US2641191A - Guide means on impeller for centrifugal pumps or blowers - Google Patents

Description

4 Sheets-Sheet 1 June 9, 1953 A BUCHI GUIDE MEANS on IMPELLER FOR CENTRIFUGAL PUMPS OR BLOWERS Filed Nov. 18, 1947 A. BUCHI 2,641,191

GUIDE MEANS 0N IMPELLER FOR CENTRIFUGAL PUMPS 0R BLOWERS June 9, 1953 4 SheeEs-Sheet 2 Filed Nov. 18, 1947 A. BUCHI June 9, 1953 GUIDE MEANS 0N IMPELLER FOR CENTRIFUGAL PUMPS OR BLOWERS 4 Sheets-Sheet 3 Filed Nov. 18, 1947 A. BUCHI June 9, 1953 GUIDE MEANS ON IMPELLER FOR CENTRIFUGAL PUMPS 0R BLOWERS Filed NOV. 18, 1947 4 Sheets-Sheet 4 Patented June 9, 1953 OFFICE GUIDE MEANS ON IMPELLEB FOR GEN: TRIFUGAL PUMPS OR BLOWER/S- Alfred Buchi, Winterthur, Switzerland Application November 18, 1947, Serial N 0. 7 86,605

In Switzerland November 12, 1946 5 Claims. 1

The invention relates to a special embodiment of the inlet device on impellers for single-stage or multi-stage centrifugal pumps or blowers. According to this invention, at least one funnelshaped annular vane is arranged into the intake throat of the impeller which guides the pressure medium from the axial to the radial direction, so that said annular vane, together with the confining surfaces of the intake throat, guides the pressure medium from the axial to the radial flow direction. The object of the invention may be so chosen and dimensioned that the funnel-shaped annular vane or vanes are fastened in the static section of the inlet casing, surrounding the impeller inlet, and the actual impeller blading starts only beyond the approximately radial exit of the annular vane or vanes. However, the annular vane or vanes may also be built into the centrifugally-acting impeller blading proper, extending inwardly towards the inlet throat for the pressure medium. Aside from the annular vane or vanes, additional vanes may be built into the entrance section of the impeller, e. g. vanes which impart a radial flow direction to the entering pressure medium, ahead of the centrifugally-acting impeller blades. If the embodiment is such that the annular vanes are to rotate with the impeller and the additional vanes are fixed in the static casing, then the additional vanes have to be slotted. The object of the invention can also be so arranged that in case of impellers with impeller blade tips extended axially towards the entrance throat for the pressure medium, the annular vane or vanes are built at least into the impeller section which guides the pressure medium from axial to radial direction. The annular vanes may extend, in this case, up to the inner ends of the impeller blades, or they may be shorter be so formed that the radii of curvature Of the passages created between the impeller walls and the annular vane or vanes, vary from the inlet in the direction of the pressur medium flow, i, e. they decrease or increase.

The impeller walls, as well as the built-in annular vane or vanes, may on one hand be so dimensioned and shaped that the Velocity of the pressure medium increases from the entrance towards the radial section of the impeller, and that on the other hand, in the same section, the radii of curvature of the passages which are created between the Walls of the impeller and the annular vane or vanes, vary in the direction of the pressure medium flow, so, that despite the necessary curvature of said passages into radial direction there will be no substantial flow detachment of the pressure medium from the walls.

The annular vane or vanes may be divided (i. e. made in several parts) in at least one plane thrOugh the blower axis. The static annular vane or vanes may be cast Or welded into the static entrance section of the pump or blower. The rotating type of annular vane 01' vanes may also be cast or welded into the impeller blading.

Furthermore, the arrangement with axially protruding impeller blade ends and with annular vane or vanes extending into the impeller blading, may also be made so that the thus formed passages for the pressure medium in the impeller have approximately square cross section, to keep the losses in these passages to a minimum. A sufficient number of annular vanes may be built in, that the thus determined radii of curvature of the passages between the confining walls of the impeller and the walls of the built-in funnelshaped annular vanes are at least greater than the width of the corresponding, curved passages for the pressure medium.

The annular vanes may, however, also be made curved and built-in so that the radii of curvature, in relation to the width of the passages for the pressure medium created between the impeller walls and the annular vanes, ar approximately equal for all pafisages.

At least two annular vanes may be built into the intake means of the impeller. In this way the passages confined between the impeller walls and the annular vanes can be made to have relatively large radii of curvature-e. g. of twice or more times the passage Width--whereby the flow deflection losses are reduced. In these cases the arrangement is made preferably so that the ratio of radius of curvature to width of passage is approximately equal for all passages. The number of the impeller blade ends and of the annular vanes may be chosen s0-for the sake of reduction of losses-that the thus created passages have approximately square cross section.

The intake means may also contain a sufficient number of annular vanes so formed and dimensioned that in all the inlet ducts thus created the sum total of all losses through friction, flow defiection and energy transition in the various separate entrance passages up to the proper centrifugally-acting impeller blading will be about equal and/or will be a minimum.

In case of multi-stage centrifugal pumps or blowers, whereby the pressure medium is guided from one impeller to the next impeller by means of fixed, inwardly-leading guide ducts in radial and then axial direction, at least one annular vane deflecting the pressure medium by approximately 180 degrees may be built in. In case of such centrifugal pumps or blowers, whereby impellers receive their pressure medium direct from a prior stage, there may be arranged at least one annular vane each, providing approximately 90 degrees flow deflection, in the fixed, curved intake passage, and/or in the corresponding impeller intake passage.

There may also be arranged a sufficient number of annular vanes in at least one of the two guideand impeller-sections equipped with such annular vanes, and the vanes be so shaped and located, that the velocity and pressure conditions over the whole admission area for the pressure medium leading to the centrifugally-acting impeller blading will be at least approximately equal. In case of centrifugal pumps or blowers with divided (two-piece) guide casings, the built-in annular vanes may also be of divided construction.

In case of multi-stage centrifugal pumps or blowers, too, the built-in annular vanes may be arranged on constructed in such numbers, shapes and with such radii of curvature that there will be minimum flow losses in the thus created guide passages and/or all losses in these guide passages being about equal.

Special impellers with axially-acting blading may be arranged ahead of the centrifugally-acting impellers, whereby the former guide the pressure medium to the latter with a minimum of shock losses. Also, at least one axially-acting impeller may be arranged ahead of the centrifugally-acting impeller so that it transmits the pressure medium to the latter via a guide wheel. In this case, too, the inlet section of the blading of the centrifugally-acting impeller is to be shaped accordingly.

The object of the invention is illustrated in the enclosed figures in several examples of centrifugal blowers. Same numbers or letters mean same or similar parts. The application of the invention on centrifugal pumps can easily be deducted therefrom, since those machines contain similar parts.

Figs. 1 and 2 show sections through singlestage centrifugal. blowers wherein the invention is embodied in the simplest form.

Fig. 3 illustrates a section through a shrouded impeller of a single-stage blower, whereby the object of the invention is applied in a different form on an impeller with backward-curved vanes.

4 the invention on an impeller similar to the one shown in Figs. 5 and 6, except that here the inner inlet section of the impeller is made in a piece separate from the impeller proper.

Fig. 9 illustrates a section through a still further embodiment of the invention, and

Fig, 10 is an axial view of the corresponding inlet device after it is removed outside of the impeller, viewed in a direction opposite to the pressure medium flow.

Figs. 11 and 12 show possible forms and arrangements of annular vanes built into the inlet opening of the impeller; Fig. 11 shows an open impeller with vanes extended as far as the inlet opening of the impeller, and Fig. 12 shows a shrouded impeller.

Figs. 13 and 14 show vertical sections through the axis of multi-stage centrifugal blowers. In Fig. 13 the casing of this blower is divided lengthwise (in axial direction) into two parts. Fig. 14 shows a multi-stage blower where the casing parts and the impellers are designed to be assembled axially and successively, so that the casing joints are vertical.

In Fig. 1, I is the impeller of the centrifugal blower, keyed upon shaft 2. The impeller I has centrifugal vanes 3 and a shroud 4. The twopiece blower casing 5 and 6 encloses the impeller I and has a joint 1. The pressure medium enters the casing at 8 and is led into the blower casing 9; from there it is fed through pressure tube III to its destination.

The object of the invention is the annular vane l I, which juts into the inlet section I2 of the impeller I and aids the flow deflection of the pressure medium in thi section from the predominantly axial direction to the at least approximately radial direction of the centrifugal impeller vanes 3. In the illustrated example, the onepiece annular vane II is cast into the ribs I3 of the blower casing which connect the fixed central section I4 with the blower volute 9. The inner diameter I5 of the annular vane II is just large enough to avoid touching the inner edges I8 of the impeller vanes 3 by said annular vane I I, and to permit detachment of easing part 5, with the thereto-attached annular vane II, from casing part 6 without blocking by the inlet edge I I of the impeller shroud 4. In the shown example the annular vane I I is arranged relatively closely to impeller shroud 4.

In Fig. 2 the impeller I has vanes 3 but no shroud, so that casing part 5 laterally encloses the vanes 3 with small clearance. The impeller vanes 3 are extended axially towards the inlet of the impeller and terminate in the approximately radially-arranged inlet edges [8. An annular vane II is so arranged that it is set back some distance from the impeller vane inlet edges I6, and that it provides the flow deflection of the pressure medium from axial to radial direction.

This annular vane II may be cast into impeller blades 3, or fixed therein in some other manner. It is arranged, as seen from the figure, more closely towards the outer side of the impeller vanes. This is done to avoid serious discrepancies in the ratios between radius of curvature and passage width, and the consequent discrepancies in losses.

InFig. 3, I is the impeller with shroud 4 and impeller vanes 3. The latter terminate inwardly at the edges I6. In this example, two annular vanes I I and II are built-in; their outer ends are cast into the impeller vanes 3. The inner ends of the annular vanes, i. e. the ones towards the inlet opening'oi the impeller, jut freely into said inlet opening.

As is visible from Fig. l, an embodiment according to Fig. 3 has backward-curved impeller vanes 35. The annular vanes II and II are so located that three annular passages It, I8 and I8" are created between the confining walls of the impeller and the two annular vanes. These annular passages have different widths, so that passage it is narrowest, and passage I8" is wid st. Thus, the mean radii of curvature of the three passages can be made to have approximately eoual ratio to the widths of the corresponding ducts. With a given angle of deflection,

the deflection losses in the three annular passages can therefore be kept about equal, so that ap proximately equal pressure and velocity conditions will prevail over the whole cross section at the exit of said annular passages towards the con trifugally-acting section of the impeller.

Figs. 5 and 6 show an open centrifugal blower im eller I in which the impeller blades 3 are radially arranged on their centrifugal part, and axially so extended at 3 and bent around at their inlet edges Iii that they admit the axially-inrusl1- ing pressure medium approximately shock-free. Two annular van s II and. II are also arranged here in the impeller blading section towards the pressure medium entrance. They may be cast-in or weldeddn, for example.

The inner part of the impeller hlading with the ax ally extended inlet edges l5 and with the annular vanes II and i! may, on the other hand, also be bui t as a part containing the inner passa es it and It". The outer of vanes may be held in a ring 2 Such a vane part is illustrated a section in '7 and in axial view in 8. In this case the inner part of the im peller is separated from the centrifugal impeller proper. This piece may be fastened at the hub section of impeller I, e. g. by means of ring it. It is built in at 3" inside of th outwardly-located impeller vanes 3. Between the ring 29 and easing part 5, seals 2i may be arranged. By these means,

both the pressure medium delivery and the blower efilciency are improved in comparison to the ones on previously-known constructions where no such cover ring nor seals are used. Ring 2b may be seated, as shown on Fig. 7, directly upon the vanes 3 of an open impeller, or it may be fastened there. The vanes 55" abutting against impeller disc I may also have axially-directed protrusions 26 which may reach e. g. into the impeller disc I, or they may he riveted or welded, etc. thereon.

The inset blading section may also be so shaped that it reaches up to the inclined edges 3a" of the impeller vanes 3.

In Figs. 9 and 10, an embodiment similar to the one in Fig. l is shown. The annular vane II is also here fastened in the ribs I3 of the blower casing 3. Aside from the annular vane -I I, however, eight thin, radial vanes 22 are also fastened in the ribs I3. These annular vanes, together with the eight radial vanes 22 and with the confining walls of impeller I and shroud enclose sixteen radially-curved guide passages for the pressure mg 3 can be maintained. The ribs 22, aswell as the annular vane II may be cast, welded, or soldered, etc, into the ribs I3;

Figs. 11 and 12 illustrate, on two construction examples, the variety of shapes that can be given to the annular vanes and impeller walls at their inlet ends. Fig. 11 shows an open impeller I. It is equipped with vanes 3 which extend axially up to edge I6. 5 is the casing part which encloses or covers the impeller 'blading on the outside. The annular vanes I I and I I, located in the inlet section of the impeller blading, show sharper curvature at the inlet ends, and reduced curvature towards the radial part of the impeller. Furthermore, the widths of the ducts created between the confining walls of the impeller and the annular vanes II and l I are larger at the pressure medium intake b1, b2, in than at the exit -b1, bz, b':;. The annular vanes II and I I are unevenly placed so that the ratio of the mean radii of curvature r1, r2, 1'3 of the passages to the mean passage widths b1, b2, be is at least approximately larger than unity at the entrance, and increases to still higher values toward the exit bi, b'a and 13's. By this means, the deflection losses in the three passages I8, I8 and I8 are kept relatively small. It is even possible, according to this invention, to locate the annular vanes I I and I I so, and pro vide them with such curvatures and such length that the velocity and pressure losses will be equal in all the three passages I8, I 8" and Ill". The pressure medium enters therefore the centrifugally-acting blade section 3 of the impeller I with even velocities and under even pressure. This, of course, results in optimum admission of the pressure medium and, consequently, optimum effect of the impeller blading and of the whole machine. The annular vanes 'I I and I I may be of diiierent length on their intake or on their exit, as visible in Fig. 11.

In contrast to an embodiment shown in Fig. 11, Fig. 12 shows annular vanes so shaped that at the inlet ends they have relatively large, though uneven, radii of curvature 11,12, 'rs compared to the passage widths b1, b2, b3, and have relatively small radii of curvature r'i, 7"2, 7"3, compared with the passage widths b'i, bz, b'3 at the exit ends. The passage widths b1, b2, b3 and bi, bz, b's, respectively, are chosen uneven, too. They are largerat the pressure medium inlet than at its exit, so that an accelerated flow through the passages is achieved. The inner ends I51 and IP52 of the annular vanes II and i I are so dimensioned that they do not touch the impeller'vanes 3 and I 6, but still provide most complete flow deflection to radial direction. With the type of annular vanes shown in Fig. 12, aS-COlltI'fiStEd to an embodiment according to Fig. 11, the ratio of radius'of curvature to passage width is large at the pressure medium intake, and smaller at the rear end'of the annular vanes II and II. I

Through the insertion of these annular vanes, the ratio of radius of curvature to width of the guide passages can be made much larger than in case of no such annular vanes. Thus the losses through flow deflection of the pressure medium from axial to radial direction can be greatly reduced. By proper choice of the radii of curvature of the annular vanes and of the confining walls oi the impeller at the pressure medium in take, and by suitable shaping, length and location of the annular vanes, the intake flow losses to "the impeller can be reduced to a minimum, and/or the intake velocities to the centrifugal impeller blading, measured over the whole intake cross section, can be made equal, at equal'pressure.

This permits more perfect filling of the impeller blading proper than would be possible without built-in annular vanes, resulting in greater output and higher efliciency of such centrifugal impellers.

Fig. 13 shows a section through the axis of a multi-stage centrifugal blower. It contains three impellers lb, lb, and lb arranged in series; The pressure medium enters at A and is discharged at B. All the three impellers lb, lb, and lb are keyed upon shaft 2, which is driven through coupling flange 2. The casing 9', 9" which encloses all the impellers, is divided into two sections at the horizontal plane 9". The object of the invention is incorporated in impeller la in similar manner as in the embodiment shown in Fig. 3. Two annular vanes a and I I'll are built into the impeller vanes 3b. They terminate at His about parallel to the blower axis, however. The annular vanes l lb and l 8. jut a little beyond the inlet edge of impeller la.

The impellers In, and lb discharge the pressure medium first to one guide device each, 23 and 24, where velocity is converted to pressure. Then the pressure medium is led through receivers 25 and 26, respectively, to the passages 27 and 28 which guide it radially inward again. The latter are equipped with vanes 30a and 39b which impose a predominantly radial flow direction to the pressure medium, particularly near the blower shaft. The pressure medium is led axially towards the inlet of the adjacent impeller lb or '0, respectively, by means of the casin walls which are curved, near the axis, from radial to axial direction. The flow deflection from space 21 into the impeller interior lb, which amounts to nearly 180 angular degrees, can be aided greatly by an embodiment of this invention. As seen in Fig. 13, it consists in at least one annular vane each (21', 21 and 28', respectively) built into the exits of the transmitting pieces 21 and 28. They guide, together with the rounded confinin walls of the guide parts 21 and 28, respectively, the pressure medium to the inlet of the adjacent impellers lb and '0, respectively, with a possible minimum of losses through deflection, friction, etc. Additional annular vanes llb, llb and c of a type hereinabove described are built into the impeller inlets. The annular vanes 21', 21" and 28, respectively, are preferably so shaped and arranged in relation to the annular vanes l l, l lb and l '0 in the impellers lb and Is, that the full deflection of the pressure medium from radially-inward direction via axial to radially-outward direction is accomplished with minimum velocity and pressure losses, and/or with even velocity and pressure distribution of the pressure medium over the whole inlet cross section of the centrifugally-acting impeller blading.

Fig. 14 illustrates also a section through a threestage blower with impellers lb, lb, lb. The blower casing consists here of four disc-shaped parts 9'1, 9'2, 9'3 and 9'4 which may be separated from each other along radially-extended joints 291, 292 and 293 upon loosening of the corresponding flange connections. Assembly of the blower is accomplished by first mounting the blower part 9'4 on the shaft 2 from the left-hand side, then sliding the balancing piston 39 on the shaft from the right-hand side, followed by impeller lo, and then fastening the blower casing part 9'3 on casing part 9'4. Thereupon the impeller lb, casing part 9'2, impeller lb, and, last, the inlet casing part 9'1 are assembled in that order.

According to the invention, deflecting vanes I la and l l 'a are built into the inlet section of the blading 3b of impeller lb. The annular vanes II- and llb are built into impeller la. similarly as illustrated already in Fig. 3.

Annular vanes l lb and l l'b are arranged in the intake section of impeller lb, and an annular vane c is installed in the inlet of impeller '0. Installation of the annular vanes l lb and llb and I '0, respectively, is done by insertion or by casting-in into vanes 30b and 30b, respectively, which subdivide the guide passages 21 and 28. These annular vanes are thus rigidly connected to the casing parts 9'2 and 9'3, and extend into the inlet sections of the impellers lb and l c, close to the inner impeller blade edges lBb and Ne. The outer diameters l5b, l5'b and We of the annular vanes llb, llb and He, respectively, are chosen just large enough that the casing parts 9'2 and 9'3 can be readily withdrawn axially from the impeller inlet openings.

Similar as on the other shown embodiments, the shape, radii of curvature, and position of the annular vanes can be so chosen that minimum velocity and pressure losses will occur in the deflecting passages between the guide passage sections 21 and 28, respectively, and the impeller'inlet lb and '0, respectively. The annular vanes may also be arranged in such numbers, shapes, and positions, that the inlet conditions will be approximately equal over the whole inlet cross sections of impeller blades 3b and 3c.

The invention provides improved inlet conditions on centrifugally-acting impellers. There, the pressure medium has to be deflected by about degrees from axial to radial direction in case of single-stage blowers or pumps or on the first stages of multi-stage blowers or pumps. The deflection amounts to nearly degrees in case of the subsequent stages of multi-stage blowers or pumps. This sharp deflection causes losses through deflection, friction, andif the passage areas are variable-also throughv energy transition. These losses, or their sum total, are to be reduced by the insertion of the proposed annular vanes. The latter may be so shaped and located that throughout the whole inlet section for the pressure medium to the centrifugallyacting impeller blades there will prevail approximately equal velocity and pressure conditions. Since the deflection losses, in particular, take up a relatively large share of the total losses, it follows that the number and design of the annular vanes should be so chosen that the ratio of curvature radius to width of passage, for the passages so formed, will be as large as possible. This ratio is to be chosen differently for the individual guide passages so that the sum total of all losses therein is equal and/or is a minimum.

I claim:

A centrifugal p mp or blower having an axial inlet eye and a blade supporting wheel, impeller blading on said wheel, a casing about said wheel and said blading, said casing having an annular portion defining the outer perimeter of said eye, said wheel having a portion beginning near the center of said eye, extending axially inwardly and curving from axial to radial direction to define with the inner portion of said casing a curved annular passage subdivided by said blading whereby the fluid to be pumped or blown is admitted axially through said eye and is forced centrifugally radially outwardly of said blower wheel, and funnel shaped annular vane means disposed in said passage beginning at least within said eye and curving with the blower wheel portion and inner portion of said casing defining said passage to subdivide said passage into a plurality of smaller annular passages, said vane means being of such progressive diameters that the resulting ratios of the mean radii of curvature to the mean widths of said last mentioned subdivisions, measured in axial planes, are approximately equal for all said passages.

2. The pump or blower as defined in claim 1 wherein the blading on the blower wheel begins within the radially outer area of said annular passage and extends outwardly therefrom in a direction having a substantial radial component, and the annular vane means extends into said passage only up to the beginning of said blading and said vane means is secured to the blower casing so as to prevent rotation thereof with the blower wheel.

3. The pump or blower as defined in claim 2 wherein there is additionally provided a series of axially extending inlet blades, said blades being fixed to the blower casing and extending from a point outside the inlet eye into said passage u to the beginning of the wheel blading.

4. The pump or blower as defined in claim 1 wherein the blading extends into the inlet eye and the vane means are secured to said blading so as to rotate therewith.

5. The pump or blower as defined in claim 1 wherein the annular vane means are secured to said blading so as to rotate therewith.

ALFRED BUCHI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 447,909 Schoonover Mar. 10, 1891 879,476 Krell Feb. 18, 1908 905,712 Krell Dec. 1, 1908 1,159,094 Rice Nov. 2, 1915 1,159,095 Rice Nov. 2, 1915 1,345,638 Schmidt July 6, 1920 1,728,204 Falla Sept. 1'7, 1929 1,896,749 Lafioon Feb. 7, 1933 2,135,053 Rockwell Nov. 1, 1938 2,305,136 Campbell Dec. 15, 1942 2,401,206 Van Rijswijk May 28, 1946 2,404,609 Whittle July 23, 1946 2,405,284 Birmann Aug. 6, 1946 2,419,669 Birmann Apr. 29, 1947 2,438,426 Whittle Mar. 23, 1948 FOREIGN PATENTS Number Country Date 27,163 Netherlands July 15, 1932 226,523 Switzerland July 16, 1943 448,676 Germany Aug. 25, 1927 546,085 Germany Mar. 14, 1932

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