二冲程点燃式直喷重油发动机小负荷试验

Partial load tests on a two-stroke spark ignition direct injection heavy fuel engine

利用燃用轻柴油的二冲程点燃式空气辅助缸内直喷发动机,进行了转速为3 000r/min、节气门开度为10%与20%下的小负荷试验,研究了点火及喷油参数对发动机性能的影响。试验结果表明:当节气门开度较小时,采用上止点前30°~40°点火提前角,饱和点火能量,稀混合气(过量空气系数大于1.1)及适度提前混合物喷射结束时刻的策略能够充分改善发动机动力性和经济性。随着负荷增大,点火能量影响程度减小,采用适度推迟点火提前角,偏浓混合气(过量空气系数小于1.0)及提前喷射结束时刻策略,增加燃油蒸发时间来充分发挥发动机动力性能,而采用饱和点火能量,偏稀混合气(过量空气系数大于1.15)能够大幅度改善发动机经济性及HC/CO排放。

The partial load tests at the engine speed of 3000 r/min and 10%,20% throttle open positions were carried out on a two-stroke spark ignition diesel-fuelled engine with air-assisted direct injection,and the effects of ignition and injection parameters on the engine performance were investigated.The tests results indicated that,at the small throttle open position,applying the strategies of the ignition timing at 30°-40°crank angle before top dead center,the saturated ignition energy,the partial lean mixture（excess-air-ratio above 1.1）and the suitable injection timing can fully improve the engine power output and fuel economy.With the increase of engine load,the effects of the ignition energy reduced.Applying the strategies of the moderate delayed ignition timing,the partial rich mixture（excessair-ratio below 1.0）and advancing the end of injection timing to increase the fuel evaporation time resulted in a remarkable engine power output.Furthermore,the fuel economy and HC/CO emissions of the engine improved greatly by the use of the saturated ignition energy and the partial lean mixture（excess-air-ratio above 1.15）.