US3027845A

US3027845A - Impeller tip pocket

Info

Publication number: US3027845A
Application number: US853191A
Authority: US
Inventors: Frederick C Gilman
Original assignee: Worthington Corp
Current assignee: Worthington Corp
Priority date: 1959-11-16
Filing date: 1959-11-16
Publication date: 1962-04-03
Anticipated expiration: 1979-04-03

Description

April 3, 1962 F. c. GILMAN 3,027,845

IMPELLER TIP POCKET Filed Nov. 16, 1959 2 Sheets-Sheet 1 FREDERICK CLGILMAN INVENTOR. BY

April 3, 1962 F. c. GlLMAN 3, 5

IMPELLER TIP POCKET Filed Nov. 16, 1959 2 Sheets-Sheet 2 FREDERICK C. GILMAN INVENTOR. BY W M F l G 10 W United States Patent Office 3,627,845 Patented Apr. 3, 1962 3,027,845 IMPELLER TIP POCKET Frederick C. Gilman, Pompton Lakes, N.J., assignor to Worthington Corporation, Harrison, N.J., a corporation of Delaware Filed Nov. 16, 1959, Ser. No. 853,191 2 Claims. (Cl. 103-103) This invention relates to centrifugal pumps and compressors, in particular to the impellers used therein. More specifically the invention contemplates the introduction of a deflecting means on the leading surface of the vanes of an impeller adjacent the discharge tip. The introduction of the deflecting means may be accomplished by either the addition of material to or the removal of material from the surface of the vane. Further, the deflection means may be embodied in either geometrically regular or irregular obstacles to smooth flow.

Pumps are generally manufactured to standard capacities. In quoting prices to customers instances arise wherein standard pumps fall slightly below required heads while the next larger standard size would not be economically competitive.

Accordingly, the present invention provides a novel means for increasing the head producing capacity of a pump by adjusting the leading surface of a vane or vanes of an impeller.

Thus, the present invention covers an improved impeller for a centrifugal pump comprising a plurality of vanes forming flow channels therebetween, wherein the leading surface of at least one of said vanes has a deflecting means formed thereon at a predetermined distance in from the peripheral edge of said leading surface, said deflecting means comprising structural irregularity to disengage and deflect the boundary flow from the leading surface.

The principles inherent in the improvement of the head producing capabilities of centrifugal machines by means of the present invention are as follows:

.(1) The tendency of relatively slow moving boundary fluid to pass the discharge tip of vanes from the leading or pressure surface to the trailing or under-pressure surface is reduced by enforced mixing of the boundary fl'llid with relatively fast moving main stream fluid as both are sharply deflected by the deflection means near the vane discharge tip.

(2) The accumulation of dead boundary fluid adjacent the trailing surface of the vanes is suppressed and the leaving stagnation point of the relative flow is moved from the trailing side to the leading side. The action is similar to that of an airfoil with a downward deflected trailing edge flap.

(3) As a consequence of these principles, eddies in advance of the vane increase the effective vanedischarge angle.

The objects and utility of this device will appear more fully from the following description considered in connection with the drawings of a preferred form and a second embodiment of the invention. The invention and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

. FIGURE 1 is an edge view of the impeller in a pump casing.

FIGURE 2 is a side elevation of an impeller partly broken away to show in section two vanes and a flow channel between these two vanes.

FIGURE 3 is a vertical section through one of the vanes of the impeller showing the tip pocket form of the invention therein.

FIGURE 4 is an edge view of FIGURE 3.

FIGURE 5 is a vertical section through one of the vanes of an impeller showing the raised deflector form of the invention therein.

FIGURE 6 is an edge view of FIGURE 5.

FIGURE 7 is a diagramamtic sketch illustrating the vane discharge angle and the tendency for the flow of fluid around the discharge tip.

FIGURE 8 is a diagrammatic sketch illustrating the tendency for the separation of the boundaryflow when the present invention is included in the leading face of the impeller vane.

FIGURE 9 is a diagrammatic sketch illustrating the deflection of the boundary layer from the leading face when the present invention is included in the leading face of the impeller vane.

FIGURE 10 is a diagrammatic sketch illustrating the effective increase in vane discharge angle when the present invention is included in the leading face of the impeller vane.

Referring more particularly to the drawings, there is shown an impeller 11. The impeller is mounted inside the stationary casing 12 on a rotatable shaft by means of the keyway 13 in a conventional manner well known in the art.

The impeller 11 includes a central hub portion 14 forming a sleeve surface 15 adapting the impeller to be snugly mounted on a shaft. The impeller 11 has a back plate or rear shroud 16 formed on one end of the central hub portion 14. A plurality of vanes 17 are connected to the central hub portion 14 and back plate or rear shroud 16. The vanes 17 originate at the central hub portion 14 and extend radially outward along a curvilinear path terminating remote from the central hub portion 14 in line with the periphery of the back plate or shroud 18.

In the illustrated form of the invention an edge of the respective vanes 19 is connected to the "back plate or rear shroud 16. The other edge of the respective vanes 20 supports a front member or shroud 21 disposed concentric to the central hub portion 14 and has an opening 22 therein to form the suction inlet 23 adjacent the central hub ends of the vanes 24.

There are a plurality of radially disposed vanes 17 and between each pair of vanes 17 a flow channel 25 is provided. The flow channel 25 extends outwardly from the central hub portion 14 and is bounded by the front shroud 21, the rear shroud 16 and a pair of vanes 17. Suction inlet 23 leads into the flow channel 25.

Referring specifically to the relationship of the vanes 17 and the flow channels 25, each vane 17 has a leading face 26 that is a face on which the higher pressure develops, and a trailing face 27 that is the face on which a lower pressure is acting. I

In the preferred embodiment of this invention as shown in FIGURES 1, 2, 3 and 4, one vane 28 has a pocket 29 formed in its leading surface 26. The pocket 29 is'located in the vicinity of the discharge tip 30 of that vane 28. The downstream boundary of the pocket 31 is parallel to the axis of rotation of the shaft. The downstream boundary of the pocket 31 is located a predetermined distance from discharge tip 30 of that vane 28.

Another embodiment of the present invention is shown in FIGURES 5 and 6, wherein a raised ridge 32 deflecting means is superimposed onto leading face 26. The deflecting surface 31 is formed on the raised ridge 32.

Operation In operation the impeller 11 rotates in a stationary casing 12. Fluid enters the casing by means of an axial entrance means into the suction inlet 23, the fluid is rotated by vanes 17 and the fluid is discharged through suitable outlet means 34 provided in the periphery of the casing 12. These parts, their interrelationship and their use, are

readily recognizable by those skilled in the art and do not differ from other centrifugal machines.

The boundary flow in conventional centrifugal machines finds its way over the discharge tip or downstream trailing edge of the vane 28 from the leading face 26 to the trailing face 27. The tendency of usual boundary flow is shown in FIGURE 7. As can be seen by reference to FIGURE 8 separation of the boundary flow from the leading face 26 is triggered by the deflecting surface 31 and thereby turbulence 36 is developed. The induced turbulence 36 impedes the smooth flow of the boundary layer over the discharge tip 3ft, thereby improving the head producing capability of the centrifugal machine in which the impeller is employed.

As is shown in FIGURE 9, the present invention introduces a forward deflection of the boundary flow at 31 from the leading surface 26 of the vane 28.

In a plane normal to the axis of rotation of the impeller 11 in FIGURE 7, the discharge vane angle D of an impeller is the opening between a first line 37 and a second line 38. The first line 37 is tangent to the circle describing the path of the discharge tip as the impeller rotates. The second line 33 is tangent to the final effective discharge surface of the leading face 26 of the impeller vane 28 as the fluid leaves past the discharge tip 30. The pressure transmitted to a fluid by a centrifugal machine varies according to the discharge vane angle D. As the discharge vane angle D increases the pressure transmitted to the fluid increases. Without the inclusion of the present invention as is seen from FIGURE 7 the zone of active fluid flow approximates the leading face 26 of the vane 28. With the present invention included, the flow of the boundary layer over the surface irregularity 31 combined with the deflecting action of the surface 31 results in eddying. The zone of eddying 39 is shown in FIGURE 10. Effective flow in the zone of eddying 39 is substantially reduced. With the fluid eddies acting in advance of the outside of the leading face 26 of the vane 28 in a fluid sense the outside of the pushing face becomes extended. The leading face 26 of the vane 28 has a new different more blunt effective shape with a higher effective discharge vane angle D'. Therefore the effective tangential component of thnust of the leading surface is increased yielding a higher discharge pressure of the centrifugal machine of which the impeller is a part.

There can be provided any desired or suitable number of vanes 17 and the vanes 17, rear shroud 16, front shroud 21, and central hub portion 14 of the impeller may be proportioned and designed for the particular use for which the centrifugal impeller is intended without departing from the spirit of this invention. A deflecting means might be provided in more than one or in all of the vanes of the centrifugal machine without significantly departing from the present invention. The range of shapes of boundary layer stream impediments provided in the leading face or in the peripheral surface that will accomplish the desired boundary layer separation and deflection are almost limitless. The geometric form of these irregularities need not be regular. Random obstacles to smooth boundary flow will accomplish an analogous result. Although a removal of material from the impeller is the preferred embodiment, FIGURES 6 and 7 show the same invention by means of the addition of material to the leading surface 27 of the vane 28 forming deflecting surface 31 thereon. In the operation of this alternate embodiment the deflecting surface 31 performs all of the functions which deflecting surface 31 performs in the preferred embodiment. All of these modifications of the means on the leading face of a vane of an impeller to separate and deflect the boundary flow from that leading surface are contemplated by the present invention.

What is claimed is:

l. A centrifugal pump comprising:

(a) a casing having a volute,

(b) a centrally disposed fluid inlet in said casing,

(c) a discharge means communicating with said volute,

(d) a rotatable shaft disposed in said casing,

(e) an impeller mounted on said shaft,

(1) said impeller including:

(1) a back shroud,

(2) a front shroud having a central suction inlet,

(3) a central hub connected to said back shroud and fixedly mounted on said shaft,

(g) a plurality of vanes connected to said central hub and spaced in equidistant relationship with each other about said central hub,

(11) each of said vanes being connected with said back shroud and said front shroud.

(1') each of said vanes projecting from said central hub radially with a backwardly directed ourve relative the direction of rotation of said impeller,

( j) each of said vanes having a leading convex surface and a trailing concave surface,

(k) a plurality of flow channels formed in said impeller extending from the inlet of said front shroud to the periphery of said front shroud and said back shroud,

(I) each of said flow channels bounded by said front shroud, said back shroud, said convex surface of one of said vanes and said concave surface of said vane immediately preceding said first mentioned vane,

(m) each of said convex leading surfaces having a downstream trailing edge extending between said back shroud and said front shroud to form a smooth peripheral surface therebetween,

(n) each of said vanes having a planar cut therein on the convex surface thereof,

(0) said planar cut star-ting at a point on said vane at least of the total distance of said vane from said central hub,

(p) said planar cut to extend towards the periphery of said impeller and to terminate short of reaching the downstream trailing edge,

(q) a planar deflecting surface formed substantially normal to said planar cut at the termination point thereof,

(r) said deflecting surface adjacent the downstream trailing edge and parallel with the axis of said shaft,

(s) said deflecting surface, said planar cut, said back shroud and said front shroud defining a pocket,

(t) the pocket starting from the starting point of said planar cut and extending to the termination point of said planar cut at said deflecting surface whereby the boundary fluid flowing along the convex surface of each of said vanes towards the downstream trailing edge of said convex surface will enter the pocket and be deflected by said deflecting surface thus introducing turbulence in the fluid flowing in said casing in the vicinity of the downstream trailing edge.

2. A centrifugal pump comprising:

(a) a casing having a volute,

(b) a centrally disposed fluid inlet in said casing,

(c) a discharge means communicating with said volute,

(d) a rotatable shaft disposed in said casing,

(e) an impeller mounted on said shaft,

(1) said impeller including:

(1) a back shroud,

(2) a front shroud having a central suction inlet,

(h) each of said vanes being connected with said back shroud and said front shroud,

(i) each of said vanes projecting from said central hub radially with a backwardly directed curve relative the direction of rotation of said impeller,

(j) each of said vanes having a leading convex surface and a trailing concave surface,

(I) each of said flow channel-s bounded by said front shroud, said back shroud, said convex surface of one of said vanes and said concave surface of said vane immediately preceding said first mentioned vane,

(n) each of said convex surfaces having a raised ridge formed thereon in integral relationship with the downstream trailing edge,

() said raised ridge projecting upwardly between said front shroud and said back shroud to form a smooth peripheral surfaces therebetween,

(p) said raised ridge extending the peripheral length of the downstream trailing edge in the direction of said central hub,

(q) a planar deflecting surface formed on said ridge at the end thereof closest to said central hub,

(r) said deflecting surface substantially normal to said convex surface and extending from said front shroud to said back shroud in parallel relationship with the axis of said shaft,

(s) said deflecting surface, said convex surface, said back shroud and said front shroud defining a pocket,

(t) the pocket extending along the convex surface from said deflecting surface towards said central hub whereby the boundary fluid flowing along said convex surface away from said central hub will enter the pocket and be deflected by said deflecting surface thus introducing turbulence in the fluid flowing in said casing in the vicinity of the downstream trailing edge.

References Cited in the file of this patent UNITED STATES PATENTS 1,071,660 Banner Aug. 26, 1913 1,688,345 Mursch et a1. Oct. 23, 1928 1,806,494 OBrien May 19, 1931 1,948,949 Stockton Feb. 27, 1934 2,574,948 Alikonis Nov. 13, 1951 2,636,479 Srnyser Apr. 28, 1953 2,737,898 Ander-matt et a1 Mar. 13, 1956 FOREIGN PATENTS 636,848 Great Britain May 10, 1950 653,161 Great Britain May 9, 1951 691,098 Germany May 16, 1940