Studies on Transonic Turbines with Film-Cooled Blades.
Annual technical rept. no. 3, 1 Jul 75-30 Jun 76,
MASSACHUSETTS INST OF TECH CAMBRIDGE GAS TURBINE LAB
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In the third year of the contract, further advances were made towards the goal of gathering the heat transfer and aerodynamics flow data necessary for a good understanding of the performance of film-cooled, highly-loaded, transonic turbine blading. The MIT cascade blowdown facility now fully operational was used in evaluating the heat transfer performance of the four blade profiles designed in the first year of the program. The results show that the level of turbulence is an important parameter in determining heat transfer in transonic cascades. It also shows that the heat transfer to the trailing edge of the blades is very high being about 75 of the heat transfer to the leading edge. A comparison of the Nusselt number calculated from heat transfer measurements with the Nusselt number obtained by a prediction method using the pressure distribution shows good correspondence. The variation of average Stanton number over a range of Mach numbers shows that the reference blade has the most superior heat transfer performance. Preliminary data has been obtained on the off-design performance of the blades and full scale tests are underway. Comparative studies show that about 21 less heat needs to be taken out by internal cooling if one stage of a transonic turbine is used to replace two moderately loaded subsonic stages which produce the same output, have the same inlet stagnation conditions, have the same mass flow and the same tip speed. This demonstrates one of the potential advantages of transonic turbines.
- Fluid Mechanics
- Jet and Gas Turbine Engines