某高速汽油机改LNG发动机动力性下降问题研究

针对直接将汽油机改为LNG发动机导致的动力性下降问题,通过GT-Power与试验标定相结合的方法,提出了一种基于单因素法的高速LNG发动机配气相位优化方法:在降低泵气损失、减少缸内废气、提高充气效率的前提下,减小气门重叠角;针对优化后的配气相位,优化设计凸轮型线;同时根据LNG燃烧特性,在控制最高燃烧温度和压力的前提下,适当将点火提前角增大,合理组织燃烧,使燃烧更加及时完全,从而提高燃烧效率。结果表明,优化后的凸轮型线满足配气机构运动学动力学要求,高速LNG发动机最大功率较之优化前提高约7.9%,最低燃料消耗率降低约5.8%,此方法可以在一定程度上解决LNG发动机的动力性下降问题。

Power Reduction Problem of Retrofitted LNG Engine with High-Speed Gasoline Engine

To solve the power reduction problem caused by retrofitting gasoline engine as LNG engine ,a single factor design method of valve timing for high‐speed LNG engine was proposed by combining GT‐Power design and experimental calibration . The valve overlap was reduced on the premise of decreasing pumping loss ,reducing in‐cylinder exhaust gas and improving air charging efficiency .The cam profile was redesigned based on the optimized valve timing .Keeping the maximum combustion temperature and pressure unchanged ,the increase of ignition advance angle was conducted to make the combustion more timely and thoroughly according to LNG combustion characteristics ,thus the combustion efficiency improved .The results show that the optimized cam profile can meet the requirements of the kinematics and dynamic performance of valve mechanism .The in‐crease of maximum power and the decrease of lowest brake specific fuel consumption for high‐speed LNG engine are 7 .5% and 5 .8% respectively after the optimization ,which proves that the method can solve the power reduction problem to certain ex‐tent .