Nozzles twin-fluid

A number of techniques have been evolved to disperse liquids in gases in the form of fine droplets. The various atomizing techniques are jet injections, fan sprays, centrifugal nozzles, twin fluid atomizers, impinging jets, and rotary... 

The feed system consisted of a reservoir, a plunger-type feed pump, a twin-fluid atomising nozzle (giving a round spray of angle 13° in free air) and a mini-compressor. Inert gas for the twin-fluid nozzle was drawn between the outlet of the heat exchanger and the rotameter... 

NAR is the ratio of air to liquid flow rates through the nozzle of a twin fluid atomizer expressed either in mass units or in volume units (air at STP). 

Problem understanding In many cases, experiments can provide only reliable integral values. In the case of twin screw extruders, for example, these are the shaft torque and the pressure and the temperature at the extrusion nozzle. Computational fluid dynamics, however, provide local information about pressure, velocity, and temperature within the overall computational domain. The calculation of gradients provides additional information about the shear rate or the heat transfer coefficients. 

The twin-fluid atomizer used here and described elsewhere (8) is based on the above principle in which liquid fuel and air are forced through a nozzle and emerge from the oriflce in the form of a spray cone. A schematic of the atomizer is shown in Figure 1. 

An air-blast atomizer, designed on the basis of industrial-type twin-fluid atomizers, was supplied with kerosene under low pressure from a nitrogen cylinder and under high pressure air from a compressor. The atomizer nozzle diameter was 1.5 mm, a stabilizer disk with 89-mm diameter was fitted into an annular air duct of 316-mm diameter, kerosene flow rate was 2.3 kg/hr, and atomizing air flow rate was 0.69 kg/hr. 

For all atomizer designs the feedstock rheological properties will impact nozzle performance with the twin-fluid designs generally being less susceptible to a droplet size... 

The quantitative effect of the solution viscosity on measured, spray-averaged droplet size performance is shown in Figure 7 for a twin-fluid, gas-assisted nozzle (31). 

FIGURE 6 Nozzle tip images, twin-fluid atomizer, showing impact of feed rheology. 

Equation (35) for drop breakup caused by acceleration and Eqs. (37) to (39) to model drop breakup by turbulent stresses can be used to interpret drop behavior for the twin-fluid nozzle shown in Figure 7. The predicted size of the ethanol drops dispersed in supercritical carbon dioxide is compared with measured values in Figure 13. One can see that the model predicts well the... 

Advanced nozzle designs, such as twin-fluid, pre-orifice and air-inclusion nozzles, can also be used. Most are designed to reduce spray drift. Atomisation in twin-fluid nozzles occurs because the interaction of air and liquid. Different spray qualities can be produced by changing both liquid and air pressures. Low spray volume rates (75-1501/ha) and high work rates (ha/hour) are possible. 

Although pressure control is the most common way of adjusting the volume output of boom sprayers fitted with conventional nozzles, two other main approaches have also been used, namely the use of twin-fluid nozzles and arrangements based on the use of solenoid valves. It should also be noted that the use of other types of spray generation system, such as spinning discs or air shear nozzles give other options for control of applied volume rate, but such arrangements are not commonly used on boom sprayers. 

Miller, P.C.H., Tuck, C.R., Gilbert, A.J. and Bell, G.J. (1991) The performance characteristics of a twin fluid nozzle sprayer. Proceedings, Air Assisted Spraying in Crop Protection, 7-9 January 1991. British Crop Protection Monograph, 46, 97-106. 

Pressure nozzle spray diameter 70 to 10,00 pm capacity 0.03 to 0.3 L/s low viscosity and clean fluids. Spinning disc spray diameter 50 to 250 pm capacity 0.0015 to 0.4 L/s for usual fluids and for viscous fluid or fluid containing solids. Twin fluid spray diameter 2 to 80 pm capacity 0.03 L/s increasing the ratio of atomizing fluid to liquid from 1 to 10, will decrease the spray diameter by a factor of 10. Rayleigh breakup to produce uniform drops of diameter 1.8 x diameter of orifice. A related topic is prilling (Section 16.11.9.14). Surface aerators for activated sludge oxidation (instead of diffused air aeration. Section 16.11.8.1). Brush aerators for oxidation ditches. Motionless mixers spray flow. 

Pressure nozzle pressure 0.45 to 14 MPa increasing the pressure increases the capacity. Spinning disc increasing the capacity increases the drop size. Twin fluid high energy input. Surface aeration 0.01 to 0.025 kW/m or 0.3 to 1.2 kg O2/MJ. Brush aeration 0.015 to 0.018 kW/m 0.6 to 0.8 kg O2/MJ. Motionless mixers spray flow gas superficial velocity 3 to 25 m/s liquid superficial velocity 0 to 0.6 m/s. Turbulent flow. 

Another possibility could be the atomization of emulsions (simple or double) with a twin-fluid nozzle, in cold atmosphere such as -30°C, to produce solid particles. This process is used to study the atomization process (drops size distribution, shape) through the microstructure of the solid particles. 

Abstract Spray nozzles are used in many applications such as cleaning, cutting, and spraying. Spray nozzles come in many varieties, and are usually classified according to the specific mode of atomization they employ. In this chapter, twin fluid, swirl, hydraulic, ultrasonic, rotary, and electrostatic nozzles are discussed. First, their specific mode of atomization is explained, followed by a brief description on the variation on each type of nozzle. Next, a comprehensive list of performance correlations for each type of nozzle is compiled from various sources. Finally, these correlations are explored in more detail for each type of nozzle. 

Keywords Air blast Air assist Discharge coefficient Effervescent Electrostatic Hat fan nozzles Full cone Hydraulic Hollow cone Rotary SMD Spray angle Spray impact Spray pattern Swirl Twin fluid Ultrasoiuc... 

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