Shrouded impeller

Kuhni contacters (Eig. 15e) have gained considerable commercial application. The principal features are the use of a shrouded impeller to promote radial discharge within the compartments, and a variable hole arrangement to allow flexibility of design for different process applications. Columns up to 5 m in diameter have been constmcted (176). Description and design criteria for Kuhni extraction columns have been reported (177,178). 

Centrifugal-eompressor impellers are either shrouded or unshrouded. Open, shrouded impellers that are mainly used in single-stage applieations are made by investment easting teehniques or by three-dimensional milling. Sueh impellers are used, in most eases, for the high-pressure-ratio stages. The shrouded impeller is eommonly used in the proeess eompressor beeause... 

For turbine mixers that the width of a baffle should not exceed more than one-twelfth of the tank diameter and, for propeller mixers, no more than one-eighteenth the tank diameter. With side-entering, inclined or off-center propellers, as shown in Figure 13, baffles are not required. Instead, shrouded impellers and diffuser rings may be used to suppress vortex formation. These devices contribute to flow resistance and reduce circulation by creating intense shear and abnormal turbulence... 

Impeller Problems The high-speed rotation of the impeller of a centrifngal compressor imparts the vital aerodynamic velocity to the flow within the gas path. The buffeting effects of the gas flow can canse fatigue failures in the conventional fabricated shrouded impeller due to vibration-induced alternating stresses. These may be of the following types ... 

Pump casing, back plate impeller pin, one type, back shrouded impeller and shaft shall be 316 stainless steel, 240 grit finish, electro-polished... 

Figure 7.10. Some types of impellers for centrifugal pumps, (a) Open impeller, (b) Semiopen impeller, (c) Shrouded impeller, (d) Axial flow (propeller) type, (e) Combined axial and radial flow, open type, (f) Shrouded mixed-flow impeller, (g) Shrouded impeller (P) in a case with diffuser vanes (V). (h) Turbine impeller.

FIGURE 4.4 Various types of pump impellers (a) axial flow (b) open type (c) mix-flow type and (d) shrouded impeller. 

Enclosed impellers are also referred to as shrouded impellers. Figure 21.10 illustrates examples of open, semi-open, and enclosed impellers. 

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