ID 282

Effect of ambient density on single drop breakup - Experimental study

 

Abstract:

Secondary atomization has been the subject of interest for many research groups - the most curious manifestation is found in the nature in the form of rain drops. While there have been several experimental studies at ambient conditions which involve real-world density ratios (R = ρliq / ρgas > 500), most of the numerical investigations have been at much lower density ratios (R < 50). The current study aims to conduct single drop breakup experiments at low density ratios – conditions which are found in most operating conditions in gas turbine engines. The experimental setup is designed to comprise primarily of a high-pressure chamber (up to 15 bar), which houses both a mono-disperse drop generator and a contoured nozzle to produce the required air jet. The chamber also has optical windows suitably placed for visualization using shadowgraph imaging, high speed imaging and drop sizing with the aid of long-distance-microscope (LDM). The prominent parameter that characterizes secondary breakup, namely the aerodynamic Weber number (We), is varied by controlling the air jet velocity. Elevating the chamber pressure results in lower R, which is lowered up to ~70. Though Rayleigh-Taylor instabilities are suspected to dominate the breakup physics at low We regimes and high R, it is interesting to study the effect of lower R on the breakup phenomena at similar range of We. The change in density ratio, especially on the lower side exhibits a different behaviour during the drop breakup process.