Abstract

MBARAWA, M.  and  MILTON, B.E.. An Examination of the Maximum Possible Natural Gas Substitution for Diesel Fuel in a Direct Injected Diesel Engine. R&D j. (Matieland, Online) [online]. 2005, vol.21, pp.3-9. ISSN 2309-8988.

In recent years, much attention has been focused on the application of alternative gaseous fuels, particularly natural gas (NG), to diesel engines. This is due to the promising results obtained from the research on NG as an internal combustion engine fuel throughout the world which has shown that there is potential for minimizing air pollution and noise by replacing diesel fuel in existing engines by NG fuel. For partial substitution of diesel fuel with NG fuel in a diesel engine, a mixed combustion process called dual-fuelling approach has been adopted. Dual fuelling is the method whereby an alternative gaseous fuel such as NG is induced into the cylinder as a primary fuel, with air, and is subsequently ignited with a pilot injection of diesel fuel. Extensive tests on emissions, performance and different amounts of NG substitution in a direct injection (DI) diesel engine have been carried out for both diesel fuel only and dual fuel (DF) operations. The results show that 86 % NG could be substituted for diesel fuel at low speeds over the whole load range. Maximum NG operation showed higher carbon monoxide (CO) emissions than the diesel fuel only operation while smoke was reduced with DF operation. The maximum values of smoke emission were 30 Hatridge smoke numbers (HSN) with the maximum NG and 28.5 HSN in diesel fuel only operation.

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