Single-Cylinder SI Engine Performance in Dual-Fuel (Gasoline-NG) Mode with Gasoline Dominant Fuel under Stoichiometric Conditions

The advantages and disadvantages of using gasoline and NG as single-fuel is a challenge for researchers in development of SI engines. Singular utilization of these fuels results in some advantages and disadvantages from economics, thermodynamics, pollution and development aspects and make it difficult to prefer one to the other. Assuming that using combination of the fuels can modify the output results, in the present research, different combinations of 100, 90, 75 and 60% gasoline and the rest of natural gas, designated as G100, G90, G75 and G60, were investigated in a SI single-cylinder engine at running at 1800rpm, 9 compression ratio and stoichiometric equivalence ratio. After collecting and processing in-cylinder experimental data in the combinations and different spark advances and their experimental data processing, consecutive cycle-to-cycle data were extracted and analyzed with engine output data. First, optimum spark advance of each combination was determined and then, the combinations were compared at their spark advances. The results revealed that increasing natural gas fraction in combination causes substantial reductions in standard deviation, σ, and coefficient of variation, COV of IMEP, so that σ and COV of G60 reduced by 51.6% and 49.2%, respectively, in comparison with G100. Reducing the gasoline presence in combination, the amount of CO2, NOx and HC reduced except G90 which have the higher HC and NOx, whereas, CO amount in G90 decreased to the lowest level. Also, no satisfactory performance was observed in the G90 combination.