Internal mixing 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. 

External mixing nozzle is operated with low liquid pressure. The liquid feed is provided through an inner duct while an atomization gas is fed by an external annular opening around the liquid orifice. On the other hand, internal mixing nozzles take advantage of gas expansion at the nozzle outlet. Part of the pressure energy applied is used to scatter the liquid fragments within and beyond the nozzle oriflce by the sudden gas expansion (Walzel 2011). 

However, the static-drop assumption is usually extremely conservative. For example, the high interfacial velocity in the spray from nozzles yields a high degree of internal mixing and much higher transfer. 

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. 

Impact nozzles Spinning discs Internal mixing... 

According to its working principles, the nozzle shown in Fig. 7.5 should be classified as a three-flow internal-external mixing nozzle Berman and co-workers called it a complete external mixing type . 

FIGURE 3 Atomization nozzle designs for internal mixing and external mixing... 

Gas and hquid can be brought in contact either within the nozzle (internal mix) or outside of the nozzle (external mix). In addition, nozzles can be categorized based on the flow rate of the atomizing gas and the way the gas is brought into contact with the liquid. These variations are airblasting, air-assisting, and effervescent nozzles. The main difference between each of the three is the velocity and quantity of air used in the atomizing process. Another difference relates to when the air is mixed with the liquid stream. 

The liquid used is water, and the gas is air 30 kg/h internal mixing The liquid film thickness, t, must be less than 0.7 mm Ideal liquids are ethanol or glycerin Nozzle must be external mixing Ideal for kerosene, or a liquid with liquid properties similar to kerosene Nozzle must be external mixing Z>3o volume mean diameter 87 m/s < Ua < 116 m/s 6.5 m /s < 0L < 10-5 m /s Air should be injected tangentially Conditions are the same as above... 

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