Richard J. Roelke
Published: 1987
Total Pages: 13
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An experimental performance evaluation was made of two moveable sidewall variable area radial turbines. The turbine designs were representative of the gas generator turbine of a variable flow capacity rotorcraft engine. The first turbine was an uncooled design while the second turbine had a cooled nozzle but an uncooled rotor. The design, fabrication and testing were carried out by Teledyne CAE under a series of government contracts. Performance measurements were taken over a turbine flow range of 2:1 in the Contractor's warm (121 C) air facility. The cooled nozzle turbine was evaluated both with and without coolant flow. The test results showed that the moveable nozzle wall is a viable and efficient means to effectively control the flow capacity of a radial turbine. Peak efficiencies of the second turbine with and without nozzle coolant were 86.5 and 88 percent respectively. These values are comparable to pivoting vane variable geometry turbines; however, the decrease in efficiency as the flow was varied from the design value was much less for the moveable wall turbine. The measured turbine performance over the entire flow range was within one point of the estimated turbine performance used in a previously conducted variable flow capacity engine analysis which showed significant fuel savings. Several design improvements were identified which should increase the turbine efficiency one or more points. These design improvements include reduced leakage losses and relocating the vane coolant ejection holes to reduce mainstream disturbance.
