Investigation On The Emission Characteristics Of Volatile Organic Compounds From A Passenger Car Driven By Gasoline-Engine

Volatile organic compounds (VOCs) are one of the primary exhaust pollutants from gasoline engines, in which polycyclic aromatic hydrocarbons (PAHs), carbonyls and alkene emissions have been proven carcinogenic. By right of the tiny diameters of VOCs, they can penetrate into the alveolus and infiltrate into blood, resulting in various diseases and the adverse effects on human health. At the same time, they are also act as precursors of atmospheric photochemistry smog and pollute the atmospheric environment. It is necessary to investigate intensively on VOCs from gasoline-driven cars and will be helpful and useful to abate the exhaust emissions.The experiments were carried out according to NEDC on a passenger car driven by gasoline engine which meet EURO III standard. The emission characteristics of VOCs, including the PAHs, before and after the catalyst were studied under the condition of EUDC, cold- and hot- start. Meanwhile, the concentration distributions of ultra-fine particles (UFPs) were also investigated at the start and the whole test procedure. The major conclusions are listed in the follows:1. Abundant VOCs were emitted at start stage, and their concentrations could reach 10000 ppm. At the same stage, the catalytic efficiencies were exceedingly low, while it went up sharply after 40s and the catalytic efficiencies were above 90% for all kinds of VOCs.2. The aromatic hydrocarbons were dominant in the VOC emissions from gasoline engine, which the chemical property of aromatic hydrocarbon and their contents in gasoline fuel have an effect on. Trimethylbenzene, xylene, toluene were majority in aromatic hydrocarbons.3. Except that the polycyclic aromatic hydrocarbons (PAH) with more than 4 benzene rings were solid state, most of PAHs emitted existed with gas state and parts existed with both gas and solid. At running process, the mass of gaseous PAHs with fewer benzene rings were more than 99% in the total PAHs.4. At the start test procedure, a great deal of UFPs emitted from gasoline engine was detected. Especially, at start idle and accelerating period the number concentration was ten times more than that at other test periods.5. The catalyst was effective on the reduction in the volume and area concentrations of UFPs, but poor on the reduction in number concentration. The main reason was that the catalytic efficiency was lower for the UFPs with 0.04-0.12μm.