Air Assisted Direct Cylinder Barrel Injection of Gasoline in a Two-Stroke S.I. Engine

This experimental study was aimed at improving a two-stroke S.I engine by injecting gasoline with air assistance through the cylinder barrel. Experimentally obtained performance and emission parameters of the engine at 25% and 100% throttle positions were analyzed at 3000 rpm. The timing of air assisted injection was optimized at 25% throttle and 3000 rpm. The performance and emissions of the engine were compared with those obtained with an optimized manifold injection system. In all cases the best spark timing was used. At 25% throttle although the thermal efficiency was increased only slightly, there was a significant reduction in HC emissions to 6.63 g/kW-h with cylinder barrel injection from 10.69 g/kW-h with manifold injection due to reduced short circuiting of the fuel. There was a reduction in NO emissions as well with cylinder barrel injection. Comparisons were made at the point of highest thermal efficiency at 100% throttle also. Since short circuiting is more dominant at high throttle conditions, better improvements in performance were observed at 100% throttle. The highest thermal efficiency was 20.1% with cylinder barrel injection compared to 18% with manifold injection. Significant reductions in HC emissions were also observed. The air fuel ratio based on the inducted air and injected fuel was also higher with cylinder barrel injection indicating reduced short circuiting losses. On the whole it was observed that air assisted direct cylinder barrel injection could be a viable option to improve the performance of a two stroke engine.