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Hydrogen is seen as one of the important energy vectors of the next century. Hydrogen as a renewable energy source, provides the potential for a sustainable development particularly in the transportation sector. Hydrogen-driven vehicles reduce both local as well as global emissions. The laboratory of transport technology (University of Gent) converted a General Motors Corporation/Crusader V-8 engine for hydrogen use. Once the engine is optimized, it will be built in a low-floor midsize hydrogen city bus for public demonstration. For a complete control of the combustion process and to increase the resistance to backfire (explosion of the air-fuel mixture in the inlet manifold), a sequential timed multipoint injection of hydrogen and an electronic management system is chosen. The results as a function of the engine parameters (ignition timing, injection timing and duration, injection pressure) are given.

The use of hydrogen in a spark ignited engine is accompanied by a significant risk for backfire and knock, especially at full load, where the richest mixture is used. In fact, when attempting to maximize engine power, knock can (and usually will) lead to runaway surface ignition and backfire without much delay. Since backfire (and knock) has to be avoided at all cost, an attempt was made to detect and quantify knock from the measured pressure traces. For future use knock detection, combined with multipoint timed hydrogen injection, offers the possibility to avoid backfire by temporarily cylinder deactivation. In a first attempt the standard method using the third derivative of the pressure was tried, but proved to be too insensitive to be of any practical use, even though knock was very audible and the pressure oscillations are easily visible on the measurements. This insensitivity is caused by the very fast combustion achieved with hydrogen, compared to other fuels.

The literature on hydrogen fueled internal combustion engines is surprisingly extensive and papers have been published continuously from the 1930's up to the present day. Ghent University has been working on hydrogen engines for more than a decade. A summary of the most important findings, resulting from a literature study and the experimental work at Ghent University, is given in the present paper, to clarify some contradictory claims and ultimately to provide a comprehensive overview of the design features in which a dedicated hydrogen engine differs from traditionally fueled engines. Topics that are discussed include abnormal combustion (backfire, pre-ignition and knock), mixture formation techniques (carbureted, port injected, direct injection) and load control strategies (power output versus NOx trade-off).