Performance Analysis And Experimental Study On Foam Aluminum Muffler In Round Tube

At the time of reducing exhaust noise, the exhaust muffler installed on modern motor vehicles often causes airflow regeneration noise and evokes the increasing of backpressure of the engine exhaust system which will increase engine power loss. New structures and new materials are applied to the design of muffler to solve the problems. Aluminum foam is a new type of material which is developed in recent years. As a lightweight material with high strength characteristics and as functional materials with physical properties such as porous, vibration, damping and absorption, the material of aluminum foam is widely used in general industry and high technology. This thesis applies the material of aluminum foam to the muffler structure and constitutes the muffler with aluminum foam, explores the application of aluminum foam on the silencer, provides evidence for the application of the muffler with this new material in the industry.This issue designs a new structure of the muffler with the application of the pipe made of aluminum foam, analyzes the acoustic field simulation, flow simulation and experimental performance, and studies the acoustic performance and aerodynamic performance. First, the acoustic performance of the muffler is analyzed, the interior sound field of the muffler is modeled and meshed in the ANSYS, then imported into SYSNOISE, imposed reasonable boundary conditions to carry out the analysis of acoustic performance of the muffler. The results shows that, compared to reactive muffler, the muffler with aluminum foam has a higher amount of noise reduction and a wider frequency band in middle and high frequency. Second, taking the aluminum foam muffler for instance, the flow field of the muffler has been analyzed by numerical simulation, the result of the simulation clearly reflects the flow field after setting the parameters of the aluminum foam and the boundary conditions of the model. Compared with the muffler without the aluminum foam, the use of aluminum foam can reduce the pressure loss effectively and make the distribution of the air become more uniform, which will improve the overall performance of the muffler.Finally, using the feature of foam aluminum which has an advantage of noise elimination at high frequency, experimental research on muffler of foam aluminum is carried out. The acoustic and Aerodynamic performance is measured in both static and dynamic conditions, which means the centrifugal fan is open or not. The results show that in static condition, compared with the muffler without foam aluminum, noise reduction of the muffler with foam aluminum in the high frequency region can reach 30dB and broaden the frequency bandwidth. In dynamic condition, the regeneration noise is suppressed at high frequency, meanwhile the foam aluminum can reduce the pressure loss effectively which will improve the overall performance of the muffler.