The effect of ethanol as a biodiesel fuel additive on the performance and emissions of a dual-fuel diesel engine

Investigating the effects of pilot fuel containing low percentages of ethanol and water in the diesel-biodiesel fuel mixture in a dual-fuel combustion process with natural gas can have favorable results on the performance and emissions of a diesel engine. In the present study, three levels of ethanol (0, 2, and 4%), two levels of biodiesel (0 and 5%), and four levels of water (0, 0.3, 0.6, and 0.9%) were mixed with diesel fuel. All these fuel samples were considered as pilot fuel in the dual fuel combustion process with an 80% natural gas replacement percentage. Based on the obtained results, the presence of water, ethanol, and the combination of water-ethanol and natural gas can improve the diesel engine's performance by increasing the combustion chamber pressure and reducing the pollutants. The presence of oxygen content in ethanol can improve the combustion process by pushing the combustion toward complete combustion. The results of the optimization using the response surface method showed that the optimal point of engine performance at full load with a fuel sample containing biodiesel in the amount of 2.5 ml, ethanol in the amount of 11.5 ml, water in the amount of 9.3 ml and gas fuel occurs in 65%. Under this condition, compared to the control sample, the braking power increased by about 79%, and the specific fuel consumption decreased by about 58%. This fuel sample reduced the amounts of carbon monoxide, carbon dioxide, nitrogen oxides, and energy production costs by 54, 33, 29, and 39%, respectively, and increased sulfur oxides by 11%.