Characteristics of liquid ethanol diffusion flames from mini tube nozzles

A series of experiments was conducted to explore the combustion characteristics of a diffusion flames from mini tubes fueled by liquid ethanol with visual observations of the flame shape, the dynamic liquid–vapor interface during phase change inside the capillary tubes and the tube outer surface temperature using CCD and IR cameras. As the fuel supply rate increased, the interface location rose to the tube exit and the temperature gradient on the outer tube surface increased, consequently the evaporating became much stronger and the interface tended to be unstable. The combustion characteristics are closely related to the rapid phase change and violent evaporation and interfacial dynamics, with the violent evaporation, actually explosive boiling, inducing an explosive flame. The intensity of the explosive flame became stronger as the flowrate increased with the maximum flame height, interface location movement, and sound intensity all significantly increasing. The periodicity of the explosive flame was directly proportional to the interface moving distance and inversely proportional to the fuel flow rate.