Positive displacement rotary machine

Abstract

A rotary machine for fluid processing, comprising a static casing (2) with a first and second port (H, L) for allowing fluid out of and into the rotary machine. The rotary machine comprises a rotor body (4, 4) attached to a main shaft (3) arranged within the static casing (2), the rotor body (4, 4) has a center axis (R) arranged an offset distance (e) from a center axis (M) of the main shaft (3), the rotary machine further comprising a sealing vane (5, 5) having a vane tip (6, 6), and a vane moving system (8, 8) operationally connected between the rotor body (4, 4) and the sealing vane (5, 5) for maintaining a vane tip seal face (6a, 6c) of the vane tip (6, 6) in a sealing proximity to the rotor body outer face (4a, 4b).

Claims

1. A rotary machine for fluid processing, comprising a static casing with a first port and a second port for allowing fluid out of and into the rotary machine; the rotary machine comprising a rotor body attached to a main shaft, said main shaft being arranged within said static casing; said main shaft having a rotational center axis which is coincident with a center axis of a casing bore in said static casing; said rotor body having a first geometric center arranged an offset distance from said rotational center axis of said main shaft; the rotary machine further comprising a sealing vane having a vane tip; and a vane moving system operationally connected between said rotor body and said sealing vane for maintaining a vane tip seal face of said vane tip in a sealing relationship with said rotor body; said rotor body having a cross section with two different circular cylinder segments, a first segment with an outer surface having a geometric center coinciding with said first geometric center, and a second segment with an outer surface having a second geometric center coinciding with said rotational center axis, and said second segment outer surface being concentric to and co-radial with said casing bore to seal against a casing inner wall of said bore at all rotational positions of said rotor body; said vane moving system comprising at least one connecting rod operationally connected at a first end to said rotor body; said at least one connecting rod being connected to a crank portion on said main shaft, said crank portion being concentric with said first segment outer surface of said rotor body, wherein that said vane tip seal face having a semi-circular cylindrical seal face, facing said first segment outer surface of said rotor body; in a first alternative, said vane tip seal face having a radius; said connecting rod at a second end thereof being operationally connected to a pivot arm at a cross pin thereof; said pivot arm being rigidly connected to said vane; said cross pin being concentric with said semi-circular face of said vane tip, and a length of said connecting rod between the center axes of said crank portion and said cross pin being equal to a radius of said first segment outer surface plus the radius of the vane tip; or in a second alternative, said vane tip comprising a vane tip element that is rotatable relative to said vane, said vane tip element having a first semi-circular cylindrical face that is concentric with an axis of rotation between said vane tip element and said vane, said vane tip element being fixedly connected to said connecting rod, said vane tip element having a second semi-circular cylindrical seal face that is concentric and co-radial with said first segment outer face of said rotor body.

2. The rotary machine according to claim 1, wherein the rotary machine further comprises a vane support mechanism located in the interface between said casing and said vane.

3. The rotary machine according to claim 2, wherein said vane support mechanism comprises a cavity defined in said casing, said cavity being open towards said vane, said cavity and a vane seal face forming a closed chamber; said vane having a protrusion extending into said cavity and forming a seal towards an inner wall of said cavity, thereby dividing said closed chamber into a first closed volume and a second closed volume.

4. The rotary machine according to claim 2, wherein said vane support mechanism further comprises a fluid adjusting arrangement providing adjustment of a pressure of said first and/or second volume to control the movement of the vane.

5. The rotary machine according to claim 3, wherein said vane support mechanism further comprises a fluid adjusting arrangement providing adjustment of a pressure of said first and/or second volume to control the movement of the vane.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a cross sectional view of a rotary machine, illustrating a vane according to the first alternative, viewed from the end,

(2) FIG. 2 shows a cross sectional view of the rotary machine from FIG. 1, viewed from the side,

(3) FIG. 3 shows the rotary machine from FIG. 1, viewed from the outside,

(4) FIG. 4 shows a rotary machine with a rotor body according to the invention,

(5) FIG. 5 shows a cross sectional view of a rotary machine, illustrating a vane according to the second alternative, viewed from the end,

(6) FIG. 6 shows a cross sectional view of the rotary machine of FIG. 5, viewed from the side,

(7) FIG. 7 shows the rotary machine of FIG. 5, viewed from the outside,

(8) FIG. 8 shows a detailed view of an integrated vane support mechanism of the sealing vane.

DETAILED DESCRIPTION OF THE INVENTION

(9) For simplicity, equal features have been referred to by equal reference numbers in the different figures.

(10) FIG. 1 shows a cross section of a positive displacement rotary machine 1 having a vane according to the first alternative.

(11) The rotary machine 1 comprises an outer casing 2 with a cylindrical inner wall 2a. The outer casing 2 having a first port L and a second port H. The first and second port L, H are adapted to let a working fluid F into and out of the casing 2. The direction of the fluid F through each port L, H depends on the use of the rotary machine 1. The reference number 18 refers to a valve arrangement that is arranged in association with the port H to let the working fluid into or out of the casing 2.

(12) The rotary machine 1 further comprises a main shaft 3 rotatably supported in the outer casing 2. The main shaft 3 is concentrically arranged within a casing bore 1a. The casing bore 1a is defined as the bore within the outer casing 2. The outer boundary of the casing bore 1a is the same as the cylindrical inner wall 2a. A centre axis M (FIG. 2) through the main shaft 3 is thus coincident with the centre axis M of the casing bore 1a. The centre axis M has a distance h to the cylindrical inner wall 2a.

(13) A rotor body 4 is further attached to the main shaft 3.

(14) As shown in FIG. 1, the rotor body outer surface 4a is mainly cylindrical, with a geometric centre R parallel to and offset from a rotational centre axis M. A radius r of the rotor body outer surface 4a and the rotor offset e, is determined so that the part of the rotor body outer surface 4a furthest away from the rotational centre axis M is always in proximity to the casing inner wall 2a. This will create a seal between the casing inner wall 2a, and the rotor body outer surface 4a, without the rotor body 4 necessarily contacting the casing 2. This further results in that any friction between the rotor body 4 and the casing 2 may be avoided. The rotary machine 1 further comprises a sealing vane 5. The sealing vane 5 is pivotably supported in the casing 2, by means of a vane shaft 7. The vane shaft 7 has a pivot axis V (see FIG. 2) that is parallel to and spaced apart from the rotational centre axis M of the main shaft 3.

(15) The sealing vane 5 comprises a vane tip 6 arranged at the free end of the sealing vane 5, i.e., at the opposite end of the pivot axis V. The vane tip 6 may have a semi-circular cylindrical outer surface 6a. The sealing vane 5 is further arranged in the static casing 2 so that a vane tip outer surface 6a (see FIG. 8) is always in sealing proximity to the rotor body outer surface 4a, hence forming a seal between the rotor body 4 and the vane 5. This is further illustrated in FIG. 1.

(16) The sealing vane 5 also has a sealing face 5a. The sealing face 5a has a semi-circular cylindrical shape with its centre axis collinear with the centre axis V of the vane pivot axis. The sealing face 5a seals against a part 2b of the casing 2, effectively between the first and second port L, H.

(17) Thus, a closed working chamber W is formed between the rotor body 4, the casing inner wall 2a and the vane 5. The volume of this working chamber W will increase or decrease as the rotor body 4 rotates, depending on the rotational direction, resulting in compression or expansion of the working fluid F.

(18) An embodiment, shown in FIG. 4, of the rotary machine 50, shows a different configuration of a rotor body 4. In this embodiment the rotor body 4 does not have a cylindrical outer surface 4a. Instead, the rotor body has an approximately lens-shaped cross section. The shape comprises two different circular cylinder segments. The shape comprises a first segment with an outer surface 4b having its geometric centre R offset from the rotational centre axis M by a distance rotor offset e, to form a seal against the sealing vane tip 6a. The rotor body further comprises a second segment with an outer face 4c concentric to and co-radial with the casing inner wall 2a to seal against the casing inner wall 2a.

(19) The rotary machine 1 may further comprise a vane moving system 8. A first embodiment of this is illustrated in FIGS. 2 and 3. The vane moving system 8 comprises one or more connecting rods 9. Each connecting rod 9 connecting the pivoting sealing vane 5 to a crank 10, via a pivot arm 11. The pivot arm 11 is rigidly mounted to the vane 5 in one end.

(20) The pivot arm 11 and the connecting rod 9 are rotationally connected to each other in respective ends via a cross pin 12, as shown in the FIG. 2.

(21) The connecting rod 9 is further in the opposite end rotationally connected to the crank 10.

(22) The crank 10 may as the FIGS. 2 and 3 shows, be an integrated part of the main shaft 3. However, the center axis of the crank 10 is arranged offset of the rotational centre axis M of the main shaft 3. This result in an offset rotation of the crank 10 and a consequent linear motion of the connecting rod 9 when the main shaft 3 rotates. The crank offset distance is the same distance e as the distance between the centre axis of the main shaft M and the centre axis of the rotor body R.

(23) The offset of the crank 10 being equal to the offset of the rotor body 4. This means that the geometrical center of the rotor body R and the center axis of the crank 10 being coincident.

(24) FIGS. 1 to 4 shows one embodiment of the vane moving system 8 in which the cross pin 12 linking the connecting rod 9 to the pivot arm 11 is concentric with the semi-circular cylindrical shape of the vane tip sealing face 6a. The length P of the connecting rod 9 also being equal to the sum of the length of the rotor body radius r and the vane tip radius v (FIG. 1). The length P is defined as the distance between the geometrical center R and the axis C of the cross-pin 12. Thus, the connecting rod 9 will guide the pivoting sealing vane 5 so that the vane tip 6a is always tangent to the rotor body outer face 4a, creating a sealing line S (illustrated in FIG. 8) without the need for contact between the parts, i.e., rotor body 4 and the sealing vane tip 6a. This results in that no friction will occur between the vane tip 6a and the rotor body outer face 4a.

(25) More precisely, the semi-circular cylindrical face of the vane tip 6a is always tangent to the cylindrical rotor body outer face 4a.

(26) FIGS. 5 to 7 shows another embodiment of a sealing vane 5 and vane moving system 8 according to the invention.

(27) In the embodiment the rotary machine 60 in FIG. 5-7 a vane tip 6 element is rigidly connected to the connecting rod 9. The vane tip 6 element has a first semi-circular face 6b sealing against the vane 5, and a second semi-circular face 6c sealing against the rotor body outer face 4a. As the FIG. 5 shows, the first semi-circular face 6b is adapted to mate with a vane semi-circular face 5b of the vane 5. Similarly, the second semi-circular face 6c is adapted to mate with the circular shape of the rotor body outer face 4a.

(28) The vane tip 6 is connected to the vane 5 by the vane tip bearing 17 (FIG. 6), ensuring that the vane 5 will follow the motion of the vane tip 6. This embodiment has the advantage that the vane tip second sealing face 6c may be both concentric and co-radial as the rotor body outer face 4a. This provides a better seal between the second sealing face 6c and the rotor outer face 4a than two faces having different radii, sealing only in a tangent line.

(29) The following description is equally relevant for all the embodiments of the invention.

(30) As the vane 5, 5 and the rotor body 4 are the only moving parts in the working chamber W, this means there is no need for contact between any moving parts of the working chamber W. Consequently, there is no need for lubricant here either and contamination of the working fluid can be avoided.

(31) All relative motion between parts in the working chamber W is controlled by the main shaft 3 and vane moving system 8, 8. All necessary bearing functions are handled by the main rotor bearing 13, crank bearing 14, vane shaft bearing 16 and connecting rod bearing 15 (for the embodiment shown in FIG. 1-4) or vane tip bearing 17 (for the embodiment shown in FIGS. 5-7). All these bearings can then be located away from the working chamber W. Since the motions of the rotor body 4 and the vane 5 are motions that may be transferred by the cylindrical shafts 3, 7, 6, 10, 12.

(32) The bearings 13, 14, 15, 16, 17 may be oil lubricated and separated from the working chamber W by simple shaft seals. This is per se known.

(33) The functioning of the vane moving system 8, 8 is thus so that it is linking the connection between the rotor body 4 and the vane tip 6, 6 without the need of connection inside the working chamber W. The connecting rod 9 is given an oscillating movement by the crank 10.

(34) For the embodiment shown in FIG. 1-4, this provides an oscillating movement of the pivot arm 11 that is linked to the connecting rod 9. Since the pivot arm 11 is fixedly attached to the vane 5, the vane 5 will move accordingly.

(35) For the embodiment shown in FIG. 5-7 the vane tip 6 is fixed to the connecting rod 9 and will move with it. The vane tip 6 element is rotatably connected to the vane 5, so that the oscillating motion of the connecting rod 9 and the vane tip 6 also provides an oscillating movement of the vane 5. In FIG. 7 it is indicated a through hole, formed as a slot 26 in the static casing wall 2. The slot 26 defines the path where the part of the connection rod 9 that is connected to the vane 5, is able to move.

(36) In all the embodiments, the elements of the vane moving device 8, 8 is arranged so that the rotor body 4, 4 and the vane 5, 5 moves by the vane moving device 8, 8 and not by any contact between the rotary body 4, 4 and the vane 5, 5.

(37) The rotary machine 1 may further comprise one or more vane support mechanisms 20 located in the interface between casing housing 2 and the vane 5. This is illustrated in detail in FIG. 8.

(38) FIG. 8 shows the vane support mechanism 20. The vane 5 may have a sealing protrusion 21 extending from the vane sealing face 5a. The protrusion 21 may for instance be positioned at the mid-point of the sealing face 5a.

(39) The vane support mechanism 20 comprises a cavity K in the casing 2 in which the protrusion 21 can move freely within the pivot range of the sealing vane 5. The pivot range is the space within the cavity K between end positions O and N as indicated in the FIG. 8.

(40) The protrusion 21 is adapted to seal against a cavity wall 2b effectively, forming two separate closed volumes A and B, that may be connected to the machines working chamber, and therefore containing the working fluid F.

(41) The oscillating motion of the vane 5 causes large dynamic forces Fd on the vane 5 and vane movement system 8. The motion will also cause a compression of volume A and expansion of volume B, or vice versa, depending on the direction of the stroke. This produces a differential pressure between volume A and B, which again generates a force Fp on the protrusion 21. This force will counteract the dynamic forces Fd, and therefore greatly offload the vane 5 and vane moving system 8.

(42) The vane support mechanism 20 further may comprise one or more fluid supply channels 22 connecting each of the two volumes A, B to a compressor port L or H (FIG. 1, 4, 5), for supplying fluid into the volumes A, B. There may further be non-return valves 23 in the fluid supply channels 22 to prevent backflow and flow between the volumes A, B. The vane support mechanism 20 may further have fluid return lines 24 connecting each volume to the compressor inlet and/or outlet port, a fixed or adjustable throttling device 25, such as a valve, in the fluid return lines 24, to set the maximum obtainable pressure in each volume.

(43) Referring to FIG. 8, when the machine is operating, the vane 5 will oscillate so that the protrusion 21 moves between its upper position O and lower position N. The dynamic force Fd will be at its maximum in the direction away from the rotor body 4 when the protrusion 21 is at its upper position O, and its maximum in the direction towards the rotor body 4 when the protrusion is at its lower position b.

(44) The vane support mechanism 20 uses the vane's 5 motion to fill and compress working fluid in the two volumes A, B on each side of the vane seal face protrusion 21.

(45) As the protrusion 21 is at its upper position O, the volume A will be fully compressed, while the volume B will be uncompressed or expanded, depending on the settings of the throttling device 25. The pressure difference between the two volumes A, B acts on the protrusion 21, exerting a pressure force Fp on the vane 5 acting towards the rotor body 4, i.e., opposite of the dynamic force Fd.

(46) As the vane 5 with the protrusion 21 moves from its upper position O towards its lower position N, the dynamic force Fd is gradually reduced, before changing direction and reaching its maximum in the direction towards the rotor body 4 when the protrusion 21 reaches its lower position N. At the same time the volume A is expanding, and volume B is compressed.

(47) By selecting adequate width of the protrusion 21 and adjusting the max. pressure in the two volumes A, B, using e.g. the throttling devices 25, the force Fp from the vane support mechanism 20 can counteract the dynamic forces, and greatly reduce the total forces on the vane 5.

(48) This is beneficial because it prevents unwanted clearance between the vane tip seal face 6a and the rotor body outer face 4a, arising from dynamic forces FD forcing the vane 5 away from the rotor body 4 as it moves towards its upper position O. In this part of the motion, the working fluid F in the working chamber W is at or close to its maximum pressure, so it is very important to minimize clearances to avoid volumetric losses.

(49) Further the support mechanism 20 reduces forces on the connecting rod bearing 15 and vane tip bearing 17. This results in that smaller, lighter bearings and other moving parts can be used, which again means reduction of e.g., size, complexity, cost, and vibrations to the surroundings.

(50) Even though the vane support mechanism 20 is illustrated with the vane embodiment from FIG. 1, the vane support mechanism is equally applicable for the vane embodiment illustrated in FIG. 5.

(51) The positive displacement rotary machine 1 may be suitable for different purposes, for instance as a compressor and/or expander for gases of gas/liquid mixtures.

(52) When working as a driven machine, e.g. compressor or pump, rotational motion is applied to the main shaft 3 by for example an electric motor, to rotate the rotor 4. When working as a driver, e.g. expander, the pressure in the working chamber W drives the rotor 4, and rotational motion is transferred via the main shaft 3 to a consumer, e.g. an electric generator.

(53) Working fluid enters the machine through one of the first or second ports L or H, depending on whether the rotary machine 1 operates as a compressor or an expander.

(54) In a compressor, the working fluid enters the working chamber W through the port L. The rotor body 4 rotates clockwise referring to FIG. 1. Once the sealing line or portion between the rotor body 4 and the casing 2 has moved past the port L, a closed working chamber W is formed between the rotor body 4, the static casing inner wall 2a and the sealing vane 5. The volume of this working chamber W will decrease as the rotor body 4 continues its rotation, and the pressure of the working fluid F entrapped in the working chamber W will increase. Once the required discharge pressure is reached, the working fluid F will exit through the second port H.

(55) A valve arrangement 18 or similar in the high-pressure port H is necessary to control the machines volumetric ratio. When designed as a compressor, this can be standard compressor valves, or other types of reed valves or non-return valves that will open once the pressure in the working chamber W reaches or slightly exceeds the pressure downstream the valve 18. These types of valves require no further control mechanisms.

(56) When working as an expander, the valves 18 may need to be controlled to open at a given position, e.g. by a mechanical control such as a cam shaft that sets the valve position based on the rotor body 4 position.

(57) Even though the figures illustrate different embodiments, it is to be noted that the embodiments of the rotor body 4, 4 may be used in any of the embodiments 1-3 or 5-7.

(58) For instance, the rotor body 4 of FIG. 5 may be used together with the vane of FIG. 5.

(59) The vane support mechanism may be used in all embodiments of the invention.

FIGURE LIST

(60) 1rotary machine, first embodiment 2static casing 2acasing inner wall 2bcasing cavity seal face 3main shaft 4rotor body, first embodiment 4rotor body, second embodiment 4arotor seal face 4brotor bodyvane seal face 4crotor bodycasing seal face 5, 5sealing vane 5avanecasing seal face 5bvanevane tip seal face 6vane tip, first embodiment 6vane tip, second embodiment 6avane tiprotor seal face 6bvane tipvane seal face 6cvane tiprotor seal face, fixed vane tip 7vane shaft 8vane moving system, first embodiment 8vane moving system, second embodiment 9, 9connecting rod 10crank 11pivot arm 12cross pin 13main rotor bearing 14crank bearing 15connecting rod bearing 16vane shaft bearing 17vane tip bearing 18valve 20vane support mechanism 21sealing protrusion 22fluid supply channels 23Flow restrictor, non-return valves 24fluid return line 25throttling device 26slot 50rotary machine, second embodiment 60rotary machine, third embodiment Kvane support mechanism chamber Afirst closed volume Bsecond closed volume Ovane protrusion upper position Nvane protrusion lower position Ssealing line Mrotational center axis of main shaft and geometrical center axis of casing bore Rgeometrical center of rotor body and crank Ccenter axis of cross pin and vane tip Vcenter axis of vane shaft Wworking Chamber Fworking fluid Lfirst portInlet fluid port/outlet fluid port Hsecond portoutlet fluid port/inlet fluid port Plength of connecting rod Fddynamic forces on vane Fpforce on vane arising from differential pressure on sealing protrusion 21 ddiameter of rotor body erotor offset distance ccasing inner bore radius rrotor seal face radius vvane tip radius foffset distance between center axis of vane shaft and casing inner bore radius.