Hydrogen: The future cryofuel in internal combustion engines

The characteristics of cryogenic hydrogen, such as high density and considerable cooling effect, favor the fuel injection, the mixing process and thus the combustion process. In addition to the preferred use of liquid hydrogen due to its range per tank filling and low amount of mass for storage in the vehicle, the cryogenic characteristics of hydrogen provide significant advantages. In addition to engine operation with external mixture formation, considerable success was achieved with internal mixture formation with injection of cryogenic high pressure hydrogen. Only pressurization of cryogenic hydrogen can be accomplished without investing a considerable amount of engine power. Hybrid mixture formation, a proper combination of external and internal mixture formation with suitably pressurized cryogenic hydrogen, is very attractive with respect to power and torque as well as other positive characteristics under steady and intermittent operating conditions. The state of the art technology of liquid hydrogen represents a suitable base for large scale demonstration projects now. Additional aims of more intense R&D work relate to internal mixture formation and improved engine drivability, as well as utility vehicle application including trucks and buses. With respect to fuel costs there will be an increased demand in developing hydrogen production free from CO2 emissions even from fossil sources such as crude oil or natural gas. (C) 1997 International Association for Hydrogen Energy.