Unsteady characteristic and flow mechanism of a scroll compressor with novel discharge port for electric vehicle air conditioning

Abstract

• The transient characteristic and flow of the scroll compressor is studied using CFD. • Gas is under compressed in downside chamber and over compressed in upside chamber. • The pressure difference between the two chambers is caused by the discharge timing. • A novel discharge port is proposed to improve the compressor efficiency by 2.4%. • The largest pressure unbalance between the upside and downside chambers reduces 50%. Scroll compressor is a key component of the air conditioner/heat pump system in electric vehicle. This paper focuses on the impacts of discharge port design on the transient performance and flow mechanism of the scroll compressor. A three-dimensional unsteady computational fluid dynamic model is established and validated. The computational domain includes inlet duct, scroll working chamber, discharge port, check valve, plenum chamber and outlet duct. R134a is used as the working fluid. The impacts of the position of the conventional circular port on the transient characteristic and flow loss mechanism of the scroll compressor are studied. It is found that large pressure difference between the two central chambers is resulted from discharging time difference of the two chambers. It inevitably leads to under compression in downside chamber and over compression in the upside chamber at designed condition. The conventional circular discharge port cannot address this problem. Therefore, a novel discharge port with a tail is proposed to retard the discharge time of the downside chamber and advance that of the upside chamber. It is found that the isentropic efficiency of the scroll compressor is improved by 2.4%. The maximum pressure unbalance between the upside chamber and downside chamber is reduced by 50%.