阅读说明：本技术 一种scr效率恢复的控制方法 (SCR efficiency recovery control method ) 是由 陈旭 冯坦 张覃亚 陈镇 缪斯浩 刘国平 陈猛 柴启寅 徐傲 李志明 于 2019-09-20 设计创作，主要内容包括：一种SCR效率恢复的控制方法,该控制方法包括以下步骤：A、若SCR效率低的原因是尿素浓度低,则更换正常浓度的尿素；B、若SCR效率低的原因是尿素喷射控制模型偏差大,则修正尿素喷射控制模型的偏差；C、若SCR效率低的原因是SCR结晶,则开启SCR去结晶再生；D、若SCR效率低的原因是SCR硫中毒,则开启SCR脱硫再生；E、若SCR效率低的原因是SCR催化剂失活,则更换SCR。本设计不仅能恢复SCR效率,而且控制方法可靠性高。(A control method of SCR efficiency recovery, the control method comprising the steps of: A. if the reason of low SCR efficiency is low urea concentration, replacing urea with normal concentration; B. if the reason of low SCR efficiency is that the deviation of the urea injection control model is large, correcting the deviation of the urea injection control model; C. if the reason of low SCR efficiency is SCR crystallization, starting SCR to remove crystallization regeneration; D. if the reason of low SCR efficiency is SCR sulfur poisoning, starting SCR desulfurization regeneration; E. if the cause of the low SCR efficiency is deactivation of the SCR catalyst, the SCR is replaced. The design can not only recover the SCR efficiency, but also has high reliability of the control method.)

1. A control method for SCR efficiency recovery, characterized by comprising the steps of:

A. if the reason of low SCR efficiency is low urea concentration, replacing urea with normal concentration;

B. if the reason that the SCR efficiency is low is that the deviation of the urea injection control model is large, urea injection is stopped to enable the original machine NOx to completely react the ammonia storage amount of the SCR, when the deviation epsilon between the measured value of the rear NOx sensor and the NOx value of the original machine is smaller than a set value (the original machine NOx value-the measured value of the rear NOx sensor)/the original machine NOx value, and the range of the set value is 0% -30%, the ammonia storage amount in the SCR is considered to be completely reacted, at the moment, the urea injection control model is restored to the initial state again, all the control parameters of the urea injection control model are changed into 0, the deviation of the urea injection control model is updated to 0, and further the deviation of the urea injection control model is corrected;

C. if the reason of low SCR efficiency is SCR crystallization, starting SCR de-crystallization regeneration:

c1 and SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

c2, SCR decrystallization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for SCR decrystallization regeneration;

c3, SCR withdrawal and recrystallization regeneration:

c31, stop oil injection

If the SCR decrystallization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR de-crystallization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR is subjected to crystallization regeneration and the controller is adopted to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step C32;

c32, recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

D. if the reason of low SCR efficiency is SCR sulfur poisoning, starting SCR desulfurization regeneration:

d1, SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

d2, SCR desulfurization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by adopting the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for desulfurization regeneration;

d3, quitting SCR desulfurization regeneration:

d31, stop oil injection

If the SCR desulfurization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR desulfurization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR desulfurization regeneration adopts the controller to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe at the same time, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step D32;

d32, and recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

E. if the cause of the low SCR efficiency is deactivation of the SCR catalyst, the SCR is replaced.

2. A method of controlling SCR efficiency recovery according to claim 1, characterized in that: in the step C, the starting requirement of SCR decrystallization regeneration simultaneously meets the following 5 conditions: SCR crystallization; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

3. A method of controlling SCR efficiency recovery according to claim 1, characterized in that: in step C1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

4. A method of controlling SCR efficiency recovery according to claim 1, characterized in that: in step D, the start of the SCR desulfurization regeneration simultaneously satisfies the following 5 conditions: SCR sulfur poisoning; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

5. A method of controlling SCR efficiency recovery according to claim 1, characterized in that: in step D1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

Technical Field

The present invention relates to the field of Selective Catalytic Reduction (SCR) systems for exhaust aftertreatment systems, and more particularly to a method for controlling SCR efficiency recovery, which is mainly suitable for reliably recovering SCR efficiency.

Background

With the coming implementation of the national six-emission regulation, diesel engine manufacturers are developing national six-diesel engines which are matched with an aftertreatment system of a catalytic oxidizer (DOC) + a particulate filter (DPF) + a selective redox reactor (SCR) in order to reduce NOx and particulate emissions in engine exhaust. No matter the four, five or six national regulations require that the alarm is given when the emission of the NOx in the tail gas exceeds the regulation limit value, and the torque limit and the speed limit are carried out when the emission of the NOx is too high, so that the driving of a driver are influenced.

Chinese patent, application publication No. CN107076638A, invention of 2017, 8/18 discloses a system for determining a performance state of an exhaust aftertreatment system, which may include determining an ammonia-to-nitrogen ratio using a sample ammonia input value and a sample NOx input value, an actual NOx input value and an actual ammonia input value may be received, an emission value may be received from a first sensor, an NOx emission estimate, an ammonia slip estimate, and an optimal ammonia storage value for selective catalytic reduction may be determined using an iterative inefficiency calculation based at least in part on the actual NOx input value, the actual ammonia input value, and the ammonia-to-nitrogen ratio, and the NOx emission estimate, the ammonia slip estimate, and the optimal ammonia storage value may be output to a diagnostic system. Although this invention provides a diagnostic method for SCR inefficiency, it does not provide a method for restoring SCR efficiency.

Disclosure of Invention

The invention aims to overcome the defect and the problem that SCR efficiency can not be recovered in the prior art, and provides a control method for SCR efficiency recovery, which can reliably recover the SCR efficiency.

In order to achieve the above purpose, the technical solution of the invention is as follows: a control method of SCR efficiency recovery, the control method comprising the steps of:

A. if the reason of low SCR efficiency is low urea concentration, replacing urea with normal concentration;

B. if the reason that the SCR efficiency is low is that the deviation of the urea injection control model is large, urea injection is stopped to enable the original machine NOx to completely react the ammonia storage amount of the SCR, when the deviation epsilon between the measured value of the rear NOx sensor and the NOx value of the original machine is smaller than a set value (the original machine NOx value-the measured value of the rear NOx sensor)/the original machine NOx value, and the range of the set value is 0% -30%, the ammonia storage amount in the SCR is considered to be completely reacted, at the moment, the urea injection control model is restored to the initial state again, all the control parameters of the urea injection control model are changed into 0, the deviation of the urea injection control model is updated to 0, and further the deviation of the urea injection control model is corrected;

C. if the reason of low SCR efficiency is SCR crystallization, starting SCR de-crystallization regeneration:

c1 and SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

c2, SCR decrystallization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for SCR decrystallization regeneration;

c3, SCR withdrawal and recrystallization regeneration:

c31, stop oil injection

If the SCR decrystallization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR de-crystallization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR is subjected to crystallization regeneration and the controller is adopted to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step C32;

c32, recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

D. if the reason of low SCR efficiency is SCR sulfur poisoning, starting SCR desulfurization regeneration:

d1, SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

d2, SCR desulfurization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by adopting the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for desulfurization regeneration;

d3, quitting SCR desulfurization regeneration:

d31, stop oil injection

If the SCR desulfurization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR desulfurization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR desulfurization regeneration adopts the controller to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe at the same time, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step D32;

d32, and recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

E. if the cause of the low SCR efficiency is deactivation of the SCR catalyst, the SCR is replaced.

In the step C, the starting requirement of SCR decrystallization regeneration simultaneously meets the following 5 conditions: SCR crystallization; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

In step C1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

In step D, the start of the SCR desulfurization regeneration simultaneously satisfies the following 5 conditions: SCR sulfur poisoning; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

In step D1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

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

the invention relates to a control method for SCR efficiency recovery, which aims at recovering SCR efficiency for specific reasons of low SCR efficiency; if the reason of low SCR efficiency is low urea concentration, replacing urea with normal concentration; if the reason of low SCR efficiency is that the deviation of the urea injection control model is large, correcting the deviation of the urea injection control model; if the reason of low SCR efficiency is SCR crystallization, starting SCR to remove crystallization regeneration; if the reason of low SCR efficiency is SCR sulfur poisoning, starting SCR desulfurization regeneration; if the cause of the low SCR efficiency is deactivation of the SCR catalyst, the SCR is replaced. Therefore, the invention not only can recover the SCR efficiency, but also has high reliability of the control method.

Drawings

FIG. 1 is a schematic illustration of SCR decrystallization regeneration in accordance with the present invention.

FIG. 2 is a schematic illustration of SCR sweet regeneration in the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following description and embodiments in conjunction with the accompanying drawings.

Referring to fig. 1 and 2, a control method for recovering SCR efficiency includes the following steps:

A. if the reason of low SCR efficiency is low urea concentration, replacing urea with normal concentration;

B. if the reason that the SCR efficiency is low is that the deviation of the urea injection control model is large, urea injection is stopped to enable the original machine NOx to completely react the ammonia storage amount of the SCR, when the deviation epsilon between the measured value of the rear NOx sensor and the NOx value of the original machine is smaller than a set value (the original machine NOx value-the measured value of the rear NOx sensor)/the original machine NOx value, and the range of the set value is 0% -30%, the ammonia storage amount in the SCR is considered to be completely reacted, at the moment, the urea injection control model is restored to the initial state again, all the control parameters of the urea injection control model are changed into 0, the deviation of the urea injection control model is updated to 0, and further the deviation of the urea injection control model is corrected;

C. if the reason of low SCR efficiency is SCR crystallization, starting SCR de-crystallization regeneration:

c1 and SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

c2, SCR decrystallization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for SCR decrystallization regeneration;

c3, SCR withdrawal and recrystallization regeneration:

c31, stop oil injection

If the SCR decrystallization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR de-crystallization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR is subjected to crystallization regeneration and the controller is adopted to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step C32;

c32, recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

D. if the reason of low SCR efficiency is SCR sulfur poisoning, starting SCR desulfurization regeneration:

d1, SCR temperature rise: raising the exhaust temperature to a set temperature T1, wherein the set temperature T1 is 250-400 ℃;

d2, SCR desulfurization regeneration: when the exhaust temperature reaches a set temperature T1, controlling the post-injection oil quantity in the cylinder through the controller, injecting oil into the exhaust pipe through the post-treatment fuel injection system or simultaneously controlling the post-injection oil quantity in the cylinder and injecting oil into the exhaust pipe through the post-treatment fuel injection system by adopting the controller, so that unburned fuel oil or hydrocarbon exists in the exhaust pipe, the unburned fuel oil or hydrocarbon is oxidized when passing through a catalytic oxidizer DOC and emits heat, the exhaust temperature is raised to the set temperature T2, the range of the set temperature T2 is 480-650 ℃, and the set temperature T2 is maintained for desulfurization regeneration;

d3, quitting SCR desulfurization regeneration:

d31, stop oil injection

If the SCR desulfurization regeneration only adopts the controller to control the post-injection oil quantity in the cylinder, closing the post-injection in the cylinder; if the SCR desulfurization regeneration only adopts the post-treatment fuel injection system to inject oil into the exhaust pipe, stopping injecting oil into the exhaust pipe; if the SCR desulfurization regeneration adopts the controller to control the post-injection oil quantity in the cylinder and the post-treatment fuel injection system to inject oil into the exhaust pipe at the same time, stopping the post-injection in the cylinder and the oil injection into the exhaust pipe at the same time; when the exhaust temperature is reduced to a set temperature T3 from a set temperature T2, and the range of the set temperature T3 is 250-500 ℃, entering a step D32;

d32, and recovering to the working condition of normal operation of engine

The main oil injection timing of the engine, the rail pressure of the high-pressure common rail, the opening degree of a throttle valve, the opening degree of an exhaust gas recirculation valve, the opening degree of a variable turbocharger valve or the pre-injection oil injection quantity of the engine are all restored to a normal state;

E. if the cause of the low SCR efficiency is deactivation of the SCR catalyst, the SCR is replaced.

In the step C, the starting requirement of SCR decrystallization regeneration simultaneously meets the following 5 conditions: SCR crystallization; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

In step C1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

In step D, the start of the SCR desulfurization regeneration simultaneously satisfies the following 5 conditions: SCR sulfur poisoning; the carbon loading of the DPF of the particulate filter is less than the maximum carbon loading limit value; when the engine operating time or mileage since the last regeneration is higher than the calibrated value; the control strategy does not prohibit regeneration; the particulate filter DPF regeneration request is not triggered.

In step D1, the exhaust gas temperature value is raised to the set temperature T1 by one or more of the following measures: the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; and increasing the opening of the variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil injection quantity of the engine, and the pre-injection oil injection quantity of the engine is 0-20 g/str.

The principle of the invention is illustrated as follows:

the design aims at the specific SCR low-efficiency reason to carry out the methods of replacing qualified urea solution, controlling model self-learning, high-temperature crystallization removal regeneration, high-temperature desulfurization regeneration and the like to recover the SCR efficiency.

When the SCR efficiency is higher than a set value for stopping the recrystallization regeneration (desulfurization regeneration) or the duration of the recrystallization regeneration (desulfurization regeneration) exceeds a set value, the recrystallization regeneration (desulfurization regeneration) is stopped.

Before recovering the SCR efficiency, the SCR efficiency can be diagnosed and the cause of the SCR inefficiency can be analyzed by the following methods;

a method of diagnosing SCR efficiency, the method comprising the steps of:

1. starting the diagnostic function of the SCR efficiency, and acquiring an original machine NOx value, a rear NOx sensor measurement value and a rear NOx theoretical value;

the diagnostic function of the SCR efficiency is turned on when the following conditions are met:

the change of the rotating speed of the current working condition and the rotating speed at the previous t1 moment is less than delta 1, the range of t1 is 0.1 s-10 s, and the range of delta 1 is 10 rpm-200 rpm;

the torque percentage is less than delta 2, and the range of delta 2 is 0-20 percent;

the SCR temperature is between T1 and T2, the range of T1 is 180-240 ℃, and the range of T2 is 300-500 ℃;

the aftertreatment system has no hardware faults (including a rear NOx sensor, a temperature sensor and the like);

the urea injection amount is more than m, and the range of m is more than 100 ml/h;

the original machine NOx value is between v1 and v2, the range of v1 is 100 ppm-1500 ppm, and the range of v2 is 300 ppm-2000 ppm;

the rear NOx sensor measurement is between v3 and v4, v3 ranges from 100ppm to 1500ppm, and v4 ranges from 300ppm to 2000 ppm;

the original machine NOx value is obtained by measuring a NOx sensor arranged in front of a post processor or reading a control map according to rotating speed and torque signals, and then the original machine NOx is subjected to time delay processing, wherein the time delay processing method comprises the following steps:

t₀=V/Q；

in the above formula, V is the flow volume from the engine outlet to the rear NOx sensor or the flow volume from the front NOx sensor to the rear NOx sensor, and Q is the exhaust gas volume flow;

inputting the SCR temperature, the original NOx value, the exhaust gas flow value and the urea injection quantity into an SCR catalyst module, and calculating the theoretical value of the NOx by adopting the following formula:

N＝A-A*E*F；

in the above formula, N is the theoretical value of post-NOx; a is the original NOx value; e is the actual NOx conversion efficiency, and the actual NOx conversion efficiency map is read according to the SCR temperature and the urea injection quantity in the SCR catalyst module; f is the ammonia storage correction efficiency, and the ammonia storage correction efficiency map is read according to the current ammonia storage amount and the exhaust flow;

filtering the NOx value of the original machine, the measured value of the rear NOx sensor and the theoretical value of the rear NOx, wherein the filtering mode is as follows:

Yn＝K*Xn+(1-K)Y_n-1；

in the above formula, Yn is the output value at the current time, Xn is the input value at the current time, Y_n-1The output value at the last moment is K, wherein K is a filter coefficient and ranges from 0 to 1;

or filtering the original machine NOx value, the measured value of the rear NOx sensor and the theoretical value of the rear NOx, wherein the filtering mode is as follows:

Yn＝(Yn-1*(a-1)+Xn)/a；

in the above formula, Yn is the output value at the current time, Xn is the input value at the current time, Y_n-1Is the output value at the last moment, a is a filter coefficient, a is an integer and a is more than or equal to 1;

2. calculating actual conversion efficiency according to the original machine NOx value and the measured value of the rear NOx sensor, wherein the actual conversion efficiency is (the original machine NOx value-the measured value of the rear NOx sensor)/the original machine NOx value;

calculating target conversion efficiency according to the original machine NOx value and the theoretical value of the rear NOx, wherein the target conversion efficiency is (the original machine NOx value-the theoretical value of the rear NOx)/the original machine NOx value;

3. judging the SCR efficiency by comparing the difference between the target conversion efficiency and the actual conversion efficiency;

if the target conversion efficiency/actual conversion efficiency is less than P1, the range of P1 is 0.4-0.98, the duration time exceeds a calibrated value t2, and the range of a calibrated value t2 is 10-3600 s, judging that the SCR efficiency is low and has a fault;

and if the target conversion efficiency/actual conversion efficiency is greater than P2, the range of P2 is 0.6-1, the duration time exceeds a calibrated value t3, and the range of the calibrated value t3 is 10-3600 s, judging that the SCR efficiency is normal.

A method for analyzing causes of SCR inefficiency, the method comprising the steps of:

1. checking whether the mass concentration of the urea is normal;

there are two methods for analyzing the mass concentration of urea, and the method 1 is as follows: measuring the mass concentration of urea according to a urea mass concentration sensor, and if the mass concentration of urea is lower than a set value L1 and the range of the set value L1 is 10% -32.5%, judging that the reason of low SCR efficiency is poor urea quality; the method 2 comprises the following steps: when the oil consumption is 5-50% higher than the rated point oil consumption of the engine; the exhaust gas flow is 5-50% larger than the exhaust gas flow of the rated point of the engine; the SCR temperature is higher than a set temperature L2, and the range of the set temperature L2 is less than 300 ℃; when the urea pump has no fault, changing the urea injection quantity to 0.8 time, 0.9 time, 1.1 time, 1.2 times and 1.3 times of the original urea injection quantity in sequence, checking the condition of SCR efficiency reduction, and if the SCR efficiency is linearly reduced, judging that the reason of low SCR efficiency is poor urea quality;

2. checking whether the urea injection control model is accurate;

after the urea mass concentration is determined to be normal, stopping injecting urea, observing the ammonia storage amount in the control model, and if the ammonia storage amount in the control model is 0, the ratio of the measured value of the rear NOx sensor to the original NOx value is smaller than a set value L3, and the range of the set value L3 is 0-0.9, judging that the reason of low SCR efficiency is inaccurate urea injection control model;

3. checking whether the SCR has crystallization fault;

after the urea mass concentration is determined to be normal and the urea injection control model is determined to be accurate, SCR crystallization analysis is carried out, and the SCR crystallization analysis needs to meet the following conditions: the oil consumption is 5-50% less than the rated point oil consumption of the engine; the exhaust gas flow is less than 5-50% of the exhaust gas flow of the rated point of the engine; the SCR temperature is lower than a set temperature L2, and the range of the set temperature L2 is lower than 300 ℃; the urea pump has no fault;

the SCR crystallization analysis is judged according to a crystallization risk coefficient CFR, and the calculation formula of the CFR is as follows:

Q_exhaust＝Mol_exhaust·C_p·T_{scr_in}；

ΔQ_urea＝Mol_urea·C_p3·ΔT₃+Mol_urea·ΔH₂+Mol_urea·ΔH₃；

in the above formula, Mol_exhaustThe amount of the exhausted substances is expressed in mol/h; c_pIn terms of specific heat capacity for vent gas, in J/mol; t is_{scr_in}Is the catalyst inlet temperature in K;

the amount of substances in the urea aqueous solution is shown as mol/h; c_p1Is the specific heat capacity of water, in J/mol; delta T₁The temperature difference of water rising from normal temperature to boiling temperature is represented by K; Δ H₁Is the molar enthalpy of water evaporation as steam, in units of J/mol; c_p2Is the specific heat capacity of water vapour, in J/mol/k; mol_ureaThe amount of urea substances in the urea aqueous solution is shown as mol/h; c_p3Is the specific heat capacity of urea, in J/mol; delta T₃The temperature difference of urea from normal temperature to decomposition temperature is represented by K; Δ H₂The molar enthalpy of urea evaporation is the molar enthalpy of urea vapor, and the unit is J/mol; Δ H₃Is the molar enthalpy of decomposition of urea vapor into ammonia gas, and the unit is J/mol;

if the CFR is smaller than the set value L4 and the range of the set value L4 is 0-30, the SCR has crystallization risk; otherwise, SCR has no crystallization risk;

adding the time at which there is a risk of crystallization to a time counter; subtracting the time at which there is no risk of crystallization from the time counter; when the SCR is in regeneration at the previous moment and the SCR regeneration at the current moment is finished, updating the time counter to be 0; when the time counter exceeds a set value L5 and the range of the set value L5 is more than 5s, judging that the reason of low SCR efficiency is the crystallization fault of SCR;

4. checking whether the SCR has sulfur poisoning fault;

after the normal mass concentration of the urea, the accurate urea injection control model and the non-crystallization fault of the SCR are determined, the main oil injection timing of the engine is delayed by 0.5-2 degrees; reducing the rail pressure of the high-pressure common rail, wherein the rail pressure is 200-2000 kpa; partially closing the throttle valve, wherein the opening degree of the throttle valve is 0% -60%; reducing the opening degree of the exhaust gas recirculation valve, wherein the opening degree of the exhaust gas recirculation valve is 0% -50%; increasing the opening of a variable turbocharger valve, wherein the opening of the variable turbocharger valve is 20-100%, or increasing the pre-injection oil quantity of an engine, the pre-injection oil quantity of the engine is 0 g/str-20 g/str to raise an exhaust temperature value to a set temperature L6, the set temperature L6 is 450-550 ℃, the time is continuously operated for a period of time, the time range is more than 30min, and if the SCR efficiency is increased by a certain amplitude, the amplitude range is more than 0.1, the reason that the SCR efficiency is low is judged to be sulfur poisoning fault of SCR;

5. checking whether the SCR catalyst is deactivated;

after determining that the mass concentration of the urea is normal, the urea injection control model is accurate, the SCR does not have crystallization fault and the SCR does not have sulfur poisoning fault, carrying out SCR catalyst inactivation analysis;

when the oil consumption is 5-50% higher than the rated point oil consumption of the engine; the exhaust gas flow is 5-50% larger than the exhaust gas flow of the rated point of the engine; the SCR temperature is higher than a set temperature L2, and the range of the set temperature L2 is less than 300 ℃; when the urea pump is not in fault, the urea injection amount is changed to be 1.05 times, 1.1 times, 1.15 times, 1.2 times, 1.25 times and 1.3 times of the original urea injection amount in sequence until the measured value of the rear NOx sensor is reduced, if the measured value of the rear NOx sensor cannot be reduced to a set value L7 and the range of the set value L7 is 0-300, the reason of low SCR efficiency is judged to be SCR catalyst deactivation.