Pumps axial flow

Axial-Flow (Propeller) Pumps (Fig. 10-44) These pumps are essentiahy very-high-capacity low-head units. Normally they are designed for flows in excess of 450 mVh (2000 gal/min) against heads of 15 m (50 ft) or less. They are used to great advantage in closed-loop circulation systems in which the pump casing becomes merely an elbow in the line. A common installation is for calandria circulation. A charac teristic cui ve of an axial-flow pump is given in Fig. 10-45. 

FIG. 10-45 Cbaracteristic curve of an axial-flow pump. To convert gallons per minute to cubic meters per hour, multiply by 0.2271 to convert feet to meters, multiply by 0.3048 and to convert horsepower to kilowatts, multiply by 0.746. 

Whereas the total dynamic head developed by a centrifugal, mixed-flow, or axial-flow pump is uniquely determined for any given flow by the speed at whicdi it rotates, positive-displacement pumps and those which approach positive displacement will ideally produce whatever head is impressed upon them by the system restrictions to flow. Actually with slippage neglecTed, the maximum head attainable is determined by the power available in the drive and the strength of the pump parts. An automatic relief valve set to open at a safe pressure... 

Figure 3-49. Upper limits of specific speeds for single suction, mixed and axial flow pumps handling clear water at 85°F at sea level. By permission, Hydraulic Institute Standards for Centrifugal, Rotary, and Reciprocating Pumps, Hydraulic Institute, 13th ed., 1975 [17].)...

Erosion corrosion of pump impellers, casings and wear plates can be very troublesome. Positive-displacement pumps create much less turbulence than centrifugal or axial-flow pumps and should be used where possible in critical... 

SINGLE SUCTION MIXED FLOW AND AXIAL FLOW PUMPS SPECIFIC SPEED, N. = PPMv/G-M... 

Explain briefly the significance of the specific speed of a centrifugal or axial-flow pump. 

Votically suspmded, single casing axial flow pumps with discharge through the column are designated Type VS3. 

There are many variants on this simple theme. For instance, many other methods for mixing have found use. In a design offered by Lurgi, the phases are mixed in what is essentially an axial flow pump, and then pass down a relatively long pipe where the turbulence of flow keeps the phases mixed while the extraction takes place. In another design, the individual phases are pumped and then join and pass through a static mixer. There are no particular physicochemical reasons for preferring one type of mixer to... 

Meyns B, Stolinski J, Leunens V, et al., Left ventricular support by catheter-mounted axial flow pump reduces infarct size. J Am Coll Cardiol 2003 41 1087-1095)... 

The centrifugal pump operates over a very wide range of flows and pressures. For low heads but high flows the axial pump is best suited. Both the centrifugal and axial flow pumps impart energy to the fluid Iw the rotational speed of the impeller and the velocity it imparts to the fluid. 

Typically, axial flow pumps are of high flow and low head type and have a high specific speed. On the other hand, purely radial pumps are of high head and low flow rate capabihty and have a low specific speed) Obviously a pump with a moderate flow and head has an average specific speed. 

Figure 7.3. Performance curves of single-suction impellers corresponding to two values of the specific speed, (a) Ns - 1550, centrifugal pump, (b) Ns = 10,000, mixed and axial flow pumps.

Figure 7.4. Performance of several kinds of pumps, (a) Comparison of small centrifugal and turbine pumps (Krista and Annett, 1940). (b) An axial flow pump operating at 880 rpm (Chem. Eng. Handbook, 1973). (c) An external gear pump like that of Figure 7.12(e) (Viking Pump Co.), (d) A screw-type positive displacement pump, (e) NPSH of reciprocating positive displacement pumps.

Explain briefly the significance of the specific speed of a centrifugal or axial-flow pump. A pump is designed to be driven at 10 Hz and to operate at a maximum efficiency when delivering 0.4 m3/s of water against a head of 20 m. Calculate the specific speed. What type of pump does this value suggest A pump built for these operating conditions has a measured overall efficiency of 70%. The same pump is now required to deliver water at 30 m head. At what speed should the pump be driven if it is to operate at maximum efficiency What will be the new rate of delivery and the power required ... 

Turbine pumps mix features of a simple propeller (axial flow) pump with a centrifugal pump and are often referred to as units with mixed flow. A simple turbine pump carries curved vanes on a central rotating spindle. Such pumps are often immersed in the liquid and find use in closed-loop circulation systems, in condenser circulating water, and in sumps and wells. Turbine pumps have noteworthy pumping capacity, and like positive displacements pumps are often used for heads up to about 100 ft/stage with capacities of up to several hundred gallons/minute. 

FIGURE 6.11 Upper limits of specific speeds of single-suction mixed-flow and axial-flow pumps. 

Compute the maximum pump capacity. For any centrifugal, mixed- or axial-flow pump, Ns =... 

Figure 5.30 Characteristic curve for an axial-flow pump.

Figure 4.4 shows various types of impellers that are used in centrifugal pumps. The one in a is used for axial-flow pump. Axial-flow pumps are pumps that transmit the fluid pumped in the axial direction. They are also called propeller pumps, because the impeller simply propels the fluid forward like the movement of a ship with propellers. The impeller in d has a shroud or cover over it. This kind of design can develop more... 

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