An experiment was carried out on a four-cylinder spark-ignited (SI) gasoline engine to investigate the effect of hydrogen addition on the engine performance at low idle speed conditions. The engine was run at three idle speeds of 800 r/min, 700 r/min and 600 r/min. At the specified idle speed and stoichiometric conditions, the hydrogen volumetric fraction in the total intake was gradually increased from 0 to about 6%. The experimental results showed that the engine fuel energy flow rate was.reduced from 30. 8 MJ/h at the idle speed of 800 r/min and a hydrogen volumetric fraction in the intake of 0 to 18. 6 MJ/h at the idle speed of 600 r/min and a hydrogen volumetric fraction in the intake of 6. 0%. For different idle speeds, the engine combustion duration was shortened, cyclic variation was eased and HC, CO and N0x emissions were decreased with the increase of hydrogen volumetric fraction in the intake. All in all, the addition of hydrogen was effective for enhancing the engine performance at tow idle speed conditions.%在一台加装了电控氢气喷射系统的四缸汽油机上,试验研究了混氢对发动机低怠速性能的影响.在怠速转速不变、维持进气混合气处于当量比的条件下,在1～6％的范围内逐渐增加氢气在总进气中的体积分数,测试了发动机转速分别为800、700、600 r/min时的低怠速性能.试验结果表明,纯汽油机怠速为800 r/min时,发动机稳定运行的燃料能量流量Ef为30.8 MJ/h,而当混氢分数增加至6.1％、怠速转速降至600 r/min时,Ef降低至18.6 MJ/h；随迸气混氢体积分数的提高,发动机低怠速时的燃烧持续期缩短,HC、CO及NOx排放量降低,循环变动也减小.可见,进气掺氢可有效改善发动机的低怠速性能.
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