Effect of Multiple Injection Strategy on Atomization and Emission Reduction Characteristics in a Diesel-Ethanol Fueled Engine

The aim of this work is to investigate the effect of the multiple injections on the overall spray and the exhaust emissions characteristics in a common rail four cylinder diesel engine operated using diesel-ethanol blended fuels. In order to prevent the phase separation in blended fuels, biodiesel fuel that based on palm oil added to the blended fuels. The reduction problem of cetane number in blended fuels was supplemented by the addition of biodiesel fuel. The spray characteristics were analyzed through the spray images which obtained by the high speed camera. In addition, the combustion and exhaust emissions characteristics were measured and analyzed by using a four cylinder diesel engine with common rail injection system. It revealed that the increase of the injection interval induces the slow development rate of the second spray in the multiple injection modes. The spray cone angle of the single injection mode is wider than that of the multiple injection modes. The advance of the first injection timing caused the reduction of the second injection quantity, and the relaxation of the combustion pressure rise rate. NO_x emission shows a reduction trend by the increased ethanol blending ratio, while it shows an increasing pattern by the advance of the first injection timing at the fixed second injection. In HC and CO emissions, the short injection interval between the first and the second injections is better than long injection interval.