The tip leakage flow which is characterized by the blade tip vortex is a highly complex and unsteady phenomenon. It is of great interest to understand the unsteady pressure characteristics of tip leakage flow. The present study aims to focus on the unsteady pressure behavior caused by tip leakage flow of a single stage axial flow turbine. A series of experiments were carried out with a scaled up high work axial flow turbine in a Large Scale Rotating Rig to understand this unsteady pressure behavior. The pressure fluctuations were mapped at five axial locations on the casing across the rotor tip. Unsteady pressures were measured using calibrated fast response transducers. Measurements were phase-locked with the rotor. The pressure data was ensemble averaged and represented gross unsteadiness in the flow. Experiments were carried out over a range of flow coefficients (Cx/U) like 0.30, 0.32, 0.34 and 0.36. The blade pass frequency was the predominant one seen during the measurements. Mild influence of vane exit wake turbulence was also seen during the measurements. Constant speed flow coefficient variation did not seem to cause additional unsteadiness to the tip leakage flow.

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