Experimental Investigation of Oil Film Flow and Droplets Behavior in the Annular Channel of a Cyclone Separator

•The liquid film was in the form of many slant streams in the middle region of the annular channel.•Four types of droplet impact outcomes were observed in the annular channel.•The impact outcomes were shown to undergo a transition from bouncing to coalescence as the droplet Weber number increased.•The transition boundary from bouncing to coalescence was 2500 under different liquid volume fractions.