Dynamic optimization design of air compressor muffler for air compressor

Wenhong Zhijun is widely used in various sectors of the national economy. But the noise it produces at work seriously affects people. How to economically and effectively reduce the noise of the air compressor, the existing air intake muffler is optimized to solve the actual problem of the air compressor noise exceeding the standard.

Air compressors are widely used in various fields of industrial production as air compressors. Air compressors are mechanical devices that compress gas to increase its pressure to more than two atmospheres and then to a gas container or other equipment. , is a general-purpose device. The air compressor is a comprehensive noise source. The noise generated during the compression process is mainly derived from the aerodynamic noise, mechanical noise and electromagnetic noise of the intake and exhaust ports. Intake noise, during the operation of the air compressor, the cylinder intake valve alternately opens and closes, the air is intermittently sucked into the cylinder, and sound waves formed in the form of pulsation changes are radiated from the air inlet. Mechanical noise, the air compressor is in operation, the sound generated by the intake valve is closed, the impact sound in the crank-link system and the frictional vibration of the piston wall when the piston reciprocates, and the sound and vibration waves when the acoustic piston compresses the air. Mechanical noise is formed. Motor noise exhaust and air bag noise, motor noise mainly includes cooling fan noise and mechanical noise when the bearing rotates. The compressed gas in the air compressor is intermittently discharged into the air bag as the exhaust valve is opened and closed. Sound is generated when the exhaust valve and the pipe are generated to form exhaust noise. The compressed air entering the air bag is mixed with the air in the bag to generate resonance, and is radiated through the air bag and the connected pipe to form noise.

Analysis of existing noise reduction measures for air compressors In the air compressor noise control, different noise sources have different treatment methods for similar noise sources, and the schemes adopted are different according to the geographical location and standard requirements. In foreign countries, Japan, the United States, etc., most of the air compressors use sound insulation cover and muffler measures.

The noise reduction of the air compressor is to reduce the noise from the structure of the air compressor itself. For most reciprocating air compressors, from the current technical level, only active noise reduction can hardly achieve the desired effect. The mechanism of noise determined by its working principle is mainly caused by pressure pulsation, which is aerodynamic noise, which is higher than mechanical noise electromagnetic noise. For example, passive reciprocating air compressors are passively silenced. Sound absorption and noise reduction and vibration reduction are effective in installing the muffler for the dynamic noise of the air compressor.

The muffler is a kind of noise reduction device that prevents sound propagation and allows airflow to pass. It is the main technical measure to control airflow noise. In the development of muffler, the first one is the passive muffler, that is, the resistive muffler resistant muffler and the impedance compound muffler. With the continuous maturity of technology, passive muffler has achieved better sound-absorbing effects, especially in the increasingly strict emission regulations and noise regulations. In order to improve most of China's noise emissions, the noise is not up to the requirements, and the noise is higher than that of similar foreign models. A variety of muffler has been developed in China, and good noise reduction has been achieved. In recent years, with the development of modern digital signal processing technology and the improvement of the performance cost ratio of electronic control devices, the concept of active muffler has been proposed internationally. Optimization design of air compressor muffler The optimal design of muffler is a complex optimization process with multivariable, multi-constrained and multi-objective. In the optimization process, it is necessary to continuously select the plan and select optimization parameters. Based on the above two points, the computational process of optimizing the design will be a computationally intensive and complex process. Computer-aided design is the best way to solve this problem. The optimized design of the muffler needs to comprehensively consider the aerodynamic performance and structural performance of the acoustic performance, and finally give the optimal parameters of a certain structure of the muffler. Solving these problems with a computer will inevitably require us to establish an appropriate mathematical model, give the constraints, and then solve the problem to give the final result.

The structure of the muffler is varied and the parameters are varied. The basic structure of the muffler must be given before the optimization design. The structure type can be determined by reference to the original or similar muffler, and then modified according to the specific requirements. We can choose a variety of structural types, the muffler of each type of structure as a solution, through calculation to determine the feasibility of this program. Each muffler can have a variety of structural parameters. We can't optimize all the parameters. We can only select some structural parameters that have obvious influence on the performance of the muffler as optimization variables according to the actual requirements. According to the structure size of the muffler. , the range of these parameters is limited, and the optimal parameters are finally selected by calculation.

3.1 Air compressor inlet muffler optimization design of the objective function muffler optimization objective function selection needs to comprehensively consider the two aspects of muffler performance evaluation, the muffler with larger muffler quantity must require more muffler cavity, expansion ratio is large, The large length and complicated structure will inevitably increase the resistance loss of the muffler, and at the same time, the structural performance will be deteriorated. Therefore, the design of the muffler must take into consideration both of these aspects. In general, a muffler with good performance is in progress. In the whole frequency range of the air noise, there should be sufficient noise reduction, the resistance loss is small, the high temperature and corrosion resistant muffler has the same dimensions and the whole machine, the structure is simple, the process is good, the cost is low, the noise is reduced, the maximum pressure loss is minimum 3.2 The initial condition of the optimized design 1 Formulating the new muffler's muffling frequency characteristics Initial conditions According to the requirements of the existing muffler on the muffling frequency characteristics, it is proposed to define the muffling frequency characteristic of the design muffler as the segment low frequency muffling peak frequency = 500, and the middle and low frequency muffling peak frequency 51200 , medium and high frequency noise reduction 3.2.1 low frequency noise reduction peak frequency = 5001 by the resonance type with perforated tube

3.2.2 Middle and low frequency muffling peak frequency, 201 The basic parameters of the interpolated two-stage expansion muffler are provided by the interpolated two-stage expansion muffler substructure, and the initial range of the selected parameters is obtained from the muffling amount and the muffling frequency characteristic. For the work, the structural parameters of the Dingding I interpolated two-stage expansion muffler 323, the high-frequency muffling peak frequency of 2000 is provided by the resistive sound-absorbing muffler substructure to meet the muffling performance of the intermediate frequency band, and the resistive sound absorption is proposed. The anechoic structure eliminates 2000 of his 4000 high-frequency noise. According to the actual situation, the design of the anechoic structure should have a silencing volume of 40 decibels per meter. When setting up this kind of muffler, you must first consider the limitations of both aspects.

The aspect is the frequency limitation, and the frequency range that can effectively silence is roughly coordinated with the effective sound absorption range. Resonant sound absorption structure is difficult to complete high frequency sound absorption performance, so it should not be used.

The porous sound absorbing material layer has good sound absorbing performance in the middle and high frequency range, and should be preferably used. Moreover, the sound absorbing performance of the sound absorbing material layer can be expanded toward the low frequency direction due to an increase in the thickness of the material.

From the above, it can be seen that the muffler is optimized from the original single-interpolation expansion structure to a double-interpolation expansion structure, which not only can widen the effective noise reduction band, but also effectively reduce the ripple noise. When the single cavity of the original muffler is doubled as the thickness of the sound absorbing material layer, the effective sound absorption range is shifted slightly to the low frequency direction by an octave. This can not only effectively reduce the noise in the middle and high frequency bands, but also compensate for the insufficient sound absorption performance of the intermediate frequency band. Another limitation comes from the geometric size, which is a concentric circular muffler. When the length is timed, it has a higher noise reduction and should choose a smaller channel width. However, the sound absorption structure of the mountain occupies a given cross-sectional area, so the smaller the channel width, the smaller the proportion of the effective section of the channel in the summary surface. If the cross-sectional area of ​​the channel remains constant, the overall cross-section of the muffler will be larger, which cannot be limited by objective conditions.

The initial conditions for the pressure loss of the new muffler are determined. Under the premise of satisfying the muffling amount, the pressure loss is as small as possible. The initial condition for taking the pressure loss is preferably no more than 5 of the current muffler pressure loss.

3.3 Air compressor inlet muffler optimization design steps The air compressor inlet muffler optimization design steps are summarized as follows: 3.3.1 According to the actual conditions, the muffler form and the muffler pressure loss frequency muffling characteristics are the objective function; 2 selected The parameters of the main pipe of the muffler system, the sound velocity and other parameters of the given gas temperature; 3 Determine the volume of the muffler according to the volume ratio of the muffler and the gas flow; 4Select the series of muffling structures; 5 pairs of muffling structures, select the series of geometric parameters; 6 pairs Group given geometric parameters, muffler muff performance calculation; 7 muffler pressure loss calculation for the data; 8 take another set of data, repeat 6070 lines of procedures; 9 for a given muffler structure, preferably the best set of geometric parameters; 10 For the other muffler structure, repeat the 5090 line program; the best muffler structure and the corresponding optimal geometric parameters are preferred.

The multi-objective genetic algorithm is used to optimize the air compressor air inlet muffler. The general mathematical calculation software is used to program the genetic toolbox developed by the University of Sheffield, UK, to realize the multi-objective genetic algorithm to optimize the air compressor air inlet muffler. The basic parameters of the multi-objective genetic algorithm are set in the program. Each objective function has a corresponding end pole determination. Taking the interpolated two-stage expansion muffler substructure as an example, the program is used to optimize its structure. The number of individuals in the selected population is 0=100; the largest genetic algebra is selected as GEN=50; the mutation rate is selected as INP=0.05; the real-value coding is used for optimization, and the optimization curve of typical parameters is 2.

Optimized to double resonant cavity, this not only increases the sound absorption peak of each frequency band, but also increases the noise reduction amount in each adjacent frequency band. By optimizing the main pipeline parameters, the pressure loss can be effectively reduced. Optimizing the structural parameters will reduce the muffler. Manufacturing costs.

At present, the society is increasingly demanding low-noise products. Whether it is mechanical and electrical products or household appliances, the level of noise has become the evaluation standard for people's quality. Therefore, in the near future, more and more low-noise products will come out to meet people's requirements. For high-noise products, for some reasons, in the production process can not make the noise to a range that people can afford, then still need to design a variety of muffler for noise reduction. The optimized design method will still be used in the design method. This is because the optimization method is relatively simple and accurate in mechanical design, and can meet a variety of requirements.

Sun Guozheng Yu Yuqing optimizes design and application, People's Education Press, 2000 Zhong Shaohua, etc., research on muffler optimization design and performance analysis method, internal combustion engine engineering, 2005 Ma Baoli, etc. Dynamic optimization design of muffler, noise and vibration control, 2004 4 Noise control technology for large-scale outdoor air compressors, environmental pollution control technology and equipment, 2005 author unit Hunan Puzhao Information Materials Co., Ltd. 142 pages due to the wavelength of the neutrons we take, the diffraction will only be in the seam The width direction is generated in the 7-axis direction. If the screen distance and the diffraction angle 1 are fixed, the relative intensity 1 is only a function of the diffraction angle 0.

From the above derivation and its results, we can see that the relative intensity 1 is a coordinate function. In the calculation. The relevant parameters are taken as the neutron mass from =67,7, and the two-sided evolution equation 2324 is about the sum and superposition function. It is found that when 600, the time-consuming function reaches the platform area, so we take n=600, m= 10. Document 4 details the cold neutron single slit diffraction experiment. We input the same parameters as the experiment. The width of the single slit is the neutron wavelength, and the distance between the slit and the diffraction screen is 25 to obtain the theoretically calculated diffraction theory curve.

3 is the theoretical result and the experimental comparison of the solid line for the theoretical calculation results, the dot is the experimental data, we take the parameter = 5.87 10 from 3 can be seen from 3, to 300, the calculation results are in good agreement with the experimental data.

According to comparison.

The solid line is the theoretical calculation result, and the dot is the class of the experimental data in the literature 4.

Theoretical physics research.

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