Theoretical investigation of engine thermal efficiency, adiabatic flame temperature, NOx emission and combustion-related parameters for different oxygenated fuels

This paper deals with theoretical investigation of engine thermal efficiency, specific heat at constant pressure (Cp), gas temperature, molecular number, adiabatic flame temperature, oxides of nitrogen (NOx) emission, and some fundamental combustion-related parameters such as theoretical air fuel ratio (AFR), lower calorific value (LCV) and ratio of LCV and theoretical AFR for different oxygenated fuels. The computations are carried out at standard atmospheric condition. Pentadecane (PD) was used as a base fuel in this computation. The results showed that almost all of the above combustion-related parameters are closely related to oxygen content in the fuels. The ratio of LCV and theoretical AFR is constant for all kinds of oxygenated fuels regardless of the oxygen content in their molecular structure. One of the interesting findings of this work is that with the increase in oxygen content in the fuels adiabatic flame temperature decreases linearly consequently NOx emission decreased linearly. The engine thermal efficiency is almost unchanged below oxygen content of 30% w/w, but gradually decreased above 30% w/w. The reduction in NOx emission is associated with the reduction in adiabatic flame temperature for the oxygenated fuels, while the reduction of engine thermal efficiency above 30% w/w of oxygen associated with the increase in gas specific heat.