Laser-Doppler Studies of the Wake-Effected Flow Field in a Turbine Cascade

The interaction between consecutive blade rows can be expected to have important effects on the heat transfer in cooled gas turbine cascades. In determining the local heat transfer under the influence of wake flow, nonintrusive optical measuring techniques were used to obtain the flow velocities and turbulence structures in the cascade inlet flow as well as along the test blade’s surface. The main purpose of the measurements is to provide accurate experimental data for the development of predictive codes. The applicability primarily of the laser-Doppler technique is discussed and problems arising from the use of laser-dual-focus anemometry are reported. In simulating the effects of wake flow, a plane airfoil was traversed in front of the cascade. Both the axial distance between the airfoil and the cascade and the position in circumferential direction were changed in discrete steps. Turbulence intensities between 1.4 and 15 percent were recorded in cold gas flow. The effects on the blade heat transfer are illustrated.