Influence of Different Compositions of Natural Gas on Engine Performance

The increasing environmental concern, the demographic and economic growth of the emerging economies and the progressive reduction in the world reserves of crude oil forced the transportation sector to consider the use of alternative fuels (natural gas and hydrogen enriched methane) and renewable sources (bio-gases). The processes employed for biogas production are responsible for blends made up by different percentages of methane, CO, H2 and inert gases. Such a variety results into a wide range of heating values as well as chemical and physical properties and inevitably affects the engine combustion process and performance. The present paper investigates the effect of different fuel blends (G20, G25 and HCNG30) on the performance of a 1.4 litre spark ignition engine and specifically it aims at highlighting the need for an algorithm to be implemented in the engine ECU and capable to identify the mixture composition so as to set the proper engine control parameters. Improved combustion behaviour was achieved when hydrogen was added to methane with the drawbacks of reduced engine exhaust temperatures and increased in-cylinder pressure. G25 operations were in turn characterized by a decrease in the engine power output associated with the replacement of methane with inert gases.