Heat/mass transfer over the cavity squealer tip equipped with a full coverage winglet in a turbine cascade: Part 2 – Data on the cavity floor

Abstract

Heat/mass transfer characteristics on the floor of the cavity squealer tip equipped with a full coverage (FC) winglet has been investigated experimentally with the variation of h/s (tip gap height-to-span ratio) by employing the naphthalene sublimation technique. For a squealer rim height-to-span ratio of hst/s=3.75% and a winglet width-to-pitch ratio of w/p=10.55%, the tip gap is changed to be h/s=0.34%, 0.68%, 1.02%, 1.36%, and 1.70%. In this study, the cavity floor is divided into four specific regions based on local heat/mass transfer rate, and the effects of h/s on local heat/mass transfer rate are fully discussed. The results show that average heat/mass transfer rate on the floor of the cavity squealer tip with the FC winglet increases steeply with the increment of h/s. This average value is found lower in the case of low h/s but higher in the case of high h/s, in comparison with that for the cavity squealer tip with no winglet. However, it is always lower than that on the plane tip surface with no winglet. For the cavity squealer tip with the FC winglet, average heat/mass transfer rate on the cavity floor is lower than that on the winglet top surface regardless of h/s, but the discrepancy between them tends to decrease rapidly as h/s increases.