Comparative Studies of Methane and Propane as Engine Fuels

Abstract

The performance of a single-cylinder, high-speed, spark-ignition engine has been studied with gaseous methane and propane as fuels. The power output and thermal efficiencies have been determined at two compression ratios, 55/1 and loll. A comparison for the same engine using liquid fuels is given in Appendix I. Both fuels will knock at high compression ratios; the limits have been determined for all ignitable mixture ratios, and also the effect of inlet temperatures has been studied. Both fuels are 'temperature sensitive', the effect being most marked with methane. An experimental comparison has been made of the auto-ignition limits of both fuels by the motoredengine method. Both fuels have been shown to give a stable region of visible cool-flame-type pre-reaction below the temperature for complete ignition. Despite the differing ignition temperature and pressure relationship determined by static experiments, a close similarity is revealed by autoignition experiments in the engine. Possible explanations of the differing effects are considered. Infra-red absorption gas analysis has been used to detect the small quantities of methane in the exhaust gas surviving combustion. A very low and constant concentration of methane is present with fast-burning mixtures, owing, it is believed, to valve overlap and scavenge effects. As the rich and weak misture limits for steady running are approached unburnt methane increases in the exhaust, the effect being most marked near the weak limit. These effects are relevant to problems of atmospheric pollution from engixie exhausts, and also assist in assigning the fall in engine efficiency at weak mixtures primarily to combustion inefficiency.Both methane and propane are shown to be suitable fuels for high-compression-ratio gas engines. Consideration of the combustion properties of these two pure hydrocarbons of simple structure is also of interest in extending the understanding of the general problem of engine knock.

Numerical and experimental analysis on the effects of turbocharged compressed bio-methane-fueled automotive spark-ignition engine

“…Various engine parameters were identified such as in-cylinder pressure, brake thermal efficiency was found and compared to methane, the observations concluded that the Indicated Mean Effective Pressure (IMEP) for methane was reduced, at different loads and speeds compared to natural gas. Comparison of the performance between methane and propane characteristics was investigated by (Moore and Roy 1956). It was concluded that the maximum efficiency by utilisation of propane was greater than that of methane.…”