Abstract:

In order to increase the driving range of electric vehicles, the operating performances of the air conditioning system under variable conditions and the functional characteristics of the scroll compressor were investigated. The performance prediction model of a trans-critical CO₂ heat pump air conditioning system coupled with a one-dimensional flow model of a scroll compressor was constructed, and the validity of the model was verified by experimental data. The differences in system performance prediction under variable operating conditions between the simplified compressor model the and one-dimensional flow model were compared, and the variation characteristics of the suction pre-compression and the asymmetric flow in the discharge process were analyzed. The results show that with a constant efficiency, the system operating characteristics index (the ratio of the system cooling capacity to the compressor power consumption) predicted by the simple compressor model, is up to 20% higher than that by the one-dimensional flow model. The compressor suction vacuum degree is the main factor affecting the degree of suction pre-compression. As the compressor speed increases from 2 500 r/min to 6 000 r/min, the degree of suction pre-compression increases by 1.92%, and the volume efficiency increases by 4.72%. The change in the throughflow area of the discharge port dominates the asymmetric pressure distribution in the discharge chamber. The reduction of the asymmetric degree of the discharge chamber pressure is beneficial to improve the compressor isentropic efficiency.

Key words: electric vehicles, driving range, CO₂ air-conditioners, scroll compressors, operating characteristics, throughflow model