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Burning natural gas in a direct injection diesel engine, requires a special arrangement to secure ignition. In this study a hot surface assisted ignition concept is investigated in a constant volume combustion bomb and a test engine with the objective to develop a better understanding of the mechanisms involved. The experiments show that surface temperature above 1200 K is required to achieve acceptable ignition, strongly dependant on natural gas composition and system parameters such as injection and hot surface geometry. A mathematical model of the concept is also being developed. Numerical simulations combined with experiments allow us to look closer into the processes, and to expand the test matrix even outside the physical limits of the test engine. This paper will give an outline of the investigation including some results from experiments and numerical simulations.

Variable composition of natural gas depending on the gas source causes variable ignition and combustion properties when used as fuel in internal combustion engines. Ignition and combustion problems lead to reduced efficiency, increased levels of emissions, as well as increased mechanical and thermal loads on engine components. The main objective of this study is to investigate the influence of natural gas composition on ignition properties in a direct injection hot surface assisted compression ignition engine. Previous investigations have shown that ignition of methane require hot surface temperature in the range of 1200-1400 K in order to obtain an ignition delay within 2 milliseconds. Pure methane and several natural gas mixtures have been tested under various conditions in a constant volume combustion bomb and in a test engine. Ignition delay and cycle to cycle variations are used to compare the combustion qualities of the different gas.