Theoretical Assessment of the Performance Characteristics of Inward Radial Flow Turbines

Abstract

While the simple centrifugal compressor has been widely used over a considerable period of time and in a variety of applications, in particular aircraft gas turbines and aero-engine superchargers, and its behaviour is therefore reasonably well understood, the inward radial flow gas turbine has only recently begun to attract the attention of engineers. As a result, its characteristics are not understood as fully as those of the centrifugal compressor. Inward radial flow turbines have a number of attractive features, such as robustness, cheapness, and relative immunity from thermal stresses, which render them particularly suitable, where the mass throughput and overall pressure ratio are moderate. While the assessment of performance and flow conditions at the design point presents no very great difficulties, the evaluation of performance under conditions of reduced speed and pressure ratio, knowledge of which is essential in most applications, does not appear to have been attempted hitherto. An analytical treatment of part-load conditions is outlined in this paper. In addition, the influence of the various design parameters on the overall characteristics is examined, and tentative suggestions are made for the best combination of these parameters for particular applications.