GTL燃料发动机排气颗粒数密度和粒径分布的试验研究

Measurements of Particle Number Concentration and Size Distribution from a GTL Fueled Engine

采用两级稀释取样装置和扫描迁移颗粒粒径分析仪(SMPS),研究了燃用天然气合成油(GTL)发动机排气颗粒的数密度和粒径分布特征,并同原柴油机的颗粒排放进行了比较,发现发动机燃用GTL时,中间转速(n=1400 r/min)下,排气颗粒多呈峰值粒径为50～80nm的单峰对数正态分布;高转速(n=2200r/min)下,呈分别包含核模态(峰值粒径为20～30nm)和积聚模态(峰值粒径为50～80nm)的双峰对数正态分布。而燃用柴油时,所有测试工况下,排气颗粒均呈包含核模态和积聚模态的双峰对数正态分布。与燃用柴油相比,怠速工况下,燃用GTL后总颗粒数密度和体积分数没有显著下降,而其它工况下总颗粒数密度和体积分数显著下降,其中总数密度均下降一个数量级,总体积分数下降20%～60%;燃用CTL后,排气中核模态数密度显著下降,某些工况下积聚模态数密度有所下降,这与GTL燃料中的芳香烃和硫含量均较低有关。

An investigation on the effect of gas to liquid （GTL） and diesel fuels on the particle number concentration and size distribution from a GTL fueled engine was conducted. Exhaust particle number concentration and size distribution were measured by a two-stage dilution system and an SMPS （scanning mobility particle sizer）. Particle number size distributions of GTL engine show unimodal and log-normal in form with an accumulation mode in the 50-80 nm diameter range at 1 400 r/min and bimodal and log-normal in form with a nucleation mode in the 20-30 nm diameter range and an accumulation mode in the 50-80 nm range at 2 200 r/min. Compared with diesel fuel, GTL shows substantial reduction in the total number and volume concentrations. The total particle number concentrations of engine fueled with GTL decrease by one order and the total particle volume concentrations decrease by 20%-60% and the number concentrations in the nucleation mode of engine fueled with GTL significantly decrease as well, and the number concentrations in the accumulation mode also decrease in some engine conditions, which are due to the lower fuel sulfur and aromatic compositions.