Volute, centrifugal-pump

Centrifugal pumps with diffusion vanes are called diffusion pumps or, more recently, vertical turbine pumps. Those pumps with volute casings are called volute pumps. 

Figure 7.9. Some types of centrifugal pumps, (a) Single-stage, single suction volute pump, (b) Flow path in a volute pump, (c) Double suction for minimizing axial thrust, (d) Horizontally split casing for ease of maintenance, (e) Diffuser pump vanes V are fixed, impellers P rotate, (f) A related type, Ihe turbine pump.

Rotary centrifugal pumps with no valve action open impeller, closed impeller, volute pumps, turbine pumps... 

Centrifugal pumps can also be constructed in a manner that results in two distinct volutes, each receiving the liquid that is discharged from a 180 degrees region of the impeller at any given time. Pumps of this type are called double volute pumps. In some applications the double volute minimizes radial forces imparted to the shaft and bearings due to imbalances in the pressure around the impeller. 

Centrifugal pumps also rec]uire that the fluid be available to the pump s suction nozzle with sufficient energy. Centrifugal pumps cannot suck or draw the liquid into the pump housing. The principal pumping unit of a centrifugal pump is the volute and impeller. (See Figure 1-3). 

Iversen, H. W., Rolling, R. E., Carlson, J. J. Volute pressure distribution, radial force on the impeller and volute mixing losses of a radial flow centrifugal pump. Trans. ASME, journal of Engineering for Tower 82 (1.960), pp. 136-144. 

With no other available escape route, the fluid is passed to the outside of the impeller by centrifugal force and into the volute where its kinetic energy is converted into pressure. At the point of discharge (i.e., discharge nozzle), the fluid is highly pressurized compared to its pressure at the inlet nozzle of the pump. This pressure drives the... 

Total head against capacity characteristic curve fora volute centrifugal pump... 

A volute centrifugal pump with an impeller diameter of 0.02 m has the following performance data when pumping water at the best efficiency... 

The impeller is the working part of a centrifugal pump. The function of the impeller is to increase the velocity or kinetic energy of the liquid. The liquid flows into the impeller, and leaves the impeller, at the same pressure. The black dot shown at the top of the impeller in Fig. 23.6 is called the vane tip. The pressure at the vane tip is the same as the pump s suction pressure. However, as the high-velocity liquid escapes from the impeller and flows into the volute, its velocity decreases. The volute (which is also called the diffuser) is shaped like a cone. It widens out in the manner illustrated in Fig. 23.7. As the liquid flows into the wider section of the volute, its velocity is reduced, and the lost velocity is converted—well, not into pressure, but into feet of head. 

Binder, R. C., and Knapp, R. T., Experimental Determinations of the Flow Characteristics in the Volutes of Centrifugal Pumps, Trans. ASME 58, 1936. 

Characteristic Curves. The pressure head versus flow relationship for a centrifugal pump, called the characteristic curve, and illustrated in Figure 13, depends very much upon the design of the impeller, its vanes and the volute casing. 

Volute—Casing of a centrifugal pump that is shaped into a spiral. 

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