US2748713A

US2748713A - Multi-stage centrifugal pump or blower

Info

Publication number: US2748713A
Application number: US342830A
Authority: US
Inventors: Buchi Alfred
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-03-21
Filing date: 1953-03-17
Publication date: 1956-06-05
Anticipated expiration: 1973-06-05

Description

June 5, 1956 A. BUCHI MULTI-STAGE CENTRIFUGAL PUMP OR BLOWER 3 Sheets-Sheet 1 Filed March 17, 1953 Inventor- ALFRED BUCHI June 5, 1956 A. BUCHI MULTI-STAGE CENTRIFUGAL PUMP OR BLOWER 3 Sheets-Sheet 2 Filed March 17, 1953 Inventor.- ALFRED BUCHI United States Patent MULTI-STAGE CENTRIFUGAL PUMP 0R BLOWER Alfred Buchi, Winterthur, Switzerland Application March 17, 1953, Serial No. 342,830

Claims priority, application Switzerland March 21, 1952 13 Claims. (Cl. 103-108) The present invention relates to multi-stage con'trifugal pumps or blowers and relates to the particular construction of one or more guide device parts arranged in the direction of the flow of the pressure medium to at least one rotor wheel and surrounding this at least partially, and of the reversing passages connected thereto. These parts direct the pressure medium from one rotor wheel to the next.

The main object of the particular construction of such a guide device resides in so simplifying the production of the casing parts which contain the reversing passages and to render them so accessible that an accurate finishing operation and also cleaning of the reversing passages is rendered possible and facilitated. Further, by this construction the production of the casing parts can be carried out by casting, pressing and the like in an advantageous manner and with considerable accuracy.

The construction of a multi-stage centrifugal pump or blower according to the invention consists in that at least the stationary guide device parts of the separate stages of a multi-stage centrifugal pump or of a blower, surrounding the rotor wheels and conducting the pressure medium to the succeeding rotor wheels, are constructed as parts separated in planes normal to the axis of the pump and reversing passages conducting the pressure medium from one stage to the next are constructed as passages open in an axial direction, which in the assembled pump are covered by separate annularcover plates.

In a preferred form of construction of the annular cover plates these are provided internally with a bore, of which the wall coincides with the outer limit of the next rotor wheel opening. The construction may be such that at least one cover part projects with an annular projection on the outer side into an annular offset and is so constructed and connected to guide device parts that on the outside there is formed with the projection a centring fitting and packing connection and 'on the inside, with projection of the cover plate, a packing relatively to the next succeeding rotor wheel on its inlet side. The guide device parts, which can be separated from one another, of the separate stages may advantageously be held together in a cylindrical casing envelope. In order to keep frictional losses in the reversing passages as small as possible, special precautions are taken; these passages may, for example, have a continuously curved shape in the directionvof diffuser passages in the guide device parts arranged directly in front thereof. For further reducing losses, the reversing passages may be so curved in a progressive and continuous manner, but differently at their inlet portions from the direction from the diffuser passages at their inner portion in a direction towards the next rotor wheel, that both the widths of the reversing passages transversely to the direction of flow and their radii of curvature, vary in such a manner that the ratio of radius of curvature to 2 width of the reversing passages is as large as possible and is never less than 1.5 1.

The through-flow cross-sectional areas of the reversing passages may be further divided, in at least one of their curved parts, transversely to the direction of flow of the pressure medium by guide blades extending in an axial direction. The method of construction may be such that against at least one outer part, containing the reversing passages, bears an internally and externally circular inner part arranged co-axially to the pump axis and closes its cover part, this part is a guide passage body forming the continuation of the reversing passage to the inlet port in the next rotor wheel and is fitted with rotor blades. The construction of the reversing passages may be such that these form, with their adjacent limiting walls extending in axial direction, an acute angle towards the interior. The points at which these limiting walls meet to form the said angle may be contiguous with the guide blades which conduct the pressure medium into the inlet port of the next rotor wheel. The point may, however, be also located opposite the inlet port to the next rotor wheel. The through-flow cross-sectional areas of the reversing passages at the parts thereof curved in the direction of flow may be so sub-divided radially by axially extending annular guide blades, that the spacing of these guide blades transversely to the direction of flow amongst themselves and relatively to the limiting walls is determined by a predetermined constant ratio of the average radii of curvature of the subdivided separated reversing guide passages to the width thereof.

Several examples of construction of the subject of the invention are illustrated in the accompanying drawings wherein:

Fig. l is a longitudinal section of a first form of construction of the invention through the axis of a multistage centrifugal blower on the line 1-1 of Fig. 2.

Fig. 2 is a cross section on the line II-II of Fig. 1.

Fig. 3 is a cross section on the line III-III of Fig. 1.

Fig. 4- is a longitudinal section of a second form of construction through the axis of a multi-stage centrifugal blower on the line IV-IV of Fig. 5.

Fig. 5 is a cross section on the line V-V of Fig. 4.

In Fig. i, 1 indicates the rotor wheels of a 5-stage blower. These may be of any construction. 2 is the common driving shaft to which the rotor wheels are keyed. 3 is a distance piece arranged between two rotor wheels. 4 and 5 are the stationary guide device parts surrounding the rotor wheel of at least one stage and containing the guide passages for the pressure medium. These blower parts are mounted in a casing cylinder 7 with flanges 7a and 7b. The pressure medium inlet casing i342, 1312 and pressure medium outlet casing 14 are so bolted to the flanges 70. and 7b that the guide device parts of each stage and the stages are pressed together. Each stage with the exception of the end stage is provided with reversing passages 8, which conduct the pressure medium of one stage to the rotor wheel of the succeeding stage.

The

guide device parts

4 and 5, according to the invention, are constructed as parts separated in a plane normal to the axis of the pump, Whilst the reversing passages are completely open towards one side in the axial direction. Annular cover plates 10 are provided for the reversing passages 8. The inner bore of the plate 10 is indicated at 11. The outlet edge of the bore 11 coincides with the outer limit of the rotor wheel inlet opening. The cover plate 10 is provided on its outer side in the axial direction with an annular projection 10a. The outer limiting surface of the projection engages with a close and tight connection with the guide device part 5. The projection 10a is provided on the inside towards the rotor Wheel with a labyrinth or similar packing. The outer periphery of the plate 10 engages with an annular groove 4a. This groove is formed by the

guide device parts

4 and 5. The centring of the plate with the axis of the rotor wheel may be effected by means of the groove 41: and the outer peripheral edge of the plate 10, or also by means of the inner axial bore of the guide device part 5 and the projection a of the plate 10. The packing rings are indicated at 20.

The axial bore in the part 4 is provided opposite the distance piece 3 with a labyrinth packing.

According to Fig. 2, as also according to Fig. 5, five guide passages 18 are connected to a gap space 16 and collecting passages 17, by which the pressure medium flowing from the collecting passages 17 is first conducted along straight line diffusers 18' extending tangentially to the rotor wheel and transversely relatively to the blower axis. From the diffusers the conveying medium passes into diltuser passages 18 connected tangentially to 18 and bent in the peripheral direction, which are enlarged at least in the cross-sectional direction and so bent in the axial direction, that they conduct the conveying material directly into the reversing passages 8 located laterally of the rotor wheel. Each reversing passage is provided in the direction of the guide and diffuser associated therewith with a continuously bent shape. The walls 8a and 8b of the reversing passages 8 are not only bent continuously, but these walls, determining the widths of the reversing passages, are provided in the transverse direction to the flow of the pressure medium with continuously changing radii of curvature.

The ratio of these radii of curvature to the width of the reversing passage is made as large as possible at the same points, namely, so large that it is never less than 1.5 :1. As the reversing passages become wider in the direction of flow, the radius of curvature of the walls 8:: decreases in this direction. Guide blades are provided in the direction of flow of the pressure medium, which divide the reversing passages at least in one part of their bent portions transversely to the flow. The adjacent walls 81: and 8b of the reversing passage limting walls following one another in the direction of rotation, which extend in an axial direction, form at 80 (Fig. 2) an acute angle, whereupon the walls 8a and 8b pass into the guide blades 6a.

Fig. 3 shows the construction of the annular space 14a connected to the last stage and provided with the outflow nozzle 14b. The conveying medium is supplied through the inlet member 13b and the annular chamber 13a to the rotor wheel 1 (Fig. 1). The construction of the collecting chamber connected to the last stage is not the subject of the present invention and may, as shown, or instead of being arranged laterally of the passages 18, be arranged, for example, vertically above the same.

According to another form of construction as shown in Fig. 4, the inner part of a reversing passage is located in an axially located inner guide device part 6, and the larger outwardly connected reversing passage part is formed in a casing part 4 open on one side towards the next stage. The open part is covered by an annular plate 10 which extends up to the interior of the guide device part 6. In the interiorly arranged reversing passage parts 8 are provided the guide blades a (see also Fig. 5). The guide part 5 is similarly constructed, as described in connection with Fig. 1, whereas the part 4 is only provided for forming the outer part of the reversing passages 3' and inwardly connected to the part 6 which contains the inner part of the reversing passages. On the outside the part 6 is also provided with a circular surface which forms tight and packing connections with the guide device parts 4', 5 and the annular cover plate 10'. The part 6 contains the continuation of the outer reversing passage up to the inlet opening into the next rotor wheel. It is provided on the side of the next succeeding rotor wheel in axial direction with a similar projection 10b to the inner part of the cover plate 10 shown in Fig. 1. This projection is here indicated by 6b, and its outer annular surface is located relatively to the part 5 in the same manner as the projection 10b.

Annular guide blades 12 are provided in the curved part of the reversing passages before the inflow of the pressure medium into the rotor wheels, said blades 12 extending in the axial direction and dividing these parts of the reversing passages in a radial direction. The spacing of these guide blades relatively to one another and from the limiting walls is determined by a definite constant ratio of the central radii of curvature of the subdivided separate reversing passages to the width thereof. The plate 10' projects in a radial direction outwardly as described in connection with Fig. 1 in respect of plate 10, into an annular groove, formed by the

part

4 and 5. According to Fig. 5 the limiting walls 8a and 8b of each two succeeding reversing passages are guided in the guide device part 6 up to the inlet opening 11a into the rotor wheel of the succeeding stage, where they meet at 8c at an acute angle, and are thus constructed as guide blades 6a. The point indicated at in Fig. 2 corresponds in this case with the point indicated at 8c. This construction of the reversing passages can also be used without difficulty also in the forms of construction shown in Fig. 1.

As shown in Figures 1 and 4, the inner parts of the reversing passagesformed in Fig. l by the cover plate and the thereto opposed wall of part 4-deviate from their radial direction for a relatively short distance into a direction askew to the blower axis, thereby it is possible to provide for a relatively greater radius of the reversing passage portions that connect with the inlet port of the next rotor wheel.

What I claim is:

1. A multi-stage centrifugal pump or blower comprising a common shaft, a plurality of rotors fixed to said shaft, two separate housing parts surrounding each rotor for one pressure stage, one for the front or inlet side of the rotor and the other for the back side of the rotor, the inside surfaces of said two housing parts being set contiguously beside one another along a normal division plane, the inside of both housing parts together forming a stationary guide device having a plurality of separate peripheral guide ducts receiving the pressure medium from the rotor, the discharge end of said guide ducts being deflected axially towards the following higher pressure stage, an equal number of secondary guide ducts on the axially outer side of said back side housing part, each of the secondary guide ducts being in registering connection with said discharge end of the peripheral guide ducts and being curved radially inwardly to thereby reverse the flow of the pressure medium in the peripheral guide ducts and to direct the pressure medium into the rotor inlet of the next following higher stage, said secondary or reversing guide ducts forming open channels in said back side housing part mainly in the direction towards the rotor inlet of the next following higher pressure stage, said channels being defined circumferentially by axially extending division walls, an annular body pressed against the free ends of said division walls, shoulder means on the axially outside surface of the housing part of the next following pressure stage bordering said annular body, the free ends of said division walls lying at least in the radially outer portions of said secondary guide ducts in a plane normal to the rotor axis, said annular body being constructed as an annular substantially fiat plate surrounding the inlet to the rotor of the next following higher pressure stage, and said shoulder means being disposed to substantially border the inner and outer perimeter of said front side housing part of the following pressure stage.

2. A multi-stage centrifugal pump or blower according to claim 1, wherein the said annular body is provided on its inner surface with a bore which registers with the outer boundary of the next rotor inlet port.

3. A multi-stage centrifugal pump or blower according to claim 1, wherein the housing parts forming guide passages are held together in a cylindrical casing envelope.

4. A multi-stage centrifugal pump or blower according to claim 3, wherein said annular body projects on thebutside into an annular recess and is so constructed and connected to the other parts forming guide passages that on the outside a centering and packing connection is formed and the inner side of each annular body is formed as a packing relative to the next succeeding rotor on its inlet side.

5. A multi-stage centrifugal pump or blower according to claim 1, wherein the reversing passages have a continuously curved shape in the direction of the diffused passages in the parts forming guide passages.

6. A multi-stage centrifugal pump or blower according to claim 1, wherein the reversing passages are curved so that their widths transverse to the direction of flow and their radii of curvature vary in such manner that at same points the ratio of the radius of curvature to the width of the reversing passages is as large as possible but is nowhere smaller than 1.5 :1.

7. A multi-stage centrifugal pump or blower according to claim 1, wherein the through-flow cross section of the reversing passages and at least in a part of their curved portions is sub-divided transversely to the direction of flow of the pressure medium by guide blades extending in axial direction.

8. A multi-stage centrifugal pump or blower according to claim 1, wherein the limiting walls of the reversing passages extending in a substantially axial direction and being located side by side form an acute angle toward the inside, and the points at which the limiting walls meet to form the said angle are contiguous with guide blades which conduct the pressure medium into the inlet port of the next rotor.

9. A multi-stage centrifugal pump or blower according to claim 1, wherein the point at which the axially extending limiting walls of the reversing passage run into one another is located substantially opposite the inlet port to the next rotor.

10. A multi-stage centrifugal pump or blower according to claim 1, wherein the through flow cross-section of the reversing passages at least at their curved portions is so sub-divided in the direction of flow by axially extending annular guide blades that the spacing of these guide blades transversely to the direction of flow between themselves and relatively to the limiting walls is determined by a definite constant ratio of the average radii of curvature of the sub-divided separate reversing guide passages relatively to the widths thereof.

11. A multi-stage centrifugal pump or blower according to claim 1, wherein the reversing passages at their inner portions deviate from their radial direction for a relatively short distance into a direction askew to the blower axis, and turns tangentially to said axis at a relatively great radius towards and into the inlet port of the next rotor wheel.

12. A multi-stage centrifugal pump or blower according to claim 1, wherein on an outer part containing the reversing passages an inner guide passage body is arranged coaxially to the axis of the pump, said body being circular inside and outside so as to connect with the annular body for the reversing passages in said outer part and being formed with continuing portions to the inlet port in the next rotor wheel of the reversing passages in said outer part.

13. A multi-stage centrifugal pump or blower according to claim 12, wherein said inner guide passage body is provided with guide blades in the continuing portions of said reversing passages.

References Cited in the file of this patent UNITED STATES PATENTS 1,142,882 Johnson June 15, 1915 2,483,643 Karrer Oct. 4, 1948 2,596,646 Buchi May 13, 1952 2,596,647 Buchi May 13, 1952 FOREIGN PATENTS 342,065 Great Britain Ian. 29, 1931