The Effect Of Burned Residual Gases On Gasoline-NG Dual-Fuel Engine Combustion Performance With Skip-Fire Technique

Spark-ignition (SI) engines are commonly used to produce the power needed for various purposes. Using gasoline-NG dual fuel in these engines and investigating the variations of burned residual gas from the previous cycle in combustion cycles can improve engine operating conditions. The experimental data for the current study were obtained from a single-cylinder SI engine in various spark advances at the compression ratio of 10 and engine speed of 1800 rpm in dual-fuel mode (consisting of mass fraction of 75% gasoline and 25% NG) and stoichiometric equivalence ratio in both skip fire and non-skip fire conditions. The obtained raw data were processed using a computer code to arrive at the in-cylinder pressure versus crank angle diagram and the indicated mean effective pressure. The analysis of ensemble average cycle diagrams obtained from the experimental cycles in optimum spark advances indicated that the in-cylinder pressure variations before peak pressure were greater in skip fire conditions and the difference between optimum spark advances in skip fire and non-skip fire conditions was calculated to be 9 crank angle degree. Standard deviation and coefficient of variations for the indicated mean effective pressure were lower in skip fire conditions; in other words, fewer cyclic variations were observed in skip fire conditions. Furthermore, mass fraction burn variations were higher in skip fire conditions as compared to a non-skip fire condition, which was indicative of faster combustion in the former.