Acoustic characteristic calculation method, system, device and storage medium of catalytic converter

Abstract

The present application relates to the technical field of vehicle parts, and specifically discloses a method, system, device and storage medium for calculating the acoustic characteristics of a catalytic converter. The method comprises obtaining structural parameter information of the catalytic converter, wherein the structural parameter information comprises the structure of a straight pipe section, a carrier section and a junction section; based on the structural data of each section in the structural parameter information and the gas parameter data, an overall mathematical model of the catalytic converter is established, wherein the overall mathematical model comprises the mathematical models of the straight pipe section and the carrier section, and the acoustic transmission loss model of the catalytic converter is determined according to the overall mathematical model; under different airflow Mach numbers, based on the acoustic transmission loss model, the transmission loss of the catalytic converter at different Mach numbers and frequencies can be quickly obtained to analyze the sound reduction of the catalytic carrier in different frequency bands, and at the same time, the influence of the parameters such as the diameter, length, hole density, perforation rate and hole diameter of the carrier on the sound reduction performance of the catalytic converter can be analyzed.

Description

Technical Field

[0001] The present application relates to the technical field of vehicle components, and in particular to a method, system, device and storage medium for calculating acoustic characteristics of a catalytic converter. Background Art

[0002] As a key component in the automobile exhaust system, the catalytic converter is mainly used to convert harmful exhaust gas components into harmless substances, thereby reducing pollution to the environment. The performance requirements of the catalytic converter are also constantly improving. In addition to the purification function, the catalytic converter also plays an important role in the control of exhaust noise. Therefore, its acoustic characteristics are particularly critical to the overall performance of the vehicle.

[0003] In recent years, automobile designs have tended to be compact to accommodate higher fuel efficiency and space utilization. This design trend has gradually replaced the traditional split exhaust muffler and catalytic converter layout with an integrated design. By integrating the muffler and catalytic converter into one unit, it not only saves space, but also optimizes the exhaust flow and improves the efficiency of the overall system. In addition, the market demand for automobile noise control is increasing, and consumers' requirements for vehicle quietness are also constantly improving, which has forced automakers to consider more complex exhaust system designs to meet users' expectations for comfort and driving experience.

[0004] In the related technologies, although some studies have explored the thermal performance and fluid dynamic characteristics of catalytic converters, there is still a lack of systematic research on their acoustic characteristics, especially the acoustic performance under integrated design. Studying the acoustic characteristics of catalytic converters is of great significance to analyzing the silencer characteristics of the entire exhaust muffler. Therefore, how to effectively evaluate and improve the acoustic characteristics of catalytic converters based on the evaluation to achieve the best exhaust silencer effect has become a problem that needs to be solved urgently. Summary of the invention

[0005] The present application aims to solve the problem in the prior art that there is no accurate and reliable method for obtaining and judging the noise reduction performance of the acoustic characteristics of a catalytic converter. Therefore, a method, system, device and storage medium for calculating the acoustic characteristics of a catalytic converter are proposed.

[0006] In order to achieve the above objectives, in a first aspect, the present application provides a method for calculating the acoustic characteristics of a catalytic converter, comprising:

[0007] The structural parameter information of the catalytic converter is obtained, wherein the structural parameter information includes the straight pipe section structural information, the carrier section structural information and the junction section structural information.

[0008] Based on the structural data of each section and the gas parameter data in the structural parameter information, an overall mathematical model of the catalytic converter is established, wherein the overall mathematical model includes a mathematical model of a straight pipe section and a mathematical model of a carrier section;

[0009] Determining an acoustic transmission loss model of the catalytic converter based on the overall mathematical model;

[0010] Under different airflow Mach numbers, the transmission loss of the catalytic converter at different frequencies is determined based on the acoustic transmission loss model.

[0011] In some possible embodiments, the overall mathematical model of the catalytic converter is established based on the structural data of each segment and the gas parameter data in the structural parameter information, including:

[0012] Ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves;

[0013] Taking into account the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross section at the junction, a mathematical model of the carrier segment is established based on the structural information of the carrier segment and the quasi-plane theory;

[0014] An overall mathematical model of the catalytic converter is established based on the straight pipe section mathematical model and the carrier section mathematical model.

[0015] In some possible embodiments, ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves, including:

[0016] Based on the one-dimensional plane wave theory of small-amplitude sound waves, the particle vibration velocity and wave amplitude corresponding to the straight pipe section are obtained;

[0017] Based on the straight pipe section structure information, the particle vibration velocity and the fluctuation amount, determining a first transfer matrix of the sound pressure and the particle vibration velocity at the inlet and outlet of the straight pipe section, wherein the first transfer matrix constitutes a mathematical model of the straight pipe section;

[0018] The first transfer matrix expression is:

[0019] In the formula, A1, B1, C1, D1 are the four-level parameters of the straight pipe section, p i , v i are the sound pressure and particle vibration velocity at the inlet of the straight pipe section, p0 and v0 are the sound pressure and particle vibration velocity at the outlet of the straight pipe section, respectively.

[0020] In some possible embodiments, the mathematical model of the carrier segment is established based on the carrier segment structure information and quasi-plane theory, taking into account the flow rate and viscosity of the gas, and the sudden contraction and expansion of the cross section at the junction, including:

[0021] Based on the quasi-plane theory of sound propagation in a small pipe when considering the gas flow rate and the thermoviscous effect, and the structural information of the carrier segment, a small pipe mathematical model of the carrier segment is established;

[0022] Based on the equal sound pressure and continuous volume velocity at the critical surface of the straight pipe section and the carrier section, a mathematical model of the inlet and outlet at the junction of the carrier section is established;

[0023] The mathematical model of the carrier segment is determined based on the mathematical model of the thin tube and the mathematical model of the inlet and outlet of the junction.

[0024] In some possible embodiments, the mathematical model of the carrier segment is established based on the carrier segment structure information and quasi-plane theory under the consideration of the flow rate and viscosity of the gas, and the sudden contraction and expansion of the cross section at the junction, and further includes:

[0025] The transfer matrix expression corresponding to the thin tube mathematical model is:

[0026]

[0027] In the formula, are the sound pressure and particle velocity at the inlet of the small tube, are the sound pressure and particle velocity at the outlet of the thin tube, They are the four-level parameters of the small tube;

[0028] The second transfer matrix expression corresponding to the carrier segment mathematical model is:

[0029]

[0030] In the formula, are the sound pressure and particle velocity at the inlet of the carrier segment, are the sound pressure and particle velocity at the outlet of the carrier section, are the four-level parameters of the carrier segment, among which, , , , , is the perforation rate.

[0031] In some possible embodiments, the overall mathematical model of the catalytic converter is established based on the straight pipe section mathematical model and the carrier section mathematical model, including:

[0032] The transfer matrix expression corresponding to the overall mathematical model of the catalytic converter is:

[0033]

[0034] in,

[0035]

[0036]

[0037] In the formula, , , , They are the four-level parameters of the catalytic converter as a whole. , , , They are the four-level parameters of the straight pipe section, , are the sound pressure and particle vibration velocity at the overall inlet of the catalytic converter, , are the sound pressure and particle vibration velocity at the overall outlet of the catalytic converter, respectively.

[0038] In some possible embodiments, the determining of the transmission loss of the catalytic converter at different frequencies based on the acoustic transmission loss model under different airflow Mach numbers includes:

[0039] Obtaining the cutoff frequencies of the straight pipe section and the carrier section, and determining the frequency value range of the acoustic transmission loss model calculation based on the cutoff frequencies;

[0040] Within the frequency value range, based on the acoustic transmission loss model, determining the transmission loss at different frequencies corresponding to different airflow Mach numbers;

[0041] Among them, the corresponding expression of the acoustic transmission loss model is:

[0042]

[0043] In the formula, is the density fluctuation, is the speed of sound, , , , They are the four-level parameters of the catalytic converter.

[0044] Compared with the prior art, the above technical solution provided by this application has at least the following technical effects or advantages:

[0045] 1) Methods The mathematical model is established in sections by combining the geometric structure characteristics of the catalytic converter. When establishing the mathematical model of the straight pipe section, the viscosity of the gas is ignored to establish the transfer matrix relationship between the sound pressure and the particle vibration velocity at the inlet and outlet of the straight pipe section. When establishing the mathematical model of the catalytic converter carrier section, the transfer matrix of the junction between the catalytic converter carrier and the circular straight pipe and the transfer matrix of the inlet and outlet of the thin tube are established respectively. In addition, the gas flow rate and thermal viscosity effect are fully considered for the thin tube of the carrier section to obtain the transfer matrix of the mathematical model of the catalytic converter carrier section. The mathematical models of the straight pipe section and the catalytic converter carrier section are combined to obtain the transfer matrix of the catalytic converter mathematical model. Finally, the acoustic transfer loss model of the entire catalytic converter is obtained through the total transfer matrix of the catalytic converter. Based on the acoustic transfer loss model, the transfer loss of the catalytic converter at different frequencies corresponding to different airflow Mach numbers is quickly obtained.

[0046] 2) The method provided in this application can be used to obtain the transfer loss of the catalytic converter at different Mach numbers and frequencies, and can quickly analyze the sound absorption of the catalytic carrier in different frequency bands. At the same time, the influence of parameters such as the diameter, length, pore density, perforation rate and pore diameter of the carrier on the sound absorption performance (transmission loss) of the catalytic converter can be analyzed, and the influence of different air flow velocities on the sound absorption performance (transmission loss) of the catalytic converter can also be analyzed.

[0047] In a second aspect, the present application provides an acoustic characteristic calculation system for a catalytic converter, comprising:

[0048] The acquisition module is configured to acquire structural parameter information of the catalytic converter, wherein the structural parameter information includes straight pipe section structural information, carrier section structural information and boundary section structural information.

[0049] A model creation module is configured to establish an overall mathematical model of the catalytic converter based on the structural data of each section and the gas parameter data in the structural parameter information, wherein the overall mathematical model includes a mathematical model of a straight pipe section and a mathematical model of a carrier section;

[0050] a determination module configured to determine an acoustic transmission loss model of the catalytic converter based on the overall mathematical model;

[0051] The transmission loss calculation module is configured to determine the transmission loss of the catalytic converter at different frequencies based on the acoustic transmission loss model under different airflow Mach numbers.

[0052] In a third aspect, the present application further provides an electronic device, including:

[0053] at least one processor;

[0054] and a memory communicatively connected to the at least one processor; wherein,

[0055] The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the steps of the method for calculating the acoustic characteristics of a catalytic converter provided in any one of the first aspects mentioned above.

[0056] In a fourth aspect, the present application further provides a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, implement the steps of a method for calculating the acoustic characteristics of a catalytic converter as described in any one of the above-mentioned first aspects.

[0057] It can be understood that the beneficial effects of the technical solutions provided in the second, third and fourth aspects can be found in the relevant description of the first aspect, and will not be repeated here.

[0058] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0060] Figure 1 is a flow chart of a method for calculating acoustic characteristics of a catalytic converter according to an embodiment of the present application;

[0061] Figure 2 is a sub-flow chart of a method for calculating acoustic characteristics of a catalytic converter according to an embodiment of the present application;

[0062] Figure 3 is a cross-sectional view of a catalytic converter according to an embodiment of the present application;

[0063] Figure 4 is a schematic diagram of various sections of a catalytic converter according to an embodiment of the present application;

[0064] Figure 5 is a schematic diagram of the interface between a circular straight pipe section and a carrier section in a catalytic converter according to an embodiment of the present application;

[0065] Figure 6 is a transmission loss curve actually measured according to the acoustic characteristic calculation method based on the catalytic converter according to the embodiment of the present application;

[0066] Figure 7is a block diagram of an acoustic characteristic calculation system of a catalytic converter according to an embodiment of the present application;

[0067] Figure 8 is a block diagram of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0068] The embodiments of the present application are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0069] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific implementations and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0070] For the catalytic converter in the automobile exhaust system, studying the acoustic characteristics of the catalytic converter is of great significance for analyzing the muffler characteristics of the entire exhaust muffler. For example, it can be used to analyze the influence of parameters such as the diameter, length, pore density, perforation rate and pore diameter of the catalytic converter carrier on the muffler performance (transmission loss) of the catalytic converter. For another example, it can be used to analyze the influence of different air flow velocities on the muffler performance (transmission loss) of the catalytic converter. Based on this, the inventor proposes a method, system, device and storage medium for calculating the acoustic characteristics of a catalytic converter. The solution provided in this application will be further described through multiple embodiments below.

[0071] See also Figures 1 to 5 This embodiment provides a method for calculating the acoustic characteristics of a catalytic converter, comprising:

[0072] Step S100: obtaining structural parameter information of the catalytic converter, wherein the structural parameter information includes straight pipe section structural information, carrier section structural information and boundary section structural information.

[0073] In this step, it should be noted that there are certain structural differences between different manufacturers and different models of catalytic converters, but the catalytic converters generally have the same structure, such as Figure 3As shown in the figure, taking a certain catalytic converter structure as an example, the catalytic converter mainly includes a carrier 2 and circular straight tubes 1 at both ends of the carrier 2. The carrier 2 of the catalytic converter is composed of many tiny channels arranged in parallel. At this time, the thermal viscosity of the gas has a significant effect on the attenuation of the sound wave, especially for the noise attenuation of the high-frequency part. Therefore, the acoustic performance analysis in the catalytic converter carrier should fully consider the influence of the thermal viscosity of the gas. For the circular straight tubes at both ends, due to the large diameter, the influence of the thermal viscosity of the gas is very small, so the gas can be treated as an ideal gas.

[0074] At the same time, since the geometric structure of the catalytic converter in the actual automobile exhaust system is relatively complex, in order to facilitate theoretical analysis and calculation, its geometric structure is simplified. The structural parameter information of the catalytic converter mainly includes the straight pipe section structural information, the carrier section structural information and the junction section structural information. The straight pipe section structural information may include parameter data such as the diameter and length of the straight pipes with circular cross-sections at both ends. The carrier section structural information may include parameter data such as the diameter, length, pore density, perforation rate and pore diameter of the carrier. The junction section structural information may include parameter data such as the perforation rate at the junction. The structural parameter information of the catalytic converter may be obtained through manual measurement input or by directly obtaining it by machine by pre-creating a structural model. The specific acquisition method is not limited here.

[0075] Step S200: establishing an overall mathematical model of the catalytic converter based on the structural data of each section and the gas parameter data in the structural parameter information, wherein the overall mathematical model includes a mathematical model of a straight pipe section and a mathematical model of a carrier section;

[0076] In this step, the gas parameter data can be pre-set, and the gas parameter data may include data parameters such as gas constant, sound pressure, density fluctuation and temperature fluctuation. Then, combined with the structural data of each segment in the structural parameter information, an overall mathematical model of the catalytic converter is established. It can be understood that, as described in the previous step, taking into account that the fine holes and the circular straight tubes of the carrier part of the catalytic converter have different effects on the thermal viscosity of the gas, the overall mathematical model of the catalytic converter is segmented to establish a mathematical model, wherein the overall mathematical model may include a straight tube segment mathematical model and a carrier segment mathematical model.

[0077] like Figure 4 As shown, it should be noted that the establishment of the overall mathematical model of the catalytic converter is mainly formed by the transfer matrix relationship of the sound propagation of the entire catalytic converter. In order to obtain the transfer loss of the catalytic converter more accurately, the transfer matrices of different sections of the catalytic converter are established respectively. Finally, the transfer matrix corresponding to the circular straight tube and the transfer matrix of the catalytic converter carrier are connected in series to obtain the transfer matrix expression of the entire catalytic converter. It is assumed that the sound pressure and particle vibration velocity at the inlet of the catalytic converter are respectively , , and the sound pressure and particle velocity at the outlet are , , and, assuming that the sound pressure and particle velocity at the inlet of the catalytic converter substrate are 、 , and the sound pressure and particle velocity at the outlet are , , the process of establishing the mathematical model is described in detail below in conjunction with the embodiments.

[0078] like Figure 2 As shown, in some examples, the establishment of the straight pipe section mathematical model, the carrier section mathematical model and the final overall mathematical model includes the following steps:

[0079] Step S210: Ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves;

[0080] In this step, based on the one-dimensional plane wave theory of small-amplitude sound waves, the particle velocity and fluctuation amount corresponding to the straight pipe section are obtained; based on the straight pipe section structure information, the particle velocity and fluctuation amount corresponding to the straight pipe section, the first transfer matrix of the sound pressure and particle velocity at the inlet and outlet of the straight pipe section is determined, wherein the first transfer matrix constitutes the mathematical model of the straight pipe section.

[0081] Specifically, due to the large diameter of the straight tube with circular cross-section at both ends, the effect of gas viscosity on the propagation of sound can be ignored. Therefore, the gas in the straight tube can be treated as an ideal gas. Based on the one-dimensional plane wave theory of small amplitude sound waves, after ignoring the traces above the second level, the so-called linearization procedure, the following three control equations can be obtained:

[0082] Equations of motion: (1)

[0083] Momentum equation: (2)

[0084] Continuity equation: (3)

[0085] In the formula, , p are density fluctuation and sound pressure respectively, where the subscript 0 indicates the average value, is the average speed of sound, is the average density fluctuation.

[0086] Combining equations (1), (2) and (3) we can obtain the wave equation of an ideal gas one-dimensional plane wave: (4)

[0087] Solving the wave equation (4) we can obtain: (5)

[0088] In the formula, is the wave number, while A and B are arbitrary constants determined by the boundary conditions, and j is an imaginary number.

[0089] Then, the expression of particle velocity can be obtained from (1): (6), taking a certain moment, that is, removing the time term, a mathematical model for the sound propagation in the straight pipe is established, that is, the transfer matrix relationship between the sound pressure and the particle vibration velocity at the inlet and outlet of the straight pipe is established. Suppose the sound pressure and the particle vibration velocity at the inlet and outlet are p respectively. i 、v i , p0, v0, then the first transfer matrix expression is: (7)

[0090] Where A1, B1, C1, and D1 are the four-level parameters of the straight pipe section.

[0091] We can solve equations (5) and (6) to get:

[0092] (8)

[0093] In the formula, k is the wave number, j is an imaginary number, l is the propagation length (straight pipe length).

[0094] Step S220: establishing a mathematical model of the carrier segment based on the carrier segment structure information and quasi-plane theory, taking into account the flow velocity and viscosity of the gas, and the sudden contraction and expansion of the cross section at the junction;

[0095] In this step, since the fine tubes of the catalytic converter carrier section and the critical surface between the straight tube section and the carrier section have different effects on acoustic propagation, a mathematical model of the fine tubes of the carrier section is established based on the quasi-plane theory of sound propagation in fine pipes when considering gas flow rate and thermal viscosity effects, as well as the structural information of the carrier section; a mathematical model of the inlet and outlet at the junction of the carrier section is established based on the equal sound pressure and continuous volume velocity at the critical surface between the straight tube section and the carrier section; and a mathematical model of the carrier section is determined based on the mathematical model of the fine tubes and the mathematical model of the inlet and outlet at the junction.

[0096] Furthermore, the establishment process of the transfer matrix corresponding to the mathematical model of the carrier section will be specifically analyzed below by combining the specific structure of the catalytic converter and the sound propagation characteristics:

[0097] Due to the tiny pore structure of the catalytic converter, the viscosity of the gas has a significant effect on the propagation of sound. Therefore, the gas can no longer be treated as an ideal gas. It is necessary to establish a control equation for sound propagation that takes into account flow velocity, heat conduction and viscosity effects. The control equations that can describe the propagation of sound in the pipeline are the Navier-Stokes equation, the continuity equation, the energy equation and the state equation. Assuming that the axisymmetric sound waves are superimposed on the uniform axial average flow, the uniform flow velocity is v0, and the functional relationship between each sound field parameter and time is , after transformation, the control equations are:

[0098] Navier-Stokes equations: (9)

[0099] (10)

[0100] Continuity equation: (11)

[0101] Energy equation: (12)

[0102] Equation of state: (13)

[0103] The boundary conditions are:

[0104] when hour, and and T Must be a finite value;

[0105] when hour, .

[0106] In the formula, j is an imaginary number, r is the inner radius of the small tube, is the circular frequency, , and p They are density fluctuation, temperature fluctuation and sound pressure respectively; R is the gas constant; subscript 0 indicates an average value.

[0107] Furthermore, it can be assumed that the variables in the sound field are related to x The functional relationship is , is the wave number in the inviscid case, is the speed of sound, is the unknown propagation constant. From (10), we know that the sound pressure p Only with x The sound field variables can be set as:

[0108]

[0109] In the formula, A is a constant, H and F About r function.

[0110] Substituting formula (14) into formula (9) and (12) yields:

[0111]

[0112] in, , is the Stokes number, is the Mach number of uniform flow, is the Prandtl constant, is the radius of the pipe.

[0113] Equations (15) and (16) can be expressed using Bessel functions The expression for the solution is:

[0114]

[0115] Substituting equations (14) and (17) into equation (13), we can obtain:

[0116]

[0117] in, .

[0118] Substituting equations (14) and (18) into equation (11), we can obtain:

[0119]

[0120] The above formula is r The points can be obtained:

[0121] (19)

[0122] Then the boundary condition and Substituting into (19) we can get K The characteristic equation of is:

[0123]

[0124] By approximating and simplifying equation (20), we can obtain K Solution:

[0125]

[0126] In the formula, is the propagation constant

[0127]

[0128] According to the propagation theory of one-dimensional waves, and Represents a one-dimensional wave as well as When propagating in the direction, the propagation constant of thermoviscosity is considered. Therefore, the solution of the wave equation considering thermoviscosity can be:

[0129]

[0130] Substituting (17) into (14), we can obtain:

[0131]

[0132] in:

[0133] (25)

[0134] When the cross-sectional area of ​​the pipe is large, the radial contribution of these functions does not change much on the pipe cross section, so equation (24) can be integrated on the pipe cross section and its average value on the pipe cross section can be calculated. This is the application form in actual general pipes.

[0135]

[0136] in:

[0137] (27)

[0138] And by: (28)

[0139] From (27), we get:

[0140]

[0141] For (27) By approximating , we can get:

[0142]

[0143] Equations (21)(23)(26)(30)(31) constitute the quasi-plane theory of sound propagation in small pipes when considering flow velocity and thermoviscous effects.

[0144] Length of catalytic converter , the specific value can be selected according to actual needs. Assume that the sound pressure and particle vibration velocity at the inlet and outlet of the thin tube are , then the transfer matrix expression of the inlet and outlet is established as: (32)

[0145] in, It can be calculated by (23) (26),

[0146] (33)

[0147] In the formula, are the sound pressure and particle velocity at the inlet and outlet of the thin tube, respectively. They are the four-level parameters of the small tube;

[0148] In some examples, such as Figure 5 As shown in the figure, at the junction of the catalytic converter carrier and the round straight pipe, there is a sudden contraction and expansion of the cross section. is the diameter of the circular straight tube, is the diameter of the catalytic converter carrier, is the porosity, and at the critical surface, the transfer matrix equation can be established by assuming that the sound pressure is equal and the volume velocity is continuous. For the case at the entrance: (34)

[0149] According to formula (34), the transfer matrix expression at the inlet is established as: (35)

[0150] Similarly, the transfer matrix at the exit is: (36)

[0151] In the formula, is the perforation rate.

[0152] Combining equations (32), (35) and (36), we get the transfer matrix equation of the catalytic converter carrier:

[0153] (37)

[0154] in: (38)

[0155] In the formula, are the sound pressure and particle vibration velocity at the inlet and outlet of the carrier segment, respectively. They are the four-level parameters of the carrier segment.

[0156] Step S230: establishing an overall mathematical model of the catalytic converter according to the straight pipe section mathematical model and the carrier section mathematical model.

[0157] In this step, combine Figure 4, the transfer matrix corresponding to the mathematical model of the straight pipe section and the mathematical model of the carrier section created in the above steps, and the transfer matrix corresponding to the overall mathematical model of the catalytic converter obtained by connecting the parts in series,

[0158] Right now: (39)

[0159] Finally, the transfer matrix expression corresponding to the overall mathematical model of the catalytic converter is obtained as follows:

[0160] (40)

[0161] in,

[0162]

[0163]

[0164] In the formula, , , , They are the four-level parameters of the catalytic converter as a whole, , , , They are the four-level parameters of the straight pipe section, , are the sound pressure and particle vibration velocity at the overall inlet of the catalytic converter, , are the sound pressure and particle vibration velocity at the overall outlet of the catalytic converter, respectively.

[0165] Step S300: determining an acoustic transmission loss model of the catalytic converter according to the overall mathematical model;

[0166] In this step, the transfer matrix corresponding to the overall mathematical model is used to determine , , , , and based on the outlet boundary condition as a non-reflecting end, the acoustic transmission loss of the entire catalytic converter can be expressed as:

[0167] (42)

[0168] In the formula, is the density fluctuation, is the speed of sound, and D is a constant term.

[0169] Step S400: Under different airflow Mach numbers, based on the acoustic transmission loss model, determining the transmission loss of the catalytic converter at different frequencies.

[0170] In this step, since the acoustic transmission loss model is based on the one-dimensional plane wave theory, if the corresponding frequency of the calculated transmission loss exceeds the cutoff frequency of the straight pipe section and the carrier section, it will directly affect the simulation calculation results of the acoustic transmission loss. Therefore, it is necessary to obtain the cutoff frequencies of the straight pipe section and the carrier section by calculating respectively, and determine the frequency value range of the acoustic transmission loss model calculation based on the minimum cutoff frequency in the straight pipe section and the carrier section, that is, the maximum end value of the frequency value range is less than the minimum cutoff frequency in the straight pipe section and the carrier section. Within this frequency value range, based on the acoustic transmission loss model, determine the transmission loss at different frequencies corresponding to different airflow Mach numbers.

[0171] Specifically, in response to different set Mach numbers, an acoustic transmission loss model is established to obtain a transmission loss curve of the catalytic converter at different frequencies, and the transmission loss of the catalytic converter at different Mach numbers and frequencies is obtained through the curve.

[0172] Through the above method steps, the mathematical model is established in sections in combination with the geometric structure characteristics of the catalytic converter. When establishing the mathematical model of the straight pipe section, the viscosity of the gas is ignored to establish the transfer matrix relationship between the sound pressure and the particle vibration velocity at the inlet and outlet of the straight pipe section. When establishing the mathematical model of the catalytic converter carrier section, the transfer matrix of the junction between the catalytic converter carrier and the circular straight pipe and the transfer matrix of the inlet and outlet of the thin tube are established respectively. In addition, the gas flow rate and thermal viscosity effect are fully considered for the thin tube of the carrier section to obtain the transfer matrix of the mathematical model of the catalytic converter carrier section. The mathematical model of the straight pipe section and the catalytic converter carrier section are combined to obtain the transfer matrix of the mathematical model of the catalytic converter. Finally, the acoustic transmission loss model of the entire catalytic converter is obtained through the total transfer matrix of the catalytic converter. Based on the acoustic transmission loss model, the transmission loss of the catalytic converter at different frequencies corresponding to different airflow Mach numbers can be quickly obtained.

[0173] At the same time, the transfer loss of the catalytic converter at different Mach numbers and frequencies can be obtained through the above method steps, so as to quickly analyze the sound absorption of the catalytic carrier in different frequency bands, and analyze the influence of parameters such as the diameter, length, pore density, perforation rate and pore diameter of the carrier on the sound absorption performance (transmission loss) of the catalytic converter. It is also possible to analyze the influence of different air flow velocities on the sound absorption performance (transmission loss) of the catalytic converter.

[0174] The following provides a practical application of the acoustic characteristics calculation method of the catalytic converter provided in the above embodiment;

[0175] See also Figure 6 , Figure 6The acoustic transmission loss of a catalytic converter at different frequencies obtained based on the practical application of the above method steps is shown. Before the calculation is performed, the calculation conditions are first determined. It can be understood that the calculation conditions need to be set according to actual needs. This embodiment only provides one of the conditions as an example, wherein the calculation conditions are: exhaust temperature 600°C, specific heat ratio =1.4, gas constant R = 287 , atmospheric pressure , since the above theories are all based on one-dimensional plane wave theory, the calculated frequency cannot exceed the cutoff frequency of the pipeline, based on the calculation formula of the cutoff frequency: The cutoff frequency of the circular straight pipe section is 1722Hz, and the cutoff frequency of the catalytic converter substrate section is 264673Hz. Therefore, the calculation frequency range can be set to 0 ~ 1600Hz, and the Mach number M (i.e., gas flow rate) is set to 0.05, 0.1, and 0.15 for analysis. Figure 6 It can be seen that under the given gas flow rates, the transmission loss is basically between 2 and 6 dB And above 400Hz, the transmission loss gradually increases with the increase of frequency. At the same time, the figure shows the effect of gas flow rate on the transmission loss of the catalytic converter. The greater the gas flow rate, the smaller the transmission loss of the catalytic converter.

[0176] See also Figure 7 , Figure 7 A block diagram of an acoustic feature calculation system 200 for a catalytic converter provided in this embodiment is shown. The acoustic feature calculation system 200 for a catalytic converter includes:

[0177] The acquisition module 210 is configured to acquire structural parameter information of the catalytic converter, wherein the structural parameter information includes straight pipe section structural information, carrier section structural information and boundary section structural information.

[0178] The model creation module 220 is configured to establish an overall mathematical model of the catalytic converter based on the structural data of each section and the gas parameter data in the structural parameter information, wherein the overall mathematical model includes a mathematical model of a straight pipe section and a mathematical model of a carrier section;

[0179] A determination module 230 is configured to determine an acoustic transmission loss model of the catalytic converter according to the overall mathematical model;

[0180] The transmission loss calculation module 240 is configured to determine the transmission loss of the catalytic converter at different frequencies based on the acoustic transmission loss model under different airflow Mach numbers.

[0181] In some embodiments, the model creation module 220 is also configured to establish a mathematical model of the straight pipe section based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves while ignoring the viscosity of the gas; establish a mathematical model of the carrier section based on the structural information of the carrier section and the quasi-plane theory while considering the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross-section at the junction; and establish an overall mathematical model of the catalytic converter based on the mathematical model of the straight pipe section and the mathematical model of the carrier section.

[0182] It is understandable that when the acoustic characteristic calculation system 200 of the catalytic converter in this embodiment is implemented, each module runs the above Figures 1 to 5 The steps of the method for calculating the acoustic characteristics of the catalytic converter in the corresponding embodiment and the technical effects that can be achieved can be referred to the above Figures 1 to 5 The corresponding embodiments are described in detail and will not be elaborated here.

[0183] See also Figure 8 , Figure 8 5 is a block diagram of an electronic device provided in an embodiment of the present application. The server 500 of the electronic device includes: a processor 501, a memory 502, and a computer program 503 stored in the memory 502 and executable on the processor 501, such as a program for calculating the acoustic characteristics of a catalytic converter. When the processor 501 executes the computer program 503, the steps of the method for calculating the acoustic characteristics of a catalytic converter in the above-mentioned embodiments are implemented, such as Figure 1 Alternatively, the processor 501 executes the computer program 503 to implement the above Figure 7 The functions of each module in the corresponding embodiment are, for example, Figure 7 For details on the functions of the modules (eg, acquisition module 210), please refer to Figure 7 The relevant descriptions in the corresponding embodiments are not repeated here.

[0184] Exemplarily, the computer program 503 may be divided into one or more units, one or more units are stored in the memory 502, and are executed by the processor 501 to complete the technical solution provided in the above embodiment. One or more units may be a series of computer program instruction segments that can complete specific functions, and the instruction segments are used to describe the execution process of the computer program 503 in the server 500.

[0185] The electronic device may include, but is not limited to, a processor 501 and a memory 502. Those skilled in the art will appreciate that Figure 8It is only an example of the server 500 and does not constitute a limitation of the server 500. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the turntable terminal device may also include an input and output terminal device, a network access terminal device, a bus, etc.

[0186] The processor 501 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0187] The memory 502 may be an internal storage unit of the server 500, such as a hard disk or memory of the server 500. The memory 502 may also be an external storage terminal device of the server 500, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the server 500. Further, the memory 502 may also include both an internal storage unit of the server 500 and an external storage terminal device. The memory 502 is used to store computer programs and other programs and data required by the turntable terminal device. The memory 502 may also be used to temporarily store data that has been output or is to be output.

[0188] In some embodiments, a computer-readable storage medium is also provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of a method for calculating the acoustic characteristics of a catalytic converter as described in any of the above embodiments are implemented.

[0189] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0190] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium can be non-volatile or volatile. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable storage medium may include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0191] The terms "first", "second", "third", etc. in the specification and claims of the present application and the drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a series of steps or units are included, or optionally, steps or units not listed are included, or optionally, other steps or units inherent to these processes, methods, products or devices are included.

[0192] Only the part relevant to the present application is shown in the accompanying drawings, but not all of the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processing or methods depicted as flow charts. Although the flow chart describes each operation (or step) as a sequential process, many of the operations therein can be implemented in parallel, concurrently or simultaneously. In addition, the order of each operation can be rearranged. When its operation is completed, the process can be terminated, but it can also have additional steps not included in the accompanying drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0193] The terms "component", "module", "system", "unit", etc. used in this specification are used to represent computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a unit can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or distributed between two or more computers. In addition, these units can be executed from various computer-readable media having various data structures stored thereon. Units can communicate through local and / or remote processes, for example, based on signals having one or more data packets (e.g., data from a second unit interacting with another unit in a local system, a distributed system, and / or a network. For example, the Internet interacts with other systems via signals).

[0194] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" 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 application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0195] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0196] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

[0197] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the disclosure disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

Claims

1. A method for calculating the acoustic characteristics of a catalytic converter, characterized in that: include: Acquiring structural parameter information of the catalytic converter, wherein the structural parameter information includes straight pipe section structural information, carrier section structural information and junction section structural information; Based on the structural data of each section and the gas parameter data in the structural parameter information, an overall mathematical model of the catalytic converter is established, wherein the overall mathematical model includes a straight pipe section mathematical model and a carrier section mathematical model, wherein: Ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves; considering the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross-section at the junction, a mathematical model of the carrier section is established based on the structural information of the carrier section and the quasi-plane theory; based on the mathematical model of the straight pipe section and the mathematical model of the carrier section, an overall mathematical model of the catalytic converter is established. The transfer matrix expression corresponding to the overall mathematical model of the catalytic converter is: in, In the formula, They are the four-level parameters of the catalytic converter as a whole. They are the four-level parameters of the straight pipe section, are the sound pressure and particle vibration velocity at the overall inlet of the catalytic converter, are the sound pressure and particle vibration velocity at the overall outlet of the catalytic converter respectively; Determining an acoustic transmission loss model of the catalytic converter based on the overall mathematical model; Under different airflow Mach numbers, the transmission loss of the catalytic converter at different frequencies is determined based on the acoustic transmission loss model.

2. The method for calculating the acoustic characteristics of a catalytic converter according to claim 1, characterized in that: Ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves, including: Based on the one-dimensional plane wave theory of small-amplitude sound waves, the particle vibration velocity and wave amplitude corresponding to the straight pipe section are obtained; Based on the straight pipe section structure information, the particle vibration velocity and the fluctuation amount, determining a first transfer matrix of the sound pressure and the particle vibration velocity at the inlet and outlet of the straight pipe section, wherein the first transfer matrix constitutes a mathematical model of the straight pipe section; The first transfer matrix expression is: In the formula, A1, B1, C1, D1 are the four-level parameters of the straight pipe section, p i , v i are the sound pressure and particle vibration velocity at the inlet of the straight pipe section, p0 and v0 are the sound pressure and particle vibration velocity at the outlet of the straight pipe section, respectively.

3. The method for calculating the acoustic characteristics of a catalytic converter according to claim 1, characterized in that: The mathematical model of the carrier segment is established based on the carrier segment structure information and quasi-plane theory, taking into account the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross section at the junction, including: Based on the quasi-plane theory of sound propagation in a small pipe when considering the gas flow rate and the thermoviscous effect, and the structural information of the carrier segment, a small pipe mathematical model of the carrier segment is established; Based on the equal sound pressure and continuous volume velocity at the critical surface of the straight pipe section and the carrier section, a mathematical model of the inlet and outlet at the junction of the carrier section is established; The mathematical model of the carrier segment is determined based on the mathematical model of the thin tube and the mathematical model of the inlet and outlet of the junction.

4. The method for calculating the acoustic characteristics of a catalytic converter according to claim 3, characterized in that: The method of establishing a mathematical model of the carrier segment based on the carrier segment structure information and quasi-plane theory in consideration of the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross section at the junction, further includes: The transfer matrix expression corresponding to the thin tube mathematical model is: In the formula, , are the sound pressure and particle velocity at the inlet of the small tube, are the sound pressure and particle velocity at the outlet of the thin tube, They are the four-level parameters of the small tube; The second transfer matrix expression corresponding to the carrier segment mathematical model is: In the formula, are the sound pressure and particle velocity at the inlet of the carrier segment, are the sound pressure and particle velocity at the outlet of the carrier section, are the four-level parameters of the carrier segment, among which, , , , , is the perforation rate.

5. The method for calculating the acoustic characteristics of a catalytic converter according to claim 1, characterized in that: The step of determining the transmission loss of the catalytic converter at different frequencies based on the acoustic transmission loss model under different airflow Mach numbers includes: Obtaining the cutoff frequencies of the straight pipe section and the carrier section, and determining the frequency value range of the acoustic transmission loss model calculation based on the cutoff frequencies; Within the frequency value range, based on the acoustic transmission loss model, determining the transmission loss at different frequencies corresponding to different airflow Mach numbers; Among them, the corresponding expression of the acoustic transmission loss model is: In the formula, is the density fluctuation, is the speed of sound, They are the four-level parameters of the catalytic converter.

6. A system for calculating acoustic characteristics of a catalytic converter, characterized in that: include: An acquisition module is configured to acquire structural parameter information of the catalytic converter, wherein the structural parameter information includes straight pipe section structural information, carrier section structural information and junction section structural information; The model creation module is configured to establish an overall mathematical model of the catalytic converter based on the structural data of each section and the gas parameter data in the structural parameter information, wherein the overall mathematical model includes a straight pipe section mathematical model and a carrier section mathematical model, wherein: Ignoring the viscosity of the gas, a mathematical model of the straight pipe section is established based on the structural information of the straight pipe section and the one-dimensional plane wave theory of small-amplitude sound waves; considering the flow rate and viscosity of the gas, as well as the sudden contraction and expansion of the cross-section at the junction, a mathematical model of the carrier section is established based on the structural information of the carrier section and the quasi-plane theory; based on the mathematical model of the straight pipe section and the mathematical model of the carrier section, an overall mathematical model of the catalytic converter is established. The transfer matrix expression corresponding to the overall mathematical model of the catalytic converter is: in, In the formula, They are the four-level parameters of the catalytic converter as a whole. They are the four-level parameters of the straight pipe section, are the sound pressure and particle vibration velocity at the overall inlet of the catalytic converter, are the sound pressure and particle vibration velocity at the overall outlet of the catalytic converter respectively; a determination module configured to determine an acoustic transmission loss model of the catalytic converter based on the overall mathematical model; The transmission loss calculation module is configured to determine the transmission loss of the catalytic converter at different frequencies based on the acoustic transmission loss model under different airflow Mach numbers.

7. An electronic device, characterized in that: include: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the steps of the method for calculating the acoustic characteristics of a catalytic converter according to any one of claims 1-5.

8. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, the steps of the method for calculating the acoustic characteristics of a catalytic converter according to any one of claims 1 to 5 are implemented.

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