温暖化に対する厳しいCO_2排出規制に代表されるrnように，深刻な地球環境問題への打ち手が望まれる現rn在，エネルギー変換の高効率化は今までにも増して重rn要な課題であり，その根幹を支える蒸気タービンの性rn能向上技術開発には不断の努力が必要とされる．%In order to address recent environmental problems such as global warming due to CO_2 emissions, continuous efforts are required to improve the performance of the steam turbine, which supports the base of energy conversion. Although the aerodynamic design technologies of steam turbine have been developed remarkably by applying the computational fluid dynamics (CFD), it is not easy to reduce the losses within a low aspect ratio cascade in the control stage and high pressure stages even if the latest three-dimensional design are used. Then, the authors investigated the loss generation mechanism in a low aspect ratio cascade using the smoke visualization and detailed internal flow measurement with a micro pitot probe to develop the new technologies for reducing the secondary loss. This paper describes the evolution of horseshoe vortex and passage vortex through a turbine blade in experimental studies, theoretical approach to explain the motion of the vortex and the effects of inlet boundary layer on passage vortex interaction analyzed by three-dimensional viscous flow analysis.
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