A method for correcting SCR NH3 storage model

Abstract

The present invention discloses a method for correcting an SCR NH3 storage model, which monitors the state of the engine and the state of the exhaust system in real time, and determines whether the state of the engine and the state of the exhaust system meet the activation condition of the NH3 identification function; if the state of the engine and the state of the exhaust system meet the activation condition of the NH3 identification function at the same time, the NH3 identification function is activated; the current NH3 escape state is identified, and it is determined whether the current NH3 escape state meets the correction condition of the NH3 storage model; if the current NH3 escape state meets the correction condition of the NH3 storage model, the current NH3 storage value g is corrected to the maximum NH3 storage value g1, and the urea injection system stops or reduces injection. The method for correcting the SCR NH3 storage model designed by the present invention can correct the current NH3 storage value, and at the same time, the post-processing system performs corresponding operations to make the current NH3 storage value the same as the correction value, thereby reducing the deviation of the NH3 storage model.

Description

Technical Field

[0001] The invention relates to the technical field of diesel engine post-processing, and in particular to a method for correcting an SCR NH3 storage model. Background Art

[0002] In the current diesel engine aftertreatment, the NH3 reserves are usually calculated through the NH3 storage model. The calculation formula of the NH3 storage model is: model NH3 storage change = urea pump injection amount × conversion coefficient 1 × correction coefficient - NOX sensor × exhaust flow × NOX conversion efficiency × conversion coefficient 2 - NH3 escape value; model NH3 storage amount = model NH3 storage amount at the previous moment + model NH3 storage change; when the model NH3 storage change is a positive value, the model NH3 storage value increases, otherwise, the model NH3 storage value decreases.

[0003] The patent with application number 201911203951.8 and titled "A correction system and method for an SCR ammonia storage model" discloses a correction system and method for an SCR ammonia storage model. The system includes a DOC catalyst, an SCR catalyst, a urea tank and a controller. The outlet end of the DOC catalyst is connected to the inlet end of the SCR catalyst. A urea nozzle is provided at the connection between the DOC catalyst and the SCR catalyst. The urea tank is connected to the urea nozzle through a urea pump; a temperature sensor and a NOx sensor are provided on the SCR catalyst, and the data output ends of the temperature sensor and the NOx sensor are connected to the data input end of the controller, and the control signal output end of the controller is connected to the control signal input end of the urea pump.

[0004] The patent with application number 201710104495.6 and titled "Diesel Engine Catalytic Reduction Urea Injection Control Method Based on Real-time Ammonia Storage Management" discloses a diesel engine catalytic reduction urea injection control method based on real-time ammonia storage management: an ammonia storage calculation model is established according to the ammonia mass conservation of the SCR system to calculate the ammonia storage of the SCR at the current moment under actual working conditions; the engine NOx emission pulse spectrum, exhaust mass flow pulse spectrum and ammonia nitrogen ratio pulse spectrum are calibrated based on steady-state experiments to calculate the basic urea injection amount; the target ammonia storage area, ammonia adsorption time constant and ammonia release time constant are calibrated through experiments to calculate the corrected urea injection amount; under actual working conditions, the urea injection is controlled by the sum of the basic urea injection amount and the corrected urea injection amount, and urea slow injection and stop injection are used in conditions where the exhaust temperature suddenly increases, so that the ammonia storage of the SCR at the current moment is close to the target ammonia storage area.

[0005] In the existing technical solutions, the following problems may cause the NH3 storage model to be inaccurate. Long-term accumulation may cause the vehicle's exhaust emissions to fail to meet regulatory requirements or cause serious urea crystallization and other problems: 1. When there is a certain error in the urea injection system, the calculated urea injection amount will also have an error, resulting in a deviation in the calculated NH3 injected into the SCR carrier; 2. When there is an error in the NOx sensor, there will be an error in the calculation of the consumed NH3; 3. There is a certain deviation in the NH3 escape value model value. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology and provide a method for correcting the SCR NH3 storage model which can reduce the deviation of the NH3 storage model and solve the emission difference and urea crystallization problems.

[0007] To achieve this purpose, the method for correcting the SCR NH3 storage model designed in the present invention monitors the state of the engine and the state of the exhaust system in real time, and determines whether the state of the engine and the state of the exhaust system meet the activation condition of the NH3 identification function; if the state of the engine and the state of the exhaust system simultaneously meet the activation condition of the NH3 identification function, the NH3 identification function is activated; the current NH3 escape state is identified, and it is determined whether the current NH3 escape state meets the correction condition of the NH3 storage model; if the current NH3 escape state meets the correction condition of the NH3 storage model, the current NH3 storage value g is corrected to the maximum NH3 storage value g1, and the urea injection system stops or reduces injection.

[0008] Furthermore, the state of the engine includes the operating condition of the engine and the fuel injection amount M of the engine.

[0009] Furthermore, the activation condition of the NH3 identification function includes that the engine enters a reverse towing condition and the duration t of the reverse towing condition is greater than a set value t1.

[0010] Furthermore, the activation condition of the NH3 identification function includes that the fuel injection amount M of the engine is less than a set value M1 and the duration t is greater than a set value t1.

[0011] Furthermore, the exhaust system state includes the SCR inlet temperature T. It is necessary to ensure that the SCR inlet temperature is not lower than a set value to meet the temperature requirement of the post-treatment system.

[0012] Furthermore, the activation condition of the NH3 identification function includes that the SCR inlet temperature T is greater than a set value T1 and the duration t is greater than t1.

[0013] Furthermore, the current NH3 escape state includes a current NH3 escape value N.

[0014] Furthermore, the method for identifying the current NH3 escape value N is: monitoring the NOx concentration value of the tail exhaust NOx sensor, and the concentration value is the current NH3 escape value N.

[0015] Furthermore, the correction condition of the NH3 storage model includes that the current NH3 escape value N is greater than a set value N1 and the duration t0 is greater than a set value t2.

[0016] In summary, the method for correcting the SCR NH3 storage model described above includes the following steps:

[0017] Step 1: monitor the engine status and exhaust system status in real time to determine whether the engine status and exhaust system status meet the activation conditions of the NH3 recognition function;

[0018] Step 2: If the state of the engine and the state of the exhaust system simultaneously meet the activation conditions of the NH3 identification function, then the NH3 identification function is activated;

[0019] Step 3: Identify the current NH3 escape state and determine whether the current NH3 escape state meets the correction condition of the NH3 storage model;

[0020] Step 4: If the current NH3 escape state meets the correction condition of the NH3 storage model, the current NH3 storage value g is corrected to the maximum NH3 storage value g1, and the urea injection system stops or reduces injection.

[0021] The beneficial effects of the present invention are as follows: the method for correcting the SCR NH3 storage model designed by the present invention determines the state of the engine and the state of the exhaust system by real-time monitoring the engine operating state, the tail NOX sensor value, the ECU feedback urea injection amount, the SCR inlet temperature and the engine injection amount. When the engine state and the exhaust system state meet the correction requirements, the current NH3 storage value is corrected, and the post-processing system performs corresponding operations to make the current NH3 storage value the same as the correction value, thereby reducing the deviation of the NH3 storage model. The phenomenon of excessive NH3 storage deviation leading to emission degradation or severe crystallization is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart of the method for correcting the SCR NH3 storage model designed for the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0024] like Figure 1 The method for correcting the SCR storage NH3 model shown includes the following steps:

[0025] Step 1: Real-time monitoring of the engine status and exhaust system status, the engine status includes the engine operating conditions and the engine fuel injection amount M, and the exhaust system status includes the SCR inlet temperature T. Determine whether the engine status and the exhaust system status meet the activation conditions of the NH3 identification function, the activation conditions of the NH3 identification function include: 1. The engine enters the reverse drag condition and the duration t of the reverse drag condition is greater than the set value t1; 2. The engine fuel injection amount M is less than the set value M1 and the duration t is greater than the set value t1; 3. The SCR inlet temperature T is greater than the set value T1 and the duration t is greater than t1.

[0026] Step 2: If the state of the engine and the state of the exhaust system simultaneously meet the activation conditions of the NH3 identification function, then the NH3 identification function is activated;

[0027] Step 3: Identify the current NH3 escape state, which includes the current NH3 escape value N. The method for identifying the current NH3 escape value N is: monitor the NOx concentration value of the tail NOx sensor, which is the current NH3 escape value N. Determine whether the current NH3 escape state meets the correction condition of the NH3 storage model. The correction condition of the NH3 storage model includes that the current NH3 escape value N is greater than the set value N1 and the duration t0 is greater than the set value t2.

[0028] Step 4: If the current NH3 escape state meets the correction condition of the NH3 storage model, the current NH3 storage value g is corrected to the maximum NH3 storage value g1, and the urea injection system stops or reduces injection.

[0029] The method for correcting the SCR NH3 storage model designed by the present invention judges the state of the engine and the state of the exhaust system by real-time monitoring the engine operating state, the NOX concentration value of the tail NOX sensor, the urea injection amount fed back by the ECU, the SCR inlet temperature and the engine fuel injection amount. When the state of the engine and the exhaust system meet the correction requirements, the current NH3 storage value is corrected, and the post-processing system performs corresponding operations to make the current NH3 storage value the same as the correction value, thereby reducing the deviation of the NH3 storage model. The phenomenon of excessive NH3 storage deviation leading to emission degradation or severe crystallization is avoided.

[0030] Here, it should be noted that the description of the above technical solutions is exemplary, and this specification can be embodied in different forms and should not be interpreted as being limited to the technical solutions set forth herein. On the contrary, providing these descriptions will make the disclosure of the present invention thorough and complete, and will fully convey the scope disclosed in this specification to those skilled in the art. In addition, the technical solution of the present invention is limited only by the scope of the claims. The shapes, sizes, ratios, angles and numbers disclosed in various aspects used to describe this specification and claims are merely examples, and therefore, this specification and claims are not limited to the details shown. In the following description, when a detailed description of a related known function or configuration is determined to be unnecessarily obscuring the focus of this specification and claims, the detailed description will be omitted. In the case of using "including", "having" and "comprising" described in this specification, another part or other parts may also be present, and the terms used may generally be singular but may also represent plural forms.

[0031] Finally, it should be pointed out that the above embodiments are only representative examples of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention should be considered to belong to the protection scope of the present invention.

Claims

1. A method for correcting an SCR NH3 storage model, characterized in that: Monitor the state of the engine and the state of the exhaust system in real time, and determine whether the state of the engine and the state of the exhaust system meet the activation conditions of the NH3 identification function; if the state of the engine and the state of the exhaust system meet the activation conditions of the NH3 identification function at the same time, activate the NH3 identification function; identify the current NH3 escape state, and determine whether the current NH3 escape state meets the correction conditions of the NH3 storage model; if the current NH3 escape state meets the correction conditions of the NH3 storage model, correct the current NH3 storage value g to the maximum NH3 storage value g1, and stop or reduce the urea injection system.

2. The method for correcting the SCR storage NH3 model according to claim 1, characterized in that: The state of the engine includes the operating condition of the engine and the fuel injection amount M of the engine.

3. The method for correcting the SCR storage NH3 model according to claim 2, characterized in that: The activation condition of the NH3 identification function includes that the engine enters a reverse towing condition and the duration t of the reverse towing condition is greater than a set value t1.

4. The method for correcting the SCR storage NH3 model according to claim 3, characterized in that: The activation condition of the NH3 recognition function includes that the fuel injection amount M of the engine is less than a set value M1 and the duration t is greater than a set value t1.

5. The method for correcting the SCR storage NH3 model according to claim 4, characterized in that: The exhaust system state includes the SCR inlet temperature T.

6. The method for correcting the SCR storage NH3 model according to claim 5, characterized in that: The activation conditions of the NH3 recognition function include that the SCR inlet temperature T is greater than a set value T1 and the duration t is greater than t1.

7. The method for correcting the SCR storage NH3 model according to claim 1, characterized in that: The current NH3 escape state includes a current NH3 escape value N.

8. The method for correcting the SCR storage NH3 model according to claim 7, characterized in that: The method for identifying the current NH3 escape value N is: monitoring the NOx concentration value of the tail exhaust NOx sensor, and the concentration value is the current NH3 escape value N.

9. The method for correcting the SCR storage NH3 model according to claim 8, characterized in that: The correction conditions of the NH3 storage model include that the current NH3 escape value N is greater than a set value N1 and the duration t0 is greater than a set value t2.

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