The influence of air side and fuel side water addition on engine’s behaviour of a biofuel based compresion ingnition engine under oxygen enriched combustion

Abstract

The effect of water injection at the air side and water addition at fuel side on engine?s performance of a Diesel engine was studied under oxygen enriched intake air using neat mahua oil as fuel. Initially experiments were carried out using neat mahua oil as fuel with different oxygen concentrations such as 21% (ambient), 22.4%, 23.8%, and 24.7% by volume at the air side. The optimal oxygen concentration was found based on the engine?s brake thermal efficiency. At the optimal oxygen concentration water injection was done on air side at 4% by mass and the experiments were repeated with neat mahua oil as fuel under oxygen enrichment mode. Finally, mahua oil emulsion was prepared using the same amount of water (i. e. 4%) and tested in the engine. A comparative study was made for the same amount of water (i. e. 4% as optimal) for water injection and neat mahua oil emulsion on engines behavior. Oxygen enrichment increased the brake thermal efficiency with all concentrations and reached the maximum value from 25.2% with ambient oxygen to a maximum of 30.6% at 23.8% of oxygen enrichment at the maximum brake mean effective pressure of 5.4 bar whereas it was 30.8% with neat diesel. The smoke, HC, and CO emissions were significantly reduced with oxygen enrichment. However, oxygen enrichment increased the NO emissions at all concentrations. Injection of water and emulsification techniques reduced the NO emissions considerably. Emulsification showed more reduction in NO emission than water injection for the same amount of water. It was concluded from the study that neat mahua oil could be effective used as fuel in compression ignition engines by combusting it under oxygen enriched condition. The optimal oxygen concentration of 23.8% could be recommended for the highest brake thermal efficiency. Injection of water at the intake manifold and emulsification techniques could solve the problem of higher NO emissions. The optimal amount of water that could be injected without affecting the engines power and brake thermal efficiency could be recommended as 4% by volume. Emulsification has the added advantage of further improvement in engine?s brake thermal efficiency.