Energy & Fuels 2009, 23, 719–724
719
Effect of Port Fuel Injection of Methanol on the Combustion Characteristics and Emissions of Gas-to-Liquid-Fueled Engines Xingcai Lu,* Tao Wu, Libin Ji, Junjun Ma, and Zhen Huang School of Mechanical and Power Engineering, Key Laboratory for Power Machinery and Engineering of the Ministry of Education, Shanghai Jiao Tong UniVersity, Shanghai 200240, People’s Republic of China ReceiVed September 28, 2008. ReVised Manuscript ReceiVed NoVember 25, 2008
A large number of published papers reveal that gas-to-liquid (GTL) fuel has the potential for reducing the particulate matter (PM), CO, and hydrocarbon (HC) emissions to a certain degree, and NOx emissions can also be reduced by optimizing the engine parameters or at a larger exhaust gas recirculation (EGR) rate. To reduce the PM and NOx emissions simultaneously on a larger scale, an experiment was conducted of GTL combustion and emissions on a single-cylinder diesel engine with the port fuel injection (PFI) of methanol. The results revealed that, because of the lower cetane number and larger latent evaporation heat value of methanol, the ignition timing delayed clearly, the maximum in-cylinder gas pressure decreased, and the maximum heat release rate increased with the PFI of methanol. At a lower to medium overall equivalence ratio, the maximum in-cylinder gas temperature decreased linearly with the increase of the premixed ratio of methanol. At a large overall equivalence ratio, the maximum gas temperature decreased on a small scale at first and then began to increase in a small magnitude with the increase of the methanol addition. With regard to the regulated emissions, both CO and HC emissions increased with the addition of methanol. However, it was interesting to note that a tradeoff relationship of PM and NOx was changed by PFI of methanol, the NOx emissions could be reduced by 85-98%, and the smoke opacity decreased by 50-62% in overall operating ranges.
Because of their excellent drivability and high economic feasibility, diesel engines have been widely used as the power sources for many commercial transportation vehicles. However, for the last 20 years, there have been major social problems relating to the air pollution and greenhouse effect, which have been caused by the engine emissions and other contributors. As a result, the increasingly severe emission standards, such as EURO 5 and Tier 2 of the U.S.A. have been imposed on the traditional light- and heavy-duty diesel engines. Therefore, worldwide efforts have been channeled into the formulation of environmentally friendly diesel fuels able to meet the advanced fuel specifications of the 21st century. A variety of feedstocks, including coal, natural gas, and biomass can be converted into liquid fuels by using the Fischer-Tropsch (F-T) catalytic conversion process. Gas-to-liquid (GTL) fuel, produced from natural gas and features high cetane number (>75), low or freesulfur specification (
