A method, system and device for evaluating a rear nox sensor gas intake pipe

Abstract

The application discloses a kind of rear NOx sensor gas taking pipe evaluation method, system and equipment, belong to NOx detection technical field.The method is: the system model is obtained by modeling to entire aftertreatment system;Aftertreatment system is simulated by three-dimensional CFD;The outlet end surface of ASC catalytic unit and its downstream pipeline are modeled to obtain gas outlet end cone model, and the simulation of gas outlet end cone is simulated by three-dimensional CFD, and simulation boundary condition comes from the simulation result of aftertreatment system;The simulation result of gas outlet end cone is processed, and the ratio of the tip average speed and cross-sectional average speed of rear NOx sensor, the tip passive scalar mass proportion of rear NOx sensor, the flow proportion of each inlet hole of gas taking pipe and the deviation of the tip average NH3+HNCO mass fraction and cross-sectional average NH3+HNCO mass fraction of rear NOx sensor or the deviation of the tip average NOx mass fraction and cross-sectional average NOx mass fraction of rear NOx sensor are respectively used to evaluate the design of gas taking pipe, to ensure NOx detection accuracy.

Description

Technical Field

[0001] This invention relates to the field of NOx detection technology, and more specifically, to a method, system, device, and storage medium for evaluating a post-NOx sensor sampling tube. Background Technology

[0002] In diesel engine exhaust aftertreatment systems, the SCR (Selective Catalytic Reduction) catalyst is responsible for purifying NOx, a harmful emission from the engine. In the SCR catalyst, a mixture of NOx-containing exhaust gas and its reducing agent NH3 reacts under the action of the catalyst to produce N2 and H2O, thus achieving the purpose of removing NOx.

[0003] To meet the China VI emission control requirements for diesel engines, the SCR control technology approach is as follows: a NOx sensor is installed at both the inlet and outlet of the exhaust aftertreatment system. The inlet NOx sensor measures the NOx emitted from the engine itself, and the software algorithm uses this measurement to calculate the urea injection amount that meets the emission requirements. The outlet NOx sensor measures the residual NOx after purification by the SCR catalyst. If the NOx does not meet the standards, an on-board diagnostic alarm is triggered, reminding the driver that the vehicle needs maintenance and inspection.

[0004] Currently, the NOx sensor in the aftertreatment system of China VI diesel engines is typically installed on the outlet cone downstream of the ASC (ammonia slip catalyst) catalytic converter. This sensor has a fixed sampling location and a small sampling range, and the measured NOx concentration value differs from the average NOx concentration downstream of the ASC catalytic converter, potentially leading to misjudgments of the catalytic converter's purification effect by the on-board diagnostic system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned shortcomings of the prior art. The purpose of the present invention is to provide a method for evaluating the after-NOx sensor intake pipe, which is used to support the design of the after-NOx sensor intake pipe of the China VI diesel engine aftertreatment system, thereby improving the measurement accuracy of the after-NOx sensor.

[0006] The second objective of this invention is to provide a post-NOx sensor gas sampling tube evaluation system.

[0007] The third objective of this invention is to provide a computer device.

[0008] To achieve the first objective mentioned above, the present invention provides a method for evaluating a post-NOx sensor sampling tube, comprising the following steps: Step 1. Model the entire aftertreatment system to obtain a system model, which includes the aftertreatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, and post-NOx sensor; perform three-dimensional CFD simulation on the aftertreatment system; Step 2. Select the outlet end face of the ASC catalytic unit and its downstream pipeline to model and obtain the outlet end cone model. The outlet end cone model includes the tailpipe downstream of the ASC catalytic unit outlet, the end cone, the gas intake pipe, and the post-NOx sensor. The inlet boundary of the outlet end cone model is the outlet end face of the ASC catalytic unit, and the simulation boundary conditions of the inlet are obtained from the simulation results of the aftertreatment system. Perform three-dimensional CFD simulation on the outlet end cone. Step 3. Process the simulation results of the outlet cone model, and evaluate the design of the gas intake pipe based on the ratio of the average velocity at the tip of the rear NOx sensor to the average velocity across the cross section, the mass ratio of the passive scalar at the tip of the rear NOx sensor, the flow rate ratio of each inlet hole of the intake pipe, and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor and the average NH3+HNCO mass fraction across the cross section, or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor and the average NOx mass fraction across the cross section.

[0009] As a further improvement, in step 1, the calculated operating parameters include exhaust flow rate, exhaust temperature, urea aqueous solution injection flow rate, raw exhaust gas composition and its mass fraction, and after-treatment system outlet pressure. The source and exhaust gas of the system model can be set to air, with components including O2 and N2; or, the components and their mass fractions of the source and exhaust gas of the system model can be set according to the actual components under the calculation conditions, including CO2, H2O, O2, N2 and NOx. The simulation calculations include the physical phenomena of urea aqueous solution spraying, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea; or, the simulation calculations include the physical phenomena of urea aqueous solution spraying, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea and the NOx reduction reaction within the SCR catalytic unit. The post-treatment system is simulated and the coordinates of the outlet end face of the ASC catalytic unit, as well as the corresponding velocity, temperature, gas composition and its mass fraction, are output; or, the post-treatment system is simulated and the coordinates of the outlet end face of the ASC catalytic unit, as well as the corresponding velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition and its mass fraction, are output.

[0010] Furthermore, in step 2, the inlet boundary circular surface of the exhaust cone model is divided into several regions in both the circumferential and radial directions; All the regions have the same area; The velocity, temperature, gas composition and mass fraction of the gas are loaded onto the outlet end face of the ASC catalytic unit on the inlet boundary circular surface; or, the velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition and mass fraction of the gas are loaded onto the outlet end face of the ASC catalytic unit on the inlet boundary circular surface. Different passive scalars are set for the aforementioned regions, and the quality score value is set to 1 for each region. A flow interface is provided at each inlet hole of the gas intake pipe to extract the flow rate of each inlet hole.

[0011] Further, in step 3, the average NH3+HNCO mass fraction of all grid regions within a spatial range at the tip of the post-NOx sensor is extracted; simultaneously, the average NH3+HNCO mass fraction of the cross section passing through the tip of the post-NOx sensor and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the deviation between the average NH3+HNCO mass fraction at the tip of the post-NOx sensor (6) and the average NH3+HNCO mass fraction of the cross section is calculated. The smaller the deviation, the more reasonable the matching of the gas intake pipe, the end cone, and the mixer.

[0012] in, This refers to the deviation between the average NH3+HNCO mass fraction at the tip of the NOx sensor and the average NH3+HNCO mass fraction across the cross section. The average NH3+HNCO concentration is measured on the cross-section at the tip of the NOx sensor, perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. This represents the average concentration of NH3+HNCO within a spatial range at the tip of the NOx sensor.

[0013] Further, in step 3, when the gas composition output from the outlet end face of the ASC catalytic unit contains NOx, the average NOx mass fraction of all grid regions within a spatial range at the tip of the post-NOx sensor is extracted; simultaneously, the average NOx mass fraction of the cross section passing through the tip of the post-NOx sensor and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the deviation between the average NOx mass fraction at the tip of the post-NOx sensor and the average NOx mass fraction of the cross section is calculated. The smaller the deviation, the more reasonable the matching of the gas intake pipe, the outlet cone, and the mixer.

[0014] in, This refers to the deviation between the tip-average NOx mass fraction and the cross-sectional-average NOx mass fraction of the post-NOx sensor. The average NOx concentration is measured at the tip of the NOx sensor, on a cross-section perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. This represents the average NOx concentration over a spatial range at the tip of the NOx sensor.

[0015] Further, in step 3, the average velocity of all grid regions within a spatial range at the tip of the post-NOx sensor is extracted; simultaneously, the average velocity of the cross section passing through the tip of the post-NOx sensor and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the ratio of the average velocity at the tip of the post-NOx sensor to the average velocity of the cross section is calculated. The larger the ratio, the higher the sensitivity of the post-NOx sensor and the more reasonable the matching of the gas intake pipe, the outlet cone, and the mixer.

[0016] in, The ratio of the tip average velocity to the cross-sectional average velocity of the NOx sensor (6) is given. The average velocity value is the velocity at the tip of the NOx sensor (6) and on a cross section perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. The velocity average value is the velocity within a spatial range at the tip of the NOx sensor (6).

[0017] Further, in step 3, the masses of different passive scalars within a spatial range at the tip of the post-NOx sensor and the total mass of all passive scalars are extracted. The proportion of each passive scalar mass in the total passive scalar mass is calculated to obtain the proportion of the passive scalar mass at the tip of the post-NOx sensor. The closer the proportions of each passive scalar mass in the total passive scalar mass, the more reasonable the design of the gas sampling pipe, which can achieve balanced gas sampling from the outlet end face of the ASC catalytic unit.

[0018] in, This represents the proportion of the passive scalar mass within a spatial range at the tip of each NOx sensor in the total passive scalar mass. For the first time within a spatial range at the tip of the NOx sensor. iThe quality of a passive scalar, This refers to the total passive scalar mass within a spatial range at the tip of the NOx sensor. i ≤N, where N is the total number of passive scalars.

[0019] Further, in step 3, the inlet mass flow rate of each inlet hole of the gas extraction pipe along the hole axis is extracted. The inlet mass flow rate of each inlet hole is divided by the total inlet mass flow rate of all inlet holes to obtain the flow rate ratio of each inlet hole of the gas extraction pipe, which is used to measure the gas flow capacity of each inlet hole. The closer the flow rate ratio of each inlet hole is, the more reasonable the design of the gas extraction pipe is, and the more balanced the gas flow capacity of each hole is.

[0020] in, The flow rate percentage for each inlet orifice. For the gas intake tube (3) j The mass flow rate of each inlet orifice (5), The sum of the mass flow rates of all inlet orifices (5), j ≤M, where M is the total number of inlet holes (5) of the gas extraction pipe (3).

[0021] To achieve the second objective mentioned above, the present invention provides a post-NOx sensor gas sampling tube evaluation system, comprising: The system modeling module is used to model the entire aftertreatment system to obtain a system model, which includes the aftertreatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, and post-NOx sensor; and performs three-dimensional CFD simulation on the aftertreatment system; The outlet cone modeling module is used to select the outlet end face of the ASC catalytic unit and its downstream pipeline to model the outlet cone model. The outlet cone model includes the tailpipe downstream of the ASC catalytic unit outlet, the end cone, the gas intake pipe, and the post-NOx sensor. The inlet boundary of the outlet cone model is the outlet end face of the ASC catalytic unit, and the simulation boundary conditions of the inlet are derived from the simulation results of the aftertreatment system. Three-dimensional CFD simulation is performed on the outlet cone. The evaluation module is used to process the simulation results of the outlet cone model and evaluate the design of the gas intake pipe based on the ratio of the average velocity of the tip of the rear NOx sensor to the average velocity of the cross section, the mass ratio of the passive scalar at the tip of the rear NOx sensor, the flow rate ratio of each inlet hole of the gas intake pipe, and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor (6) and the average NH3+HNCO mass fraction at the cross section or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor (6) and the average NOx mass fraction at the cross section.

[0022] To achieve the above-mentioned objective three, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-mentioned method for evaluating a post-NOx sensor gas sampling tube.

[0023] Beneficial effects: Compared with the prior art, the advantages of this invention are as follows: This invention models and simulates the entire aftertreatment system, the outlet face of the ASC catalytic unit, and its downstream pipelines. The simulation results are then processed, and the design of the gas sampling pipe is evaluated based on the ratio of the average velocity at the tip of the post-NOx sensor to the average velocity across the cross-section, the mass ratio of the passive scalar of the post-NOx sensor, the flow rate ratio of each inlet orifice of the gas sampling pipe, and the deviation between the average NH3+HNCO mass fraction at the tip of the post-NOx sensor and the average NH3+HNCO mass fraction across the cross-section, or the deviation between the average NOx mass fraction at the tip of the post-NOx sensor and the average NOx mass fraction across the cross-section. This provides a theoretical basis for the design of the gas sampling pipe, thereby ensuring the accuracy of NOx detection. Attached Figure Description

[0024] Figure 1 This is a flowchart of the present invention; Figure 2 A schematic diagram showing the division of the inlet boundary circle of the exhaust cone model into several regions; Figure 3 This is a schematic diagram of the air intake tube inlet. Figure 4 This is a schematic diagram of the tip of the NOx sensor and the cross-section beyond the sensor tip; Figure 5 The calculation system model for the aftertreatment system uses either air or the actual components under operating conditions as the source exhaust gas, and compares the evaluation indicators with or without considering the NOx reduction reaction in the SCR catalytic unit during the calculation.

[0025] Wherein: 1-tailpipe, 2-end cone, 3-gas intake pipe, 4-outlet end face of ASC catalytic unit, 5-inlet hole, 6-rear NOx sensor tip. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments shown in the accompanying drawings.

[0027] See Figures 1-5 A method for evaluating a post-NOx sensor sampling tube includes the following steps: Step 1. Model the entire aftertreatment system to obtain the system model. The system model includes the aftertreatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, post-NOx sensor 6, and other components in the flow field.

[0028] The post-processing system was subjected to 3D CFD simulation, specifically including: The calculated operating parameters include exhaust flow rate, exhaust temperature, urea aqueous solution injection flow rate, raw exhaust gas composition and its mass fraction, and after-treatment system outlet pressure.

[0029] like Figure 5 As shown, the source and exhaust gases in the system model can be set to air, with components including O2 and N2. Alternatively, the components and their mass fractions of the source and exhaust gases in the system model can be set according to the actual components under the calculation conditions, including CO2, H2O, O2, N2, and NOx.

[0030] The simulation calculations include the physical phenomena of urea aqueous solution injection, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea (NOx reduction reaction is not considered). Alternatively, the simulation calculations include the physical phenomena of urea aqueous solution injection, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea, and the NOx reduction reaction within the SCR catalytic unit (NOx reduction reaction is considered).

[0031] The simulation calculation of the aftertreatment system outputs the coordinates of the grid on the outlet end face 4 of the ASC catalytic converter, along with the corresponding velocity, temperature, gas composition, and mass fraction. Alternatively, the simulation calculation of the aftertreatment system outputs the coordinates of the grid on the outlet end face 4 of the ASC catalytic converter, along with the corresponding velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition, and mass fraction. When the exhaust gas is air, the gas composition output from the outlet end face 4 of the ASC catalytic converter includes O2, N2, and H2O, NH3, and HNCO produced by urea aqueous solution injection, pyrolysis, and hydrolysis. When the exhaust gas is the actual operating condition exhaust composition including CO2, H2O, O2, N2, and NOx, the gas composition output from the outlet end face 4 of the ASC catalytic converter includes CO2, H2O, O2, N2, NOx, HNCO, and NH3. It should be noted that when the simulation model considers the NOx reduction reaction within the SCR catalytic converter, the output temperature and the mass fraction of each component will differ significantly compared to when the NOx reduction reaction within the SCR catalytic converter is not considered.

[0032] Step 2. Select the outlet end face 4 of the ASC catalytic unit and its downstream pipeline to model and obtain the outlet end cone model. The outlet end cone model includes the tail pipe 1, end cone 2, gas intake pipe 3, and post-NOx sensor 6 downstream of the ASC catalytic unit outlet. The inlet boundary of the outlet end cone model is the outlet end face 4 of the ASC catalytic unit. The simulation boundary conditions of the inlet are obtained from the simulation results of the aftertreatment system.

[0033] A three-dimensional CFD simulation of the exhaust cone was performed, specifically including: The inlet boundary circular surface of the exhaust cone model is divided into several regions in both the circumferential and radial directions, such as... Figure 2 As shown, all the regions described have the same area.

[0034] The velocity, temperature, gas composition, and mass fraction output at the outlet end face 4 of the ASC catalytic unit loaded on the inlet boundary circular surface. Alternatively, the velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition, and mass fraction output at the outlet end face 4 of the ASC catalytic unit loaded on the inlet boundary circular surface.

[0035] Different passive scalars were set for several regions, and the quality score value was set to 1 for each region.

[0036] A flow interface is provided at each inlet hole 5 of the gas intake pipe 3 to extract the flow rate of each inlet hole 5.

[0037] Step 3. Process the simulation results of the outlet cone model. Evaluate the design of the gas intake pipe 3 based on the ratio of the average velocity at the tip of the rear NOx sensor 6 to the average velocity across the cross section, the mass ratio of the passive scalar at the tip of the rear NOx sensor 6, the flow rate ratio of each inlet hole of the intake pipe 3, and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor 6 and the average NH3+HNCO mass fraction across the cross section, or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor 6 and the average NOx mass fraction across the cross section.

[0038] like Figure 5 As shown, when the exhaust gas in step 1 is air, the calculation in step 1 cannot take into account the NOx reduction reaction within the SCR catalytic unit. In step 3, the design of the gas intake pipe 3 is evaluated based on four dimensions: the ratio of the average velocity at the tip of the post-NOx sensor 6 to the average velocity across the cross section, the mass ratio of the passive scalar at the tip of the post-NOx sensor 6, the flow rate ratio of each inlet hole 5 of the gas intake pipe 3, and the deviation between the average NH3+HNCO mass fraction at the tip of the post-NOx sensor 6 and the average NH3+HNCO mass fraction across the cross section.

[0039] When the original exhaust gas in step 1 is the actual exhaust gas composition, but the calculation does not consider the NOx reduction reaction in the SCR catalytic unit, the design of the intake pipe 3 is evaluated based on five dimensions: the ratio of the average velocity at the tip of the rear NOx sensor 6 to the average velocity across the cross section, the mass ratio of the passive scalar at the tip of the rear NOx sensor 6, the flow rate ratio of each inlet hole of the intake pipe 3, the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor 6 and the average NH3+HNCO mass fraction across the cross section, and the deviation between the average NOx mass fraction at the tip of the rear NOx sensor 6 and the average NOx mass fraction across the cross section.

[0040] When the original exhaust gas is the actual exhaust composition and the calculation takes into account the NOx reduction reaction in the SCR catalytic unit, the design of the intake pipe 3 is evaluated based on four dimensions: the ratio of the average tip velocity to the average cross-sectional velocity of the rear NOx sensor 6, the mass ratio of the passive scalar at the tip of the rear NOx sensor 6, the flow rate ratio of each inlet hole of the intake pipe 3, and the deviation between the average NOx mass fraction at the tip of the rear NOx sensor 6 and the average NOx mass fraction at the cross-sectional area.

[0041] Specifically as follows: 1) Extract the average NH3+HNCO mass fraction of all grid regions within a spatial range at the tip 6 of the NOx sensor. Simultaneously, extract the average NH3+HNCO mass fraction of the cross-section at the tip of the NOx sensor 6, perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. The spatial range at the tip of the NOx sensor 6 is a cylinder with the tip as the axial center and the end face and side face containing two rows of gas intake holes of the sensor. Calculate the deviation between the average NH3+HNCO mass fraction at the tip of the NOx sensor 6 and the average NH3+HNCO mass fraction of the cross-section. This deviation is used to measure the difference between the average NH3+HNCO mass fraction of the gas taken by the NOx sensor and the average NH3+HNCO mass fraction of the gas in space. The smaller the deviation value, the more reasonable the matching of the gas intake pipe 3, the outlet cone 2, and the mixer.

[0042]

[0043] in, The deviation between the average NH3+HNCO mass fraction at the tip of the NOx sensor 6 and the average NH3+HNCO mass fraction across the cross section is considered. The average NH3+HNCO concentration is measured on the cross-section at the tip of NOx sensor 6, perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. This represents the average concentration of NH3+HNCO within a spatial range at the tip of the NOx sensor.

[0044] 2) When the gas composition output from the outlet end face 4 of the ASC catalytic unit contains NOx, the average NOx mass fraction of all grid regions within a spatial range at the tip of the NOx sensor 6 is extracted; simultaneously, the average NOx mass fraction of the cross section at the tip of the NOx sensor 6 and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the deviation between the average NOx mass fraction at the tip of the NOx sensor 6 and the average NOx mass fraction of the cross section is calculated, which is used to measure the difference between the average NOx mass fraction of the gas taken by the NOx sensor and the average NOx mass fraction of the gas in space; the smaller the deviation, the more reasonable the matching between the gas intake pipe 3, the outlet cone 2, and the mixer;

[0045] in, This represents the deviation between the average NOx mass fraction at the tip of the NOx sensor 6 and the average NOx mass fraction across the cross section. The average NOx concentration is measured at the tip of NOx sensor 6, on a cross-section perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. This represents the average NOx concentration over a spatial range at the tip of the NOx sensor 6.

[0046] 3) Extract the average velocity of all grid regions within a spatial range at the tip of the NOx sensor 6; simultaneously, extract the average velocity of the cross section at the tip of the NOx sensor 6 and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model; calculate the ratio of the average velocity at the tip of the NOx sensor 6 to the average velocity of the cross section, which is used to measure the sensitivity of the NOx sensor; the larger the ratio, the higher the sensitivity of the NOx sensor and the more reasonable the matching of the intake pipe 3, the outlet cone 2, and the mixer;

[0047] in, The ratio of the tip average velocity to the cross-sectional average velocity of the NOx sensor (6) is given. The average velocity value on the cross section at the tip of the NOx sensor (6) and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is given. The velocity average value is the velocity within a spatial range at the tip of the NOx sensor (6).

[0048] 4) Extract the mass of each passive scalar in all grid regions within a spatial range at the tip of the NOx sensor 6 and the total mass of all passive scalars. Calculate the proportion of each passive scalar's mass in the total passive scalar mass to obtain the proportion of the passive scalar mass at the tip of the NOx sensor 6. This proportion is used to measure the ability of gas in each grid region of the inlet boundary circle of the outlet cone model to reach the NOx sensor after passing through the gas intake tube 3. The closer the proportions of each passive scalar's mass in the total passive scalar mass, the more reasonable the design of the gas intake tube 3, and the more evenly gas can be taken from the outlet end face 4 of the ASC catalytic unit.

[0049] in, This represents the percentage of the passive scalar mass within a spatial range at the tip of each NOx sensor 6 in the total passive scalar mass. For the tip of the NOx sensor 6, within a spatial range, the first i The quality of a passive scalar, The total passive scalar mass within a spatial range at the tip of the NOx sensor 6. i ≤N, where N is the total number of passive scalars.

[0050] 5) Extract the inlet mass flow rate of each inlet hole 5 along the hole axis direction of the gas intake pipe 3. Divide the inlet mass flow rate of each inlet hole 5 by the total inlet mass flow rate of all inlet holes 5 to obtain the flow rate ratio of each inlet hole 5 of the gas intake pipe 3. This is used to measure the gas flow capacity of each inlet hole 5. The closer the flow rate ratio of each inlet hole is, the more reasonable the design of the gas intake pipe 3 is, and the more balanced the gas flow capacity of each hole is.

[0051] in, The flow rate percentage for each inlet orifice. For the gas intake tube (3) j The mass flow rate of each inlet orifice (5), The sum of the mass flow rates of all inlet orifices (5), j ≤M, where M is the total number of inlet holes (5) of the gas extraction pipe (3).

[0052] Based on the simulation results, five key indicators were obtained: the ratio of the average velocity at the tip of the NOx sensor to the average velocity across the cross section; the mass ratio of the passive scalar of the NOx sensor; the flow rate ratio of each inlet orifice of the gas sampling tube; and the deviation between the average NH3+HNCO mass fraction at the tip of the NOx sensor and the average NH3+HNCO mass fraction across the cross section, or the deviation between the average NOx mass fraction at the tip of the NOx sensor and the average NOx mass fraction across the cross section. The design parameters were continuously adjusted based on these five key indicators to obtain the optimal design value for the gas sampling tube, providing a theoretical basis for its design and ensuring the accuracy of NOx detection.

[0053] A post-NOx sensor sampling tube evaluation system, comprising: The system modeling module is used to model the entire aftertreatment system to obtain a system model. The system model includes the aftertreatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, and post-NOx sensor 6; and performs three-dimensional CFD simulation of the aftertreatment system. The outlet cone modeling module is used to select the outlet end face 4 of the ASC catalytic unit and its downstream pipeline to model the outlet cone model. The outlet cone model includes the tailpipe 1, end cone 2, gas intake pipe 3, and post-NOx sensor 6 downstream of the ASC catalytic unit outlet. The inlet boundary of the outlet cone model is the outlet end face 4 of the ASC catalytic unit. The simulation boundary conditions of the inlet are obtained from the simulation results of the aftertreatment system. Three-dimensional CFD simulation is performed on the outlet cone. The evaluation module processes the simulation results of the outlet cone model. It evaluates the design of the gas intake pipe 3 based on the ratio of the average velocity at the tip of the rear NOx sensor 6 to the average velocity across the cross section, the mass ratio of the passive scalar at the tip of the rear NOx sensor 6, the flow rate ratio of each inlet hole 5 of the intake pipe 3, and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor 6 and the average NH3+HNCO mass fraction across the cross section, or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor 6 and the average NOx mass fraction across the cross section.

[0054] A computer device includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method for evaluating a post-NOx sensor sampling tube.

[0055] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for evaluating a post-NOx sensor sampling tube, characterized in that, Includes the following steps: Step 1. Model the entire aftertreatment system to obtain a system model, which includes the aftertreatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, and post-NOx sensor (6); perform three-dimensional CFD simulation on the aftertreatment system; Step 2. Select the outlet end face (4) of the ASC catalytic unit and its downstream pipeline to model and obtain the outlet end cone model. The outlet end cone model includes the tail pipe (1), end cone (2), gas intake pipe (3), and post-NOx sensor (6) downstream of the outlet of the ASC catalytic unit. The inlet boundary of the outlet end cone model is the outlet end face (4) of the ASC catalytic unit. The simulation boundary conditions of the inlet are from the simulation results of the aftertreatment system. A three-dimensional CFD simulation was performed on the outlet cone. Step 3. Process the simulation results of the outlet cone model, and evaluate the design of the gas intake pipe (3) based on the ratio of the average velocity of the tip to the average velocity of the cross section of the rear NOx sensor (6), the mass ratio of the passive scalar at the tip of the rear NOx sensor (6), the flow ratio of each inlet hole (5) of the gas intake pipe (3), and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor (6) and the average NH3+HNCO mass fraction at the cross section or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor (6) and the average NOx mass fraction at the cross section.

2. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 1, the calculated operating parameters include exhaust flow rate, exhaust temperature, urea aqueous solution injection flow rate, raw exhaust gas composition and its mass fraction, and after-treatment system outlet pressure. The source and exhaust gas of the system model can be set to air, with components including O2 and N2; or, the components and their mass fractions of the source and exhaust gas of the system model can be set according to the actual components under the calculation conditions, including CO2, H2O, O2, N2 and NOx. The simulation calculations include the physical phenomena of urea aqueous solution spraying, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea; or, the simulation calculations include the physical phenomena of urea aqueous solution spraying, evaporation, and wall impact, as well as the pyrolysis and hydrolysis reactions of urea and the NOx reduction reaction within the SCR catalytic unit. The post-processing system is simulated and the coordinates of the grid on the outlet end face (4) of the ASC catalytic unit, as well as the corresponding velocity, temperature, gas composition and its mass fraction, are output; or, the post-processing system is simulated and the coordinates of the grid on the outlet end face (4) of the ASC catalytic unit, as well as the corresponding velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition and its mass fraction, are output.

3. The method for evaluating a post-NOx sensor sampling tube according to claim 2, characterized in that, In step 2, the inlet boundary circular surface of the exhaust cone model is divided into several regions in both the circumferential and radial directions; All the regions have the same area; The velocity, temperature, gas composition and mass fraction of the ASC catalytic unit are loaded onto the inlet boundary circular surface; or, the velocity, temperature, turbulent kinetic energy and dissipation rate, gas composition and mass fraction of the ASC catalytic unit are loaded onto the inlet boundary circular surface. Different passive scalars are set for the aforementioned regions, and the quality score value is set to 1 for each region. A flow interface is provided at each inlet hole (5) of the gas extraction pipe (3) to extract the flow rate of each inlet hole (5).

4. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 3, the average NH3+HNCO mass fraction of all grid regions within a spatial range at the tip of the post-NOx sensor (6) is extracted; at the same time, the average NH3+HNCO mass fraction of the cross section passing through the tip of the post-NOx sensor (6) and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the deviation between the average NH3+HNCO mass fraction at the tip of the post-NOx sensor (6) and the average NH3+HNCO mass fraction of the cross section is calculated. The smaller the deviation, the more reasonable the matching between the gas intake pipe (3), the end cone (2), and the mixer. in, The deviation between the tip-average NH3+HNCO mass fraction and the cross-sectional average NH3+HNCO mass fraction of the post-NOx sensor (6) is given. The average NH3+HNCO concentration is measured on the cross-section at the tip of the NOx sensor (6) and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. The average concentration of NH3+HNCO within a spatial range at the tip of the NOx sensor (6) is given.

5. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 3, when the gas component output from the outlet end face (4) of the ASC catalytic unit contains NOx, the average NOx mass fraction of all grid areas within a spatial range at the tip of the post-NOx sensor (6) is extracted; at the same time, the average NOx mass fraction of the cross section passing through the tip of the post-NOx sensor (6) and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the deviation between the average NOx mass fraction at the tip of the post-NOx sensor (6) and the average NOx mass fraction of the cross section is calculated. The smaller the deviation, the more reasonable the matching between the gas intake pipe (3), the outlet cone (2), and the mixer. in, The deviation between the tip-average NOx mass fraction and the cross-sectional average NOx mass fraction of the rear NOx sensor (6) is given. The average NOx concentration is measured at the tip of the NOx sensor (6) and on a cross section perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. The average NOx concentration within a spatial range at the tip of the NOx sensor (6) is given.

6. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 3, the average velocity of all grid regions within a spatial range at the tip of the post-NOx sensor (6) is extracted; simultaneously, the average velocity of the cross section passing through the tip of the post-NOx sensor (6) and perpendicular to the axis of the inlet boundary circular surface of the outlet cone model is extracted; the ratio of the average velocity at the tip of the post-NOx sensor (6) to the average velocity of the cross section is calculated. The larger the ratio, the higher the sensitivity of the post-NOx sensor (6) and the more reasonable the matching of the gas intake pipe (3), the outlet cone (2), and the mixer. in, The ratio of the tip average velocity to the cross-sectional average velocity of the NOx sensor (6) is given. The average velocity value is the velocity at the tip of the NOx sensor (6) and on a cross section perpendicular to the axis of the inlet boundary circular surface of the outlet cone model. The velocity average value is the velocity within a spatial range at the tip of the NOx sensor (6).

7. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 3, the masses of different passive scalars in all grid areas within a spatial range at the tip of the post NOx sensor (6) and the total mass of all passive scalars are extracted. The proportion of each passive scalar mass in the total passive scalar mass is calculated to obtain the proportion of the passive scalar mass at the tip of the post NOx sensor (6). The closer the proportions of each passive scalar mass in the total passive scalar mass, the more reasonable the design of the gas extraction pipe (3) is, and the more evenly the gas can be extracted from the outlet end face (4) of the ASC catalytic unit. in, The percentage of the passive scalar mass in the total passive scalar mass within a spatial range at the tip of each NOx sensor (6) is given. For the tip of the NOx sensor (6), within a spatial range, the first The quality of a passive scalar, The total passive scalar mass within a spatial range at the tip of the NOx sensor (6) is given. ≤N, where N is the total number of passive scalars.

8. The method for evaluating a post-NOx sensor sampling tube according to claim 1, characterized in that, In step 3, the inlet mass flow rate of each inlet hole (5) of the gas extraction pipe (3) along the hole axis direction is extracted. The inlet mass flow rate of each inlet hole (5) is divided by the total inlet mass flow rate of all inlet holes (5) to obtain the flow rate ratio of each inlet hole (5) of the gas extraction pipe (3), which is used to measure the gas flow capacity of each inlet hole (5). The closer the flow rate ratio of each inlet hole is, the more reasonable the design of the gas extraction pipe (3) is, and the more balanced the gas flow capacity of each hole is. in, The flow rate percentage for each inlet orifice. For the gas intake tube (3) j The mass flow rate of each inlet orifice (5), The sum of the mass flow rates of all inlet orifices (5), j ≤M, where M is the total number of inlet holes (5) of the gas extraction pipe (3).

9. A post-NOx sensor sampling tube evaluation system, characterized in that, include: The system modeling module is used to model the entire post-treatment system to obtain a system model, which includes the post-treatment system encapsulation cylinder, DOC catalytic unit, DPF catalytic unit, SCR catalytic unit, ASC catalytic unit, urea aqueous solution nozzle, mixer, and post-NOx sensor (6); and performs three-dimensional CFD simulation on the post-treatment system. The outlet cone modeling module is used to select the outlet end face (4) of the ASC catalytic unit and its downstream pipeline to model and obtain the outlet cone model. The outlet cone model includes the tail pipe (1), end cone (2), gas intake pipe (3), and post-NOx sensor (6) downstream of the outlet of the ASC catalytic unit. The inlet boundary of the outlet cone model is the outlet end face (4) of the ASC catalytic unit. The simulation boundary conditions of the inlet are derived from the simulation results of the aftertreatment system. A three-dimensional CFD simulation was performed on the outlet cone. The evaluation module is used to process the simulation results of the outlet cone model and evaluate the design of the gas intake pipe (3) based on the ratio of the average velocity of the tip to the average velocity of the cross section of the rear NOx sensor (6), the mass ratio of the passive scalar at the tip of the rear NOx sensor (6), the flow ratio of each inlet hole (5) of the gas intake pipe (3), and the deviation between the average NH3+HNCO mass fraction at the tip of the rear NOx sensor (6) and the average NH3+HNCO mass fraction at the cross section or the deviation between the average NOx mass fraction at the tip of the rear NOx sensor (6) and the average NOx mass fraction at the cross section.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the post-NOx sensor gas sampling tube evaluation method according to any one of claims 1-8.

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