Breakup of colliding droplets and particles produced by heavy fuel oil pyrolysis

Heavy fuel oil (HFO) obtained by blending oil refinery residue and cutter stock is actively used as fuel in marine engines and industrial boilers. However, the use of HFO presents a number of unresolved problems. In the lack of oxidizer, pyrolysis of HFO droplets in the flame core produces solid particles, and the fuel combustion temperature drops, increasing the solid phase concentration in the combustion chamber. This study investigates the water/HFO fragmentation behavior as the emulsion droplets collide with solid particles produced by their pyrolysis. According to the experimental findings, droplet-particle collisions can occur in two regimes: spreading and separation. A two-fold increase in the droplet to particle size ratio shifts the critical Weber number towards 10–20% higher values. To ensure the consistent separation regime with 2.5-mm droplets, the velocities should be 15–30% lower than with droplets of about 1 mm in radius. Larger particle size leads to a 20–30% increase in the resultant water/HFO droplet velocity. The research findings indicate that the arrangement of atomizers at an angle of less than 10° to each other will reduce the cost of thermal and electric energy production by almost 10%. [Display omitted] •Doubling the droplet to particle size ratio causes a 10–20% increase in critical We•An increase in droplet size from 1 mm to 2.5 mm reduces critical velocity by 15–30%.•20–40% larger particle size causes a 20–30% increase in droplet velocity.•Approx. 10° is the optical angle for atomizer arrangement.•An equation predicts transition boundaries between spreading and separation.