Abstract
Single-row double-jet film cooling (DJFC) of a turbine guide vane is numerically investigated in the present study, under a realistic aero-thermal condition. The double-jet units are positioned at specific locations, with 57% axial chord length (Cx) on the suction side or 28% Cx on the pressure side with respect to the leading edge of the guide vane. Three spanwise spacings (Z) in double-jet unit (Z = 0, 0.5d, and 1.0d, here d is the film hole diameter) and four spanwise injection angles (β = 11°, 17°, 23°, and 29°) are considered in the layout design of double jets. The results show that the layout of double jets affects the coupling of adjacent jets and thus subsequently changes the jet-in-crossflow dynamics. Relative to the spanwise injection angle, the spanwise spacing in a double-jet unit is a more important geometric parameter that affects the jet-in-crossflow dynamics in the downstream flowfield. With the increase in the spanwise injection angle and spanwise spacing in the double-jet unit, the film cooling effectiveness is generally improved. On the suction surface, DJFC does not show any benefit on film cooling improvement under smaller blowing ratios. Only under larger blowing ratios does its positive potential for film cooling enhancement start to show. Compared to the suction surface, the positive potential of the DJFC on enhancing film cooling effectiveness behaves more obviously on the pressure surface. In particular, under large blowing ratios, the DJFC plays dual roles in suppressing jet detachment and broadening the coolant jet spread in a spanwise direction. With regard to the DJFC on the suction surface, its main role in film cooling enhancement relies on the improvement of the spanwise film layer coverage on the film-cooled surface.
Highlights
Publisher’s Note: MDPI stays neutralFilm cooling has been widely applied to the highly-efficient thermal protection of guide vanes in modern gas turbines [1]
Through shaped film cooling holes, the jet injection is modified and subsequently, the flow dynamics of jet-in-crossflow, which is attributed to the cancellation of the kidney vortex pair or counterrotating vortex pair (CVP) that originates from the mutual interaction of the ejecting jet with oncoming crossflow
For the double-jet film cooling (DJFC), local η ad distribution immediately behind the front-hole was very similar to the single compound-angle hole film cooling before the front jet interacted with the rear jet
Summary
Film cooling has been widely applied to the highly-efficient thermal protection of guide vanes in modern gas turbines [1]. As the gas turbines advance, the turbine inlet temperature will be progressively elevated such that the thermal-protection requirement becomes more critical. To ensure the guide vanes work reliably under crucial aero-thermal conditions without significant deterioration, developing more efficient film cooling schemes is a necessity. The innovation of shaped holes is regarded as the most inspiring advancement [4]. Through shaped film cooling holes, the jet injection is modified and subsequently, the flow dynamics of jet-in-crossflow, which is attributed to the cancellation of the kidney vortex pair or counterrotating vortex pair (CVP) that originates from the mutual interaction of the ejecting jet with oncoming crossflow. It is well known that the earlier exploration of shaped holes was initialized in the middle of the 1970s. The preliminary investigation of Goldstein et al [5]
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