Experimental Study Of Compression Ignition Engine Operated With DME Fuel

Because of its high thermal efficiency and reliability, diesel engine is wide used. But with develop of human society and economy, traditional diesel engine have to face the problem such as lack of fossil fuel, environmental pollution. So develop new clean energy sources to reduce NOx and PM emission is very important.Dimethyl ether (DME) have high cetane number, is fit to compression ignition. Traditional diesel engine just reform fuel supply system and then it could burn DME. DME have high percentage of oxygen, so it could burn with large EGR ratio, and its latent heat of vaporization is high, this could reduce the highest burn temperature, all of these could reduce NOx emission of engine. Molecular structure of DME do not have C-C bond, so combustion of DME process almost have no PM emission. So DME is acceptable alternative fuel for diesel engine. But its characteristics such as low calorific value, viscosity make it could not use in diesel engine directly.This paper reform fuel supply system of a turbocharged diesel engine and research the influence of injector open pressure, advance angle of fuel supply, and diameter of spray orifice to dynamical performance and emission. And emission of DME engine in ESC experiment is measured. In order to reduce NOx emission, exhaust gas recycle (EGR) system is developed. The influence of EGR to DME engine performance is researched. This paper measure pressure of cylinder in different condition, and analyze combustion characteristic of DME.This paper make six experiment scheme to research the influence of injector open pressure, advance angle of fuel supply, and diameter of spray orifice to engine performance. Comparing emission and dynamical performance,8℃A advance angle of fuel supply,16MPa injector open pressure,0.38mm diameter of spray orifice is suitable for DME. And emission of DME engine is lower than Europe III emission standard.In order to reduce NOx emission, EGR system with cooler is developed. Comparing experiment data, low EGR ratio could make that emission of DME engine lower than Europe IV emission standard. And dynamical performance of engine have a low decline. The fuel consumption of DME engine almost the same as that there is no EGR at low load and rise 1% to 3% at heavy load.Though measure in-cylinder pressure, heat release rate curve is calculated, transient heat release rate and combustion duration is researched. Premixing combustion of DME is little. Diffusion combustion of DME take a large percentage in the combustion process and burning velocity of diffusion combustion of DME is quick.