ENGINE EXPERIMENTAL RESULTS WITH HYDROGEN TWO-STEP DIRECT INJECTION

摘要

In hydrogen-fuelled internal combustion engines, port fuel injection, compared to directrninjection, allows higher range and is less expensive and more adaptable to existing engines,rnbut leads to lower specific power and may cause backfire and pre-ignition. Conversely, directrninjection is more complex and expensive, but provides even higher specific power than withrngasoline, prevents backfire and makes pre-ignition less probable.rnThe benefits of direct injection are added to those of port fuel injection in an innovative lowpressurern(12 bar rail pressure) direct-injection system that is shown in this paper. Therninjection is accomplished in two steps: first an electroinjector meters hydrogen and feeds arnsmall intermediate chamber, then the hydrogen stored in the intermediate chamber is timelyrninjected into the cylinder by a mechanically actuated valve.rnThe prototype was obtained modifying a production single-cylinder 650 cm~3 engine forrnmotorcycles.rnExperimental results show proper engine operation, without pre-ignition, knocking orrnroughness even with stoichiometric or slightly rich mixtures. Maximum power was higherrnthan with gasoline.