轻型汽油车蒸发排放特征及温度对蒸发排放的影响

Characteristics of Evaporative Emissions from Light-Duty Vehicles and Effects of Ambient Temperature on Evaporative Emissions of Light-Duty Vehicles

车辆蒸发排放是城市地区大气环境中VOCs(挥发性有机物)的重要人为源.选取满足国五排放标准的轻型汽油车,采用满足国Ⅵ(A)汽油标准的汽油,在密闭舱内设定两种不同温度,研究蒸发排放特征及温度对蒸发排放的影响.结果表明:①6辆车热浸VOCs蒸发排放因子范围为0. 01~0. 10 g/h,昼间损失VOCs蒸发排放因子范围为0. 09~1. 49 g/d,低于已有研究中国四或国三车辆的蒸发排放水平.②昼间损失VOCs蒸发排放水平远超过热浸VOCs蒸发排放水平.③热浸蒸发排放过程中密闭舱内VOCs质量呈近似线性增长,昼间损失蒸发排放过程中密闭舱内VOCs质量呈先快后缓的增长特征.④温度升高后,热浸和昼间损失VOCs蒸发排放因子均明显增加.温度由25℃升至38℃后,热浸VOCs蒸发排放因子增加36. 0%~533. 9%;温度从18~33℃升至23~38℃后,昼间损失VOCs蒸发排放因子增加16. 7%~106. 2%.研究显示,温度变化对热浸和昼间损失VOCs蒸发排放因子均影响明显.

Vehicle evaporative emissions are an important anthropogenic source of volatile organic compounds(VOCs)in urban atmospheric environments.To investigate the characteristics of evaporative emissions of light-duty vehicles and the influence of the key factor,namely,environmental temperature,on vehicle evaporation emissions,a series of hot soak and diurnal loss experiments were carried out in a sealed housing for evaporative emission determination(SHED)testing chamber using vehicles that met the national five emission standards and fuels that met the nationalⅥ(A)gasoline standards.The test results show that the amount of VOCs from hot soak evaporation was approximately 0.01-0.10 g/h,and the amount of VOCs from diurnal loss evaporation was between 0.09-1.49 g/d,which is lower than the VOCs released from vehicles that met the national four or three emission standards reported in other studies.The emission level of VOCs from diurnal loss was much higher than that from hot soak.The concentration of VOCs in the SHED testing apparatus during the hot soak evaporation process increased linearly,while the concentration of VOCs during the diurnal loss evaporation process showed rapid increase,followed by slow increase.The amount of VOCs from both hot soak and diurnal loss evaporative emissions increased after the environmental temperature in the SHED increased.When the temperature was raised from 25℃to 38℃,the VOCs evaporative emission factors from hot soak increased by 36.0%-533.9%.When the temperature was raised from 18-33℃to 23-38℃,the VOCs evaporative emission factors from diurnal loss increased from 16.7%-106.2%.This study showed that the temperature change had a significant effect on the evaporative emission levels in the process of both hot soak and diurnal loss.