A method for calculating the temperature of an scr catalyst
By establishing the thermodynamic equation of the SCR catalyst support and calibrating it with measured temperature, a closed-loop calculation method was formed, which solved the calculation deviation and uniformity problems of the SCR temperature model and realized accurate calculation of urea demand.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANHUI ABBOT TESTING TECH CO LTD
- Filing Date
- 2026-04-20
- Publication Date
- 2026-07-14
AI Technical Summary
Existing SCR temperature models have large discrepancies between calculated and actual temperatures and poor catalyst temperature uniformity, making it impossible to accurately calculate urea demand.
By acquiring the geometric and thermodynamic physical properties of the SCR catalyst support, a thermodynamic equation is established, and fitting and calibration are performed using thermocouple-measured temperatures, forming a closed-loop calculation method of bench calibration, vehicle calibration, and real-time deviation correction.
The accurate calculation of the SCR catalyst support temperature model was achieved, reducing temperature deviation, improving catalyst temperature uniformity, and ensuring accurate calculation of urea demand.
Smart Images
Figure CN122385000A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for calculating the temperature of an SCR catalyst. Background Technology
[0002] Diesel internal combustion engines, a product of human industrial development, have become an indispensable part of people's lives. However, with the increasing number of cars in various countries, environmental pollution problems are becoming increasingly serious.
[0003] Studies have shown that selective catalytic reduction (SCR) systems are the best solution for effectively reducing nitrogen oxides (NOx) in off-engine aftertreatment. Typically, automotive aftertreatment systems only install an inlet temperature sensor on the SCR carrier, eliminating the outlet temperature sensor. Based on the SCR catalyst denitrification principle, accurate measurement of the internal temperature of the SCR carrier is necessary for precise calculation of urea requirements.
[0004] Therefore, how to solve the problem of large deviation between the calculated and actual temperatures of the existing SCRT temperature model and the poor temperature uniformity of the catalyst has become an urgent issue to be addressed. Summary of the Invention
[0005] The main objective of this invention is to provide a method for calculating the temperature of an SCR catalyst, thereby addressing the aforementioned technical problems.
[0006] To achieve the above objectives, the present invention proposes a method for calculating the temperature of an SCR catalyst, comprising: S1: Obtain the geometric and multiple thermodynamic and physical properties of the SCR catalyst support; S2: Based on the aforementioned geometric and thermodynamic physical properties, establish the thermodynamic equations for the SCR catalyst support; S3: Perform WHTC cycle tests on the engine bench, and fit and calibrate the thermodynamic equations by measuring the temperature of thermocouples arranged on the SCR carrier to obtain a preliminary SCR carrier center temperature model and outlet temperature model. S5: The initially calibrated model is transferred to the vehicle, and a second calibration is performed through road testing of the vehicle to correct the heat exchange parameters under the vehicle's operating conditions. S5: Using the calibrated SCRT temperature strategy model, calculate and output the center model temperature and outlet model temperature of the SCR catalyst support in real time.
[0007] In one embodiment, the geometric characteristic parameter is an inherent geometric constant of the carrier.
[0008] In one embodiment, the thermodynamic physical property parameters include the specific heat capacity parameter of the carrier material, the heat transfer coefficient between the carrier and the engine exhaust gas, the heat exchange coefficient between the carrier and the environment, and the heat exchange coefficient between the carrier and the vehicle's airflow.
[0009] In one embodiment, the step of establishing the thermodynamic equation of the SCR catalyst support based on the geometric and thermodynamic physical properties specifically includes: S21. Constructing a 3D model: A three-dimensional rectangular coordinate system is established with the geometric center of the SCR catalyst support as the origin, where the X-axis is the exhaust gas flow axis, the Y-axis is the carrier radial direction, and the Z-axis is the carrier circumferential direction. Based on the geometric characteristic parameters, a three-dimensional grid is divided. The grid size is adapted according to the number and size of the carrier pores, so that each grid unit corresponds to a single pore area of the carrier. The geometric parameters of the grid unit are obtained by decomposing and calculating the total parameters of the carrier. S22. Establish the three-dimensional energy conservation equation: Establish a three-dimensional unsteady energy conservation equation ;in For carrier density, , , These are the axial, radial, and circumferential thermal conductivity coefficients of the carrier, respectively. For the temperature of the grid cell carrier, The temperature of the exhaust gas corresponding to the grid cell; S23, Supplementary thermal conductivity parameters: The axial, radial, and circumferential thermal conductivity of the SCR carrier was measured through small-scale experiments. The steady-state hot plate method was used to test the thermal conductivity characteristics in each of the three directions, obtaining thermal conductivity values at different temperatures. This resulted in temperature-thermal conductivity characteristic curves, which were then entered into the calibration variable `ScrMdl_heatCondCoeff_CUR`. The X-axis represents the carrier temperature, and the Z-axis represents the thermal conductivity value in the corresponding direction, with units of W / m². ; S24. Boundary conditions and source term settings: The boundary conditions include: the exhaust gas temperature at the carrier inlet surface (X=0) is the compensated SCR inlet temperature; the carrier outlet surface (X=L, where L is the total axial length of the carrier) is an adiabatic boundary; the radial surface of the carrier (Y=R, where R is the carrier radius) undergoes convective heat transfer with the environment; and the circumferential surface (Z direction) is a periodic boundary. S25. Discretization and solution of equations: The three-dimensional energy conservation equations are discretized using the finite volume method, transforming the partial differential equations into a system of algebraic equations. Implicit Euler schemes are employed for time discretization, with a time step of [missing information]. The time interval is set to 5ms~50ms, and the temperature value of each grid cell is solved by iterative method. S26. Initial conditions set: During a cold start of the engine, the carrier temperature of all grid cells is equal to the current ambient temperature, i.e. The initial temperature of the exhaust gas is the same as the ambient temperature, and it gradually increases after the engine starts and is then input into the model.
[0010] In one embodiment, the step of real-time calculation and output of the center model temperature and outlet model temperature of the SCR catalyst support specifically includes: After obtaining the temperature of all grid cells, the temperature of the grid cells at the geometric center of the carrier (X=L / 2, Y=0, Z=0) is extracted as the temperature of the SCR carrier center model; the average temperature of all grid cells at the carrier exit surface (X=L) is extracted as the temperature of the SCR carrier exit model.
[0011] In one embodiment, the first end face of the SCR catalyst support is provided with three first thermocouples for detecting the uniformity of the support inlet temperature, and the plurality of first thermocouples are arranged in a ring at intervals.
[0012] In one embodiment, a second thermocouple for inlet center temperature calibration is provided at the axis of the first end face, and the angle between the second thermocouple and the line connecting any two of the first thermocouples is 120°.
[0013] In one embodiment, a third thermocouple for verifying the temperature at the outlet end of the carrier is provided at the center of the second end face of the SCR catalyst support.
[0014] In one embodiment, a fourth thermocouple for calibrating the center temperature of the SCR catalyst support is provided at the center of gravity of the support.
[0015] In the technical solution of this invention, the method for calculating the SCR catalyst temperature includes: S1: Obtain the geometric and multiple thermodynamic and physical properties of the SCR catalyst support; S2: Based on the aforementioned geometric and thermodynamic physical properties, establish the thermodynamic equations for the SCR catalyst support; S3: Perform WHTC cycle tests on the engine bench, and fit and calibrate the thermodynamic equations by measuring the temperature of thermocouples arranged on the SCR carrier to obtain a preliminary SCR carrier center temperature model and outlet temperature model. S4: Transfer the initially calibrated model to the vehicle and perform a second calibration through road testing of the vehicle to correct the heat exchange parameters under the vehicle's operating conditions. S5: Using the calibrated SCRT temperature strategy model, calculate and output the center model temperature and outlet model temperature of the SCR catalyst support in real time.
[0016] This technical solution forms a complete closed loop of bench calibration, vehicle calibration, and real-time deviation correction, which can solve the technical problems of large deviation between the calculated and actual temperatures of the existing SCRT temperature model and poor temperature uniformity of the catalyst. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0018] Figure 1 This is a schematic flowchart of the SCR catalyst temperature calculation method of the present invention; Figure 2 This is a schematic diagram of the structure of the SCR catalyst of the present invention; Figure 3 This is a graph showing the specific heat capacity and temperature of the present invention.
[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0021] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.
[0022] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0023] This invention provides a method for calculating the temperature of an SCR catalyst.
[0024] like Figure 1 As shown, the SCR catalyst temperature calculation method provided in this embodiment of the invention includes: S1: Obtain the geometric and multiple thermodynamic and physical properties of the SCR catalyst support.
[0025] The geometric characteristic parameters are inherent geometric constants of the carrier. These core set parameters, including carrier volume, carrier size, number of carrier pores, carrier weight, and carrier density, can be obtained from the SCR carrier manufacturer.
[0026] Thermodynamic physical properties generally include the specific heat capacity of the carrier material, the heat transfer coefficient between the carrier and the engine exhaust, the heat exchange coefficient between the carrier and the environment, and the heat exchange coefficient between the carrier and the vehicle's airflow.
[0027] like Figure 3 As shown, the specific heat capacity parameter of the SCR carrier is determined by the catalyst material and can be obtained through small-scale experiments on the SCR carrier. The specific heat capacity parameter is filled into the calibration variable ScrMdl_heatCpSpcOfCat_CUR, where the X-axis parameter is the exhaust gas temperature (unit: K) and the Z-axis parameter is the heat capacity value at the corresponding temperature (unit: J / (kg·K)).
[0028] The heat transfer coefficients of the SCR carrier material and engine exhaust gas temperature were obtained through WHTC cycle testing on the engine bench. The coefficients were determined by the fitting rate between the measured temperature of the thermocouple installed in the SCR carrier and the temperature of the SCRT model. The calibrated variables were ScrMdl_exhHeatTrfCoeff_CUR. The X-axis parameter represents the heat energy transferred by the exhaust gas (positively correlated with exhaust gas mass flow rate, exhaust gas specific heat capacity, and exhaust gas temperature, unit: W), and the Z-axis parameter represents the heat energy coefficient acting on the SCR carrier (unit: W / m²). When the model parameter following rate is less than the actual thermocouple value, increase the Z-axis exchange coefficient; when the model parameter following rate is greater than the actual thermocouple value, decrease the Z-axis exchange coefficient.
[0029] The heat exchange coefficient of the SCR carrier material and environmental parameters is obtained in practical application environments through engine bench WHTC cycles or vehicle road tests. It is determined by the fitting rate between the measured temperature of the thermocouple installed in the SCR carrier and the temperature of the SCRT model. The calibration variable is ScrMdl_htcTubeToAmb. The parameter X-axis represents the ambient temperature (unit: K), and the Z-axis represents the heat exchange coefficient between the SCR carrier and the ambient temperature (unit: W / m²). When the model parameter following rate is less than the actual thermocouple value, increase the Z-axis exchange coefficient; when the model parameter following rate is greater than the actual thermocouple value, decrease the Z-axis exchange coefficient.
[0030] The heat exchange coefficient between the SCR carrier material and the airflow generated by the vehicle's travel speed is obtained through road testing of the entire vehicle in a real-world application environment. It is determined by fitting the measured temperature of a thermocouple installed in the SCR carrier to the SCRT model temperature along the speed. The calibration variable is ScrMdl_ambHeatTrfCoeff_CUR. The parameters are: X-axis represents vehicle speed (km / h), and Z-axis represents the heat exchange coefficient generated between the SCR carrier and the vehicle speed (W / m²). When the model parameter following rate is less than the actual thermocouple value, increase the Z-axis exchange coefficient; when the model parameter following rate is greater than the actual thermocouple value, decrease the Z-axis exchange coefficient.
[0031] The thermal conductivity correction coefficients for the SCR catalyst support crystal faces were obtained. These correction coefficients were based on measurements of the exposure of active crystal faces of the catalyst. By adjusting the thermal conductivity coefficients in each direction in the three-dimensional energy conservation equation, the influence of differences in catalytic activity of different crystal faces on the thermal conduction of the support was compensated. The proportion of active crystal faces of the catalyst was determined by XRD patterns and TEM characterization. The axial, radial, and circumferential thermal conductivity of the support was tested using the steady-state hot plate method. The crystal face thermal conductivity correction coefficients were obtained by fitting the active crystal face proportions and entered into the calibration variable ScrMdl_crystalHeatCorr_CUR. The X-axis represents the proportion of active crystal faces (unit: %), and the Z-axis represents the corresponding correction coefficient. For example, when the active crystal face proportion is 60%, the correction coefficient is 1.05, and when the active crystal face proportion is 80%, the correction coefficient is 1.12. These correction coefficients are used to adjust the thermal conductivity coefficients in each direction in the three-dimensional energy conservation equation, compensate for the influence of differences in catalytic activity of different crystal faces on the thermal conduction of the support, and avoid calculation errors caused by differences in crystal face characteristics.
[0032] Of the specific heat capacity parameters and various heat transfer / exchange coefficients mentioned above, except for the specific heat capacity parameter which is a fixed curve, the other parameters are updated in real time according to the operating conditions. The ECU obtains the corresponding parameter values in real time by looking up the table through signals such as exhaust gas flow, ambient temperature, and vehicle speed collected by sensors, so as to ensure that the thermodynamic equation matches the current operating conditions.
[0033] S2: Based on the geometric and thermodynamic physical properties, establish the thermodynamic equations for the SCR catalyst support.
[0034] In this embodiment, the construction of a three-dimensional model consistent with the actual structure of the SCR carrier is specifically as follows: S21. Constructing a 3D model: A three-dimensional rectangular coordinate system is established with the geometric center of the SCR catalyst carrier as the origin. The X-axis is the exhaust gas flow axis, the Y-axis is the carrier radial direction, and the Z-axis is the carrier circumferential direction. Based on the geometric characteristic parameters, a three-dimensional grid is divided. The grid size is adapted according to the number and size of the carrier pores, so that each grid unit corresponds to a single pore area of the carrier. The geometric parameters of the grid unit are obtained by decomposing the total parameters of the carrier.
[0035] The mesh size is adapted to the number of pores and the wall thickness of the channels in the carrier. The mesh unit size is set to 0.1mm×0.1mm×0.5mm (X×Y×Z) to ensure that each mesh unit corresponds to a single channel area in the carrier, avoiding calculation deviations caused by multiple channels sharing a single mesh unit. The geometric parameters (volume, heat transfer area) of the mesh unit are calculated by decomposing the total parameters of the carrier. For example, the volume of a single mesh unit = total volume of the carrier ÷ total number of meshes, and the heat transfer area between a single mesh unit and the exhaust gas = total inner surface area of the channels in the carrier ÷ total number of meshes. After the mesh is divided, the mesh independence is verified to ensure that the mesh size is reasonable (the deviation of the calculation result after mesh densification is <0.5℃), avoiding the increase of ECU computing power burden due to excessively dense mesh and the impact of calculation accuracy on excessively sparse mesh.
[0036] S22. Establish the three-dimensional energy conservation equation: Establish the three-dimensional unsteady-state energy conservation equation: ; The carrier density, pre-input in step S1, is 2.8 g / cm³ in this embodiment. 3 (2800kg / m 3 ), which are intrinsic constants; The specific heat capacity of the carrier material at constant pressure is obtained by looking up a table in real time from the calibration variable ScrMdl_heatCpSpcOfCat_CUR, and it varies with the carrier temperature. : The rate of change of carrier temperature over time (unit: K / s), which is an intermediate variable to be solved; , , : These are the axial, radial, and circumferential thermal conductivity coefficients of the carrier (unit: W / ). Adjustments are made in conjunction with the crystal plane thermal conductivity correction coefficient; , , : These are the second-order partial derivatives of the carrier temperature in the axial, radial, and circumferential directions, respectively, reflecting the temperature gradient in each direction; Heat transfer coefficient between carrier and engine exhaust (unit: W / ) (), obtained from the real-time table lookup in step S1; Heat exchange area between a single grid cell and exhaust gas (unit: m²) 2 The mesh is calculated from step S21. The temperature of the exhaust gas corresponding to the grid cell (unit: K) is gradually obtained after compensation of the inlet temperature of the SCR carrier; : Temperature of the grid element carrier (unit: K), which is the quantity to be solved; Heat exchange coefficient between carrier and environment (unit: W / ) The result is obtained from the real-time table lookup in step S1, and includes the combined effects of natural convection and forced convection (airflow from vehicle movement). Heat exchange area between a single grid cell and the environment (unit: m²) 2 The mesh is calculated from step S21. Ambient temperature (unit: K), collected in real time by the vehicle ambient temperature sensor.
[0037] In this calculation equation, the heat of reaction of the denitrification reaction on the surface of the SCR catalyst is ignored. This heat is much smaller than the enthalpy change of the tail gas (engineering error <2%), which can effectively simplify the equation calculation without affecting the calculation accuracy.
[0038] S23, Supplementary thermal conductivity parameters: The axial, radial, and circumferential thermal conductivity of the SCR carrier was measured through small-scale experiments. The steady-state hot plate method was used to test the thermal conductivity characteristics in each of the three directions, obtaining thermal conductivity values at different temperatures. This resulted in temperature-thermal conductivity characteristic curves, which were then entered into the calibration variable `ScrMdl_heatCondCoeff_CUR`. The X-axis represents the carrier temperature, and the Z-axis represents the thermal conductivity value in the corresponding direction, with units of W / m². .
[0039] In this embodiment, a small sample (50mm×50mm×50mm) consistent with the actual SCR carrier material is selected to ensure that the crystal plane characteristics and microstructure of the sample are consistent with the actual carrier, thus avoiding test deviation.
[0040] The steady-state hot plate method is used for testing, which can accurately measure the thermal conductivity in different directions. During the test, the sample is fixed between the hot plate and the cold plate, and the temperature difference between the hot plate and the cold plate is controlled (set to 20℃). After the system reaches steady state, the heat flow through the sample is measured, and the thermal conductivity is calculated according to Fourier's law.
[0041] S24. Boundary conditions and source term settings: The boundary conditions include: the exhaust gas temperature at the carrier inlet surface (X=0) is the compensated SCR inlet temperature; the carrier outlet surface (X=L, where L is the total axial length of the carrier) is an adiabatic boundary; the radial surface of the carrier (Y=R, where R is the carrier radius) undergoes convective heat transfer with the environment; and the circumferential surface (Z direction) is a periodic boundary.
[0042] Inlet boundary (X=0): The exhaust gas temperature is the compensated SCR inlet temperature. This temperature can be compensated using a Kalman filter algorithm, combined with the average temperature of the upstream DOC (diesel oxidation catalyst) and DPF (particulate filter) systems of the SCR for joint correction, eliminating errors caused by single sensor measurement deviations and operating condition fluctuations. Specifically, the initial temperature is collected by a temperature sensor placed at the SCR inlet, and the temperatures at the DOC outlet and DPF outlet are also collected. The average temperature of the three is calculated, and then noise interference is filtered out using a Kalman filter algorithm to obtain the compensated inlet temperature, ensuring the accuracy of the inlet temperature.
[0043] The outlet boundary (X=L, where L is the total axial length of the carrier, L=300mm in this embodiment): is set as an adiabatic boundary, i.e. Because the SCR carrier outlet has no forced heat dissipation device, the heat loss is negligible.
[0044] Radial surface boundary (Y=R, R is the carrier radius, R=75mm in this embodiment): It exchanges heat with the environment via convection, the heat transfer coefficient is the obtained comprehensive heat exchange coefficient (including natural convection and forced convection), and the boundary conditions are as follows: .
[0045] Circumferential surface boundary (Z direction): Defined as a periodic boundary, i.e. Because the SCR carrier has a cylindrical structure, the circumferential temperature distribution is periodic, ensuring the rationality of the temperature distribution.
[0046] Source term setting: The source term ignores the heat of SCR reaction and only considers the heat input and output of exhaust gas convection heat transfer and ambient heat dissipation, that is, the source term is In which the convective heat transfer of exhaust gas is the heat flow input (when At that time, environmental heat dissipation is heat flow output ( (At that time), the setting of the source term clearly reflects the heat balance of the carrier.
[0047] S25. Discretization and solution of equations: The three-dimensional energy conservation equations are discretized using the finite volume method, transforming the partial differential equations into a system of algebraic equations. Implicit Euler schemes are employed for time discretization, with a time step of [missing information]. Set the time to 5ms~50ms, and solve for the temperature value of each grid cell using an iterative method.
[0048] In this embodiment, the finite volume method is used to discretize the three-dimensional energy conservation equation. This method is a mature method for solving the three-dimensional heat conduction equation in engineering. It has strong numerical stability and moderate computational load, which is suitable for the computing power of the vehicle ECU.
[0049] S26. Initial conditions set: During a cold start of the engine, the carrier temperature of all grid cells is equal to the current ambient temperature, i.e. The initial temperature of the exhaust gas is the same as the ambient temperature, and it gradually increases after the engine starts and is then input into the model.
[0050] During a cold start (before ignition), the SCR catalyst carrier is not heated by the exhaust gas, and the carrier temperature of all grid cells is equal to the current ambient temperature. For example, when the ambient temperature is 25℃, the initial temperature of all grid cells is 25℃ (298K), and when the ambient temperature is -10℃, the initial temperature is -10℃ (263K).
[0051] During the initial cold start of the engine, the exhaust gas temperature is the same as the ambient temperature. As the engine starts (after ignition), the exhaust gas temperature gradually increases. The SCR inlet temperature sensor collects the data in real time and inputs it into the model to ensure that the initial conditions are completely matched with the actual operating conditions, thus avoiding subsequent calculation errors caused by deviations in the initial temperature setting.
[0052] S3: Perform WHTC cycle tests on the engine bench, and fit and calibrate the thermodynamic equations by measuring the temperature of thermocouples placed on the SCR carrier to obtain preliminary SCR carrier center temperature model and outlet temperature model.
[0053] The SCR carrier is mounted on the engine test bench. K-type thermocouples (measurement accuracy ±0.5℃) are placed at the geometric center, outlet surface, and different radial positions of the carrier to ensure that the thermocouples are in close contact with the carrier and to avoid measurement errors. The engine ECU and test computer are connected to collect data such as exhaust gas flow rate, exhaust gas temperature, ambient temperature, and measured temperature of the carrier in real time. At the same time, the thermodynamic equation established in step S3 is imported into the ECU and the model calculation is started.
[0054] The WHTC (World Harmonized Transient Cycle) test was conducted, and supplementary tests were conducted under low-temperature conditions (-10℃ to 10℃) and transient conditions. The low-temperature conditions were achieved through an environmental simulation chamber, and the transient conditions covered the complete cycle of engine idling → acceleration → constant speed → deceleration. The test duration was no less than 120 minutes to ensure coverage of typical engine operating conditions.
[0055] Subsequently, the model-calculated temperatures (center temperature and outlet temperature) were compared with the thermocouple-measured temperatures in real time to calculate the deviation between the two. By adjusting the parameters in the thermodynamic equation (specific heat capacity of the carrier, heat transfer coefficient of the exhaust gas, and heat exchange coefficient of the environment), the deviation was gradually reduced.
[0056] During the bench calibration phase, the influence of the heat exchange coefficient between the SCR carrier and the vehicle's airflow is not considered (the vehicle speed is 0 during bench testing, so the coefficient is 0). Only the specific heat capacity parameters of the carrier material, the heat transfer coefficient between the carrier and the engine exhaust, and the heat exchange coefficient between the carrier and the environment are adjusted and calibrated.
[0057] When the deviation between the model-calculated temperature and the measured temperature is ≤ ±3℃, the preliminary calibration is completed, and the preliminary SCR carrier center temperature model and outlet temperature model are obtained. The calibrated parameters are stored in the ECU calibration module for subsequent vehicle calibration.
[0058] S5: The initially calibrated model is transferred to the vehicle, and a second calibration is performed through road testing of the vehicle to correct the heat exchange parameters under the vehicle's operating conditions.
[0059] In this embodiment, the preliminarily calibrated model is transferred to the vehicle ECU. Thermocouples consistent with those used in bench testing are arranged on the vehicle SCR carrier and connected to an on-board data recorder to collect data such as vehicle speed, ambient temperature, ambient pressure, exhaust gas parameters, measured carrier temperature, and calculated model temperature in real time.
[0060] When the deviation between the model-calculated temperature and the measured temperature is ≤ ±2℃ under vehicle operating conditions, a second calibration is completed to determine the final SCRT temperature strategy model. All calibrated parameters are then fixed to the ECU for subsequent real-time calculations.
[0061] S6: The center model temperature and outlet model temperature of the SCR catalyst support are calculated and output in real time using the calibrated SCRT temperature strategy model.
[0062] In this embodiment, based on the calibrated SCRT temperature strategy model, the center model temperature and outlet model temperature of the SCR carrier are calculated in real time according to the above thermodynamic equation solution process, with the calculation frequency consistent with the time step.
[0063] After obtaining the temperature of all grid cells, the temperature of the grid cells at the geometric center of the carrier (X=L / 2, Y=0, Z=0) is extracted as the temperature of the SCR carrier center model; the average temperature of all grid cells at the carrier exit surface (X=L) is extracted as the temperature of the SCR carrier exit model.
[0064] Please refer to Figure 2The SCR catalyst support has three first thermocouples for detecting the uniformity of the inlet temperature on its first end face. These first thermocouples are arranged in a ring with spacing between them. A second thermocouple for calibrating the inlet center temperature is located at the center of the first end face. The angle between the second thermocouple and any two of the first thermocouples is 120°. A third thermocouple for verifying the outlet temperature of the support is located at the center of the second end face. A fourth thermocouple for calibrating the center temperature of the support is located at the center of gravity of the SCR catalyst support.
[0065] The annular array of multiple first thermocouples is 5-15 mm away from the first end face of the SCR catalyst support. Similarly, the third thermocouple is also 5-15 mm away from the second end face of the SCR catalyst support.
[0066] Optionally, the distance between the first thermocouple and the third thermocouple and the end face is selected to be 10mm.
[0067] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they 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 invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.
[0068] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.
Claims
1. A method for calculating the temperature of an SCR catalyst, characterized in that, The method for calculating the SCR catalyst temperature includes: S1: Obtain the geometric and multiple thermodynamic and physical properties of the SCR catalyst support; S2: Based on the aforementioned geometric and thermodynamic physical properties, establish the thermodynamic equations for the SCR catalyst support; S3: Perform WHTC cycle tests on the engine bench, and fit and calibrate the thermodynamic equations by measuring the temperature of thermocouples arranged on the SCR carrier to obtain a preliminary SCR carrier center temperature model and outlet temperature model. S4: Transfer the initially calibrated model to the vehicle and perform a second calibration through road testing of the vehicle to correct the heat exchange parameters under the vehicle's operating conditions. S5: Using the calibrated SCRT temperature strategy model, calculate and output the center model temperature and outlet model temperature of the SCR catalyst support in real time.
2. The method for calculating the SCR catalyst temperature according to claim 1, characterized in that, The geometric characteristic parameters are inherent geometric constants of the carrier.
3. The method for calculating the SCR catalyst temperature according to claim 1, characterized in that, The thermodynamic physical properties include the specific heat capacity of the carrier material, the heat transfer coefficient between the carrier and the engine exhaust, the heat exchange coefficient between the carrier and the environment, and the heat exchange coefficient between the carrier and the vehicle's airflow.
4. The method for calculating the SCR catalyst temperature according to claim 1, characterized in that, The specific steps for establishing the thermodynamic equation of the SCR catalyst support based on the geometric and thermodynamic physical properties are as follows: S21. Constructing a 3D model: A three-dimensional rectangular coordinate system is established with the geometric center of the SCR catalyst support as the origin, where the X-axis is the exhaust gas flow axis, the Y-axis is the carrier radial direction, and the Z-axis is the carrier circumferential direction. Based on the geometric characteristic parameters, a three-dimensional grid is divided. The grid size is adapted according to the number and size of the carrier pores, so that each grid unit corresponds to a single pore area of the carrier. The geometric parameters of the grid unit are obtained by decomposing and calculating the total parameters of the carrier. S22. Establish the three-dimensional energy conservation equation: Establish a three-dimensional unsteady energy conservation equation ;in For carrier density, , , These are the axial, radial, and circumferential thermal conductivity coefficients of the carrier, respectively. For the temperature of the grid cell carrier, The temperature of the exhaust gas corresponding to the grid cell; S23, Supplementary thermal conductivity parameters: The axial, radial, and circumferential thermal conductivity of the SCR carrier was measured through small-scale experiments. The steady-state hot plate method was used to test the thermal conductivity characteristics in each of the three directions, obtaining thermal conductivity values at different temperatures. This resulted in temperature-thermal conductivity characteristic curves, which were then entered into the calibration variable `ScrMdl_heatCondCoeff_CUR`. The X-axis represents the carrier temperature, and the Z-axis represents the thermal conductivity value in the corresponding direction, with units of W / m². ; S24. Boundary conditions and source term settings: The boundary conditions include: the exhaust gas temperature at the carrier inlet surface (X=0) is the compensated SCR inlet temperature; the carrier outlet surface (X=L, where L is the total axial length of the carrier) is an adiabatic boundary; the radial surface of the carrier (Y=R, where R is the carrier radius) undergoes convective heat transfer with the environment; and the circumferential surface (Z direction) is a periodic boundary. S25. Discretization and solution of equations: The three-dimensional energy conservation equations are discretized using the finite volume method, transforming the partial differential equations into a system of algebraic equations. Implicit Euler schemes are employed for time discretization, with a time step of [missing information]. The time interval is set to 5ms~50ms, and the temperature value of each grid cell is solved by iterative method. S26. Initial conditions set: During a cold start of the engine, the carrier temperature of all grid cells is equal to the current ambient temperature, i.e. The initial temperature of the exhaust gas is the same as the ambient temperature, and it gradually increases after the engine starts and is then input into the model.
5. The method for calculating the SCR catalyst temperature according to claim 4, characterized in that, The specific steps for real-time calculation and output of the center model temperature and outlet model temperature of the SCR catalyst support are as follows: After obtaining the temperature of all grid cells, the temperature of the grid cells at the geometric center of the carrier (X=L / 2, Y=0, Z=0) is extracted as the temperature of the SCR carrier center model; the average temperature of all grid cells at the carrier exit surface (X=L) is extracted as the temperature of the SCR carrier exit model.
6. The method for calculating the SCR catalyst temperature according to claim 1, characterized in that, The first end face of the SCR catalyst support is provided with three first thermocouples for detecting the uniformity of the support inlet temperature, and the multiple first thermocouples are arranged in a ring at intervals.
7. The method for calculating the SCR catalyst temperature according to claim 6, characterized in that, A second thermocouple for inlet center temperature calibration is provided at the axis of the first end face, and the angle between the second thermocouple and any two of the first thermocouples is 120°.
8. The method for calculating the SCR catalyst temperature according to claim 6, characterized in that, A third thermocouple for verifying the temperature at the outlet of the carrier is provided at the center of the second end face of the SCR catalyst support.
9. The method for calculating the SCR catalyst temperature according to claim 6, characterized in that, A fourth thermocouple for calibrating the center temperature of the SCR catalyst support is provided at the center of gravity of the support.