• The changes observed were large and three-dimensional in nature. Their neglect in stage blading design could lead to serious miscalculations. Parameters such as pressure coefficient, wake width, three-dimensional velocity field, and exit angles were observed to change significantly.

• The cooling was able to produce significant changes in the total pressure coefficient. The large changes in pressure coefficient are due to a shift in the wake position and wake width rather than a change in the wake peak or trough magnitudes. In the rotational frame, root injection reduced the width of the wake while radial and impingement cooling increased the width. The effects of the rotational frame width changes are smoothed out in the stationary frame measurements. To understand the physical mechanism responsible for the loss coefficient changes (stationary frame) it is necessary to look in the rotational frame.

• Root injection tended to have an opposite effect on the three-dimensional velocity field then radial and impingement cooling. This is consistent with the stationary frame data provided in Part I of this publication. Again, it is necessary to examine both the stationary and rotational frames to have a complete understanding of the physics controlling the velocity field.

• The changes in rotor exit flow are highest at the midspan. The effects of the cooling are convected to the midspan by the action of the passage vortices. It is believed that the cooling air is energizing the boundary layer ahead of the rotor thereby effecting the development and effects of the secondary flows.

Additional research should be performed to detail the complex cooling-mainstream mixing process and its effects on the inlet rotor boundary layer and the resulting secondary flows.

Detailed information and reduced data for this part of the study is presented in Appendix-

"Mainstream Aerodynamic Effects Due to Wheelspace Coolant Injection in a High Pressure Turbine Stage: Part II- Aerodynamic Measurements in the Rotating Frame," (Christopher McLean, Cengiz Camci, Boris Glezer), The ASME Transactions, Journal of Turboma-chinery, Vol.123, No.4 , October 2001, pp. 697-703.

6.2.2 Turbine tip aerodynamics under the influence of coolant injection from a tip trench

Rotational frame velocity and pressure measurements were made downstream of a tip cooled rotor blade row in AFTRF . The specific emphasis was given to study discrete hole cooling injection from a a square cross section trench machined on the tip surface of turbine blades. Measurements were taken at two axial locations to track the development of the secondary flow in the blade tip region using a five hole probe. Coolant mass flow was injected at several locations on the rotor tip to investigate the effect of coolant air on the secondary flow. The ultimate objective is to reduce losses by the introduction of high momentum air in the tip gap. Results indicate that the passage and the leakage vortices retain their structures up to 46 % chord-length downstream of the rotor trailing edge. The cooling air,

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