掺混标准氢氧气对汽油机性能的影响

针对汽油机部分负荷条件下热效率低和有害排放高的问题, 笔者在一台加装了电控氢、氧气喷射系统的四缸汽油机上研究了掺混标准氢氧气对汽油机燃烧与排放特性的影响.标准氢氧气定义为氢气与氧气物质的量比为2∶1的氢氧气.试验时, 通过调整氢气和氧气喷嘴的喷射脉宽, 使标准氢氧气占进气的体积分数 (α_2H2/O2) 由0分别增加至2%和4%, 并减少汽油的喷射脉宽, 使混合气的过量空气系数由1.00增加至1.50.结果表明:掺入标准氢氧气能改善汽油机经济性, 发动机比燃料能量消耗率最低值由原机的12.63 MJ/kW·h分别降低至α_2H2/O2为2%和4%时的12.27 MJ/kW·h和12.11 MJ/kW·h;此外, 掺入标准氢氧气后, 汽油机滞燃期及快速燃烧持续期缩短, 最大压力升高率提高, HC及CO排放降低, 但NO_x排放明显增加.

Effect of Standard Hydroxygen Addition on the Performance of a Gasoline Engine

The gasoline engines usually encounter the dropped thermal efficiency and adversely increased toxic emissions at part load conditions.This paper investigated the effect of standard hydroxygen addition on the performance of a gasoline engine.The standard hydroxygen is defined as the hydroxygen with a hydrogen-to-oxygen mole ratio of 2∶1.The experiment was carried out on a four cylinder gasoline engine equipped with an electronically controlled hydrogen and oxygen injection system.During the experiment, the volume fraction of the standard hydroxygen in the total intake was raised from 0 to 2% and 4% by adjusting the injection durations of hydrogen and oxygen, respectively.The gasoline injection duration was reduced to enable the global excess air ratio of in-cylinder charge to increase from 1.00 to 1.50.The test results showed that the addition of standard hydroxygen availed improving the engine fuel economy.The lowest brake specific energy consumption rate was decreased from 12.63 MJ/kW·h to 12.27 MJ/kW·h and 12.11 MJ/kW·h of the 2% and 4% standard hydroxygen-blended gasoline engines, respectively.Moreover, it was also found that the flame development and propagation periods were shortened, the peak cylinder pressure rise rate was enhanced, HC and CO emissions were reduced whereas NO_x emissions were increased after the standard hydroxygen addition.