MMD/SMD

MMD/SMD that may be 1.1, 1.2 or 1.5J2491 Thus, once the SMD is calculated, the entire droplet size distribution after primary breakup can be determined. 

In the breakup regimes, a droplet may undergo secondary breakup when the breakup time is reached. The droplet size distribution after bag or multimode breakup may follow the Simmons root-normal distribution pattern 264 with MMD/SMD equal to 1.1,... 

To characterize a droplet size distribution, at least two parameters are typically necessary, i.e., a representative droplet diameter, (for example, mean droplet size) and a measure of droplet size range (for example, standard deviation or q). Many representative droplet diameters have been used in specifying distribution functions. The definitions of these diameters and the relevant relationships are summarized in Table 4.2. These relationships are derived on the basis of the Rosin-Rammler distribution function (Eq. 14), and the diameters are uniquely related to each other via the distribution parameter q in the Rosin-Rammler distribution function. Lefebvre 1 calculated the values of these diameters for q ranging from 1.2 to 4.0. The calculated results showed that Dpeak is always larger than SMD, and SMD is between 80% and 84% of Dpeak for many droplet generation processes for which 2left-hand side of Dpeak. The ratio MMD/SMD is... 

The ratio MMD/SMD is generally recognized as a good measure of droplet size range. In addition, various indices and factors have been defined to describe the spread of droplet sizes in a spray, for example, droplet uniformity index LVfSAMD -Z),)/MMD 433 and relative span factor (D09 -Z)01)/MMD, etc. 

A).5 (MMD) Mass median diameter 50% of total volume of droplets are of smaller diameters than this value V=50% Left-hand or right-hand side of Dpeak for q > or < 3.2584 MMD= (0.693) MMD -(o.evsf rfi 0 SMD v ( q J... 

Hewitt [34] derived formulas for Mass Mean Diameter (MMD) and Number Mean Diameter (NMD) for air-assist nozzles. He claims that SMD is primarily a function of liquid density and air velocity. The effects of nozzle geometry are neglected from his study, as his study was aimed more at rotary nozzles (as explained later in Rotary Nozzles section). 

Figure 4 (A, B) Number-frequency distribution and (C) cumulative number distribution of an aerosol of unit-density spheres. Indicated are the count median diameter (CMD), the surface median diameter (SMD), and the mass median diameter (MMD) of the number-frequency distribution. The 16, 50, and 84% size cut of the cumulative number distribution are shown. For further explanation, see text.

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