Tip gap flow characteristics in a turbine cascade equipped with pressure-side partial squealer rims

Tip gap flow characteristics and aerodynamic loss generations in a turbine cascade equipped with pressure-side partial squealer rims have been investigated with the variation of its rim height-to-span ratio (hp/s) for a tip gap height of h/s = 1.36%. The results show that the tip gap flow is characterized not only by the incoming leakage flow over the pressure-side squealer rim but also by the upstream flow intrusion behind the rim. The incoming leakage flow tends to decelerate through the divergent tip gap flow channel and can hardly reach the blade suction side upstream of the mid-chord, due to the interaction with the upstream flow intrusion as well as due to the flow deceleration. A tip gap flow model has been proposed for hp/s = 3.75%, and the effect of hp/s on the tip surface flow is discussed in detail. With increasing hp/s, the total-pressure loss coefficient mass-averaged all over the present measurement plane decreases steeply, has a minimum value for hp/s = 1.88%, and then increases gradually. Its maximum reduction with respect to the plane tip result is evaluated to be 11.6%, which is found not better than that in the cavity squealer tip case.