Centrifugal turbines - Calculations and modeling

In the design of a turbine, the most delicate point is the volute, which is responsible for more than half of the total energy degradation, and this without taking into account the heat transfers it causes. A one-dimensional approach to the flow in the volute has been detailed in order to obtain the expression of the velocity components at the impeller inlet.

The flow in the volute is not adiabatic, and a similarity law is proposed for the whole turbine. These adimensional numbers provide the engineer with an easy, approximate method of transposing results to different test and operating conditions.

Using simplifying assumptions, a quick calculation is presented, followed by a numerical application, to satisfy a nominal operating point. The results obtained make it possible to sketch out the geometry of the machine, thus confirming the feasibility of using a centripetal turbine. Based on the geometry, a one-dimensional model of the turbine assembly is developed to predict its characteristic curves.

A table of notations and symbols is provided in the first part of this document. .