Many technologies are being developed to solve the trouble of
the urban pollution. Among other solutions (improvements in engine
control and combustion, electrical propulsion) one of the foreseen
ways is the employment of low or zero carbon content fuels, such as
hydrogen. In fact a nearly zero emission vehicle may be obtained
through the hydrogen propulsion; in this case the only polluting
agents are nitrogen oxides if an internal combustion engine is
used. Though fuel cells are considered as the most promising
solution in the long term, they are still in their prototypical
phase and the use of the internal combustion engine use remains
until today a relevant topic.
It has been evident since the 80s that direct injection is the
only method to get a high specific power without pre-ignition and
backfire phenomena. However this technique shows a higher
difficulty in getting a well-mixed charge. The process of mixing
between air and fuel obviously depends upon many parameters, such
as the injection pressure and timing, the location of the injectors
and so on. In this study the effects of the injection parameters on
combustion, engine performances, emissions and efficiency were
analyzed.
Commercial electro-injectors were considered in this paper, and
one of the main issues of the described work was the analysis of
the engine performances and emissions as a function of the engine
rotating speed and load. This paper shows the realization of a
directly injected, hydrogen-fuelled prototype and the results of
its experimental testing. Performances, consumption and
NOx emissions are discussed as well as the influence of
the injection parameters on the heat release rate.