Investigation On Performance Of Natural Gas/Diesel Oil Dual Fuel Engine

CNG/diesel dual fuel engine is a kind of engine that relies on natural gas as the main fuel and ignited by diesel engines, a small amount of diesel is injected to ignite the natural gas in the vicinity of the compression cylinder. In this paper, a diesel engine retained the electronic control system and fuel supply system and increased the natural gas supply system to be a dual fuel engine.Firstly the performance of the amount of diesel ignition and fuel injection pressure of dual fuel engine was researched. The more amount of diesel to ignite, the lower the rate of substitution was. The calorific value equivalent to fuel consumption and exhaust gas temperature were lower. Otherwise, the equivalent thermal efficiency and excess air ratio got higher. With the injection timing increases, the maximum explosion pressure showed a trend the development of" V ". The greater the amount of diesel ignition was, the higher the explosion pressure was. At low load, when the amount of diesel ignition got more, NOx, smoke and CH4 increased, but THC decreases. At high load, when the amount of diesel ignition got more, NOx emission was reduced, THC and smoke increased. When the injection pressure increased, the replacement rate, calorific value equivalent to the smaller fuel consumption and exhaust gas temperature decreased, and the excess air ratio, equivalent to the explosion pressure and the greater thermal efficiency increased. Within a certain range, the higher the rail pressure, the better the performance of the economy, the smaller the smoke, the less CH4 and HC emissions, but higher NOx emissions. When the pressure increased, the burst pressure increased, but also easy to knock. If the pressure was low, fuel atomization was poor, resulting in larger smoke and higher exhaust gas temperature.Secondly, the EGR and pre-injection on dual fuel engine was researched. When EGR rate increased, NOx emissions reduced, but HC, CO and CH4 increased. With the increase of the main injection angle, NOx emissions increased, but HC, CO and CH4 emissions decreased. When EGR rate was 20%, the equivalent to the thermal efficiency, the maximum rate of pressure rise, explosion pressure and the excess air ratio increased, but the exhaust temperature and heat value equivalent to the minimum fuel consumption decreased. With the increase of pre-injection angle, the calorific value equivalent to fuel consumption, the maximum rate of pressure rise and the exhaust temperature showed a trend of decrease and then increase. The equivalent thermal efficiency, pressure and excess air ratio showed a trend of increase and then decrease. When the amount of pre-injection increased, the pressure rise rate, exhaust gas temperature and maximum explosion pressure were greater. With the increase of pre-injection angles, NOx emissions reduced, HC, CO and CH4 emissions showed a trend of decrease and then increase slightly. With the increase amount of pre-injection, NOx emissions increased, the top of the NOx was greater, smoke was greater too, but HC, CO and CH4 smaller emissions decreased.