Heat Transfer Characteristics of the Multicavity Tips at Different Turbulence Levels

A comprehensive understanding of the tip heat transfer characteristics is important to the blade tip design. In this work, the heat transfer coefficient (h) data of several multicavity tips was measured using a steady-state method with an infrared camera. The multicavity tips with different cavity numbers were developed by placing ribs into the traditional squealer tip. All the measurements were conducted in a low-speed linear cascade. Moreover, to gain insight into the heat transfer characteristics of the multicavity tips, computational simulations verified by measurements were implemented to acquire the detailed flow structure of these tips. Measurement results show that the h distributions of the multicavity tips are changed by the ribs. Due to the reattachment of the leakage flow, additional high-h regions are observed downstream of the rib. And the h values in the suction-side rim corner increase, especially at near the trailing-edge. A low-h region is found in the corner upstream of the rib. Furthermore, adopting a high freestream turbulence level would enhance the heat transfer. The augment of h values on the tip front portion is more evident than that on the midto-rear part. The validation in a turbine stage indicates that the present data obtained in the stationary condition still could reveal the heat transfer characteristics of these multicavity tips in a rotating condition.