Numerical simulation and optimized design of water-cooled volute for turbine-based air compressor used in automotive fuel cells

Abstract

Water-cooled components of air compressor provide a feasible way to improve the performance of automotive fuel cells. Due to the large heat generation during air compression, the efficiency of air compressor is normally not easily enhanced. To recover power and prevent excessive gas temperature, this paper has proposed an optimized water-cooled volute for the turbine-based air compressor used for automotive fuel cells. Firstly, a three-dimensional numerical model of the volute integrated with impeller has been developed, upon comparison with the measured isentropic efficiency and pressure ratio, the mean absolute errors were found to be 0.0669 and 0.0117, respectively. Then, a closed flow passage on the volute outer wall is constructed to form an initial water-cooled volute structure. Numerical simulation analysis is then conducted on the initial water-cooled volute under different cooling water inlet conditions. The Box-Behnken method is used to generate the design space for the water-cooled volute structure, and a response surface model is fitted using a second-order function. The response surface model is then used as the objective function of multi-objective genetic algorithm to perform global optimization and generate the Pareto front. The combinations of parameters for the water-cooled volute structures are determined from the optimal solution set. The results showed that the isentropic efficiency of the optimized water-cooled volute was improved by 12.43 % compared to the original volute, and the outlet gas temperature was reduced by 1.29 % compared to the initial water-cooled volute. The proposed water-cooled volute and its design method can enhance the overall performance of the air compressor for automotive fuel cells.