A method for optimizing low flow resistance intake muffler

Abstract

The present invention discloses a method for optimizing a low flow resistance intake muffler, comprising the following steps: selecting a curved perforated pipe muffler as a design optimization object; measuring the noise characteristics of the engine intake system of a car during rapid acceleration to determine the noise peak frequency band; determining the target frequency at which the transmission loss peak of the perforated pipe muffler is located; setting the structural parameters of the perforated pipe main pipe according to the layout space of the engine compartment and the dimensions of the intake pipe; and calculating the optimal structural design scheme of the perforated muffler using the response surface analysis method. The present invention has the following positive effects: (1) The finite element calculation method is used to quickly predict the performance of the intake muffler at a low cost. (2) The response surface analysis method is used to fit a response surface approximate model of the transmission loss and pressure loss of the intake muffler, and the muffler performance can be quickly calculated based on the approximate model. (3) While meeting the requirements for noise reduction of the intake system, the intake flow resistance of the intake muffler can be minimized, thereby improving the intake efficiency and fuel economy of the engine.

Description

Technical Field

[0001] The invention relates to the technical field of automobile engine noise reduction, and in particular to a method for optimizing a low flow resistance intake muffler. Background Art

[0002] Engine noise is the main source of vehicle noise and is related to the NVH performance level of the vehicle. Engine noise and exhaust noise are more obvious and are the first to receive attention. The exhaust pipe is long, so there is a lot of space for silencing components. Its control technology is relatively mature, so it can be effectively controlled. The intake system, as another noise source that affects the noise inside the car, has received more attention.

[0003] Arranging an intake muffler on the intake system is an effective way to reduce intake noise. The performance of the intake muffler directly affects the noise reduction effect of the intake noise and the intake efficiency of the engine, which in turn affects the NVH performance and fuel economy of the vehicle.

[0004] Limited by the space of the engine compartment and the direction of the intake system pipeline, the structure of the intake muffler is often irregular, and the curved perforated tube muffler is often designed and installed in the intake system. This muffler has the advantages of high temperature resistance, oil resistance, corrosion resistance, simple structure, and easy processing. It can also be used in harsh environments with high-speed and high-temperature airflow. As a basic muffler element for noise reduction in the intake system, a muffler with a suitable resonance sound absorption peak can be designed by changing structural factors such as the size, position and number of perforations on the main pipeline. At the same time, these structural factors will affect the air flow of the muffler. However, the quantitative relationship between these structural factors and the peak frequency of the muffler transmission loss and the air flow is not clear, and there is no design method for the curved perforated tube intake muffler. Summary of the invention

[0005] The present invention overcomes the shortcomings of the prior art and provides a method for optimizing a low flow resistance intake muffler. The method uses a finite element calculation method for the intake muffler, obtains a response surface approximate model of the muffler transmission loss and pressure loss according to the response surface analysis method, and finally calculates the structural parameters of the intake muffler with the lowest air flow resistance and meeting the noise reduction requirements.

[0006] To achieve the above purpose, the technical solution provided by the present invention is: a method for optimizing a low flow resistance intake muffler. First, the noise peak frequency band of the engine intake system during rapid acceleration of the vehicle is measured, then the peak target frequency of the transmission loss of the intake muffler is determined, and finally the optimal structural parameters of the muffler design are obtained according to the response surface analysis method. The specific steps are as follows:

[0007] Step 1, selecting a bent perforated pipe muffler as a design optimization object;

[0008] Step 2, measuring the noise characteristics of the engine intake system when the car accelerates suddenly, and determining the frequency band where the noise peak is located;

[0009] Step 3, determining the target frequency where the transmission loss peak of the perforated tube muffler is located according to the frequency band where the noise peak is located;

[0010] Step 4, according to the layout space of the engine compartment and the size of the air intake duct, set the structural parameters of the perforated pipe main pipe diameter, bending radius, bending diameter, muffler cavity diameter and cavity length;

[0011] Step 5, calculate the optimal structural design scheme of the perforated silencer, determine the structural parameters of the main factors affecting the transmission loss of the silencer, the structural parameters of the perforation diameter d, the number of holes n, the distance D between the perforation center and the center line of the pipe, and the perforation thickness h.

[0012] Furthermore, the curved perforated pipe silencer in step 1 is composed of a curved main pipe with a plurality of through circular holes and a silencer chamber.

[0013] Furthermore, in step 2, the third gear throttle opening 100% rapid acceleration is selected as a typical operating condition to measure the noise characteristics of the intake system.

[0014] Furthermore, in step 5, a fitting function between the central frequency of the perforated muffler transmission loss and its influencing factors is obtained using the response surface analysis method.

[0015] Furthermore, in step 5, a fitting function of the pressure loss of the perforated muffler and its influencing factors is obtained using the response surface analysis method.

[0016] Furthermore, the step 5 specifically includes the following steps:

[0017] (1) Based on the structural parameters of the main factors affecting the transmission loss of the muffler, such as the diameter of the perforation d, the number of holes n, the distance D between the center of the perforation and the center line of the pipe, and the perforation thickness h, the muffler sample data table was generated using the central composite design method in the response surface experimental design.

[0018] (2) Based on the parameters in the sample data table, use 3D modeling software to build 3D models of all muffler samples.

[0019] (3) Using finite element acoustic analysis software, calculate the transmission loss of all muffler samples and obtain the frequency f at which the transmission loss peaks. The calculation formula for transmission loss is:

[0020]

[0021] Among them, W in is the incident sound power level at the entrance, Wout is the outlet radiated sound power level.

[0022] (4) Use fluid mechanics analysis software to calculate the pressure loss of all muffler samples under common working conditions.

[0023] (5) With the perforation diameter d, the number of holes n, the distance D between the perforation center and the pipeline centerline, and the perforation thickness h as input variables, and the transmission loss peak frequency f as the output variable, the second-order polynomial modeling method is selected, and the polynomial function is constructed to fit the sample space by solving the response surface polynomial coefficients, and the response surface approximate model of the transmission loss peak frequency is established.

[0024] (6) With the perforation diameter d, the number of holes n, the distance D between the perforation center and the pipeline centerline, and the perforation thickness h as input variables and the pressure loss as the output variable, the second-order polynomial modeling method is selected, and the polynomial function is constructed to fit the sample space by solving the response surface polynomial coefficients to establish an approximate response surface model of pressure loss.

[0025] (7) Based on the target frequency of the transmission loss peak of the perforated tube muffler and the response surface approximation model, all design variable combinations that meet the target frequency band are calculated.

[0026] (8) All design variable combinations that meet the target frequency are substituted into the response surface approximation model of pressure loss, and the pressure losses of the silencers of all design variable combinations are calculated and compared. The combination with the smallest pressure loss is the optimal intake silencer design.

[0027] Furthermore, in step (5), the response surface approximation model function expression of the transmission loss peak frequency is:

[0028]

[0029] Among them, α0, α1, …, α 2N , α ij are the coefficients of each polynomial, X0, X1, …, X N , X i , X j are the variable factors, and N is the number of variable factors.

[0030] Furthermore, in the step (6), the response surface approximate model function expression of the pressure loss is:

[0031]

[0032] Among them, β0, β1, …, β 2N , β ij are the coefficients of each polynomial.

[0033] The technical solution of the present invention has the following positive effects:

[0034] (1) The finite element calculation method can quickly predict the performance of the intake muffler at a low cost.

[0035] (2) The response surface analysis method is used to fit the response surface approximate model of the transmission loss and pressure loss of the intake muffler. The muffler performance can be quickly calculated based on the approximate model, and the intake muffler design can be quickly completed according to different noise characteristics.

[0036] (3) While meeting the requirements for noise reduction of the intake system, the intake flow resistance of the intake muffler can be minimized, thereby improving the engine's intake efficiency and fuel economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flow chart of the method of the present invention;

[0038] Figure 2 It is a schematic diagram of the structure of the intake muffler optimized by the present invention; DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. The implementation case is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0040] like Figure 1 As shown, a method for optimizing a low flow resistance intake muffler comprises the following steps:

[0041] Step 1: Select a curved perforated pipe silencer as the design optimization object. Its structure is usually composed of a curved cylindrical silencer cavity and a concentric curved main pipe, and a certain number and size of circular through holes are arranged on the main pipe.

[0042] Step 2, placing the microphone in the near field of the engine compartment air intake duct, measuring the noise characteristics of the engine intake system of a certain car when the throttle opening of the third gear is 100% during rapid acceleration. According to the measurement results, the frequency band where the noise peak is located is in the frequency band near the frequency f0.

[0043] Step 3, according to the noise peak frequency band measured in the previous step, determine the target frequency f0 where the transmission loss peak of the perforated tube muffler is located;

[0044] Step 4: According to the layout space of the engine compartment and the size of the air intake pipe, set the structural parameters such as the diameter of the perforated pipe main pipe, the bending radius, the bending diameter, the silencer cavity diameter and the cavity length. The structure is shown in the figure below. Figure 2 shown.

[0045] Step 5, using the response surface analysis method to calculate the optimal structural design of the perforated muffler, determine the four main parameters that affect the transmission loss of the muffler, namely, the diameter d of the perforation, the number of holes n, the distance D between the perforation center and the center line of the pipe, and the perforation thickness h, which specifically include the following steps:

[0046] (1) According to the structural parameters of the main factors affecting the transmission loss of the muffler, such as the diameter d of the perforation, the number of holes n, the distance D between the center of the perforation and the center line of the pipe, and the perforation thickness h, the value ranges of the four parameter design variables are shown in Table 1. The central composite design method in the response surface experimental design is adopted to express the values ​​of each parameter as a standard variable. The values ​​corresponding to the standard variables are shown in Table 2 below. The final muffler sample data table is shown in Table 3.

[0047] Table 1 Design variable range of intake muffler parameters

[0048]

[0049] Table 2 Standard variable table of intake muffler parameters

[0050]

[0051] Table 3 Sample table of standard variables for muffler response surface test design

[0052]

[0053] (2) Based on the parameters in the sample data table, use 3D modeling software to build 3D models of all muffler samples.

[0054] (3) Use finite element acoustic analysis software to calculate the transmission loss of all muffler samples and obtain the frequency f at which the transmission loss peaks. Take the inlet as 1W sound power and the outlet as a full sound absorption interface as the boundary conditions of the acoustic analysis, calculate the incident sound power and radiated sound power at the inlet and outlet of the muffler, and then calculate the muffler transmission loss according to the transmission loss calculation formula. The calculation formula for transmission loss is:

[0055]

[0056] Among them, W in is the incident sound power at the entrance, W out is the outlet radiated sound power.

[0057] (4) Using fluid mechanics analysis software, with flow inlet and pressure outlet as boundary conditions, the pressure loss of all muffler samples under common working conditions is calculated. The calculation results are shown in Table 4. Due to space constraints, only part of the data is listed as an example.

[0058] Table 4 Calculation results of muffler samples

[0059]

[0060] (5) With the perforation diameter d, the number of holes n, the distance D between the perforation center and the pipeline centerline, and the perforation thickness h as input variables, and the transmission loss peak frequency f as the output variable, the second-order polynomial modeling method is selected, and the polynomial function is constructed to fit the sample space by solving the response surface polynomial coefficients, and the response surface approximate model of the transmission loss peak frequency is established.

[0061] f=α0+α1d+α2n+α3D+α4h+α5dn+α6dD+α7dh+α8nD+α9nh+α 10 Dh+α 11 d 2 +α 12 n 2 +α 13 D 2 +α 14 h 2

[0062] Among them, α0, α1, α2,…,α 14 is the influence coefficient of each factor in the equation.

[0063] (6) The perforation diameter d, the number of holes n, the distance D between the perforation center and the pipeline centerline, and the perforation thickness h are used as input variables, and the pressure loss P is used as the output variable. The second-order polynomial modeling method is selected, and the polynomial function is constructed to fit the sample space by solving the response surface polynomial coefficients, and the response surface approximate model of pressure loss is established.

[0064] P=β0+β1d+β2n+β3D+β4h+β5dn+β6dD+β7dh+β8nD+β9nh+β 10 Dh+β 11 d 2 +β 12 n 2 +β 13 D 2 +β 14 h 2

[0065] Among them, β0, β1, β2,…,β 14 is the influence coefficient of each factor in the equation.

[0066] (7) Based on the target frequency of the perforated tube muffler's transmission loss peak and the transmission loss peak frequency response surface approximate model, all design variable combinations that meet the target frequency band are calculated. The target frequency is set to a small range, i.e., f0-5≤f≤f0+5Hz. Since the number of variable combinations that meet the conditions is generally dozens or even hundreds, they are not listed here one by one.

[0067] (8) Substitute all the design variable combinations that meet the target frequency into the response surface approximation model of pressure loss, calculate the pressure loss of the silencer with all the design variable combinations and compare them. By comparing, the minimum pressure loss value P can be found. max , the corresponding design variable combination is d0, n0, D0, h0, and this combination is the optimal intake muffler design solution.

[0068] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for optimizing a low flow resistance intake muffler, characterized in that The following steps are involved: Step 1, selecting a bent perforated pipe muffler as a design optimization object; Step 2, measuring the noise characteristics of the engine intake system when the car accelerates suddenly, and determining the frequency band where the noise peak is located; Step 3, determining the target frequency where the transmission loss peak of the perforated tube muffler is located according to the frequency band where the noise peak is located; Step 4, according to the layout space of the engine compartment and the size of the air intake duct, set the structural parameters of the perforated pipe main pipe diameter, bending radius, bending diameter, muffler cavity diameter and cavity length; Step 5, calculate the best structural design scheme of the perforated muffler, determine the structural parameters of the main factors affecting the transmission loss of the muffler, the structural parameters of the perforation diameter d, the number of holes n, the distance D between the perforation center and the center line of the pipeline, and the perforation thickness h; The step 5 specifically comprises the following steps: Step (1) according to the structural parameters of the main factors affecting the transmission loss of the muffler, the value ranges of the four parameter design variables, namely, the diameter d, the number of holes n, the distance D between the perforation center and the center line of the pipe, and the perforation thickness h, a muffler sample data table is generated by the central composite design method in the response surface experimental design; Step (2) establishing three-dimensional models of all muffler samples using three-dimensional modeling software according to the parameters in the sample data table; Step (3) Use finite element acoustic analysis software to calculate the transmission loss of all muffler samples and obtain the frequency f at which the transmission loss peak is located. The calculation formula for the transmission loss is: Where TL is the transmission loss in dB, W in is the incident sound power at the entrance, in W, W out is the outlet radiated sound power, in W; Step (4) using fluid mechanics analysis software to calculate the pressure loss of all muffler samples under common working conditions; Step (5) takes the diameter d of the perforation, the number of holes n, the distance D between the center of the perforation and the center line of the pipeline, and the thickness h of the perforation as input variables, and takes the transmission loss peak frequency f as output variable, selects a second-order polynomial modeling method, and constructs a polynomial function to fit the sample space by solving the response surface polynomial coefficients, thereby establishing a response surface approximate model of the transmission loss peak frequency; Step (6) takes the diameter d of the perforation, the number of holes n, the distance D between the center of the perforation and the center line of the pipeline, and the thickness h of the perforation as input variables, and takes the pressure loss as the output variable, selects a second-order polynomial modeling method, and constructs a polynomial function to fit the sample space by solving the response surface polynomial coefficients, thereby establishing an approximate response surface model of pressure loss; Step (7) calculating all design variable combinations that meet the target frequency band according to the target frequency at which the transmission loss peak of the perforated tube muffler is located and the response surface approximation model; Step (8) substitutes all design variable combinations that meet the target frequency into the response surface approximation model of pressure loss, calculates the pressure loss of the silencers of all design variable combinations and compares them. The combination with the smallest pressure loss is the optimal intake silencer design.

2. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: The curved perforated pipe muffler in step 1 is composed of a curved main pipe with a plurality of through-holes and a muffler chamber.

3. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: In step 2, the third gear throttle opening 100% rapid acceleration is selected as a typical working condition to measure the noise characteristics of the intake system.

4. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: In step 5, the response surface analysis method is used to obtain the fitting function of the central frequency of the perforated muffler transmission loss and its influencing factors.

5. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: In step 5, the response surface analysis method is used to obtain the fitting function of the perforated muffler pressure loss and its influencing factors.

6. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: In step (5), the response surface approximate model function expression of the transmission loss peak frequency is: Among them, α0, α1, …, α 2N , α ij are the coefficients of each polynomial, X0, X1, …, X N , X i , X j are the variable factors, and N is the number of variable factors.

7. The method for optimizing a low flow resistance intake muffler according to claim 1, characterized in that: In step (6), the response surface approximate model function expression of pressure loss is: Among them, β0, β1, …, β 2N , β ij are the coefficients of each polynomial.

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