FILM COOLING EFFECTIVENESS DISTRIBUTION ON FIRST-STAGE VANE ENDWALL WITH AND WITHOUT LEADING-EDGE FILLETS PART II: EFFECT OF INCIDENCE ANGLE

摘要

Using the leading edge airfoil fillet to reduce the aerodynamic loss and surface heat transfer has been proved effective, while the factor of film cooling has not been considered. The first part of the research indicates that the leading edge fillet could improve the film cooling effectiveness through controlling the secondary flow, while this conclusion is restricted to the design condition. The flow field at off-design condition is different from that of the design condition, especially for the structure of horseshoe vortex at the leading edge. It's possible that the advantage of fillets is not reliable at positive or negative inlet flow angle conditions, which makes the investigation on endwall film cooling with leading edge modification at off-design condition necessary. This paper, which is the second part of a two-part series research investigating the effects of leading edge modification on endwall film cooling, is focused on the performance of fillets at off-design condition. The influence of incidence angle on film cooling effectiveness is studied on first-stage vane endwall with and without leading-edge fillets. A baseline configuration and three kinds of leading edge airfoil fillets are tested in a low speed four-blade cascade consisting of large scale model of the GE-E3 Nozzle Guide Vane (NGV). The results show that as the incidence angle varies from i=+10 deg to i=-10 deg, at low blowing ratio the film cooling effectiveness decreases near the leading edge suction side for all the leading edge geometries. However, this trend becomes opposite under high blowing ratio that the lowest film cooling effectiveness condition is at the incidence angle of i=+10 deg. Near the leading edge pressure side, the film cooling effectiveness increases as the incidence angle varies from i=+10 deg to i= -10 deg at all blowing ratios in the research. The change of incidence angle causes the peak of laterally averaged effectiveness in this region to shift upstream. The experimental results also indicate that the longfillet has the lowest sensitivity towards incidence angle. As for the main passage endwall, with the incidence angle changing form i=+10 deg to i=-10 deg the averaged film cooling effectiveness increases, while this trend will be eliminated by increasing the blowing ratio.