In order to meet the increasingly stringent emission regulations, particularly the restrictions on diesel particulate and NO emissions, the search for measures that can simultaneously reduce NO and particulate emissions has become an important issue for internal combustion engine research. For diesel engines, the use of delayed injection, increased fuel injection rates, high pressure injection, common rail injection systems, pilot injection, multiple injections, premixed compression ignition, EGR, and exhaust aftertreatment techniques are commonly used NO and particulate emissions. The use of alternative fuels for diesel engines to reduce particulate and NO emissions is an effective way. Applying alcohol fuels such as methanol and ethanol on diesel engines can significantly reduce NO and particulate emissions. Recent studies have found that DME is an alternative fuel that is more suitable for diesel engines. The results of dimethyl ether combustion tests conducted by AMOCO and Hal-different diesel engines show that dimethyl ether can achieve high efficiency, ultra-low emission, gentle and smokeless combustion of the engine and can meet the most severe European III and California standards. Ultra-low emission vehicle. The performance and combustion characteristics of the engine when using dimethyl ether were studied, and the influence of the main parameters of the combustion system on the engine performance was studied.
Fuel Characteristics (1) Dimethyl ether is the simplest ether compound with a molecular formula of 3. The main physical and chemical characteristics of dimethyl ether and diesel were compared. The molecular structure of dimethyl ether has only CH and CO bonds, no CC bonds, and it is an oxygenated fuel, which helps to reduce the smoke and particles generated by combustion. At the same time, it can use a larger exhaust gas recirculation rate (EGR). Reduce NO emissions. (2) The low calorific value of dimethyl ether is only 64.7% of that of diesel fuel. In order to achieve the dynamic performance of the diesel engine, it is necessary to increase the circulating fuel supply of dimethyl ether. (3) The cetane number of dimethyl ether is higher than that of diesel fuel, which is much higher than other alternative fuels. Therefore, it is not necessary to adopt combustion-supporting measures when diesel engine is used for dimethyl ether. (4) The saturated vapor pressure of dimethyl ether at normal temperature and pressure is 0.5 MPa. As the temperature increases, the saturated vapor pressure increases. In order to prevent air resistance from occurring, the fuel supply system pressure is much higher than the diesel fuel supply system. Adding 2% of castor oil to dimethyl ether increases the lubricity of the fuel, but pure dimethyl ether is used in the emissions test to eliminate the effect of the lubricant on emissions.