Enhancing heat dissipation to improve efficiency of two-stage electric air compressor for fuel cell vehicle

The electric air compressor is the most energy-consuming auxiliary component in the PEMFC (Proton Exchange Membrane Fuel Cell), and its power consumption accounts for more than 80% of the PEMFC parasitic power. Improving the efficiency of electric air compressor is of great significance to energy saving of the PEMFC. In this study, the numerical equation of the internal flow channel of the TSEAC (Two-stage Electric Air Compressor) was established. The validity of the numerical equation was verified by the experimental study. It is found that the heat generated by the electric air compressor for the PEMFC is 2-4 times higher than that of the turbocharger for a traditional diesel engine. Besides, the temperature-rising characteristics of gas in the inner flow passage of the TSEAC are analyzed. Under its normal working conditions, the temperature rise of gas passing through impeller and diffuser reaches the maximum of 33.97 K and 48.95 K, respectively. Higher temperatures cause gas to be heated and expand more, thus increasing the compression power of compressed gas consumed, and the efficiency of the TSEAC is reduced. The theoretical compression power of the TSEAC with cooling compression process is calculated. It is concluded that shell cooling can reduce the export of first and second level compression stress and the second level compression inlet temperature. Under constant inlet pressure and temperature, shell cooling can reduce the internal power consumption of the TSEAC. In order to verify the feasibility of this study, the thermal conductivity of the TSEAC shell was increased from 273W/(m.K) to 397W/(m.K) and 524W/(m.K), the outlet temperature was decreased by 7.5 K and 12 K, and the maximum efficiency was increased by 1.3% and 2.4%, respectively.