Volatile organic compounds (VOCs) from a State-Ill diesel engine are analyzed by thermal de-gorption-gas chromatography-mass spectrometry (TD-GC-MS). Over 90 kinds of VOCs are detected from the exhaust gas of a State-Ill diesel engine under different speeds and loads. The test results indicate that aromatic hydrocarbons, including benzene, toluene, p-xylene, m-xylene, o-xylene, ethylbenzene, styrene, naphthalene etc. have higher emissions, among which the highest is toluene. Under the same speed with the increase of engine load, the styrene emission reduces while the emissions of other aromatic hydrocarbons show a trend of fall first and then rise. The emissions of most aromatic hydrocarbons fall with the rise of engine speed at low-medium load range and have only negligible changes with different engine speeds at high load.%采用热脱附-气相色谱-质谱联用技术(TD-CC-MS)对国3柴油机排气中的挥发性有机物进行了分析.在国3柴油机不同转速和负荷下的排气中定性检出烷烃、烯烃、芳香烃等90余种挥发性有机物,且在VOC8中以碳数C5-C20的化合物为主,其中C8化合物排放比例最高,为9.81％～15.41％.试验结果表明,芳香烃中的苯、甲苯、对二甲苯、间二甲苯、邻二甲苯、乙苯、苯乙烯、萘等排放量较高,其中排放水平最高的为甲苯；在相同转速下,苯乙烯的排放随着发动机负荷的增加而降低；而其他芳香烃则随着柴油机负荷的增加呈先降后增的变化趋势；在相同负荷下,多数芳香烃在中低负荷时随着发动机转速的增加而降低,但在高负荷时随发动机转速增加变化幅度很小.
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