Cold-air performance of free power turbine designed for 112-kilowatt automotive gas-turbine engine. III. Effect of stator-vane end clearances on performance
An experimental investigation of a free power turbine designed for a 112-kW, automotive, gas-turbine engine was made to determine the penalty in performance due to the stator-vane end clearances. Tests were made over a range of mean section stator-vane angles from 26/sup 0/ to 50/sup 0/ with the vane end clearances filled. These results are compared with test results of the same turbine with vane end clearances open. At design equivalent values of rotative speed and pressure ratio and at a vane angle of 35/sup 0/, the mass flow with the vane end clearances filled was about 8% lower than mass flow with vane end clearances open. This decrease in mass flow was mitigated by increasing the vane angle. This was as expected since vane loading and reaction decrease with increasing vane angle. With the vane end clearances filled, there was about a 66% reduction in mass flow when the vane angle was decreased from 40/sup 0/ to 26/sup 0/. For the same decrease in vane angle the stator throat area decreased by about 50%. This result indicates that the rotor losses were increasing with decreasing vane angle. At design equivalent values of speed and pressure ratio, there was a penalty of about 4 points in total efficiency due to the vane end clearances of 1.1 and 1.9% of the vane height for the hub and tip sections, respectively. This penalty remained about constant over the range of vane angles investigated. Significant increases in total efficiency were obtained for both stator-vane end configurations as the vane angle was increased from 26/sup 0/. A peak total efficiency of about 0.91 was obtained at the vane angle of 45/sup 0/ with the vane end clearances filled. Results of static-pressure measurements and rotor-exit surveys showed that the rotor reaction was positive from hub to shroud for the vane angle of 45/sup 0/. Although high negative rotor incidence angles were obtained, the high positive rotor reactions would be expected to minimize the effects of increased losses due to incidence.
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- DOE Contract Number:
- EC-77-A-1011
- OSTI ID:
- 6379518
- Report Number(s):
- DOE/NASA/1011-78/29; NASA-TM-78956
- Country of Publication:
- United States
- Language:
- English
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