Spray volume distribution pattern

For a fixed-orifice conventional hydraulic pressure nozzle operating with a given spray liquid, the only way in which flow rate through the nozzle can be changed is by varying the pressure at the nozzle. However, variations in operating pressure result in changes to both the spray volume distribution pattern (pattemation), the droplet size (spray quality) and velocity distributions (see Table 4.2). 

Characteristics of the spray are measured by laser diffraction and analyzed with Fraunhofer diffraction equation, so that the optical properties of the spray are not necessary for the analysis. The device is called HELOS by Sympatec with a measuring range from 0.5 to 175 pm at that lens configuration. The analysis of the diffraction patterns of several drops with different size is mathematically complex and done by the Software of Sympatec, WINDOX . Thus a cumulative volume distribution of the spray, or drop size distribution (DSD), is measured. 

Hollow Sprays. Most atomizers that impart swid to the Hquid tend to produce a cone-shaped hoUow spray. Although swid atomizers can produce varying degrees of hoUowness in the spray pattern, they aU seem to exhibit similar spray dynamic features. For example, detailed measurements made with simplex, duplex, dual-orifice, and pure airblast atomizers show similar dynamic stmctures in radial distributions of mean droplet diameter, velocity, and Hquid volume flux. Extensive studies have been made (30,31) on the spray dynamics associated with pressure swid atomizers. Based on these studies, some common features were observed. Test results obtained from a pressure swid atomizer spray could be used to iUustrate typical dynamic stmctures in hoUow sprays. The measurements were made using a phase Doppler spray analyzer. 

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