Regenerative multi-stage compressor

Abstract

A regenerative compressor (100) configured to operate at pressures exceeding 50 bar comprises a motor (101), at least one magnetic drive coupling (1) connected to the motor (101) and suitable for transmitting rotational motion to at least one drive shaft (2), the drive shaft (2) being mechanically connected to the coupling (1) and two peripheral impellers (3, 4) being mounted on the shaft (2).

Description

Technical Field

[0001] The present invention relates to compressors operated with gas, and more particularly, to a novel regenerative multi-stage compressor specially designed for operation with gas. Background Art

[0002] Single-stage compressors are known which produce a pressure increase in a gas by increasing the rotational speed of a single-stage impeller.

[0003] When the compressor is operated with gases having a low molecular weight (eg ammonia, hydrogen, helium, methane, etc.), the increase in speed required to achieve the required pressure brings about some disadvantages.

[0004] First, in order for the compressor to operate at high speeds, it needs to be equipped with very expensive bearings made of ceramic materials, and often requires the use of grease.

[0005] Introducing grease into the machinery carries the risk of contaminating the process gas, with serious consequences for the equipment subsequently served by the compressor.

[0006] In addition to the above, the increase in speed causes a rise in the temperature inside the machine, which makes it impossible to maintain its thermal balance. This drawback limits the machine's areas of application, since the increase in speed reduces the reliability of the compressor, which requires more frequent maintenance operations. Conversely, in some specific areas, maintenance operations cannot always be carried out frequently, but only at predetermined intervals that must be as wide as possible.

[0007] Regenerative compressors are defined as turbines with tangential flow with low specific speed (about 0.03, while centrifugal compressors have a specific speed of about 0.1 and radial compressors have a specific speed of about 0.5), high head and low flow rate. These characteristics, as well as advantages related to the fact that they are not affected by stalls or pumping instabilities, make the use of these compressors very interesting in several fields, for example, in the chemical, petrochemical, pharmaceutical industries.

[0008] In the literature, regenerative compressors are also defined as circumferential compressors or turbines or resistance compressors. Although this configuration is mainly used to pump liquids, some theories supported by semi-empirical expressions have been proposed in the literature to explain the behavior of this type of machine when it is used to process gases.

[0009] One theory describes the pumping mechanism: A regenerative compressor is provided with an impeller having peripheral radial blades. As the impeller rotates in the direction of flow, the fluid is pushed between the blades toward the periphery of the impeller and then back again, toward the bases of other blades. This recirculation is done several times between the suction and delivery ports through a large number of blades, creating a multi-stage or regenerative effect. The path of the fluid is geometrically similar to a coiled spring that bends to form an incomplete circle, where each cycle adds energy to the fluid.

[0010] According to some authors, the friction that exists between the impeller and the fluid is due to the turbulent motion, which acts as the main force, causing the pumping action. The view put forward by these authors is that the pumping mechanism is caused by the shear stress generated in the fluid by the impeller.

[0011] The subject of this patent is a novel multi-stage compressor of the regenerative type, equipped with a magnetic drive coupling and specially designed to operate with gas.

[0012] The special and novel combination of technical features of this new compressor enables several advantages to be achieved, in addition to eliminating the above-mentioned disadvantages.

[0013] An important object of the present invention is to provide a compressor in which more than one stage is utilized to produce the required pressure increase, thereby eliminating the disadvantages associated with single-stage compressors of the known type.

[0014] More specifically, an object of the present invention is to provide a compressor in which the rotational speed of the impeller is reduced, thereby reducing the generation of heat compared to a single-stage compressor. Thus, it is not necessary to lubricate the bearings with grease, but dry bearings are used instead.

[0015] Since there are no contaminants inside the machine, the gas being processed is not subject to any alteration and therefore the new compressor is highly reliable.

[0016] Due to the reduced heat generation, the compressor operates at a lower temperature and is therefore safer, especially when handling gases classified as explosive. The compressor can more easily maintain a state of thermal equilibrium and avoid heat accumulation. As a result, all parts of the compressor operate more reliably: connected electric motors, bearings, windings. Summary of the invention

[0017] These and other direct and complementary objectives are achieved by the new regenerative multistage compressor, which has been specially designed and developed for gas operation.

[0018] According to the above definition, a new compressor is regenerative and includes:

[0019] -motor;

[0020] - at least one magnetic drive coupling connected to said motor and suitable for transmitting rotational motion to at least one drive shaft;

[0021] - the drive shaft is mechanically connected to the coupling;

[0022] - a first impeller mechanically connected directly or indirectly to the shaft;

[0023] - At least one second impeller mechanically connected directly or indirectly to said shaft.

[0024] Each of said impellers is of the peripheral type, that is to say it comprises a disc provided with radial or twisted blades mounted on one or both sides of the disc, depending on the size of the machine and the expected performances based on the design.

[0025] The impeller rotates integrally with the shaft, which in turn is supported by bearings. In a preferred configuration, the shaft comprises at least two supports, for example at two opposite ends thereof, and the impeller is mounted on the shaft in a space contained between the two supports.

[0026] Therefore, the novel compressor comprises at least two stages. Each stage preferably comprises two half-shells, with one of the impellers being mounted between them.

[0027] For each stage, each of the impellers rotates in a circumferential annular duct obtained between the half-shells. The annular duct communicates on one side with the gas suction port, the coils forming an angle of approximately 360°, and ends near the delivery port. The annular duct is interrupted by a preferably movable element that separates the low-pressure side (the side where the suction port is located) from the high-pressure side (the side where the delivery port is located).

[0028] The two stages are substantially identical to one another but are oriented so that they are offset, conveniently by 180°, to balance radial loads, thereby significantly reducing radial loads, further helping to increase the life of the bearings and thereby the life of the entire machine.

[0029] There is an annular cavity between the two stages which serves the function of dividing the flow between the two stages and allowing them to deflect.

[0030] The new compressor comprises a sealing element mounted near the impeller, mechanically locked and provided with a labyrinth profile, which separates the vortex in which the blade set of said impeller rotates from the inner cavity closest to the shaft, thus maximizing the sealing effect and volumetric efficiency, thanks to minimized internal circulation, due to leakage. In order to guarantee that the clearances are not compromised and the maintenance costs are minimized, said sealing element is made as a wearing or sacrificial part.

[0031] The new compressor solves another drawback, thereby eliminating another factor that reduces efficiency. The new compressor includes a dynamic barrier to prevent recirculation, obtained by the presence of a plurality of protrusions located on the shaft and rotating integrally with the shaft, which greatly reduces the clearance relative to the sealing element constrained between the shaft and the containment cup. In another embodiment, the shaft can be without protrusions and a sealing element provided with teeth can be inserted between the shaft and the containment cup.

[0032] The compressor comprises a plurality of sealing elements suitable for ensuring a static seal.For example and preferably, the compressor comprises a plurality of pairs of O-rings placed side by side, between which a path is formed for monitoring any leakage of the first O-ring which can be connected to a monitoring device.

[0033] In order to ensure effective internal recirculation of the gas, necessary to ensure the thermal balance of the compressor, the latter comprises a gas recirculation system composed of a series of channels and ducts obtained by various types of elements, as described below and claimed herein.

[0034] Each impeller is provided with a hole which communicates the vortex in which the blades of the impeller rotate with the inner cavity (referring to the cavity closest to the shaft), thereby slightly pressurizing the inner cavity itself.

[0035] The path of the gas will be described below, for example starting from the lower impeller, meaning the impeller which is further from the coupling and which defines for example the second stage.

[0036] The gas path continues through a series of preferably axial holes formed in the disk of the impeller, ie the axes of the holes are parallel to the axis of rotation.

[0037] The gas reaches the lower bearings, ie the bearings further from the coupling, and flows through them. If necessary, the support of the bearings can be provided with appropriate channels for maximizing the gas flow through the bearings.

[0038] The gas flow continues through an axial hole obtained inside the shaft between its lower end (further from the coupling) and the opposite upper end (closer to the coupling). At the upper end, or close to it, there is a channel through which the gas flows out of the shaft, flows through the channel between the body containing the internal magnet and the internal magnet itself, and reaches the support of the upper bearing, through which the gas flows as described with reference to the lower bearing. In addition, if the support is provided with a channel, the gas also flows through the said channel, which can obtain a higher flow rate.

[0039] Finally, through another duct formed in the suction chamber, the gas reaches the suction chamber itself, where it is at a low pressure and mixes with the gas entering the first stage.

[0040] To make the system even more efficient, the novel compressor preferably includes two further important devices in addition to creating a pressure differential between the scroll and the suction chamber of the first stage.

[0041] The first device is a tangential fan, which is located at the lower end of the shaft and has the function of directing the gas downwards.

[0042] The second means consists of one or more grooves which are formed on the outer surface of the inner magnet, in particular in a helical manner, in order to guide the flow of the gas in the region of the receiving body.

[0043] A further innovative feature relates to said support of the bearing, which is mechanically fixed to other fixed parts of the compressor.In another solution, as described above, said support comprises a series of axial grooves allowing the gas to flow therethrough.

[0044] Without the grooves, the gas would in any case flow through the bearing in such a way as to cool the bearing.

[0045] In the case of mounting bearings requiring the use of lubricants, a manifold can be provided which is configured so as to collect the deposited grease and retain it, thereby preventing it from being lost.

[0046] The magnetic drive coupling that provides torque to the shaft can be of any type available on the market and has a housing made of metal, ceramic, polymer compound, carbon fiber or other materials. The internal magnet, that is, the magnet that rotates inside the housing, can be located in any position according to the structural or design requirements.

[0047] The features of the novel compressor will be explained in more detail in the following description, with reference to the accompanying drawings, which are attached hereto by way of non-limiting examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 A cross-sectional view of a novel multi-stage compressor (100) is shown. According to the present invention, the coupling (1) can be used with Figure 1 The opposite arrangement is shown, wherein the coupling (1) is specifically mounted so that the cup (10) containing the internal magnets (11) faces the interior of the compressor (100). In the opposite configuration, the containing cup (10) can be mounted so that it faces the opposite direction.

[0049] Figure 2 Details of the impeller (3, 4) and part of the sealing element are shown.

[0050] Figure 3 A detail of a shaft (2) according to one possible embodiment is shown.

[0051] Figure 4A cross-sectional view of the impeller (3, 4) is shown, and Figure 4a A detail of the same impeller is shown, wherein the communication channel (31) between the vortex (V) and the inner cavity can be observed.

[0052] Figure 5 is a cross-sectional view of a portion of a compressor (100), schematically illustrating the gas recirculation path.

[0053] Figure 6 A three-dimensional view of a tangential fan (9) is shown, and Figure 7 Shown are an inner magnet (11) and its outer covering (110), which is provided with a spiral groove (111).

[0054] Figure 8 Shown are details of a manifold (231) designed to contain lubricant in the case where lubricated bearings (23) are installed in the compressor (100). DETAILED DESCRIPTION

[0055] The invention is a compressor (100) particularly suitable for operation with gas, configured to work at pressures exceeding 50 bar, comprising a motor (101), at least one coupling (1), preferably of the magnetic type, connected to the motor (101) and suitable for transmitting a rotational movement to at least one drive shaft (2).

[0056] The drive shaft (2) mechanically connected to the coupling (1) is in turn supported by bearings (23) in at least two supports (21, 22), for example near two opposite lower ends (2a) and upper ends (2b).

[0057] The compressor (100) comprises at least two impellers (3, 4), each impeller being directly or indirectly mechanically connected to the shaft (2), and wherein the impellers (3, 4) are mounted on the shaft (2) in the space contained between the two supports (21, 22).

[0058] Each of the impellers (3, 4) is of peripheral type and comprises a disk (31, 41) provided with a set of blades (32, 42) mounted on one or both sides of the disk (31, 41). Thus, the new compressor (100) comprises at least two stages (A, B), wherein each stage (A, B) comprises a casing (A10, B10), which in turn is formed by half-casings (A1, A2, B1), between which one of the impellers (3, 4) is mounted.

[0059] Each of the impellers (3, 4) rotates in a circumferential annular duct (5) obtained in the housing (A10, B10), wherein the annular duct (5) is connected to a gas suction port (at Figure 1 The coils are connected to the first stage A (visible in the figure and indicated by A3), and the coils form an angle of approximately 360° and are close to the delivery port (at Figure 1 The end of the second level B is visible in the figure and is indicated by B3).

[0060] For example, the annular duct (5) is interrupted by a preferably removable element which separates the low-pressure side (the side where the suction opening is located) from the high-pressure side (the side where the delivery opening is located).

[0061] The at least two stages (A, B) are substantially identical to each other, but are oriented such that they are offset, such as, for example and preferably, by 180°.

[0062] An annular cavity (7) is provided between the two shells (A10, B10) of the impeller (3, 4), the annular cavity having a duct communicating with the vortex (V) of the impeller, which plays the role of internal diversion so that the stages (A, B) can be offset.

[0063] One or more sealing elements (8) are mounted near the impeller (3, 4), are mechanically locked and are provided with a labyrinth profile, which separate the vortex (V) in which the blade set (32, 42) of the impeller (3, 4) rotates from the inner cavity closer to the shaft (2).

[0064] according to Figure 3 A first solution shown, in order to form a dynamic barrier preventing gas recirculation, comprises, on the shaft (2), between the impellers (3, 4), a plurality of protrusions (24) which rotate relative to one or more sealing elements (25) constrained between the shaft (2) at the height of the protrusions (24) and the casing (A10, B10).

[0065] In another solution not shown in the figures, one or more sealing elements equipped with teeth are inserted between the shaft (2) and the housing (A10, B10). According to the invention, in order to ensure static sealing, a pair of washers and O-rings arranged side by side are installed between the elements constituting the stationary part of the compressor (100), between which a path is established for monitoring any leakage of the first O-ring suitable for connection to a monitoring device.

[0066] exist Figure 5The gas recirculation path is schematically shown in the figure, and its function is to ensure the heat balance inside the compressor (100). Assuming that starting from the second stage (B), that is, starting from the lower impeller (3) farther from the coupling (1), the gas flows from the vortex (V) into the inner cavity, flows through one or more holes or channels (81) formed in the impeller (3), and connects the vortex (V) with the inner cavity.

[0067] The disc (31, 41) of the impeller (3, 4) is provided with one or more holes or ducts (82) which connect the inner cavity with the bearing (23), wherein the gas flows into the bearing (23) through the holes or ducts (82).

[0068] In one possible solution, said supports (21, 22) of the bearing (23) are provided with suitable holes or ducts (83, 86) for the passage of gas, designed to maximize the gas flow through the bearing (23) itself.

[0069] The gas then flows into the shaft (2) through the axial hole, from its lower end (2a) to its upper end (2b) near the coupling (1).

[0070] In or near the upper end (2b) of the shaft (2), there is a passage (85) which communicates the interior of the axial bore (84) of the shaft (2) with the interior of a receiving cup (10) containing the coupling (1), in which at least one internal magnet (11) is received.

[0071] like Figure 7 As shown, the outer surface (110) of the inner magnet (11) is provided with one or more grooves (111) designed to guide the gas flow in the area of ​​the receiving cup (10). The one or more grooves (111) are preferably spiral.

[0072] The cup (10) comprising the coupling (1) is made of metal, ceramic, polymer compound, carbon fiber or other materials.

[0073] The gas then flows through the upper bearing (23) and / or through a further passage (86) obtained in the upper support (22) and reaches the inner chamber of the first stage (A). The inner chamber (C) communicates with the suction chamber (A4) through a communication duct (87), through which the gas from the coupling (1) enters the suction chamber (A4) itself and mixes with the inflowing gas.

[0074] The compressor (100) preferably further comprises a tangential fan (9), which is located at the lower end of the shaft (2) and serves to guide the gas downward.

[0075] According to the invention, the new compressor (100) may furthermore comprise means for generating a further air flow in order to cool the top of the compressor (100), ie the part where the outer magnets (12) of the coupling (1) are located.

[0076] According to the invention, the housing (13) of the external magnet (12) is provided with one or more holes or openings, which are conveniently protected by a filter cap through which air flows.

[0077] Furthermore, the external magnet (12) may be provided with an integrated fan, for example on the upper part of the external magnet (12) itself, which fan generates the required flow in the hollow space (14) between the external magnet (12) and the housing (13).

[0078] Therefore, with reference to the above description and accompanying drawings, the following claims are expressed.

Claims

1. A compressor (100) of the regenerative type, operating on gas, configured to operate at a pressure exceeding 50 bar, said compressor comprising a motor (101), at least one magnetic drive coupling (1) connected to said motor (101) and suitable for transmitting a rotational movement to at least one drive shaft (2), said drive shaft (2) being mechanically connected to said coupling (1), characterized in that The compressor comprises at least two impellers (3, 4), each of which is directly or indirectly mechanically connected to the shaft (2), each of which is of peripheral type and comprises a disk (31, 41) provided with a set of blades (32, 42), the set of blades (32, 42) being mounted on one or both sides of the disk (31, 41), and wherein the shaft (2) is in turn supported by bearings (23) in at least two supports (21, 22), and wherein the impellers (3, 4) are mounted on the shaft (2) in a space contained between the two supports (21, 22), And, wherein the compressor comprises at least two stages (A, B), each stage comprising a casing (A10, B10) composed of two half casings (A1, A2, B1), one of the impellers (3, 4) being mounted between the two half casings, The at least two stages (A, B) are identical to each other but oriented 180° offset, and wherein between the at least two housings (A10, B10) of the impellers (3, 4) there is an annular cavity (7) which acts as an internal manifold to offset the stages (A, B), Furthermore, the compressor (100) includes a gas recirculation system so that gas flows through the bearing (23).

2. The compressor (100) according to claim 1, characterized in that: Each of the impellers (3, 4) rotates in a circumferential annular duct (5) obtained in the housing (A10, B10), and wherein the annular duct (5) communicates with a gas suction port on one side, the coil forms an angle of 360° and ends near a delivery port.

3. The compressor (100) according to claim 2, characterized in that: The annular duct (5) is interrupted by a detachable element, which separates a low-pressure side from a high-pressure side, the low-pressure side being the side where the suction port is located, and the high-pressure side being the side where the delivery port is located.

4. The compressor (100) according to claim 1, characterized in that: It comprises a sealing element (8) mounted near the impeller (3, 4) which separates a vortex (V) in which the set of blades (32, 42) of the impeller (3, 4) rotates from an inner cavity closer to the shaft (2).

5. The compressor (100) according to claim 1, characterized in that The shaft (2) comprises a plurality of protrusions (24) contained between the two impellers (3, 4) and one or more sealing elements (25) constrained between the shaft (2) and the housing (A10, B10) at the height of the protrusions (24), or, conversely, the compressor (100) comprises one or more sealing elements provided with teeth inserted between the shaft (2) and the housing (A10, B10) in order to create a dynamic barrier preventing gas recirculation.

6. The compressor (100) according to claim 1, characterized in that Between the fixed parts constituting the compressor (100) there are pairs of gaskets or O-rings placed side by side, between which a path is formed for monitoring any leakage of the first O-ring adapted to be connected to a monitoring device.

7. The compressor (100) according to claim 4, characterized in that Each of the impellers (3, 4) is provided with a hole or passage (81) which connects the vortex (V) in which the blades (32, 42) of the impeller (3, 4) rotate with the inner cavity.

8. The compressor (100) according to claim 4, characterized in that The disc (31, 41) of the impeller (3, 4) comprises one or more holes or ducts (82) which connect the inner cavity (C) with the bearing (23).

9. The compressor (100) according to claim 1, characterized in that: Said supports (21, 22) of the bearing (23) are provided with appropriate holes or ducts (83, 86) for the passage of gas, designed to maximize the gas flow through the bearing (23) itself.

10. The compressor (100) according to claim 1, characterized in that The shaft (2) is provided with an axial hole (84) for the passage of gas along the shaft (2) itself.

11. The compressor (100) according to claim 10, characterized in that The shaft (2) comprises a passage (85) at its upper end (2b) closest to or near the coupling (1), which connects the interior of the axial hole (84) of the shaft (2) with the interior of a receiving cup (10) designed to receive the coupling (1), and at least one internal magnet (11) is received in the receiving cup.

12. The compressor (100) according to claim 4, characterized in that It comprises a communication conduit (87) which connects the inner cavity with the suction cavity of each impeller (3, 4), and the gas from the coupling (1) flows into the suction cavity itself through the communication conduit and mixes with the inflowing gas.

13. The compressor (100) according to claim 1, characterized in that It comprises a tangential fan (9) which is located at the lower end of the shaft (2) and has the function of directing the gas downwards.

14. The compressor (100) according to claim 11, characterized in that The outer surface (110) of the inner magnet (11) comprises one or more grooves (111) for directing the flow of gas in the region of the containment cup (10).

15. The compressor (100) according to claim 11, characterized in that The receiving cup (10) including the coupling (1) is made of metal, ceramic, polymer compound, carbon fiber or other materials, and is configured so that its axis is parallel to or coincides with the axis of the shaft (2) and faces the inside of the compressor (100) or the opposite direction.

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