An Investigation of the Injection Properties in a Direct Injection Natural Gas Engine

Direct injection of natural gas into the cylinder of spark ignition internal combustion engines has shown a great potential for better fuel economy and lower emissions. Since the technology is rather new, different aspects of the in cylinder flow have not been investigated completely. Injection process is one of the most important aspects of the flow field inside cylinder, as it controls the mixing of fuel and air. Low gas density, high injection pressure, short injection duration and very small injector nozzle diameters make injection investigations quite critical. In this study, multidimensional modeling of direct natural gas injection and mixing process has been performed using AVL FIRE software. In this regard, grid resolution strategy and required grid size as well as overall fuel jet shape have been evaluated through a validation case study. Finally, the validated model has been used to investigate the injection in a direct injection engine cylinder. In this regard, a centrally mounted inwardly-opening single-hole injector has been adapted to all cases. The effect of engine speed has been investigated on the flow field via quantitative and qualitative representation of the results. Based on the results, a discussion has been made on mixing and injection properties.

An Investigation of the Injection Properties in a Direct Injection Natural Gas Engine Keywords:

natural gas , direct injection , internal combustion engine , multidimensional modeling