Numerical modeling of noise and vibration due to discharge in hermetic compressors

The pulsive and intermittent nature of the operation of a hermetic refrigeration compressor leads to the generation of noise and vibration during the operation. Specifically, in hermetic compressors, gas pulsation induced by refrigerant discharge is a major source of NVH effects. The generation of noise and vibration due to refrigerant gas discharge is a process that involves thermo-mechanical operation within compressor cylinder, cavity acoustic resonance, valve opening/closing, hermetic shell vibration, and exterior sound radiation. In the presented study, a numerical simulation model was developed to address the multi-physical process of noise generation due to refrigerant gas discharge. The thermodynamics aspects of the compression process and the vibro-acoustics aspects are coupled together. The thermo-mechanical submodel is based on a compressor mechanistic model based on control volume analysis with lumped parameters. The vibro-acoustics submodel is based on finite element analysis, and it describes the two-way coupled interaction of compressor cavity acoustic resonances and hermetic shell vibration. Meanwhile, the acoustics response in the cavity is coupled with the thermodynamics submodel through proper modeling dynamics of discharge valves. Numerical simulations were conducted to demonstrate how simulation models work and how they can potentially help compressor manufacturers to gain a better understanding of the physical reasons behind NVH effects of compressors.