High Efficiency Regenerative Helium Compressor

Helium plays several critical rolls in spacecraft propulsion. High pressure helium is commonly used to pressurize propellant fuel tanks. Helium cryocoolers can be used to sub-cool and thereby densify cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2). The use of densified cryogenic propellants can reduce the gross payload weight of a launch vehicle by up to 20%, or increase payload capability. Helium compressors are critical components for cryogenic propellant storage and distribution systems, whether used in cryocoolers for densification or to compress gaseous helium for propellant pressurization. Regenerative compressor technology can serve high head, low flow helium pressurization applications in a compact form with high reliability. Pressure ratios on the order of 3:1 per impeller-stage are commercially available. Non-lubricated gas-bearing supported prototypes have been successfully demonstrated. However, even state-of-the-art prototype regenerative compressors are limited to efficiencies of about 55%. This was achieved using aerodynamic rotor blades rather than the straight radial blades previously used. Commercially available regenerative compressors with straight vaned rotors operate at much lower efficiency. An innovation is proposed that promises to improve the efficiency of regenerative compressors well beyond the current state of the art.