Modifications of double-rim geometry to improve thermal performance of squealer tip in a turbine stage

Abstract

The double-recessed (i.e. double-rim) design is an alternative to improve thermal performance of the squealer tip. In this paper, the aero-thermal performance of double-rim squealer tip in a turbine stage was numerically investigated under engine condition. The heat transfer and film cooling effect between the double-rim squealer tip and conventional squealer tip were compared to show the superior thermal characteristic of double-rim design. The interactions between the leakage flow and coolants were analyzed to address the heat transfer reduction and film cooling improvement for the double-rim configuration. To further reduce the thermal load on double-rim squealer tip, the height and arc length of the inner rim were modified to increase the coolant accumulations in squealer cavities. The results show that the tip and pressure side cooling flow is well attached on the cavity floor and suction side rim of double-rim squealer tip as compared to the conventional squealer tip. With the proper arrangement of inner rim height and arc length, the modified double-recessed squealer tip helps to reduce the area-averaged heat transfer coefficient by 90.3%, and improve the film cooling effectiveness by 49.6%, while the isentropic stage efficiency is almost not affected, as compared to the conventional squealer tip.