Urea injection dose determination method and device, computer equipment and storage medium

Abstract

The invention relates to the technical field of tail gas treatment, and discloses a urea injection dose determination method and device, computer equipment and a storage medium. The injection process that urea and hot waste gas enter a decomposition reaction tube under the full working condition of an engine is simulated, and if the impact temperature of the urea when colliding with the decomposition reaction tube meets the urea crystallization condition, the urea injection dose is determined. And the urea injection dosage at the moment is collected to serve as the maximum urea injection dosage allowed by the current working condition of the engine, meanwhile, the exhaust flow and the exhaust temperature of hot waste gas of the current working condition are collected, and then the impact mapping relation among the maximum urea injection dosage, the exhaust flow and the exhaust temperature is established. Therefore, the maximum urea injection dosage of the engine under various working conditions is determined according to the impact mapping relation, various applications and working conditions can be comprehensively covered, and practicability and accuracy are high.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment, and in particular to a method, a device, a computer device and a storage medium for determining a urea injection dosage. Background Art

[0002] Diesel exhaust contains a variety of harmful pollutants, which cause serious harm to the environment and human health. The exhaust system can use Selective Catalytic Reduction (SCR) to reduce nitrogen oxide emissions. The system mainly includes hot exhaust gas from the engine, diesel exhaust fluid (DEF) such as urea and a catalytic converter. The vaporized DEF and hot exhaust gas enter the Decomposition Reaction Pipe (DRP) in the catalytic converter. Since urea has a temperature range for starting to decompose, the temperature of the collision impact area generated when urea is sprayed into the decomposition reaction tube will decrease, thereby producing solid byproducts and forming urea crystals.

[0003] At present, there are methods in the prior art for controlling crystallization in the process of urea removal of nitrogen oxides. The urea injection amount is controlled by calculating the energy ratio between urea evaporation and exhaust. This method can reduce the risk of crystallization to a certain extent, but it is more of a theoretical calculation and cannot fully cover various application conditions, resulting in large errors. Summary of the invention

[0004] In view of this, the present invention provides a method, device, computer equipment and storage medium for determining urea injection dosage to solve the problem that the prior art controls the urea injection amount based on theoretical calculation, cannot fully cover various application conditions and has large errors.

[0005] In a first aspect, the present invention provides a method for determining a urea injection dosage, the method comprising:

[0006] The injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine operating conditions is simulated, and the impact temperature of urea when it collides with the decomposition reaction tube is collected;

[0007] In the simulation process of different engine working conditions, the maximum urea injection dosage and the exhaust flow rate and exhaust temperature of the hot exhaust gas are determined when the impact temperature meets the urea crystallization conditions;

[0008] Establishing an impact mapping relationship according to the maximum urea injection dosage, exhaust flow rate and exhaust temperature;

[0009] According to the impact mapping relationship, the target urea injection dosage under the target engine operating condition is obtained.

[0010] Beneficial effects: The embodiment of the present invention simulates the injection process of urea and hot exhaust gas entering the decomposition reaction tube under all engine working conditions. If the impact temperature of urea when colliding with the decomposition reaction tube meets the urea crystallization condition, the urea injection dose at this time is collected as the maximum urea injection dose allowed by the current engine working condition, and the exhaust flow rate and exhaust temperature of the hot exhaust gas in the current working condition are collected at the same time, and then the impact mapping relationship between the maximum urea injection dose, exhaust flow rate and exhaust temperature is established. Therefore, according to the impact mapping relationship, the maximum urea injection dose under various engine working conditions is determined, which can fully cover various applications and working conditions, and has strong practicality and high accuracy.

[0011] In some optional embodiments, determining the maximum urea injection dose when the shock temperature satisfies the urea crystallization condition comprises:

[0012] In the simulation process of the current working condition of the engine, the urea injection dosage is gradually increased according to the preset increment, and the impact temperature of the urea when it collides with the decomposition reaction tube is detected to see whether it meets the urea crystallization condition; wherein, the urea crystallization condition is that the impact temperature is less than the impact temperature threshold;

[0013] When it is detected that the impact temperature meets the urea crystallization condition, the current urea injection dosage is obtained to obtain the maximum urea injection dosage of the current engine operating condition.

[0014] Beneficial effect: When simulating each engine operating condition, the present invention gradually increases the urea injection dosage, and then detects the urea injection dosage when the shock temperature is less than the shock temperature threshold, and obtains the maximum urea injection dosage allowed by the corresponding operating condition, thereby analyzing the maximum dosage rate of urea injection under each engine condition before the urea shock may cause deposits, ensuring that the obtained shock mapping relationship can be applied to all operating conditions.

[0015] In some optional implementations, an impact mapping relationship is established according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature, including:

[0016] According to the exhaust flow rate and exhaust temperature under different engine working conditions, a binary group is constructed;

[0017] The association relationship between the binary group and the corresponding maximum urea injection dosage is constructed to obtain the impact mapping relationship.

[0018] Beneficial effects: The present invention constructs a binary group based on the exhaust flow rate and exhaust temperature under different engine operating conditions, and establishes a correlation between the binary group and the corresponding maximum urea injection dose, so as to use the obtained impact mapping relationship to control the urea injection dose under different operating conditions, and is conducive to improving the control accuracy.

[0019] In some optional implementations, obtaining a target urea injection dosage under a target engine operating condition according to the impact mapping relationship includes:

[0020] determining a target exhaust flow rate and a target exhaust temperature under a target engine operating condition;

[0021] According to the impact mapping relationship, the target exhaust flow rate and the target exhaust temperature, the target urea injection dosage is obtained by query.

[0022] Beneficial effect: The present invention determines the exhaust flow and exhaust temperature under the corresponding working conditions of the engine, and then uses the impact mapping relationship to query the target urea injection dosage, thereby achieving control of the urea injection dosage under all working conditions of the engine and effectively reducing the risk of deposit formation.

[0023] In some optional embodiments, after obtaining the target urea injection dosage under the target engine operating condition, the method further includes:

[0024] According to the target urea injection dosage, the exhaust system is controlled to perform urea injection;

[0025] If the presence of urea crystal deposits in the decomposition reaction tube is detected after the urea injection is completed, the urea injection dosage corresponding to the target operating condition in the impact mapping relationship is reduced.

[0026] Beneficial effects: The present invention performs urea injection verification according to the urea injection dosage of the corresponding working condition, detects whether there is urea crystal deposit in the decomposition reaction tube after the urea injection is completed, and adjusts the urea injection dosage in the impact mapping relationship according to the detection result, thereby improving the accuracy of the impact mapping relationship.

[0027] In some optional embodiments, the injection process of urea and hot exhaust gas into the decomposition reaction tube under full engine operating conditions is simulated, including:

[0028] Adjust the engine speed and engine load to make the engine enter different operating conditions and make the exhaust flow and exhaust temperature of the hot exhaust gas correspond to the operating conditions of the engine;

[0029] Urea is injected when the hot exhaust gas enters the exhaust system, so that the urea and the hot exhaust gas enter the decomposition reaction tube of the exhaust system together.

[0030] Beneficial effects: The present invention adjusts the engine speed and engine load to make the engine enter different working conditions, and makes the engine generate hot exhaust gas of corresponding working conditions, so as to adjust the exhaust flow rate and exhaust temperature. At the same time, urea is sprayed to mix urea and hot exhaust gas into the decomposition reaction tube, so as to simulate the process of urea and hot exhaust gas entering the decomposition reaction tube under different working conditions of the engine, so as to carry out full working condition testing, which is conducive to improving the comprehensiveness of scene coverage.

[0031] In some optional embodiments, before collecting the impact temperature when urea collides with the decomposition reaction tube, the method further includes:

[0032] Obtaining physical structural parameters of the decomposition reaction tube, and obtaining a collision area when urea reaches the decomposition reaction tube according to the physical structural parameters;

[0033] A temperature collection device is installed in the collision area, and the temperature collection device is used to collect the impact temperature when the urea collides with the decomposition reaction tube.

[0034] Beneficial effect: The present invention analyzes the collision area where urea is likely to collide with the inner wall of the decomposition reaction tube, and installs a temperature collection device in the corresponding area to collect the impact temperature when the urea collides with the decomposition reaction tube, and then adjusts the urea injection dosage according to the impact temperature, thereby improving the accuracy of the urea injection dosage test process.

[0035] In a second aspect, the present invention provides a device for determining a urea injection dosage, the device comprising:

[0036] The first processing module is used to simulate the injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine working conditions, and collect the impact temperature of urea when it collides with the decomposition reaction tube;

[0037] The second processing module is used to determine the maximum urea injection dosage and the exhaust flow rate and exhaust temperature of the hot exhaust gas when the impact temperature meets the urea crystallization condition during the simulation of different engine working conditions;

[0038] A third processing module is used to establish an impact mapping relationship according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature;

[0039] The fourth processing module is used to obtain a target urea injection dosage under a target engine operating condition according to the impact mapping relationship.

[0040] In a third aspect, the present invention provides a computer device, comprising: a memory and a processor, the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for determining the urea injection dose of the first aspect or any corresponding embodiment thereof by executing the computer instructions.

[0041] In a fourth aspect, the present invention provides a computer-readable storage medium having computer instructions stored thereon, the computer instructions being used to enable a computer to execute the method for determining a urea injection dosage of the first aspect or any corresponding embodiment thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 is a flow chart of a method for determining a urea injection dosage according to an embodiment of the present invention;

[0044] Figure 2 is a schematic diagram of a thermocouple installation position according to an embodiment of the present invention;

[0045] Figure 3 is a flow chart of another method for determining a urea injection dosage according to an embodiment of the present invention;

[0046] Figure 4 is a schematic diagram of a constant exhaust temperature and exhaust flow rate according to an embodiment of the present invention;

[0047] Figure 5 is a schematic diagram of the effect of urea injection amount on shock temperature according to an embodiment of the present invention;

[0048] Figure 6 is a schematic diagram of an impact map according to an embodiment of the present invention;

[0049] Figure 7 is a flow chart of another method for determining urea injection dosage according to an embodiment of the present invention;

[0050] Figure 8 is a structural block diagram of a device for determining a urea injection dosage according to an embodiment of the present invention;

[0051] Fig. 9 It is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0053] SCR uses basic chemistry to reduce nitrogen oxide emissions through a simple, efficient, safe and reliable process. The main components of the SCR process are hot exhaust gas, DEF and catalytic converter. The vaporized DEF and hot exhaust gas enter the catalytic converter located in the exhaust system. Due to the temperature range where urea begins to decompose, some urea will not be completely decomposed into gaseous products, but will be partially decomposed to produce solid by-products. If urea is partially decomposed when it is present on a solid surface, such as when the urea injection hits the mixer element or the DRP pipe wall, the solid decomposition by-products will adhere to the surface. Under the continuous collision of the urea spray, the temperature of the wall area will drop below 150°C. The formed liquid film is swept by the exhaust gas flow, undergoes a series of side reactions, and is deposited downstream of the injection area to form crystals.

[0054] At present, when controlling crystallization in the process of urea nitrogen oxide removal, relevant technologies often use theoretical formulas to evaluate the risk of urea crystallization, thereby controlling the urea injection amount. Although the risk of crystallization can be controlled to a certain extent, it is more of a theoretical calculation and open-loop control. The standards for crystallization risks are different for different catalytic converters and different scenarios, and it cannot fully cover various applications and working conditions, resulting in large errors.

[0055] Therefore, the embodiment of the present invention provides a method for determining the urea injection dose, which simulates the injection process of urea and hot exhaust gas entering the decomposition reaction tube under all engine working conditions. When it is detected that the impact temperature of urea when colliding with the decomposition reaction tube meets the urea crystallization condition, the maximum urea injection dose and the exhaust flow rate and exhaust temperature of the hot exhaust gas at this time are collected, and then the impact mapping relationship between the maximum urea injection dose, the exhaust flow rate and the exhaust temperature is established, so as to determine the urea injection dose under various engine working conditions, which can fully cover various applications and working conditions with high accuracy.

[0056] According to an embodiment of the present invention, an embodiment of a method for determining a urea injection dosage is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0057] In this embodiment, a method for determining a urea injection dosage is provided, which can be used for a computer device, such as a computer, to test the urea injection dosage. Figure 1 FIG. 4 is a flow chart of a method for determining a urea injection dosage according to an embodiment of the present invention. Figure 1 As shown, the process includes the following steps:

[0058] Step S101 , simulating the injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine operating conditions, and collecting the impact temperature of urea when it collides with the decomposition reaction tube.

[0059] In some optional embodiments, the physical structure parameters of the decomposition reaction tube are obtained, and based on the physical structure parameters, the collision area when the urea reaches the decomposition reaction tube is obtained, and a temperature collection device is installed in the collision area, and the temperature collection device is used to collect the impact temperature when the urea collides with the decomposition reaction tube.

[0060] In this embodiment, the test and determination process of the urea injection dose requires a DRP with an internal temperature acquisition device such as an instrument thermocouple. The thermocouple should be installed in any area of ​​the DRP where urea may hit the surface of the DRP. First, based on the physical structural parameters of the DRP such as size parameters, geometric structure, etc., a computational fluid dynamics (CFD) wall film analysis is performed to obtain the collision area to determine the position where urea may hit the inner wall of the DRP to guide the placement of the thermocouple. It should be noted that the urea injection dose in the present invention refers to the urea injection dose of the post-treatment system in each time step, which is essentially an injection dose rate, such as the urea injection dose within 1s.

[0061] It should be noted that CFD wall film analysis uses numerical calculation methods to solve fluid flow and heat transfer problems. By establishing a mathematical model, the physical problems of fluid flow (such as the continuity equation, momentum equation, and energy equation, etc.) are converted into a set of discrete equations that can be solved by a computer, thereby simulating and analyzing the flow phenomena, temperature changes and other physical properties of the fluid under various geometric shapes and boundary conditions. The specific implementation process can refer to the detailed description of the relevant technology, which will not be repeated here.

[0062] For example, Figure 2 As shown in the figure, the dots indicate the thermocouple installation positions. The thermocouples should be placed in the low-temperature deposition area (bottom of DRP, near the urea injection point). DRP needs to be installed with through holes to wire the thermocouples to the inside of DRP. The through holes should not be close to the thermocouple positions to prevent the thermocouples from affecting the temperature of the DRP wall. During the setup phase before testing the urea injection dose, it must be confirmed that the test unit in the computer equipment contains enough thermocouple channels to connect to the corresponding number of thermocouples on the decomposition reaction tube. The test unit can be installed with additional thermocouple channel plates to obtain a sufficient number of thermocouple channels.

[0063] The present invention analyzes the collision area where urea is likely to collide with the inner wall of the decomposition reaction tube, and installs a temperature collection device in the corresponding area to collect the impact temperature when the urea collides with the decomposition reaction tube, and then adjusts the urea injection dosage according to the impact temperature, thereby improving the accuracy of the urea injection dosage test process.

[0064] In some optional embodiments, the engine speed and engine load are adjusted to make the engine enter different operating conditions and make the exhaust flow rate and exhaust temperature of the hot exhaust gas correspond to the operating conditions of the engine. Then, urea is injected when the hot exhaust gas enters the exhaust system so that the urea and the hot exhaust gas enter the decomposition reaction tube of the exhaust system together. Generally, after the urea is injected, it will quickly mix with the hot exhaust gas and react in the DRP.

[0065] In the embodiment of the present invention, the switching of different engine working conditions is mainly achieved by adjusting the engine speed and the engine load. The exhaust flow rate and exhaust temperature of the hot exhaust gas generated by the engine under different working conditions are also different, so the engine speed and the engine load are used to adjust the exhaust flow rate and exhaust temperature conditions. It should be noted that the exhaust temperature measurement should be the temperature measurement closest to the upstream of the DRP inlet, so that the measured exhaust temperature can be guaranteed to be close to the actual exhaust temperature of the hot exhaust gas, thereby reducing the error.

[0066] The present invention adjusts the engine speed and the engine load to make the engine enter different working conditions, and makes the engine generate hot exhaust gas of corresponding working conditions, so as to adjust the exhaust flow rate and the exhaust temperature, and at the same time, injects urea to make the urea and the hot exhaust gas mix and enter the decomposition reaction tube, so as to simulate the process of urea and hot exhaust gas entering the decomposition reaction tube under different working conditions of the engine, thereby performing full working condition testing and improving the comprehensiveness of scene coverage.

[0067] Step S102, in the simulation process of different engine operating conditions, determining the maximum urea injection dosage when the impact temperature satisfies the urea crystallization condition and the exhaust flow rate and exhaust temperature of the hot exhaust gas.

[0068] Specifically, when DEF is injected into the exhaust system and diesel aftertreatment system, the DEF may coat or impact the inner wall of the exhaust system, and the area where the DEF impacts the inner surface will become a local cold spot due to heat transfer from the exhaust wall to the DEF. Due to this cooling, the impact area may be at risk of forming urea deposits.

[0069] In this embodiment, in the process of simulating each operating condition, the exhaust flow rate and exhaust temperature of the hot exhaust gas corresponding to the current operating condition are determined, and then the exhaust flow rate and exhaust temperature are fixed, and the urea injection dose is adjusted until the collected impact temperature meets the urea crystallization condition, which means that the urea injection dose at this time is the maximum urea injection dose allowed by the current operating condition. If the urea injection dose is increased, there will be a risk of generating urea crystal deposits.

[0070] Step S103: establishing an impact mapping relationship according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature.

[0071] Specifically, the testing and determination process of the urea injection dosage involves plotting the DRP wall temperature (i.e., the collected impact temperature) as a function of the exhaust temperature, exhaust flow rate, and urea injection dosage, thereby establishing an impact mapping relationship, wherein the temperature range, exhaust flow rate, and urea injection dosage should be determined based on the application conditions of the DRP.

[0072] Step S104, obtaining a target urea injection dosage under a target engine operating condition according to the impact mapping relationship.

[0073] Specifically, after obtaining the impact mapping relationship, the target urea injection dosage under the target working condition of the engine can be directly queried therein, so as to control the injection dosage of urea under the corresponding working condition and prevent urea from crystallizing and forming deposits. The present invention can cover various working conditions of the engine and has strong practicality.

[0074] The method for determining the urea injection dosage provided in this embodiment simulates the injection process of urea and hot exhaust gas entering the decomposition reaction tube under all engine working conditions. If the impact temperature of urea when colliding with the decomposition reaction tube meets the urea crystallization condition, the urea injection dosage at this time is collected as the maximum urea injection dosage allowed by the current engine working condition, and the exhaust flow rate and exhaust temperature of the hot exhaust gas in the current working condition are collected at the same time, and then the impact mapping relationship between the maximum urea injection dosage, exhaust flow rate and exhaust temperature is established. Therefore, according to the impact mapping relationship, the maximum urea injection dosage under various engine working conditions is determined, which can fully cover various applications and working conditions, and has strong practicality and high accuracy.

[0075] In this embodiment, a method for determining a urea injection dosage is provided, which can be used for a computer device, such as a computer, to test the urea injection dosage. Figure 3 FIG. 4 is a flow chart of a method for determining a urea injection dosage according to an embodiment of the present invention. Figure 3 As shown, the process includes the following steps:

[0076] Step S301, simulate the injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine operating conditions, and collect the impact temperature of urea when it collides with the decomposition reaction tube. Figure 1 The detailed description of step S101 in the illustrated embodiment will not be repeated here.

[0077] Step S302, in the simulation process of different engine operating conditions, determining the maximum urea injection dosage when the impact temperature satisfies the urea crystallization condition and the exhaust flow rate and exhaust temperature of the hot exhaust gas.

[0078] Specifically, the above step S302 includes:

[0079] Step S3021, during the simulation of different engine operating conditions, determine the exhaust flow rate and exhaust temperature of the hot exhaust gas.

[0080] Specifically, as the urea injection dose increases, urea will continue to cool the inner wall of the DRP and increase the risk of urea deposition. Therefore, in order to accurately measure the maximum urea injection dose allowed for any operating condition, when simulating the corresponding operating condition, the exhaust flow rate and exhaust temperature of the hot exhaust gas should be constant or fluctuate within a certain range to avoid large changes in exhaust flow rate and temperature affecting the accuracy of urea injection dose measurement. For example, the exhaust conditions that keep the exhaust flow rate and exhaust temperature constant are as follows: Figure 4 As shown in the figure, it can be seen that the exhaust temperature of the engine and the distribution of the exhaust temperature can be clustered, and the impact mapping point as the exhaust condition is selected. The urea impact test is performed according to the exhaust temperature and the exhaust temperature at the impact mapping point, wherein each impact mapping point corresponds to a different engine operating condition.

[0081] Step S3022, during the simulation of the current working condition of the engine, the urea injection dosage is gradually increased according to a preset increment, and the impact temperature of the urea when it collides with the decomposition reaction tube is detected to see whether it meets the urea crystallization condition.

[0082] Specifically, during the simulation process, the urea injection dosage should be increased in small increments so as to provide a good resolution for the mapping map when the mapping map is drawn according to the final impact mapping relationship. It should be noted that the increment of the urea injection dosage can be set according to the resolution requirements of the actual scene. The smaller the increment is set, the higher the resolution of the mapping map corresponding to the impact mapping relationship.

[0083] In some optional embodiments, the urea crystallization condition may be that the shock temperature is less than a shock temperature threshold. During the simulation test, the urea injection dose may be increased until the shock temperature exceeds a given shock temperature threshold. This ensures that when the shock temperature threshold needs to be adjusted, the shock mapping relationship already contains the maximum urea injection dose under the corresponding conditions, thereby avoiding waste of resources caused by repeated testing.

[0084] Step S3023, when it is detected that the impact temperature meets the urea crystallization condition, the current urea injection dosage is obtained to obtain the maximum urea injection dosage of the current engine operating condition.

[0085] Specifically, when the urea injection dose is gradually increased, the impact temperature of urea hitting the inner wall of DRP is detected in real time. If the impact temperature meets the urea crystallization condition, the urea injection dose at this time is taken as the maximum urea injection dose allowed by the corresponding working condition. In order to further improve the accuracy of the test results, the impact mapping test can be carried out according to the following steps:

[0086] Step a1: Run the engine at rated conditions for 20 minutes to remove DRP residual deposits in the exhaust aftertreatment system to prevent affecting the measurement accuracy. During the engine's rated condition operation, the urea injection dose should be kept at the minimum dose (e.g. 0.2 ml). If a large amount of deposits have formed in the DRP, it may take more than 20 minutes to remove them all.

[0087] Step a2, read the two-minute urea injection dose reading. If the test unit cannot obtain the urea injection dose reading, the dose consumption data within two minutes can be read through the recorder, and the average value can be calculated to obtain the urea injection dose reading at the corresponding moment. In this case, a flag can be added to the recorder data to obtain the urea injection dose reading at the corresponding moment to help data analysis.

[0088] Step a3, run the engine for 30 minutes under the corresponding working conditions to stabilize the exhaust temperature and exhaust flow. The recorder data can be checked to ensure that the exhaust temperature and exhaust flow have stabilized. It should be noted that the 30-minute stabilization time is a recommended value and can be adjusted as needed. During this interval, the urea injection dose should be kept at the minimum level (the minimum dose defined to maintain the health of the doser).

[0089] Step a4, after the 30-minute stabilization time is over, read the urea injection dosage reading and the shock temperature reading for two minutes.

[0090] Step a5, increase the urea injection dose to the next highest flow rate, and run stably at this dose for 10 minutes or until the shock temperature stabilizes. The shock temperature can be stabilized by checking the recorder data. The 10-minute stabilization time is a recommended value and can be adjusted as needed.

[0091] Step a6, after the 10-minute stabilization time is over, read the urea injection dosage reading and the shock temperature reading for two minutes.

[0092] Step a7: repeating steps a1 to a6 for each urea injection dosage under the specified exhaust temperature and exhaust flow conditions.

[0093] Step a8, repeating steps a1 to a7 for each exhaust gas temperature and exhaust gas flow rate condition.

[0094] Specifically, data from the above shock mapping test process is used to determine the maximum urea injection dose for each engine condition before urea shock may cause deposits. The process is based on the shock temperature collected by the thermocouple during the test at each injection dose rate. The maximum urea injection dose is determined based on the temperature drop of the thermocouple relative to the temperature collected by the same thermocouple and the absolute temperature of the thermocouple. If the shock temperature collected by the thermocouple is below the absolute temperature limit, there is a risk of deposit formation in the DRP.

[0095] It should be noted that the temperature drop limit and absolute temperature limit are related to the installation position of the thermocouple and the type of deposits formed, and the shock temperature threshold can be set based on these conditions. Figure 5 As shown in the figure, when the exhaust flow rate is 0.5 kg / s, as the urea injection dose increases per second (from 0.16 to 0.57), the impact temperature gradually decreases to 75°C; when the exhaust flow rate is 0.1 kg / s, as the urea injection dose increases per second (from 0.04 to 0.17), the impact temperature drops to 20°C. Figure 5 The temperature drops shown can be used as shock temperature thresholds for starting the test and adjusted as needed. These thresholds need to be verified against stored test data to ensure accuracy.

[0096] When simulating each engine working condition, the present invention gradually increases the urea injection dosage, and then detects the urea injection dosage when the shock temperature is less than the shock temperature threshold, and obtains the maximum urea injection dosage allowed by the corresponding working condition, thereby analyzing the maximum dosage rate of urea injection under each engine condition before the urea shock may cause deposits, ensuring that the obtained shock mapping relationship can be applied to all working conditions.

[0097] Step S303: establishing an impact mapping relationship according to the maximum urea injection dosage, exhaust flow rate and exhaust temperature.

[0098] Specifically, the above step S303 includes:

[0099] Step S3031, constructing a binary group according to the exhaust flow rate and exhaust temperature under different engine working conditions.

[0100] Specifically, the binary group is composed of exhaust flow and exhaust temperature, which can be calculated according to the following formula: Figure 4 The exhaust flow rate and exhaust temperature at the impact mapping point shown are used to construct binary groups corresponding to different working conditions.

[0101] Step S3032: constructing an association relationship between the binary group and the corresponding maximum urea injection dosage to obtain an impact mapping relationship.

[0102] Specifically, the maximum urea injection dose corresponding to each binary group is determined, and the association between the two is established to obtain the impact mapping relationship and draw the impact mapping diagram. For example, the impact mapping diagram is as follows: Figure 6 As shown, the maximum urea injection dosage under the corresponding working condition can be found according to the impact map.

[0103] The present invention constructs a binary group based on the exhaust flow rate and exhaust temperature under different engine working conditions, and establishes a correlation relationship between the binary group and the corresponding maximum urea injection dosage, so as to use the obtained impact mapping relationship to control the urea injection dosage under different working conditions and improve the control accuracy.

[0104] Step S304: obtaining a target urea injection dosage under a target engine operating condition according to the impact mapping relationship.

[0105] Specifically, the above step S304 includes:

[0106] Step S3041, determining the target exhaust flow and target exhaust temperature under the target operating condition of the engine.

[0107] For example, a comparison table of exhaust flow and exhaust temperature corresponding to the engine operating conditions may be established in advance, so as to quickly determine the target exhaust flow and target exhaust temperature corresponding to the target operating conditions.

[0108] Step S3042: Query and obtain the target urea injection dosage according to the impact mapping relationship, the target exhaust flow rate and the target exhaust temperature.

[0109] For example, see again Figure 6 , in the impact mapping diagram corresponding to the impact mapping relationship, query the target urea injection dosage corresponding to the target exhaust flow rate and the target exhaust temperature.

[0110] In some optional embodiments, the exhaust system is controlled to perform urea injection according to the target urea injection dosage. If urea crystal deposits are detected in the decomposition reaction tube after the urea injection is completed, the urea injection dosage corresponding to the target operating condition in the impact mapping relationship is reduced.

[0111] In some optional embodiments, after the shock heat mapping analysis is completed, it must be verified using steady-state deposit test data. The shock mapping test results may not change, but the maximum urea injection dose that marks the crystallization risk may need to be adjusted for each DRP crystallization type. The verification process is as follows:

[0112] Step b1, as a first step, before running other tests, previous steady-state deposit test data (if available) can be compared to see if the impact map is valid. Generally, under the exhaust temperature and exhaust flow conditions, if the urea injection dosage rate is high, deposits are expected to form; if the urea injection dosage rate is low under the exhaust temperature and exhaust flow conditions, deposits should not form.

[0113] Step b2, run non-accelerated deposit test conditions directly from the impact map with the complete engine and exhaust aftertreatment system. Control the exhaust temperature and exhaust flow through the engine speed and torque commands, and overwrite the urea dosage to the values ​​shown on the impact map, and run for a sufficient time. The duration can be adjusted according to the thermal management strategy and scenario needs. For example, a continuous run time of 20 hours can be selected based on the minimum acceptable time for deposit regeneration. The ideal result of the non-accelerated deposit test is the formation of small amounts of deposits that will not affect engine or aftertreatment performance and can be removed by thermal management. If the program or application does not have thermal management capabilities, the ideal result would be no deposits.

[0114] Additionally, the logger data must be checked to ensure the health of the engine and exhaust aftertreatment system throughout the test. Tests can be run with FTIR, NOx, and NH3 measurement systems at the exhaust pipe to ensure the health of the aftertreatment system.

[0115] Step b3, if there is no deposit in the DRP after the test, it may be necessary to increase the urea dosage value at the impact appropriately; if a large amount of deposits are generated, or the deposits affect the engine or aftertreatment performance, the urea dosage value must be reduced. For example, the urea value can be adjusted by changing the limit of each deposit.

[0116] Step b4, running at least six deposition test conditions to verify the impact map data, select six or more conditions to check different types of deposits and try to cover the temperature and exhaust flow space to ensure the accuracy of the impact map.

[0117] In some optional embodiments, the urea injection amount in the impact map can be compared with the calibrated urea injection amount command required to meet the emission requirements, such as WHTC, WHSC, WNTE and other emission cycles, which can be used to better adjust the urea injection amount to meet the emission requirements while mitigating the risk of deposit formation. The impact map can limit the urea dosage in certain areas, and if the urea injection amount limit cannot meet the emission cycle requirements, the design may need to be changed.

[0118] The method for determining the urea injection dosage provided in this embodiment determines the exhaust flow rate and exhaust temperature under the corresponding working condition of the engine, and then uses the impact mapping relationship to query and obtain the target urea injection dosage, thereby realizing the control of the urea injection dosage of the engine under all working conditions, and effectively reducing the risk of deposit formation. In addition, urea injection verification is performed according to the urea injection dosage of the corresponding working condition. After the urea injection is completed, whether there is urea crystallized deposit in the decomposition reaction tube is detected, and the urea injection dosage in the impact mapping relationship is adjusted according to the detection result, so as to improve the accuracy of the impact mapping relationship.

[0119] The method for determining the urea injection dosage of the present invention is described in detail below with reference to a specific application example. Figure 7 As shown, the application example includes the following steps:

[0120] Step 1, perform CFD wall film analysis to determine where urea may hit the inner wall of the DRP to help place the thermocouple. The thermocouple should be installed in any collision area in the DRP where urea may hit the DRP surface to measure the impact temperature of the decomposition reaction tube wall during the impact test.

[0121] Step 2, controlling engine speed and engine load to adjust exhaust flow and exhaust temperature conditions, the exhaust temperature at the SCR inlet can be mapped from 150°C to the maximum temperature during deposit regeneration (approximately 600°C), and the exhaust flow can be mapped from idle to maximum exhaust flow (usually rated).

[0122] Step 3, at the specified exhaust temperature and exhaust flow rate, the DEF dosage instruction is increased in small steps (from 0 ml / sec, 0.05 ml / sec, 0.1 ml / sec, 0.3 ml / sec, 0.7 ml / sec, 1.2 ml / sec) to find out when the impact temperature collected by any thermocouple drops to 150°C (the temperature of urea crystallization). The urea injection dosage at this time is defined as the maximum urea injection dosage allowed under the corresponding exhaust temperature and exhaust flow rate.

[0123] Step 4, generating the impact mapping data of the decomposition reaction tube under all engine working conditions. Specifically, determine the correlation between the three key input variables (exhaust temperature, exhaust flow, urea injection dosage) and the key output (impact temperature of the inner wall of the decomposition reaction tube), perform thermal mapping in the test unit where the decomposition reaction tube is located, determine the maximum urea injection dosage under each engine condition before urea impact may cause deposits, and generate the decomposition reaction tube impact thermal mapping data under all engine working conditions.

[0124] Step 5, determine the final urea injection strategy through emission cycle test impact mapping data such as the World Harmonized Transient Cycle (WHTC), the World Harmonized Stationary Cycle (WHSC), and the World-wide harmonized Non-transient Engine-testing Cycle (WNTE).

[0125] In this embodiment, a device for determining the urea injection dosage is also provided, which is used to implement the above-mentioned embodiments and preferred embodiments, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware of a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0126] This embodiment provides a device for determining a urea injection dosage, such as Figure 8 As shown, including:

[0127] The first processing module 801 is used to simulate the injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine working conditions, and collect the impact temperature of urea when it collides with the decomposition reaction tube;

[0128] The second processing module 802 is used to determine the maximum urea injection dosage and the exhaust flow rate and exhaust temperature of the hot exhaust gas when the impact temperature meets the urea crystallization condition during the simulation of different engine operating conditions;

[0129] The third processing module 803 is used to establish an impact mapping relationship according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature;

[0130] The fourth processing module 804 is used to obtain a target urea injection dosage under a target engine operating condition according to the impact mapping relationship.

[0131] In some optional implementations, the first processing module 801 is further configured to:

[0132] Adjust the engine speed and engine load to make the engine enter different operating conditions and make the exhaust flow and exhaust temperature of the hot exhaust gas correspond to the operating conditions of the engine;

[0133] Urea is injected when the hot exhaust gas enters the exhaust system, so that the urea and the hot exhaust gas enter the decomposition reaction tube of the exhaust system together.

[0134] In some optional embodiments, before collecting the impact temperature when urea collides with the decomposition reaction tube, the device is also used to:

[0135] Obtaining physical structural parameters of the decomposition reaction tube, and obtaining a collision area when urea reaches the decomposition reaction tube according to the physical structural parameters;

[0136] A temperature collection device is installed in the collision area, and the temperature collection device is used to collect the impact temperature when the urea collides with the decomposition reaction tube.

[0137] In some optional implementations, the second processing module 802 is further configured to:

[0138] In the simulation process of the current working condition of the engine, the urea injection dosage is gradually increased according to the preset increment, and the impact temperature of the urea when it collides with the decomposition reaction tube is detected to see whether it meets the urea crystallization condition; wherein, the urea crystallization condition is that the impact temperature is less than the impact temperature threshold;

[0139] When it is detected that the impact temperature meets the urea crystallization condition, the current urea injection dosage is obtained to obtain the maximum urea injection dosage of the current engine operating condition.

[0140] In some optional implementations, the third processing module 803 is further configured to:

[0141] According to the exhaust flow rate and exhaust temperature under different engine working conditions, a binary group is constructed;

[0142] The association relationship between the binary group and the corresponding maximum urea injection dosage is constructed to obtain the impact mapping relationship.

[0143] In some optional implementations, the fourth processing module 804 is further configured to:

[0144] determining a target exhaust flow rate and a target exhaust temperature under a target engine operating condition;

[0145] According to the impact mapping relationship, the target exhaust flow rate and the target exhaust temperature, the target urea injection dosage is obtained by query.

[0146] In some optional embodiments, after obtaining the target urea injection dosage under the target operating condition of the engine, the device is further used to:

[0147] According to the target urea injection dosage, the exhaust system is controlled to perform urea injection;

[0148] If the presence of urea crystal deposits in the decomposition reaction tube is detected after the urea injection is completed, the urea injection dosage corresponding to the target operating condition in the impact mapping relationship is reduced.

[0149] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0150] The device for determining the urea injection dosage in this embodiment is presented in the form of a functional unit, where the unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that executes one or more software or fixed programs, and / or other devices that can provide the above functions.

[0151] The embodiment of the present invention also provides a computer device having the above Figure 8 The device for determining the urea injection dosage is shown.

[0152] See also Fig. 9 , Fig. 9 is a schematic diagram of the structure of a computer device provided by an optional embodiment of the present invention, such as Fig. 9 As shown, the computer device includes: one or more processors 10, a memory 20, and interfaces for connecting various components, including high-speed interfaces and low-speed interfaces. Various components are connected to each other using different buses for communication, and can be installed on a common mainboard or installed in other ways as needed. The processor can process the instructions executed in the computer device, including instructions stored in or on the memory to display the graphical information of the GUI on an external input / output device (such as, a display device coupled to the interface). In some optional embodiments, if necessary, multiple processors and / or multiple buses can be used together with multiple memories and multiple memories. Similarly, multiple computer devices can be connected, and each device provides some necessary operations (for example, as a server array, a group of blade servers, or a multi-processor system). Fig. 9 A processor 10 is taken as an example.

[0153] The processor 10 may be a central processing unit, a network processor or a combination thereof. The processor 10 may further include a hardware chip. The hardware chip may be a dedicated integrated circuit, a programmable logic device or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general purpose array logic or any combination thereof.

[0154] The memory 20 stores instructions executable by at least one processor 10, so that the at least one processor 10 executes the method shown in the above embodiment.

[0155] The memory 20 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; the data storage area may store data created according to the use of the computer device, etc. In addition, the memory 20 may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some optional embodiments, the memory 20 may optionally include a memory remotely arranged relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0156] The memory 20 may include a volatile memory, such as a random access memory; the memory may also include a non-volatile memory, such as a flash memory, a hard disk or a solid state drive; the memory 20 may also include a combination of the above types of memory.

[0157] The computer device also includes an input device 30 and an output device 40. The processor 10, the memory 20, the input device 30 and the output device 40 may be connected via a bus or other means. Fig. 9 The example of connecting through bus is taken in the following.

[0158] The input device 30 can receive input digital or character information, and generate key signal input related to the user settings and function control of the computer device, such as a touch screen, a keypad, a mouse, a track pad, a touch pad, an indicator bar, one or more mouse buttons, a trackball, a joystick, etc. The output device 40 may include a display device, an auxiliary lighting device (e.g., an LED) and a tactile feedback device (e.g., a vibration motor), etc. The above-mentioned display device includes but is not limited to a liquid crystal display, a light emitting diode, a display and a plasma display. In some optional embodiments, the display device can be a touch screen.

[0159] The embodiment of the present invention also provides a computer-readable storage medium. The method according to the embodiment of the present invention can be implemented in hardware, firmware, or can be implemented as a computer code that can be recorded in a storage medium, or can be implemented as a computer code that is originally stored in a remote storage medium or a non-temporary machine-readable storage medium and will be stored in a local storage medium through a network download, so that the method described herein can be stored in such software processing on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only storage memory, a random access memory, a flash memory, a hard disk or a solid-state hard disk, etc.; further, the storage medium can also include a combination of the above types of memories. It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component that can store or receive software or computer code. When the software or computer code is accessed and executed by a computer, a processor, or hardware, the method shown in the above embodiment is implemented.

[0160] A part of the present invention may be applied as a computer program product, such as a computer program instruction, which, when executed by a computer, can call or provide the method and / or technical solution according to the present invention through the operation of the computer. Those skilled in the art should understand that the existence of the computer program instruction in a computer-readable medium includes, but is not limited to, a source file, an executable file, an installation package file, etc., and accordingly, the way in which the computer program instruction is executed by the computer includes, but is not limited to: the computer directly executes the instruction, or the computer compiles the instruction and then executes the corresponding compiled program, or the computer reads and executes the instruction, or the computer reads and installs the instruction and then executes the corresponding installed program. Here, the computer-readable medium may be any available computer-readable storage medium or communication medium accessible to the computer.

[0161] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A method for determining a urea injection dosage, characterized in that: The method comprises: The injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine operating conditions is simulated, and the impact temperature of urea when it collides with the decomposition reaction tube is collected; In the simulation process of different engine working conditions, the maximum urea injection dosage and the exhaust flow rate and exhaust temperature of the hot exhaust gas are determined when the impact temperature meets the urea crystallization conditions; Establishing an impact mapping relationship according to the maximum urea injection dosage, exhaust flow rate and exhaust temperature; According to the impact mapping relationship, a target urea injection dosage under the target operating condition of the engine is obtained.

2. The method according to claim 1, characterized in that: The step of determining the maximum urea injection dosage when the shock temperature satisfies the urea crystallization condition comprises: In the simulation process of the current working condition of the engine, the urea injection dosage is gradually increased according to the preset increment, and the impact temperature of the urea when it collides with the decomposition reaction tube is detected to see whether it meets the urea crystallization condition; wherein, the urea crystallization condition is that the impact temperature is less than the impact temperature threshold; When it is detected that the impact temperature meets the urea crystallization condition, the current urea injection dosage is obtained to obtain the maximum urea injection dosage of the current engine operating condition.

3. The method according to claim 2, characterized in that The step of establishing an impact mapping relationship according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature includes: According to the exhaust flow rate and exhaust temperature under different engine working conditions, a binary group is constructed; The association relationship between the binary group and the corresponding maximum urea injection dosage is constructed to obtain the impact mapping relationship.

4. The method according to claim 1, characterized in that: The step of obtaining a target urea injection dosage under a target engine operating condition according to the impact mapping relationship includes: determining a target exhaust flow rate and a target exhaust temperature under a target engine operating condition; The target urea injection dosage is obtained by querying according to the impact mapping relationship, the target exhaust flow rate and the target exhaust temperature.

5. The method according to claim 4, characterized in that After obtaining the target urea injection dosage under the target engine operating condition, the method further includes: controlling the exhaust system to perform urea injection according to the target urea injection dosage; If the presence of urea crystal deposits in the decomposition reaction tube is detected after the urea injection is completed, the urea injection dosage corresponding to the target operating condition in the impact mapping relationship is reduced.

6. The method according to any one of claims 1 to 5, characterized in that The simulation of the injection process of urea and hot exhaust gas into the decomposition reaction tube under full engine operating conditions includes: Adjust the engine speed and engine load to make the engine enter different operating conditions and make the exhaust flow and exhaust temperature of the hot exhaust gas correspond to the operating conditions of the engine; Urea is injected when the hot exhaust gas enters the exhaust system, so that the urea and the hot exhaust gas enter the decomposition reaction tube of the exhaust system together.

7. The method according to claim 6, characterized in that Before collecting the impact temperature when urea collides with the decomposition reaction tube, the method further includes: Acquiring physical structural parameters of the decomposition reaction tube, and obtaining a collision area when urea reaches the decomposition reaction tube according to the physical structural parameters; A temperature collection device is installed in the collision area, and the temperature collection device is used to collect the impact temperature when the urea collides with the decomposition reaction tube.

8. A device for determining urea injection dosage, characterized in that: The device comprises: The first processing module is used to simulate the injection process of urea and hot exhaust gas into the decomposition reaction tube under all engine working conditions, and collect the impact temperature of urea when it collides with the decomposition reaction tube; The second processing module is used to determine the maximum urea injection dosage and the exhaust flow rate and exhaust temperature of the hot exhaust gas when the impact temperature meets the urea crystallization condition during the simulation of different engine working conditions; A third processing module is used to establish an impact mapping relationship according to the maximum urea injection dosage, the exhaust flow rate and the exhaust temperature; The fourth processing module is used to obtain a target urea injection dosage under a target engine operating condition according to the impact mapping relationship.

9. A computer device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the method for determining the urea injection dosage according to any one of claims 1 to 7 by executing the computer instructions.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a computer to execute the method for determining the urea injection dosage according to any one of claims 1 to 7.

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