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The goal of hydrogen engine research is to achieve highest possible efficiency with low NOx emissions. This is necessary for the hydrogen car to remain competitive with the ever-improving efficiency of conventional fuel's use, to take advantage of the increased availability of hydrogen distribution for fuel cells and to achieve better range than battery electric vehicles. This paper examines the special problems of hydrogen engine combustion and ways to improve efficiency. Central to this are the effects of compression ratio (CR) and lambda (excess air ratio) and ignition system. The results demonstrate highest indicated thermal efficiency at ultra lean condition of lambda ≻ 2 and with central ignition. This need for this lean mixture is partly explained by the higher heat transfer losses.

The gross emissions for the Australian vehicle fleet are forecast from estimates of population growth, vehicle ownership and vehicle in-service performance. These estimates are coupled with sensitivity analyses, to emissions deterioration and on-road performance and the impact of alternative fuels. It is concluded that more data on precontrol and high mileage controlled vehicles is needed to remove uncertainties in the projections. The results indicate that existing vehicle emission control standards will continue to give beneficial reductions in hydrocarbon emission levels through to 1995 and present levels will not be exceeded this century. Ambient ozone trends have fallen and are qualatatively in accord with reducing vehicle emissions.