Centrifugal compressor and method of operating a centrifugal compressor to produce a uniform inlet flow of process gas

Abstract

A centrifugal compressor (100) has a casing (110) with two or more compressor inlets (120) for process gas to be compressed; an impeller (130) is located inside the casing (110) to receive inlet flow of process gas from the two compressor inlets (120) through a plenum (115) and to increase the gas pressure as the process gas flows into the impeller (130); due to the two or more inlets (120), uniformity of flow at the inlets (120) can be achieved by a short collector pipe (121) fluidly connected upstream of the inlets (120); as there are fewer restrictions, the piping design of a compressor system including such a compressor becomes easy.

Description

Technical Field

[0001] The subject matter disclosed herein relates to centrifugal compressors, compressor systems, and methods for operating centrifugal compressors. Background Art

[0002] The known centrifugal compressor has a housing with a single inlet and an impeller located inside the housing and downstream of the inlet. The inlet receives an inlet flow of process gas to be compressed, which is compressed by the impeller from a single suction duct fluidly connected upstream of the inlet.

[0003] The design of known centrifugal compressors is based on the assumption that the inlet flow of the process gas is uniform. Excessive non-uniformity in the inlet flow may cause the compressor's impeller to malfunction, thereby affecting its performance or potentially even leading to surge and structural damage to the compressor.

[0004] To avoid such problems, compressor manufacturers recommend keeping the portion of the suction duct immediately upstream of the compressor inlet straight for at least a predetermined length, thereby reducing or eliminating any unevenness in the inlet flow. Therefore, such rules should be followed when designing a plant that includes one or more compressors, and especially when designing its ducting.

[0005] This length increases with the cross-sectional area of ​​the compressor inlet, which in turn depends on the size of the compressor and the flow rate it handles. Therefore, while it is relatively easy to follow this application principle for small compressors, large compressors require long suction pipes.

[0006] Large compressors are attractive due to their high efficiency and ability to handle large flow volumes. However, for large compressors, straight suction piping can reach lengths of tens of meters, which can severely restrict plant piping design. This problem is even more severe for preassembled plant modules containing compressors, particularly those designed for transport after assembly, such as on ships. Summary of the Invention

[0007] According to a first aspect, the subject matter disclosed herein relates to a centrifugal compressor comprising a housing and an impeller located within the housing; the housing having two or more inlets for receiving an inlet flow of a process gas to be compressed by the compressor. A suction duct located immediately upstream of the inlets is used to reduce or eliminate flow non-uniformities. The length of the suction duct can be selected based on the cross-sectional area of ​​each inlet, rather than the total cross-sectional area of ​​all inlets. Thus, due to the number of inlets, the suction duct can be short.

[0008] According to a second aspect, the subject matter disclosed herein is directed to a compressor system comprising at least one centrifugal compressor having two or more inlets for receiving an inlet flow of a process gas. Because the suction piping immediately upstream of the inlets is preferably straight but can be short, system piping is easier to manufacture due to fewer restrictions.

[0009] According to a third aspect, the subject matter disclosed herein relates to a method of operating a centrifugal compressor. A process gas stream to be compressed is generated and then separated into a first process gas stream and a second process gas stream; each of the process gas streams travels along a preferably straight path to reduce or eliminate flow non-uniformities, and the two process gas streams are then suitably combined before being fed to an impeller of the compressor. The gas streams are preferably combined so that the gas flow received by the impeller is optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more complete understanding of the disclosed embodiments of the present invention and many of its attendant advantages will be readily obtained by reference to the following detailed description when considered in conjunction with the accompanying drawings, which likewise become better understood, wherein:

[0011] Figure 1 shows a simplified transverse cross-sectional view of an embodiment of a centrifugal compressor according to the herein disclosed subject matter,

[0012] Figure 2 Shown Figure 1 A simplified longitudinal section view of a compressor,

[0013] Figure 3 Shown Figure 1 A more detailed transverse cross-sectional view of the compressor,

[0014] Figure 4 Shown Figure 1 A more detailed partial view of the compressor in longitudinal section, and

[0015] Figure 5 A flow chart illustrating an embodiment of a method according to the subject matter disclosed herein is shown. DETAILED DESCRIPTION

[0016] The centrifugal compressor disclosed herein comprises a casing and an impeller located inside the casing. The casing has two or more inlets for receiving a process gas stream to be compressed by the compressor. A suction duct is connected upstream of the inlet of the compressor for reducing or removing flow unevenness in the gas stream fed to the inlet; the suction duct can take the form of a straight (usually identical) duct. In this way, the amount of process gas that can be compressed by compression depends on the total cross-sectional area of ​​all these ducts. However, the length of each of these ducts depends on the cross-sectional area of ​​a single duct, not on the total cross-sectional area of ​​all ducts. Therefore, they can be short and not bulky as a whole.

[0017] Reference will now be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present disclosure, not limitation thereof. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the present disclosure without departing from the scope or spirit of the present disclosure.

[0018] Figures 1 to 4 An embodiment of a centrifugal compressor 100 is shown, such as may be arranged along a gas pipeline or within a gas processing plant.

[0019] The centrifugal compressor 100 is arranged to compress a process gas stream. 3 / h and about 600,000m 3 The features disclosed herein are particularly advantageous in large centrifugal compressors with gas flow rates between 1000 Å / h and 2000 Å / h.

[0020] The centrifugal compressor 100 has a housing 110. The housing 110 defines a plenum 115 and has two inlets 120 configured to deliver an inlet process gas stream to the plenum 115, such as Figure 1 and Figure 2 According to alternative embodiments, the number of inlets can be higher, for example three or four, i.e. at least one more inlet is added to the two mentioned; however, having only two inlets provides good results and is a good compromise. In large centrifugal compressors, each of the two inlets may have a diameter of between about 0.75 m 2 About 3.3m 2 Preferably, for a flow rate of 300,000 m 3 / h compressor, the cross-sectional area of ​​each inlet is less than 1.7m 2 , and for a flow rate of 500000m 3 / h compressor, the cross-sectional area of ​​each inlet is less than 2.8m 2 .

[0021] According to the embodiment of the drawings, the plenum chamber 115 has a substantially cylindrical shape; the plenum chamber 115 can house a portion of the shaft 160 of the compressor; the plenum chamber 115 can also house the guide member 150. The plenum chamber 115 is radially delimited by an outer wall 116 and an inner wall 117 facing the outer wall 116. According to the specific embodiment of the drawings, the inner wall 117 corresponds to a portion of the outer surface of the guide member 150; therefore, if the shaft 160 and the guide member 150 are considered, the front part of the plenum chamber 115 (at the Figure 2 The left side of the center) is substantially annular in shape, and the rear portion of the plenum 115 (at Figure 2 Preferably, the plenum 115 has a circular symmetry axis.

[0022] The inlet 120 is preferably located on the outer wall 116 of the plenum 115, which is preferably cylindrical or frustoconical in shape. The plenum can be considered to be made of two equal or similar halves: the one with the inlet located on its proximal side and the other half with no inlet located on its distal side.

[0023] The plenum chamber 115 has an outlet; considering Figure 2 , outlet 118 is adjacent to inner wall 117 and faces outer wall 116 and inlet 120; specifically, it is an annular outlet and radially defines the front of plenum 115. Inlet process gas flows within plenum 115 from inlet 120 to outlet 118 and has a radial component of velocity directed toward the circular axis of symmetry of plenum 115.

[0024] The housing 110 houses an impeller 130 arranged downstream of the plenum 115 and is in fluid connection with the plenum 115. The impeller 130 is rotatable about an axis of rotation "R" extending in the longitudinal direction of the centrifugal compressor 100 and preferably coinciding with the circular symmetry axis of the plenum 115. The housing 110 further has an outlet downstream of the impeller 130, which outlet is not shown in the drawings.

[0025] A passage 125 is disposed between the outlet 118 and the impeller 130 to deliver process gas from the plenum 115 to the impeller 130. Specifically, a guide member 150 partially defines the passage 125 from the plenum 115 and separates the passage 125 from the rear portion of the plenum 115. The outlet 118 is located between the plenum 115 and the passage 125 at a narrow portion or bottleneck along the flow path of the process gas.

[0026] It should be noted that, unlike the above description, the plenum chamber may have a flat annular outlet instead of a cylindrical annular outlet (see Figure 2 118 in the drawing), and the channels may develop only substantially axially rather than initially substantially radially and ultimately substantially axially.

[0027] The impeller 130 is configured to exert suction to the gas in the plenum 115 by its rotation and to determine a flow of gas through the plenum 115 from the inlet 120 to the compressor outlet, while centrifugally increasing the pressure between the compressor inlet and the compressor outlet.

[0028] According to the working configuration of the centrifugal compressor 100, the plenum 115 is located downstream of the inlet 120 and upstream of the impeller 130 and is configured to uniformly distribute the pressure and velocity in the inlet process gas flow towards the impeller 130.

[0029] According to the embodiment of the drawings, the inlet 120 has an equal cross section (or substantially equal cross section); moreover, the inlet 120 is arranged symmetrically with respect to the meridional plane "M" of the compressor (i.e. the plane containing the rotation axis "R"). Such symmetry helps to uniformly distribute the pressure and velocity in the inlet process gas flow towards the impeller 130.

[0030] Preferably, the centrifugal compressor 100 comprises two collectors 121 connected to the casing 110, which are in fluid communication with the plenum 115 through the inlet 120. In particular, each collector 121 protrudes from the casing 110 in a rectilinear direction and has a collector inlet 122 connectable to an upstream suction gas duct and a collector outlet 123 connected to the inlet 120. The collectors 121 are arranged to convey the respective process gas flow from the two upstream suction ducts to the plenum 115 and are configured to reduce or eliminate the non-uniformity in the process gas flow from the collector inlet 122 to the collector outlet 123. In this way, the system ducts are subjected to lower constraints, as the inlet process gas flow can be directed in a desired manner.

[0031] Advantageously, the collectors 121 are arranged symmetrically with respect to the meridional plane "M" of the centrifugal compressor 100. The meridional plane is the plane containing the rotation axis "R". In particular, the meridional plane "M" is arranged perpendicularly with respect to the working configuration of the centrifugal compressor 100. Such symmetry helps to uniformly distribute the pressure and velocity in the inlet process gas flow towards the impeller 130.

[0032] Moreover, each collector 121 preferably has a distance between the collector inlet 122 and the collector outlet 123 of between about 1 and about 3 times the diameter of the collector inlet 122, more preferably between 1.3 and 2.5. In this way, the system ducts are subjected to lower constraints, as the inlet process gas flow is sufficiently directed to the plenum 115, independently of the external system ducts.

[0033] Advantageously, each collector 121 defines a diverging duct that diverges from the collector inlet 122 to the collector outlet 123 to decelerate the gas flowing therethrough. Preferably, the area ratio between the cross-sectional area of ​​the collector outlet 123 and the cross-sectional area of ​​the collector inlet 122 is between about 1.0 and about 1.3 to achieve the desired deceleration of the gas and thereby reduce turbulence and improve the uniformity of the gas flowing to the impeller 130. However, the use of a converging duct from the collector inlet 122 to the collector outlet 123 is not excluded, wherein the area ratio between the cross-sectional area of ​​the collector outlet 123 and the cross-sectional area of ​​the collector inlet 122 is between about 0.75 and about 1.0.

[0034] Preferably, each collector 121 has an end portion adjacent to its outlet 123 that extends longitudinally along a respective straight line "s"; the length of this portion may be, for example, at least 400 mm long; elsewhere, the collectors 121 may extend along a more or less curved line. Alternatively, the collectors 121 may be completely straight, such as Figure 1 and Figure 2 As shown in the example of , turbulence in the gas flow toward the inflation chamber 115 is reduced or avoided.

[0035] According to a preferred embodiment, the above-mentioned straight line "s" of the collector 121 does not intercept the rotation axis "R" of the impeller 130, as shown in FIG. Figure 1 Specifically, each straight line "s" has a minimum distance "d" from the axis of rotation "R" greater than 0 mm and less than about 1000 mm, preferably less than about 0.3 times the diameter of the outer wall 116; this means that the gas flow from the collector 121 is preferably not directed to the central area of ​​the inflation chamber 115, but is directed to the peripheral zone "Z" (i.e., Figure 1 ), which advantageously has a diaphragm, as explained below. However, it is not excluded that the straight line "s" intercepts the axis of rotation "R".

[0036] Preferably, the straight lines "s" of the collector 121 intersect each other and form an angle α in the range of about 15° to about 30° (see Figure 1 ). In other words, the collector 121 is preferably arranged so that the intersection of the line "s" is located in the plenum 115 on the opposite side of the collector 121 (and the inlet 120) relative to the rotation axis "R", as shown in FIG. Figure 1 Shown inside the zone "Z".

[0037] It should be noted that the straight lines "s" of the collector 121 intersect at the point of the zone, but the gas flows from the collector do not necessarily merge (and mix) in this zone. As will become apparent below, it is preferred that they do not substantially merge (and mix) in the zone but merge (and mix) later. Therefore, the above directions and angles are intended to delay the merging (and mixing) of the gas flows from the inlet and collector.

[0038] Preferably, the collector inlet 122 has equal cross-section and cross-sectional area. Specifically, the cross-sectional area may be between about 0.75 m 2 About 2.5m 2 In addition, preferably, the collector outlet 123 has a preferably equal cross-section, matching the cross-section of the inlet 120 as described.

[0039] Advantageously, the straight line "s" forms an angle β with the plane "T" which is transverse to the axis of rotation "R" of the centrifugal compressor 100 (see Figure 2 ); the angle β is preferably in the range of about 10° to about 20°. In this way, the axial flow of the gas entering the plenum 115 through the inlet 120 toward the impeller 130 is promoted and the generation of turbulence inside the plenum 115 is reduced, while the compressor inlet is substantially radial and any collector orientation is also the same.

[0040] Preferably, the centrifugal compressor 100 includes one or more spacers arranged in the plenum 115 to avoid flow interference between the gas flows from the inlet 120, which flow interference is caused by the "collision" of the flows and their simultaneous counter-rotation inside the plenum 115, which may cause turbulence inside the plenum 115 and in the gas flowing to the impeller 130; in other words, due to the one or more spacers, a gradual merging (and mixing) between the gas flows from the inlet is desired and achieved. Specifically, the centrifugal compressor 100 includes two spacers 140a and 140b (see, for example Figure 3 ), which may be collectively referred to as 140, are located in the plenum 115 at two opposite sides relative to its circular axis of symmetry, which corresponds to (or substantially corresponds to) the axis of rotation "R." Specifically, two septa 140a and 140b are arranged to divide the plenum 115 into two symmetrical and substantially separate volumes.

[0041] According to the embodiment of the drawings, there are proximal septum 140a and distal septum 140b. Proximal septum 140a is located in the proximal half of the inflation chamber 115 ( Figure 3 The distal septum 140b is located in the distal half of the inflatable chamber 115 ( Figure 3140a). The lower half of the plenum chamber 115 in FIG. 140 is preferably located relative to the proximal septum 140a relative to its circular axis of symmetry, which corresponds to (or substantially corresponds to) the axis of rotation "R".

[0042] Preferably, the spacers 140 have a substantially planar geometry and are arranged in the plenum 115 on a meridional plane of the centrifugal compressor 100. Specifically, on a vertical meridional plane "M" according to the operating configuration of the centrifugal compressor 100.

[0043] According to the embodiment of the drawings, each septum 140 extends from a first end 141 located at the outer wall 116 to a second end 142 located at least partially at the inner wall 117, and completely occupies the longitudinal cross-section of the inflatable chamber 115 (especially the longitudinal cross-section of the rear portion of the inflatable chamber 115), as shown in FIG. Figure 3 Specifically, the second end portion 142 has a connection portion 143 connected to the inner wall 117 (in the rear portion of the plenum 115) and a free portion 144 located at the outlet 118 (in the front portion of the plenum 115), so that the process gas in the plenum 115 first flows on the opposite side of the distal septum 140b, and then preferably merges (and mixes) on the opposite side of the proximal septum 140a, downstream of the plenum 115, specifically in the connecting channel 125.

[0044] According to another aspect, the subject matter disclosed herein relates to a compressor system, which is not shown in the accompanying drawings.

[0045] The compressor system includes a centrifugal compressor, such as a centrifugal compressor similar or identical to compressor 100 described above, and at least two suction ducts, each suction duct being fluidly coupled to a respective inlet of the centrifugal compressor and arranged to deliver a process gas stream to an impeller of the compressor through the inlet and a plenum.

[0046] The collector can be integrated into the compressor. The suction duct can be integrated into the compressor or, more commonly, can be external to the compressor and, for example, a component supporting the slide of a centrifugal compressor; these suction ducts are connected to the flange of the collector. It should be noted that the slide can include other ducts and / or other machinery.

[0047] Each suction duct preferably has a straight portion immediately upstream of the collector, and each straight portion extends longitudinally over a length, for example, between about 2.5 times and about 6 times the diameter of the collector inlet, or longer. According to an advantageous application, the suction duct is arranged substantially vertically relative to the operating configuration of the compressor system and substantially perpendicular to the axis of rotation of the compressor. Specifically, in order to reduce the amount of space occupied by the suction duct, each straight portion can be limited to the above-mentioned range, and preferably, each suction duct is completely straight and has a length corresponding to the length of the straight portion. In addition, the straight portions of the suction duct are parallel to each other.

[0048] According to another aspect, the subject matter disclosed herein relates to a method of operating a centrifugal compressor, such as a centrifugal compressor similar or identical to compressor 100 described above; such a method can be implemented in a gas processing plant.

[0049] The embodiment of the method corresponds to Figure 5 Flowchart 200 in FIG. 1 includes a set of consecutive steps numbered from 210 to 270 .

[0050] The method includes an initial step 210 of generating a process gas stream, for example, a process gas stream to be compressed by an impeller of a centrifugal compressor similar to or the same as the impeller 130 of the compressor 100 .

[0051] Following step 210 is step 220 of separating the process gas stream into, for example, a first process gas stream and a second process gas stream.

[0052] Following step 220, step 230 is performed to advance the first and second process gas streams along separate, preferably substantially linear, paths (preferably parallel to one another) to reduce or eliminate flow non-uniformities in the first and second process gas streams. Preferably, the length of each linear path is, for example, between about 2.5 and about 6.0 times the collector inlet diameter. Preferably, these linear paths do not extend beyond a desired length to minimize space requirements.

[0053] Following step 230 is step 240 of flowing the first process gas and the second process gas into a plenum (eg, plenum 115).

[0054] Following step 240 is step 250 of keeping the two process gas streams separated inside the plenum 115 , in particular by means of spacers, such as spacers 140 a and 140 b .

[0055] Following step 250 is step 260: combining the first process gas flow and the second process gas flow to produce the desired suction process gas flow that is "optimized" from the perspective of, for example, the impeller that is to compress it. In compressor 100, this occurs at the outlet of the plenum, specifically before and after the outlet, for example in a connecting channel (such as channel 125).

[0056] Following step 260 is a final step 270 of feeding the “optimized” process gas stream into an impeller (such as 130 ) of a centrifugal compressor.

Claims

1. A centrifugal compressor (100), comprising: - a housing (110) having a first inlet and a second inlet, the housing forming a plenum having an outlet spaced from the first inlet and the second inlet; - a shaft disposed in the plenum chamber; an impeller (130) coupled to the shaft and located inside the housing (110) downstream of the plenum, the impeller being arranged to increase the pressure of the process gas as it flows through the impeller (130); as well as - a first diaphragm and a second diaphragm arranged in the inflation chamber, the first diaphragm and the second diaphragm having a body extending from a first end connected to the housing toward the shaft into the inflation chamber, the body terminating in a second end, the second end having a first portion connected to the inner wall of the housing and a second portion arranged in the outlet.

2. The centrifugal compressor (100) according to claim 1, Wherein the first inlet and the second inlet have substantially equal cross-sectional areas.

3. The centrifugal compressor (100) according to claim 1, wherein the shaft rotates on an axis of rotation (R), wherein the centrifugal compressor (100) has a longitudinal plane (M) arranged vertically relative to the working configuration of the centrifugal compressor and containing the axis of rotation (R), and The first inlet and the second inlet are arranged on both sides of the longitudinal plane (M).

4. The centrifugal compressor (100) according to claim 1, wherein the plenum (115) has a cylindrical shape, a frustoconical shape or an annular shape, and The first inlet and the second inlet are located on the side surface of the inflation chamber (115).

5. The centrifugal compressor (100) according to claim 3, The first separator and the second separator are arranged on the longitudinal plane (M).

6. The centrifugal compressor (100) according to claim 1, The first septum (140a) is close to the first inlet and the second inlet, and the second septum (140b) is far away from the first inlet and the second inlet.

7. The centrifugal compressor (100) according to claim 1, wherein the housing has a radially outer wall (116) and a radially inner wall (117) facing the radially outer wall (116) and close to the shaft, wherein the radially outer wall and the radially inner wall define the plenum chamber, and The outlet (118) of the plenum chamber faces the radially outer wall (116) and the first inlet and the second inlet, and is adjacent to the radially inner wall (117).

8. The centrifugal compressor (100) according to claim 1, The housing forms a shaped connecting channel (125) which terminates at one end at the outlet to the plenum chamber.

9. The centrifugal compressor (100) according to claim 1, further comprising: - Two collectors (121) protruding from said housing (110), each collector (121) comprising: - a collector inlet (122) arranged to be fluidically coupled to a suction conduit, and - a collector outlet (123) fluidly coupled to the inlet (120), wherein the two collectors are configured to reduce or eliminate non-uniformities in the flow of process gas from the collector inlet (122) to the collector outlet (123).

10. The centrifugal compressor (100) according to claim 9, Each collector (121) defines a diverging duct diverging from the collector inlet (122) to the collector outlet (123).

11. The centrifugal compressor (100) according to claim 9, The distance between the collector inlet (122) and the collector outlet (123) is between 1 and 3 times the diameter of the collector inlet (122).

12. The centrifugal compressor (100) according to claim 9, wherein the two collectors (121) include end portions adjacent to the collector outlets (123), wherein the end portions extend longitudinally along respective straight lines, and The straight lines form an angle (α) in the range of 15° to 30°.

13. The centrifugal compressor (100) according to claim 1, The first end of the first septum is between the first inlet and the second inlet.

14. The centrifugal compressor (100) according to claim 1, The first diaphragm and the second diaphragm are located on opposite sides of the plenum.

15. The centrifugal compressor (100) according to claim 9, wherein an area ratio of the collector inlet cross section to the collector outlet cross section is between 1.0 and 1.

3.

16. A compressor system comprising: A centrifugal compressor (100) according to any one of the preceding claims 1 to 15.

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