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In order to study the combustion process in a dual fuel direct injection compression ignition engine, a two-zone model has been developed. Two distinct zones of interest are gaseous fuel-air mixture zone and liquid pilot fuel zone. The present model uses methane as the main gaseous fuel. One of the problems which mostly occur in both part load and full load operating conditions of dual fuel engines is the onset of knock. The main target of this paper is the investigation of knock formation resources and effective parameters such as air-fuel equivalence ratio, initial temperature and injection timing. The numerical results have been compared with the experimental data of OM-355 direct injection dual fuel diesel engine and the work of other researchers.

The dual-fuel diesel engine (D.F.D.E) is a conventional diesel engine in which much of the energy released, hence power, comes from the combustion of gaseous fuel such as natural gas. The exhaust emission characteristics of the D.F.D.E needs further refinements, particularly in terms of reduction of Unburnt Hydrocarbons (UHC) and Carbon Monoxide (CO) emission, because the concentration of these pollutants are higher than the baseline diesel engine. Furthermore, the combustion process in a typical D.F.D.E tends to be complex, showing combination of the problems encountered both in diesel and spark ignition (S.I.) engines. In this work, a computer code has been modified for simulation of D.F.D.E combustion process. This model simulates D.F.D.E combustion by using a Multi-Zone Combustion Model (MZCM) for diesel pilot jet combustion and a conventional S.I. combustion model for modelling of combustion of premixed gas/air charge.