Experimental study on the combustion characteristics of a high speed direct injection diesel engine fuelled with natural gas

Experimental results are provided concerning the combustion of natural gas in a compression ignition environment, where the liquid diesel fuel is partially replaced by natural gas injected into the intake air. The investigation was conducted on a single cylinder, naturally aspirated, high speed direct injection diesel engine, modified to operate under dual fuel conditions. Results are given revealing the effect of liquid fuel percentage replacement by natural gas on the engine performance (i.e. cylinder pressure, total heat release rate, total brake specific energy consumption) and the main combustion characteristics (i.e. duration of combustion, ignition delay, etc.). By comparing the results, an important effect of the presence of natural gas is observed. Taking into account that the experimental measurements cover a very wide range of natural gas supplement ratios (0-90%) without any appearance of knocking phenomena, the belief is strengthened that the findings of the present work are extremely valuable if it is opted to apply this technology to existing direct injection diesel engines.