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Automotive air conditioning compressors induce pressure pulsations into the refrigerant system during their operation. These pressure pulsations are transmitted through the refrigerant system on both discharge and suction sides of the compressor. As these pulsations travel through the evaporator in the vehicle air handling system, undesired compressor noise can be generated inside the vehicle. It is important to minimize these pulsations at the compressor source in order to improve vehicle refrigerant system sound quality and meet customer requirements. This paper provides an analysis of measured NVH (pressure pulsation) data and a development of CAE models used to understand the characteristics of pressure pulsations generated by an automotive compressor. It explains factors which influence the magnitude and frequency of the pulsations in order to minimize their effects in the refrigerant system with regard to sound perceived in passenger compartment of the vehicle.

In the refrigerant circuit of an automotive air-conditioning system, oil is needed to lubricate the moving parts of the compressor. However, it is desired to limit the presence of oil within the compressor, avoiding its flow to the areas of heat exchangers (like evaporator and condenser), in order to improve the efficiency of the heat transfer process. The oil separation is done immediately downstream of the compressor in a device using either impinging or centrifugal effects on the refrigerant carrier gas flow. The oil phase is assumed to exist as a secondary phase in the form of droplets. The main requirement for a good design of an oil separator device is to achieve the maximum liquid separation with the smallest pressure drop for the gas flow. The numerical simulations were performed using Eulerian Multiphase model and Mixture model of FLUENT6 on fully unstructured tetrahedral meshes of various design iterations of the separator.