EGR率对生物柴油颗粒纳米结构的影响

为研究同时运用废气再循环(EGR)技术和燃用生物柴油对柴油机排气颗粒纳米结构的影响，分别采集0%，15%，30% EGR率下186F柴油机燃用生物柴油时的排气颗粒，并用激光拉曼光谱仪测得颗粒光谱，使用五带法对一阶拉曼光谱进行拟合，分析拟合曲线参数，计算颗粒微晶尺寸和碳碳键长度。结果表明：EGR率为30%时，生物柴油颗粒光谱的半高宽(FWHM)最大，代表化学异相性最强并且颗粒中的物质种类最多，随着EGR率降低，半高宽逐渐减小；当EGR率从0%升高到30%，I_D/I_G逐渐增大，代表石墨化程度降低，颗粒中的石墨结构减少；同时，I_D1/I_D2从0% EGR率的8左右降低到15%和30% EGR率的4左右，代表EGR率升高，颗粒内部缺陷由空位缺陷向石墨烯边缘缺陷发展；随着EGR率升高，微晶尺寸逐渐减小，碳碳键长度基本不变。

Impact of EGR Rate on Soot Nanostructure from a Diesel Engine Fueled with Biodiesel

A specific nanostructure analysis was performed on the soot derived from diesel engine fueled with biodiesel under different rate of exhaust gas.The experimental instruments used in this study included an 186FA engine bench,a full-flow dilution constant volume sampling system,and a laser Rarnan spectrometer.In the engine bench test,biodiesel soot under several EGR rates were collected from the exhaust gas with the Micro-Orifice Uniform Deposit Impactor (MOUDI).Then,a laser Raman spectrometer was utilized in order to explore the nanostructure of biodiesel soot.The first-order Raman spectra have been analyzed by curve fit with five band combination and the obtained spectral parameters were discussed.The results revealed that 30％ EGR rate had the widest FWHM representing strongest chemical heterogeneity and most material types in biodiesel soot,next was 15％ EGR rate,and no EGR was the last.While EGR rate climbed from 0 to 30％,ID/IG gradually increased,which suggested that ordered graphitic structure reduce and the degree of graphitization decreased.In addition,ID1/ID2 were located about from 8 of 0％ EGR to 4 of 15％ and 30％ EGR,suggesting a general transformation from vacancy defect to defect at graphene layer edges.Furthermore,crystallite dimension reduced when EGR rate raised.However,C-C bond length seemed no fluctuation.Besides,there was no obvious difference of C-C bond length between biodiesel soot and typical carbon graphite.In summary,the nanostructure of biodiesel soot under high EGR rate tended to have low degree of graphitization and high oxidative reactivity.