This paper presents results of rig testing of a transonic, single stage turbine at off-design conditions. Mapping of the 3.4 pressure ratio, 1.9 stage loading turbine ranged from 70% through 120% of design speed and 75% to 125% of design pressure ratio. Results show expansion efficiency dropping over 4% from 100% to 80% of design speed at design pressure ratio, while remaining within half a percent from 90% to 110% of design pressure ratio at design speed. Efficiency lapse rate from equivalent sea-level to cruise altitude Reynolds numbers at the design point was measured and found to be worth over 1.5%. Analyses of test results using a viscous 3D solver showed very good agreement for the efficiency change with speed.

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