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The purpose of this study was to examine the cause of fluctuations in combustion. It is important to understand the changes that occur in flame kernel development and in flame propagation during cyclic variation. In this study, a comparison was made between time-series variations in OH emission with THC concentration, and the intensity of the combustion reaction and the direction of flame propagation are also discussed. Early flame development and cyclic variation at an early stage of combustion were demonstrated by simultaneously measuring a two-dimensional image of flame emission and the time-series variation of local flame emission. The instantaneous intensity at Cassegrain measurement point agreed with the intensity of time-series variation in local flame propagation at CCD recorded timing. Variations in THC concentration in the cylinder were compared with time-series variations in local flame emission.

The purpose of this study is to examine the cause of combustion fluctuation in a partially loaded two-stroke engine with respect to the hydrocarbon (HC) concentration in the cylinder. HC concentration in the cylinder, exhaust gas velocity and pressure were simultaneously measured in order to determine the influence of HC concentration on combustion fluctuation. A correlation between cyclic variation in HC concentration in the cylinder and IMEP was confirmed. The way in which the HC concentration influenced the combustion states in the next cycle made clear. A decrease of HC concentration cause the delay of early flame development and combustion, the decrease of HC concentration had an great influence on the combustion states. The relationship between combustion states and HC concentration was discussed. The relative value of IMEP and HC concentration were closely related to the HC concentration in the cylinder.

The purpose of this study was to detect a misfiring cycle in terms of the transfer-passage and the exhaust-pipe flow rate by experimental measurements. Simultaneous measurements of flow rates and in-cylinder pressure were carried out. The flow rate data were grouped into the different combustion classes by the in-cylinder pressure. A large flow rate of exhaust blow-down and a large reverse flow rate were observed in the cycle before misfiring, compared with in the cycle before firing. It showed that high concentration of the residual burnt gas in the cylinder was the main source of misfiring, this feature was also demonstrated by the complementary measurement of CO and CO2 concentrations.