In case of using biodiesel to fuel compression ignition engines, there is a decrease in effective power of the engine by 5 ... 15%, but with concomitant reduction in the amounts of polluting gases (CO, CO 2 , HC). The currently researches and also the solutions proposed regarding the external conditioning process of fuel or fuel-air mixture (trough ultrasounds) aimed at improving overall performance of the engine, the functional characteristics (primarily engine power and efficiency), increasing speed of chemical reactions and, consequently, reduces the duration of burning, acting on some physico-chemical properties of the fuel in a controlled manner. This paper presents an originally and novelty CFD simulation study on temporal development inside a diesel engine combustion chamber of a fuel injection process using a biodiesel fuel conditioned trough ultrasounds. It shows the values of Combustion Equivalence Ratio (CER) variations for the ultrasonic conditioned biodiesel. In the horizontal section of the combustion chamber, according to data obtained by simulation, it is apparent that for the case of biodiesel ultrasonic conditioned injection, the occupied area by the fuel-air mixture is 6.77% higher than when using biodiesel classic unconditioned. In the case of biodiesel conditioning exist an area that is characterized by a higher CER = 1.4-2.0, occupying 11% of mixture total area. A lower value of the mixture area in the combustion chamber of CERs = 0.8-1.4 (for biodiesel ultrasonic conditioned), lead to influence the burning process by a lower value of the adiabatic flame temperature, which determinate lower values of NO x emissions resulting from the combustion process. A lower value of the area air-fuel mixture all available surface relative to the combustion chamber (in the case of ultrasonic conditioning) increase the premix phase of combustion and realize further increase the diffusion phase of combustion that conduct to reduced emissions of NO x . Taking into account the complex nature of the interaction of ultrasounds with liquid media and their action at the molecular level of biodiesel, further studies are needed to determine the effect on diesel engine functional parameters, the level of pollutants emissions and to confirm the above obtained results trough experimental researches.

CFD simulation, biodiesel, external conditioning, ultrasounds, combustion equivalence ratio

Presentation: oral