Dynamic behaviors of heavy oil droplets impacting solid surfaces and liquid films

The carbonaceous deposition on the outer surface of cyclone separator's vortex finder is primarily caused by the impact and deposition of heavy oil droplets on the solid surface. A glycerol-anhydrous ethanol solution with physical properties similar to heavy oil droplets was used as the research object, this study simulates the impact between heavy oil droplets and surfaces/liquid films under different temperature conditions. Experiments combined with the CLSVOF method reveal that reducing droplet contact time on surfaces inhibits deposition. This can be achieved by increasing the contact angle, decreasing droplet viscosity, increasing the initial impact velocity of the droplets, reducing droplet diameter, and creating appropriate microstructures on the solid surface to split the droplets into several smaller droplets upon impact. For droplet-liquid film interactions, increasing the Weber number (We), decreasing the Ohnesorge number (Oh), and optimizing film thickness promote secondary droplet formation, thereby inhibiting carbonaceous deposition. However, once the liquid film reaches a certain thickness, further increases have little effect on the splash behaviors. Moreover, the influence of different surface microstructures on splash morphology and characteristic parameters can be neglected. Based on dimensionless parameters such as We, Re, Oh, and h*, a predictive model for the critical conditions of splashing during the impact of heavy oil droplets on liquid films is proposed: Wec·Oh^-0.4 = 1000 h*.