US1839514A - Device for preventing short circuiting flow around impellers - Google Patents

Description

jam. 5, 1932. A. R. was 1,839,514

DEVICE FOR PREVENTING SHORT GIRCUITING FLOWAROUND IMPELLERS Filed Jan. 23, 1929 1N VE/w-oe: [4277102 8. A E/s,

illustrated a preferred embodiment of my invention, 7

Fig. 1 is a utility view, partially in section, illustrating one type of pump in which my invention is particularly applicable.

Fig. 2 is a cross-sectional view illustrating the details of my invention.

Fig. 3 is a sectionalview taken on the line 3-3 of Fig. 2. a a

Fig. 4 is a graph on which a curve of pressure against output is plotted.

Referring particularly to Fig. 1, Ifhave illustrated a deep-well turbine pump comprising a pump section 10, positioned in the lower end of a well 11, and inside a well casing 12. The pump section is supported by a suitable discharge tube 13 which extends upward to the surface of the ground and is connected to a pump head 14. A shaft 15 extends from the pump section 10 upward inside the discharge tube and is rotated by a means 16. The pump section 10 is formed The details of these pump bowls may best be understood by reference to Fig. 2 wherein two of the pump bowls 19 are illustrated as being connected together by bolts 20 passing through an upper flange 21 of the lower bowl and being threadedly received into the lower walls of the pump bowl thereabove. An impeller chamber 22 is formed in each of the pump bowls, a lower portion of this impeller chamber being defined by an upper wall 23 of the pump bowl 19 immediately therebelow. Each of the impeller chambers 22 communicates between an intake passage 24 and a dis charge passage 25, these passages being formed in a pump bowl structure 26 which comprises the different pump bowls 19.

Positioned in each impeller chamber 22 is an impeller 30 having'a hub 31 which is secured to the shaft 15 by any suitable means such as a key 32. The lower portion or eye 33 of the impeller extends into a bore 34 in a manner to leave a primary clearance space 35 therebetween, this clearance space being ordinarily small.

Formed through the impeller is an impeller passage 36 which has vanes 37 therein. The

passage 36 has an inlet-port 38 in communication with the intake passage 34 and has an outlet port 39 in communication with'the dischargepassage 25. V

. When the shaft 15 is rotated, each of the impellers draws well fluid upward through the adjacent intake passage and discharges this fluid into the adjacent discharge passage 25. This particulartype of centrifugal impeller has the property of centrifugal- 1y discharging thewell fluid from the outlet port '39 at a relatively high total head.

At the point of discharge from the impeller, this total head is divided into a high velocity head and a rather low pressure head. As soon as this fluid reaches the discharge passage 25 the pressure head becomes high and the velocity head lowers a corresponding amount. Thus, the pressure in the discharge passage 25 invariably higher than the pressure in the intake passage 24, and this differential pressure has heretofore invariably set up a short-circuiting flow around the lower shroud 42 of the impeller 30 in a direction indicated by the dotted arrow 43. This flow takes place through an auxiliary chamber 44 formed between the lower shroud 42 and the upper wall 23. Due to the fact that the velocity head of the fluid changes into a high pressure head ver soon after enterin the dischar e oas- J7 a .z: 1

sage 25, any abrasive particles which are carventional type of pump are allowed to drop into the chamber 44. Heretofore great difficulty has been encountered due to these abrasive particles collecting in the chamber 44 and wearing the upper wall 23, and especially the lower shroud 42 of the impeller.

Various types of labyrinth packing have been devised for decreasing this short-circuitingflow, but it has been impossible to eliminate this short-circuiting flow. F urthermore, these packings are invariably placed adjacent the eye of the impeller, thus allowing an accumulation of sand below this impeller even though the short-circuiting flow is decreased. 7

My invention comprises the formation of a skirt 47 on the outer portion of the lower shroud 42, this skirt extending in close proximity to a cylindrical wall 48 of the impeller chamber 22. A secondary clearance space 49 is formed therebetween, this clearance space ordinarily being in the neighborhood of several thousandths of an inch. Formed through the skirt 47 are one or more upwardly inclined openings 50. As best shown in Fig. 2, the inner ends of these openings communicate with the auxiliary chamber 44, while the outer ends of these,- openings communicate with the clearance space 49. The openings 50 act as an auxiliary pumping means tendstage, and as abscissa the output in gallons.

A typical test curve has been plotted, this curve having a decided droop indicating that as the output of the impeller is increased,

the total head developed by this impeller decreases. In fact, with the particular impeller tested in securing the information disclosed in Fig. 4, the total head per stage un der no output was feet. As the output of the impeller increases, or, in other words, as more fluid passed through the passage 36 thereof, the total headperfstage dropped.

When the output was900 gallons per minute, the total head was in the neighborhood of 36 feet instead of 60 feet as pre'viously. if

ft is well established that the total-head developed by an impeller is a function of, and

nearly proportional to, the maximum radius 1 I below the mouth of the openings 50 extends of the passage 36 therein. In O 'tl16IWOI'ClS, with a given output, the total head developed by an impeller is proportional tothe distance between the center of rotation of the shaft and the mouth of the outlet port 39. I

In Fig. 2 l have illustrated an impeller,

' the mouth of the outlet port 39' of which is not parallel to the axis of rotation, but instead converges upward,'so thatthe upper portion 52 of this mouth is closer to the axis of the shaft 15 than isthe lower portion 53 of this mouth. With this particular type of.

impeller, the total head developed thereby with a given output is substantially proportional to the mean distance between the axis of rotation of the shaft and the portions 52 "and. 53 of the mouth of the outlet port 39.

The outer periphery of theskirt 44 is positioned at a radius which is greater thanthis mean difference, and it therefore follows that the pressure developed by the centrifugal.

force of the fluid in the openings is always greater than the pressure developed in the.

passage 36 of the impeller, even though the flow through this passage 36 is reduced to,

substantially zero. In other words,the impeller 30 at zero output might develop a head I of 60 feet in the passage 86, but the head developed in the openings 50 would exceed this value by several feet due to the fact that the mouths of these openings are at a greater radial distance fromthe shaft than the mean distance between the shaft and'the portions 52 and 5". This causes a flow of iiuid upward through the clearance space 35 and into the chamber 4%, this fluid beingdischarged through the openings 50 and into the clearance space 49.

It should be understood that the volume of fluid passing through the openings 50 is at all times very small due to the proximity of the cylindrical wall 48 to the mouthsof the openings 50, and that therefore the total head developed by the openings 50 is not materially decreased'by a large output therethrough. In other Words, the pumping means formed by the openings 50 wouldfollow a curve 59 shown in Fig.4, this curve lying above the curve and extending only a very short distance along the abscissa scale.

Whenthe output of the impeller increases,

the total head developed thereby also decreases, thus accentuating the diiference'in values ofhead developed by the passage 36 and the openings 50.

To insure that the flow of fluid passing through the openings 50 b e directed upward into the discharge passage 25 rather than the clearance space 35. ,VGlOCltY which exists between the streams of being short-circuited around the lower edge of the skirt 47, I incline theseopenings up- {ward, as best indicated in Fig. 2. Furthermore, the mouth of each'opening 50 is only a small distance below a ledge 60 defining the upper end of the cylindrical wall 48, while the portion of the periphery of the skirt 47 a material distance downward in close "proximity to the cylindrical wall 48.

The clearance space 49 in effect actsas a sealing means, due to the very small width of this space, this sealing means being ordinarily filled with a fluid. The sealing area larger, however, than that above the mouth of the openings 50, inasmuch as these openings are positioned as heretofore described. There 19 thus'very little resistance to flow upwardthrough the clearance space l9 from;

around the lower edge of the skirt M.

It should thus be apparentthat any fluid entering the auxiliary chamber a l will be dis charged through the openings 50 lrrespective of the amount of flow through tl e passages 36-of the impeller. it should further be ag-J parent that in my invention the directionof flow throughthe chamber is'reversed from,

the ordinary direction of flow. In other words, the pumping means, draws the fluid through this chamberin a direction indicated by the arrow .62.

Furthermore, by makingv the clearance space el9 extremely narrow, this clearance vspace restricts the flow of fluidthrough the chamber 44: thus insurin a low velocit in a o m ihe dlh'erential fluid passing through the intake passage 2i and the clearance space 35 1S usually greater than ten feet per second. In f'act,the velocity of the fluid in the clearance space 35 is so low that abrasiverparticles will not be raised thereby, but will gravitate therefrom and into thelarger and faster fluid stream passing through the intake passage 24-. This action'is important to'this invention and pr vents any mate wear between the skirt r? and the cylindrical wall 48. It is thus im possible for any abrasive particles to accumulate between the upper wall 23 and the lower shroud of the impeller and the wear which heretofore took place due to this accumulation of abrasive particles is ent'rely eliminated. I

The simplicity of the means for accomplishing these desirable results should be apparent. No additional working parts over those ordinarily used are needed in building this type below the mouth of the openings 50is much :3

aids in preventing a'short-circuiting flow more machine work is required on the pump j let port therein; a pump bowl structure in' which said impeller rotates, there being an auxiliary chamber between said impeller and said pump bowl structure, said structure providing an intake passage and a discharge passage communicating respectively with said inlet and outlet ports; and an auxiliary pump means for drawing fluid intosaid auxiliary chamber from said intake passage and discharging it into said discharge passage.

2. In a turbine pump, the combination of: a pump bowl structure providing an impeller chamber; an impeller having upper and lower shrouds and being adapted to rotate in said impeller chamber; and means for setting up between said lower shroud and said pump bowl structure a flow of well fluid which parallels the flow of said well fluid through said impeller.

3. In a turbine pump, the combination of an impeller having an inlet port and an outlet port therein; a pump bowl structure in which said impeller rotates, there being an auxiliary chamber between said impeller and said pump bowl structure, said structure providing an intake passage and a dischargepassage communicating respectively with said inlet and outlet ports; and a skirt on said impeller and having an opening. therein actmg to centrifugally discharge fluid from' said auxiliary chamber into said discharge passage.

'4. In a turbine pump, the combination of an impeller having an inlet port and an outlet port therein; a pump. bowl structure in which said impeller rotates, there being an .45

auxiliary chamber between said impeller and said pump bowlstructure, said structure providing an intakepassage and a discharge passage communicating respectively with said inlet and outlet ports; an auxiliary pump means for drawing fluid into said auxiliary chamber from said intake passage'and-discharging it into said discharge passage; and means for restricting the flow of fluid pumped by said auxiliary pump means so that-the pressure developed thereby is always greater than the pressure set up in said outlet port of said impeller.

5. In a turbine pump, the combination of: an impeller having an inlet port and an outlet port therein; a pump bowl "structure in which said impeller rotates, there being an auxiliary chamber between said impeller and said pump bowl structure, said structure providing an intake passage and a discharge passage communicating respectively with said-inlet and outlet ports; a skirt on said impeller. and having an opening therein acting to centrifugally discharge fluid from said auxiliary chamber into said discharge passage; and means for maintaining the flow of fluid through said opening substantially constant. p V

6. In a turbine pump, the combination of: a pump bowl structure defining an impeller chamber bounded on one side by a cylindrical wall; an impeller adapted to rotate in said impeller chamber; askirt on said impeller rotating in close proximity to but spaced from said wall; and an opening through said skirt and adapted to centrifugally discharge fluid between said skirt and said cylindrical wall.

"7. In a turbine pump, the combination of: a pump bowl structure defining an impeller chamber bounded on one side by a cylindrical wall; an impeller adapted to rotate in said impeller chamber; a skirt on said impeller rotating in close proximityto said wall; an opening through said skirt and adapted to centrifugally discharge fluid between said skirt and said cylindrical wall; and a settling space through which said fluid must pass beforereaching said opening.

8. A combination as defined in claim 6 in which'said impeller has anooutlet port discharging into a discharge passage of said pump bowl structure and in which said opening is inclined in a manner to force said fluid into said discharge passage.

9. In aturbine pump, the combination of: a pump bowl structure providing an impeller chamber, a portion of which is defined by a bore in said structure and a cylindrical wall concentric with said bore; an impeller adapted to rotate in said chamber, said impeller having an eye extending into said bore in a manner to form a primary clearance space therebetween communicating with an intake passage and with an auxiliary chamber formed between said impeller and said pump bowl structure; and a skirt formed on the periphery of said impeller and rotating adjacent said cylindrical wall in a manner to form asec'ondaryclearance space therebetween communicating with said auxiliary chamber and with a discharge passage, said skirt providing an opening therethrough communicating with said auxiliary chamber and said secondary clearance space.

10. A combination as defined in claim 9 in which the mouth of said opening opens on said secondary clearance space at a point near that end of said secondary clearance space which communicates with said dis- 1 end of said secondary clearance space which communicates with said discharge passage.

12. A combination as defined in claim 9 in which said primary clearance space is substantially vertical and in which said secondary clearance space limits the velocity of said fluid in said primary clearance space so that abrasive particles carried by said fluid may settle therefrom before the fluid enters said auxiliary chamber.

13. In a turbine pump, the combination of: walls defining an impeller chamber communicating with an intake and a discharge passage; an impeller rotating in said impeller chamber to pump a fluid containing abrasive particles from said intake passage through said discharge passage, said impeller providing an eye rotating in close proximity to said walls to define an upright clearance space, said fluid moving through said eye and having a velocity adjacent the mouth of said clearance space to carry said abrasive particles upward therewith; and means for setting up an upward flow of said fluid through said clearence space of insuflicient velocity to raise said abrasive particles therewith. V

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 18th day of January, 1929.

ARTHUR R. VVEIS.

Images