Among the different efforts towards the reduction in pollutant emissions from direct injection (DI) diesel engines, the use of gaseous fuels as a partial supplement for diesel fuel has been proposed by many researchers. These engines are known as dual fuel engines. An experimental investigation was performed to investigate the influence of dual-fuel combustion on the performance and exhaust emissions of a DI diesel engine fueled with natural gas (NG) and biogas. In this work, the combustion pressure and the rate of heat release were evaluated experimentally in order to analyze the combustion characteristics and their effects on exhaust emissions including particulate matter (PM) for single-fuel (diesel) and dual fuel combustion modes. The use of NG as an alternative fuel is a promising solution.Biogas, on the other hand, is a renewable alternative fuel that has tremendous potential to be used in diesel engines especially in developing nations. Comparative results are presented revealing the effect of dual fuel combustion on engine performance and exhaust gaseous and PM emissions for the engine operating conditions considered in this study.

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This paper investigates a technique of calculating the completeness of combustion on a cycle- by-cycle basis. The technique introduces the normalized pressure rise due to the combustion parameter, ψ to describe the completeness of combustion. This parameter is based on the Rassweiler-Withrow method of calculating the mass fraction burned and is derived from the pressure-crank angle record of the engine. Experimental data were obtained from a Rover K4 optical access engine and analysed with a combustion analysis package. A computer simulation was then used to model the data on a cycle-by-cycle basis, both with and without the completeness of combustion parameter. The paper discusses the conditions under which it is suitable to model mean engine cycles, compared with the need to model cycle-by-cycle variability, and comments on the situations in which each type of modelling would be most appropriate. The engine simulation model is also used to investigate cycle-by-cycle variability of NO emissions that have recently been obtained experimentally. The successful aspects of this investigation are that the cycle-by-cycle variability in the completeness of combustion can be determined by use of the parameter ψ, that the inclusion of the completeness of combustion parameter improves the simulation's ability to model the experimental data both in a statistical sense (the coefficient of variation of the indicated mean effective pressure) and on a cycle-by-cycle basis and that cycle-by-cycle NO modelling results are found to compare well with experiment.