Secondary Flow Measurements in a Turbine Passage With Endwall Flow Modification

Abstract

A flow modification technique is introduced in an attempt to allow increased turbine inlet temperatures. 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, specifically the path of the passage vortex. Six endwall jets are installed at a location downstream of the saddle point near the leading edge of the pressure side blade. These wall jets are found to be ineffective in diverting the path of the passage vortex. The second technique utilizes a row of 12 endwall jets whose positions along the centerline of the passage are based on results from an optimized boundary layer fence. The row of jets successfully diverts the path of the passage vortex and decreases its effect on the suction side blade. This can be expected to increase the effectiveness of film cooling in that area. The row of jets increases the aerodynamic losses in the passage, however. Secondary flow measurements are presented showing the development of the endwall flow, both with and without modification. [S0889-504X(00)01004-7]

Controlling secondary flows in very highly-loaded low-pressure turbine cascades

“…As a followup to the work of Chung and Simon, Aunapu et al (2000) used endwall jets to modify the endwall flow. The airflow requirements were similar to those used for film cooling.…”

“…Geometric modifications to the endwall region have been shown to yield lower secondary losses. Both Chung and Simon (1991) and Aunapu et al (2000) studied the effects of endwall fences on the secondary flow in a linear cascade representation of a single turbine blade passage. Their investigations showed that the size and strength of the passage vortex could be reduced with the application of endwall fences.…”

Effect of streamwise fences on secondary flows and losses in a two-dimensional turbine rotor cascade

“…The stronger cross-channel pressure gradient directly affects Aunapu et al [3] have done investigation to reduce the secondary flow with end wall flow modification. They have used end wall jets for this purpose and have concluded that the end wall jets located in the center of a turbine passage are effective in altering the path of the pressure-side leg of the horseshoe vortex.…”

Numerical Study of Effect of Streamwise End Wall Fences on Secondary Flow Losses in Two Dimensional Turbine Rotor Cascade

“…No quantitative results showing the effect of counter rotating vortex were presented. Aunapu et al (2000) performed tests on the end wall fence. The fence length was modified by 30% from the upstream end and 20% from the downstream end.…”