Pressure Surface Separations in Low-Pressure Turbines—Part 2: Interactions With the Secondary Flow

This paper describes a study of the interaction between the pressure surface separation and the secondary flow on low-pressure turbine blades. It is found that this interaction can significantly affect the strength of the secondary flow and the loss that it creates. Experimental and numerical techniques are used to study the secondary flow in a family of four low-pressure turbine blades in linear cascade. These blades are typical of current designs, share the same suction surface and pitch, but have differing pressure surfaces. A mechanism for the interaction between the pressure surface separation and the secondary flow is proposed and is used to explain the variations in the secondary flows of the four blades. This mechanism is based on simple dynamical secondary flow concepts and is similar to the aft-loading argument commonly used in modern turbine design.