Gas path sound transmission in spherically-shaped reciprocating compressors: Theory and experiment

Gas pulsations within the refrigerant gas cavity is one of the the principa l noise propagating paths in reciprocating compressors. This paper provide a physical insight to the relationship between the gas pulsations inside th e cavity and noise radiation of reciprocating compressors. The refrigerant gas cavity of the rest compressor is modeled as a space between concentric spherical shells and analyzed with modal expansion techniques. Gas pulsatio ns within the cavity are mathematically represented as the forcing terms of the inhomogeneous wave equation in spherical coordinates. The pressure dis tribution inside the cavity is then estimated accordingly. Based on the ort hogonality principles, the noise radiation patterns associated with the gas pulsations are predicted. Acoustic modal analysis, directivity rest and ru nning speed sensitivity test are conducted to identify the acoustic charact eristics of cavity and to verify the analytical model. The experimental res ults are in good agreement with the prediction of the analytical model. Thu s, the concentric, spherical shell model well describes the acoustic charac teristics of cavity within the test compressor. This model can also be empl oyed as a design tool to analyze the effects of system parameter variation on overall noise radiation.