Method for controlling emission peak value of oxynitride of diesel engine

Abstract

The invention discloses a diesel engine oxynitride emission peak value control method which comprises the following steps that dynamic parameters of an engine are obtained, and the dynamic parameters are loads or supercharging pressure; judging whether the dynamic parameter is greater than a corresponding preset threshold value or not; in response to the condition that at least one dynamic parameter is greater than a corresponding preset threshold value, determining a dynamic correction coefficient of the dynamic parameter based on dynamic detection of the corresponding dynamic parameter; the maximum oxygen concentration measured by the rack is obtained, and the instantaneous required air inflow of the corresponding working condition is calculated; according to the instantaneous required air inflow and the dynamic correction coefficient, the actual required air inflow is obtained through calculation; and controlling the air inflow of the engine according to the actual required air flow. The nitrogen and oxygen emission of the engine under the violent variable working condition can be reduced, and the stability of the nitrogen and oxygen value is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of diesel engine nitrogen oxide emission peak control, and in particular relates to a diesel engine nitrogen oxide emission peak control method, device and medium. Background Art

[0002] In order to meet the requirements of the national standard "GB17691-2018 Emission limits and test methods for diesel engine nitrogen oxides", the National VI diesel engine uses a selective catalytic reducer (SCR). The SCR system injects a reductant based on the real-time nitrogen oxide value measured by the nitrogen oxide sensor. The reductant is usually urea, which generates harmless nitrogen and water through a catalytic reduction reaction, thereby reducing pollution to the environment.

[0003] The control logic of the SCR system is: the nitrogen oxide value measured by the front nitrogen oxide sensor is used as the input of the electronic control unit, and the SCR injects urea solution according to the corresponding calibration logic to catalyze the reduction reaction with nitrogen oxides to reduce nitrogen oxide emissions. The rear nitrogen oxide sensor further measures the final emitted nitrogen oxide value to evaluate the capability of the SCR.

[0004] However, if the engine is under drastic operating conditions, the nitrogen oxide value will be several times higher than normal operation, and the SCR's processing capacity is far from enough at this time. Summary of the invention

[0005] In order to solve the problem that the nitrogen oxide value of the existing engine will exceed the standard under drastic operating conditions, the present invention proposes a control method for the diesel engine nitrogen oxide emission peak value, which can reduce the engine's nitrogen oxide emissions under drastic operating conditions and improve the stability of the nitrogen oxide value.

[0006] The objective of the present invention is achieved through the following technical solutions: The first aspect of the present invention discloses a method for controlling a peak value of nitrogen oxide emissions from a diesel engine, comprising the following steps: Obtaining a dynamic parameter of the engine, wherein the dynamic parameter is load or boost pressure; Determining whether the dynamic parameter is greater than a corresponding preset threshold; In response to at least one dynamic parameter being greater than a corresponding preset threshold, determining a dynamic correction coefficient of the dynamic parameter based on dynamic detection of the corresponding dynamic parameter; Obtain the maximum oxygen concentration measured on the bench and calculate the instantaneous required air intake volume for the corresponding working conditions; The actual required air volume is calculated according to the instantaneous required air volume and the dynamic correction coefficient; The engine air intake volume is controlled according to the actual required air volume.

[0007] The second aspect of the present invention discloses a control device for a diesel engine nitrogen oxide emission peak, comprising a memory and a controller that are communicatively connected in sequence, wherein a computer program is stored in the memory, and the controller is used to read the computer program and execute a diesel engine nitrogen oxide emission peak control method described in the first aspect.

[0008] A third aspect of the present invention discloses a computer-readable storage medium having instructions stored thereon. When the instructions are executed on a computer, the method for controlling a diesel engine nitrogen oxide emission peak value described in the first aspect is executed.

[0009] The beneficial effects of the present invention are: The present invention monitors dynamic parameters, and when the dynamic parameters are greater than preset values, determines the dynamic correction coefficients thereof, further calculates the required intake air volume at the moment, optimizes combustion, thereby reducing the NOx peak, and makes the WHTC cycle emissions meet the national regulatory limits. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0011] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0013] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0014] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0015] The first aspect of the present invention discloses a method for controlling the peak value of nitrogen oxide emissions from a diesel engine, which includes steps S1 to S7. It should be noted that the step identifiers in this scheme are only for the convenience of explaining the method and do not constitute a limitation on the order of precedence. The order of each step is based on its language description and the order of each signal.

[0016] Step S1, obtaining dynamic parameters of the engine, where the dynamic parameters are load or boost pressure.

[0017] Specifically, the load includes engine speed, accelerator pedal, and fuel injection amount. For example, to improve the accuracy of nitrogen oxide emission control, the above three load parameters are detected simultaneously during the control process.

[0018] Step S2: determine whether the dynamic parameter is greater than a corresponding preset threshold.

[0019] Step S3: in response to at least one dynamic parameter being greater than a corresponding preset threshold, determining a dynamic correction coefficient of the dynamic parameter based on dynamic detection of the corresponding dynamic parameter.

[0020] Specifically, if the dynamic parameter is load, when at least one of the engine speed, the accelerator pedal, and the fuel injection amount is greater than its corresponding threshold value, the dynamic correction coefficient of the dynamic parameter is determined based on the dynamic detection of the corresponding dynamic parameter. At this time, the dynamic correction coefficient of the dynamic parameter is determined based on the dynamic detection of the corresponding dynamic parameter as follows: first, the engine speed change rate, the accelerator pedal change rate, and the fuel injection amount change rate are calculated respectively; then the maximum value of the engine speed change rate, the accelerator pedal change rate, and the fuel injection amount change rate is used as the load change rate; then the dynamic correction factor is calculated and output based on the load change rate; and finally the dynamic correction coefficient is determined based on the dynamic correction factor.

[0021] If the dynamic parameter is boost pressure, when the boost pressure is greater than its corresponding threshold, a dynamic correction factor is calculated and output based on dynamic authentication of the boost pressure deviation; and a dynamic correction coefficient is determined based on the dynamic correction factor.

[0022] Step S4: Obtain the maximum oxygen concentration measured by the test bench and calculate the instantaneous required air intake volume corresponding to the working condition.

[0023] Step S5: Calculate the actual required air volume according to the instantaneous required air volume and the dynamic correction coefficient.

[0024] Step S6: controlling the engine air intake according to the actual required air volume.

[0025] Step S7, obtaining the real-time nitrogen oxide value in the nitrogen oxide emissions, and determining whether the real-time nitrogen oxide value is less than or equal to the standard threshold; if the real-time nitrogen oxide value is greater than the standard threshold, determining the dynamic correction coefficient of the dynamic parameter based on the dynamic detection of the corresponding dynamic parameter; if the real-time nitrogen oxide value is less than or equal to the standard threshold, then ending.

[0026] The method of the present invention calculates a dynamic correction factor by detecting changes in relevant dynamic parameters when the engine is running under variable operating conditions. The required intake air volume at this moment is further calculated based on the dynamic correction factor and the maximum oxygen content, thereby optimizing combustion and reducing the NOx peak value, so that the WHTC cycle nitrogen oxide emissions meet the national regulatory limits.

[0027] The second aspect of the present invention discloses a control device for the peak value of nitrogen oxide emission of a diesel engine, comprising a memory and a controller which are sequentially connected in communication, wherein a computer program is stored on the memory, and the controller is used to read the computer program and execute a control method for the peak value of nitrogen oxide emission of a diesel engine described in the second aspect. Specifically, the memory may include, but is not limited to, a random access memory (RAM), a read-only memory (ROM), a flash memory (Flash Memory), a first-in-first-out memory (FIFO) and / or a first-in-last-out memory (FILO), etc.; the controller may not be limited to a microcontroller of the STM32F105 series. In addition, the computer device may also include, but is not limited to, a power supply unit, a display screen and other necessary components.

[0028] A third aspect of the present invention discloses a computer-readable storage medium having instructions stored thereon. When the instructions are executed on a computer, the method for controlling a diesel engine nitrogen oxide emission peak value described in the first aspect is executed.

[0029] The operating principles of the devices and media disclosed in the second and third aspects of the present invention are detailed in the first aspect and will not be elaborated here.

[0030] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A method for controlling the peak value of nitrogen oxide emissions from a diesel engine, characterized in that: The following steps are involved: Obtaining a dynamic parameter of the engine, wherein the dynamic parameter is load or boost pressure; Determining whether the dynamic parameter is greater than a corresponding preset threshold; In response to at least one dynamic parameter being greater than a corresponding preset threshold, determining a dynamic correction coefficient of the dynamic parameter based on dynamic detection of the corresponding dynamic parameter; Obtain the maximum oxygen concentration measured on the bench and calculate the instantaneous required air intake volume for the corresponding working conditions; The actual required air volume is calculated according to the instantaneous required air volume and the dynamic correction coefficient; The engine air intake volume is controlled according to the actual required air volume.

2. A method for controlling the peak value of nitrogen oxide emissions from a diesel engine according to claim 1, characterized in that: The dynamic parameter is load, which includes engine speed, accelerator pedal, and fuel injection amount; The dynamic correction coefficient of the dynamic parameter determined based on the dynamic detection of the corresponding dynamic parameter includes: Calculate the engine speed change rate, accelerator pedal change rate, and fuel injection amount change rate respectively; The maximum value among the engine speed change rate, the accelerator pedal change rate and the fuel injection amount change rate is taken as the load change rate; Calculating an output dynamic correction factor based on the load change rate; A dynamic correction coefficient is determined based on the dynamic correction factor.

3. The method for controlling the peak value of nitrogen oxide emissions from a diesel engine according to claim 1, characterized in that: The dynamic parameter is the boost pressure, and the dynamic correction coefficient of the dynamic parameter is determined based on the dynamic detection of the corresponding dynamic parameter, including: Based on the dynamic certification of boost pressure deviation, the dynamic correction factor is calculated and output; A dynamic correction coefficient is determined based on the dynamic correction factor.

4. The method for controlling the peak value of nitrogen oxide emissions from a diesel engine according to claim 1, characterized in that: After controlling the engine air intake according to the actual required air volume, the method further includes: Get real-time NOx values ​​in NOx emissions, Determining whether the real-time nitrogen and oxygen value is less than or equal to a standard threshold; In response to the real-time nitrogen and oxygen value being greater than a standard threshold, a dynamic correction coefficient of the dynamic parameter is determined based on dynamic detection of the corresponding dynamic parameter.

5. A control device for the peak value of nitrogen oxide emission of a diesel engine, characterized in that: It comprises a memory and a controller which are communicatively connected in sequence, wherein the memory stores a computer program, and the controller is used to read the computer program and execute a method for controlling a nitrogen oxide emission peak of a diesel engine as claimed in any one of claims 1 to 4.

6. A computer-readable storage medium having instructions stored thereon, characterized in that: When the instructions are executed on a computer, a method for controlling a diesel engine nitrogen oxide emission peak value as described in any one of claims 1 to 4 is executed.