Orifice Generator

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). 

These droplets are then mixed with more air to dry the particles. The rate of droplet formation is equal to the oscillation frequency (/) of the piezoelectric crystal. From the volumetric flow rate of the liquid and the frequency /, the volume of the individual drops and particle diameter can be calculated. 

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The Coulter technique is a method of determining the number and size distribution of particles suspended in an electrolyte by causing them to pass through a small orifice on either size of which is immersed an electrode. The changes in electrical impedance as particles pass through the orifice generate pulses whose amplitudes are proportional to the volumes of the particles. The pulses are fed to a pulse height analyzer where they are scaled and counted and, from the derived data, the size distribution of the suspended phase is determined. 

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. 

G. Bream, U. Lackermeier Drop formation from a vibrating orifice generator driven by mexlulated electrical signals, Phys. Fluids 9, 3658-3669 (1997). 

Rietz Extruder This extruder, shown schematically in Fig. 18-49, has orifice plates and baffles along the vessel. The rotor carries nmlti-ple blades with a forward pitch, generating the head for extrusion through the orifice plates as well as battering the material to break up agglomerates between the baffles. Typical applications include wet... 

It will be seen when the pressure ratio Pi/Pi is less than the critical value (wr — 0.607) the flow rate becomes independent of the downstream pressure P2. The fluid at the orifice is then flowing at the velocity of a small pressure wave and the velocity of the pressure wave relative to the orifice is zero. That is the upstream fluid cannot be influenced by the pressure in the downstream reservoir. Thus, the pressure falls to the critical value at the orifice, and further expansion to the downstream pressure takes place in the reservoir with the generation of a shock wave, as discussed in Section 4.6. 

Micro-jet arrays are usually associated with lower energy consumption rates than sprays generated by the special (HAGO) nozzle for the same flow rate. The liquid was pushed through a 0.5 mm stainless steel orifice plate to form the jets. The holes in the plate were laser drilled and were arranged in a circular pattern giving a radial... 

A capillary rheometer is another type of instmment, in which the uncured mbber is extmded through a small orifice and the change in dimensions of the extmdate is measured with a laser [2]. This instmment generates high shear rates, compared to Mooney rheometer. The capillary rheometer can thus represent flow of compounds on mbber processing machinery, such as injection molds. 

Folded membranes were generated out of two phospholipid monolayers at the air/subphase interface [158]. A thin Teflon septum separated the two half-cells of the setup which was also made of Teflon. This septum, with an orifice 50-200 jim in diameter, was... 

The SUM was covered by a polymer film with an orifice of approximately 0.3 mm in diameter on each side, and subsequently a folded BLM was generated from a DPhPC/l,2-dipalmitoyl-in-glycero-3-phosphatidic acid (DPPA) monolayer on the side facing the SUM (Fig. 19). Interestingly, no pretreating of the orifice with any alkane or lipid was required, as is imperative for all other BLM techniques. Thus, an accumulation of such compounds could be excluded, and the physicochemical properties of the membrane and... 

Fig 1. Schematic diagram of the ICFB gasifier. 1. steam generator, 2. flowmeter, 3. orifice flowmeter, 4. air preheater, 5, gas plenum, 6. draft tube, 7. orifice, 8. gas separator, 9. freeboard, 10. screw feeder, 11. mono-pump, 12. sludge feed nozzle, 13. cyclone, 14. condenser, 15. collector, 16. filter, 17. ID fan. 

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