US1812309A - Centrifugal pump - Google Patents

Description

' June 30, 1931.

A. F. SHERZER 1,812,309 CENTRIFUGAL PUMP Filed March 22, 1927 2 Sheets-Sheet 1 INVENTOR. 1220): 12251622702. BY

HIS ATT RNEY.

June 30, 1931. SHERZER 1,812,309

CENTRIFUGAL PUMP Filed March 22, 1927 2 Sheets-Sheet 2 IN V EN TOR.

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H/S AT RNEY.

Patented June 30, 1931 UNITED STATES PATENT OFFIGE ALLEN F. SHERZER, F ANN ARBOR, MICHIGAN, ASSIGNOR T0 INGERSOT'L-RAND COM- EANY, 0F JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY cnivcarrueen FUMP AppIication medium-en 22,

This invention relates to centrifugal pumps, blowers and the like, but more particularly to centrifugal pumps for liquids.

" The object of the invent-ion is to increase the eficiency of a centrifugal pump.

A further object of the invention is to so proportion a centrifugal pump that a considerable amount of head or pressure will be developed above and beyond that heretow fore obtainable of a given impeller diameter and rotative speed.

Further ob]ects and advantages will be in part obvious and in part pointed out hereinafter.

In the drawings in which similar reference characters refer to similar parts,

Figure 1 is a longitudinal vertical section through a centrifugal pump constructed in accordance with the practice of the invengo tion, and

Figure 2 is a central cross section through the pump taken on the line 2-2 of Figure 1 looking in the direction of the arrows.

Referring to the drawings, the centrifugal pump comprises an impeller A adapted to rotate within a casing B and journalled in suitable endibearings C. In this instance the impeller A is of the double flow type, the water or other fluid to be pumped being adapted to enter at the opposite eyes D and E and discharged at the exit F at the periphery of the impeller.

The casing B is accordingly provided with inlets G adjacent the eyes of the impeller A and an outlet H is also provided for the fluid discharged from the pump.

The impeller A may be suitably mounted on a shaft J as by means of sleeves K screwed to the shaft J as at L and suitable stufling 40 boxes 0 with glands P may be provided.

' For driving the impeller A, the shaft J may have a flange Q for attachment to a motor.

One of the principal sources of loss in a centrifugal pump is the power consumed in so-called disk-friction, or in other words,

. that power required to merely rotate the im-\ 'peller in the water surrounding it, even though no water is pumped. This varies about as the fifth" power of the impeller diameter. Disk friction is by this inven- 1927. Serial No. 177,335.

of this form the water in the clearance space beyond the side walls of the impeller A and the stationary sides R of the shell B and also the water in the circular portion T of the casing B radially beyond the impeller A rotates with the impeller at about the same angular velocity. In this way, by the action of centrifugal force, the pressure at the clearance rings U of the impeller A is considerablyv reduced and thus the internal leakage back into the inlets G is correspondingly decreased, thereby assisting in increasing the eificiency of the pump considerably in excess of the ordinary volute type.

The use of a circular portion T in the casing B adjacent the periphery F of the impeller A is most favorable to the production of a large diameter vortex within the casing B of the pump and no out water is provided. It is understood that while the circular casing T is preferable and the ideal form for this; pump, slight variations in the direction of the volute type do not appear to seriously affect the performance. The greater portion of the casing, however, should be concentric and circular as at T so as to prevent restrictions in the vortex.

The curvature and number of vanes V in.

the impeller A are not necessarily diiferent from those of any other well designed impeller heretofore employed. However, the width of the impeller A is considerably greater than in designs heretofore used for equal capacity and head. Preferably the impeller A is from two or three times the usual width, the preferred widths in low head pumps for heads up to one hundred feet are about two-tenths of. an inch per one hundred gallons per minute. of capacity, such width being the width of vthe exit opening at the periphery F. In high head pumps up to approximately three hundred feet, thewidths may be approximately eleven-hundredths of an inch per one hundred gallons per minute. These measurements are not inconsistent for the reason that there is a film of fluid adjacent the walls of the passages within the impeller A which is of practically no value because of the retardation due to skin fric-- tion. The relatively great width of the impeller A results in larger passage areas and hence lower relative water velocities in the impeller. This means lower friction loss in the impeller, but what is mainly sought by the low water velocity in the impeller, in this invention, is to provide a low absolute angle of discharge from the impeller. Preferably, the absolute velocity of the water leaving the impeller at the periphery F should be substantially tangential in direction. This is producedin this invention by the low relative velocity of the water leaving the impeller. The resultant absolute velocity of the water leaving theimpeller is determined'by two component velocities, one being the tangential velocity of the impeller and the other the velocity of the water relative to the impeller. It is evident that a true tangential absolute velocity of the water may not be obtained.

However, it-is considered that the tangential component is the only truly usefuLvelocity of the water to produce a head within the casing and low disk friction loss. The angle of absolute velocity of water discharge, from the impeller is preferably less than five .degrees. Best results have been obtained when this angle is about three degrees in the circular casing pump. In practice, heretofore, this angle has been approximately six degrees to ten degrees in ordinary pumps.-

Due to the low angle of discharge from the impeller A, the water discharged from the impeller at the periphery-F has its maximum effect in causing the larger vortex in the circular chamber inclosed by the portion T of the casing B. This may be compared to the action of a jet of Water directed into a tub of water causing the water to revolve. It is obvious that the more nearly tangential the direction of the jet, the more effective it will be in producing rotation of the water in the tub.- .Therefore, for practical purposes the discharge from the impeller should be substantially tangential and is in practice substantially at an angle of three degrees.

A feature of this invention is the proper proportion of the clearance between thesides S of the impeller and the stationary side walls R of the pump casing or shell B. Heretofore this has been considered of slight importance but it has been found in the practice of this invention to be very important when the shell or casing B is of the concern tric type or circular as at T.-

The proportions may be best expressed terms of the lateral cylindrical area obtained by revolutions of a perpendicular from the impeller to the shell, about the center of the shaft as an axis. Such a perpendicular revolved will generate the surface of a cylinder and the variations of the areas between the walls R and S leaving the periphery F of the impeller A and approaching the center of the shaft J is of great importance in producing the most eflicient results. At the periphery F of the impeller A it has been found that the perpendicular distance from the sides R of the casing B to the outer circumference of the runner should be from six-tenths to nine-tenths of the width of the impeller at I its periphery F. It has been foundthat ifv the cylindrical areas of clearance between the walls R and S increase in the direction of the center of the impeller A, best efiiciency is obtained from the pump. If the reverse condition exists, the efliciency of the pump may be relatively poor. The rate of increase of the cylindrical areas referred to is not so important as the fact that there is an increase. This divergence of the adjacent side walls R and S toward the axis of the impeller may be expressed by saying that the longitudinal cylindrical sections of the clearance provided between the casing B and the impeller A increase from the periphery F of the impeller A towards the axis of the impeller. Such divergence should existv for at least threetenths of the impeller radius, measured radially inward from the impeller periphery F. Further divergence has been found to be of no practical importance.

While each of the features above described may be of some value in the designs of a centrifugal pump, it has been found that in practice the best result and greatest efliciency is produced by the combination of such features and especially in combination with .a casing B circular as at T. The good effects of each feature may bein part nullified by features of design heretofore employed which Thus by the above construction are accom- I plished among others, the objects hereinbefore referred to.

' I claim:

1. A centrifugal pump comprising an impeller and a casmg having a circular portion adjacent to the periphery of the impeller, the distance from the sides of the casingto the (sides of the impeller at the periphery thereof being 'not less than six-tenths nor greater than nine-tenths of the width of the impeller at its periphery, the adjacent side walls of said casing and impeller being .di-

vergent toward the axis of the impellerso tha-tlongitudinal cylindrical sections of the clearance" provided between the casing and impeller increases from the periphery of the impeller toward the axis of the impeller, and means to prevent substantial longitudinal movement of the impeller with respect to the casing.

2. A centrifugal pump comprising an impeller and a casing having a circular portion adjacent to the periphery of the impeller, the distance from the sides of the casing to the sides of the impeller at the periphery thereof being not less than six-tenths nor greater than nine-tenths of the width of the impeller at its periphery, the adjacent side Walls of said casing and impeller being divergent toward the axis of the impeller so that longitudinal cylindrical sections of the clearance provided between the casing and impeller increases continuously from the periphery of the impeller toward the aims of the impeller, for not less than about threetenths of the radial distance from the periphery of the impeller to the center line of the shaft.

3. A centrifugal pump comprising an impeller and a casing having a circular portion adjacent to the periphery ofthe impeller, and said impeller being not less than sixtenths nor greater than nine-tenths of the width of the impeller at its periphery, the adjacent side walls of said casing and impeller being divergent toward the axis of the impeller so that longitudinal cylindrical sections of the clearance provided betwee the casing and impeller increases from the periphery of the impeller toward the axis of the impeller to a distance of three-tenths of the impeller radius measured radially inwardly from the impeller periphery and means to prevent substantial longitudinal movement of the impeller with respect to the casing.

4. A centrifugal pump comprising a casing havi an inlet and outlet and a rotating imp 1' having relatively wide exit passages forming an exit of larger size as compared to the inlet of the impeller so as to decrease the fluid velocity in the outlet from inlet to exit, said casing being substantially concentric with theimpeller adjacent the periphery -thereof, theadjacent side walls of the casing and impeller being divergent towards the axis of the impeller so that longitudinal concentric sections of the clearance provided between the casing and impeller increases from the periphery of the impeller to the axis of the impeller.

- 5. A centrifugal pump comprising an 1mp'eller and a casing surrounding said impeller, said casing having side walls divergent from the side walls of the impeller from the impeller periphery toward the impeller axis forming a path for the fluid being pumped of increasing lon 'tudinal cylindrical section between the cm and the impeller from the periphery of the impeller toward the axis of the impeller, and means to prevent substantial longitudinal movement of the impeller with respect to the casing.

6. A centrifugal pump comprising an impeller and a casing surrounding the impeller, said casing having side walls adjacent the side walls of the impeller and divergent therefrom in the direction of the impeller axis, forming chambers at the side of the impeller continuously increasin in longitudinal cylindrical sectional area rom the periphery of the impeller for at least three-tenths ofthe impellenradius measured from the impeller periphery toward the impeller axis. 7

7. A centrifugal pump comprising an impeller and a casing surrounding the impeller, said impeller having fluid passages of continuously increasing sectional area from the eye to the exit of the impeller, said casing forming a chamber at the peri hery of the impeller of substantially uni orm section throughout the circumference of the impeller and said casing having side walls diverging with respect to the side walls of the impeller to form chambers adjacent the side walls of the impeller of continuously increasing lindrical sectional area in the direction 0 the impeller axis from the impeller periphery.

8. A centrifugal pump comprising a circular casing, and an im eller adapted to rotate within the casing an having passages therein continuously increasing in size from the eye to the periphery of the impeller, said casing having side walls divergent from the side walls of the impeller from the impeller periphery toward the impeller axis forming a path for the fluid being pumped of increasing longitudinal cylindrical section between the casing and the impeller from the periphery of the impeller toward the axis of the impeller and means to prevent substantial longitudinal movement of the impeller with respect to the casing.

In testimony whereof I have signed this specification.

ALLEN F. SHERZER.

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