Influence of Ambient Air Pressure on Pressure-Swirl Atomization

Abstract

The spray characteristics of six simplex atomizers are examined in a pressure vessel using a standard light diffraction technique. Attention is focused on the effects of liquid properties, nozzle flow number, spray cone angle, and ambient air pressure on mean drop size and drop-size distribution. For all nozzles and all liquids it is found that continuous increase in air pressure above the normal atmospheric value causes the SMD to first increase up to a maximum value and then decline. An explanation for this characteristic is provided in terms of the measurement technique employed and the various competing influences on the overall atomization process. The basic effect of an increase in air pressure is to improve atomization, but this trend is opposed by contraction of the spray angle which reduces the relative velocity between the drops and the surrounding air, and also increases the possibility of droplet coalescence.

Prediction of drop size distribution in a spray from a pressure swirl atomizer using maximum entropy formalism

“…The input values and the corresponding atomizer hydrodynamic parameters correspond to the data given by Wang and Lefebvre [10]. F ollowing the analysis of maximum entropy formalism, F ig.…”

“…All these functions are based on certain parameters, which are assumed by considering the nature of the spray. F or example, in the R osin-R ammler distribution a size parameter and a dispersion parameter are involved, where the dispersion parameter typically varies between 2 and 4 for a spray from pressure swirl nozzles [10]. H owever, any such prescription is rather ad hoc, based on empirical evidence and provides no physical link between the atomization parameters and the resulting spray characteristics.…”

On the Development of Spray Submodels Based on Droplet Size Moments

“…The Rosin-Rammler mean radius is the droplet radius for which 63% of the liquid mass is made up of droplets with smaller radii. The shape of the distribution is determined by the exponent, and the majority of sprays have distributions with exponents between the values of 2 and 4, and mostly at the lower end of this range, as reported by Wang and Lefebvre [19]. Thus the shape was chosen to match a Rosin-Rammler distribution of exponent 2.…”

A numerical study of water mist mitigation of tunnel fires

“…The shape of the distribution is determined by the exponent, and the majority of sprays have distributions with exponents between the values of 2 and 4, most commonly at the lower end of this range [19]. However, droplet moments using the Rosin-Rammler distribution of exponent two cannot be analytically integrated.…”