Numerical study of twin-spark plug arrangement effects on flame, combustion and emissions of a medium compression ratio direct-injection methanol engine

The effects of twin-spark plug arrangement on flame, combustion and emissions of a medium compression ratio direct injection methanol engine were numerically investigated. Computational results showed that at approximately A (ratio of distance of twin-spark plug and cylinder diameter) = 0.65, the burning and exothermic were the most reasonable compared to other twin-spark plug locations. A = 1.00 was the worst twin-spark plug arrangement. The maximum in-cylinder pressure and the maximum in-cylinder temperature were decreased with increasing A. Ignition delay were increased with increasing A. The A = 0.65 had the shortest combustion duration and the maximum heat release rate. The maximum in-cylinder pressure of A = 1.00 was approximately 57.5% lower than A = 0.25. The ignition delay of A = 1.00 was approximately 2.4 times longer than A = 0.25. The combustion duration of A = 0.67 was approximately 12% and 52.2% lower than A = 0.25 and A = 1.00, respectively. Unburned methanol and soot were increased gradually with increasing A, and at the A > 0.75, the unburned methanol and soot emissions were increased rapidly as increasing A. The unburned methanol of A = 1.00 was approximately 4.6 times higher than A = 0.25. The variations in emitted NOx emissions showed opposite tendencies with the variations in unburned methanol and soot emissions. The optimum arrangement of the twin-spark plug for application of actual engine was approximately A = 0.65.