Centrifugal atomizer

Centrifugal atomizer Centrifugal casting Centrifugal cleaners Centrifugal compressors... 

Atomization of melts has, in principle, some similarity to the atomization of normal liquids. The atomization processes originally developed for normal liquids, such as swirl jet atomization, two-fluid atomization, centrifugal atomization, effervescent atomization, ultrasonic piezoelectric vibratory atomization, and Hartmann-whistle acoustic atomization, have been deployed, modified, and/or further developed for the atomization of melts. However, water atomization used for melts is not a viable technique for normal liquids. Nevertheless, useful information and insights derived from the atomization of normal liquids, such as the fundamental knowledge of design and performance of atomizers, can be applied to the atomization of melts. 

The Laser-spin-atomized droplets are usually spherical, clean, and homogeneous in composition. A mass median diameter of 100 pm has been obtained for a Ni-Al-Mo alloy. Cooling rates are estimated to be in the order of magnitude of 105 °C/s. Similarly to other centrifugal atomization techniques, droplet properties (shape, size, cooling rate, etc.) are dependent on the rotation speed, ingot diameter, superheat, and material properties. 

Metals Company used a commercial centrifugal atomizer to produce elongated droplets quenched with air. This atomizer has a spinner consisting of a steel cylinder with numerous fine holes along the barrel. The atomization system, while generating large output and high yield, allows variation of the spinner speed and hole size, adjustment of the melt temperature, and control of the atmosphere if necessary. 

In rotary or centrifugal atomization, droplet formation may follow several distinct mechanisms, as proposed by many research-ers 94 l09l"l, 2I on the basis of experimental observations of rotating flat disk process (Fig. 3.9) (a) Direct Droplet Formation, (b) Direct Droplet and Ligament Formation, (c) Ligament Formation, and... 

Most commercial and near-commercial atomization processes for liquid metals/alloys involve two-fluid atomization or centrifugal atomization. As suggested by many experimental observations, two-fluid atomization of liquid metals is typically a three-stage process, 3IX 3 yl whereas centrifugal atomization may occur in three different regimes.[5][320] Many atomization modes and mechanisms for normal liquids may be adopted or directly employed to account... 

Droplet Formation in Centrifugal Atomization. The mechanisms of centrifugal atomization of liquid metals are quite similar to those for normal liquids. Three atomization modes have been identified in rotating electrode atomization process, i.e., (I) Direct Droplet Formation, (2) Ligament Disintegration, and (3) Film/Sheet Disintegration.1[189][32°] are aiso applicable to the centrifugal atomiza-... 

This number group may be used to determine in which regime a centrifugal atomization takes place for given operation conditions and material properties. Since the group is not dimensionless and the plot was made using SI units, it should be used with caution. From Fig. 4.3, 132°1 it can be seen that for a given liquid metal/alloy at a... 

Table 4.19. Correlations for Mean Droplet Sizes of Liquid Metals in Centrifugal Atomization...

Figure 4.3. Regimes in centrifugal atomization of melts Direct Droplet Formation, Ligament Disintegration, and Film/Sheet Disintegration.

This approximate relationship is similar to those for centrifugal atomization of normal liquids in both Direct Droplet and Ligament regimes. However, it is uncertain how accurately the model for K developed for normal liquid atomization could be applied to the estimation of droplet sizes of liquid metals Tombergl486 derived a semi-empirical correlation for rotating disk atomization or REP of liquid metals with the proportionality between the mean droplet size, rotational speed, and electrode or disk diameter similar to the above equation. Tornberg also presented the values of the constants in the correlation for some given operation conditions and material properties. 

A Niro Utility Dryer (Columbia, MD) equipped with a 12 cm diameter radial vane centrifugal atomizer (24,000 rpm) was used for spray drying. Drying conditions were standardized at an inlet air temperature of 200 + 5°C and an exit air temperature of 100 +... 

Similarly, a chamber of relatively large diameter but low height is used to conform to the droplet pattern spun horizontally from a centrifugal atomizer. 

A 3-1/2 foot diameter "Laboratory Spray Dr yer" made by Bowen Engineering, Somerville, NJ, equipped with a centrifugal atomization nozzle, was used for these experiments. 

In case of use of pressure nozzles, the liquid feed is pumped through a small orifice under high pressure, typically 2-300 bars, and the liquid breaks up into droplets by friction with the atmosphere. Nozzles may produce powders with particularly narrow particle size distribution or relatively dense particles. The particle size from a given pressure nozzle is influenced by the feed rate. This is controlled by varying the feed pressure which again influences the flow capacity. Pressure nozzles are therefore less flexible than centrifugal atomizers with regard to ease of operation and control of product characteristics. 

G. Michot, Production of icosahedral Al-Cu-Fe powders by centrifugal atomization method, in C. Janot, R. Mosseri (Eds.), Proc. of the 5th Internal Conf. on Quasicrystals, (Singapore World Scientific,1996) p. 794-797. 

One of the primary reasons that the spray dryer-scrubber is able to achieve excellent sulfur dioxide removal with such low liquid-to-gas ratios is the small size of the droplets produced by the high speed centrifugal atomizer. This type of atomizer also has an easily controlled turndown capability which is a desirable feature that has been demonstrated in the pilot tests. As gas flow decreases, the amount of sodium carbonate solution can be decreased in direct proportion without interfering with sulfur dioxide removal efliciency. The atomizer actually produces finer droplets at the lower liquid flow rates. This appears to compensate for any gas-liquid mixing problems that could impair performance. 

Devices that spray liquids are called atomizers. They are classified as direct-jet atomizers, which create a cylindrical jet, and centrifugal atomizers, which create a swirling jet with a gas core inside. A thin liquid cylindrical layer (sheet) is formed at the exit of a centrifugal atomizer and then expands in the radial direction as... 

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