Abstract
ABSTRACT Film cooling is one of the essential approaches to cool high-performance turbine blades. Film cooling with delta winglet vortex generator pair (DWVGP) placed upstream of the cooling hole is investigated by large eddy simulation (LES) at the blowing ratio of M=1.0. Film cooling effectiveness and vortical structures are evaluated in the flow field of a jet in crossflow (JICF). Results indicate that film cooling effectiveness increases significantly for the DWVGP case. As a dominant vortex structure, the ubiquitous counter-rotating vortex pair (CRVP) is recognized in the flow field. It has a detrimental effect that lifts the coolant off the cooling surface. The DWVGP evolved anticounter-rotating vortex pair (anti-CRVP) has the opposite sense of rotation to the jet introduced CRVP, which undertakes vorticity decay when developing downstream of the cooling hole. With the downwash effect of anti-CRVP, the reattachment of coolant is earlier, and a wide region of enhanced film cooling effectiveness in the spanwise direction is achieved. The coherent vortex structures including the classical vortices in the flow field and the vortex generator pair introduced vortices are analyzed. The genesis and evolution mechanism of CRVP with and without the vortex generators are discussed. It indicates that three branches of upstream spiral structures from the nozzle tube contribute to the CRVP. The merging of CRVP upstream branches is delayed by the vortex generators evolved anti-CRVP, which postpones the formation of downstream CRVP.
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