Centrifugal Pumps |
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a₁ a₂ actual angle a2 angular momentum brake horse-power capacity cent centrifugal pump computed constant speed cost curves in Fig decrease determined diffusion vanes discharge pipe disk friction displacement pump equation falling characteristic flow foot valve given gross efficiency head and discharge head developed head per stage hydraulic efficiency Hydraulic Turbines impeller passages impeller vanes increases involute kinetic energy Laval leakage loss of head manometer maximum efficiency Mechanical efficiency motor multi-stage pump necessary number of stages number of vanes obtained pipe line Pitot tube radial radius rate of discharge rotation rotative speed seen in Fig shaft shock loss shown in Fig single-stage pump specific speed Steam Turbine Stuffing Box suction impeller suction pipe theory thrust thrust bearing total head type of pump v₂ value of h vane angle vary velocity head volumetric efficiency volute pump water horse-power Worthington turbine pump zero
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Page 171 - ... cutwater." If the cross.section of the case is circular, as in Fig. 9, the outer boundary curve is a parabolic spiral whose equation is r = \/c0 + K , where 0 is the angle measured from the "cutwater," K is the radius to the "cutwater," and c is a constant. If the cross-section of the case is rectangular, the outer boundary curve should be a volute the diameter of whose base circle is 2K sin A, where K has the same meaning as in the former instance, and A is the angle with the tangent' made by...
Page 148 - Francis formula slightly modified is q = 3.33(L - 0.1 nH) (H + oA,)1.8 where L is the length of the weir crest in feet, H is the head on the weir measured in feet, n is the number of end contractions or is zero for a suppressed weir, hv the velocity head in the weir channel, and aa factor varying from 1.0 to 2.0 according to circumstances.1 Experiments of Schoder and Turner indicate that for H = 0.1 ft. the factor 3.33 should be increased by 7 per cent., for H = 0.2 ft. by 3 per cent., and that it...
Page 94 - Sec. peller, and consequently the impeller passages, is not completely filled with water. Thus the actual rate of discharge of the pump is decreased below the expected amount. This cavitation may make itself apparent even where the pump is tested at one speed only. It is indicated by an abrupt break in the smoothness of the curve or by a marked increase in the steepness of the curve for the larger discharges.
Page 148 - H = 0.1 ft. the factor 3.33 should be increased by 7 per cent., for H = 0.2 ft. by 3 per cent., and that it is correct when H = 0.3 ft. For small rates of discharge the triangular weir is better than the rectangular weir. Any angle of notch may be employed. For the 90° triangular notch the formula is q = 2.54 H™ The Venturi meter is very satisfactory and should be permanently installed in many pumping plants as it permits of the measurement of water without any interference in its flow. The extra...
Page 57 - The diameter of the discharge pipe of a centrifugal pump = 6 in., that of the suction pipe = 8 in. Pressure gage at d reads 30 Ib. per sq. in., vacuum gage at s reads 10 in. of mercury. The pressure gage is 3 ft. above the vacuum gage. If q = 3.0 cu. ft. per sec. and the brake horse-power = 36.0, find the efficiency of the pump. (NOTE. A pressure gage reads pressures above that of the atmosphere, a vacuum gage reads the amount by which the pressure is less than that of the atmosphere.) Ans. h = 85.8...
Page 90 - For the curves in Fig. 61 the corresponding values of these factors are 0.96, 0.985, and 0.80 respectively. It will be noticed that for small rates of discharge the curves in Fig. 66 are concave upward and, after passing a point of FIG. 62. — Construction of 6-inch De Laval centrifugal pump. inflection, they assume the customary form of concave downward. The reason for this is that the "churning loss
Page ii - Journal Engineering Record Engineering News Railway Age Gazette American Machinist Signal Engineer American Engjneer Electric Railway Journal Coal Age Metallurgical and Chemical Engineering Power PROBLEMS IN ALTERNATING CURRENT MACHINERY BY WALDO V.
Page 105 - Fig. 78 we have 105 something that is analogous to the characteristic curve for a hydraulic turbine as the coordinates are speed and discharge. (However, these coordinates represent actual values and not values under a unit head.) Upon this diagram we draw isohead, iso-power, and iso-efficiency curves. By the use of these diagrams it is possible to tell at a glance what the conditions of operation might be under any circumstances and it is easily seen what is the most economical field of operation....
Page 130 - ... favor. For other situations they may have a greater economy in some instances. Also they are able to lift water from below them at starting without being primed. The fact that there is no relation between head and discharge is often an advantage in their favor. Where either the head or the discharge are required to vary within wide limits and where they do not maintain definite relations with each other, the displacement pump will be found to be more flexible and more economical. 93. PROBLEMS...
Page 132 - ... Volute Pumps. — It is usually stated that the volute pump is very good for low heads but is inefficient under high heads and that for the latter we should resort to the turbine pump. The reason why the value of the head enters the question is that it is necessary to transform a greater per cent. of the kinetic energy of the water leaving the impeller into pressure with high heads than with low heads. It is never all converted into pressure because the water must possess a certain amount of...