Vibrating orifice

The droplet size delivered from a vibrating orifice monodisperse aerosol generator can be derived from the following expressions ... 

Vibrating- Orifice Atomization 103-104 Standard deviation <1.05 Ca, Zn, Al Low Very low Low Very narrow size distribution, High EE Coarse particles,Very low volume productivity... 

There are a number of techniques for generating aerosols, and these are discussed in detail in the LBL report (1979) and in volumes edited by Willeke (1980) and Liu et al. (1984). We briefly review here the major methods currently in use these include atomizers and nebulizers, vibrating orifices, spinning disks, the electrical mobility analyzer discussed earlier, dry powder dispersion, tube furnaces, and condensation of vapors from the gas phase. 

Another common method of generating particles with diameters 0.5-50 /rm is the Berglund-Liu (1973) vibrating-orifice generator shown schematically in Fig. 11.77. The solution to be aerosolized is pumped through a small orifice 5-20 /xm in diameter. The orifice is oscillated by a piezoelectric crystal so that the liquid stream is broken on each oscillation, forming a small liquid particle that is carried away in a stream of air. 

FIGURE 11.77 Schematic diagram of vibrating-orifice aerosol generator (from Hinds, 1982). 

The vibrating orifice method for producing monodisperse liquid aerosols, combined with drying or chemical reaction in a flame, comes about as close to being a magic particle maker as any technique we are aware of. 

Experimental evaluation of various widely used commercial instruments has been undertaken by several investigators, including Liu et al. (1974), who used the vibrating orifice technique to generate spherical aerosols with narrow size distributions. Similarly, Pinnick and Auvermann (1979) generated droplets of a solution which were dried to make solid particles for evaluating the response of... 

Wall-coated flow tube reactors have been used to study the uptake coefficients onto liquid and solid surfaces. This method is sensitive over a wide range of y (10" to 10 1). For liquids this method has the advantage that the liquid surface is constantly renewed, however if the uptake rate is fast, the liquid phase becomes saturated with the species and the process is limited by diffusion within the liquid, so that corrections must be applied [70,72,74]. Many experiments were designed to investigate the interaction of atmospheric species on solid surfaces. In this case the walls of the flow tube were cooled and thin films of substrate material were frozen on the wall. Most of the reaction probabilities were obtained from studies on flow tubes coated with water-ice, NAT or frozen sulfate. Droplet train flow tube reactors have used where liquid droplets are generated by means of a vibrating orifice [75]. The uptake of gaseous species in contact with these droplets has been measured by tunable diode laser spectroscopy [41]. 

The AeroDose is a battery-operated drug delivery device under development by AeroGen, Inc. (Sunnyvale, CA), which uses vibrating orifice technology to produce drug... 

AeroDose Vibrating orifice 2.0 pm 80% of nominal dose 70% of emitted dose... 

Membrane nebulizer Vibrating orifice, continuous mode NA 50-80% of emitted dose NA... 

A semi-continuous SAS apparatus, as a rule, consists of two pumps used to deliver the liquid solution and supercritical CO2, respectively. A cylindrical vessel is used as the precipitation chamber. The liquid mixture is delivered to the precipitator through an injector. Different arrangements have been proposed in the literature like nozzles, capillaries, vibrating orifices and coaxial devices. Supercritical CO2 is delivered through another inlet port that can be located on the top or the bottom of the vessel. The pressure in the precipitator is regulated by a micrometering valve located at the exit of the chamber. A stainless-steel fiit located at the bottom of the precipitator is used to collect the produced powder. A second vessel located downstream the micrometering valve is used to recover the Uquid solvent. 

The vibrating-orifice monodisperse method of aerosol generation is based on the principle of the disintegration of a jet of liquid issuing from an orifice that is... 

An illustration of the design of the vibrating-orifice generator head is shown Fig. 6. Liquid is fed into the generator head and forced out of the orifice. 

Figure 6 A vibrating-orifice aerosol generator (TSI Model 3450).

E-C, evaporation-condensation N, nebulizer EC, electrostatic classifier VO, vibrating orifice SD, spinning disc FD, fluidized bed RB, rotating brush WDF, Wright dust feeder NBS, NBS dust generator. Values of parameters given are from specifications listed by TSI, Inc., and BGI, Inc. Stability data are from the references. A density of / g/m3 is assumed for the mass concentration values. 

Constant-ouput atomizer, tri-jet aerosol generator, electrostatic classifier, vibrating-orifice aerosol generator, fluidized-bed aerosol... 

A probe, called a vibroflot, consists of a cylindrical shell about six feet long and 12 to 16 inches in diameter, which houses a vibrator. Orifices are provided at the bottom and sides of the cylinder for fluid egress (normally... 

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