Detection method and system for simulating vertically arranged pavement remote sensing equipment, and medium

Abstract

The invention discloses a detection method and system for simulating vertically-arranged pavement remote sensing equipment and a medium, and the detection method comprises the steps: sequentially dividing three continuous regions A, B and C, and carrying out the relative rest of an automobile in the region B, and carrying out the physical modeling; drawing a dynamic grid for performing decoupling analysis on the influence of the entrance speed and the vehicle speed; carrying out numerical simulation, and simulating a turbulence model based on a large eddy current simulation method so as to obtain transient data of pollutants in the tail gas; a light source is used for emitting ultraviolet light and infrared light beams and receiving light penetrating through waste gas, so that a contour map of the integral molar concentration of pollutants and the diffusion condition of the pollutants is calculated. According to the invention, through simulation of the running vehicle, massive transient data processing of pollutants in vehicle exhaust is realized. And the pollutant concentration of the vehicle under the working condition is obtained from transient data, so that a pollutant diffusion rule is summarized, and the precision of remote sensing equipment in actual production is improved.

Description

Technical Field

[0001] The invention belongs to the field of data measurement, and in particular relates to a method, system and medium for simulating vertically arranged road surface remote sensing equipment detection. Background Art

[0002] Road surface remote sensing (RS) is a fast, non-intrusive and economical monitoring method for diagnosing pollutant emissions during actual driving. This RS method has received widespread attention in recent years and consists of 2 arrangements (horizontal and vertical laser beams). By comparing the light attenuation of the infrared beam, the concentrations of hydrocarbons (HC), carbon monoxide (CO) and carbon dioxide (CO2) in the plume can be measured. Nitrogen oxides (NO) can also be measured by ultraviolet beams. When a vehicle passes the measurement location, the concentration ratio of pollutants (such as CO, HC and NO) to CO2 in the exhaust plume can be measured within 0.5s. This horizontal beam may be affected by dust suspension and vehicle splashes because it is usually placed about 25.4cm above the ground. The vertical arrangement can overcome the shortcomings of the horizontal arrangement because its measurement equipment is placed at a higher position to avoid the influence of traffic and pedestrians near the ground. In addition, the vertical arrangement can also use the whisk scanning method to capture downward images of passing vehicles and their exhaust plumes to provide information about emission dispersion, which is very promising in remote sensing equipment.

[0003] For enforcement purposes, the identification of high-emission vehicles must be highly accurate, which is a major challenge for RS equipment. Computational fluid dynamics (CFD) is an effective tool to improve RS accuracy, as it can visually display detailed information about the transport of pollutant emissions in the turbulent flow field behind the vehicle.

[0004] Studies have shown that exhaust gas will diffuse immediately when it is released into the air, and the concentration will decrease due to dilution. For a given smoke plume, using CO2 as the reference gas, Q CO , Q HC , Q NO It represents the ratio of CO, HC, NO and CO2 concentration, i.e. Q CO =CO / CO2, Q HC =HC / CO2, Q NO = NO / CO2. Studies have shown that for a particular motor vehicle exhaust plume, Q CO , Q HC , Q NOIn the initial stage of diffusion in the tailpipe and air (lasting about 1s), it remains unchanged, so the volume concentration of each pollutant in the tail gas can be calculated by inversion. Assuming the engine air-fuel ratio is m, there is no excess air, the proportion of nitrogen and oxygen in the engine intake is 79% and 21% respectively, and assuming that the fuel carbon-hydrogen ratio is fixed. Under normal circumstances, the chemical composition of diesel can be regarded as C12H23, and the carbon-hydrogen ratio is very close to 1:2. Assuming that diesel is measured in CH2 equivalent, the combustion equation is:

[0005]

[0006] According to the atomic conservation in the combustion equation, and Q CO , Q HC , Q NO The dry volume concentration of each component can be derived from the definition of simultaneous equations as shown below.

[0007]

[0008] In the formula, C CO2 , C CO , C HC , C NO are the volume concentrations of CO2, CO, HC and NO in the exhaust gas respectively.

[0009] The existing methods are only applicable to motor vehicle operating conditions. In actual vehicle driving, the air-fuel ratio changes with different driving conditions, the engine combustion efficiency changes, and the residual oxygen concentration in the exhaust gas also changes. The combustion equation that assumes there is no excess oxygen is less applicable.

[0010] The method of the present invention can directly obtain the diffusion data of the exhaust gas behind a diesel vehicle during actual driving by combining dynamic grid technology with numerical simulation, and then directly calculate the integral molar concentrations of CO2, CO, HC, and NO in the vehicle exhaust gas through a specific numerical processing method. It has wide applicability and conforms to production practice. Summary of the invention

[0011] The purpose of the present invention is to overcome the above problems existing in the prior art and to provide a method, system and medium for simulating vertically arranged road surface remote sensing equipment detection.

[0012] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0013] A method for detecting a road surface remote sensing device simulating a vertical arrangement, comprising:

[0014] Three continuous areas A, B, and C are divided in sequence. A car is placed relatively still in area B for physical modeling, and area B moves forward according to the speed of the vehicle. An AB interface is set between area A and area B, and a BC interface is set between area B and area C.

[0015] Draw dynamic mesh based on AB and BC interfaces to decouple the impact of inlet velocity and vehicle velocity;

[0016] The Euler method of computational fluid software is used for numerical simulation, and the turbulence model is simulated based on the large eddy simulation method to obtain the transient data of pollutants in the exhaust gas;

[0017] The light source emits ultraviolet and infrared beams and receives the light that passes through the exhaust gas, thereby calculating the integrated molar concentration of the pollutants and the contour map of the pollutant diffusion.

[0018] Furthermore, the large eddy simulation method uses a wall-adaptive local eddy viscosity model to capture transient turbulence.

[0019] Furthermore, the pressure-implicit operator partitioning method is used to solve the pressure-velocity coupling.

[0020] Furthermore, area A and area C are located in front of and behind area B, respectively. As area B moves forward, the grid of area A closest to area B gradually disappears, and the grid of area C appears.

[0021] Furthermore, the left and right surfaces of the A region, the B region, and the C region are coupled by setting a periodic boundary.

[0022] Furthermore, the Euler method of computational fluid software was used to perform numerical simulations including the conservation equations of mass, momentum, energy and species. The absolute standard of the four conservation equations was 10 -12 , the formulas are as follows:

[0023]

[0024] Furthermore, the integral molar concentration of pollutants and the contour map formula of pollutant diffusion are calculated as follows:

[0025]

[0026] Furthermore, calculating the integral molar concentration of the pollutant and the contour map of the pollutant diffusion includes the following steps:

[0027] Extract the molar concentration and grid height of the grid to calculate the integral;

[0028] Multiply the molar concentration and the grid height in the same grid to get a product;

[0029] Sum these products along each vertical line;

[0030] The integrated values ​​are averaged to eliminate the influence of time fluctuations;

[0031] Generate a contour plot in the xz plane.

[0032] The present invention also provides a road surface remote sensing equipment detection system simulating vertical arrangement, comprising:

[0033] The physical modeling module is used to sequentially divide three continuous areas, A, B, and C. A car is placed in the B area to be relatively still and perform physical modeling. The B area moves forward according to the speed of the vehicle. An AB interface is set between the A area and the B area, and a BC interface is set between the B area and the C area.

[0034] Mesh drawing module, which draws dynamic mesh based on AB and BC interfaces, and is used to decouple the influence of inlet speed and vehicle speed;

[0035] Numerical simulation module, used to perform numerical simulation using the Euler method of computational fluid software, and simulate turbulence models based on large eddy simulation methods, so as to obtain transient data of pollutants in exhaust gas;

[0036] The pollution calculation module is used to use a light source to emit ultraviolet and infrared beams and receive the light that passes through the exhaust gas, so as to calculate the integral molar concentration of the pollutants and the contour map of the pollutant diffusion.

[0037] The present invention also provides a computer storage medium on which a computer program is stored, and the computer program implements the above detection method when executed.

[0038] The beneficial effects of the present invention are:

[0039] 1. The present invention realizes the processing of massive transient data of pollutants in vehicle exhaust by simulating the running vehicle. The concentration of pollutants in the vehicle under the working condition is obtained from the transient data, so as to summarize the diffusion law of pollutants and further help improve the accuracy of remote sensing equipment in actual production.

[0040] 2. The present invention uses linear regression analysis to estimate the emission concentration of various pollutants from gasoline and diesel vehicles.

[0041] 3. The present invention uses the carbon balance method to study the emission factors of the remote sensing method.

[0042] 4. The present invention uses the weighted partial least squares method to correct the nitrogen oxide concentration inversion algorithm.

[0043] 5. The present invention modifies the engine combustion equation by considering the influence of residual oxygen on the combustion equation, and after the modification, the emission factor is estimated using the carbon balance method. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0045] Figure 1 is a flow chart of the method of the present invention;

[0046] Figure 2 It is a schematic diagram of the area division of the dynamic grid in the present invention;

[0047] Figure 3 Schematic diagram of the distribution of vertical lines in the vehicle wake area in the present invention;

[0048] Figure 4 It is the contour map of the integrated molar concentration of CO2 at a vehicle speed of 30 km / h (a) and 90 km / h (b) in the present invention;

[0049] Figure 5 It is a system structure block diagram of the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] like Figure 1 A method for detecting a road surface remote sensing device simulating a vertical arrangement is shown, comprising:

[0052] Three continuous areas A, B, and C are divided in sequence. A car is placed in area B to remain relatively still and physical modeling is performed. Area B moves forward according to the speed of the vehicle. An AB interface is set between area A and area B, and a BC interface is set between area B and area C.

[0053] Draw dynamic mesh based on AB and BC interfaces to decouple the impact of inlet velocity and vehicle velocity;

[0054] The Euler method of computational fluid software is used for numerical simulation, and the turbulence model is simulated based on the large eddy simulation method to obtain the transient data of pollutants in the exhaust gas;

[0055] The light source emits ultraviolet and infrared beams and receives the light that passes through the exhaust gas, thereby calculating the integrated molar concentration of the pollutants and the contour map of the pollutant diffusion.

[0056] The present invention takes a Toyota Hiace car equipped with a 3.0L turbocharged diesel engine as an example. The total length, width and height of the car are 4695mm, 1695mm and 1980mm respectively. The exhaust tail pipe is located on the left side of the vehicle and has a diameter of 104mm. Figure 2 As shown in the figure, the dynamic grid is divided into three areas: A, B, and C. The vehicle is placed in area B and is relatively stationary, and area B moves forward according to the vehicle speed. Area A and area C are located in front of and behind area B, respectively. The initial lengths of area A and area C are 200m and 2m, respectively. As area B moves forward, the grid of area A, which is closest to area B, gradually disappears, and the grid of area C appears.

[0057] Since the time scale considered in this study is relatively short, the chemical reaction source terms in the energy equation and the species equation are ignored. In addition to nitrogen (N2) and oxygen (O2) in the air, this invention only considers CO2, NO and water vapor (H2O) because the CO and HC emissions of diesel vehicles are relatively low. The large eddy simulation (LES) uses the wall adaptive local eddy viscosity (WALE) model to capture transient turbulence. The pressure-velocity coupling is solved using the pressure-implicit operator partitioning method (PISO). The Euler method of the computational fluid software is used for numerical simulation, including the conservation equations of mass, momentum, energy and species. The absolute standard of the four conservation equations is 10 -12 , the formulas are as follows:

[0058]

[0059]

[0060] Table 1 shows the boundary conditions for each face in regions A, B, and C. The main advantage of dynamic meshing is that the effects of inlet velocity and vehicle velocity can be decoupled for analysis. In addition, an interface boundary is required to establish the relationship between different regions. For example, the AB interface is set by coupling the rear of region A and the front of region B because these two faces are adjacent. Similar to static meshing, the left and right faces of regions A, B, and C are also coupled by setting periodic boundaries accordingly. By combining the above dynamic meshing technology with the large eddy simulation method, the transient simulation results of pollutants in vehicle exhaust can be obtained.

[0061] Table 1 Boundary conditions of dynamic grid

[0062]

[0063] By applying an original and specific integration method to the above results, we can obtain the integral molar concentration of pollutants and the contour map of pollutant diffusion. The integration principle is as follows: First, the light source emits ultraviolet and infrared beams, which are absorbed by CO2, CO, NO in the exhaust gas. x and HC absorption. Then, the detection device receives the light that has passed through the exhaust gas. According to Lambert-Beer's law, the attenuation of light intensity determines the integral of the emission concentration along the light path. I is the light intensity, dI is the light intensity weakened by absorption by gas molecules. C(y) is the local molar concentration, and dy is the slight change in vertical distance. I1 and I2 are the intensities of the input and output light, respectively. The integral of the molar concentration of pollutants in the vertical direction along the light path can be calculated.

[0064] The formula for calculating the integral molar concentration of pollutants and the contour map of pollutant diffusion is as follows:

[0065]

[0066] Figure 3 The uniform distribution of vertical lines in the vehicle wake area is shown. The integration process is divided into the following five steps:

[0067] Extract the molar concentration and grid height of the grid to calculate the integral;

[0068] Multiply the molar concentration and the grid height in the same grid to get a product;

[0069] Sum these products along each vertical line;

[0070] The integrated value is averaged in the range of 3.0-8.0s to eliminate the influence of time fluctuation;

[0071] Generate a contour plot in the xz plane.

[0072] like Figure 4 As shown, it is a contour map of the integrated molar concentration of CO2 in vehicle exhaust gas when the vehicle speed is 30km / h and 90km / h.

[0073] The second aspect of the present invention also provides a road surface remote sensing equipment detection system simulating vertical arrangement, comprising:

[0074] The physical modeling module is used to sequentially divide three continuous areas, A, B, and C. A car is placed in the B area to be relatively still and perform physical modeling. The B area moves forward according to the speed of the vehicle. An AB interface is set between the A area and the B area, and a BC interface is set between the B area and the C area.

[0075] Mesh drawing module, which draws dynamic mesh based on AB and BC interfaces, and is used to decouple the effects of inlet speed and vehicle speed;

[0076] Numerical simulation module, used to perform numerical simulation using the Euler method of computational fluid software, and simulate turbulence models based on large eddy simulation methods, so as to obtain transient data of pollutants in exhaust gas;

[0077] The pollution calculation module is used to use a light source to emit ultraviolet and infrared beams and receive the light that passes through the exhaust gas, so as to calculate the integral molar concentration of the pollutants and the contour map of the pollutant diffusion.

[0078] The third aspect of the present invention also provides a computer storage medium on which a computer program is stored, and the computer program implements the above method when executed. The storage medium may include: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program codes.

[0079] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for simulating vertically arranged road surface remote sensing equipment detection, characterized in that: include: Three continuous areas A, B, and C are divided in sequence. A car is placed relatively still in area B for physical modeling, and area B moves forward according to the speed of the vehicle. An AB interface is set between area A and area B, and a BC interface is set between area B and area C. Draw dynamic mesh based on AB and BC interfaces to decouple the impact of inlet velocity and vehicle velocity; The Euler method of computational fluid software is used for numerical simulation, and the turbulence model is simulated based on the large eddy simulation method to obtain the transient data of pollutants in the exhaust gas; The light source emits ultraviolet and infrared beams and receives the light that passes through the exhaust gas, thereby calculating the integrated molar concentration of the pollutants and the contour map of the pollutant diffusion.

2. The method for detecting a simulated vertically arranged road surface remote sensing device according to claim 1, characterized in that: The large eddy simulation method uses a wall-adaptive local eddy viscosity model to capture transient turbulence.

3. The method for detecting a road surface remote sensing device simulating vertical arrangement according to claim 1, characterized in that: The pressure-implicit operator partitioning method is used to solve the pressure-velocity coupling.

4. The method for detecting a road surface remote sensing device simulating vertical arrangement according to claim 1, characterized in that: Area A and area C are located in front of and behind area B respectively. As area B moves forward, the grid of area A closest to area B gradually disappears, and the grid of area C appears.

5. The method for detecting a road surface remote sensing device simulating vertical arrangement according to claim 1, characterized in that: The left and right surfaces of regions A, B, and C are coupled by setting periodic boundaries.

6. The method for detecting a road surface remote sensing device simulating vertical arrangement according to claim 1, characterized in that: The numerical simulation was performed using the Euler method of computational fluid software, including the conservation equations of mass, momentum, energy and species. The absolute standard of the four conservation equations was 10 -12 , the formulas are as follows:

7. The method for detecting a simulated vertically arranged road surface remote sensing device according to claim 1, characterized in that: The formula for calculating the integral molar concentration of pollutants and the contour map of pollutant diffusion is as follows:

8. The method for detecting a simulated vertically arranged road surface remote sensing device according to claim 7, characterized in that: The steps for calculating the integral molar concentration of pollutants and the contour map of pollutant diffusion are as follows: Extract the molar concentration and grid height of the grid to calculate the integral; Multiply the molar concentration and the grid height in the same grid to get a product; Sum these products along each vertical line; The integrated values ​​are averaged to eliminate the influence of time fluctuations; Generate a contour plot in the xz plane.

9. A road surface remote sensing equipment detection system simulating vertical arrangement, characterized in that: include: The physical modeling module is used to sequentially divide three continuous areas, A, B, and C. A car is placed in the B area to be relatively still and perform physical modeling. The B area moves forward according to the speed of the vehicle. An AB interface is set between the A area and the B area, and a BC interface is set between the B area and the C area. Mesh drawing module, which draws dynamic mesh based on AB and BC interfaces, and is used to decouple the effects of inlet speed and vehicle speed; Numerical simulation module, used to perform numerical simulation using the Euler method of computational fluid software, and simulate turbulence models based on large eddy simulation methods, so as to obtain transient data of pollutants in exhaust gas; The pollution calculation module is used to use a light source to emit ultraviolet and infrared beams and receive the light that passes through the exhaust gas, so as to calculate the integral molar concentration of the pollutants and the contour map of the pollutant diffusion.

10. A computer storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the detection method according to any one of claims 1 to 8 is implemented.

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