Application of an extended two-dimensional inverse method in turbine volute design

Nozzleless housings for turbocharger turbines accelerate and guide flow into downstream rotors. Their design affects the aerodynamic performance and reliability of the turbines. Due to the three-dimensional nature of the volute of the housings, turbine housing volute design is largely based on extended 1D theories and trial-and-error method. In this paper, a detailed description of an extended two-dimensional theory for volute design is given, including its numerical implementation. The method is then applied to design a twin-entry turbine housing for a turbocharger turbine under both equal and unequal admissions, to replace a highly optimized, manually designed housing. The results show that the new volute achieves the same turbine aerodynamic performance as the manually optimized volute with greatly reduced design time, and it also generates more uniform rotor inlet condition with lower pressure excitation force. A breakdown of the stage loss shows that the loss in the new volute housing is larger than that in the manual housing due to its smaller overall dimensions, but the losses inside rotor and downstream diffuser are both reduced due to the more uniform volute exit flow. A discussion on the secondary flow in the two volutes is carried out to show how the volute geometry, through influencing the radial discharge from the volute exit, affects this flow. A further discussion on the flow angle jump around the tongue is placed at the end of the paper to show the mechanism of this jump, how to control it in volute design, and to offer a way forward to improve the volute design method.