High-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor

Abstract

The invention provides a high-speed direct-driven double-cantilever multi-stage cylindrical centrifugal compressor, and relates to the technical field of centrifugal compressors, the compressor is directly driven by a high-speed motor, and multi-stage impellers are serially connected on two sides of a driving spindle in a double-cantilever manner to form a first compression section and a second compression section which are serially connected to work; unification of a high pressure ratio and an extremely compact structure is realized, a transient protection device integrated at the tail end of a stay bolt is provided aiming at specific transient safety risks of the long cantilever rotor, a bearing mounting part of the stay bolt is in clearance fit with an auxiliary bearing, and the stay bolt is kept in non-contact with a rotating part when the compressor operates stably, so that the safety of the compressor is ensured. Unnecessary friction and loss are avoided, the auxiliary bearing can be in contact with the stay bolt before any static runner component only when transient overlarge deflection of the rotor occurs, so that effective mechanical limiting is provided, and collision and abrasion of dynamic and static parts are prevented.

Description

Technical Field

[0001] This invention relates to the field of centrifugal compressor technology, and in particular to a high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor. Background Technology

[0002] With rising global energy costs, industrial users are becoming significantly more sensitive to energy consumption. The overall efficiency of an energy storage system, especially its charge-discharge cycle efficiency, directly determines its economic viability, and the compressor efficiency is key to the energy consumption during the "charging" process. In supercritical carbon dioxide energy storage systems, the compressor, as the core energy-consuming device, is of paramount importance.

[0003] Traditional compressor units, such as single-shaft multistage centrifugal compressors or integral gear compressors, are typically assembled from separate compressor units, gearboxes, and drive units (such as motors). This structure has the following inherent drawbacks: First, the energy transmission path is long, and the gearbox itself causes 2%-3% energy loss; second, the equipment is bulky, requiring complex foundations and alignment adjustments, resulting in a large footprint and high initial installation costs; third, the internal components, including gears, multiple support bearings, and a complex lubrication system, are major sources of failure, leading to high maintenance workload and costs, and requiring extensive disassembly and prolonged downtime for maintenance; finally, the efficiency of traditional compressors drops sharply when operating outside of their design conditions (partial load), making it difficult to flexibly adapt to the changing operating conditions of energy storage systems, resulting in significant power waste.

[0004] Despite advancements in related technologies such as high-performance permanent magnets, high-speed motor design, high-frequency inverters, advanced bearings, and digital design / feedback engineering (CFD / FEA), these technologies have not yet been systematically integrated to address the comprehensive challenges of using these compressors in energy storage applications. Existing solutions fail to effectively balance high efficiency, high reliability, compact structure, low maintenance costs, and rapid response to varying operating conditions.

[0005] However, the unique compact architecture of the 'long cantilever rotor combined with tie rod bolt series impeller' designed to achieve the above-mentioned goals of high efficiency and compactness also brings new technical challenges: during transient processes such as high-speed start-up and shutdown and over-critical speed, the farthest end of the rotor (i.e., the end of the tie rod bolt) may experience significant instantaneous deflection, posing a risk of rubbing against stationary components. Finding a dedicated protection scheme for this novel architecture that does not affect its core advantages of compactness, high efficiency, and oil-free operation while ensuring safe transient operation has become a technical challenge that must be overcome to realize the concept of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor that solves the problem of instantaneous deflection at the farthest end of the rotor, which poses a risk of collision and friction with stationary parts.

[0007] To achieve the above objectives, the present invention provides a high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor, comprising a high-speed motor, a first compression section, and a second compression section. The high-speed motor has symmetrically arranged pressure-bearing housings on both sides. Two cantilever ends on the drive shaft of the high-speed motor extend into the two pressure-bearing housings respectively. The first compression section and the second compression section are respectively arranged on the two cantilever ends of the drive shaft. Each of the first and second compression sections has multi-stage centrifugal impellers connected in series on its corresponding cantilever ends. The outlet of the first compression section is connected to the inlet of the second compression section. Transient protection devices are installed on both cantilever ends, and the transient protection devices include: A tie rod bolt, one end of which is fixedly connected to the drive spindle, and the other end of which protrudes from the outermost impeller and is provided with a bearing mounting part; An auxiliary bearing is fitted onto the bearing mounting portion with a clearance fit. A bearing housing is fixedly installed on a stationary partition on the inlet side of the compressor, and the outer ring of the auxiliary bearing is fitted onto the bearing housing.

[0008] Furthermore, the outlet of the first compression section is connected to the inlet of the second compression section via a connecting pipeline.

[0009] Furthermore, three centrifugal impellers are connected in series on each of the two cantilever ends via the tie rod bolts.

[0010] Furthermore, the pressure-bearing shell has a cylindrical structure.

[0011] Furthermore, the pressure-bearing housing includes an outer volute, an inner volute, and a compression inlet section connected in sequence by bolts. The outer volute is bolted to the motor housing of the high-speed motor. Inside the pressure-bearing housing, a bearing seat, a first-stage partition, a second-stage partition, and a third-stage partition are installed in sequence along the air intake direction. The bearing seat is bolted to the first-stage partition. The first-stage partition and the second-stage partition are bolted to the inner volute. The third-stage partition is bolted to the outer volute.

[0012] Furthermore, the outer volute is mounted on the drive spindle via a dry gas sealing structure.

[0013] Furthermore, the auxiliary bearing is a hybrid ceramic ball bearing, and the rolling elements of the auxiliary bearing are made of silicon nitride ceramic.

[0014] Furthermore, the high-speed motor is a permanent magnet synchronous motor.

[0015] Furthermore, the drive spindle is rotatably connected to the motor housing of the high-speed motor via a main support bearing.

[0016] Furthermore, the compression outlets on the first compression section and the second compression section are respectively integrated on the two outer volutes.

[0017] The technical solution of this invention adopts a high-speed motor direct drive, and sets up multiple impellers in series in a double cantilever configuration on both sides of the drive shaft to form a first compression section and a second compression section working in series. This achieves a balance between high pressure ratio and an extremely compact structure. In response to the transient safety risks unique to this long cantilever rotor, an innovative transient protection device integrated into the end of the tie rod bolt is proposed. The bearing mounting part of the tie rod bolt is clearance-fitted with the auxiliary bearing. During the steady-state operation of the compressor, it remains non-contact with the rotating parts, avoiding unnecessary friction and wear. Only when the rotor experiences excessive transient deflection can the auxiliary bearing contact the tie rod bolt before any stationary flow channel component, thereby providing effective mechanical restraint and preventing friction between moving and stationary parts. This solution systematically solves the drawbacks of traditional compressors, such as low energy efficiency, large size, and complicated maintenance, and provides a complete, reliable, and implementable high-performance SCO2 compression solution. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a cross-sectional view of the overall structure of the present invention.

[0020] Figure 2 This is a cross-sectional view of the first compression section.

[0021] Figure 3 for Figure 2 Enlarged view of the structure indicated by point A in the middle.

[0022] Explanation of reference numerals in the attached drawings: 1-First compression section, 101-First outer volute, 102-Inner volute, 103-Compression inlet section, 104-First stage diaphragm, 105-Tie rod bolt, 106-First stage impeller, 107-Second stage impeller, 108-Third stage impeller, 109-Second stage diaphragm, 110-Third stage diaphragm, 111-Dry gas seal, 112-Auxiliary bearing, 113-Bearing housing, 114-Drive main shaft, 115-Main support bearing, 2-Second compression section, 201-Second outer volute, 202-Fourth stage impeller, 203-Fifth stage impeller, 204-Sixth stage impeller, 205-Motor housing. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] like Figures 1-3 As shown, the present invention provides a high-speed direct-drive double cantilever multi-stage cylindrical centrifugal compressor configured for compressing supercritical carbon dioxide working fluid, including a high-speed motor, a first compression stage 1 and a second compression stage 2. The high-speed motor is a permanent magnet synchronous motor (its stator and rotor are integrated in the motor housing 205 and directly drive the main shaft 114). The drive spindle 114 is rotatably connected to the motor housing 205 of the high-speed motor via the main support bearing 115, that is, between the stator and rotor of the high-speed motor. Two main support bearings 115 are symmetrically arranged on both sides of the drive spindle 114. The two main support bearings 115 are the core load-bearing components of the rotor system, responsible for bearing the radial load and part of the circumferential load of the rotor under all operating conditions, ensuring the stable high-speed rotation of the rotor.

[0027] The high-speed motor has symmetrical pressure-bearing housings on both sides. The pressure-bearing housings are cylindrical structures. The two cantilever ends on the drive shaft 114 of the high-speed motor extend into the two pressure-bearing housings respectively. The pressure-bearing housings include an outer volute, an inner volute 102 and a compression inlet section 103 connected in sequence by bolts. The compression outlet is integrated on the outer volute. The outer volute is mounted on the drive shaft 114 by a dry gas seal 111 structure. The dry gas seal 111 structure is existing technology and will not be described in detail here. The outer volute is mounted on the motor housing 205 of the high-speed motor by bolts. Inside the pressure-bearing housings, along the air intake direction, a bearing seat 113, a first-stage partition 104, a second-stage partition 109 and a third-stage partition 110 are installed in sequence. The bearing seat 113 is fixedly mounted on the first-stage partition 104 by bolts. The first-stage partition 104 and the second-stage partition 109 are fixedly mounted on the inner volute 102 by long bolts. The third-stage partition 110 is mounted on the outer volute by bolts.

[0028] The first compression section 1 and the second compression section 2 are respectively arranged on the two cantilever ends of the drive main shaft 114. The outlet of the first compression section 1 is connected to the inlet of the second compression section 2 through a connecting pipe. The first compression section 1 and the second compression section 2 are each equipped with a three-stage centrifugal impeller in series on their respective cantilever ends by tie rod bolts 105.

[0029] Transient protection devices are installed on both cantilever ends. These devices are additional safety devices independent of the main support bearing 115 system, specifically designed to address the deflection risk of the double cantilever structure under extreme transient conditions. The two main support bearings 115 constitute the core load-bearing system of the rotor system, and their design employs a small working clearance (e.g., radial diameter clearance approximately 0.1%-0.15% of the journal diameter) to ensure extremely high rotational accuracy and stability of the rotor under all steady-state operating conditions. The auxiliary bearing 112 in the rotor end transient protection device is an independent safety limiting system. The radial diameter clearance between it and the bearing housing 113 is set to be significantly larger than the working clearance of the main support bearing 115 (e.g., approximately 2-3 times the latter). The clearance value was determined through rotor dynamics analysis. Its lower limit ensures that the auxiliary bearing 112 and the tie rod bolt 105 remain non-contact throughout the compressor's steady-state and normal transient processes (such as start-up and shutdown), avoiding unnecessary friction and wear. Its upper limit ensures that in the event of extreme over-deflection, the auxiliary bearing 112 can contact the rotor before any stationary flow path component, thereby providing effective mechanical restraint and preventing rubbing between moving and stationary parts. The auxiliary bearing 112 has an internal sealing structure to prevent lubricating oil mist from entering the medium. This division of labor design, with the main bearing providing precision load and the auxiliary bearing 112 providing large clearance protection, perfectly matches the dedicated function of transient protection while ensuring the long-term operational reliability of the double cantilever rotor.

[0030] The transient protection device includes a tie rod bolt 105, an auxiliary bearing 112, and a bearing housing 113. One end of the tie rod bolt 105 is fixedly connected to the drive shaft 114, and the other end of the tie rod bolt 105 protrudes from the outermost impeller and is provided with a bearing mounting part. The auxiliary bearing 112 is fitted onto the bearing mounting part with a clearance fit, and the outer ring of the auxiliary bearing 112 is fitted onto the bearing housing 113. The auxiliary bearing 112 and the dry gas seal 111 together constitute a compressed internal environment without liquid lubricating oil. The auxiliary bearing 112 is a hybrid ceramic ball bearing, and the rolling elements of the auxiliary bearing 112 are made of silicon nitride ceramic.

[0031] The assembly steps of a single compression section in the compressor, taking the first compression section 1 on the left as an example, employ the innovative method of this invention: 1. Fix the outer casing and the end stator: Connect and fix the outer volute to the left side of the motor housing 205, and install the dry gas seal 111 and the third-stage partition 110 (final stage partition) in sequence.

[0032] 2. Establish rotor reference: Install tie rod bolt 105 on the left end of drive spindle 114 and tighten it.

[0033] 3. Stator and rotor are installed alternately (installed against the airflow direction from the outlet end of the compression section to the inlet end): a. Assemble the third-stage impeller 108 (final stage impeller). b. Install the first inner volute 102. c. Assemble the second-stage impeller 107.

[0034] d. Install the second-stage baffle 109 (intermediate stage baffle). e. Install the first-stage impeller 106 (first-stage impeller) and tighten the entire impeller string with the lock nut.

[0035] 4. Complete the installation of the front stator and protection device: Install and fix the first-stage partition 104 (primary partition). Then, install the shaft end auxiliary bearing 112 at the end of the tie rod bolt 105 and fix the auxiliary bearing 112 to the first-stage partition 104.

[0036] 5. Close the inlet: Install the first compression inlet section 103.

[0037] The second compression segment 2 on the right is installed symmetrically with the same logic.

[0038] The compressor operates as a complete six-stage tandem compressor. The working path of the SCO2 working fluid to be compressed is as follows: For ease of distinction, the three impellers of the first compression section 1 are named sequentially along the airflow direction as first-stage impeller 106, second-stage impeller 107, and third-stage impeller 108; the three impellers of the second compression section 2 are named sequentially along the airflow direction as fourth-stage impeller 202, fifth-stage impeller 203, and sixth-stage impeller 204. The outer volute on the left is named first outer volute 101, and the outer volute on the right is named second outer volute 201.

[0039] The working fluid first enters the first compression section 1 on the left side through the compression inlet section 103. Within the first compression section 1, the working fluid flows sequentially through the first-stage impeller 106, the second-stage impeller 107, and the third-stage impeller 108, completing three stages of compression. The compressed gas is discharged from the compression outlet integrated into the first outer volute 101. This gas is then guided to the second compression section 2 through an external connecting pipeline. Within the second compression section 2, the working fluid continues to flow sequentially through the fourth-stage impeller 202, the fifth-stage impeller 203, and the sixth-stage impeller 204, completing the subsequent three stages of compression. Finally, the high-pressure SCO2 working fluid, after a total of six stages of compression, is discharged from the compression outlet integrated into the second outer volute 201.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor, characterized in that, The system includes a high-speed motor, a first compression section, and a second compression section. The high-speed motor has symmetrically arranged pressure-bearing housings on both sides. Two cantilever ends on the drive shaft of the high-speed motor extend into the two pressure-bearing housings. The first and second compression sections are respectively arranged on the two cantilever ends of the drive shaft. Each of the first and second compression sections has a multi-stage centrifugal impeller installed in series on its corresponding cantilever end. The outlet of the first compression section is connected to the inlet of the second compression section. A transient protection device is installed on each of the two cantilever ends. The transient protection device includes: A tie rod bolt, one end of which is fixedly connected to the drive spindle, and the other end of which protrudes from the outermost impeller and is provided with a bearing mounting part; An auxiliary bearing is fitted onto the bearing mounting portion with a clearance fit. A bearing housing is fixedly installed on a stationary partition on the inlet side of the compressor, and the outer ring of the auxiliary bearing is fitted onto the bearing housing.

2. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, The outlet of the first compression section is connected to the inlet of the second compression section via a connecting pipeline.

3. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, Three centrifugal impellers are mounted on each of the two cantilever ends via tie rod bolts.

4. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, The pressure-bearing shell has a cylindrical structure.

5. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 4, characterized in that, The pressure-bearing housing includes an outer volute, an inner volute, and a compression inlet section connected in sequence by bolts. The outer volute is bolted to the motor housing of the high-speed motor. Inside the pressure-bearing housing, along the air intake direction, a bearing seat, a first-stage partition, a second-stage partition, and a third-stage partition are installed in sequence. The bearing seat is bolted to the first-stage partition. The first-stage partition and the second-stage partition are bolted to the inner volute. The third-stage partition is bolted to the outer volute.

6. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 5, characterized in that, The outer volute is mounted on the drive spindle via a dry gas sealing structure.

7. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, The auxiliary bearing is a hybrid ceramic ball bearing, and the rolling elements of the auxiliary bearing are made of silicon nitride ceramic.

8. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, The high-speed motor is a permanent magnet synchronous motor.

9. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 1, characterized in that, The drive spindle is rotatably connected to the motor housing of the high-speed motor via a main support bearing.

10. The high-speed direct-drive double-cantilever multi-stage cylindrical centrifugal compressor according to claim 5, characterized in that, The compression outlets on the first compression section and the second compression section are respectively integrated on the two outer volutes.

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