Performance Numerical Simulation And Optimization For Car Muffler

Facing the austere crisis of energy sources, economizing energy and decreasing emission is one of the most important thing we should do to carry out scientific development view and construct a harmonious society. With the automobile manufactures'coming to China, independent innovation is the motivity for China to implement sustainable development.Muffler–which is the most important part to reduce vehicle noise, how to decreasing noise taking account of reducing energy waste which is a new research after auto development.Foreign auto manufactures have accumulated mass databases, so they could design a new style muffler in a short time, but most auto mufflers in China mainly rely on foreign company's technology. The core technology and intellectual property are controlled by foreign company. This causes that the domestic enterprises can not design and produce muffler autonomously. This paper is based on the National"863"to study the Muffler's acoustic performance and there-dimensional flow analysis, give optimization scheme. The aim of this paper is to do some preparatory work for the establishment of muffler autonomous design theory and method. This paper improved the test bench which was built according to the national standard"GB/T4760-1995 acoustics-- measurement procedure for silencers". Two fans worked in series to fulfil the experiment. In aspect of acoustic and pressure drop measuring, accurate dates resulted from less airflow and human influence.The experiment processes are as follows:1)Valve positions'calibration: After the installation of muffler, the fans should be opened, it was the time to calibrate the valve position and measure pressure drop relative to different airflow velocity.2)Sensor'calibration: According to the national standard, sensor should be calibrated.3)After the installation of the muffler, sound should be opened, then the sound pressure could be measured to the premise the sound sensor achieve testing standard through adjusting the power amplify.4)Sensor'calibration: According to the national standard, sensor should be calibrated.5)After the installation of the muffler, valve was placed at the biggest position, sound should be opened, then the sound pressure could be measured to the premise the sound sensor achieve testing standard through adjusting the power amplify.6)The sound pressure could be measured by adjusting the valve's position relative to different airflow velocity, it was the same job as step 4 and 5.In the experiment the static and dynamic Muffler transmission was measured, It showed that the Muffler's performance was in the downward trend along with the air velocity changing, it was resulted from renewable noise impact. The pressure losses were measured, It showed that the Muffler's pressure losses were in the upward trend along with the air velocity changing.The Muffler shell is so complex that it must be establishment in three-dimensional software in the premise of without affecting sound field analysis, then the closed shell was converted to STL format, the internal components were added in GT-Muffler of the pre-presser software of GT-power. The muffler should be dispersed in suitable length in order to be used in GT-suite, after the numeration in Suite with its internal transmission loss module, the results could be deal in GT-POST.Through simulation results and experimental results of comparative analysis verified the accuracy of model muffler. Full preparations had been done for the further optimize the structure of the analysis.After the establishment of three-dimensional flow field simulation model, the calculation could be carried out by a large-scale CFD software Fire with the boundary conditions, the results were certified by the pressure loss. It showed that the numeration and experiment were in good agreement. The paper also discussed the conditions under different air flow velocities, it showed that the upward trend of the pressure loss and renewable noise, gived good explanation to the experiment. Through the analysis of acoustic and flow of prototype middle and rear muffler, according to acoustic four-terminal network theory, muffler could be decomposed into a number of sub-four-terminal network series, then the optimum was confirmed. Through the same boundary conditions the sound field and flow field simulation analysis, optimization model would be compared with the prototype, the results showed that the performance of the optimization Muffler and pressure losses, optimized to meet requirements.The method of using four-terminal network to analyse various aspects muffler will be able to conclude a muffler design's key-point, and the combination of the sound field and fluid analysis will make great sense in muffler design. This paper only gives one optimum, it hopes that through the process of optimum can pave a way to the muffler's design.