Research on Suppression of Airflow Secondary Noise in a Muffler Based on Large Eddy Simulation

Abstract

Based on the Large Eddy Simulation (LES), the problem of the performance of a muffler being weakened by the airflow secondary noise in the expansion chamber was analyzed. Based on the different relative positions of the inlet and outlet, a single-chamber muffler is divided into four structures and a numerical simulation model of the flow field is developed. The LES was used to analyze the flow field and secondary noise in the expansion chamber. First, the LES is used to calculate the unsteady flow in the expansion chamber to obtain the turbulent intensity and the pressure pulsation distribution of the flow in the muffler chamber. Subsequently, a simulation model of the acoustic field was built separately to obtain the secondary noise distribution of the flow in the muffler by computing the flow field information. It is shown that the secondary noise properties in the muffler are related to its geometrical configuration. The turbulence intensity of the flow field in the chamber can be reduced by changing the airflow pattern in the chamber, to weaken the intensity of the airflow secondary noise. Finally, a structural modification of the two-chamber muffler was performed based on the findings of the study, and the improved muffler performance was evaluated through numerical simulations and field tests. Experimental results show that the improved muffler has better acoustic properties and increases the noise reduction capacity by about 18 percent. It further confirms that the intensity of secondary noise can be substantially suppressed by changing the internal structure of the muffler, which opens up new ideas for the future design and modification of exhaust mufflers.