Noise Reduction of Muffler by Optimum Design

Soo, Yi Kang (2020) Noise Reduction of Muffler by Optimum Design. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Exhaust noise from internal combustion engine is one of the factor which causing the noise pollution to the environment. Therefore, muffler is design used to attenuate sound that generated from the engine. Muffler is the most important part of the exhaust system. Sound is a kind of pressure wave that generated during the alternating of pluses of the high and low pressure air. Increase in engine rpm will also lead to increase of pressure pulses. Therefore, sound will be emitted at higher frequencies. The theory of muffler in attenuating sound is that muffler is designed to dampen the high intensity pressure wave that generated during the combustion process in the internal combustion engine. Muffler will only restrict the transmission of noise but it has to serve in the way to let the passage of exhaust gas out from the muffler. Design of muffler is a very complex function as different design will affects the attenuation sound capability, emission of exhaust gas and the fuel efficiency of the internal combustion engine. In this project, the performance of combination muffler was analyzed in term of transmission loss and backpressure generated by using FEA. Literature review have shown that in the journal, the parameters of the combination muffler, diameter of muffler, length of muffler, length of reactive chamber, length of reactive muffler part, diameter of inner pipe, length of absorptive muffler part and design of inlet and outlet pipe diameter, length of the extended inlet and outlet tubes, tail-pipe length, diameter of the holes and pitch length can be calculated using formula but inner pipe length of the combination muffler cannot be calculated using formula but with the range between 60mm to 90mm. Hence in this project, all the parameters to design the combination muffler were calculated so that optimum performance of muffler can be obtained. Solidworks CAD software will be the tools to design the combination muffler. 50mm, 60mm, 65mm, 70mm, 80mm and 90mm inner pipe length are tested and simulated to achieve the best design of combination muffler. The results show that 60mm inner pipe length is the best design with maximum and average transmission loss of 44.57dB and 16.02dB respectively. This combination muffler design achieve maximum of 41.6% transmission loss at 1500Hz.