Two-Fluid Pneumatic Atomizers

Two-Fluid (Pneumatic) Atomizers This general category includes such diverse apphcations as venturi atomizers and reac tor-effluent quench systems in addition to two-fluid spray nozzles. Depending on the manner in which the two fluids meet, several of the breakup mechanisms may be apphcable, but the final one is high-level turbulent rupture. 

For proper use of the equations, the chamber shape must conform to the spray pattern. With cocurrent gas-spray flow, the angle of spread of single-fluid pressure nozzles and two-fluid pneumatic nozzles is such that wall impingement wiU occur at a distance approximately four chamber diameters below the nozzle therefore, chambers employing these atomizers should have vertical height-to-diameter ratios of at least 4 and, more usually, 5. The discharge cone below the vertical portion should have a slope of at least 60°, to minimize settling accumulations, and is used entirely to accelerate gas and solids for entty into the exit duct. 

In internal mixing atomization (for example centrifugal-pneumatic atomization), 159] the liquid metal and gas enter the swirl jet atomizer tangentially under pressure (Fig. 2.13)J159] The two fluids rotate, form a mixture, and accelerate in the confuser. Due to the strong centrifugal force, the liquid metal forms a film at the nozzle exit even without the presence of the gas. With the applied gas, the liquid film is atomized into a fine dispersion of droplets outside the nozzle. 

Nozzles enable the kinetic energy of a liquid propulsion jet to be utilized for different purposes. In the first instance one can distinguish between one- and two-component nozzles. Single fluid nozzles are generally used as atomizer nozzles, in which the kinetic energy of the liquid propulsion jet is utilized for dispersion of its own. There are, however, also pneumatic atomizer nozzles, which belong to two-component nozzles [571]. 

Two-Fluid or Pneumatic Nozzles Atomization by Kinetic Energy... 

Three general types of atomizers are available. The most conunonly used are the rotary wheel atomizers and the pressure nozzle single-fluid atomizers [8]. Pneumatic two-fluid nozzles are used only rarely in very special applications. 

Atomization and nozzle design Rotary, multi-fluid pneumatic (two to four fluids), pressure, and ultrasonic nozzles... 

Two-fluid nozzles, also known as pneumatic nozzles, use a compressed gas to atomize the liquid feed. There are different designs of nozzles on the market. The two major groups of two-fluid nozzles are known as an external mixing nozzle and an internal mixing nozzle. 

Three general types of atomizers are available. The most commonly used are the rotary wheel atomizers and the pressure nozzle single-fluid atomizers [8]. Pneumatic two-fluid nozzles are used only rarely in very special applications. Existing spray drying systems provide various forms of the dry product—from fine powders to granules. The typical ranges of the disintegrated droplets and particle sizes of various products in a spray dryer are listed in Table 10.3. 

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