Parameter Scaling of the Aerodynamic Breakup of the Acoustic Levitated Droplets in an Air Jet Flow

The aerodynamic breakup of the droplet has been intensely studied in this paper.We aim to establish a unified relationship between dimensionless kinematic parameters such as displacement,spreading diameter,Weber num-ber,time,and so on.The breakup characteristics of the acoustic levitated ethanol droplet are experimentally inves-tigated when exposed to an air jetflow.The breakup phenomenons were recorded with a high-speed camera.The breakup characteristics were analyzed,and the physical models of the moving and transforming behaviors were established to explain the breakup mechanisms.We found that the displacement of the windward side of the dro-plet follows free acceleration rule,with the displacement,acceleration,and time in the dimensionless form.The spreading of the diameter during deformation can also be written in a simple equation as a function of Weber number and displacement.We also discussed more details.

Diffusion of a Nonvolatile Fuel Spray in Swirl Flow

The diffusion of fuel spray in swirl flow is vital for the combustion of diesel engine,however,the researches on this is still mysterious due to the obstacles on direct investigations on a real engine.The research of intake swirl in engine at present normally use CFD simulation or based on data analysis of combustion and exhaust emission,the specific mixing process of fuel in swirl flow still not very clear.In this paper,a rapid compression machine(RCM)with an optical combustion chamber was established with the mean compression velocity of 7.55 m/s.Three kinds of flow fields,including intense swirl field,weak swirl field and turbulent field,were conducted to investigate the diffusion characteristics of injected fuel,the mixing processes of fuel spray in the swirl flow fields were recorded by the high-speed camera.Experimental results show that the mixing of fuel spray in air consists of four stages:fuel injection,wall approaching,rapid diffusion and final diffusion.The fuel spray is firstly bended by the lateral flow of the swirl field,then liquid fuel is blown onto,and coats on,the sidewall.The fuel on the sidewall is finally enrolled into the chamber plenum afterwards in gaseous phase via the spiral arms(in swirl fields)or random routes(in turbulent field)At last the fuel disperses all over the chamber.The results give an intuitive observation and help better understand the air-fuel mixing process in diesel and direct inject gasoline engines.