Inlet guide vanes types

The so-called propeUer-type fans with blades that are aerodynami-caUy designed (as seen in Fig. 10-68) can consist of two or more stages. The air in these fans enters in an axial direction and leaves in an axial direction. The fans usually have inlet guide vanes followed by a rotating blade, followed by a stationary (stator) blade. 

The two principal elements of evaporator control are evaporation rate a.ndproduct concentration. Evaporation rate in single- and multiple-effect evaporators is usually achieved by steam-flow control. Conventional-control instrumentation is used (see Sec. 22), with the added precaution that pressure drop across meter and control valve, which reduces temperature difference available for heat transfer, not be excessive when maximum capacity is desired. Capacity control of thermocompression evaporators depends on the type of compressor positive-displacement compressors can utilize speed control or variations in operating pressure level. Centrifugal machines normally utihze adjustable inlet-guide vanes. Steam jets may have an adjustable spindle in the high-pressure orifice or be arranged as multiple jets that can individually be cut out of the system. 

In initial test evaluation, a low nss value of 22,000 was unfavorably realized for 450 gpm at 6000 rpm, as indicated in Fig. 3, The integrally cast guide vanes within the pump-inlet elbow-type bell were then partially machined away. The corresponding reduction of inlet losses resulted in an nss of 150,000 at 450 gpm. This was equivalent to a favorably low liquid level of 10 in. above the inlet edge of the pump, as indicated in Fig. 4. 

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