A theoretical and experimental study on the effects of water steam injection on NOx emissions of direct injection diesel engine running with different biodiesel blends

Diesel fuel can be considered as a non-renewable fuel and will probably last for a limited period of time. By taking into account of high content of harmful emissions, challenges and high costs in gathering-transporting processes, there is an increasing need to develop new sources that could be alternatives to diesel fuels. In this regard, biofuels are seen as an alternative for diesel fuel owing to renewability, biodegradability and generating acceptable quality exhaust gases. The biggest penalty of biofuels, which are much more environmental friendly than conventional diesel in many aspects, is the increase in NOx emissions due to high level oxygen content. NOx emissions are tried to be controlled by international agencies such as European Union, IMO and US EPA with increasingly tightened regulations because of their harmful effects on human and environmental health.In this study, effects of water steam injection to the intake manifold of a single cylinder diesel engine to performance and emissions are investigated by experimentally and theoretically, in order to control the high NOx emissions originated from biofuels. In the experimental work, which is conducted in full load conditions, three different types of methyl esters are used in mixture with diesel fuel (10%, 20% by mass), and performance and emission changes are observed by injection of variable ratios of water steam (10%, 20%, 30%). Meanwhile the theoretical study covers modeling of combustion of three different types of methyl esters with single and two zone combustion models, results derived from this work are validated with experimental values.