Compressible DNS studies of the boundary layer on a low pressure turbine blade at high incidence

Abstract

The gas turbine is an integral part of the power generation system in most of the aviation industry. The overall efficiency of an engine depends chiefly on the efficiency of the gasturbine, which in turn depends on efficient blade designs. According to a recent report by Jahanmiri (2011), a 1% improvement in the efficiency of a low pressure turbine (LPT) results in savings of about USD52,000 per year on a typical airliner. The turbo-machinery industry strives to increase turbine blade loading in order to reduce weight and total cost. It has been constantly realized that lack of proper understanding of the complicated flow over these blades is impeding efforts to improve the aero-dynamic design of blades. Also the life of a turbine blade is directly related to the fluctuating heat transfer rates on its surface. Based on a report by Reed (1985), Narasimha (1991) notes that a 25% difference in heat transfer rates on a turbine blade can mean an order of magnitude difference to its life. Moreover, one study shows that as much as 70% on the suction side of a typical turbine blade could be transitional (Narasimha 1991). This phenomenon is directly related to the instantaneous peak heat transfer rate on a blade, which in turn is related to the life of the blade and the efficiency of the gas-turbine in general. These observations make flow past a blade, especially in the harsh and highly disturbed environment characteristic of turbomachinery, a crucial problem in fluid-dynamics that needs to be understood.