In order to meet increasingly stringent emission regulations, especially the restrictions on diesel engine particulate and NO emissions, seeking measures that can simultaneously reduce NO and particulate emissions has become an important topic in internal combustion engine research. For diesel engines, it is usually used to delay fuel injection, increase fuel injection rate, high pressure injection, common rail injection system, pilot injection, multiple injection, premixed compression ignition, EGR (exhaust gas recirculation) and exhaust gas aftertreatment technology to reduce NO and particulate emissions. It is an effective way for diesel engines to use alternative fuels to reduce particulate and NO emissions. The application of alcohol fuels (such as methanol, ethanol) to diesel engines can significantly reduce NO and particulate emissions. *New research has found that dimethyl ether is a more suitable alternative fuel for diesel engines. The test results of AMOCO and Hal-Dimethyl ether on a variety of diesel engines show that dimethyl ether can achieve engine high efficiency, ultra-low emissions, soft and smokeless combustion, and can meet the most stringent European III and California Of ultra-low emission vehicles. The performance and combustion characteristics of the engine fueled with dimethyl ether are studied, and the influence of the main parameters of the combustion system on the engine performance is studied.
Fuel characteristics (1) Dimethyl ether is the simplest ether compound with molecular formula 3. The main physical and chemical properties of dimethyl ether and diesel are compared. There are only CH and CO bonds in the molecular structure of dimethyl ether, and no CC bonds. In addition, it is an oxygen-containing fuel, which helps to reduce the smoke and particles generated by combustion; at the same time, it can use a greater exhaust gas recirculation rate (EGR) , To reduce NO emissions. (2) The low calorific value of dimethyl ether is only 64.7% of diesel. In order to achieve the power of diesel engine, the circulating fuel supply of dimethyl ether must be increased. (3) The cetane number of dimethyl ether is higher than that of diesel and much higher than other alternative fuels. Therefore, it is not necessary to take combustion-supporting measures when using dimethyl ether in diesel engines. (4) The saturated vapor pressure of dimethyl ether at normal temperature and pressure is 0.5MPa. As the temperature increases, its saturated vapor pressure increases. In order to prevent the occurrence of air lock phenomenon, the pressure of the fuel supply system is much higher than that of the diesel fuel supply system. 2% castor oil is added to dimethyl ether to increase the lubricity of the fuel, but pure dimethyl ether is used in the emission test to eliminate the influence of lubricants on emissions.
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