A Detailed Analysis of Radial Turbines

The field of radial turbines is wide and radial turbines of today find applications inareas as diverse as small gas turbines; turbochargers for cars, buses, and trucks, railwaylocomotives, and diesel power generators; cryogenic and process expanders; rocket engineturbopumps; and specialty steam turbines, [12]. The three-dimensional flow inside aradial turbine is complex and ever since the radial turbine was introduced on the market,a desire to model this flow with simple correlations and loss models has existed.This master thesis consist of two studies. In the first study two radial turbines aremodeled on a mean-line basis and the performance of different operating conditionsare simulated. The results are compared to test data to evaluate the accuracy of thesimulations. In the second and final study an aerodynamic design of a radial turbine isconducted. Initially a preliminary design is considered. This design is evaluated withthe same mean-line tool which were used to simulate the two turbines already mentionedand additionally a blade-to-blade tool. The preliminary design is revised, based on theevaluations, to a detailed design. The detailed design is evaluated with the same toolsas the preliminary design and changed until it meets the requirements stated.The results from the simulations show good agreement with the test data and it can,therefore, be concluded that it would be possible to evaluate a new design using themean-line tool used in this thesis. It is, however, naive to think that a mean-line analysisis able to predict the flow completely and thus the mean-line analysis should be viewedas a tool which is able to speed up the design process. It is difficult to judge theaerodynamic design from the second study because it would require for the turbine tobe manufactured and tested. However, the design shows promise according to the one-and two-dimensional analyses preformed.