Potential improvement in conventional diesel combustion mode on a common rail direct injection diesel engine with PODE/WCO blend as a high reactive fuel to achieve effective Soot-NOx trade-off

Abstract

Many countries in and around the world have conducted various studies on biodiesel usage over common rail direct injection (CRDI) diesel engines, among which waste cooking oil (WCO) biodiesel has made a major impact on diesel engine research because of its cost-efficient nature and elimination of waste disposal. The deposits of carbon and very high viscosity are some of the key factors which deteriorate the usage of raw WCO biodiesel. Lower volume proportionate blends of WCO biodiesel produce excellent combustion characteristics reducing hydrocarbon (HC), carbon mono oxide (CO), and soot emissions, but they seem to promote the formation of nitrous oxides (NOx). As a solution to overcome this problem, polyoxymethylene dimethyl ether (PODE) with lower viscosity, higher oxygen content, high cetane number, showing better combustion characteristics with a good soot-NOx trade-off is selected for the present research work. The novelty of the current research work shows the reduction of soot and NOx emissions using PODE/WCO/Diesel blends by varying the proportions in a conventional combustion mode of a CRDI diesel engine without any modifications which was lagging by the previous researches. A trans-esterified WCO biodiesel is blended with diesel in varying volumes as 10, 20, and 30%. The chemical properties of the blend fuels were determined using ASTM standards. The investigation was carried out and it was found that W20 blend fuel showed a highest reduction of 21.11%, 23.51%, and 22.45% of CO, HC, and soot emissions respectively with a rise of 6.39% of NOx emissions. W20 blend with a good soot-NOx trade-off was selected in which PODE was blended in varying proportions such as 10, 20, and 30% respectively. The properties of the test fuels were determined and the further investigation was carried out. This second stage of reduction was done in determining the fuel with excellent soot-NOx trade-off without compromising the performance of the engine. It was found that W20P20 blend fuel showed the highest reduction of 33.86%, 50.78%, and 80.86% of HC, CO, and Soot emissions with a slight increase of 0.78% of NOx emissions. Brake Thermal Efficiency was found better for W20P20 fuel in comparison with W20 fuel. Thus, two stages of reduction in emissions were carried out with the aim of meeting the stringent emissions norms in the conventional diesel combustion technique.