Investigations on the effect of diluents addition on engines behaviour of a biofuel based diesel engine under oxygen enriched combustion

Abstract

The growing concern on energy security due to the fast rate of fossil fuel depletion, their rise in cost and concern on environmental pollution has empowered the research all over the world towards the utilization of alternative fuels to petroleum derived fuels. Diesel engines are considered as the most important prime movers used in many applications which use conventional diesel oil as fuel. Vegetable oils are promising alternatives to diesel oil due to their very close resemblance to diesel. Among the vegetable oils, Mahua Oil (MO) looks as a promising alternative fuel which has great potential and attraction especially in India to use in Compression Ignition (CI) engines. However, its direct usage in compression ignition engines had disappointing results on performance and emissions because of its high viscosity, density and poor volatility. This work explored the use of neat MO efficiently without modifying the fuel by combusting it under oxygen enriched condition. The problem of increased nitric oxide (NO) emission with oxygen enrichment was controlled by addition of different diluents such as water, exhaust gas and carbon dioxide along with the intake air. A single cylinder, 4-stroke water-cooled, direct injection diesel engine was used for the entire work. Initially engine trials were made with Neat Diesel (ND) oil and neat MO with atmospheric oxygen concentration (i.e. 21% O2) in the intake air under varying engine power outputs such as 20%, 40%, 60%, 80%, and 100% power outputs for providing baseline data. In the second phase of work, the engine s intake system was modified to operate it under oxygen enriched condition. Engine experiments were carried out under enriched oxygen concentration in the intake air such as 22%, 23%, 24% and 25% by volume at 20%, 40%, 60%, 80%, and 100% (maximum power output) to obtain the optimized oxygen concentration for the best Brake Thermal Efficiency (BTE). In the third phase, Water Injection (WI) technique was tried for controllingNO emission under oxygen enrichment. 2