Effects of tip clearance on miniature gas turbines compressor performance: a numerical approach

The miniaturization of gas turbines that are optimized at their current large size leads
to a substantial loss of efficiency and performance at the smaller scales. One of the
important loss sources is tip clearance flow. In this study, a numerical approach is
carried out to assess the effects of TC, based on an axial compressor in gas turbines. Firstly,
constant TC value is applied and results are compared with benchmark case without TC.
Thereafter, varied TC values are applied with compressor blade height unchanged, to
understand the effect of varied TC ratio. Thirdly, constant TC value is applied with blade
height changed, i.e. varied Reynolds number, to assess the effect of TC on miniaturized
compressor. Our results indicate that compressor performance deteriorates with the
existence of TC and the performance loss amplifies with the increase of TC ratio. The
miniaturization of compressor also results in performance loss, due to increased TC ratio. In
addition, detailed observation of flow field has identified the occurrence of fluid jet and the
transition of fluid jet when TC is applied. The present study clarifies the effects of TC on
compressor performance, especially for miniature gas turbines.