Novel Technique for Measurements of Continuous Liquid Jet Core in an Atomizer

A novel optical method is proposed for the measurement of the length of the continuous liquid jet core in atomizers. Laser light is directed through the injecting nozzle to illuminate internally the liquid jet, which acts as an optical fiber transmitting the laser beam. The continuous core of the liquid jet is visualized by means of laser-induced fluorescence, generated by the addition of dye in the liquid. The instantaneous continuous length of the liquid jet is measured as the distance from the nozzle exit, where the emitted laser-induced fluorescence intensity from the liquid jet becomes negligibly small due to interruption of laser light transmission through the liquid jet following the liquid jet breakup. The method provides a nonintrusive measurement approach, promising improved measurements in dense sprays, where droplets obstruct the illumination and the imaging path of shadowgraphic techniques. Measurements in an air-blast atomizer showed that the continuous liquid length measured by the novel approach is systematically shorter than that measured by shadowgraphy. As such, existing empirical correlations for the breakup length, which have been mainly measured by shadowgraphy, may need to be revisited.