Effect of the axial clearance on the performance characteristics of a low-flow reaction turbine

This study is concerned with a stage of a radial low-flow reaction turbine, which is used in aircraft engines, propellant feed systems of rocket engines, turbocharging systems of internal combustion engines, etc. The goal of the study is to investigate the effect of the clearance between the impeller and the stationary housing of a radial-flow turbine on its power parameters. The paper shows the need to refine, supplement, and sort parametric data on the effect of the axial clearance between the free edge of a radial-flow turbine impeller blade and the stationary housing on the turbine power parameters. It is shown that clearances in the turbine setting play an important role in the working process and significantly affect the key performance characteristics. The correctness of the methodological approaches to the tests and experimental studies conducted is verified by the results of other authors. The studies were conducted in two stages. At the first stage, a turbine stage was tested as a part of a single model gas-dynamic circuit with a compressor stage and a combustion chamber. At the second stage, tests were carried out with two independent gas-dynamic ducts of the turbine and compressor, in which the working fluid was supplied to the units separately, with the possibility of flow rate control. The novelty of the study consists in obtaining new data on the effect of the axial clearance in small-sized radial low-flow turbines on the key power and performance parameters of the stage. In the study, generally accepted methods of experimentation and data processing were used. The obtained results allow one to relate the parameters of the expansion process in reaction gas turbines to the axial clearance value. The practical value of the results lies in the possibility of using the obtained experimental data in designing low-flow impeller machines for jet engines and in refining computational methods.