停缸对混氢汽油机怠速燃烧过程的影响

Effect of Cylinder Cutoff on Combustion Process of a Hydrogen-Enriched Gasoline Engine at Idle Conditions

通过一套自主开发的电控单元调整氢气和汽油的喷射脉宽,使氢气占进气的体积分数(φH2)由0%逐渐增加至6.5%左右,同时减少汽油的喷射脉宽,使工作缸中混合气的过量空气系数始终保持在1.0附近.通过该电控单元还可以切断指定气缸的氢气与汽油供给,从而实现停缸控制.试验结果表明,φH2相同时,停缸后发动机充气效率提高,火焰发展期与快速燃烧期有所缩短,怠速转速的循环变动系数减小,泵气损失降低.停缸和加大混氢体积分数均有利于减少发动机怠速时的传热损失及能量消耗量.在φH2为6.63%且两缸停止工作的条件下,发动机怠速能耗量较原机降低约40%.

A self-developed electronic control system was used to adjust hydrogen and gasoline injection durations.The hydrogen volume fraction in the intake（φH2）is increased from 0% to 6.5%.For a specified φH2,gasoline injection duration is reduced to keep the excess air ratio of the air-fuel mixture in working cylinders at the stoichiometric condition.Cylinder cutoff was realized by stopping the fuel supply to the specified cylinders through the electronic control unit.The test results demonstrated that,for a given φH2,engine volumetric efficiency is enhanced,flame development and propagation periods are short-ened,the coefficient of variation in engine idle speed is decreased,and pumping loss is reduced after cylinder cutoff.Both cylinder cutoff and hydrogen enrichment are effective on reducing cooling loss and engine fuel energy consumption at idle.At φH2=,6.63% and two-cylinders cutoff mode,fuel energy flow rate is decreased by about 40%,compared with that of the original engine.