Ammonia demand determination method, control method, controller and SCR system

Abstract

The present application provides a method for determining ammonia demand, a control method, a controller, and an SCR system. The method includes: obtaining a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient; determining an ammonia demand correction value based on the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient; obtaining a base ammonia demand value; and determining a final ammonia demand value based on the ammonia demand correction value and the base ammonia demand value. By adaptively adjusting the ammonia demand and the required injection amount based on the NH3 sensor signal, the calculation process is simplified, control accuracy is improved, and the low accuracy of determining ammonia demand in existing solutions is addressed.

Description

Technical Field

[0001] The present application relates to the technical field of SCR systems, and in particular to a method for determining an ammonia demand, a control method, a controller, and an SCR system. Background Art

[0002] In diesel engine aftertreatment, SCR (Sensor-Controlled Reactor) reduces environmentally harmful NOx in exhaust gas to N2. For ultra-low NOx emissions and future China VII emission standards, NH3 sensors are the preferred solution for achieving consistent emissions. However, existing solutions can lead to excessive urea consumption and ammonia leaks. Summary of the Invention

[0003] The main purpose of this application is to provide a method for determining ammonia demand, a control method, a controller and an SCR system to solve the problem of low accuracy in determining ammonia demand in existing solutions.

[0004] According to one aspect of an embodiment of the present invention, a method for determining an ammonia demand is provided, the method comprising: obtaining a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient, wherein the required injection amount of the front-stage SCR is used to characterize the required ammonia injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the required ammonia injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the rear-stage SCR; determining an ammonia demand correction value based on the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient; obtaining a basic value of the ammonia demand; and determining a final ammonia demand based on the ammonia demand correction value and the basic value of the ammonia demand.

[0005] Optionally, obtaining the pre-stage correction coefficient includes: obtaining the mass flow rate of the pre-stage SCR ammonia, the mass flow rate of the pre-stage SCR nitrogen oxides, the air flow rate and the current temperature, the current temperature being used to characterize the temperature in the SCR system at the current moment, and the air flow rate being used to characterize the air flow rate in the SCR system at the current moment; and determining the pre-stage correction coefficient according to the mass flow rate of the pre-stage SCR ammonia, the mass flow rate of the pre-stage SCR nitrogen oxides, the air flow rate and the current temperature.

[0006] Optionally, obtaining the post-stage correction coefficient includes: obtaining the mass flow rate of post-stage SCR ammonia, the mass flow rate of post-stage SCR nitrogen oxides, the air flow rate and the current temperature, the current temperature being used to characterize the temperature in the SCR system at the current moment, and the air flow rate being used to characterize the air flow rate in the SCR system at the current moment; and determining the post-stage correction coefficient according to the mass flow rate of the post-stage SCR ammonia, the mass flow rate of the post-stage SCR nitrogen oxides, the air flow rate and the current temperature.

[0007] Optionally, an ammonia demand correction value is determined based on the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient and the rear-stage correction coefficient, including: determining the ammonia demand correction value according to Qx=fac1×Q1+fac2×Q2, Qx is the ammonia demand correction value, fac1 is the front-stage correction coefficient, Q1 is the required injection amount of the front-stage SCR, fac2 is the rear-stage correction coefficient, and Q2 is the required injection amount of the rear-stage SCR.

[0008] Optionally, the final ammonia demand is determined according to the ammonia demand correction value and the basic value of the ammonia demand, including: determining the final ammonia demand according to Q=fac1×Q1+fac2×Q2+Qbas, where Q is the final ammonia demand, fac1 is the front-stage correction coefficient, Q1 is the required injection amount of the front-stage SCR, fac2 is the rear-stage correction coefficient, Q2 is the required injection amount of the rear-stage SCR, and Qbas is the basic value of the ammonia demand.

[0009] Optionally, obtaining a basic value of ammonia demand includes: obtaining the mass flow rate of exhaust gas from the SCR system, the ratio of ammonia in the SCR system to hydroxide in the SCR system, the concentration of nitrogen oxides in the SCR system, and a total efficiency value, wherein the total efficiency value is used to characterize the gas conversion efficiency of the SCR system; and determining the basic value of ammonia demand based on the mass flow rate of exhaust gas from the SCR system, the ratio of ammonia in the SCR system to hydroxide in the SCR system, the concentration of nitrogen oxides in the SCR system, and the total efficiency value.

[0010] Optionally, the basic value of the ammonia demand is determined according to the mass flow rate of the exhaust gas of the SCR system, the ratio of ammonia of the SCR system to hydroxide of the SCR system, and the concentration of nitrogen oxides of the SCR system, including: determining the basic value of the ammonia demand according to Qbas=ConcNOx×η×ANR×MExh×C, where Qbas is the basic value of the ammonia demand, ConcNOx is the concentration of nitrogen oxides of the SCR system, η is the total efficiency value, ANR is the ratio of ammonia of the SCR system to hydroxide of the SCR system, MExh is the mass flow rate of the exhaust gas of the SCR system, and C is the gas molar coefficient.

[0011] According to another aspect of an embodiment of the present invention, a method for controlling ammonia demand is also provided, the method comprising: determining a final ammonia demand using any one of the methods for determining ammonia demand; and controlling the filling of ammonia in the final ammonia demand into the SCR system based on the final ammonia demand.

[0012] According to another aspect of an embodiment of the present invention, a controller is also provided, which includes a first acquisition unit, a first determination unit, a second acquisition unit and a second determination unit; the first acquisition unit is used to acquire the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient and the rear-stage correction coefficient, the required injection amount of the front-stage SCR is used to characterize the ammonia required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the ammonia required injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the rear-stage SCR; the first determination unit is used to determine the ammonia demand correction value based on the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient and the rear-stage correction coefficient; the second acquisition unit is used to acquire the basic value of the ammonia demand; the second determination unit is used to determine the final ammonia demand based on the ammonia demand correction value and the basic value of the ammonia demand.

[0013] According to another aspect of an embodiment of the present invention, an SCR system is also provided, which includes a controller, a front-stage SCR, a rear-stage SCR, a front-stage nitrogen oxide sensor, a rear-stage nitrogen oxide sensor and an ammonia sensor. The rear end of the front-stage SCR and the front end of the rear-stage SCR are connected through a connecting pipe. The ammonia sensor is installed on the inner wall of the connecting pipe. The front-stage nitrogen oxide sensor is installed to the front end of the front-stage SCR, the rear-stage nitrogen oxide sensor is installed to the rear end of the rear-stage SCR, and the ammonia sensor is installed to the front end of the rear-stage SCR. The front-stage nitrogen oxide sensor, the rear-stage nitrogen oxide sensor and the ammonia sensor communicate with the controller respectively, and the controller is used to execute any one of the methods for determining the ammonia demand.

[0014] In the embodiment of the present invention, the NH3 sensor signal is adaptively adjusted to the ammonia demand and the required injection amount, thereby simplifying the calculation process and improving the control accuracy, thereby solving the problem of low accuracy in determining the ammonia demand in the existing solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0016] Figure 1 A flow chart showing a method for determining ammonia demand according to an embodiment of the present application is shown;

[0017] Figure 2 A flowchart of obtaining a basic value of ammonia demand according to an embodiment of the present application is shown;

[0018] Figure 3 A flow chart showing a method for controlling ammonia demand according to an embodiment of the present application is shown;

[0019] Figure 4 A schematic diagram of a controller according to an embodiment of the present application is shown;

[0020] Figure 5 A schematic diagram of an SCR system according to an embodiment of the present application is shown;

[0021] Figure 6 The figure shows the relationship between the main input and output and conversion efficiency of SCR and ASC according to the present application.

[0022] The above drawings include the following reference numerals:

[0023] 100, controller; 210, front-stage SCR; 220, rear-stage SCR; 230, front-stage NOx sensor; 240, rear-stage NOx sensor; 250, ammonia sensor; 260, front-stage temperature sensor; 270, urea nozzle; 280, rear-stage temperature sensor; 290, ammonia slip catalyst; 310, engine; 320, front-end oxidation catalyst; 330, front-end SCR; 340, oxidation catalyst; 350, particulate filter. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the 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. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element or intervening elements may be present. Moreover, in the specification and claims, when it is described that an element is "connected to" another element, the element may be "directly connected to" the other element or "connected to" the other element through a third element.

[0028] For ease of description, some nouns or terms involved in the embodiments of the present application are explained below:

[0029] As mentioned in the background technology, the SCR (Sensor-Controlled Reactor) in diesel engine aftertreatment is responsible for reducing environmentally harmful NOx in exhaust gas to N2. For ultra-low NOx emissions and future China VII emissions standards, NH3 sensors are the preferred solution for achieving consistent emissions. However, existing solutions can easily lead to excessive urea consumption, which can cause ammonia leakage. To address the low accuracy of ammonia demand determination in existing solutions, a typical embodiment of the present application provides a method for determining ammonia demand, a control method, a controller, and an SCR system.

[0030] According to an embodiment of the present application, a method for determining ammonia demand is provided.

[0031] Figure 1 Flowchart of the method for determining the ammonia demand according to an embodiment of the present application. Figure 1 As shown, the method includes the following steps:

[0032] Step S101, obtaining a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient, wherein the required injection amount of the front-stage SCR is used to characterize the required ammonia injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the required ammonia injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the rear-stage SCR;

[0033] In one embodiment of the present application, obtaining the pre-stage correction coefficient includes: obtaining the mass flow rate of the pre-stage SCR ammonia, the mass flow rate of the pre-stage SCR nitrogen oxides, the air flow rate and the current temperature, the above-mentioned current temperature is used to characterize the temperature in the SCR system at the current moment, and the above-mentioned air flow rate is used to characterize the air flow rate in the above-mentioned SCR system at the current moment; and determining the above-mentioned pre-stage correction coefficient according to the mass flow rate of the above-mentioned pre-stage SCR ammonia, the mass flow rate of the above-mentioned pre-stage SCR nitrogen oxides, the above-mentioned air flow rate and the above-mentioned current temperature.

[0034] In one embodiment of the present application, obtaining the post-stage correction coefficient includes: obtaining the mass flow rate of post-stage SCR ammonia, the mass flow rate of post-stage SCR nitrogen oxides, the air flow rate and the current temperature, the above-mentioned current temperature is used to characterize the temperature in the SCR system at the current moment, and the above-mentioned air flow rate is used to characterize the air flow rate in the above-mentioned SCR system at the current moment; and determining the above-mentioned post-stage correction coefficient according to the mass flow rate of the above-mentioned post-stage SCR ammonia, the mass flow rate of the above-mentioned post-stage SCR nitrogen oxides, the above-mentioned air flow rate and the above-mentioned current temperature.

[0035] Correction coefficient fac1 of SCR1's NH3 required injection amount: Under transient operating conditions, the ammonia storage set value will not change in a short period of time, so transient correction is required for the urea injection amount. The transient correction coefficient fac1 is determined by the NH3 mass flow measured by the NH3 sensor, the NOx mass flow calculated by the model, the air flow rate, and the current temperature.

[0036] Correction factor fac2 for the required NH3 injection amount of SCR2: Under transient operating conditions, the downstream NOx sensor and NH3 sensor, as well as the model NOx, air flow velocity, and current temperature jointly determine the transient correction factor fac2.

[0037] Step S102, determining an ammonia demand correction value based on the required injection amount of the preceding SCR, the required injection amount of the succeeding SCR, the preceding correction coefficient, and the succeeding correction coefficient;

[0038] In one embodiment of the present application, an ammonia demand correction value is determined based on the required injection amount of the above-mentioned front-stage SCR, the required injection amount of the above-mentioned rear-stage SCR, the above-mentioned front-stage correction coefficient and the above-mentioned rear-stage correction coefficient, including: determining the above-mentioned ammonia demand correction value according to Qx=fac1×Q1+fac2×Q2, Qx is the above-mentioned ammonia demand correction value, fac1 is the above-mentioned front-stage correction coefficient, Q1 is the required injection amount of the above-mentioned front-stage SCR, fac2 is the above-mentioned rear-stage correction coefficient, and Q2 is the required injection amount of the above-mentioned rear-stage SCR.

[0039] Step S103, obtaining a basic value of ammonia demand;

[0040] Get the average temperature of SCR according to the upstream and downstream temperature sensors of SCR, and take the average of upstream and downstream temperatures;

[0041] The NOx mass flow rate is obtained by multiplying the NOx percentage measured by the NOx sensor upstream of the SCR by the exhaust gas mass flow rate;

[0042] According to the front-stage SCR kinetic model and the rear-stage SCR kinetic model, the NOx values ​​of the front-stage SCR and the rear-stage SCR upstream and downstream are obtained respectively. The reaction efficiency of the model is calculated based on the upstream and downstream NOx values:

[0043] η1 or η2 = 1-NOxDs / NOxUs; NOxDs is the downstream NOx concentration, NOxUs is the upstream NOx concentration

[0044] The front-stage SRC efficiency η1 and the rear-stage SRC efficiency η2 are used to calculate the total efficiency of the SCR system according to the following formula:

[0045] η=1-(1-η1)×(1-η2);

[0046] Therefore, the SCR pre-control module obtains the basic value of NH3 demand based on SCR pre-control Qbas according to the NOx mass flow rate upstream of the SCR, the total SCR efficiency, the exhaust gas mass flow rate and the average temperature:

[0047] In one embodiment of the present application, Figure 2 As shown, obtain the basic value of ammonia demand, including:

[0048] Step S1031, obtaining the mass flow rate of exhaust gas from the SCR system, the ratio of ammonia gas to hydroxide in the SCR system, the concentration of nitrogen oxides in the SCR system, and the total efficiency value, where the total efficiency value is used to characterize the gas conversion efficiency of the SCR system;

[0049] Step S1032: determining a basic value of the ammonia demand according to the mass flow of the exhaust gas of the SCR system, the ratio of ammonia of the SCR system to hydroxide of the SCR system, the concentration of nitrogen oxides of the SCR system, and the total efficiency value.

[0050] First confirm the feedforward value and give an approximate range to improve the accuracy of control.

[0051] In one embodiment of the present application, the basic value of the ammonia demand is determined according to the mass flow rate of the exhaust gas of the above-mentioned SCR system, the ratio of ammonia of the above-mentioned SCR system to the hydroxide of the above-mentioned SCR system, and the concentration of nitrogen oxides of the above-mentioned SCR system, including: determining the basic value of the above-mentioned ammonia demand according to Qbas=ConcNOx×η×ANR×MExh×C, where Qbas is the basic value of the above-mentioned ammonia demand, ConcNOx is the concentration of nitrogen oxides of the above-mentioned SCR system, η is the above-mentioned total efficiency value, ANR is the ratio of ammonia of the above-mentioned SCR system to the hydroxide of the above-mentioned SCR system, MExh is the mass flow rate of the exhaust gas of the above-mentioned SCR system, and C is the gas molar coefficient.

[0052] Step S104: determining a final ammonia demand based on the ammonia demand correction value and the basic value of the ammonia demand.

[0053] In the above steps, the NH3 sensor signal is adaptively adjusted to the ammonia demand and the required injection amount, thereby simplifying the calculation process and improving the control accuracy, thereby solving the problem of low accuracy in determining the ammonia demand in the existing solution.

[0054] In one embodiment of the present application, the final ammonia demand is determined according to the above-mentioned ammonia demand correction value and the above-mentioned ammonia demand basic value, including: determining the above-mentioned final ammonia demand according to Q=fac1×Q1+fac2×Q2+Qbas, where Q is the above-mentioned final ammonia demand, fac1 is the above-mentioned front-stage correction coefficient, Q1 is the required injection amount of the above-mentioned front-stage SCR, fac2 is the above-mentioned rear-stage correction coefficient, Q2 is the required injection amount of the above-mentioned rear-stage SCR, and Qbas is the above-mentioned basic value of the ammonia demand.

[0055] Required NH3 injection amount before SCR: The mass flow rates of NO, NO2, and NOx upstream of SCR1 are obtained based on the NOx sensor upstream of SCR; the mass flow rate of NH3 upstream of SCR1 is obtained based on the urea supply system; the model calculation efficiency of the pre-stage SCR, the model calculation ammonia storage, and the model NO, NO2, NOx, and NH3 mass flow rates output by the pre-stage SCR are obtained from the pre-stage SCR kinetic module based on the exhaust gas mass flow rate, the upstream temperature of SCR1, and the mass flow rates of NO, NO2, and NH3 upstream of SCR.

[0056] Pre-stage SCR ammonia storage set value: The calculation of the ammonia storage set value of SCR1 needs to consider: the deviation between the NH3 sensor measurement value and the SCR kinetic model NH3 value is calculated to obtain the correction factor of the model NH3 calculation, and the output NO, NO2, NOx and NH3 are corrected in the kinetic model calculation, and the reaction efficiency and ammonia storage of the pre-stage SCR are corrected to improve the accuracy of the model calculation; under steady-state conditions, when the NH3 sensor value is greater than a certain value, it is necessary to recalculate the set ammonia storage at different temperatures. The ammonia storage at the corresponding temperature at this time can be used as the ammonia storage set value of the pre-stage SCR, and the corresponding NH3 demand injection amount Q1 is calculated.

[0057] Ammonia storage difference ΔR1 = set ammonia storage (TUS) - actual ammonia storage; Q1 = F(ΔR1); F is a function of the ammonia storage difference, generally obtained by fitting experimental data.

[0058] Post-stage SCR Ammonia Reserve Setpoint: The post-stage SCR ammonia reserve setpoint is the feedforward setpoint plus the NH3 sensor measurement value, which is integrated and fed back to determine the post-stage SCR injection quantity Q2. ΔR2 = Setpoint Ammonia Reserve - Actual Ammonia Reserve; R2 Actual Ammonia Reserve = Avrg(∫(MNH3 - MNOx) / RMaxdt, R model ammonia reserve), where MNH3 is the ammonia mass flow rate, MNOx is the nitrogen oxide mass flow rate, and Avrg represents the average value. Q2 = F(ΔR2), where RMaxdt is the maximum RMax ammonia reserve and dt is the time derivative.

[0059] When ammonia storage is high, the downstream NOx value is used to correct the urea injection amount.

[0060] This application also provides a method for controlling ammonia demand, such as Figure 3 As shown, the method includes the following steps:

[0061] Step S301: Determine the final ammonia demand using any method for determining the ammonia demand;

[0062] Step S302: According to the above-mentioned final ammonia demand, controlling the charging of ammonia of the above-mentioned final ammonia demand into the SCR system.

[0063] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0064] The present embodiment further provides a controller. It should be noted that the controller of the present embodiment can be used to execute the method for determining the ammonia demand provided in the present embodiment. The controller provided in the present embodiment is introduced below.

[0065] Figure 4 Schematic diagram of a controller according to an embodiment of the present application. Figure 4 As shown, the controller includes a first acquisition unit 41, a first determination unit 42, a second acquisition unit 43 and a second determination unit 44; the first acquisition unit 41 is used to acquire the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient and the rear-stage correction coefficient, the required injection amount of the above-mentioned front-stage SCR is used to characterize the required ammonia injection amount of the above-mentioned front-stage SCR, the required injection amount of the above-mentioned rear-stage SCR is used to characterize the required ammonia injection amount of the above-mentioned rear-stage SCR, the above-mentioned front-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the above-mentioned front-stage SCR, and the above-mentioned rear-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the above-mentioned rear-stage SCR; the first determination unit 42 is used to determine the ammonia demand correction value according to the required injection amount of the above-mentioned front-stage SCR, the required injection amount of the above-mentioned rear-stage SCR, the above-mentioned front-stage correction coefficient and the above-mentioned rear-stage correction coefficient; the second acquisition unit 43 is used to acquire the basic value of the ammonia demand; the second determination unit 44 is used to determine the final ammonia demand according to the above-mentioned ammonia demand correction value and the above-mentioned basic value of the ammonia demand.

[0066] In the above controller, the NH3 sensor signal is adaptively adjusted to the ammonia demand and the required injection amount, thereby simplifying the calculation process and improving the control accuracy, thereby solving the problem of low accuracy in determining the ammonia demand in the existing solution.

[0067] In one embodiment of the present application, the first acquisition unit includes a first acquisition module and a first determination module. The first acquisition module is used to obtain the mass flow rate of the pre-stage SCR ammonia, the mass flow rate of the pre-stage SCR nitrogen oxides, the air flow rate and the current temperature. The above-mentioned current temperature is used to characterize the temperature in the SCR system at the current moment, and the above-mentioned air flow rate is used to characterize the air flow rate in the above-mentioned SCR system at the current moment; the first determination module is used to determine the above-mentioned pre-stage correction coefficient based on the mass flow rate of the above-mentioned pre-stage SCR ammonia, the mass flow rate of the above-mentioned pre-stage SCR nitrogen oxides, the above-mentioned air flow rate and the above-mentioned current temperature.

[0068] In one embodiment of the present application, the first acquisition unit includes a second acquisition module and a second determination module, the second acquisition module is used to obtain the mass flow rate of the post-stage SCR ammonia, the mass flow rate of the post-stage SCR nitrogen oxides, the air flow rate and the current temperature, the above-mentioned current temperature is used to characterize the temperature in the SCR system at the current moment, and the above-mentioned air flow rate is used to characterize the air flow rate in the above-mentioned SCR system at the current moment; the second determination module is used to determine the above-mentioned post-stage correction coefficient based on the mass flow rate of the above-mentioned post-stage SCR ammonia, the mass flow rate of the above-mentioned post-stage SCR nitrogen oxides, the above-mentioned air flow rate and the above-mentioned current temperature.

[0069] In one embodiment of the present application, the first determination unit includes a third determination module, which is used to determine the above-mentioned ammonia demand correction value according to Qx=fac1×Q1+fac2×Q2, where Qx is the above-mentioned ammonia demand correction value, fac1 is the above-mentioned front-stage correction coefficient, Q1 is the required injection amount of the above-mentioned front-stage SCR, fac2 is the above-mentioned rear-stage correction coefficient, and Q2 is the required injection amount of the above-mentioned rear-stage SCR.

[0070] In one embodiment of the present application, the second determination unit includes a fourth determination module, which is used to determine the above-mentioned final ammonia demand according to Q=fac1×Q1+fac2×Q2+Qbas, where Q is the above-mentioned final ammonia demand, fac1 is the above-mentioned front-stage correction coefficient, Q1 is the required injection amount of the above-mentioned front-stage SCR, fac2 is the above-mentioned rear-stage correction coefficient, Q2 is the required injection amount of the above-mentioned rear-stage SCR, and Qbas is the basic value of the above-mentioned ammonia demand.

[0071] In one embodiment of the present application, the second acquisition unit includes a third acquisition module and a fifth determination module, which acquires the mass flow rate of the exhaust gas of the SCR system, the ratio of the ammonia of the SCR system to the hydroxide of the SCR system, the concentration of nitrogen oxides of the SCR system and the total efficiency value, where the total efficiency value is used to characterize the gas conversion efficiency of the SCR system; and determines the basic value of the ammonia demand based on the mass flow rate of the exhaust gas of the SCR system, the ratio of the ammonia of the SCR system to the hydroxide of the SCR system, the concentration of nitrogen oxides of the SCR system and the total efficiency value.

[0072] In one embodiment of the present application, the fifth determination module includes a determination submodule, which is used to determine the basic value of the above-mentioned ammonia demand according to Qbas=ConcNOx×η×ANR×MExh×C, where Qbas is the basic value of the above-mentioned ammonia demand, ConcNOx is the concentration of nitrogen oxides of the above-mentioned SCR system, η is the above-mentioned total efficiency value, ANR is the ratio of ammonia of the above-mentioned SCR system to hydroxide of the above-mentioned SCR system, MExh is the mass flow rate of the exhaust gas of the above-mentioned SCR system, and C is the gas molar coefficient.

[0073] The controller includes a processor and a memory. The first acquisition unit, the first determination unit, the second acquisition unit and the second determination unit are all stored in the memory as program units. The processor executes the program units stored in the memory to implement corresponding functions.

[0074] The processor includes a core, which retrieves the corresponding program unit from the memory. One or more cores can be configured, and the low accuracy of the existing solution in determining the ammonia demand can be addressed by adjusting the core parameters.

[0075] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0076] An embodiment of the present invention provides a computer-readable storage medium having a program stored thereon, which implements the above-mentioned method for determining the ammonia demand when executed by a processor.

[0077] An embodiment of the present invention provides a processor, which is used to run a program, wherein the method for determining the ammonia demand is executed when the program is run.

[0078] An embodiment of the present invention provides a device, comprising a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, at least the following steps are implemented: obtaining a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient, wherein the required injection amount of the front-stage SCR is used to characterize the ammonia required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the ammonia required injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the rear-stage SCR; determining an ammonia demand correction value based on the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient; obtaining a base value of ammonia demand; and determining a final ammonia demand based on the ammonia demand correction value and the base value of ammonia demand. The device herein may be a server, a PC, a PAD, a mobile phone, or the like.

[0079] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program initialized with at least the following method steps: obtaining the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient and the rear-stage correction coefficient, the required injection amount of the above-mentioned front-stage SCR is used to characterize the required ammonia injection amount of the above-mentioned front-stage SCR, the required injection amount of the above-mentioned rear-stage SCR is used to characterize the required ammonia injection amount of the above-mentioned rear-stage SCR, the above-mentioned front-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the above-mentioned front-stage SCR, and the above-mentioned rear-stage correction coefficient is used to characterize the correction coefficient of the ammonia required injection amount of the above-mentioned rear-stage SCR; determining an ammonia demand correction value based on the required injection amount of the above-mentioned front-stage SCR, the required injection amount of the above-mentioned rear-stage SCR, the above-mentioned front-stage correction coefficient and the above-mentioned rear-stage correction coefficient; obtaining a basic value of the ammonia demand; and determining a final ammonia demand based on the above-mentioned ammonia demand correction value and the above-mentioned basic value of the ammonia demand.

[0080] This application also provides an SCR system, such as Figure 5As shown, the SCR system includes a controller 100, a front-stage SCR 210, a rear-stage SCR 220, a front-stage NOx sensor 230, a rear-stage NOx sensor 240, and an ammonia sensor 250. The rear end of the front-stage SCR and the front end of the rear-stage SCR are connected by a connecting pipe. The ammonia sensor is installed on the inner wall of the connecting pipe. The front-stage NOx sensor is installed to the front end of the front-stage SCR, the rear-stage NOx sensor is installed to the rear end of the rear-stage SCR, and the ammonia sensor is installed to the front end of the rear-stage SCR. The front-stage NOx sensor, the rear-stage NOx sensor, and the ammonia sensor communicate with the controller respectively. The controller is configured to execute any of the above-mentioned methods for determining ammonia demand. By adaptively adjusting the ammonia demand and the required injection amount using the NH3 sensor signal, the calculation process is simplified, the control accuracy is improved, and the low accuracy of determining ammonia demand in existing solutions is solved.

[0081] like Figure 5 As shown, the system further includes a front-stage temperature sensor 260, a urea nozzle 270, a rear-stage temperature sensor 280 and an ammonia slip catalyst 290. The ammonia slip catalyst 290 is an ASC. The installation positions of the front-stage temperature sensor 260, the urea nozzle 270, the rear-stage temperature sensor 280 and the ammonia slip catalyst 290 are as shown. Figure 5 As shown, no further details will be given here. The system also includes an engine 310, a front-end oxidation catalyst 320, a front-end SCR 330, an oxidation catalyst 340, and a particulate filter 350, which are sequentially connected through pipelines. The front-end SCR 330 is not involved in the method of this application, so it will not be described again.

[0082] like Figure 6 As shown, the conversion efficiency of SCR for NOx and NH3 is not 100%. Its conversion efficiency is strongly related to the catalyst characteristics, exhaust gas mass flow rate and temperature. The conversion efficiency is generally determined through experiments. The calculation of the reactant concentration of the front and rear SCR and ASC is shown in the following formula:

[0083] NOx_ds=NOx_1_snr×(1-η1)×(1-η2)(1-η3)+β{NH3_snr-NOx_1_snr×(1-η1)(η2+(1-η2)η3)-(NH3_snr-NOx_1_snr×(1-η1)η2)η4}

[0084] snr is the sensor;

[0085] η 1～3 They are the efficiency of NOx (nitrogen oxides) reduction by the front-stage SCR, the efficiency of NOx (nitrogen oxides) reduction by the rear-stage SCR, and the efficiency of NOx (nitrogen oxides) reduction by the ASC;

[0086] η4 is the efficiency of ammonia oxidation by ASC;

[0087] β is the cross-sensitivity coefficient of the NOx sensor to NH3.

[0088] The units described above as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0089] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0090] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to execute all or part of the steps of the above-mentioned methods of each embodiment of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0091] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0092] 1) The method for determining ammonia demand in the present application simplifies the calculation process and improves control accuracy by adaptively adjusting the ammonia demand and the required injection amount based on the NH3 sensor signal, thereby solving the problem of low accuracy in determining ammonia demand in existing solutions.

[0093] 2) The ammonia demand control method of the present application simplifies the calculation process and improves the control accuracy by adaptively adjusting the ammonia demand and the required injection amount based on the NH3 sensor signal, thereby solving the problem of low accuracy in determining the ammonia demand in the existing solution.

[0094] 3) The controller of the present application simplifies the calculation process and improves the control accuracy by adaptively adjusting the ammonia demand and the required injection amount based on the NH3 sensor signal, thereby solving the problem of low accuracy in determining the ammonia demand in the existing solution.

[0095] 4) The SCR system of the present application simplifies the calculation process and improves the control accuracy by adaptively adjusting the ammonia demand and the required injection amount based on the NH3 sensor signal, thereby solving the problem of low accuracy in determining the ammonia demand in existing solutions.

[0096] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for determining ammonia demand, characterized in that: include: Obtaining a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient, wherein the required injection amount of the front-stage SCR is used to characterize the required ammonia injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the required ammonia injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the rear-stage SCR; determining an ammonia demand correction value according to the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient; Get the basic value of ammonia demand; Determining a final ammonia demand based on the ammonia demand correction value and the basic value of the ammonia demand; Obtaining a pre-stage correction coefficient includes: obtaining a mass flow rate of ammonia gas in the pre-stage SCR system, a mass flow rate of nitrogen oxides in the pre-stage SCR system, an air flow velocity, and a current temperature, wherein the current temperature is used to represent a temperature in the SCR system at a current moment, and the air flow velocity is used to represent an air flow velocity in the SCR system at a current moment; and determining the pre-stage correction coefficient based on the mass flow rate of ammonia gas in the pre-stage SCR system, the mass flow rate of nitrogen oxides in the pre-stage SCR system, the air flow velocity, and the current temperature; Obtaining a post-stage correction coefficient includes: obtaining a mass flow rate of post-stage SCR ammonia, a mass flow rate of post-stage SCR nitrogen oxides, an air flow velocity, and a current temperature, wherein the current temperature is used to represent a temperature in the SCR system at a current moment, and the air flow velocity is used to represent an air flow velocity in the SCR system at a current moment; and determining the post-stage correction coefficient based on the mass flow rate of post-stage SCR ammonia, the mass flow rate of post-stage SCR nitrogen oxides, the air flow velocity, and the current temperature; Obtaining a basic value of an ammonia demand includes: obtaining a mass flow rate of exhaust gas from an SCR system, a ratio of ammonia in the SCR system to hydroxide in the SCR system, a concentration of nitrogen oxides in the SCR system, and a total efficiency value, where the total efficiency value is used to characterize a gas conversion efficiency of the SCR system; and determining the basic value of the ammonia demand based on the mass flow rate of exhaust gas from the SCR system, the ratio of ammonia in the SCR system to hydroxide in the SCR system, the concentration of nitrogen oxides in the SCR system, and the total efficiency value.

2. The method according to claim 1, characterized in that Determining an ammonia demand correction value according to the required injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient includes: The ammonia demand correction value is determined according to Qx=fac1×Q1+fac2×Q2, where Qx is the ammonia demand correction value, fac1 is the front-stage correction coefficient, Q1 is the required injection amount of the front-stage SCR, fac2 is the rear-stage correction coefficient, and Q2 is the required injection amount of the rear-stage SCR.

3. The method according to claim 2, characterized in that Determining a final ammonia demand according to the ammonia demand correction value and the basic value of the ammonia demand includes: The final ammonia demand is determined according to Q=fac1×Q1+fac2×Q2+Qbas, where Q is the final ammonia demand, fac1 is the front-stage correction coefficient, Q1 is the required injection amount of the front-stage SCR, fac2 is the rear-stage correction coefficient, Q2 is the required injection amount of the rear-stage SCR, and Qbas is the basic value of the ammonia demand.

4. The method according to claim 1, wherein Determining a basic value of the ammonia demand according to the mass flow of the exhaust gas of the SCR system, the ratio of the ammonia of the SCR system to the hydroxide of the SCR system, and the concentration of nitrogen oxides of the SCR system includes: The basic value of the ammonia demand is determined according to Qbas=ConcNOx×η×ANR×MExh×C, where Qbas is the basic value of the ammonia demand, ConcNOx is the concentration of nitrogen oxides of the SCR system, η is the total efficiency value, ANR is the ratio of ammonia of the SCR system to hydroxide of the SCR system, MExh is the mass flow rate of the exhaust gas of the SCR system, and C is the gas molar coefficient.

5. A method for controlling ammonia demand, characterized in that: include: Determining the final ammonia demand using the method for determining the ammonia demand according to any one of claims 1 to 4; According to the final ammonia demand, the SCR system is controlled to be charged with ammonia of the final ammonia demand.

6. A controller, characterized in that: include: a first acquisition unit, configured to acquire a required injection amount of a front-stage SCR, a required injection amount of a rear-stage SCR, a front-stage correction coefficient, and a rear-stage correction coefficient, wherein the required injection amount of the front-stage SCR is used to characterize the required ammonia injection amount of the front-stage SCR, the required injection amount of the rear-stage SCR is used to characterize the required ammonia injection amount of the rear-stage SCR, the front-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the front-stage SCR, and the rear-stage correction coefficient is used to characterize the correction coefficient of the required ammonia injection amount of the rear-stage SCR; a first determining unit, configured to determine an ammonia demand correction value according to a required injection amount of the front-stage SCR, a required injection amount of the rear-stage SCR, the front-stage correction coefficient, and the rear-stage correction coefficient; The second acquisition unit is used to obtain a basic value of ammonia demand; a second determining unit, configured to determine a final ammonia demand based on the ammonia demand correction value and the basic value of the ammonia demand; The first acquisition unit includes a first acquisition module and a first determination module, the first acquisition module is used to obtain the mass flow rate of ammonia in the pre-stage SCR, the mass flow rate of nitrogen oxides in the pre-stage SCR, the air flow rate and the current temperature, the current temperature is used to represent the temperature in the SCR system at the current moment, and the air flow rate is used to represent the air flow rate in the SCR system at the current moment; The first determination module is used to determine the front-stage correction coefficient according to the mass flow rate of the front-stage SCR ammonia, the mass flow rate of the front-stage SCR nitrogen oxides, the air flow rate and the current temperature; The first acquisition unit includes a second acquisition module and a second determination module, the second acquisition module is used to obtain the mass flow rate of post-stage SCR ammonia, the mass flow rate of post-stage SCR nitrogen oxides, the air flow rate and the current temperature, the current temperature is used to represent the temperature in the SCR system at the current moment, and the air flow rate is used to represent the air flow rate in the SCR system at the current moment; The second determination module is used to determine the post-stage correction coefficient according to the mass flow rate of the post-stage SCR ammonia, the mass flow rate of the post-stage SCR nitrogen oxides, the air flow rate and the current temperature; The second acquisition unit includes a third acquisition module and a fifth determination module, which acquires the mass flow rate of the exhaust gas of the SCR system, the ratio of the ammonia of the SCR system to the hydroxide of the SCR system, the concentration of the nitrogen oxides of the SCR system and the total efficiency value, where the total efficiency value is used to characterize the gas conversion efficiency of the SCR system; and determines the basic value of the ammonia demand based on the mass flow rate of the exhaust gas of the SCR system, the ratio of the ammonia of the SCR system to the hydroxide of the SCR system, the concentration of the nitrogen oxides of the SCR system and the total efficiency value.

7. An SCR system, characterized in that: include: A controller, a front-stage SCR, a rear-stage SCR, a front-stage nitrogen oxide sensor, a rear-stage nitrogen oxide sensor and an ammonia sensor, the rear end of the front-stage SCR and the front end of the rear-stage SCR are connected through a connecting pipe, the ammonia sensor is installed on the inner wall of the connecting pipe, the front-stage nitrogen oxide sensor is installed to the front end of the front-stage SCR, the rear-stage nitrogen oxide sensor is installed to the rear end of the rear-stage SCR, and the ammonia sensor is installed to the front end of the rear-stage SCR. The front-stage nitrogen oxide sensor, the rear-stage nitrogen oxide sensor and the ammonia sensor communicate with the controller respectively, and the controller is used to execute the method for determining the ammonia demand as described in any one of claims 1 to 4.

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