LIQUID-HYDROGEN PUMPS FOR AUTOMOTIVE APPLICATION

The availability of compact LH2 pumps suitable for operation on board an automotive vehicle represents a key problem for direct cylinder fuel injection into the hydrogen fueled internal combustion engine. Small high pressure piston pumps for automotive application have been demonstrated by S. Furuhama (Musashi Institute of Technology). These pumps were located inside of the LH2 fuel tank which is adversative to minimum heat leak of the cryogenic fuel tank. This in turn necessitates the development of small pumps arranged separately from the vehicle's tank. In this way one avoids significant heat leaks and boil-off losses. Within the long range program of noted automobile manufacturers the DLR is aiming at the development of LH2 pump prototypes. At first, in a joint project between BMW and DLR, a 2.5 MPa LH2 piston pump operated by a hydraulic drive was developed for a research vehicle using early cylinder injection of cryogenic hydrogen. As a consequence of special design the cooldown period of the pump is less than 5 min and the warming up rate after shutdown is about 15 K h-1. By a special arrangement of materials the detrimental radial thermal expansion of piston/piston sleeve with respect to the cylinder could be eliminated. Priming of the pump is made by use of gaseous hydrogen for cyclic pressurization of the section around the intake valve. Furthermore, priming of the pump is also possible by means of a 0.2 MPa highly reliable membrane type LH2 boost pump, using a cold linear electromagnetic drive. This pump can be located inside of the fuel tank without any detrimental increase of the heat leak between inner and outer vessel. Further optimum configurations are discussed for fuel conditioning systems dependent upon pressure range and location of liquid pumps and cold compressors. © 1990.