甲醇-生物柴油对发动机循环变动的影响

在单缸柴油机上通过测量得到了燃用不同掺混比甲醇-生物柴油时的燃烧示功图,对不同柴油机工况下甲醇-生物柴油燃烧的循环变动进行了研究,分析了最大压力升高率循环变动系数(COV_((dp/dφ)max))、平均指示压力循环变动系数(COV_(pmi))、最高燃烧压力的变动系数(COV_(pmax))、最高燃烧压力对应曲轴转角的标准偏差(SD_(φpmax))等循环变动的评价参数。研究结果表明:工况一定时,随着甲醇掺混比增加,COV_((dp/dφ)max),COV_(pmi)等循环变动系数均有所增大;与生物柴油相比,甲醇掺混比为10%和20%时循环变动系数变化较小,当甲醇掺混比为30%时,COV_((dp/dφ)max)增加了6.2%,COV_(pmi)增加了24.2%,COV_(φpmax)增加了8.4%;当甲醇掺混比不变时,随着转速的增加,COV_((dp/dφ)max)降低,COV_(pmi)以及COV_(pmax)先降低后增高;负荷增加时,各压力参数的循环变动系数均降低,SD_(φpmax)略微上升。

Effects of Methanol/Biodiesel on Engine Cyclic Variation

The combustion indicator diagrams were measured on a single cylinder diesel engine fueled with different blended fuels of diesel and methanol .The combustion cyclic variation of blended fuel was studied under different conditions ,which ana-lyzed the evaluation parameters of cyclic variation such as the maximum pressure rise rate coefficient COV (dp /dφ)max the mean in-dicated pressure coefficient COVpmi ,the maximum combustion pressure coefficient COVpmax and the standard error of its corre-sponding crank angle SDφpmax .The results show that COV (dp /dφ)max and COVpmi increase with the increase of methanol mixing ratio .Compared with biodiesel ,the changes of cyclic variation coefficients are smaller when the mixing ratios are 10% and 20% .When the mixing ratio of methanol increases to 30% ,the COV (dp /dφ)max increases by 6 .2% ,COVpmi increases by 24 .2% , and COV pmax increases by 8 .4% .For the constant mixing ratio ,COV (dp /dφ)max decreases and COVpmi and COVpmax first decrease and then increase with the increase of speed .With the increase of load ,the cyclic variation coefficients of all pressure parame-ters decrease ,but the corresponding standard error of maximum combustion pressure slightly increases .