An investigation of the effects of volute A/R distribution on radial turbine performance

In order to meet the higher design requirements of radial turbines, it is necessary to clearly understand the impact of different design parameters on turbine performance. The A/R distribution is one of the most important design parameters for the radial turbine volute, but there are few studies on it. To clarify the effect of A/R distribution on turbine efficiency and blade excitation force, a detailed comparative study is carried out. An experimentally validated numerical method is used, and steady and unsteady CFD simulations are conducted in this study. The results show that the volute A/R distribution has a significant effect on the turbine efficiency, while a linear distribution can provide a more uniform inlet condition and thus improve the rotor efficiency. The flow parameters fluctuated significantly at the volute tongue. Although the efficiency is not sensitive to this fluctuation, it directly affects the excitation force on the rotor blades. The volute with S-shaped A/R distribution produces the smallest excitation force due to the smallest fluctuation. Two new A/R distributions are presented which combine the advantages of linear and S-shaped or convex A/R distributions with high efficiency and low excitation force. It is suggested that the A/R should be close to the linear distribution and decreases rapidly before the tongue.