Numerical Investigation on the Characteristics of Vapor Injection of Scroll Compressor for Electric Vehicle

To investigate the vapor injection performance of a scroll compressor with a short profile, a three-dimensional transient numerical model of a vapor-injection scroll compressor for an electric vehicle with a displacement of 38 cm³/r is established and verified with deviations within 9.5%. We investigated the effects of the pressure and temperature of vapor injection on the performance of the scroll compressor using the model. The results show that under the condition of a constant superheat, with an increase in injection pressure, the discharge temperature of the compressor initially decreases and then gradually increases. Moreover, the heating capacity exhibits an increasing trend, with the maximum increase in heating capacity reaching 20.5% and 17.1% at rotary speeds of 5000 and 6000 r/min, respectively. In addition, the heating coefficient of performance (COP) increases during the first stage and then decreases. Moreover, the maximum values of the heating COP with vapor injection at the former speeds were 3.9% and 2.3% higher than those without vapor injection, respectively. The compressor efficiency exhibits the same tendency as the heating COP, and the volumetric efficiency gradually decreases. The compressor discharge temperature increases slightly with constant injection pressure, whereas the compressor power, heating capacity, and heating COP remain almost constant as the injection temperature increases. Compared with the injection temperature, the injection pressure has a significant impact on the scroll compressor.