Method, system and equipment for calculating non-exhaust particulate matter in closed chamber based on operation loss

Abstract

The present invention relates to the field of automobile emission testing technology, and discloses a method, system and device for calculating non-exhaust particulate matter in a closed chamber based on running loss, including: constructing a whole vehicle running model in a closed chamber; setting a collection tube in the whole vehicle running model; performing CFD simulation on the change of non-exhaust particulate flow field when the vehicle is running in the closed chamber; obtaining the particle concentration distribution according to CFD, respectively calculating the particle source mass flow rate and the first collected particle mass flow rate at the corresponding collection tube; calculating the ratio of the first collected particle mass flow rate to the particle source mass flow rate; fitting the preset vehicle speed and particle collection rate to obtain a fitting formula; calculating the second collected particle mass flow rate at the collection tube; and obtaining the non-exhaust particulate matter emission according to the second collected particle mass flow rate, the fitting formula, the travel speed and the vehicle running time. The advantages of the present invention are: it is used to accurately calculate the non-exhaust particulate matter emission of the whole vehicle including brake wear and tire wear.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile emission testing, and in particular to a method, system and device for calculating non-exhaust particulate matter in a closed chamber based on operating loss. Background Art

[0002] In addition to exhaust gas, vehicles also emit non-exhaust particulate matter when they are running. Non-exhaust particulate matter mainly includes brake wear particles and tire wear particles. The emission of non-exhaust particulate matter is an important part of urban air pollution, and its emission has a great impact on PM. 2.5 、PM 10 Studying and controlling the emission of these particles can help reduce air pollution levels and improve urban air quality.

[0003] Among the existing non-exhaust particulate matter testing technologies for motor vehicles, the more mature one is the bench test for components of the braking system. The disadvantage is that the braking system is separated from the whole vehicle and is not in line with the actual usage. There is also a wheel hub outer side collection cover device developed for brake wear, but this device can only collect particulate emissions generated by brake wear, and cannot collect particulate emissions from tire wear, and cannot test the overall emissions of the whole vehicle. In addition, the patent with application number CN115684496 A proposes a variable temperature running loss closed chamber test system, which can use the running loss closed chamber to test the change of particulate matter concentration in the closed chamber to analyze the overall emission of the whole vehicle, but it is limited by the unknown uniform distribution of solid particulate matter in the closed chamber, and it is not reasonable to simply use the concentration multiplied by the volume of the closed chamber to calculate the emissions of the whole vehicle. There will be a large deviation, and the final emission results of the whole vehicle cannot be obtained by using the running loss closed chamber.

[0004] In order to solve the above problems, the present application proposes a method and system for accurately calculating the non-exhaust particulate matter emissions of the entire vehicle based on an operating loss closed chamber. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method, system and equipment for calculating non-exhaust particulate matter based on a running loss closed chamber, which can be used to accurately calculate the non-exhaust particulate matter emissions of the entire vehicle including brake wear and tire wear, which helps to optimize vehicle design and reduce particulate matter emissions.

[0006] In a first aspect, the present invention provides a method for calculating non-exhaust particulate matter in a closed chamber based on operating losses, comprising the following steps:

[0007] Constructing a vehicle operation model in a closed room; setting a collection pipe in the vehicle operation model; performing CFD simulation on the change of non-exhaust particulate flow field when the vehicle is running in the closed room;

[0008] The particle concentration distribution in the closed room at different preset vehicle speeds is obtained according to CFD simulation, and the mass flow rate of the particle source and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model are calculated respectively; the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds is calculated to obtain the particle collection rate; the preset vehicle speed is used as the independent variable and the particle collection rate is used as the dependent variable to obtain the fitting formula;

[0009] The vehicle in the whole vehicle operation model is set to run at an arbitrary speed, and the second collected particulate matter mass flow rate of the collection tube at each moment during the vehicle operation time is calculated; the non-exhaust particulate matter emissions are obtained based on the second collected particulate matter mass flow rate, the fitting formula, the travel speed and the vehicle operation time.

[0010] Furthermore, the whole vehicle operation model is constructed in a 1:1 ratio according to the actual vehicle operation model; and the CFD simulation constructs the calculation domain according to the actual size of the closed chamber.

[0011] Furthermore, in the CFD simulation, a particle injection port is provided on the wheel hub of the front wheel of the vehicle, and a particle injection port is provided behind the position where the tire of the rear wheel contacts the ground; and a particle injection port is provided at the contact point between the brake pad and the brake disc.

[0012] Furthermore, the Realizable k-ε turbulence model is used in the CFD simulation to simulate the external flow field of the vehicle; the random turbulence trajectory model is used to simulate the closed indoor flow field and the multiphase motion of particles.

[0013] Furthermore, the Reynolds number is obtained through a vehicle operation model experiment, and the Reynolds number is applied to the CFD simulation.

[0014] Furthermore, the mass flow rate of the particle source is the sum of the mass flow rates at the front wheels, rear wheels and brake pads of the vehicle; the first collected particle mass flow rate is the product of the particle concentration at the collection pipe position in the corresponding vehicle operation model and the collection flow of the APS.

[0015] Furthermore, the APS collects the sampling concentration at the sampling tube in the whole vehicle operation model, and the product of the sampling concentration and the collection flow of the APS is the second collected particulate matter mass flow rate.

[0016] Furthermore, the non-exhaust particulate matter emissions obtained based on the second collected particulate matter mass flow rate, the fitting formula, the travel speed and the vehicle running time also include: the non-exhaust particulate matter emission mass flow rate of the vehicle in the whole vehicle operation model is the ratio of the second collected particulate matter mass flow rate and the particulate matter collection rate, and the non-exhaust particulate matter emissions are obtained by integrating the non-exhaust particulate matter emission mass flow rate and the fitting formula corresponding to the vehicle running time.

[0017] In a second aspect, the present invention provides a system for calculating non-exhaust particulate matter in a closed chamber based on operating losses, comprising:

[0018] Construction module: constructing a vehicle operation model in a closed room; setting a collection pipe in the vehicle operation model; performing CFD simulation on the change of non-exhaust particulate flow field when the vehicle is running in the closed room;

[0019] Simulation module: obtain the particle concentration distribution in the closed room at different preset vehicle speeds based on CFD simulation, calculate the particle source mass flow rate and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model respectively; calculate the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds to obtain the particle collection rate; use the preset vehicle speed as the independent variable and the particle collection rate as the dependent variable to fit and obtain the fitting formula;

[0020] Calculation module: Set the vehicle in the whole vehicle operation model to run at an arbitrary speed, calculate the second collected particulate mass flow rate of the collection tube at each moment during the vehicle operation time; obtain the non-exhaust particulate emission according to the second collected particulate mass flow rate, fitting formula, travel speed and vehicle operation time.

[0021] In a third aspect, the present invention provides an electronic device comprising a memory, a processor and a computer program; wherein the computer program is stored in the memory and is configured to be executed by the processor to implement the method described in the first aspect.

[0022] The present invention has the following technical effects:

[0023] The present application proposes a method for calculating non-exhaust particulate matter in a closed chamber based on operation loss. By constructing a vehicle operation model in a closed chamber and performing CFD simulation, the two are combined to calculate the non-exhaust emissions of the vehicle; the ratio of the mass flow rate of particulate matter at the collection pipe to the mass flow rate of the particulate matter source, that is, the particulate matter collection rate, is obtained through simulation; then, the second collected particulate matter mass flow rate at the collection pipe in the vehicle operation model is measured and calculated, and the vehicle operation time is integrated by combining the particulate matter collection rate and the travel speed to obtain the final non-exhaust particulate matter emissions of the vehicle;

[0024] The vehicle operation model in the closed room in this application is set according to the actual vehicle operation status to ensure that the model can accurately reflect the emission behavior of the vehicle;

[0025] The CFD simulation in this application uses the Realizable k-ε turbulence model and the random turbulence trajectory model, and sets various boundary conditions. The Reynolds number calculated based on the experiment is substituted into the model, which has high accuracy and reliability;

[0026] In the present application, the second collected particulate matter mass flow rate and the vehicle's travel speed that change with time are collected and integrated over time, so that the calculation result is more accurate;

[0027] This application can be used to test non-exhaust particulate matter of the whole vehicle, including brake wear and tire wear. The accuracy of the whole vehicle motion model and CFD simulation ensures the accuracy of the calculation results; the precise calculation of non-exhaust particulate matter emissions helps to optimize vehicle design, reduce particulate matter emissions, and provide a scientific basis for the formulation of stricter environmental protection regulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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.

[0029] Figure 1 It is a flow chart of a method for calculating non-exhaust particulate matter in a closed chamber based on operating loss provided in an embodiment of the present invention;

[0030] Figure 2 It is a structural schematic diagram of a whole vehicle running model in a closed room provided by an embodiment of the present invention;

[0031] Figure 3 A simplified closed chamber and vehicle model for CFD simulation provided by an embodiment of the present invention;

[0032] Figure 4 The wind speed distribution diagram from the left side view of the vehicle in the closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0033] Figure 5 The wind speed distribution diagram from the top view of the vehicle in the closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0034] Figure 6 The wind speed distribution diagram of the vehicle front view in the closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0035] Figure 7 The particle concentration distribution diagram from the left side view of the vehicle in the closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0036] Figure 8The particle concentration distribution diagram from the top view of the vehicle in the closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0037] Fig. 9 The particle concentration distribution diagram from the perspective of the vehicle's front view in a closed room when the vehicle speed is 40km / h, 80km / h and 120km / h respectively provided in the embodiment of the present invention;

[0038] Fig.10 The motion trajectory of particles at the front wheel at a vehicle speed of 120 km / h provided by an embodiment of the present invention;

[0039] Fig.11 The motion trajectory of particles at the rear wheel at a vehicle speed of 120 km / h provided by an embodiment of the present invention;

[0040] Fig.12 The particle movement trajectories from different perspectives of the vehicle provided by the embodiment of the present invention;

[0041] Fig.13 A schematic diagram of a fitting formula provided in an embodiment of the present invention.

[0042] In the figure, 1. chassis dynamometer; 2. front fan; 3. sampling port; 4. particulate matter testing equipment; 5. driver assistance; 6. air bag; 7. chiller; 8. plate heat exchanger; 9. copper grille; 10. circulation fan; 11. engine air intake pipe; 12. engine exhaust pipe; 13. fresh air system; 14. tail exhaust fan. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0044] Explain the following terms:

[0045] (1) CFD (Computational Fluid Dynamics) is a method of numerically calculating and analyzing fluid motion by establishing mathematical models and computer simulation technology. Through CFD simulation, the flow, heat transfer, mass transfer and chemical reaction behaviors of fluids under different conditions can be predicted, providing an important reference for engineering design and optimization.

[0046] (2) The Realizable k-ε turbulence model is a model used in computational fluid dynamics (CFD) to simulate turbulent flows. It is an improvement on the standard k-ϵ turbulence model to better predict complex flow phenomena such as rotational flow, strong adverse pressure gradient flow, and flow separation. The model improves the predictive ability of complex flow phenomena by improving the dissipation rate equation and considering the effects of rotation and curvature.

[0047] (3) Euler method is a first-order numerical method mainly used to solve ordinary differential equations with given initial values ​​(i.e. initial value problems). In the fields of mathematics and computer science, this method is regarded as the most basic type of explicit method for solving numerical ordinary differential equations. The basic idea of ​​Euler method is iteration, solving by successive substitutions, and finally achieving a certain accuracy requirement.

[0048] (4) Lagrange method, also known as Lagrange method, body method or tracking method, is a method to describe fluid motion. It is mainly used to study the change law of motion parameters (such as position coordinates, velocity, acceleration, etc.) of each fluid particle over time. By combining the changes in motion parameters of all fluid particles, the motion law of the entire fluid can be obtained.

[0049] (5) The random turbulence trajectory model is another model that describes the motion of particles in turbulence. This model is based on the Lagrangian viewpoint, which tracks the motion trajectories of fluid microclusters or particles in the turbulent field. It introduces random terms to simulate the influence of turbulent pulsations on particle motion, thereby describing the diffusion and mixing process of particles in the turbulent field.

[0050] (6) The running loss closed chamber is a fully enclosed environmental chamber for testing non-exhaust HC emissions generated by the vehicle during driving, and is equipped with engine intake and exhaust pipes, etc. When the vehicle is placed on the chassis dynamometer in the closed chamber and driving, the vehicle intake and exhaust are connected to the engine intake and exhaust pipes, and the vehicle intake and exhaust are directly connected to the outside atmosphere, ensuring that there is no exchange between the gas inside the closed chamber and the outside gas during the vehicle's driving, and all the particulate matter generated by the vehicle is in the running loss closed chamber. It should be noted that in this application, the running loss closed chamber is referred to as the closed chamber.

[0051] (7) Aerodynamic particle size spectrometer (APS) is a high-performance, multi-purpose particle measuring instrument, which is mainly used to measure the aerodynamic size of aerosol particles and provide the distribution of aerosol number concentration, surface area concentration, volume concentration and mass concentration with particle size. The dynamic particle size of the particle is calculated by measuring the flight time of the particle passing through two close-range laser beams in the accelerated airflow. This measurement method avoids the influence of the refractive index and Mie scattering instrument, and improves the accuracy and stability of the measurement.

[0052] Example 1

[0053] Figure 1 A method for calculating non-exhaust particulate matter based on an operating loss closed chamber is provided in an embodiment of the present invention, and specifically includes:

[0054] S1. Construct a vehicle operation model in a closed room; set up a collection tube in the vehicle operation model; and perform CFD simulation on the changes in the non-exhaust particle flow field when the vehicle is running in the closed room.

[0055] In this application, a vehicle operation model was first constructed for experimentation, and then a CFD simulation was performed using a computer:

[0056] 1. Vehicle operation model

[0057] The whole vehicle operation model and the actual vehicle operation model are built in a 1:1 ratio. The vehicle is fixed on a chassis dynamometer to simulate the vehicle's operating state at different speeds, ensuring the accuracy and reliability of the experimental conclusions.

[0058] In a specific embodiment, the vehicle is located in a closed room, a chassis dynamometer 1 is arranged under the vehicle, a front fan 2 is arranged at the front of the vehicle to simulate the wind speed state when the vehicle is running, and a sampling port 3 is arranged on the bottom of the closed room. The particle testing equipment 4 collects the concentration of particulate matter in the air in the vehicle in real time and accurately through the sampling port 3; there is also a driver assistant 5 to assist the driver in management, maintenance, communication and coordination; an air bag 6 is arranged above the closed room for pressure compensation; a chiller 7 is arranged in the closed room for heat exchange to reduce the indoor ambient temperature; a plate heat exchanger 8 and a copper grille 9 are used in combination with each other to cooperate to reduce the indoor ambient temperature, which significantly improves the heat transfer speed and efficiency; there is also a circulating fan 10 that makes the temperature uniform; there are also an engine intake duct 11 and an engine exhaust duct 12, a fresh air system 13 is used to supply air to the engine intake duct 11, and a tail exhaust fan 14 is used to exhaust the exhaust gas in the engine exhaust duct 12. In addition, the closed room is also provided with a personnel entrance and a vehicle entrance. Figure 2 not shown in; Figure 2 It is only a schematic diagram of the closed room structure. The chiller 7, the plate heat exchanger 8, the fresh air system 13 and the tail exhaust fan 14 are all arranged in the closed room.

[0059] A collection tube is set at a random position in the closed room. The collection tube is used to collect the sampling flow rate of the particulate matter at that point, and then the mass flow rate is calculated; the mass flow rate indicates the mass of particulate matter passing through a given cross-sectional area per unit time, and is an important physical parameter in industrial production.

[0060] The related design of the closed chamber is prior art and will not be described in detail in this application.

[0061] It should be noted that this application focuses on PM2.5 and PM 10 The concentration of PM 2.5 and PM 10 Take this as an example to illustrate.

[0062] 2. CFD simulation

[0063] The calculation domain was constructed according to the actual size of the closed chamber for CFD simulation to simulate the flow field and particle change characteristics during the closed chamber experiment, ensuring the accuracy and reliability of the simulation process.

[0064] It should be noted that the following content is illustrated by using ANSYS Fluent software to build a simulation model, but this application does not make any specific limitations on this. COMSOL Multiphysics, ANSYS Flo and other software can also be used to implement the technical solution of this application.

[0065] For example, see Figure 3 , the following processing can be performed during simulation:

[0066] The ground fans and ceiling circulation fans that may disturb the closed indoor environment flow field are taken into consideration, and the sampling tubes are drawn according to the actual experimental design. The car body model of a certain brand is used as the research object. Without affecting the calculation accuracy, the three-dimensional model is simplified, and the doors and windows of the closed room are ignored. For the vehicle, the accessories such as door handles, wipers and rearview mirrors are ignored, and the chassis is flattened.

[0067] When simulating the flow field in a closed room, the entire calculation domain needs to be numerically discretized. The calculation domain is meshed using a hybrid grid of tetrahedrons and triangular prisms. To meet the requirements of the wall function, a triangular prism grid parallel to the body surface is stretched out to simulate the boundary layer. At the same time, the grid is encrypted using a density box in the calculation sensitive area (tires, body near wall flow area, and rear area) to achieve local mesh refinement to improve the calculation accuracy. No-slip wall boundaries are used for other walls in the calculation domain.

[0068] The following is a description of the model used in the analysis:

[0069] Under normal conditions, a car is driving in an open space and is a low Mach number vehicle. The flow field around the car is considered to be an incompressible fluid. Due to its complex shape, the airflow separation around the car body is easy to occur. The external flow field of the car is a viscous, incompressible flow with typical three-dimensional separation flow characteristics, so the external flow field of the car is treated as turbulent. The Realizable k-ε turbulence model takes into account the effects of rotation and curvature on the flow, and can effectively simulate rotating shear flow, free flow containing jets, and boundary layer flow, etc. Therefore, this application adopts the Realizable k-ε turbulence model.

[0070] The simulation of non-exhaust particulate matter in a closed room involves flow field and particulate matter, which is a multiphase flow problem. In this study, the fluid is regarded as a continuous medium and the Euler method is used for calculation; the particulate matter is regarded as a discrete phase and the Lagrange method is used for calculation. Assuming that the non-exhaust particulate matter is a small sphere of different particle sizes and ignoring the interaction between particles, the particles are mainly affected by gravity, airflow drag and Saffman lift in the flow field. On the one hand, they move along a certain orbit. On the other hand, due to the influence of turbulent pulsation, the particles will also diffuse around the average orbit and produce irregular motion. Therefore, the random turbulent orbit model is selected to simulate the multiphase motion of the flow field and particulate matter.

[0071] In the simulation, the formula describing the force on the particles, that is, the equilibrium force equation of the particles in the Cartesian coordinate system can be written as:

[0072] ,

[0073] ,

[0074] ,

[0075] in, is the fluid drag; is the air speed; is the particle velocity; is the vehicle speed; is the fluid dynamic viscosity coefficient, ; is the particle density, which is ; is the air density, which is 1.225 kg·m -3 ; The particle diameter is set to 2.5 , 10 ; is the Reynolds number; is the fluid drag correction factor; are other external forces acting on the particles.

[0076] For the above formula, the Reynolds number is a dimensionless number that can be used to characterize fluid flow conditions. It needs to be calculated through a full-vehicle running model experiment in order to simulate the particle motion trajectory and particle distribution through computer simulation.

[0077] The entire experimental operation took a long time. The mapping calculation was extremely computationally intensive and time-consuming during the simulation process. Therefore, when analyzing the diffusion characteristics of particulate matter, only six representative vehicle speeds were selected as the investigation objects, namely, 20 km·h-1 、40 km·h -1 、60 km·h -1 、80 km·h -1 、100 km·h -1 and 120 km·h -1 , and the Reynolds number and turbulence intensity at different vehicle speeds are calculated, where the turbulence intensity is the ratio of the root mean square of the speed fluctuation to the average speed.

[0078] In a closed room, there are circulating fans, wind from the front fans, and other air flow disturbances, which will form turbulence. Turbulence intensity describes the degree of wind speed change over time and space, reflects the relative intensity of pulsating wind speed, and is the most important characteristic quantity describing the characteristics of atmospheric turbulence motion. The calculation of turbulence intensity can improve the accuracy of computer simulation and reduce errors and uncertainties.

[0079] In a specific embodiment, the calculated values ​​of Reynolds number and turbulence intensity at different vehicle speeds are shown in Table 1.

[0080] Table 1 Reynolds number and turbulence intensity at different vehicle speeds

[0081]

[0082] The flow field is simulated according to the above Reynolds number to obtain more accurate particle trajectory and particle distribution, making the simulation results more accurate.

[0083] Particulate matter emissions from brake wear and tire wear are simulated in the following way:

[0084] The particle emission point of the brake pad is generated by the friction between the brake pad and the brake disc, so the wear point is where the brake pad and the brake disc contact, and a particle injection port is set at this point.

[0085] The point where tire wear particle emissions are generated is: the point where the tire contacts the drum surface. Specifically, for the front and rear wheels, a particle injection port is set on the wheel hub of the front wheel of the vehicle, and a particle injection port is set behind the contact mark between the rear wheel tire and the ground.

[0086] The emission factors of each particle emission point are obtained according to the bench test, and the particle phase injection ports of the brake pads and the front and rear wheels are set in the same way. See Table 2. The emission factor is represented by E, which represents the average value of the particle emission in mg / km. is the vehicle speed in km / s, then the mass flow rate Q = E× , the unit of Q is mg / s. Among them, brake wear corresponds to brake pads, and tire wear corresponds to tires.

[0087] Table 2 Brake wear and tire wear emission factor settings

[0088]

[0089] In summary, based on the above settings, a CFD simulation of the changes in the non-exhaust particle flow field when the vehicle is running in a closed room was completed.

[0090] The rationality of the design related to CFD simulation is explained as follows:

[0091] (1) The distribution characteristics of the flow field in a closed chamber have a direct impact on the distribution characteristics of non-exhaust particulate matter emitted by vehicles. The distribution characteristics of the flow field in the cabin under different working conditions are simulated and analyzed.

[0092] Since the wind speed of the front fan placed in front of the vehicle is controlled to change with the vehicle speed, the wind speed in the closed room will change greatly with the change of different vehicle speeds in the experiment. Figure 4 , Figure 5 and Figure 6 Taking the indoor wind speed distribution diagram under the working conditions of 40km / h, 80km / h and 120km / h as an example, the indoor wind speed distribution is uneven, and the distribution pattern of the wind speed change in the cabin under different vehicle speed conditions is still basically the same. In the X-axis direction, affected by the front fan, the wind speed on the front side of the vehicle is significantly higher, and the wind speed on the rear side is significantly reduced. In the Y-axis direction, the wind speed in the lower part of the room is significantly higher than that in the upper part, and due to the disturbance of the surrounding airflow caused by the rotation of the wheels, the wind speed around the wheels has a significant increase. The wind speed in the Z-axis direction is affected by the vehicle shape and is symmetrically distributed on the left and right sides of the vehicle body. The simulation results of the wind speed distribution characteristics in the closed room can be explained by actual experimental conditions, which proves the rationality of the relevant settings of the CFD simulation of this application.

[0093] (2) The movement trajectory of particles in a closed room is mainly dominated by the flow field. The uneven wind speed distribution in the closed room will have a certain impact on the distribution characteristics of particles.

[0094] The discrete phase model is used to simulate and analyze the distribution characteristics of particulate matter in a closed room. The simulation results are shown in Figure 7 , Figure 8 and Fig. 9. The mass concentration of particles is unevenly distributed in the closed room, and is mainly distributed in a flocculent state. Combined with the above analysis of the flow field, it can be seen that the distribution of particles is greatly affected by the wind speed distribution. In the X-axis direction, due to the high wind speed in front of the vehicle, it is conducive to the diffusion of particles. Therefore, the concentration of particles in front of the front of the vehicle is relatively low at different vehicle speeds, while the wind speed in the rear of the cabin is relatively low, and particles are more likely to accumulate here. For conditions with low vehicle speeds, the wind speed of the front fan is also relatively low, so the particles gather at the rear of the vehicle and the rear of the cabin. As the vehicle speed and the wind speed of the fan increase, the particles are entrained by the airflow and begin to circulate along the wall in the cabin, and the distribution of particle concentration in the cabin gradually tends to be uniform. Consistent with the flow field distribution characteristics, the particle concentration remains basically symmetrical in the Z-axis direction.

[0095] (3) Particulate matter at a speed of 120 km / h -1 The motion trajectory at Fig.10 and Fig.11 After the particles are ejected from the rear of the tire contact surface and the tire gap, most of the particles are dispersed to the side and rear after being blocked by the bottom of the wheel and the vehicle covering under the action of the flow field.

[0096] See also Fig.12 , due to PM 2.5 and PM 10 The particle size is small, the gravity is small, and it is significantly affected by the turbulence of the flow field during movement, and has good turbulence following performance. Therefore, the particles are mainly scattered to the side and rear after being blocked by the cover under the airflow, and enter the wheel cover gap with the rolling of the tire and the shape of the cover.

[0097] At the same time, part of the particles generated by the front wheel are mixed into the gap between the wheel cover and the tire at the rear wheel, so more particles are gathered in the gap between the rear wheel and the wheel cover than in the front wheel. 2.5 and PM 10 The spatial distribution difference is not significant, which may be due to the small difference in the particle size of the target particles and the similar forces during the diffusion process.

[0098] Therefore, based on the above analysis, the CFD simulation model of the present application has high accuracy and precision.

[0099] S2. According to the CFD simulation, the particle concentration distribution in the closed room at different preset vehicle speeds is obtained, and the mass flow rate of the particle source and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model are calculated respectively; the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds is calculated to obtain the particle collection rate; the preset vehicle speed is used as the independent variable and the particle collection rate is used as the dependent variable to obtain the fitting formula.

[0100] When the CFD simulated flow field is in a stable state, the software automatically performs iterative calculations to obtain the particle concentration distribution, and then calculates the first collected particle mass flow rate based on the particle concentration distribution. The first collected particle mass flow rate is obtained by multiplying the particle concentration at the collection tube position in the corresponding vehicle operation model by the sampling flow rate; the sampling flow rate is a parameter of APS, and APS can measure the concentration of particulate matter in a closed room every second.

[0101] As for the mass flow rate of the particulate matter source, it is calculated based on the above parameter settings and the preset parameters in Table 2. 10 For example, the mass flow rate of the particulate matter source = preset vehicle speed × (4.39×2+0.37×2+2.51×2+0.29×2), which is the sum of the mass flow rates at each particulate matter emission point.

[0102] Particle collection rate As shown below:

[0103] ,

[0104] in, is the first collected particle mass flow rate, is the mass flow rate of the particle source,

[0105] Set different preset speeds, such as when the preset speed is 20km·h -1 , 40km·h -1 、60km·h -1 , 80km·h -1 , 100km·h -1 and 120 km·h -1 When the particle concentration data at the sampling tube is obtained, the calculation can be obtained The values ​​corresponding to the preset speeds are 0.003, 0.003, 0.004, 0.0055, 0.0067 and 0.007. Obviously, the particle collection rate decreases slightly with the increase of the preset vehicle speed.

[0106] Based on the particle collection rate obtained at each preset speed, a curve is drawn, see Fig.13 , and fit the calculation formula:

[0107] ,

[0108] in, The preset speed.

[0109] Here, the particle collection rate is the ratio of the particle mass flow rate at a certain point in the closed room and the overall particle flow rate in the closed room obtained based on the simulation, which can more accurately reflect the actual particle distribution. Based on this ratio, combined with the experimental conditions of the actual point of the collection tube, the particle emissions of the entire vehicle can be derived.

[0110] S3. Set the vehicle in the whole vehicle operation model to run at an arbitrary speed, calculate the second collected particulate matter mass flow rate of the collection pipe at each moment during the vehicle operation time; and obtain the non-exhaust particulate matter emissions based on the second collected particulate matter mass flow rate, the fitting formula, the travel speed and the vehicle operation time.

[0111] The non-exhaust particulate matter emission mass flow rate of the vehicle in the whole vehicle operation model is the ratio of the second collected particulate matter mass flow rate and the particulate matter collection rate. The non-exhaust particulate matter emission mass flow rate and the fitting formula are integrated corresponding to the vehicle operation time to obtain the non-exhaust particulate matter emission amount.

[0112] Specifically, the second collected particle mass flow rate can be calculated using the following formula:

[0113] ,

[0114] Among them, F aps Refers to the sampling flow of APS, the unit is m 3 / s;C aps is the sampling concentration of the aerodynamic particle size spectrometer (mg / m 3 Here, the sampling flow rate of the APS may correspond to the calculation of the first collected particle mass flow rate. The measurement of the particle sampling concentration may also be completed using other equipment, and this application does not make specific limitations.

[0115] Based on the above other parameter settings, it can be concluded that the vehicle non-exhaust particulate matter emission mass flow rate in the vehicle operation model is:

[0116] .

[0117] In the above formula, v is substituted into the running speed, and the running speed and APS sampling concentration are quantities that change over time. aps Substituting into the above formula and integrating the time, the total non-exhaust particulate matter emissions of the vehicle in the entire driving condition can be calculated. The operating time can be obtained from the chassis dynamometer.

[0118] Example 2

[0119] Based on the relevant parameter settings of Example 1, in a specific embodiment, the process of conducting an experiment on the vehicle operation model is as follows:

[0120] Step 1: Clean the enclosed room to reduce the content of particulate matter in the enclosed room;

[0121] Step 2: Fix the vehicle on the base dynamometer and set the drag coefficient according to the requirements of the National VI standard;

[0122] Step 3: The engine air intake pipe and the engine exhaust pipe are directly connected to the outside of the sealed room to ensure the sealing of the sealed room;

[0123] Step 4: Set up APS and start it;

[0124] Step 5: Start the closed room purge function to reduce the background emission of the closed room; the purge function is to replace the air in the closed room; background emission refers to the particulate matter in the air before the experiment;

[0125] Step 6: Carry out 8 consecutive cycles of WLTC driving, with the chassis dynamometer recording the vehicle speed.

[0126] Among them, the APS sampling flow rate is fixed at 5L / min, and the APS can record the mass concentration of particulate matter in a closed room every second in real time. WLTC is the abbreviation of the English name of the World Light Vehicle Test Specification; the National VI standard is the standard for pollutant emissions from Chinese motor vehicles.

[0127] In a specific embodiment, eight WLTC cycles take a total of 14,400 seconds, and the particle concentration data and velocity data collected by the APS per second are substituted into the following formula:

[0128] ,

[0129] Integrating the time, the total emission result for the last 8 cycles is 885.78 mg. Each WLTC mileage is 23.3 km, and the total mileage of 8 cycles is 186.4 km, so the particulate matter emission per unit mileage is 885.78 / 186.4 mg / km=4.75 mg / km.

[0130] Example 3

[0131] Based on the content of Example 1, the present application provides a non-exhaust particulate matter calculation system based on an operation loss closed chamber, including:

[0132] Construction module: construct a vehicle operation model in a closed room; set up a collection tube in the vehicle operation model; perform CFD simulation on the changes in the non-exhaust particulate flow field when the vehicle is running in the closed room;

[0133] Simulation module: obtain the particle concentration distribution in the closed room at different preset vehicle speeds based on CFD simulation, calculate the particle source mass flow rate and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model respectively; calculate the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds to obtain the particle collection rate; use the preset vehicle speed as the independent variable and the particle collection rate as the dependent variable to fit and obtain the fitting formula;

[0134] Calculation module: Set the vehicle in the whole vehicle operation model to run at an arbitrary speed, calculate the second collected particulate mass flow rate of the collection tube at each moment during the vehicle operation time; obtain the non-exhaust particulate emission according to the second collected particulate mass flow rate, fitting formula, travel speed and vehicle operation time.

[0135] For other contents, please refer to Example 1 and will not be described in detail here.

[0136] It should be noted that the division of the above-mentioned functional modules is only used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0137] Example 4

[0138] The present application provides an electronic device, the electronic device includes a processor and a memory for storing instructions executable by the processor; when the processor is configured to execute the instructions, the electronic device implements the method in Embodiment 1. The electronic device may be a tablet computer, a handheld computer, a personal computer PC, or other electronic device. The electronic device may directly display the calibration result, which is convenient for the operator to directly view.

[0139] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When the use is implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.) mode) to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more available media integrated. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state hard disk Solid State Disk (SSD)), etc.

[0140] In the description of the present invention, it is to be understood that the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0141] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0142] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating non-exhaust particulate matter in a closed room based on operating losses, characterized in that: The following steps are involved: Constructing a vehicle operation model in a closed room; setting a collection pipe in the vehicle operation model; performing CFD simulation on the change of non-exhaust particulate flow field when the vehicle is running in the closed room; The particle concentration distribution in the closed room at different preset vehicle speeds is obtained according to CFD simulation, and the mass flow rate of the particle source and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model are calculated respectively; the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds is calculated to obtain the particle collection rate; the preset vehicle speed is used as the independent variable and the particle collection rate is used as the dependent variable to obtain the fitting formula; The vehicle in the vehicle operation model is set to run at an arbitrary speed, and the second collected particulate matter mass flow rate of the collection pipe at each moment during the vehicle operation time is calculated; the non-exhaust particulate matter emission is obtained according to the second collected particulate matter mass flow rate, the fitting formula, the travel speed and the vehicle operation time; wherein, The vehicle operation model is constructed in a 1:1 ratio according to the actual vehicle operation model; the CFD simulation constructs the calculation domain according to the actual size of the closed room; the calculation domain is numerically discretized, and the calculation domain is meshed using a hybrid mesh of tetrahedrons and triangular prisms, parallel triangular prism meshes are stretched on the surface of the vehicle body to simulate the boundary layer, and the density box is used to encrypt the mesh when calculating sensitive areas; In the CFD simulation, particle injection ports are set on the wheel hub of the front wheel of the vehicle, and behind the ground contact position of the rear wheel tire; particle injection ports are set at the contact point between the brake pad and the brake disc; the external flow field of the vehicle is treated as turbulent, and the random turbulence trajectory model is used to simulate the closed indoor flow field and the multiphase motion of particles; The Reynolds number is obtained through the vehicle running model experiment, and the Reynolds number is applied to the CFD simulation; wherein the Reynolds number is calculated based on different vehicle driving speeds, and the vehicle driving speed includes 20 km·h -1 、40 km·h -1 、60km·h -1 、80 km·h -1 、100 km·h -1 and 120 km·h -1 ; The non-exhaust particulate matter emission amount is obtained according to the second collected particulate matter mass flow rate, the fitting formula, the travel speed and the vehicle running time, further comprising: the non-exhaust particulate matter emission mass flow rate of the vehicle in the whole vehicle running model is the ratio of the second collected particulate matter mass flow rate and the particulate matter collection rate, and the non-exhaust particulate matter emission mass flow rate and the fitting formula are integrated corresponding to the vehicle running time to obtain the non-exhaust particulate matter emission amount; Non-exhaust particulate matter emission mass flow rate Calculated by the following formula: ， ， in, is the fitting formula, v is the travel speed, is the second collected particle mass flow rate, F aps is the sampling flow rate of APS, C aps is the sampling concentration of the aerodynamic particle size spectrometer; v and Caps are quantities that change over time. The non-exhaust particulate matter emissions are obtained by integrating over the operating time.

2. The method for calculating non-exhaust particulate matter in a closed chamber based on operating loss according to claim 1 is characterized in that: The Realizable k-ε turbulence model is used in CFD simulation to simulate the external flow field of the vehicle.

3. The method for calculating non-exhaust particulate matter in a closed chamber based on operating loss according to claim 1, characterized in that: The particle source mass flow rate is the sum of the mass flow rates at the front wheels, rear wheels and brake pads of the vehicle; the first collected particle mass flow rate is the product of the particle concentration at the collection pipe position in the corresponding vehicle operation model and the collection flow of the APS.

4. The method for calculating non-exhaust particulate matter in a closed chamber based on operating loss according to claim 3 is characterized in that: The APS collects the sampling concentration at the sampling tube in the whole vehicle operation model, and the product of the sampling concentration and the collection flow of the APS is the second collected particulate matter mass flow rate.

5. Based on the operation loss closed chamber non-exhaust particulate matter calculation system, it is characterized by: The method for calculating non-exhaust particulate matter in a closed chamber based on operating loss according to any one of claims 1 to 4 comprises: Construction module: constructing a vehicle operation model in a closed room; setting a collection pipe in the vehicle operation model; performing CFD simulation on the change of non-exhaust particulate flow field when the vehicle is running in the closed room; Simulation module: obtain the particle concentration distribution in the closed room at different preset vehicle speeds based on CFD simulation, calculate the particle source mass flow rate and the first collected particle mass flow rate at the collection tube position in the corresponding vehicle operation model respectively; calculate the ratio of the first collected particle mass flow rate and the particle source mass flow rate at different preset vehicle speeds to obtain the particle collection rate; use the preset vehicle speed as the independent variable and the particle collection rate as the dependent variable to fit and obtain the fitting formula; Calculation module: Set the vehicle in the whole vehicle operation model to run at an arbitrary speed, calculate the second collected particulate mass flow rate of the collection tube at each moment during the vehicle operation time; obtain the non-exhaust particulate emission according to the second collected particulate mass flow rate, fitting formula, travel speed and vehicle operation time.

6. An electronic device, characterized in that: include: A memory, a processor and a computer program; wherein the computer program is stored in the memory and is configured to be executed by the processor to implement the method for calculating non-exhaust particulate matter in a closed chamber based on operating losses as described in any one of claims 1 to 4.

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