Development of numerical simulation techniques for performance improvement and noise reduction of hermetic refrigerant compressors

Thermodynamic efficiency improvement and noise reduction are two major goals in designing hermetic refrigeration compressors. Development of numerical techniques used to achieve these two goals is presented in this dissertation. The main topics of this thesis are refinement of compressor simulation techniques, development of vibro-acoustic analysis procedures to estimate radiated noise levels, and formulation of four pole parameters of three-dimensional cavities.; An advanced compressor simulation program should consider the effects of cylinder process and gas pulsations. However, it is known that simulation results from such a program tend to have difficulty converging. In this research, a new iteration scheme was developed to improve convergence of the simulation results. As an application, the simulation technique was applied to optimize the design of a discharge valve system.; A vibro-acoustic analysis procedure was developed using the finite element method and the boundary element method to calculate noise levels radiated from compressors. For the first time in compressor engineering, the noise level due to pulsating flows was able to be estimated by a purely numerical method. The procedure was also applied to predict sound levels of noise radiated from suction accumulators used in rotary compressors.; Four pole method is a very useful concept for computer simulation and vibro-acoustic analysis of compressors. The concept, originally developed for one-dimensional or lumped systems, was extended by Kim and Soedel (4) to systems that include three-dimensional acoustic elements. However, it was discovered during this research that their method was not entirely valid because of the singularity at source point. It was shown that this difficulty can be overcome by using the surface source model instead of the point source model that was used in the original method.