A study on the nitrogen oxides reduction using the low temperature combustion for compression ignition engines fueled with DME

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.This study describes the spray, combustion and exhaust emission characteristics of dimethyl-ether (DME) fuel a various exhaust gas recirculation rate (EGR). Especially, the high EGR rate was applied to reduce the nitrogen oxides (NOx) in the low temperature combustion conditions. Spray characteristics such as spray tip penetration, spray cone angle and tip velocity were investigated using the DME spray image analysis which obtained from the spray visualization system including high speed camera and constant volume chamber Combustion and exhaust emissions characteristics acquired from the DME fueled single cylinder diesel engine an emission gas analyzer, respectively. It was revealed that DME spray bad higher tip velocity than ULSD at the same injection condition; however, the reduction rate of tip velocity of DME was fast due to the evaporation. DME fuel bad short ignition delay when comparing ULSD however, the application of EGR make the ignition delay o DME extended. In addition, EGR reduced the oxygen concentration in the engine cylinder. With higher EGR, the peak combustion pressure and the rate of heat release rat slightly increased, and combustion phasing was retarded ao slower heat release was observed. DME combustion exhausted lower soot and NOx emissions than ULSD, and it showed similar or slightly lower HC and CO emissions. The application of EGR significantly reduced NOx emission, however, the soot emission showed negligible increment. In addition, HC and C emissions were increased slightly by EGR due to the reduction of oxygen concentration and low cylinder temperature.