US1914919A - Centrifugal pump - Google Patents

Description

June 20, 1933. T. M. HEERMANS 1,914,919

CENTRIFUGAL PUMP Filed oct. so, 1951 u f' EFF/c/ENCr/a 6 Y 23 HEAD /N FEET Patented June 20, 1933 UNITED STATES PATENT OFFICE THOMAS M.-HEERMANS, OF WAUWATOSA, WISCONSINQVASSIGNOR TO ALLIS-GHALHERS MANUFACTURING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF DELAWARE CENTRIFUGAL PUMI.

VApplication filed October O, 1931. Serial No. 572,024.

A This invention relates in general to the art of centrifugal pumps and relates more specilically to improvements in centrifugal pumps used for pumping liquids.

An object of the invention is to provide a more or less tangentialdischarge of a. pump, as related above, with novel means for changing its capacity.. t

Another obiect of the invention is that the means for changing the capacity of a centrifugal pump comprises a capacity changing Venturi design nozzle formed either to be readily insertible in the discharge outlet of the pump or so as to be readily externally attachable to the ldischarge outlet. Another object ofthe invention is to form the discharge outlet and provide tbe same with initially thick walls so that the desired capacity changing of the pump may be eifected while retaining its Venturi design b v merelyx reaming or machining out the outlet by.

the required amount.

Anotherobject of the invention is to provide a centrifugal pump having operating characteristics which well ada t the pump for use in furnishing a substantlally constant quantity of a liquid while operatin at satisfactory efficiencies and against hea s of different magnitudes.

substantially tangential outlets of centrifugal pumps with a Venturi form or design of flow passage having its constricted portion immediately adjacent the cut-off of the pump that p desired results and additionally provides designs of .outlets for centrifugal `pumps and/or means cooperating .with such outlets for changing the capacity'of the pumps Without necessitating adjustments of the pump casing or the substitution of different runners. And by merely changing the area of the constriction of the Venturi form/or design o f iiow passage and correspondingly changing It has been found that providing the outlets accordingi to this invention has the further advantage in that pumps provided therewith have operating characteristics which show that they may be operated over appreciable ranges of head Without an accompanying appreciable change in quantity of liquid pumped per unit of time over these ranges. This makes centrifugal pum s pro-l vided With the improvements constituting this invention adapted to a lield from which centrifu al pumps were heretofore considered to e excluded, namely, to the field of supplying constant quantities of liquid, regardless of slight changes in the pressure at the outlet.

Other objects and advantages ofthe present invention will become apparent from a consideration of the detailed description hereinafter found in the specification and of the drawing accompanying the same and on which like reference numerals refer to similar parts or elements in all of the several views.

Fig. 1 is an end elevational view of a centrifugal pump, the tangential discharge outlet thereof and the novel Venturi nozzle insertible in the outlet being shown in longitudinal cross-section. j

Fig. 2 is a longitudinal cross-sectional view of a dischargeoutlet of a .centrifugal pumpwith a slightly modified form of Venturi liozzle insertible in the outlet, the nozzle also being shown in longitudinal cross-section.

Fig. 3 is a longitudinal cross-sectional view of a slightly different discharge outlet of a centrifugal .pump with another modified form of vVenturi nozzle attachable to and located entirely externally of the discharge outlet, the nozzle also being shown in longitudinal section.

Fig. 4 is a longitudinal sectional view of a discharge outlet having a Venturi form of flow passage cast integral with the nozzle portion, of a centrifugal -pump of relatively large size and capacity.

Fig. is alongitudinal sectional view of a discharge outlet having aI Venturi form of flow passage -cast integral with the nozzle portion, of a centrifugal pump of relatively small capacity.

Fig. 6 is a graph of operating curves of a centrifugal pump having a discharge outlet as shown in Fig. 1 and also a graph of operating curves of the same centrifugal pump with the outlet thereof provided with an insertible Venturi nozzle as shown in Figs. 1 and 2.

. Referring to Fig. 1 the centrifugalpump casing 1, of usual construction, is provided with a shaft2 alined with the suction inlet 3 of the pump. The shaft2 carriesarunner 4 having vanes 5 which act upon the liquid flowing into the easing through the inlet 3, when the runner 4 is rotated at high speeds, and force the liquid into the collector chamber 6 surrounding the runner 4. vThe collector chamber 6 terminates in a tangential discharge outlet 7 having a boss 8. The boss 8 is provided with interior threads 9 preferably tapered as shown for direct cooperation with complementary external threads l0 formed on an intermediate portion ofa novel Venturi nozzle 11. The enlarged portion 12 of the nozzle 11 is provided with internal threads 13 also shown to be tapered, to facilitate the application of the conduit member `14 to the nozzle 11. The reduced portion 15 of the nozzle 11 is tapered to permit its being received within the tapered discharge outlet 7. The flow passage of the nozzle 11 is of a Venturi form having a constriction 16 1ocated closely adjacentV to the cut-off 17 of the pump casing, which cut-off is vrounded as shown to prevent the formation of eddies and so as to desirably cooperate with the adjacent mouth portion formed by the curved annular inner surface terminating inwardly of the constriction 16. Outwardly beyond the constriction 16 the-flow passage of the nozzle 11 is provided by a diverging annular surface 18 which forms the regainer section of the nozzle. It is in this section of the nozzle 11 where the velocityhead is substan- Venturi nozzle 11 and discharge outlet 7 are l shown. The intermediate portion of the nozzle 11 instead of the screw threads is provided with an external, apertured annular flange 19 and the outlet 7 is provided .with an external, apertured annular flange 20 to which the nozzle 11 is secured by bolts 21 passing through the apertures in said flanges. Similarly the enlarged outer end of the nozzle 11 is provided with anexternal, apertured annular flange 22 registerable with an annular flange 23 on the conduit member 14 so that said member may be secured to the nozzle 11 by bolts 24 passing through the apertures in said flanges. The parts and their arrangement otherwise are the same as shown in Fig. 1.

In Fig. 3 a further modified form of dis-- charge outlet is shown in which the cut-off 17 of the pump is located closely'adjacent to an annular supporting surface 25 provided directly by a portion of the' material of said cut-olf and an external flange 26 terminating the discharge outlet 7. A. Venturi nozzle 11 having an external. annular flange 27 terminating the same adjacent the constriction 16 thereof may therefore be advantageously employed in a centrifugal pump provided with a discharge outlet as shown in this figure. The nozzle 11 may be secured to the outlet 7 by any suitable means cooperating directly with the flanges 27 and 26. The opposite end of the nozzle 11 may likewise be provided with an external. annular flange 28 for direct cooperation with a like flange 23 on a conduit member 14 for the purpose of fixedly securing the member 14 to the nozzle 11.

l Fig. 4 shows the discharge outlet7 of a centrifugal pump wherein the desired Venturi form or design of flow passage is provided directly -by the inner surface of the outlet. This surface provides a constriction 16 adjacent the rounded cut-olf 17 of the pump, said constriction terminatingl at one side thereof in a regainer portionf18 as in the detachable nozzles of Figs. 1, 2 and 3. Similarly to the construction of Figs. 2 and 3 the discharge outlet 7 in this construction is provided with an external, annular flange 30 and the conduit meinber 14 with a like flange' 23 whereby thel member l14 may be secured to the discharge outlet 7 by means cooperating with the flanges '30 and 23.l The thought underlying this construction is that the core box for forming the nozzle portion of a centrifugal pump not having a. Venturi form of discharge outlet flow passage or having such an outlet, may be modified bymaking the discharge outlet forming pattern portion of the core box detachable from the collector forming pattern portion of theA core box. In this way by merely substituting for the discharge outlet pattern portion of the given core box a. discharge outlet core portion having the desired Venturi form a: centrifugal pump having the same interior collector` l passage but having the desired Venturi form or flow passage in its discharge outlet may subsequently be readilyI cast. This construction'scheme is, as stated before, especially suitable in the constructien of the larger s izes of centrifugal pumps.

Fig. 5 similarly to Fig. 4 shows the interior surface of the discharge outlet 7 of a cen- 5 trifugal pump as directly providinga Venturi form of flow passage. It differs from the showing of Fig. 4 primarily in that the cut-off 17 of the pump is removed a greater distance from the constriction 16 of the Venturi form of flow passage, provided directly by the discharge outlet, so that the mouth 31 thereof leading into the constriction 16 is of'a pronounced conicalform. The discharge outlet 7 may be provided with an external iange 30 and the conduit member 14 4with a cooperating flange 23 for the purpose described in connection with the similar showing of Fig. 4. A construction as shown in F ig ,5 is especiallysuitable for use in pumps" of smaller capacities than those in which the construction shown in Fig. 4 is suitable. The walls of the discharge outlet 7 of t lis ligure, it will be noted, are shown to be relatively thick so that the original capacity of the pump may be changed by reaming or machining out the material forming the regainer surface portion 18 so as to obtain the desired area of the constriction 16 in the reduced state ofthe discharge outlet. Advantages from the standpoint of' the manufacturer of centrifugal pumps:

Say a years business in three sizes of small pumps is as follows: 125 pumps having 11/2" diameter outlets; 100 pumps having 2 dlam- 5 eter outlets and 75 pumps having 3 diameter outlets, and that these umps on stock orders of twenty-live cost $125.00, $130.00 and $135.00 respectively, to-build. Now if the same range of capacities can be covered by a L3 single 3" pump with two Venturi nozzles giving respectively, the capacities of the smaller outlet diameter pumps mentioned, it means that three hundred pumps of one size can be manufactured, larger stock orders can be plut 5 through at one time, and more special tools can advantageously be provided to reduce the cost where only one size of pump is considered l as against three pump sizes. The economies resulting from producing one size in larger stock orders obviously'should bring the production cost of the three hundred 3 pumps below that of the three hundred pumps divided among the three sizes mentioned.

f3 three different pumps to take care lof three distinct capacity requirements.

Advantages to the user: z Thev novel Venturi nozzle permits of very materially and appreciably. extendingthe C5 range 'of utility vof a particular casing and Advantages to the manufacturer and to :theV

runner, since the 2 outlet diameter-pump, for example, may have a rating of 200 G. P. M. at 7 5 head and 17 50 R. P. M. This same runner in a'dilferent suitable casing would be good for 400 G. P. M. at 300 head by using a suitable motor to increase the speed of the runner to 3500 R. P. M. The

different suitable casing would be required.

to take care efficiently of the increased output of the runner as by using theworiginal casing designed for 200 G. P. M. the eiiciency would be found not to be satisfactory and the output of the runner exceeding its rated output at the doubled speed would not be desirable. However, by using a capacity reducing Venturi nozzle, the capacity of the pump using the original casing and the same runner while o erating the runner at the doubled speed coul be maintained at approximately 200 G. P. M. its normal output rating and eflicient performance realized. Here again it is seen that a single casing and runner can be made to take the place of two casings and with the single casing two ranges of per formance realized of 75 head, at 200 G. P'. M. capacity at 1750 R. P. M. and 30'0 head, at 200 G. P. M. capacity at 3500 R. P. M.

Further, for small, capacity, high head pumps, it is usually necessary to make the runner in two pieces either riveted or welded together, if a small enough opening at the periphery is to be obtained to keep the ca pacity within the desired limits.` Aboutl as narrow an outside or peripheral opening at the runner outlet. that-can be provided by casting the runner in one -piece is an o ening 3/16 x 7/32 yvide. A- runner or 75 G. P. M. 300 head pump should be about 7/64" Wide at the outside.) The wider one piece runner hasseveral advantages over the narrow runner comprising two pieces fastened together in that it has a lower manufacturing cost, is better mechanically and is less sub]ect to stoppage of its passages by small foreign particles contained in the liquid being pumped. The wider runner can be used in `a pump provided with the disclosed novel capacity controlling Venturi nozzles as this nozzle enables the capacity of a pump having a wider runner than a runner which could be used in the standard design of pump, to be eiliciently controlled. In other words, the novel capacity changing pozzle herein disclosed is advantageously employable to secure `a comparatively small capacity from a pump which would not be practical to cast to smallenough dimensions for best efficiency whcen using a normal design.

Tphatithe novel Venturi. nozzle herein disclosed is both a capacity anda head changing device can be s'een from t'liperformance curves shown in Fig. Q. Thev dot-,dash curves shown .in this figure are vplotted from test data of a,standard.\centrifugal pump having the straight line-e1ement 'discharge-outlet flow-passage substantially as shown in Fig. 1 and havin a 2 diameter linlet and outlet and 3500 R. M. normal speed rating for its runner. While the solid line curves shown in this -figure are plotted from test data of this same pump operating at its rated speed 3500 R. P. M. but with a 2 x 11/21` Venturi nozzle inserted as shown in Fig. 1 inthe discharge outlet of the pump. The.- capacity values in G. P. M. are plotted as abscissae and the correspondingr head values, eiiiciency values l tively, the eiiiciency, head and brake horse# lpower curves for the standard pump and the and brake horsepower values, as ordinates. The curves designated E, H and B are respecduced slightly from about 114pto 106 but it may here be stated that a similar type of pum i except for the size Vwhich would ordinari y be used for 60 G. P. M. and designed for best efficiency at this 60 G. P. M. capacity rating gives 102 head with 58% eicliency. The saidlarger size pump for which the solid line curves were drawn and having the stated with the stated Venturi nozzle has itsmaXinovel nozzle at G. P. M. capacity, therefore has a 1% higher ei'ciency at this capacity rating than a pump which would ordinarily beused for this capacity rating of 60 G. P. M. The brake horsepower curve to the break-ott pointfor the stated standard pump when operated with the stated nozzle and at' the same speed 3500 R. P. M. is seen to coincide with the brake horsepower curve for the `stated standard pump whenoperated at this speed. Between'GO G. P. M., the capacity at which the stated sta-nd ard pump provided mum eiciency when operated at 3500 R.' P. M., and about 85 G. P. M. capacity, the curves e, h and b are seen to have" knees, the portions ofthese curves below the knees thereof coincide in vertical line portions of their lengths. This characteristic of the curves, as clearly shown, for-the standard pump operatingwith the stated novel Venturi nozzle in the discharge outlet has the following significance.

The kneefof the head curve H for the stated standard lpump is seen to terminate at about 20 of head and at about 165 G. P. M. capacity at which point the runner is handling all of the water this runner is capable of pass'- ing and this is not a desirable or satisfactory operating condition. The knee of the curve z. for the stated standard pump using the stated Venturi nozzle is, however, seen to terminate at about 7 0 head and at about 85 G. P. M. capacity, which is .well within the limits the runner will handle satisfactorily so there should be no disadvantage in operating this latter pump at a break-olf capacity of 85 G. P. M. if desired. The adaptability of a centrifugal pump having the disclosed Venturi nozzle in fields where high efficiencies are relatively unimportant as compared with the desirability of maintaining a substantially constant output of pumped liquid in G. P. M., therefore, becomes apparent. This may be done by. umps designed for some avera ve pressure o the pressure range below te knees of the head curve and zero pressure head with the Venturi nozzles herein disclosed fixing or determining the delivery capacities of the pumps.

Having now fully described the various modifications of the novel Venturi design of discharge outlet for centrifugal pumps and set forth the principle of operation of the invention as measured by these modilications and stated their advantages and applica- Abiilities, itis to be further understood that the invention is not to be limitedto the exact details of construction and -of operation herein shown and described, for various modifica.- tions within the scope of the claims may occur to persons skilled in the art to which the invention apperta'ins.

It is claimed and desired to secure by Lety ters Patent:

1. In a centrifugal pump, a substantially tangential discharge outlet, said outlet being pump.

2. In a centrifugal pump, a substantially tangential discharge outlet, said outlet havf ing associated therewith a Venturi design of flow surface changeable to vary the capacity of the pump.

3. In a 'centrifugal pump, a substantially tangential discharge outlet, and a capacity changing hollow member attachabl'e to said outlet.

4. In a centrifugal pump, a substantially tangential discharge outlet, and a hollow member having a Venturi design of flow surface, said member' being attachable to said outlet and being provided for .the purpose of changing the capacity of the pump.

5. In a centrifugal pump, a substantially tangential discharge outlet having an inner surface constituted by substantially straight line elements, and a capacity changing hollow member attachable to said outlet.

6. In a centrifugal pump, a substantially tangential discharge outlet having an inner surface constituted by substantially straight line elements, and a hollow member having a Venturi design of flow surface, said member being attachablo to said outlet and being provided for the purpose of changing the capacity of the pump.

7. In a centrifugal pump, a discharge outlet having an inner surface constituted by substantially straight line elements, and a hollow member having a. Venturi design of iiow surface, said member being attachable to said outlet and being provided for the purpose of changing the capacity of the pump.

8. In a centrifugal pump, a substantially tangential discharge outlet, and a capacity changing hollow member insertible in said outlet.

9. In a centrifugal pump, a substantially tangential discharge outlet, and a hollow member insertible in said outlet, said member being provided with. a Venturi design of iow surface and being insertible for the purpose of changing the capacity of the pump. p

l0. In a centrifugal pump, a discharge outlet, and a nozzle having a Venturi design of flow surface, said nozzle being insertible in said outlet for the purpose of changing the capacity of the pump.

11. In a centrifugal pump, a substantially tangential discharge outlet, a cut-0E forming a portion of said outlet, said outlet being provided with a Venturi design of changeable liow surface, the constriction forming portion of said surface being located adjacent said cut-off, said changeable surface being provided for the purpose of chang.' g the capacity of the pump.

12. In a centrifugal pump, a substantially tangential discharge outlet, a cut-off forming a portion of said outlet, said outlet being provided with a Venturi design of changeable fiow surface, said surface and said cut-off being formed and related to prevent the formation of eddies adjacent the cut-o, said changeable surface being provided for the purpose of changing the capacity of the pump.

13. In a centrifugal pump, a substantially tangential discharge outlet, said outlet having a Venturi design of-flow surface and being comprised of relatively thick walls, the capacity of the pump, while maintaining a Venturi design of flow passage, being changeable by operating directly upon the material constituting the walls of said outlet.

14. In a liquid pumping system, a centrifugal pump, the discharge outlet of said pump being provided with changeable means having a Venturi design of iow surface having a constriction area less than the fixed normal area of the outlet of the pump, said means being provided for the purpose of changing the capacity of thepump.

15. A centrifugal pump comprising a casing, a substantially tangential discharge -outlet for said casing, an inlet to said casing,

a runner rotatable within said casing, a conduit member adapted to be connected to said discharge outlet, the flow passage between the inventor is aiiixed hereto.

THOMAS M. HEERMANS.

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