Two-stage SCR urea injection quantity control method, device and equipment

Abstract

The present invention discloses a dual-stage SCR urea injection quantity control method, device and equipment, relating to the technical field of engine exhaust aftertreatment. The method comprises obtaining the real-time operating mode of the engine and determining the control mode of the front-stage SCR and the rear-stage SCR according to the obtained operating mode; based on the determined control mode, the front-stage SCR and the rear-stage SCR perform corresponding urea injection quantity calculations, and switch the control mode according to the operating state of the SCR; wherein the control mode of the front-stage SCR includes an initial mode, a target efficiency mode, and a high-efficiency mode, and the control mode of the rear-stage SCR includes an initial mode and a high-efficiency mode. The present application determines the coordinated control state of the dual-stage SCR according to the engine operating mode, more effectively reduces nitrogen oxide emissions for different operating modes, and also considers the influence of the DPF state on the coordinated control of the dual-stage SCR, thereby achieving efficient coordinated control of the urea injection quantity of the dual-stage SCR.

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 treat the 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 improved. 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] Currently, the common method for controlling dual-stage SCR systems is to obtain the real-time inlet temperatures of the primary and secondary SCRs, determine the SCR coordinated control state based on these two temperatures, and then determine the urea injection rate for the primary and secondary SCRs based on the SCR coordinated control state. However, this control method only determines the SCR coordinated control state based on the primary and secondary SCR inlet temperatures, fails to consider the needs of different engine operating conditions, and does not consider the relationship between dual-stage SCR control and the DPF. Summary of the Invention

[0004] The present application provides a dual-stage SCR urea injection amount control method, device and equipment. By determining the coordinated control state of the dual-stage SCR according to the engine operating mode, nitrogen oxide emissions are more effectively reduced for different operating modes. At the same time, the influence of the DPF state on the coordinated control of the dual-stage SCR is also considered, thereby achieving 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] Obtaining the real-time working mode of the engine, and determining the control mode of the front-stage SCR and the rear-stage SCR according to the obtained 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 status of the SCR;

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

[0009] In conjunction with the first aspect, in one embodiment,

[0010] The working mode of the engine includes 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 the default mode, the economic mode, and the power mode;

[0012] The special mode is a special operating mode that the engine enters to achieve specific effects, including regeneration mode and 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 pre-stage SCR heating mode, a DOC heating mode, and a post-stage SCR heating mode.

[0015] In combination with the first aspect, in one embodiment, 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 engine is in a normal operating mode, the initial control mode of the front-stage SCR is determined to be a target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be a 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 conjunction with the first aspect, in one embodiment,

[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 conjunction with the first aspect, in one embodiment,

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

[0027] In conjunction with the first aspect, in one embodiment,

[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 efficiency target of the front-stage SCR;

[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 embodiment, the calculating of the urea injection amount based on the pre-stage SCR efficiency target specifically includes:

[0034] Determine the pre-stage SCR basic efficiency target based on the pre-stage SCR inlet temperature, exhaust flow, and the current operating mode of the engine;

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

[0036] Determining 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 pre-SCR inlet, the exhaust flow rate of the pre-SCR, and the pre-SCR temperature;

[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 for 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 front-stage SCR inlet and the nitrogen oxide concentration at the front-stage SCR outlet;

[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 pre-stage SCR is obtained according to the obtained pre-stage SCR urea injection amount correction coefficient and the theoretical urea injection amount of the pre-stage SCR.

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

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

[0045] According to the deviation between the target ammonia storage capacity of the front-stage SCR and the actual ammonia storage capacity 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 conversion of nitrogen oxides by the pre-stage SCR;

[0047] The ammonia demand is converted into 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 quantity control device, the dual-stage SCR urea injection quantity 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 for 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 the initial mode, the target efficiency mode, and the high-efficiency mode, and the control modes of the rear-stage SCR include the initial mode and the 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 of the technical solutions provided in the embodiments of the present application include:

[0054] By acquiring the real-time operating mode of the engine and determining the control modes of the front-stage SCR and the rear-stage SCR according to the acquired operating mode, the front-stage SCR and the rear-stage SCR calculate the corresponding urea injection amounts based on the determined control mode, and switch the control mode according to the operating state of the SCR. By determining the coordinated control state of the two-stage SCR according to the engine operating mode, nitrogen oxide emissions are more effectively reduced for different operating modes. At the same time, the influence of the DPF state on the coordinated control of the two-stage SCR is also considered, thereby achieving 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 this application;

[0056] Figure 2 This is the architecture diagram of the dual-stage SCR;

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

[0058] Figure 4 This is a schematic diagram of the hardware structure of the dual-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 present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

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

[0061] In one aspect, an embodiment of the present application provides a dual-stage SCR urea injection quantity control method, which coordinates the dual-stage SCR control according to the requirements of different engine operating conditions, and coordinates the urea injection quantity 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 quantity of the dual-stage SCR.

[0062] In one embodiment, referring to Figure 1 , Figure 1 This is a flow chart of the dual-stage SCR urea injection control method of this 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 status of the SCR;

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

[0066] See also Figure 2 The figure shows the architecture of the 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 engine operating mode is determined based on the engine operating state and / or engine operating conditions. The engine operating modes include normal mode and special mode. Normal mode is the operating mode in which the engine often operates for a long time, including default mode, economy mode, and power mode. Special mode is a special operating mode entered by the engine to achieve specific effects, including regeneration mode and exhaust temperature management mode. Regeneration mode includes DPF regeneration mode, pre-stage SCR desulfurization regeneration mode, post-stage SCR desulfurization regeneration mode, and decrystallization regeneration mode. Exhaust temperature management mode includes pre-stage SCR heating mode, DOC heating mode, and post-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 obtained working mode, specifically:

[0069] When the engine is in a normal operating mode, the initial control mode of the front-stage SCR is determined to be a target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be a 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 control mode of the corresponding front-stage SCR and rear-stage SCR selected based on the working condition characteristics of the special mode, the engineering personnel select the appropriate control mode of the front-stage SCR 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-stage SCR and the rear-stage SCR according to the acquired working mode also includes: before the temperature of the front-stage SCR and the rear-stage SCR reaches the urea injection temperature, the front-stage SCR and the rear-stage SCR are defaulted to the initial mode and urea injection is stopped.

[0073] In this 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 this application, the control mode is switched according to the change of the working state of the SCR. Specifically, the control mode switching of the subsequent SCR is as follows:

[0078] When the post-stage SCR is in high-efficiency mode, if the post-stage SCR temperature is lower than the minimum urea injection temperature, the post-stage SCR switches to initial mode. When the post-stage SCR temperature is no lower than the minimum urea injection temperature, the post-stage SCR switches to high-efficiency mode. The minimum urea injection temperature is a calibrated value, representing the lowest temperature at which urea can hydrolyze and react to convert nitrogen oxides in the SCR. This value is determined by engineering technicians through testing 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] Furthermore, in one embodiment, the urea injection amount is calculated based on the pre-stage SCR efficiency target, specifically including:

[0081] S201: Determine a pre-stage SCR basic efficiency target based on the pre-stage SCR inlet temperature, exhaust flow rate, and the current operating mode of the engine;

[0082] Specifically, according to different operating modes of the engine, different SCR basic efficiency target MAP maps are selected (for example, when the engine operating mode is the normal mode, the SCR basic efficiency target MAP map #01 is selected; when the engine operating mode is different special modes, the SCR basic efficiency target MAP maps #02, #03, etc. are selected; the number of SCR basic efficiency target MAP maps and the corresponding relationship with the engine operating modes are determined by engineering and technical personnel based on the number of engine operating modes and the degree of difference in operating conditions of each operating mode, and the number of SCR basic efficiency target MAP maps does not exceed the number of engine operating 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 map 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 map is a calibrable MAP, and the relationship between the front-stage SCR inlet temperature, exhaust flow rate and the SCR basic efficiency target is calibrated by the technician under a specific engine operating mode;

[0083] S202: Determine a first correction coefficient for the front-stage SCR efficiency target based on the DPF carbon load and the DPF temperature;

[0084] Specifically, the first correction coefficient of the pre-stage SCR efficiency target is obtained by checking the MAP according to the DPF carbon load and 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 this 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 front-stage SCR basic efficiency targets can be selected for different engine operating modes; the first correction coefficient is determined according to the DPF carbon load and the DPF temperature to correct the front-stage SCR target efficiency, so that when the working conditions are suitable for DPF passive regeneration, the front-stage SCR target efficiency is adjusted to promote DPF passive regeneration, extend the DPF active regeneration interval, reduce the DPF regeneration frequency, and thus reduce fuel consumption; the second correction coefficient of the front-stage SCR efficiency target 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 lowered 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 nitrogen oxides based on the nitrogen oxide concentration at the inlet of the pre-stage SCR, the exhaust flow rate of the pre-stage SCR, and the pre-stage SCR temperature;

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

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

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

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

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

[0096] S208: Obtaining a correction coefficient for the urea injection amount of the pre-stage SCR based on the calculated actual conversion efficiency of the pre-stage SCR and the target conversion efficiency of the pre-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 a final urea injection amount for the pre-SCR based on the obtained pre-SCR urea injection amount correction coefficient and the theoretical urea injection amount of the pre-SCR. Specifically, the pre-SCR urea injection amount correction coefficient is multiplied by the theoretical urea injection amount of the pre-SCR to obtain the final urea injection amount for the pre-SCR.

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

[0100] S211: Based on the temperature of the front-stage SCR, a preset MAP table is consulted to determine the target ammonia storage capacity of the front-stage SCR. The actual ammonia storage capacity of the front-stage SCR is the actual ammonia storage capacity of the SCR at the previous moment plus the ammonia newly entering the SCR and minus the ammonia consumed in converting nitrogen oxides.

[0101] S212: Obtaining ammonia required for ammonia storage control through PID control based on a deviation between a target ammonia storage amount of the front-stage SCR and an actual ammonia storage amount of the front-stage SCR;

[0102] S213: Obtaining an ammonia demand based on the ammonia required for ammonia storage control and the ammonia required for nitrogen oxide conversion by the preceding SCR;

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

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

[0105] It should be noted that, for the rear-stage SCR in 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 high-efficiency mode calculation method 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 operating mode of the engine and determines the control mode of the front-stage SCR and the rear-stage SCR according to the obtained operating 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 operating state of the SCR. By determining the coordinated control state of the dual-stage SCR according to the engine operating mode, nitrogen oxide emissions are more effectively reduced for different operating modes. At the same time, the influence of the DPF state on the coordinated control of the dual-stage SCR is also considered, thereby achieving efficient coordinated control of the urea injection amount of the dual-stage SCR.

[0107] In a second aspect, an embodiment of the present application further 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 status of the SCR; among which, 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] The functional implementation of each module in the dual-stage SCR urea injection quantity control device corresponds to each step in the dual-stage SCR urea injection quantity control method embodiment, and their functions and implementation processes are not described here one by one.

[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 with data processing capabilities, such as a personal computer (PC), a laptop computer, or a server.

[0112] Reference Figure 4 , Figure 4 Schematic diagram of the hardware structure of the dual-stage SCR urea injection quantity control device involved in the embodiment of the present application. 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, memory, and communication interface.

[0114] Communication interfaces include input / output (I / O) interfaces, physical interfaces, and logical interfaces, used to interconnect components within the dual-stage SCR urea injection quantity control device, as well as interfaces used to interconnect the dual-stage SCR urea injection quantity control device with other devices (e.g., other computing devices or user devices). Physical interfaces can be Ethernet, fiber, or ATM interfaces; user devices can be displays, keyboards, and other devices.

[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-purpose processor that can invoke a dual-stage SCR urea injection quantity control program stored in a memory and execute the dual-stage SCR urea injection quantity control method provided in the embodiments of the present application. For example, the general-purpose processor may be a central processing unit (CPU). The method executed when the dual-stage SCR urea injection quantity control program is invoked can be referenced to the various embodiments of the dual-stage SCR urea injection quantity control method of the present application and will not be further described here.

[0117] Those skilled in the art will understand that Figure 4 The hardware structure shown in the figure does not constitute a limitation to the present application and may include more or fewer components than shown in the figure, or a combination of certain components, or a different arrangement of components.

[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 the "first", "second" and "third" to different types.

[0119] In the description of the embodiments of this application, the words "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 this application should not be construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary," "for example," or "for example" is intended to present the relevant concepts in a concrete manner.

[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; “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 are included that appear in a specific order. However, it should be understood that these operations or steps may not be performed in the order in which they appear in the embodiments of the present application or may be performed in parallel. The sequence numbers of the operations are only used to distinguish between different operations, and the sequence numbers themselves do not represent any order of execution. In addition, these processes may include more or fewer operations, and these operations or steps may be performed 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 the necessary general hardware platform, of course, it can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, 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, magnetic disk, optical disk) as described above, and includes a number of instructions for enabling 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 do not 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 dual-stage SCR urea injection control method, characterized in that: The dual-stage SCR urea injection amount control method includes: Obtaining the real-time working mode of the engine, and determining the control mode of the front-stage SCR and the rear-stage SCR according to the obtained 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 status of the SCR; Among them, the control modes of the front-stage SCR include initial mode, target efficiency mode, and high efficiency mode, and the control modes of the rear-stage SCR include initial mode and high efficiency mode; 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.

2. The dual-stage SCR urea injection control method according to claim 1, characterized in that: The working mode of the engine includes 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 the default mode, the economic mode, and the power mode; The special mode is a special operating mode that the engine enters to achieve specific effects, including regeneration mode and 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 pre-stage SCR heating mode, a DOC heating mode, and a post-stage SCR heating mode.

3. A dual-stage SCR urea injection amount control method according to 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 engine is in a normal operating mode, the initial control mode of the front-stage SCR is determined to be a target efficiency mode, and the initial control mode of the rear-stage SCR is determined to be a 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 according to 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-stage SCR is the high-efficiency mode, if the temperature of the rear-stage SCR is lower than the minimum urea injection temperature, the rear-stage SCR switches to the initial mode, and when the temperature of the rear-stage SCR is not lower than the minimum urea injection temperature, the rear-stage SCR switches to the high-efficiency mode.

5. The dual-stage SCR urea injection control method according to 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 efficiency target of the front-stage SCR; 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.

6. A dual-stage SCR urea injection amount control method according to claim 5, characterized in that: The calculation of the urea injection amount based on the front-stage SCR efficiency target specifically includes: Determine the pre-stage SCR basic efficiency target based on the pre-stage SCR inlet temperature, exhaust flow, and the current operating mode of the engine; The first correction coefficient of the front-stage SCR efficiency target is determined based on the DPF carbon load and DPF temperature; Determining 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 pre-SCR inlet, the exhaust flow rate of the pre-SCR, and the pre-SCR temperature; 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 for the pre-stage SCR is obtained; Calculate the actual conversion efficiency of the front-stage SCR based on the nitrogen oxide concentration at the front-stage SCR inlet and the nitrogen oxide concentration at the front-stage SCR outlet; 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 pre-stage SCR is obtained according to the obtained pre-stage SCR urea injection amount correction coefficient and the theoretical urea injection amount of the pre-stage SCR.

7. The dual-stage SCR urea injection control method according to claim 5, characterized in that: The calculation of the urea injection amount based on the pre-stage SCR ammonia storage target specifically includes: Check the pre-set MAP table according to the temperature of the front-stage SCR to determine the target ammonia storage capacity of the front-stage SCR; According to the deviation between the target ammonia storage capacity of the front-stage SCR and the actual ammonia storage capacity 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 conversion of nitrogen oxides by the pre-stage SCR; The ammonia demand is converted into urea demand to obtain the urea injection amount of the front-stage SCR.

8. A dual-stage SCR urea injection quantity control device, characterized in that: The dual-stage SCR urea injection quantity control device includes: 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 for 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; Among them, the control modes of the front-stage SCR include initial mode, target efficiency mode, and high efficiency mode, and the control modes of the rear-stage SCR include initial mode and high efficiency mode; 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.

9. A dual-stage SCR urea injection quantity control device, characterized in that: The dual-stage SCR urea injection quantity control device includes 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 7 are implemented.

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