Development of a Hydrogen Direct Injection Reciprocating Engine using Commercial Injectors

Several techniques are being eveloped to solve the problem f urban pollution. Among other solutions (improvements in engine control and combustion, electrical propulsion) one of the possibility is the employment of low carbon content fuels. A nearly zero emission vehicle may be propelled by hydrogen, in this case the only polluting agents are nitrogen oxides when using internal combustion engines. Though fuel cells are considered to be the most promising solution in the long term, they are still in the prototypical phase, while the internal combustion engine continues to be a relevant topic. Hydrogen used as a fuel, combined with hybridization was considered to be a very effective solution for urban vehicles such as small buses or light duty vehicles. In particular, series hybrid vehicles can use very small displacement engines as range extenders resulting in a noticeable fuel economy when considering urban cycles. Therefore, the development and testing of a small displacement, high thermal efficiency engine was the goal of this work. Hydrogen injection directly in the cylinder was considered to achieve these results and in effects this study mainly concerned about the injection and mixing processes in a directly injected, hydrogen fuelled single cylinder engine. Since commercial electro-injectors were considered, 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.