Radial Supercharger Turbines - Calculations and Modeling

When sizing a radial supercharger turbine, experience shows that the most critical component is the volute, which accounts for more than half of the total energy loss—and this is without considering the heat transfer it causes. For this reason, a one-dimensional approach to flow in the volute has been detailed to derive the expression for the velocity components at the impeller inlet.

The flow in the volute is not adiabatic, and a similarity law is proposed for the entire turbine. These dimensionless numbers provide engineers with a simple, approximate method for transposing results to different test and operating conditions.

A quick calculation scheme is proposed, using assumptions and estimations for certain modeling coefficients (losses, effects of angle of attack and angular deflection, etc.), followed by a numerical application, satisfying the conditions encountered at a nominal operating point. The results obtained make it possible to sketch out the machine’s geometry and thus ensure the feasibility of using a radial turbine. Based on the resulting geometry, a one-dimensional model of the entire turbine assembly is developed to predict its characteristic curves. The results from the proposed models are compared with experimental results provided by manufacturers. The prediction of overall performance proves to be very satisfactory and sufficient for the preliminary design step.