Injector Geometry Effect on Plain Jet Airblast Atomisation

Abstract

Airblast atomisation drop size is a function of the liquid and gas flow conditions. It is also subject to the atomisation geometry, or more specifically the jet breakup mechanism. Plain jet atomisation featuring coaxial air and fuel flows has been investigated to assess the injector geometry effect on the spray characteristics. Results from various flow conditions and atomiser configurations suggest that a prompt atomisation correlation that was evaluated for prefilming injectors can be applied to plain jet airblast atomisation, in a slightly modified form. Changes in the velocity term are necessary to fit the measured data. A scaling factor has been established to compensate for the velocity term change. This factor may also imply the underlying difference between flat sheet and round jet atomisation. The liquid atomisation mode is dependent not only on the manner of geometrical air-liquid contact but also on flow conditions. In this study, the combined air-fuel velocity ratio VR and Weber number (WeVR) is found to be a criteria that determines the air flow pattern influence on atomisation. Data from this experiment show that a small change in the axial distance between the liquid jet and air orifice entrance results in marked difference in spray drop mean size under low air momentum flow conditions.

Experimental Study of the Effect of the Expansion Segment Geometry on the Atomization of a Plain-Jet Airblast Atomizer

“…In resent year, several geometrical parametric of the plain-jet airblast atomizer has been studied by Paul and Srdihara. The investigation shows the axial distance between the liquid jet and air orifice entrance results in marked difference in spray drop mean size under low air momentum flow conditions [10], and the liquid postrecess in the air nozzle cavity leads to increased drop sizes with the convergent exit and has little effect with the straight exit [11]. Charalampous et al study the breakup length of liquid jets in airblast atomizers using different measuring method [12].…”