Developments in the energy and environmental sectors have awakened interest in hydrogen-fueled internal combustion engines. Based on a 50-engine survey of recent U.S. research and demonstration activities, the technical status of hydrogen engines is summarized. A comparative hydrogen/conventional-fuel orientation is maintained in assessing basic fuel property, engine power and efficiency, emissions and general operating characteristics.
Key theoretical and experimental results, and correlations where evident, are noted. Engine problem areas and their solutions are discussed, accompanied by some thoughts toward future development possibilities and supporting research needs.