Evaluation of Diesel Engine Performance and Exhaust Emission Characteristics Using Biodiesel under Variable Operating Conditions

As environmental concern increases and fossil fuel reserves dwindle, biodiesel has emerged as an alternative sustainable, renewable, and biodegradable fuel to supply diesel engines.Amongst the various sources of raw materials used in biodiesel production, locally sourced sunflower oil presents a viable alternative, especially in countries experiencing problems with energy security and emission reduction, such as Iraq.In this work, the performance and emissions of four-cylinder direct injection diesel engine fueled with locally made Iraqi sunflower oil biodiesel were investigated.The biodiesel was produced with a transesterified reaction, and it was evaluated in blends as B20, B50 and pure (B100) in comparison to diesel fuel under several operating conditions of speed (1250-3000 rpm) and load (4.3-90 kN/m 2 ).Experimental results showed that the environmental impact of water injection was significant: CO emissions decreased by almost 50%, unburned hydrocarbons by 45% and carbon dioxide by 33%, without neglecting reduction of exhaust temperature and engine noise.On the other hand, the calorific value of biodiesel is lower than that for diesel and caused high Brake specific fuel consumption (BSFC) up to its peak at 12% for B100.NO x increased by about 21% as a result of improved oxygen availability and higher in cylinder temperatures.Among the blends studies, B20 demonstrated promising balancing of emissions reductions and thermal efficiency with no mechanical modifications.However, some limitations remain and should be explored in further studies.It is recommended to combine durability testing, techno-economic analysis and on-road tests in the future in order to fulfill international emission control legislations and for environment-friendly application of biodiesel in Iraq power and transportation services.