Determination of an efficient winglet for recessed tip and its loss map in aeroengine turbine cascade

In this investigation, (i) the losses for seven streamlined winglets mounted on the recessed tip are measured with the five-hole probe in a strong-reaction turbine cascade when h/s (tip clearance-to-span ratio) = 1.0 % and w/p (winglet width-to-pitch ratio) = 10.0 %, (ii) the best winglet coverage is selected based on the loss data, and then (iii) its loss map in wide ranges of h/s and w/p is obtained for the recessed tip. For the recessed tip, SW (full suction-side winglet) is found to be the best winglet, and the loss reduction capability of the recessed tip deteriorates in the presence of pressure-side winglet coverage. The reduction of loss by the recessed tip with SW is almost identical to the sum of that by the recessed tip without winglet and that by the flat tip with SW. The full loss data for the recessed tip with SW reveal that wider winglet leads to lower loss, regardless of h/s, but the loss generated by SW of w/p = 5.0 % is not so different from that by SW of w/p = 10.0 %. This tendency becomes more noticeable for higher h/s.