Diesel injection strategies for reducing emissions and enhancing the performance of a methanol based dual fuel stationary engine

Abstract

The effect of injection strategies of diesel on combustion, performance and emissions of a single cylinder, light duty, common rail, and methanol-diesel dual fuel engine were investigated. Methanol was port injected and experiments were carried out at a speed of 1500 rpm, brake mean effective pressure of 4.3 bar (75% rated load) and methanol to diesel energy share of about 50%. The directly injected diesel was first introduced as a single pulse, then as two pulses – Pilot and main injection and finally as three pulses – pilot, main and post injection. Single pulse injection of diesel resulted in delayed combustion which lowered the combustion stability and brake thermal efficiency. With the pilot main injection strategy combustion rate, peak combustion temperature and combustion stability were enhanced due to increased charge reactivity. Further, hydrocarbon and carbon monoxide emissions were reduced due to the complete combustion of methanol. The pilot with main and post injection strategy could reduce the rate of pressure rise, Nitric oxide levels and average in-cylinder temperature as compared to the pilot main injection mode. Through proper selection of the quantity and timing of the post injected diesel (1.25 mg/cycle and 5°crank angle after top dead center) which is employed along with pilot and main injections, a significant reduction in Hydrocarbon, Carbon mono-oxide, Nitric oxide and Soot emissions with good combustion stability and low ringing index could be achieved in the dual fuel mode.