마이크로 가스터빈 엔진에 적용된 압축기 공력성능 특징

Abstract

A centrifugal compressor is essentially applicable to a micro gas turbine because it can produce a high-pressure ratio over than 3.0 within a limited geometrical allowance. In this paper, aerodynamic design and internal flow characteristics of the centrifugal compressor were described in detail by comparing them with those of turbocharger compressors. Then a centrifugal compressor design procedure with a pressure ratio of 5.0 at the design point for a 1,000 N thrust micro gas turbine has been introduced and the internal flow field at the design point has been further investigated with CFD methods. High impeller pressure ratio led to high absolute Mach number at the impeller outlet, however, small gap between the impeller outlet and diffuser inlet did not sufficiently recover static pressure and it caused large flow separation region and corresponding total pressure at the diffuser hub. For this reason, it requires sophisticated matching between impeller and diffuser stages in micro gas turbines. Based on the internal flow analysis, ideas for further performance improvements have been proposed while maintaining essential compressor performances.