Analysis Of Muffling Performance Of Automobile Exhaust Muffler Under Flow And No Flow Condition

The rapid development of automobile industry has brought people more convenience,while the noise pollution caused by its emissions has attracted more attention.Exhaust muffler is used to reduce noise,so the analysis of its muffling performance has always been the focus of research.A complex multi-cavity resistant muffler is taken as the research object.Muffle performance in both flow and no flow conditions is analyzed.In the no flow condition,one-dimensional GT-POWER and three-dimensional finite element Virtual.lab is used to simulate the transmission loss of muffler,the simulation is verified by two load test methods.The advantages and limitations of the two different simulation methods are analyzed.The effect of perforation apertures on Transmission loss is studied.Summarize the rule and optimize.The influence of airflow velocities on the acoustic performance of muffler is studied under flow condition and the airflow regeneration noise was also studied.Before studying the regenerative noise of muffler airflow,the simulation model of muffler inner flow field is established to analyze the flow field.The actual back pressure of muffler is measured by cold flow bench,and the validity of the simulation is verified by comparing the simulation and measurement values.Based on the aero-acoustic theory and the analysis of the flow field information,the airflow regenerative noise source distributed in the muffler is preliminarily predicted.For the research of muffler airflow regeneration noise,we choose three methods: broadband noise model,FW-H acoustic analog method and co-simulation.Firstly,we use the Proudman broadband noise model and the Curle noise model to analyze the distribution of quadrupole and dipole sound sources in the muffler to verify the effectiveness of our prediction mechanism.Study the effect of changing the diameter of the intake pipe and the outlet pipe on the intensity of the dipole and quadrupole sound source in the muffler and propose optimization suggestions,compare the dipole and quadrupole sound source intensities before and after optimization.Then FW-H acoustic analogy method and joint simulation method are used to obtain the spectrum of airflow regenerated noise to verify the effectiveness of the optimization opinion.Finally,the differences of the above three methods are compared and analyzed.This paper summarizes the optimization mechanism of air regeneration noise by comparing the flow field information before and after optimization.