Experimental Investigation of Atomization of Water Jets in Air Streams

Atomization is a process by which a volume of liquid is converted spray. This process includes the breakup of the liquid jet or the liquid sheet exiting the injector. This paper has experimentally investigated the models and mechanisms for the breakup of the liquid jet and the liquid sheet formed by the jets impingement in a still environment and in an environment with counter flow, coflow, and cross flow. Also, the effects of the impingement angle, injector diameter, and jet length before impingement on the formation of the liquid sheet have been explored. Imaging has been employed to investigate different patterns formed by these interactions. To produce water jets, injectors with 0.4 and 0.9 mm diameters at a velocity range of 1-33 m/s and in accordance with Reynolds numbers between 3,000 and 30,000 have been used. It was found that in the low flow speed range, the water jet breaks up by the Riley's breakup model. While in high speed range, the breakup model is the firstwind - induced breakup model. The measured breakup length has a very good agreement with the result of Sallam’s equation. In investigating the breakup of liquid jets in cross flow, six breakup models were observed, including Rayleigh-like, turbulent, column, bag, multimode and shear breakup models. Also, in paper, an equation has been presented for the penetration of water jet into an air counter flow. Through a qualitative comparison of the images taken from the impingement of two water jets, velocity and Reynolds number ranges of the closed rim, alternating drops, open rim, and fully-developed models were determined. It was observed that, by increasing pre- impingement length of a jet, the instabilities on the liquid sheet increase.