Prediction of the ignition limits of alcohol-hydrocarbon mixtures

An experimental program was undertaken to determine the effects of hydrocarbon additives on the ignition limits of alcohol fuels using methanol-isopentane and methanol-toluene mixtures. A fixed volume of the liquid fuel mixture, chosen to limit the change in liquid composition caused by differential vaporization, was introduced into a combustion bomb apparatus. The liquid was temperature-equilibrated to achieve an equilibrium fuel-vapor/air stoichiometry. A spark in the vapor volume provided the energy for ignition. Results of the ignition limit experiments for both the methanol-isopentane and methanol-toluene mixtures demonstrate that the mixture ignition limits can be predicted from a knowledge of the individual fuel limits and the vapor-liquid equilibrium composition of the mixture. The average difference between the predicted and measured temperature ignition limits for both fuel mixtures was 1.7 C. Both the experimental procedures used to obtain the ignition limits of the mixtures and the methodology used to predict the ignition limits of the mixtures are discussed.