Effect of injection timing in multiple injections on NOx and smoke from CRDI diesel engine fueled with biodiesel blend

Abstract

Diesel engines with their high thermal efficiency and fuel economy are very much successful in commercial applications compared to their counterpart gasoline engines. The emissions like HC and CO from diesel engines are less compared to gasoline engines because they run mostly with lean mixtures. But due to heterogeneous combustion NOx and smoke emissions from Diesel engines is high. Due to contradicting requirements for the reduction of NOx and smoke, the tradeoff between NOx and smoke emission without compromising fuel economy is a big challenge being faced by automotive industries and researchers in the field. Also to have sustainable civilization, there is a need to find eco friendly and renewable alternative fuel to petro diesel to conserve fast depleting petroleum resources and to minimize environmental pollution. Biodiesel produced from non-edible feed stock is found to be a good alternative to petro diesel. It is observed that the formation of NOx is very much dependent on the peak temperature in the combustion chamber. Various types of techniques are being tried by the researchers to reduce high NOx emission from usage of biodiesel blended fuel in diesel engines. The techniques used are like dilution using EGR, injection of water, retardation of injection timing etc. With the development of CRDI systems split and multiple injection strategy attracting the attention of researchers as a promising technique in reducing the NOx emissions. In this work an attempt is made to study the effect of retardation of injection timing of a selected multiple injection with pilot-main-post strategy. The selected strategy is with 10% pilot fuel quantity with a dwell of 10 CAD and closely coupled fixed quantity of 0.5 mg post injection with 3 CAD after main injection. The main injection timing along with pilot and post was retarded from the recommended 23^o bTDC in steps of 3 degrees. It is observed that the combination of multiple injection and retardation of injection reduced NOx emissions effectively without compromising power output and thermal efficieny.