ID 165

Jet Breakup Dynamics in a Twin-jet Crossflow Airblast Atomizer

 

Abstract:

Airblast atomizers with radial injection of liquid fuel jets into crossflow of air find applications in gas turbine combustion, for instance, in Lean Premixed Prevaporized (LPP) combustors. Though significant research has been conducted on atomization of single liquid jets in cross flows air (typically in wind tunnels), the hole-to-hole variation in jet breakup in a multi-jet configuration has received less attention. The current research considers an airblast atomizer, which allows injection of two radially opposite liquid jets of water from a central tube into crossflow air in the annular passage such that the atomizing characteristics of the two liquid jets can be simultaneously studied based on high speed visualization. Experiments are performed for a range of aerodynamic Weber number (We) and liquid Reynolds number (Re) such that jet-wall interactions are always avoided. Interestingly, differences in the left and right jets are observed not only in the instantaneous jet breakup length but also‒depending on We and Re‒in the modes of jet breakup (either column or bag breakup). The mean and fluctuations of jet breakup length are measured. Proper Orthogonal Decomposition (POD) analysis of the jet breakup images is carried out to identify the dominant jet breakup modes and also to investigate the existence of any temporal correlation between the breakup modes of the left and the right jets. High speed images of the ligaments and droplets immediate downstream of the injector are also captured. An attempt is made to correlate the spray characteristics with primary breakup of the two jets.