Experimental Investigations on the Effects of Water Injection in a Light Duty Diesel Engine Operated with Biodiesel Fuel

In-cylinder emission control methods for simultaneous reduction of oxides of nitrogen (NOx) and particulate matter (PM) are gaining attention due to stringent emission targets and the higher cost of aftertreatment systems. Alongside there is a renewed interest to use carbon neutral biodiesel due to global warming concerns with fossil diesel. In the present work, the effects of water injection on the performance and emission characteristics of a light duty diesel engine operated with Karanja biodiesel are investigated. Considering the corrosive effects of water at higher concentrations, 3, 6, and 9% water by mass is injected by varying the pulse width of a low-pressure port fuel injector. Experiments were conducted at a rated speed of 1500 rpm under varying load conditions. The results obtained are compared with neat biodiesel as reference fuel. There are no significant differences in the peak pressure and the peak heat release rates with and without water injection. However, there is a marginal improvement in the brake thermal efficiency with a maximum increase of 1.5%. The brake specific fuel consumption increases at low load by 6%, however, it decreases by 3% at high load. The NOx emissions are reduced by a maximum of 19% with 9% water injection at full load. At low loads, the variations in smoke emissions with and without water injection are insignificant, however, it reduces at high loads by 25% with 9% water injection. Overall, the present study shows that water injection has a potential to reduce NOx and smoke emissions simultaneously along with better engine performance. The scientific reasons behind the benefits obtained with water injection are discussed in detail in the manuscript.