Improved Turbine Blade Cooling Using Endwall Flow Modifications. A trident Scholar Project Report, No. 260

摘要

A flow modification technique designed to allow increased turbine inlet temperatures while keeping the turbine blades below their thermal limits is introduced. A large-scale two-half-blade cascade simulator is used to model the secondary flow between two adjacent turbine blades. Various flow visualization techniques and measurements are used to verify that the test section replicates the flow of an actual turbine engine. Two techniques are employed to modify the endwall secondary flow by altering the flow characteristics, specifically the path of the horseshoe vortex. Five wall jets are installed at a location downstream of the saddle point near the leading edge of the pressure side blade. These wall jets, near the saddle point, are found to be ineffective in diverting the path of the horseshoe vortex. The second technique utilizes a row of 12 centerline wall jets whose positions are based on results from a modified fence. The row of jets have successfully diverted the path of the horseshoe vortex and decreased its effect on the suction side blade. This can be expected to increase the effectiveness of film cooling in that area. However, the row of jets increased the aerodynamic losses in the turbine passage, which would result in a decrease of turbine efficiency.