US3163120A - Self-priming axial-flow pump - Google Patents

Description

Dec. 29, 1964 J, RICHARDS 3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 FIG.|

0000000 0000 o o 0000 on amp /0 o 150E110 oooqgb 0000 oo o ooeo 00 I7 uoooooo 0000000: o 0000 no 3 Sheets-Sheet l JOHN F). RICHHRDS ATTORNEYS Dec. 29, 1964 J. A. RICHARDS 3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 3 Sheets-Sheet 2 F'IG.7

FIG. 3

INVENTOR. JO/WV I). R/Cf/HRDS #M ATTORNEYS Dec. 29, 1964 J. A. RICHARDS 3,163,120

SELF-PRIMING AXIAL-FLOW PUMP Filed May 18, 1962 3 Sheets-Sheet 3 a FIG.4

I '1;I I 42 I N VEN TOR. JOHN H. RICK/HROS ATTORNEYS United States Patent insane Patented Dec. 29, 1964 3,163,126 SELEPRIIWING AXIAL-FLGW PUMP John A. Richards, Seattle, Wash, assignor to fiascade Manufacturing Company, Portland, Greg, a corporation of Qregon Filed May 18, 1962, Ser. No. 196,577 7 Claims. (Cl. 103-113) This invention relates to liquid pumps of the axial flow character. Pumps which are referred to as axial flow pumps can be either single or multiple stage; and may employ several types of prime movers, or impellers as they will be hereinafter termed. These several types can be classified as falling into four general categories:

(1) Propeller pumps (2) Mixed flow pumps, in which the impeller is partly centrifugal and partly screw (3) Open impeller turbines, these being centrifugal pumps with parts arranged in a manner which allows for axial flow (4) Closed impeller pumps, much the same as the open type excepting that both sides of the impeller are shrouded.

A characteristic of axial flow pumps is that the impeller must be kept flooded, wherefor on the occasion of each start-up, on an installation where the impeller is called upon to lift liquid from a source thereof which lies at a level below the level occupied by the impeller of the pump, it becomes necessary to prime the pump.

The present invention has for its general object the provision of an axial-flow pump incorporating in its design means by which the pump is made self-priming.

This and other more particular objects and advantages will appear and be understood in the course of the following description and claims, the invention consisting in the novel construction and in the adaptation and combination of parts hereinafter described and claimed.

In the accompanying drawings:

FIGURE 1 is a fragmentary longitudinal vertical sectional view illustrating one type of an axial-flow pump embodying preferred teachings of the present invention.

FIG. 2 is a fragmentary horizontal sectional view thereof on line 22 of FIG. 1.

FIG. 3 is an exploded view of parts of the pump ineluding the improvements of the present invention.

FIG. 4 is a fragmentary vertical sectional view illus trating another type of axial-flow pump embodying improvements of the present invention.

FIG. 5 is a horizontal sectional view on line 5-5 of FIG. 4.

FIGS. 6, 7 and 8 are diagrammatic views showing salient flow patterns; and

FIG. 9 is a fragmentary longitudinal vertical sectional view illustrating a modified self-priming version of an axial-flow pump of the type shown in FIG. 1, employing a reduced scale.

First describing the embodiment of FIGS. 1 through 3, there is shown a pump casing It) formed in its lower portion with a horizontal pump cylinder 11. The suction end of this cylinder is denoted by 12. Water or other liquid which is to be pumped is drawn through a suction pipe 16 into an ingress chamber 14 occupying a level above the pump cylinder. A flap valve 15 normally closes the outlet from this chamber. Between chambers 14 and 12 is a screening basket 17. A rotary impeller of the propeller type works in cylinder 11. Illustrated as a 3- stage impeller, the propellers are carried by a shaft 21 driven from an electric motor 22, and have the usual stationary diffusers 23 provided at the suction side of each propeller.

Journaled by its inner or front end on a bearing which is carried by a dowel pin 24, the propeller shaft 2 1 has its outer or aft end attached by a shear pin 25 to the armature shaft 2.6 of the motor. Such armature shaft is received through a sealing muff 27, and giving support to the muff is an adapter head 28 which fits in the after end of the pumping cylinder. This adapter head is axially spaced a rather substantial distance beyond the final propeller of the multi-stage series. Above the propeller shaft a baffle plate 30 occupies this space, being made integral with the head and lying radial to the propeller shaft in the longitudinal vertical plane of the shaft axis. Below the propeller shaft the head is desirably formed with a protruding toe portion 31 having a concave profile configuration when viewed from the side.

Water being pumped travels upwardly from the propeller chamber past the baffle plate to a discharge pipe 32. The proper length of the baffle plate, considered in a direction endwise to the travel path of the pumped water, will vary as between axial-flow pumps of differing designs. In the instance of the illustrated pump I find it desirable to provide a baffle plate of considerable length. To this end I provide within the pump casing a vertical discharge passage 33 lying in an intervening position between the bafile plate 30 and the discharge pipe 32. The longitudinal vertical plane occupied by the baffle plate coincides with a diameter of this passage, and at opposite sides of the passage, on this diameter, grooves 34 are let into the walls of the passage. A plate 35 fits in these grooves to produce a co-planar prolongation of the baffle plate. I have shown such prolongation as being perforated with multiple through-holes 36 of small diameter. It has been found that the bafile plateby which term I include both of the plates 3% and 35rnay be solid or may be either slotted or perforated in whole or in part. It is pointed out in this regard that it is only through experimentation that I have been so far enabled to determine the most effective pattern for any'given designof pump.

The functioning of the baflle plate will be best understood by pointing out that when an axial-flow pump is started the major portion of the priming fluid carries to the discharge side of the final impeller and then tends to rotate with the impeller. This is the case even though the pump may have a final diffuser, or straightener, located behind the final impeller, in that the diffusers of an axial flow pump have a short length measured along the direction of flow. Air from the suction side of the impeller becomes mixed with the priming fluid and by the rapid rotation of the mixture a centrifugal force is created. The liquid portion of this mixture, being more dense, tends to be driven to the outside, leaving the less dense air portion toward the center. My baffle plate, as one of its accomplishments, breaks up the centrifugal action and thereby obtains a more uniform mixture within the propeller chamber, with the net result that there is a higher percentage of the air at the outside of the mixture. The air is thus enabled to more readily escape through the discharge opening. A further accomplishment takes place as follows: the driving force of the impeller as it acts upon the air-liquid mixture imparts energy to the latter. Due to the plates close proximity to the shaft and to the surrounding wall the plate acts as a diverter and, depending on the shape, size, and placement of the plate, forces the mixture to leave the vicinity of the impeller and either pass through the perforations or over the edge which is distal to the impeller, in consequence of which the mixture leaves the highly turbulent impeller area and reaches a relatively calm zone containing liquid which is relatively free of air. The velocity of the mixture rapidly drops off as it passes through the near-static liquid and the force of gravity now overcomes other forces involved and a portion of the air leaves the mixture and escapes through the discharge opening. No primary fluid has been lost in this operation, and the described action of combining air from the suction side of the impeller with fluid on the discharge side, and moving this mixture from a zone of turbulence to one relatively free of such turbulence, with contained air escaping in the process, continues. The pump functions as an air pump until all air has been removed between the impeller and the source of liquid supply.

The above is a rather general summation of the priming result which I attain. In FIGS. 6, 7 and 8 I have diagrammed the motion pattern to which air and liquid is subject in the pump of the present invention as it moves between the suction chamber 12 lying at the front end and the discharge chamber 29 lying at the after end of the impeller.

During priming the pressure on the suction side is reduced, and a pressure difierential between the discharge and suction chamber is created. This diiierential varies from 'zero pressure, at the start of priming, to ceiling pressure occurring just before actual pumping of liquid takes place. This ceiling pressure will vary from installation to installation, and is a function of suction height and the pressure at the discharge.

Separating the suction from the discharge is a liquid seal. Created by the dynamic action of the impellers the liquid in this seal is represented in FIG. 6 by the arrows which surround the drive shaft, and rotates at very nearly the same speed as the impeller. In addition to this rotation a second circular motion is created. FIGS. 7 and 8 view the impeller from the side, and shown by these views are rotation patterns under two conditions, that of 7 being a condition in which no pressure difference exists between the suction and discharge side of the impeller, and that of 8 being a condition in which a pressure difference obtains. The x x axis lies at the longitudinal cenier of the impeller in the former instance, and tilts to the side of higher pressure in the latter instance. The change of pressure increases the circulation on the lowpressur'e' side. Thislurihalance in circulation creates a force-field which counteracts'the pressureforces. While for illustrative purposes the rotation with the impeller (FIG. 6) and the circulation within the impeller (FIGS. 7 and 8) are shown separately, the two motions actually are simultaneous. The absolute path of the fluid particles can best be described as a circular cork screw. A factor which must be recognized as affecting the degree of tilt of said axis is the density of the pumpage. The pumpage is a mixture of liquid and gas, and since gas is compressible the density is not only a function of the amount of gas but also the pressure at the location considered. The significance of said density factor is simply that on a multi-stage pump each pumping unit of the impeller has a different vortex pattern. '7

During the priming cycle the air in the suction line and suction chamber is evacuated by moving it through the liquid seal into the discharge chamber and out the discharge line. The liquid seal as such does not transport any gases from suction to discharge since the circulations described are confined to each pumping unit of a multi-stage impeller. V

The above is an over-simplified description of the real flow pattern. I visualize each individual liquid particle as having only a localized travel, moving a short distance toward the discharge and there releasing part of the gas to other liquid particles and then returning toward the suction side. A chain reaction of this nature will give much the same effect as the simplified circulation described. The straightener lips also create pulsations. These shock waves are feasibly beneficial for priming.

It should perhaps be again stressed that the accomplishments of the baffle plate are to (I) produce a discharge chamber of reduced turbulence so that the gas will separateffrom the liquid, (2) direct the separated gas into the discharge pipe, and (3) prevent the gas from becoming trapped or from being returned to the impeller.

It should be here pointed out that the air need not be discharged through the pumps normal discharge opening. Should such normal discharge opening be directed downwardly, as is the case with some horizontal pumps, a separate opening for escape of air can be provided on the upper side of the pump casing. Such an escape opening can likewise be provided on vertical pumps in which the normal discharge turns abruptly downward. in either such case, for automatic operation, it is only necessary that means such as a float or a pressureresponsive check valve be provided to cause the air-vent opening to close when the prime has been made. FIG. 9 illustrates teachings of the present invention applied to a horizontal pump of the above-mentioned type having its discharge opening directed downwardly, and indicating the manner in which an air-escape check valve is applied. Such check valve, denoted by (it), is set so as to close in response to a rise of pressure at the discharge or pressure side of the pump to a predetermined level (this being the ascertained ceiling pressure hereinabove referred to) and is or may be fitted with a regulating control handle 61. The discharge pipe 32' has a U-bend to produce a trap in which air-free liquid collects during the pumps self-priming action. The pump casing is denoted by 1%, and functioning counterparts of the plates 30 and 35 are denoted by 33' and 35 respectively.

In FIGS. 4 and 5 I have shown a vertical-type axialfiow pump equipped with a bafile plate embodying teachings of the present invention. The pump is shown as e-ing equipped with a single-stage propeller 4t) and pairs of diametrically opposed ditfusion vanes, as 41-42 and 43-44, above and below such propeller. The lineshaft 45 which drives the propeller from a top-mounted motor (not shown) is enclosed in a shaft tube 46 occupying a position axial to a discharge column 47. A long-radius discharge elbow 48 extends laterally from the upper end of the discharge column in the vertical plane occupied by the diliuser vanes. The bathe plate, designated by 50, is applied as a co-planar prolongation of the one of said upper vanes which extends radially from the shaft tube 4d on the same side as that occupied by the discharge elbow. Some vertical-pump designs might dictate that this hafile be extended beyond the discharge column into the throat of the discharge elbow.

A vertical pump employing the bafile plate of the present invention must be so designed that, when stopped, a body of priming liquid will be retained in the casing in a position to be picked up by the impeller when the pump is again started up. This can be accomplished in a number of ways as, for example, by forming a U-trap in the suction pipe 51.

A feature of the present invention which is highly important is that the pump will not lose prime should gas enter the suction line. The pump clears its passages automatically and resumes delivery of the pumped liquid.

It is believed that the invention will have been clearly understood from the foregoing description of the illustrated embodiments. Changes in the details of construction may be resorted to without departing from the spirit of the invention and it is accordingly my intention that no limitations be implied and that the hereto annexed claims be given the broadest interpretation to which the employed language fairly admits.

What I claim is:

1. In combination with the rotary impeller of an axialflow pump, and a casing housing said impeller formed so that a body of the liquid to be pumped is at all times available to the impeller as a prime for the pump: a stationary diverter contained within the casing in a discharge passage travclled by pumped liquid as the latter initially leaves the discharge end of the impeller and formed so as to (l) interrupt impeller-induced centrifugal motion of a fluid composed of said priming liquid mixed with air drawn by the impeller from the suction side of the pump and (2) lead said mixture to a zone relatively free of impeller-induced turbulence occupying a level no lower than the discharge end of the impeller and from which the contained air is free to escape by ascension.

2. Structure according to claim 1 in which said diverter extends for a distance along said passage suflicient in length to substantially isolate said zone from the turbulence imposed by the impeller upon the liquid-air mixture.

3. Structure according to claim 2 in which the diverter is in the nature of a baflie plate extending into approximate touching contact with the wall of the passage on a diameter of the latter.

4. In an axial-flow pump, a rotary impeller mounted to turn about a horizontal axis, a pump casing housing said impeller providing inflow and outflow passages to and from the impeller, said outflow passage including a vertical section rising to a height elevated above the chamber in which the impeller Works and connecting with said chamber by an elbow section, and a stationary diverter serving a bafiie function upon a liquid-air mixture driven by the impeller and comprising a plate occupying a diameter of the vertical section co-planar with a diameter of the impeller chamber, said plate depending from the vertical section through approximately the upper onehalf of the elbow section and at its leading edge extending into such close proximity of the impeller as to interrupt centrifugal motion of liquid-air mixture leaving the discharge end of the impeller.

5. The axial-low pump of claim 4 in which said plate is perforated at least in part.

6. The axial-flow pump of claim 4 in which the plate is imperforate other than for a portion thereof which lies in such distal relation to the impeller as to be outside a zone of turbulence reflecting said centrifugal motion of the liquid-air mixture.

7. In an axial-flow pump, a rotary impeller mounted to turn about a vertical axis, a pump casing housing said impeller providing an inflow passage to the lower end of the impeller and an outflow passage from the upper end of the impeller, a vertical drive shaft to the impeller disposed centrally of the outflow passage, and a baffle plate occupying the space between the shaft and the outer wall of the outflow passage on a radius of the former and extending upwardly into said outflow passage from approximately the upper end of the impeller, the baflie plate having considerable length measured along the axis of the shaft, means being provided by which a body of liquid to be pumped is at all times available to the impeller as a prime for the pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,571 Mann May 8, 1945 2,428,487 Fernstrum Oct. 7, 1947 2,461,925 Rupp Feb. 15, 1949 2,627,812 Mann Feb. 10, 1953. 2,627,817 Mann et al Feb. 10, 1953 2,934,021 Conery et a1 Apr. 26, 1960 2,945,448 Frederick July 19, 1960 FOREIGN PATENTS 601,653 Great Britain May 11, 1948

Claims (1)

1. IN COMBINATION WITH THE ROTARY IMPELLER OF AN AXIALFLOW PUMP, AND A CASING HOUSING SAID IMPELLER FORMED SO THAT A BODY OF THE LIQUID TO BE PUMPED IS AT ALL TIMES AVAILABLE TO THE IMPELLER AS A PRIME FOR THE PUMP: A STATIONARY DIVERTER CONTAINED WITHIN THE CASING IN A DISCHARGE PASSAGE TRAVELLED BY PUMPED LIQUID AS THE LATTER INITIALLY LEAVES THE DISCHARGE END OF THE IMPELLER AND FORMED SO AS TO (1) INTERRUPT IMPELLER-INDUCED CENTRIFUGAL MOTION OF A FLUID COMPOSED OF SAID PRIMING LIQUID MIXED WITH AIR DRAWN BY THE IMPELLER FROM THE SUCTION SIDE OF THE PUMP AND (2) LEAD SAID MIXTURE TO A ZONE RELATIVELY FREE OF IMPELLER-INDUCED TURBULENCE OCCUPYING A LEVEL NO LOWER THAN THE DISCHARGE END OF THE IMPELLER AND FROM WHICH THE CONTAINED AIR IS FREE TO ESCAPE BY ASCENSION.

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