The physical characteristics [density, viscosity, surface tension] of the liquid being sprayed can significantly affect an atomizer's performance. Unfortunately, the magnitudes of the effects of these characteristics vary with the atomizer type, design, scale and operating parameters. Even subtle differences in surface finish, nozzle material and geometry can significantly affect non-water spray performance. 

The laboratory at spray research is specifically designed to accommodate the testing of atomizers spraying a variety of non-water liquids and water-based simulants. We make extensive use of Designed Experiments to limit the size of the test matrices involving non-water liquids. It is often possible to use a succession of scaled instances of large atomizers to predict the full-scale performance with reasonable accuracy.

Extrapolating from water data to the atomizer's actual performance spraying a specific liquid is not at all straight-forward. Although the literature is replete with equations relating some aspect of atomizer performance to liquid properties, there is little agreement as to the exact details. Additionally, most of the reported studies have concentrated on the small-scale pressure-swirl atomizers used in gas turbines, spraying commercial fuels.

For dropsize performance, the general form is:

 DS Q x^a

where DS is some characteristic diameter [e.g.- D32, Dv0.5, D30], and x is some specific liquid property. For surface tension and the Sauter mean diameter [D32], the exponent a is cited variously as 0.19, 0.25 and 1.0. Likewise, for viscosity and D32, the  exponent a is cited as 0.06, 0.118, 0.16, 0.20 and 0.215. Relatively little data as to the relationship between dropsize performance and liquid density is available. Again however, for D32 the exponent a is cited over a wide range [i.e.-  -0.3767, -0.3215, -0.25, -0.22, 0.125 and 0.5].

The situation is further confounded by the fact that rarely does a liquid differ from water by a single physical characteristic. It is clearly unreasonable to expect any single-term relationship to adequately predict the affect of liquid characteristics on spray performance based solely on data gathered when spraying water.