Method, device and equipment for controlling urea injection amount of two-stage SCR (Selective Catalytic Reduction)

Abstract

The invention discloses a two-stage SCR urea injection amount control method, device and equipment, and relates to the technical field of engine exhaust aftertreatment. The method comprises the steps that the real-time working mode of an engine is obtained, and the control mode of a front-stage SCR and the control mode of a rear-stage SCR are determined according to the obtained working mode; on the basis of the determined control mode, the preceding-stage SCR and the post-stage SCR conduct corresponding urea injection amount calculation, and control mode switching is conducted according to the working state of the SCR; wherein the control mode of the front-stage SCR comprises an initial mode, a target efficiency mode and a high-efficiency mode, and the control mode of the rear-stage SCR comprises an initial mode and a high-efficiency mode. According to the method, the coordination control state of the two-stage SCR is determined according to the working mode of the engine, nitrogen oxide emission is more effectively reduced for different working modes, meanwhile, the influence of the DPF state on coordination control of the two-stage SCR is considered, and efficient coordination control over the urea injection amount of the two-stage SCR is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of engine exhaust aftertreatment, and in particular to a dual-stage SCR urea injection quantity control method, device and equipment. Background Art

[0002] At present, the National VI after-treatment system generally adopts the "DOC (diesel oxidation catalyst) + DPF (diesel particulate purifier) ​​+ SCR (selective catalytic reduction) + ASC (ammonia purification catalyst)" solution to deal with emission pollutants in automobile exhaust. With the upgrade of emission regulations in the next stage, the emission limit requirements for pollutants such as nitrogen oxides will be further increased. The after-treatment system needs to adopt a two-stage SCR solution, namely "ccSCR (compact coupled selective catalytic reduction) + DOC + DPF + SCR + ASC". The two-stage SCR after-treatment system requires the front and rear stage SCR to independently control urea injection, and requires coordinated control of the front and rear stage SCR.

[0003] At present, the commonly used method for controlling the dual-stage SCR system is to obtain the primary and secondary SCR inlet temperatures in real time, determine the SCR cooperative control state according to the two temperatures, and determine the urea injection amount of the primary and secondary SCR according to the SCR cooperative control state. However, this control method only determines the SCR cooperative control state according to the primary and secondary SCR inlet temperatures, does not consider the needs of different engine operating conditions, and does not consider the relationship between dual-stage SCR control and DPF. Summary of the invention

[0004] The present application provides a dual-stage SCR urea injection amount control method, device and equipment, which determines the coordinated control state of the dual-stage SCR according to the engine working mode, more effectively reduces nitrogen oxide emissions for different working modes, and also considers the influence of the DPF state on the dual-stage SCR coordinated control, thereby realizing efficient coordinated control of the urea injection amount of the dual-stage SCR.

[0005] In a first aspect, an embodiment of the present application provides a dual-stage SCR urea injection amount control method, the dual-stage SCR urea injection amount control method comprising:

[0006] Acquire the real-time working mode of the engine, and determine the control mode of the front-stage SCR and the rear-stage SCR according to the acquired working mode;

[0007] Based on the determined control mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amount, and switch the control mode according to the working state of the SCR;

[0008] The control modes of the front-stage SCR include an initial mode, a target efficiency mode, and a high efficiency mode, and the control modes of the rear-stage SCR include an initial mode and a high efficiency mode.

[0009] In combination with the first aspect, in one implementation,

[0010] The working modes of the engine include a normal mode and a special mode;

[0011] The normal mode is a working mode in which the engine often works for a long time, including a default mode, an economic mode, and a dynamic mode;

[0012] The special mode is a special operating mode that the engine enters to achieve a specific effect, including a regeneration mode and an exhaust temperature management mode;

[0013] The regeneration mode includes DPF regeneration mode, front-stage SCR desulfurization regeneration mode, rear-stage SCR desulfurization regeneration mode, and decrystallization regeneration mode;

[0014] The exhaust temperature management mode includes a front-stage SCR heating mode, a DOC heating mode, and a rear-stage SCR heating mode.

[0015] In combination with the first aspect, in one implementation, the control modes of the front-stage SCR and the rear-stage SCR are determined according to the acquired working mode, specifically:

[0016] When the working mode of the engine is the normal mode, the initial control mode of the front-stage SCR is determined to be the target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be the high efficiency mode;

[0017] When the working mode of the engine is a special mode, the corresponding control modes of the front-stage SCR and the rear-stage SCR are selected based on the working condition characteristics of the special mode.

[0018] In combination with the first aspect, in one implementation,

[0019] The control mode is switched according to the working state of the SCR. Specifically, when the working mode of the engine is the normal mode, the control mode is switched according to the change of the working state of the SCR;

[0020] The control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the front-stage SCR is specifically as follows:

[0021] When the front-stage SCR is in the target efficiency mode, if the current front-stage SCR efficiency target is greater than the first limit value, the front-stage SCR switches to the high efficiency mode;

[0022] When the front-stage SCR is in the high efficiency mode, if the current front-stage SCR efficiency target is less than the second limit value, and the nitrogen oxide conversion rate of the rear-stage SCR is greater than the third limit value, the front-stage SCR switches to the target efficiency mode.

[0023] In combination with the first aspect, in one implementation,

[0024] The control mode is switched according to the working state of the SCR. Specifically, when the working mode of the engine is the normal mode, the control mode is switched according to the change of the working state of the SCR;

[0025] The control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the subsequent SCR is specifically as follows:

[0026] When the control mode of the rear SCR is the high efficiency mode, if the temperature of the rear SCR is lower than the minimum urea injection temperature, the rear SCR switches to the initial mode, and when the temperature of the rear SCR is not lower than the minimum urea injection temperature, the rear SCR switches to the high efficiency mode.

[0027] In combination with the first aspect, in one implementation,

[0028] The initial mode of the front-stage SCR is to stop injecting urea;

[0029] The target efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR efficiency target;

[0030] The high efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR ammonia storage target;

[0031] The initial mode of the post-stage SCR is to stop injecting urea;

[0032] The high efficiency mode of the post-stage SCR is to calculate the urea injection amount based on the post-stage SCR ammonia storage target.

[0033] In combination with the first aspect, in one implementation, the calculating of the urea injection amount based on the pre-stage SCR efficiency target specifically includes:

[0034] Determine the basic efficiency target of the front-stage SCR according to the inlet temperature of the front-stage SCR, the exhaust flow rate, and the current working mode of the engine;

[0035] A first correction coefficient for the front-stage SCR efficiency target is determined based on the DPF carbon load and the DPF temperature;

[0036] Determine a second correction coefficient for the efficiency target of the front-stage SCR according to the nitrogen oxide conversion rate of the rear-stage SCR;

[0037] Determining a front-stage SCR efficiency target based on a front-stage SCR basic efficiency target, a first correction coefficient of the front-stage SCR efficiency target, and a second correction coefficient of the front-stage SCR efficiency target;

[0038] Determine the amount of urea required to convert nitrogen oxides based on the nitrogen oxide concentration at the inlet of the front-stage SCR, the exhaust flow rate of the front-stage SCR, and the temperature of the front-stage SCR;

[0039] Based on the determined amount of urea required for converting nitrogen oxides and the determined pre-stage SCR efficiency target, a theoretical urea injection amount of the pre-stage SCR is obtained;

[0040] Calculate the actual conversion efficiency of the front-stage SCR based on the nitrogen oxide concentration at the inlet of the front-stage SCR and the nitrogen oxide concentration at the outlet of the front-stage SCR;

[0041] According to the calculated actual conversion efficiency of the front-stage SCR and the target conversion efficiency of the front-stage SCR, a correction coefficient of the urea injection amount of the front-stage SCR is obtained;

[0042] The final urea injection amount of the front-stage SCR is obtained according to the obtained correction coefficient of the urea injection amount of the front-stage SCR and the theoretical urea injection amount of the front-stage SCR.

[0043] In combination with the first aspect, in one implementation, the calculating of the urea injection amount based on the pre-stage SCR ammonia storage target specifically includes:

[0044] According to the temperature of the front-stage SCR, check the pre-set MAP table to determine the target ammonia storage capacity of the front-stage SCR;

[0045] According to the deviation between the target ammonia storage amount of the front-stage SCR and the actual ammonia storage amount of the front-stage SCR, the ammonia required for ammonia storage control is obtained through PID control;

[0046] The ammonia demand is obtained based on the ammonia required for ammonia storage control and the ammonia required for the front-stage SCR to convert nitrogen oxides;

[0047] The ammonia demand is converted into the urea demand to obtain the urea injection amount of the front-stage SCR.

[0048] In a second aspect, an embodiment of the present application provides a dual-stage SCR urea injection amount control device, the dual-stage SCR urea injection amount control device comprising:

[0049] A determination module, which is used to obtain the real-time working mode of the engine and determine the control mode of the front-stage SCR and the rear-stage SCR according to the obtained working mode;

[0050] An execution module, which is used to calculate the corresponding urea injection amount of the front-stage SCR and the rear-stage SCR based on the determined control mode, and switch the control mode according to the working state of the SCR;

[0051] The control modes of the front-stage SCR include an initial mode, a target efficiency mode, and a high efficiency mode, and the control modes of the rear-stage SCR include an initial mode and a high efficiency mode.

[0052] In a third aspect, an embodiment of the present application provides a two-stage SCR urea injection quantity control device, which includes a processor, a memory, and a two-stage SCR urea injection quantity control program stored in the memory and executable by the processor, wherein when the two-stage SCR urea injection quantity control program is executed by the processor, the steps of the two-stage SCR urea injection quantity control method described above are implemented.

[0053] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0054] By acquiring the real-time working mode of the engine and determining the control modes of the front-stage SCR and the rear-stage SCR according to the acquired working mode, then based on the determined control mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amount, and switch the control mode according to the working state of the SCR, by determining the coordinated control state of the two-stage SCR according to the working mode of the engine, nitrogen oxide emissions are more effectively reduced for different working modes, and the influence of the DPF state on the coordinated control of the two-stage SCR is also considered, so as to realize efficient coordinated control of the urea injection amount of the two-stage SCR. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of the dual-stage SCR urea injection quantity control method of the present application;

[0056] Figure 2 It is the architecture diagram of the double-stage SCR;

[0057] Figure 3 This is a functional module schematic diagram of the dual-stage SCR urea injection quantity control device of this application;

[0058] Figure 4 This is a schematic diagram of the hardware structure of the two-stage SCR urea injection quantity control device of this application. DETAILED DESCRIPTION

[0059] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0060] In order to make the objectives, technical solutions and advantages of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0061] In the first aspect, an embodiment of the present application provides a two-stage SCR urea injection amount control method, which coordinates the two-stage SCR control according to the requirements of different engine operating conditions, and coordinates the urea injection amount of the front and rear SCRs according to the influence between the SCR and the DPF, thereby realizing efficient coordinated control of the urea injection amount of the two-stage SCR.

[0062] In one embodiment, referring to Figure 1 , Figure 1 Schematic diagram of the process of the dual-stage SCR urea injection control method of the present application. Figure 1 As shown, the dual-stage SCR urea injection amount control method includes:

[0063] S1: Acquire the real-time working mode of the engine, and determine the control mode of the front-stage SCR and the rear-stage SCR according to the acquired working mode;

[0064] S2: Based on the determined control mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amount, and switch the control mode according to the working state of the SCR;

[0065] The control modes of the front-stage SCR include an initial mode, a target efficiency mode, and a high efficiency mode, and the control modes of the rear-stage SCR include an initial mode and a high efficiency mode.

[0066] See also Figure 2 As shown in the figure, it is an architectural diagram of a two-stage SCR. The front-stage SCR (i.e., ccSCR / ccASC) is installed at the rear end of the turbine outlet. A nitrogen oxide sensor, a temperature sensor, and a urea nozzle are also installed between the ccSCR and the turbine outlet. The nitrogen oxide sensor and the temperature sensor respectively measure the nitrogen oxide concentration and temperature before the ccSCR. The urea nozzle is used to execute the urea injection amount required for injecting the ccSCR. The DOC, DPF, and rear-stage SCR are installed after the front-stage SCR. A temperature sensor and a urea nozzle are installed in front of the rear-stage SCR to measure the inlet temperature of the rear-stage SCR and inject urea into the rear-stage SCR.

[0067] It should be noted that the working mode of the engine is determined according to the working state and / or working condition of the engine. The working mode of the engine includes a normal mode and a special mode; the normal mode is the working mode in which the engine often works for a long time, including the default mode, the economic mode, and the dynamic mode; the special mode is the special working mode entered by the engine to achieve a specific effect, including the regeneration mode and the exhaust temperature management mode; the regeneration mode includes the DPF regeneration mode, the front-stage SCR desulfurization regeneration mode, the rear-stage SCR desulfurization regeneration mode, and the decrystallization regeneration mode; the exhaust temperature management mode includes the front-stage SCR heating mode, the DOC heating mode, and the rear-stage SCR heating mode.

[0068] In this application, the control modes of the front-stage SCR and the rear-stage SCR are determined according to the acquired working mode, specifically:

[0069] When the working mode of the engine is the normal mode, the initial control mode of the front-stage SCR is determined to be the target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be the high efficiency mode;

[0070] When the working mode of the engine is a special mode, the corresponding control modes of the front-stage SCR and the rear-stage SCR are selected based on the working condition characteristics of the special mode.

[0071] Among them, for the corresponding control modes of the front-stage SCR and the rear-stage SCR selected based on the working condition characteristics of the special mode, the engineering personnel select the appropriate control modes of the front and rear-stage SCR according to the working condition characteristics of the specific special mode. For example, in the DPF regeneration mode, the front-stage SCR is the target efficiency mode, and the rear-stage SCR is the initial mode; in the front-stage SCR heating mode, the front-stage SCR is the initial mode, and the rear-stage SCR is the initial mode; in the rear-stage SCR heating mode, the front-stage SCR is the high efficiency mode, and the rear-stage SCR is the initial mode.

[0072] It should be noted that determining the control mode of the front SCR and the rear SCR according to the acquired working mode also includes: before the temperature of the front SCR and the rear SCR reaches the urea injection temperature, the front SCR and the rear SCR are defaulted to the initial mode and urea injection is stopped.

[0073] In the present application, the control mode is switched according to the working state of the SCR. Specifically, when the working mode of the engine is the normal mode, the control mode is switched according to the change of the working state of the SCR.

[0074] The control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the front-stage SCR is specifically as follows:

[0075] When the front-stage SCR is in the target efficiency mode, if the current front-stage SCR efficiency target is greater than the first limit value, the front-stage SCR switches to the high efficiency mode;

[0076] When the front-stage SCR is in high efficiency mode, if the current front-stage SCR efficiency target is less than the second limit value, and the nitrogen oxide conversion rate of the rear-stage SCR is greater than the third limit value, the front-stage SCR switches to the target efficiency mode. The first limit value is greater than the second limit value.

[0077] In the present application, the control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the subsequent SCR is specifically as follows:

[0078] When the control mode of the rear SCR is high efficiency mode, if the temperature of the rear SCR is lower than the minimum urea injection temperature, the rear SCR switches to the initial mode, and when the temperature of the rear SCR is not lower than the minimum urea injection temperature, the rear SCR switches to the high efficiency mode. The minimum urea injection temperature is a calibrated value, which indicates the lowest temperature at which urea can be hydrolyzed and reacted in the SCR to convert nitrogen oxides, and is obtained by engineering and technical personnel through experiments based on the characteristics of the SCR catalyst carrier.

[0079] In the present application, for the control modes of the front-stage SCR and the rear-stage SCR, the initial mode of the front-stage SCR is to stop the injection of urea; the target efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR efficiency target; the high-efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR ammonia storage target; the initial mode of the rear-stage SCR is to stop the injection of urea; the high-efficiency mode of the rear-stage SCR is to calculate the urea injection amount based on the rear-stage SCR ammonia storage target.

[0080] Further, in one embodiment, the urea injection amount is calculated based on the pre-stage SCR efficiency target, specifically including:

[0081] S201: determining a basic efficiency target of the front-stage SCR according to an inlet temperature of the front-stage SCR, an exhaust flow rate, and a current operating mode of the engine;

[0082] Specifically, different SCR basic efficiency target MAP diagrams are selected according to different working modes of the engine (for example, when the engine working mode is the normal mode, the SCR basic efficiency target MAP diagram #01 is selected; when the engine working mode is different special modes, the SCR basic efficiency target MAP diagrams #02, #03, ... are selected; the number of SCR basic efficiency target MAP diagrams and the corresponding relationship with the engine working mode are determined by engineering and technical personnel according to the number of engine working modes and the degree of difference in the working conditions of each working mode, and the number of SCR basic efficiency target MAP diagrams does not exceed the number of engine working modes), and then the front-stage SCR basic efficiency target is obtained by looking up the table from the selected SCR basic efficiency target MAP diagram according to the inlet temperature of the front-stage SCR and the exhaust flow rate of the front-stage SCR. The SCR basic efficiency target MAP diagram is a calibrable MAP, and the relationship between the front-stage SCR inlet temperature, exhaust flow rate and SCR basic efficiency target is calibrated by the technicians under a specific engine working mode;

[0083] S202: Determine a first correction coefficient of the front-stage SCR efficiency target according to the DPF carbon load and the DPF temperature;

[0084] Specifically, the first correction coefficient of the front-stage SCR efficiency target is obtained by checking the MAP according to the DPF carbon load and the DPF temperature. The coefficient ranges from 0 to 2, and the MAP is calibrated by the engineering personnel;

[0085] S203: Determine a second correction coefficient for the efficiency target of the front-stage SCR according to the nitrogen oxide conversion rate of the rear-stage SCR;

[0086] Specifically, the second correction coefficient of the efficiency target of the front-stage SCR is obtained by checking the MAP according to the nitrogen oxide conversion rate of the rear-stage SCR. The value range of the coefficient is 0-2. The MAP is calibrated by the engineering personnel.

[0087] S204: determining a front-stage SCR efficiency target based on a front-stage SCR basic efficiency target, a first correction coefficient of the front-stage SCR efficiency target, and a second correction coefficient of the front-stage SCR efficiency target;

[0088] Specifically, the front-stage SCR basic efficiency target is multiplied by the first correction coefficient of the front-stage SCR efficiency target, and then multiplied by the second correction coefficient of the front-stage SCR efficiency target to obtain the front-stage SCR efficiency target;

[0089] It should be noted that different basic efficiency targets of the front-stage SCR can be selected for different engine operating modes; the first correction coefficient determined according to the DPF carbon load and the DPF temperature can correct the target efficiency of the front-stage SCR, so that when the working conditions are suitable for DPF passive regeneration, the target efficiency of the front-stage SCR is adjusted to promote DPF passive regeneration, extend the DPF active regeneration interval, and reduce the DPF regeneration frequency, thereby reducing fuel consumption; the second correction coefficient of the efficiency target of the front-stage SCR is determined according to the nitrogen oxide conversion rate of the rear-stage SCR. When the conversion efficiency of the rear-stage SCR decreases, the conversion efficiency target of the front-stage SCR can be adjusted to improve the nitrogen oxide conversion efficiency of the front-stage SCR and ensure that emissions do not exceed the standard. When the conversion efficiency of the rear-stage SCR is high, the efficiency target of the front-stage SCR can be appropriately reduced to reduce the impact of the excessively high conversion efficiency of the front-stage SCR on the passive regeneration of the DPF;

[0090] S205: determining the amount of urea required for converting the nitrogen oxides according to the nitrogen oxide concentration at the inlet of the front-stage SCR, the exhaust flow rate of the front-stage SCR, and the temperature of the front-stage SCR;

[0091] Specifically, the nitrogen oxide concentration at the inlet of the front-stage SCR is multiplied by the exhaust flow rate of the front-stage SCR, and then multiplied by the stoichiometric ratio of the chemical reaction of nitrogen oxides and ammonia to obtain the ammonia required for converting nitrogen oxides. The ammonia is multiplied by 5.425 to obtain the amount of urea required for converting nitrogen oxides. The stoichiometric ratio of the chemical reaction of nitrogen oxides and ammonia is obtained by checking the MAP according to the temperature of the front-stage SCR.

[0092] S206: obtaining a theoretical urea injection amount of the front-stage SCR based on the determined urea amount required for converting nitrogen oxides and the determined front-stage SCR efficiency target;

[0093] Specifically, the amount of urea required for converting nitrogen oxides is multiplied by the efficiency target of the previous SCR to obtain the theoretical urea injection amount of the previous SCR;

[0094] S207: Calculating the actual conversion efficiency of the front-stage SCR according to the nitrogen oxide concentration at the inlet of the front-stage SCR and the nitrogen oxide concentration at the outlet of the front-stage SCR;

[0095] Specifically, the actual conversion efficiency of the front-stage SCR = (nitrogen oxide concentration at the inlet of the front-stage SCR - nitrogen oxide concentration at the outlet of the front-stage SCR) / nitrogen oxide concentration at the inlet of the front-stage SCR;

[0096] S208: Obtaining a correction coefficient of urea injection amount of the front-stage SCR according to the calculated actual conversion efficiency of the front-stage SCR and the target conversion efficiency of the front-stage SCR;

[0097] Specifically, according to the deviation between the actual conversion efficiency of the front-stage SCR and the target conversion efficiency of the front-stage SCR, the MAP is checked to obtain the correction coefficient of the urea injection amount of the front-stage SCR;

[0098] S209: Obtain the final urea injection amount of the front SCR according to the obtained urea injection amount correction coefficient of the front SCR and the theoretical urea injection amount of the front SCR. Specifically, the urea injection amount correction coefficient of the front SCR is multiplied by the theoretical urea injection amount of the front SCR to obtain the final urea injection amount of the front SCR.

[0099] Further, in one embodiment, the urea injection amount is calculated based on the pre-stage SCR ammonia storage target, specifically including:

[0100] S211: Checking a preset MAP table according to the temperature of the front-stage SCR to determine the target ammonia storage amount of the front-stage SCR; the actual ammonia storage amount of the front-stage SCR is the actual ammonia storage amount of the SCR at the previous moment plus the ammonia newly entering the SCR and minus the ammonia consumed by converting nitrogen oxides;

[0101] S212: obtaining ammonia required for ammonia storage control through PID control according to the deviation between the target ammonia storage amount of the preceding SCR and the actual ammonia storage amount of the preceding SCR;

[0102] S213: Obtaining an ammonia demand based on ammonia required for ammonia storage control and ammonia required for conversion of nitrogen oxides by the front-stage SCR;

[0103] Specifically, the ammonia required for ammonia storage control is added to the ammonia required for the front-stage SCR to convert nitrogen oxides to obtain the ammonia demand; the ammonia required for the front-stage SCR to convert nitrogen oxides is the nitrogen oxide concentration at the inlet of the front-stage SCR multiplied by the exhaust flow rate of the front-stage SCR, and then multiplied by the chemical reaction stoichiometric ratio of nitrogen oxides and ammonia;

[0104] S214: Convert the ammonia demand into the urea demand to obtain the urea injection amount of the front-stage SCR. Specifically, the ammonia demand is multiplied by 5.425 to obtain the urea demand, thereby obtaining the urea injection amount of the front-stage SCR.

[0105] It should be noted that, for the rear-stage SCR in the high-efficiency mode, the urea injection amount is calculated based on the rear-stage SCR ammonia storage target, and the calculation method is similar to the calculation method of the high-efficiency mode of the front-stage SCR mentioned above.

[0106] The dual-stage SCR urea injection amount control method of the embodiment of the present application obtains the real-time working mode of the engine, and determines the control mode of the front-stage SCR and the rear-stage SCR according to the obtained working mode, then based on the determined control mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amount, and switch the control mode according to the working state of the SCR. By determining the coordinated control state of the dual-stage SCR according to the engine working mode, nitrogen oxide emissions are more effectively reduced for different working modes. At the same time, the influence of the DPF state on the coordinated control of the dual-stage SCR is also considered, so as to achieve efficient coordinated control of the urea injection amount of the dual-stage SCR.

[0107] In a second aspect, an embodiment of the present application also provides a dual-stage SCR urea injection quantity control device.

[0108] In one embodiment, referring to Figure 3 , Figure 3 This is a functional module diagram of the dual-stage SCR urea injection control device of this application. Figure 3 As shown, the dual-stage SCR urea injection quantity control device includes: a determination module and an execution module.

[0109] The determination module is used to obtain the real-time working mode of the engine, and determine the control mode of the front-stage SCR and the rear-stage SCR according to the obtained working mode; the execution module is used to calculate the corresponding urea injection amount of the front-stage SCR and the rear-stage SCR based on the determined control mode, and switch the control mode according to the working state of the SCR; wherein, the control mode of the front-stage SCR includes the initial mode, the target efficiency mode, and the high efficiency mode, and the control mode of the rear-stage SCR includes the initial mode and the high efficiency mode.

[0110] Among them, the functional implementation of each module in the above-mentioned two-stage SCR urea injection amount control device corresponds to each step in the above-mentioned two-stage SCR urea injection amount control method embodiment, and its functions and implementation processes are no longer repeated here.

[0111] In a third aspect, an embodiment of the present application provides a dual-stage SCR urea injection quantity control device, which may be a device having a data processing function, such as a personal computer (PC), a laptop computer, or a server.

[0112] Reference Figure 4 , Figure 4 The schematic diagram of the hardware structure of the dual-stage SCR urea injection quantity control device involved in the embodiment of the present application is shown in FIG. In the embodiment of the present application, the dual-stage SCR urea injection quantity control device may include a processor, a memory, a communication interface, and a communication bus.

[0113] The communication bus may be of any type and is used to interconnect the processor, the memory, and the communication interface.

[0114] The communication interface includes an input / output (I / O) interface, a physical interface, and a logical interface, etc., which are used to interconnect the devices inside the dual-stage SCR urea injection quantity control device, and an interface used to interconnect the dual-stage SCR urea injection quantity control device with other devices (such as other computing devices or user devices). The physical interface can be an Ethernet interface, an optical fiber interface, an ATM interface, etc.; the user device can be a display, a keyboard, etc.

[0115] The memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0116] The processor may be a general processor, and the general processor may call the dual-stage SCR urea injection quantity control program stored in the memory, and execute the dual-stage SCR urea injection quantity control method provided in the embodiment of the present application. For example, the general processor may be a central processing unit (CPU). The method executed when the dual-stage SCR urea injection quantity control program is called may refer to the various embodiments of the dual-stage SCR urea injection quantity control method of the present application, and will not be repeated here.

[0117] Those skilled in the art will understand that Figure 4 The hardware structure shown in the figure does not constitute a limitation on the present application, and may include more or less components than shown in the figure, or combine certain components, or arrange the components differently.

[0118] The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings 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 limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. The terms "first", "second" and "third" are used to distinguish different objects, etc., and do not represent a sequence, nor do they limit "first", "second" and "third" to different types.

[0119] In the description of the embodiments of the present application, "exemplary", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a specific way.

[0120] In the description of the embodiments of the present application, unless otherwise specified, “ / ” means or, for example, A / B can mean A or B; the “and / or” in the text is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, “multiple” refers to two or more than two.

[0121] In some processes described in the embodiments of the present application, multiple operations or steps that appear in a specific order are included, but it should be understood that these operations or steps may not be executed in the order in which they appear in the embodiments of the present application or in parallel, and the sequence number of the operation is only used to distinguish the different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed in sequence or in parallel, and these operations or steps may be combined.

[0122] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, disk, CD) as described above, and includes a number of instructions for a terminal device to execute the methods described in each embodiment of the present application.

[0123] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A two-stage SCR urea injection control method, characterized in that: The dual-stage SCR urea injection amount control method comprises: Acquire the real-time working mode of the engine, and determine the control mode of the front-stage SCR and the rear-stage SCR according to the acquired working mode; Based on the determined control mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amount, and switch the control mode according to the working state of the SCR; The control modes of the front-stage SCR include an initial mode, a target efficiency mode, and a high efficiency mode, and the control modes of the rear-stage SCR include an initial mode and a high efficiency mode.

2. A dual-stage SCR urea injection amount control method as claimed in claim 1, characterized in that: The working modes of the engine include a normal mode and a special mode; The normal mode is a working mode in which the engine often works for a long time, including a default mode, an economic mode, and a dynamic mode; The special mode is a special operating mode that the engine enters to achieve a specific effect, including a regeneration mode and an exhaust temperature management mode; The regeneration mode includes DPF regeneration mode, front-stage SCR desulfurization regeneration mode, rear-stage SCR desulfurization regeneration mode, and decrystallization regeneration mode; The exhaust temperature management mode includes a front-stage SCR heating mode, a DOC heating mode, and a rear-stage SCR heating mode.

3. A dual-stage SCR urea injection control method as claimed in claim 2, characterized in that: The control modes of the front-stage SCR and the rear-stage SCR are determined according to the acquired working mode, specifically: When the working mode of the engine is the normal mode, the initial control mode of the front-stage SCR is determined to be the target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be the high efficiency mode; When the working mode of the engine is a special mode, the corresponding control modes of the front-stage SCR and the rear-stage SCR are selected based on the working condition characteristics of the special mode.

4. A dual-stage SCR urea injection amount control method as claimed in claim 3, characterized in that: The control mode is switched according to the working state of the SCR. Specifically, when the working mode of the engine is the normal mode, the control mode is switched according to the change of the working state of the SCR; The control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the front-stage SCR is specifically as follows: When the front-stage SCR is in the target efficiency mode, if the current front-stage SCR efficiency target is greater than the first limit value, the front-stage SCR switches to the high efficiency mode; When the front-stage SCR is in the high efficiency mode, if the current front-stage SCR efficiency target is less than the second limit value, and the nitrogen oxide conversion rate of the rear-stage SCR is greater than the third limit value, the front-stage SCR switches to the target efficiency mode.

5. A dual-stage SCR urea injection control method as claimed in claim 3, characterized in that: The control mode is switched according to the working state of the SCR. Specifically, when the working mode of the engine is the normal mode, the control mode is switched according to the change of the working state of the SCR; The control mode is switched according to the change of the working state of the SCR, wherein the control mode switching of the subsequent SCR is specifically as follows: When the control mode of the rear SCR is the high efficiency mode, if the temperature of the rear SCR is lower than the minimum urea injection temperature, the rear SCR switches to the initial mode, and when the temperature of the rear SCR is not lower than the minimum urea injection temperature, the rear SCR switches to the high efficiency mode.

6. A dual-stage SCR urea injection amount control method as claimed in claim 1, characterized in that: The initial mode of the front-stage SCR is to stop injecting urea; The target efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR efficiency target; The high efficiency mode of the front-stage SCR is to calculate the urea injection amount based on the front-stage SCR ammonia storage target; The initial mode of the post-stage SCR is to stop injecting urea; The high efficiency mode of the post-stage SCR is to calculate the urea injection amount based on the post-stage SCR ammonia storage target.

7. A dual-stage SCR urea injection control method as claimed in claim 6, characterized in that: The calculation of the urea injection amount based on the front-stage SCR efficiency target specifically includes: Determine the basic efficiency target of the front-stage SCR according to the inlet temperature of the front-stage SCR, the exhaust flow rate, and the current working mode of the engine; A first correction coefficient for the front-stage SCR efficiency target is determined based on the DPF carbon load and the DPF temperature; Determine a second correction coefficient for the efficiency target of the front-stage SCR according to the nitrogen oxide conversion rate of the rear-stage SCR; Determining a front-stage SCR efficiency target based on a front-stage SCR basic efficiency target, a first correction coefficient of the front-stage SCR efficiency target, and a second correction coefficient of the front-stage SCR efficiency target; Determine the amount of urea required to convert nitrogen oxides based on the nitrogen oxide concentration at the inlet of the front-stage SCR, the exhaust flow rate of the front-stage SCR, and the temperature of the front-stage SCR; Based on the determined amount of urea required for converting nitrogen oxides and the determined pre-stage SCR efficiency target, a theoretical urea injection amount of the pre-stage SCR is obtained; Calculate the actual conversion efficiency of the front-stage SCR based on the nitrogen oxide concentration at the inlet of the front-stage SCR and the nitrogen oxide concentration at the outlet of the front-stage SCR; According to the calculated actual conversion efficiency of the front-stage SCR and the target conversion efficiency of the front-stage SCR, a correction coefficient of the urea injection amount of the front-stage SCR is obtained; The final urea injection amount of the front-stage SCR is obtained according to the obtained correction coefficient of the urea injection amount of the front-stage SCR and the theoretical urea injection amount of the front-stage SCR.

8. A dual-stage SCR urea injection control method as claimed in claim 6, characterized in that: The calculation of the urea injection amount based on the front-stage SCR ammonia storage target specifically includes: According to the temperature of the front-stage SCR, check the pre-set MAP table to determine the target ammonia storage capacity of the front-stage SCR; According to the deviation between the target ammonia storage amount of the front-stage SCR and the actual ammonia storage amount of the front-stage SCR, the ammonia required for ammonia storage control is obtained through PID control; The ammonia demand is obtained based on the ammonia required for ammonia storage control and the ammonia required for the front-stage SCR to convert nitrogen oxides; The ammonia demand is converted into the urea demand to obtain the urea injection amount of the front-stage SCR.

9. A dual-stage SCR urea injection control device, characterized in that: The dual-stage SCR urea injection quantity control device comprises: A determination module, which is used to obtain the real-time working mode of the engine and determine the control mode of the front-stage SCR and the rear-stage SCR according to the obtained working mode; An execution module, which is used to calculate the corresponding urea injection amount of the front-stage SCR and the rear-stage SCR based on the determined control mode, and switch the control mode according to the working state of the SCR; The control modes of the front-stage SCR include an initial mode, a target efficiency mode, and a high efficiency mode, and the control modes of the rear-stage SCR include an initial mode and a high efficiency mode.

10. A two-stage SCR urea injection quantity control device, characterized in that: The dual-stage SCR urea injection quantity control device comprises a processor, a memory, and a dual-stage SCR urea injection quantity control program stored in the memory and executable by the processor, wherein when the dual-stage SCR urea injection quantity control program is executed by the processor, the steps of the dual-stage SCR urea injection quantity control method according to any one of claims 1 to 8 are implemented.

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