Design Of The Suction Muffler Of A Reciprocating Compressor

The suction muffler of a reciprocating compressor is used for reducing a noise produced by pressure pulsations. According to the shape, the suction muffler is classified into one-chamber type, two-chamber type, Helmholtz-resonator type, pipe-resonator type, and so on. These mufflers are used according to the characteristics of the frequency of compressor noise. In this study, four pole parameters have been used for calculating Transmission Loss of the muffler, and Insertion Loss has been acquired for the optimum design of a muffler by the experiment. NOMENCLATURE p : Acoustic Pressure [Pa] c : Speed of Sound [m/s] v : Mass Velocity [kg/s] TL : Transmission Loss ρ : Density of Refrigerant [kg/m] IL : Insertion Loss INTRODUCTION The pressure pulsation generated at the suction and discharge port of reciprocating compressor is the main cause of a noise and vibration. In addition, it has relation to generation of a flow-induced noise and compressor performance. Therefore, many researches on suction muffler have been carried out in view of noise reduction as well as flow performance. According to the characteristics of the noises, either one-chamber type suction muffler or two-chamber type suction muffler can be used for reducing a noise of a reciprocating compressor. Also, Helmholtz resonator can be inserted to a suction muffler. In this case, noise can be reduced so much in a local frequency band, but the width of the band is too narrow to reduce the noise totally with varying temperature of the refrigerant. On the other hand, it is reported that a suction muffler with a pipe resonator can reduce noises efficiently in a broad frequency band. In this study, Transmission Loss (TL), one of the performance parameters for muffler, is calculated using four pole parameters. Another performance parameter, that is, Insertion Loss (IL) is obtained by experiment and one-chamber type suction muffler is compared with two-chamber type suction muffler and pipe-resonator type suction muffler on the characteristics of the noise reduction. SUCTION MUFFLER MODELING Transmission Loss TL (Transmission Loss), one of the performance parameters for a muffler, can be calculated by transfer matrix. State variables for the transfer matrix are acoustic pressure and mass velocity. It is assumed that plane wave propagates to the exclusion of higher modes or three-dimensional waves. Indeed, the suction muffler of a reciprocating compressor is too small to allow propagation except plane waves at the frequencies of interest. In the end, an overall transfer matrix can be defined, in spite of the existence of three-dimensional waves in the suction muffler. The overall transfer matrix relation can be written as             =      