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The operating conditions and the propellant transport properties used in Earth-to-Orbit (ETO) applications affect the aerothermodynamic design of ET0 turbomachinery in a number of ways. This paper discusses some aerodynamic and heat transfer implications of the low molecular weight fluids and high Reynolds number operating conditions on future ET0 turbomachinery. Using the current SSME high-pressure fuel turbine as a baseline, the aerothermodynamic comparisons are made for two alternate fuel turbine geometries. The first is a revised first-stage rotor blade designed to reduce peak heat transfer. This alternate design resulted in a 23% reduction in peak heat transfer. The second design concept was a single-stage rotor to yield the same power output as the baseline twostage rotor. Since the rotor tip speed was held constant, the turbine work factor doubled. In this alternate design the peak heat transfer remained the same as the baseline. While the efficiency of the single-stage design was 3.1 points less than the baseline two-stage turbine, the design was aerothermodynamically feasible, and may be structurally desirable.

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A numerical study of the aerodynamic and thermal environment associated with axial turbine stages is presented. Computations were performed using a modification of the unsteady viscous code, ROTOR1, and an improved version of the steady inviscid cascade system, MERIDL-TSONIC, coupled with boundary layer codes, BLAYER and STAN5. Two different turbine stages were analyzed: the first stage of the United Technologies Research Center Large Scale Rotating Rig (LSRR) and the first stage of the Space Shuttle Main Engine (SSME) high pressure fuel turbopump turbine. The time-averaged airfoil midspan pressure and heat transfer profiles were predicted for numerous thermal boundary conditions including adiabatic wall, prescribed surface temperature, and prescribed heat flux. Computed solutions are compared with each other and with experimental data in the case of the LSRR calculations. Modified ROTOR1 predictions of unsteady pressure envelopes and instantaneous contour plots are also presented. Relative merits of the two computational approaches are discussed.

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