The Effect of Compression Ratio on Small Two Stroke Cycle Spark Ignition Engine Fueled Methanol Containing Water

对小型二冲程循环火花点火发动机进行了实验研究，实验中甲醇的含水量分别为0%、10%和20%。特别地，我们用应变式压力计测量了气缸内的压力变化。发动机转速恒定（2200rpm）。产出率0.4（恒定）。压缩比（CR）发生变化（CR=7.1、7.7、8.4）。在此条件下，进行了变过剩空气比（EAR）发动机性能试验。本研究的实验结果如下：(1)在丰富的混合物中，使用甲醇含量高达20%的水的最大输出功率与使用纯甲醇的最大功率大致相等。但在稀混合气中，最大输出功率随含水率的增加而减小。(2)随着含水率的增加，着火时滞增大，但燃烧持续时间不变。然后MBT（最佳转矩最小提前量）减小。(3)在高压缩比工况下，以含水甲醇为燃料的发动机热效率和输出功率略有提高。MBT也降低了，可燃混合物区域也减小了。

We Studied on small two stroke cycle spark ignition engines fueled methanol contains 0%, 10% and 20% volume of water. Especially, we measured pressure change in the cylinder using strain-type pressure gage. Engine speed is constant(2200rpm). Delivery ratio is 0.4(constant). And compression ratio(CR)is changed(CR=7.1, 7.7 and 8.4). Under these condition, engine performance test was carried out, with variable excess air ratio(EAR).Experimental results in this investigation are following(1)At rich mixture, maximum output power using methanol contents up to 20% of water is approximately equal to maximum power using neat methanol. But, at lean mixture, maximum output power is decreased as the water contents rate increases.(2)As the water contents rate increases, ignition time lag is increased, but burning duration is not change. Then MBT(Minimum advance for Best Torque) isdecreased.(3)Under high compression ratio condition, thermal efficiency and output power or engines fueled methanol containing water is slightly increased. MBT is also decreased, and flammable mixture region is reduced.