evaporation and atomization effects of the injected fuel in the exhaust tail pipe, improving the HC combustion efficiency and the like.

Description

DPF active regeneration air inlet control system and method utilizing SCR gas auxiliary structure

Technical Field

The invention relates to the technical field of diesel engine control, in particular to a DPF active regeneration air inlet control system and method utilizing an SCR gas auxiliary structure.

Background

For a heavy Diesel engine adopting regeneration, tail pipe oil injection is a common active regeneration mode, namely oil is injected in front of a Diesel Oxidation Catalyst (DOC), the temperature rise characteristic of the DOC is utilized, so that the temperature of an inlet of a Diesel Particulate Filter (DPF) reaches a Particulate Matter (PM) ignition point (about 550 ℃), and PM accumulated in the DPF is burnt. However, the tail pipe oil injection active regeneration also has the defects of uncontrollable regeneration, HC slippage and carrier burnthrough and burnout cracking caused by high temperature.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned drawbacks of the prior art, and providing a DPF active regeneration air intake control system and method using an SCR gas-assisted structure.

The purpose of the invention can be realized by the following technical scheme:

a DPF active regeneration induction control system utilizing an SCR gas assist configuration for controlling a diesel exhaust aftertreatment system, comprising:

a sensor assembly connected to the diesel exhaust aftertreatment system including exhaust mass flowSensor, oxygen sensor before DOC, temperature sensor before DPF, temperature sensor after DPF, and NO after SCR_xA sensor;

and the information processing terminal is respectively connected with the sensor assembly and the diesel engine exhaust post-processing system and is used for generating a control signal for the diesel engine exhaust post-processing system according to the acquisition signal of the sensor assembly.

Further, the information processing terminal includes:

a signal acquisition module for acquiring the acquisition signal of the sensor assembly, including a DOC pre-oxygen sensor signal Sig_O1Exhaust mass flow signal Sig_QmFront temperature sensor Signal Sig of DPF_T1Post DPF temperature sensor Signal Sig_T2DOC front temperature sensor signal Sig_T3And post SCR NO_xSensor signal Sig_NOx；

A trigger module responding after receiving the DPF regeneration trigger time signal and used for judging Sig_NOxIf the signal is greater than the maximum limit value, if so, generating no system trigger signal, and if not, generating the system trigger signal according to Sig_T1And Sig_T3Further judging whether an active regeneration trigger signal or an oil injection trigger signal is generated;

DOC front air supplement module for supplementing air according to Sig_O1And Sig_QmGenerating opening and closing and opening control signals aiming at a DOC air valve;

a thermal management module to manage according to Sig_T2And generating an opening and closing control signal aiming at the DOC front air valve.

Further, in the trigger module, after generating the system trigger signal, the sigs is first paired_T1Make a judgment if Sig_T1If the temperature is less than 550 ℃, an active regeneration trigger signal is generated and then the signal is compared with Sig_T3Make a judgment if Sig_T3If the temperature is less than 230 ℃, an oil injection trigger signal is generated.

Furthermore, in the DOC front air supplement module, the comparison of O in the exhaust of the diesel engine₂Mass flow Sig_OmActual oxygen demand m for sufficient combustion with HC_O2In relation to each other, if m_O2≥Sig_OmThen opening DOC front air valve until the active regeneration process is finished or m is reached_O2＜Sig_OmAnd (4) conditions.

Further, in the thermal management module, whether Sig exists is judged_T2≥T_maxThen opening DOC advance air valve until Sig is reached_T2＜T_maxConditional, the active regeneration process is re-triggered.

The invention also provides a control method of the DPF active regeneration air inlet control system utilizing the SCR gas auxiliary structure, which comprises the following steps:

a signal acquisition step of acquiring acquisition signals of the sensor component, including a DOC front oxygen sensor signal Sig_O1Exhaust mass flow signal Sig_QmFront temperature sensor Signal Sig of DPF_T1Post DPF temperature sensor Signal Sig_T2DOC front temperature sensor signal Sig_T3And post SCR NO_xSensor signal Sig_NOx；

A triggering step of judging Sig after receiving the DPF regeneration triggering time signal_NOxIf the signal is greater than the maximum limit value, if so, generating no system trigger signal, and if not, generating the system trigger signal according to Sig_T1And Sig_T3Further judging whether an active regeneration trigger signal or an oil injection trigger signal is generated;

DOC pre-air supplement step according to Sig_O1And Sig_QmGenerating opening and closing and opening control signals aiming at a DOC air valve;

thermal management step according to Sig_T2And generating an opening and closing control signal aiming at the DOC front air valve.

Further, in the triggering step, Sig is firstly triggered_T1Make a judgment if Sig_T1If the temperature is less than 550 ℃, an active regeneration trigger signal is generated and then the signal is compared with Sig_T3Make a judgment if Sig_T3If the temperature is less than 230 ℃, an oil injection trigger signal is generated.

Furthermore, in the DOC front air supplement step, comparing O in the exhaust of the diesel engine₂Mass flow Sig_OmActual oxygen demand m for sufficient combustion with HC_O2In relation to each other, if m_O2≥Sig_OmThen opening DOC front air valve until the active regeneration process is finished or m is reached_O2＜Sig_OmAnd (4) conditions.

Further, in the thermal management step, whether Sig exists is judged_T2≥T_maxThen opening DOC advance air valve until Sig is reached_T2＜T_maxConditional, the active regeneration process is re-triggered.

Compared with the prior art, the invention has the following beneficial effects:

1. by reasonably controlling the oxygen concentration in front of the DOC, the oxidation of HC in the DOC is promoted, the unoxidized amount of HC is reduced, and the HC slip is reduced;

2. through the thermal management step, the effective control of the internal temperature peak value of the DPF during active regeneration is realized, and the failure condition of the DPF is reduced;

3. the DOC front air supplement method related to the DOC method can promote the fuel to be sent out before the DOC and the atomization uniformity, reduce the use of an HC mixer and reduce the cost of an exhaust aftertreatment system of a diesel engine.

Drawings

FIG. 1 is a schematic diagram of an active regeneration air intake control system of a DPF utilizing a diesel engine SCR gas assist structure according to the present invention;

FIG. 2 is a schematic view of a DOC + DPF system sensor arrangement according to the present invention;

FIG. 3 is a schematic view of a sensor arrangement of an SCR system according to the present invention;

FIG. 4 shows a heavy duty diesel engine P of a type_injMAP and P_inj-PW_inj-m_injMAP, wherein (4a) is P_injMAP, (4b) is P_inj-PW_inj-m_inj MAP；

Reference numbers in the figures: 1 is a gas storage tank, 2 is a pressure stabilizing cavity, 3 is a blowback valve, 4 is a mixing cavity, 5 is a metering valve, 6 is a urea filter element, 7 is a diaphragm pump, 8 is a pressure release valve, 9 is a urea box, 10 is a fuel injector, 11 is a DOC advance gas valve, 12 is a DOC device, 13 is a DPF device, 14 is an SCR device, 15 is a urea injector, 16 is a diesel exhaust pipeline, 17 is an airflow direction, 18 is an exhaust mass flow sensor, and 19 is a DOC front oxygen sensor,20 is a DOC front temperature sensor, 21 is a DPF front temperature sensor, 22 is a DPF rear temperature sensor, and 23 is a SCR rear NO_xA sensor.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

The DPF active regeneration air inlet control system and method utilizing the SCR (Selective Catalytic Reduction) gas-auxiliary structure of the diesel engine can promote the full oxidation of Hydrocarbon (HC) in DOC and reduce HC slip; the effective control of the temperature peak value in the DPF during active regeneration is realized, and the failure condition of the DPF is reduced; the evaporation and atomization uniformity of the injected fuel before the DOC can be improved, additional devices are reduced, and the cost of an exhaust aftertreatment system of the diesel engine is effectively reduced.

Fig. 1 shows a design diagram of a DPF active regeneration air intake control system using a gas-assisted structure of a diesel SCR gas-assisted structure, for controlling a diesel exhaust aftertreatment system, comprising:

the sensor component is connected with the diesel engine exhaust aftertreatment system and comprises an exhaust mass flow sensor, an oxygen sensor before DOC, a temperature sensor before DPF, a temperature sensor after DPF and NO after SCR_xThe specific connection mode of the sensors is shown in fig. 2 and 3, and in practical application, the number and the types of the sensors can be increased;

the information processing terminal is respectively connected with the sensor assembly and the diesel engine exhaust post-processing system, is used for generating a control signal for the diesel engine exhaust post-processing system according to the acquisition signal of the sensor assembly, and comprises a signal acquisition module, a trigger module, a DOC front air supply module and a heat management module.

The specific steps of the control method implemented by the control system are described as follows.

Step 1, signal acquisition stage.

Acquiring signals of sensors at each position of an exhaust aftertreatment system of the diesel engine, including a DOC front oxygen sensor signal Sig_O1Exhaust mass flow signal Sig_QmFront temperature sensor Signal Sig of DPF_T1Post DPF temperature sensor Signal Sig_T2DOC front temperature sensor signal Sig_T3And post SCR NO_xSensor signal Sig_NOx. In the fuel injection feedforward calibration of the active regeneration system, the pressure (P) of the fuel pump is fixed after the type selection of the fuel pump and the determination of the injection electromagnetic valve_inj) By adjusting the Pulse Width (PW) of the electronic valve_inj) Determining the actual fuel injection quantity (m)_inj) And the oil injector is a hole-type oil injector. minj by query P_inj-PW_inj-m_injMAPs (MAP) are available. The urea injection amount (murea) may be calculated by a urea injection controller (DCU). FIG. 4 is a diagram of an aftertreatment system P for a heavy duty diesel engine of the type having a displacement of 8L_injMAP and P_inj-PW_inj-m_injMAP, at query time, PW_injPW_inA fixed adjustment factor (< 1) is first divided.

And 2, a system triggering stage.

After DPF regeneration time is triggered, Sig is determined_NOxWhether or not it is greater than the maximum limit value (lim)_NOx). If Sig_NOx＜lim_NOxTriggering the DPF active regeneration air intake control system using SCR gas-assisted structure of the invention and judging Sig_T1. If Sig_T1Less than 550 ℃, triggering active regeneration, and judging Sig_T3. If Sig_T3And < 230 ℃ to trigger oil injection. Other variables of the active regeneration triggering, such as the differential pressure across the DPF, the carbon loading calculated based on the model, the carbon loading calculated based on the mileage or the time of travel, etc., are the same as in the prior art. lim (small)_NOxThe diesel engine exhaust emission control method can be selected according to the latest diesel engine exhaust emission control regulation limit value, the DPF front exhaust temperature of 550 ℃ and the DOC front exhaust temperature of 230 ℃ are selected more reasonable limit values, and the values can be corrected in the practical application process.

And step 3, DOC front air supplement stage.

By Sig_O1Calculating O in the exhaust gas of a diesel engine₂Mass flow (Sig)_Om) The calculation formula is as follows,

Sig_Om＝Sig_O1×Sig_Qm

m obtained by inquiring MAP_injCalculating the actual oxygen demand (m) for sufficient combustion of HC_O2) The calculation formula is as follows,

m_O2＝m_inj/42×(3+1.5)×32×mf

where mf is the actual oxygen demand correction factor (> 1).

If m is_O2≥Sig_OmThe SCR gas auxiliary structure is used for supplying gas, the DOC gas inlet valve 11 is opened, and the Sig is continuously monitored at the moment_O1Until the end of the active regeneration process, or m_O2＜Sig_OmAnd (4) conditions. The opening degree of the DOC front valve can be controlled according to Sig_OmThe adjustment is carried out to obtain the proper air inlet mass flow so as to avoid the problem of HC dilution caused by overlarge air inlet mass flow, influence on DOC oxidation temperature rise capability and reduce the DPF active regeneration effect.

And 4, a thermal management stage.

Let T_maxIs the highest DPF back exhaust temperature that the DPF carrier can withstand. When Sig_T2Greater than the highest DPF after-row T that the DPF carrier can withstand_maxAnd the carrier is easy to break, burn through and the like, at the moment, the gas valve 11 before the DOC is opened, and the gas is supplemented before the DOC, so that on one hand, the HC concentration in exhaust gas can be reduced, the DOC temperature rise rate is reduced, on the other hand, the exhaust mass flow is increased, the average temperature is reduced, and the heat required for raising the same temperature is reduced, so that the Sig is reduced_T2The purpose of (1). When Sig_T2Down to T_maxAnd then selecting a proper time to re-trigger the active regeneration process.

The control system and the control method can promote the evaporation and atomization effects of the injected fuel in the tail pipe, improve the HC combustion efficiency, and supplement and improve the established DPF tail pipe fuel injection active regeneration control strategy.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A DPF active regeneration air inlet control system utilizing an SCR gas auxiliary structure is used for controlling a diesel engine exhaust post-treatment system and is characterized in that the diesel engine exhaust post-treatment system comprises a gas storage tank, a pressure stabilizing cavity, a blowback threshold, a mixing cavity, a metering valve, a urea filter element, a diaphragm pump, a pressure release valve, a urea box, a fuel injector, a DOC air inlet valve, a DOC device, a DPF device, an SCR device, a urea injector and a diesel engine exhaust pipeline, wherein the gas storage tank, the pressure stabilizing cavity, the blowback threshold, the mixing cavity, the metering valve, the urea filter element, the diaphragm pump and the urea box are sequentially connected, the pressure release valve is connected with the diaphragm pump in parallel, the DOC air inlet valve, the DOC device, the DPF device and the SCR device are sequentially connected through the diesel engine exhaust pipeline, the fuel injector is arranged at the input end of the DOC air inlet valve, and the diesel engine exhaust pipeline connected,

the control system includes:

the sensor component is connected with the diesel engine exhaust aftertreatment system and comprises an exhaust mass flow sensor, an oxygen sensor before DOC, a temperature sensor before DPF, a temperature sensor after DPF and NO after SCR_xA sensor;

2. The DPF active regeneration intake control system using an SCR gas-assist structure according to claim 1, wherein the information processing terminal includes:

a signal acquisition module forAcquiring acquisition signals of sensor components, including DOC pre-oxygen sensor signal Sig_O1Exhaust mass flow signal Sig_QmFront temperature sensor Signal Sig of DPF_T1Post DPF temperature sensor Signal Sig_T2DOC front temperature sensor signal Sig_T3And post SCR NO_xSensor signal Sig_NOx；

3. The system as claimed in claim 2, wherein the trigger module generates a system trigger signal and then first generates a system trigger signal to Sig_T1Make a judgment if Sig_T1If the temperature is less than 550 ℃, an active regeneration trigger signal is generated and then the signal is compared with Sig_T3Make a judgment if Sig_T3If the temperature is less than 230 ℃, an oil injection trigger signal is generated.

4. The DPF active regeneration air intake control system using SCR gas assist structure as claimed in claim 2, wherein the DOC pre-air make-up module compares O in diesel exhaust₂Mass flow Sig_OmActual oxygen demand m for sufficient combustion with HC_O2In relation to each other, if m_O2≥Sig_OmThen opening DOC front air valve until the active regeneration process is finished or m is reached_O2＜Sig_OmAnd (4) conditions.

5. The method of claim 2The DPF active regeneration air inlet control system utilizing the SCR gas auxiliary structure is characterized in that whether Sig exists or not is judged in the heat management module_T2≥T_maxIf Sig_T2≥T_maxThen opening DOC advance air valve until Sig is reached_T2＜T_maxConditional, the active regeneration process is re-triggered.

6. A control method of a DPF active regeneration intake control system using an SCR gas-assist structure according to claim 1, comprising:

7. The control method according to claim 6, wherein in the triggering step, Sig is first triggered_T1Make a judgment if Sig_T1If the temperature is less than 550 ℃, an active regeneration trigger signal is generated and then the signal is compared with Sig_T3Make a judgment if Sig_T3If the temperature is less than 230 ℃, an oil injection trigger signal is generated.

8. The control method according to claim 6, wherein,characterized in that in the DOC front air supplement step, O in the exhaust of the diesel engine is compared₂Mass flow Sig_OmActual oxygen demand m for sufficient combustion with HC_O2In relation to each other, if m_O2≥Sig_OmThen opening DOC front air valve until the active regeneration process is finished or m is reached_O2＜Sig_OmAnd (4) conditions.

9. The control method according to claim 6, wherein in the thermal management step, it is determined whether Sig is present_T2≥T_maxIf Sig_T2≥T_maxThen opening DOC advance air valve until Sig is reached_T2＜T_maxConditional, the active regeneration process is re-triggered.