Search Results

An experimental study was carried out to investigate the characteristics of cycle-by-cycle variations of combustion in a spark ignition engine. Cylinder pressure - crank angle histories of the 240 consecutive cycles were measured in the single cylinder by using a personal computer (IBM-PC AT) controlled data acquisition system which is developed for engine tests. From these data, a heat release analysis was performed for cycles and the averaged. It was observed that characteristics of the pressure and combustion rate related parameters varies with operating conditions such as air fuel ratio, ignition timing, and so on. Variation in early flame stage is the major cause for for the cycle-by-cycle variation of combustion. It was also noticed that the variation in early flame stage does not influence the mean effective pressure significantly in case of a rapid burn operation.

To improve the cold startability of methanol, methanol-butane mixed fuel was experimented. Engine performance and exhaust emissions are obtained with methanol-butane mixed fuel. These characteristics are compared with those of methanol and gasoline. The mixing ratios of methanol and butane are 50:50 (M50), 80:20 (M80), and 90:10 (M90) based on the calorific value. As a result, M90 produces more power than gasoline and more or less than methanol depending on the engine speed and the excess air ratio. Brake horse power of M90 is higher than that of gasoline by 5 - 10 %, and brake specific fuel consumption is smaller than that of gasoline by 17 % to the maximum based on the calorific value. NOx emission concentrations for M90 are lower than those for gasoline and higher than those for methanol because of the effect of butane, CO emission concentrations are somewhat lower than those for methanol and gasoline.