Research And Software Development Of Optimal Design Of Automobile Exhaust Muffler Based On Genetic Algorithm

With　the　rapid　development　of　high-speed　vehicle,　vehicle　outer　noise　pollution　have　become　global　problem.　The　exhaust　noise　is　one　of　the　main　sources　vehicle　outer　noise.　The　exhaust　muffler　is　the　chief　and　effective　device　to　control　exhaust　noise.　Firstly, the influence of the linear temperature and the average speed of airflow on sound transmission performance was discussed, the six sound field transmission matrixes for silencing elements usually used in mufflers was established on this basis. Regarded engine , exhaust pipe and silencer as a exhaust system of exhausting, the mathematical model for calculation the insertion loss in a muffler is presented. As an optimal method , Genetic Algorithm has obvious advantages which is based on the nature selection and genetic transmission mechanisms , such as high collateral, stochastic, self-reliance. The basic theory of the normal Genetic Algorithm was introduced in brief. Genetic Algorithm has problem of premature convergence and result swing near optimum value. To solve the problem of premature , the method called Monte-Carlo was adopted to prevent the algorithm from local optimal, and to the problem of result swing , the method changing the hunting zone dynamically was proposed to improve the accuracy of the optimal result. Float encoding method combined with the normal Genetic Algorithm, and the advanced Genetic Algorithm of float encoding was brought. Further more, MATLAB language was used to devises genetic algorithm programs to optimize the test functions of two famous optimal methods. The test results indicated that the improved Genetic Algorithms of float encoding was valid, which can not only avoid local optimal but also improve the accuracy of the optimal result. Secondly, the characteristic calculation of the silencer performance and optimization software has been designed, its programming realization based on VB and float encoding. The modular program and data-base managed technology were used in the software, so it has convenience to extend the program, and it has the common character at the same time. Finally, the software is used in the characteristic calculation of the performance of the muffler used in a saloon car. In order to combine the theory analysis with experimental study and realizing the optimal design of mufflers, a muffler experimental device is built up, and the transfer properties of single cavity exhaust silencer were simulated using ANSYS7.0. The results of decreasing exhaust noise of the muffler indicated that the research has theoretical and practical value significantly in this paper.