Design and Flow Analysis of Radial and Mixed Flow Turbine Volutes

Radial and mixed flow turbines which are an important component of a turbocharger consist essentially of a volute, a rotor and a diffuser. Vaneless volute turbines, which have reasonable performance and low cost, are the most widely used in turbochargers for automotive engines. Care has to be done in the design of the volute, whose function is to convert a part of the engine exhaust gas energy into kinetic energy and direct the flow towards the rotor inlet at an appropriate flow angle with reduced losses. Turbulent compressible flow analysis and performance prediction using the finite volume method with two turbulence models (RNG k-ε and SST) implemented in the ANSYS-CFX software, are carried out on two different volute types. Four volutes, with different cross section areas used for radial turbines, are studied and the computed results are compared with the available experimental data. The second volute studied is the one used for a mixed flow turbine in the turbocharger test rig at Imperial College. In this part of the study, the interest is focused on the influence of the volute inlet flow conditions on its performance (efficiency, exit flow angle, etc).