Floating Seal for Turbopumps

Cryogenic engines for in-space propulsion require innovative technologies to provide long-life, lightweight, and reliable turbopump designs. One area open for improvement is seals for rotating-to-static hardware. Florida Turbine Technologies, Inc. (FTT) is proposing the use of a floating seal for turbopump applications. The floating seal would allow lower leakages than current state-of-the-art seals, such as labyrinth seals. The floating seal also has the added benefit of maintaining low leakages throughout transients and rotor displacements, since the floating seal's clearance tracks with the rotor axial movement and is independent of radial movement. Plus, the floating seal is a non-contacting seal with high pressure and speed capability; this increases its reliability relative to contacting face seals or labyrinth seals operating at the same conditions and leakages. The floating seal is proposed to work with the cryogenic liquid propellants used in upper stage engines, liquid hydrogen and liquid oxygen. The feasibility of the floating seal for turbopump applications will be determined through detailed 3D computational fluid dynamics (CFD) analyses. 1D parametric studies to vary the seal geometry and boundary conditions will also be performed. The concerns of axial instability and increased turbopump axial length will be addressed during Phase I.

NASA's potential application of the innovation would be in cryogenic rocket turbopumps, such as those fed with liquid hydrogen. The floating seal could be located along vertical portions of turbine disks or the shroud or hub of pump impellers – wherever large pressure drops and low leakages are needed. The seal could be used in place of labyrinth seals, brush seals, carbon face seals, and inter-propellant seals. Under FTT's Teaming Agreement with Aerojet, FTT is responsible for design and analysis of the turbopump as well as component hardware manufacturing. Current potential applications include the Affordable Upper Stage Engine also under development with target applications on NASA's SLS family of rockets. FTT is also exploring turbomachinery opportunities to support the nano/micro satellite launch market. Finally, Aerojet is in the process of acquiring Pratt & Whitney Rocketdyne from United Technologies Corporation which will open up additional product lines for the floating seal, such as the RS-25 high pressure fuel and oxidizer turbopumps.

Non-NASA potential applications include similar uses in the Air Force Research Laboratory's (AFRL) Hydrocarbon Boost technology demonstrator engine, in the low or high speed oxygen turbopumps. Pratt & Whitney Rocketdyne could benefit from implementing the floating seal into the RS-68 Oxygen and Hydrogen turbopumps to isolate turbine gases from the bearings and minimize hydrogen leakage onto both turbine disks. Outside of space propulsion, the floating seal could be incorporated into industrial pumps for nuclear power coolant, oil and water transfer pumps or water injection applications.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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