A thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor

Abstract

This application provides a thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor. The thermal management structure includes an induced draft pre-cooling structure located downstream of the impeller hub back-side sealing structure, a motor chamber connected to the induced draft pre-cooling structure, and bearing cooling induced draft channels and return channels located on both sides of the motor rotor shaft. The induced draft pre-cooling structure, located downstream of the impeller hub back-side sealing structure, pre-cools the leakage flow before introducing it into the motor chamber, achieving efficient cooling of the motor rotor, stator windings, and bearings. Combined with the design of the bearing cooling induced draft channels and closed return channels, the cooling efficiency is further optimized and the working fluid loss is reduced. This solves the technical problems of poor cooling effect and significant working fluid loss in existing cooling methods for supercritical carbon dioxide centrifugal compressors, which result in poor cooling effect on internal motor windings, rotors, and bearings. It has advantages such as compact structure, excellent cooling effect, and high overall reliability.

Description

Technical Field

[0001] This invention relates to the field of centrifugal compressor technology, and specifically to a thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor. Background Technology

[0002] Supercritical carbon dioxide closed-loop cycle is a medium-temperature, high-pressure cycle with advantages such as compact structure and high efficiency. It can be widely used in energy conversion fields, such as nuclear and solar power generation, and waste heat utilization of gas turbines and internal combustion engines. The supercritical carbon dioxide centrifugal compressor is the core component in the closed-loop cycle.

[0003] In small-scale supercritical carbon dioxide closed-cycle power generation systems, a fully enclosed layout is generally adopted to reduce leakage losses from the dynamic seal between the centrifugal compressor impeller and the motor. The centrifugal compressor impeller and the motor are arranged coaxially in the same enclosed space. The motor rotor, stator, and bearings operate in a supercritical carbon dioxide environment. A large amount of heat is generated during the operation of the motor driving the compressor. Thermal management is required to ensure that the motor stator, rotor, and bearings do not overheat.

[0004] Currently, cooling water channels are typically installed on the motor housing to cool the motor. However, this only addresses the cooling of the motor stator core and has limited effectiveness in cooling the motor rotor, stator windings, and bearings. Because the compressor and motor are fully enclosed, lubricating oil cannot be introduced to cool the motor bearings, which can easily lead to bearing overheating and failure.

[0005] Supercritical carbon dioxide centrifugal compressors often operate near the critical point. Because the critical point temperature of carbon dioxide is low, the temperature of supercritical carbon dioxide in the compressor is also low. In addition, supercritical carbon dioxide has high density and low viscosity, and good flow and heat transfer performance, so it can be used as a heat transfer medium for compressor thermal management.

[0006] Therefore, researchers in this field urgently need to develop a thermal management structure and cooling method for supercritical carbon dioxide centrifugal compressors with better cooling performance. Summary of the Invention

[0007] In view of this, for the thermal management of a fully enclosed supercritical carbon dioxide centrifugal compressor, this invention provides a thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor. By setting an air pre-cooling structure downstream of the impeller hub back sealing structure, the leakage flow is pre-cooled before being introduced into the motor chamber, achieving efficient cooling of the motor rotor, stator windings, and bearings. Through the design of the bearing cooling air duct and closed return channel, the cooling efficiency is further optimized and the working fluid loss is reduced, solving the technical problems of poor cooling effect and large working fluid loss in the existing cooling methods of supercritical carbon dioxide centrifugal compressors.

[0008] To achieve the above objectives, one embodiment of the present invention provides a thermal management structure for a supercritical carbon dioxide centrifugal compressor. This thermal management structure includes: a pre-cooling structure for bleed air, a motor chamber, a bearing cooling bleed air passage, and a return flow passage. The pre-cooling structure for bleed air is located downstream of the impeller hub back-side sealing structure and is used to pre-cool the impeller leakage flow. The motor chamber is connected to the pre-cooling structure for bleed air, introducing the pre-cooled leakage flow into the motor chamber to directly cool the motor rotor, stator windings, and bearings. The bearing cooling bleed air passage is located at the bearing mounting positions on both sides of the motor rotor shaft, guiding a portion of the cooled leakage flow to cool the bearings. The return flow passage is used to guide the leakage flow after cooling the motor and bearings back to the compressor inlet passage.

[0009] Furthermore, the bleed air precooling structure includes a leak flow water-cooled channel for precooling the impeller leak flow and a sealing grate for isolating the uncooled leak flow.

[0010] Furthermore, the sealing grates are multi-stage labyrinth seals or air film seals.

[0011] Furthermore, the outer periphery of the motor chamber is provided with a water-cooled flow channel, which is connected in parallel or in series with the leakage flow water-cooled flow channel in the air pre-cooling structure.

[0012] Furthermore, the pre-cooling structure includes an air duct, a main cooling channel flowing into the motor chamber, and an auxiliary cooling channel flowing into the bearing cooling air duct. After the leakage flow flows into the air duct for cooling, a portion of the cooling leakage flow enters the motor chamber through the main cooling channel to contact-cool the motor rotor and stator windings, carrying away the heat generated by wind friction loss at the air gap between the motor rotor and stator. The other portion of the cooling leakage flow enters the bearing cooling air duct to contact-cool the bearing.

[0013] Furthermore, the cooling leakage flow rate of the bearing cooling airflow channel is adjusted according to the heat generated by the bearing.

[0014] Furthermore, the inlet of the return channel is connected to the leakage outlet channel of the motor rear cover plate, and the outlet is connected to the compressor inlet channel.

[0015] Furthermore, a one-way valve is provided at the inlet of the reflux channel to prevent backflow of the working fluid.

[0016] Furthermore, a reflux cooling structure is provided on the reflux channel.

[0017] Another embodiment of the present invention provides a cooling method for the thermal management structure of a supercritical carbon dioxide centrifugal compressor, comprising the following steps:

[0018] The impeller leakage flow is pre-cooled by the induced draft pre-cooling structure and then introduced into the motor chamber to directly contact and cool the motor rotor, stator windings and bearings.

[0019] The bearing is directionally cooled by distributing the leakage flow after partial cooling through the bearing cooling airflow channel;

[0020] The leakage flow after cooling the motor and bearings flows back to the inlet channel of the supercritical carbon dioxide centrifugal compressor through the return channel, forming the motor cooling circuit of the supercritical carbon dioxide centrifugal compressor.

[0021] The beneficial effects of this invention are:

[0022] This invention provides a thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor. It is a thermal management structure and method that comprehensively utilizes the impeller leakage flow and pre-cooling of the leakage flow. Specifically, by setting an air induced pre-cooling structure downstream of the impeller hub back-side sealing structure, the leakage flow is pre-cooled before being introduced into the motor chamber, achieving efficient cooling of the motor rotor, stator windings, and bearings. Combined with the design of a bearing cooling induced flow channel and a closed return channel, the cooling efficiency is further optimized and the working fluid loss is reduced. This solves the technical problems of poor cooling effect and significant working fluid loss in existing centrifugal compressor cooling methods, which suffer from poor cooling effect on internal motor windings, rotors, and bearings. This invention is applicable to fully enclosed supercritical carbon dioxide circulation systems and has the advantages of compact structure, excellent cooling effect, and high overall reliability. Attached Figure Description

[0023] The following figures are provided to further illustrate this application and form part of this application. They are intended to be illustrative and explanatory only, and are not intended to limit the scope of the invention. In the figures:

[0024] Figure 1 This is a schematic diagram of the thermal management structure of a supercritical carbon dioxide centrifugal compressor according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the supercritical carbon dioxide flow path structure of the present invention;

[0026] Figure 3 This is a flowchart of the cooling method for the thermal management structure of the supercritical carbon dioxide centrifugal compressor of the present invention.

[0027] Figure label:

[0028] 1-Compressor inlet channel; 2-Impeller front cover plate; 3-Blade; 4-Impeller hub; 5-Impeller hub back sealing structure; 6-Exhaust air pre-cooling structure; 7-Exhaust air channel; 71-Main cooling channel; 72-Auxiliary cooling channel; 8-Leakage water cooling channel; 9-Sealing grate; 10-Left bearing; 11-Left bearing cooling exhaust air channel; 12-Motor rotor; 13-Stator winding; 14-Casing water cooling channel; 15-Motor casing; 16-Right bearing; 17-Right bearing cooling exhaust air channel; 18-Motor rear cover plate; 19-Return channel; 191-One-way valve; 192-Return cooling structure; 20-Motor chamber. Detailed Implementation

[0029] The following illustrations will disclose several embodiments of this application, providing a clear and complete description of the technical solution of the present invention. The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] The technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of a person skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0032] The following are examples of specific implementation processes provided to illustrate the technical solutions to be protected in this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can implement this application by different technical means under the guidance of the concept of this application. Therefore, this application is not limited to the specific embodiments below.

[0033] Example 1

[0034] like Figure 1 , Figure 2As shown, the thermal management structure of the supercritical carbon dioxide centrifugal compressor of this invention includes the following core components: a pre-cooling structure 6, a motor chamber 20, a bearing cooling duct 7, and a return channel 19. The pre-cooling structure 6 is arranged downstream of the impeller hub back-side sealing structure 5 and is used to pre-cool the impeller leakage flow. The motor chamber 20 is connected to the pre-cooling structure 6, and the pre-cooled leakage flow is introduced into the motor chamber 20 to directly cool the motor rotor 12, stator winding 13, and bearings. The bearing cooling duct is located at the bearing mounting positions on both sides of the motor rotor shaft, namely, the left bearing cooling duct 11 corresponding to the left bearing 10 and the right bearing cooling duct 17 corresponding to the right bearing 16, guiding part of the cooled leakage flow to cool the left bearing 10 and the right bearing 16. The return channel 19 is used to guide the leakage flow after cooling the motor and bearings back to the compressor inlet channel 1.

[0035] exist Figure 1 , Figure 2 In the above, the induced draft pre-cooling structure 6 includes a leakage flow water-cooled channel 8 for pre-cooling the impeller leakage flow and a sealing grate 9 for isolating the uncooled leakage flow. Further, the induced draft pre-cooling structure 6 has an induced draft flow channel 7, a main cooling flow channel 71 flowing into the motor chamber, and an auxiliary cooling flow channel 72 flowing into the bearing cooling induced draft flow channel 11. After the leakage flow flows into the induced draft flow channel 7 for cooling, a portion of the cooled leakage flow enters the motor chamber 20 through the main cooling flow channel 71 to contact-cool the motor rotor 12 and stator winding 13, carrying away the heat generated by wind friction loss at the air gap between the motor rotor and stator. The other portion of the cooled leakage flow enters the bearing cooling induced draft flow channel 11 to contact-cool the bearing.

[0036] Combination Figure 1 , Figure 2 As shown, the working principle of the technical solution applied in this embodiment is as follows: supercritical carbon dioxide enters the impeller channel from the compressor inlet channel 1, and after being compressed by the high-speed rotating blades 3, it is divided into the main stream and the leakage stream. The main stream enters the subsequent components such as the diffuser, volute, and return flow device. Part of the leakage stream enters the leakage channel on the back side 4 of the impeller hub, and enters the induced draft pre-cooling structure 6 through the sealing structure 5 on the back side of the impeller hub. In the induced draft pre-cooling structure 6, the leakage stream is pre-cooled through the induced draft channel 7 and the leakage stream water-cooled channel 8. The leakage stream water-cooled channel 8 is connected to an external cooling water source, and the temperature of the leakage stream is reduced to a preset range through heat exchange.

[0037] The sealing grates 9 prevent uncooled leakage flow from entering the motor chamber. After pre-cooling in the leakage flow water-cooling channel 8 along the airflow channel 7, the cooled leakage flow is divided into two paths under the guidance of the main cooling channel 71 and the auxiliary cooling channel 72: one path is the main cooling flow along the main cooling channel 71, which enters the motor chamber and directly cools the motor stator, rotor and air gap area, carrying away the heat generated by wind friction loss; the other path is the bearing cooling flow along the auxiliary cooling channel 72: it flows through the left and right bearing cooling airflow channels 11 and 17 to the left bearing 10 and the right bearing 16 respectively, and after directional cooling of the bearings, it merges with the main cooling flow. Then, it flows into the return channel 19 through the leakage flow outlet opened on the motor rear cover plate 18 and returns to the compressor inlet channel 1, forming a closed loop, optimizing cooling efficiency and reducing working fluid loss.

[0038] In a preferred embodiment, the pre-cooling structure for induced draft is further provided with an auxiliary cooling channel, which is filled with a paraffin-based phase change material or a metal-based composite material (such as an aluminum-graphite composite). When the leakage flow temperature rises sharply (such as during instantaneous operation), the phase change material can quickly absorb the heat of the leakage flow and liquefy, thus having a high transient heat dissipation capacity. Combined with the water-cooled leakage flow channel, the pre-cooling effect of the leakage flow can be further guaranteed, thereby further ensuring a better cooling effect for the motor rotor, stator windings, and bearings.

[0039] It should be noted that the coolant in the leakage flow cooling channel of this embodiment is preferably, but not limited to, cooling water. It can also be other cooling liquids, such as ethylene glycol solution suitable for low-temperature environments, depending on the actual situation. Its setting position is preferably, but not limited to, on the side of the air pre-cooling structure 6 near the main cooling channel 71, as long as it can play the role of cooling the leakage flow.

[0040] Furthermore, the sealing grates 9 are multi-stage labyrinth seals or air film seals, and V-shaped guide grooves are provided between adjacent grates to guide uncooled leakage flow back, preventing it from entering the motor chamber and enhancing the isolation effect on uncooled leakage flow.

[0041] In a preferred embodiment, a housing water-cooling channel is provided on the outer periphery of the motor chamber, i.e., on the motor housing. This channel is connected in parallel or in series with the leakage flow water-cooling channel 8 in the induced draft pre-cooling structure. By adjusting the cooling water flow rate and temperature, the leakage flow pre-cooling effect can be further controlled to adapt to different operating conditions. Specifically, the housing water-cooling channel and the leakage flow water-cooling channel 8 can be connected via a three-way valve, supporting switching between series and parallel modes to adapt to different operating conditions.

[0042] Furthermore, the cooling leakage flow rate of the bearing cooling airflow channel is adjusted according to the heat generated by the bearing. Specifically, the bearing cooling flow rate is adjusted by changing the cross-sectional area of ​​the auxiliary cooling channel 72, thereby adjusting the cooling leakage flow rate of the bearing cooling airflow channel. For example, when the bearing temperature exceeds a threshold, the cross-sectional area of ​​the auxiliary cooling channel is increased to improve the bearing cooling effect.

[0043] exist Figure 1 , Figure 2 In the process, the inlet of the return channel 19 is connected to the leakage outlet channel of the motor rear cover plate 18, and the outlet is connected to the compressor inlet channel 1.

[0044] Furthermore, such as Figure 2 As shown, a one-way valve 191 is provided at the inlet of the reflux channel 19 to prevent backflow of the working fluid. Furthermore, a reflux cooling structure 192 is provided on the reflux channel 19 to enhance the overall thermal management effect of the equipment.

[0045] Example 2

[0046] like Figure 3 As shown, the cooling method of the supercritical carbon dioxide centrifugal compressor thermal management structure in Embodiment 1 of the present invention specifically includes the following steps:

[0047] Step 1: After the impeller leakage flow is pre-cooled by the induced draft pre-cooling structure, it is introduced into the motor chamber to directly contact and cool the motor rotor, stator windings and bearings.

[0048] Step 2: Distribute a portion of the cooled leakage flow through the bearing cooling airflow channel to perform directional cooling on the bearing;

[0049] Step 3: The leakage flow after cooling the motor and bearings flows back to the inlet flow channel of the supercritical carbon dioxide centrifugal compressor through the return channel, forming the motor cooling circuit of the supercritical carbon dioxide centrifugal compressor.

[0050] In summary, the thermal management structure and cooling method for a supercritical carbon dioxide centrifugal compressor provided by this invention is a thermal management structure and method that comprehensively utilizes the impeller leakage flow and pre-cooling of the leakage flow. Specifically, by setting an air induced pre-cooling structure downstream of the impeller hub back-side sealing structure, the leakage flow is pre-cooled before being introduced into the motor chamber, achieving efficient cooling of the motor rotor, stator windings, and bearings. Combined with the bearing cooling air induced flow channel and closed return channel design, the cooling efficiency is further optimized and the working fluid loss is reduced, resulting in advantages such as compact structure, uniform cooling, and high reliability.

[0051] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0052] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0053] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A thermal management structure for a supercritical carbon dioxide centrifugal compressor, characterized in that, include: Exhaust pre-cooling structure: Located downstream of the impeller hub back sealing structure, it is used to pre-cool the impeller leakage flow; The exhaust precooling structure includes a leak flow water-cooled channel for precooling the impeller leak flow and sealing grates for isolating the uncooled leak flow. Motor chamber: It is connected to the air pre-cooling structure and introduces the pre-cooled leakage flow into the motor chamber to directly cool the motor rotor, stator windings and bearings; Bearing cooling airflow channels: These are located at the bearing mounting positions on both sides of the motor rotor shaft to guide some of the leakage flow after cooling to provide directional cooling for the bearings; Return channel: Used to guide the leakage flow after cooling the motor and bearings back to the compressor inlet channel.

2. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, The sealing grates are multi-stage labyrinth seals or air film seals.

3. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, The outer periphery of the motor chamber is provided with a shell water-cooling channel, which is connected in parallel or in series with the leakage water-cooling channel in the air pre-cooling structure.

4. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, The pre-cooling structure includes an air intake channel, a main cooling channel flowing into the motor chamber, and an auxiliary cooling channel flowing into the bearing cooling air intake channel. After the leakage flow flows into the air intake channel for cooling, a portion of the cooling leakage flow enters the motor chamber through the main cooling channel to perform contact cooling on the motor rotor and stator windings, carrying away the heat generated by wind friction loss at the air gap between the motor rotor and stator. The other portion of the cooling leakage flow enters the bearing cooling air intake channel to perform directional cooling on the bearing.

5. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, The cooling leakage flow rate of the bearing cooling airflow channel is adjusted according to the heat generated by the bearing.

6. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, The inlet of the return channel is connected to the leakage outlet of the motor rear cover plate, and the outlet is connected to the compressor inlet channel.

7. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, A one-way valve is installed at the inlet of the reflux channel to prevent backflow of the working fluid.

8. The thermal management structure of the supercritical carbon dioxide centrifugal compressor as described in claim 1, characterized in that, A reflux cooling structure is provided on the reflux channel.

9. A cooling method based on the thermal management structure according to any one of claims 1-8, characterized in that, Includes the following steps: The impeller leakage flow is pre-cooled by the induced draft pre-cooling structure and then introduced into the motor chamber to directly contact and cool the motor rotor, stator windings and bearings. The bearing is cooled by distributing the leakage flow after partial cooling through the bearing cooling airflow channel; The leakage flow after cooling the motor and bearings flows back to the inlet channel of the supercritical carbon dioxide centrifugal compressor through the return channel, forming the motor cooling circuit of the supercritical carbon dioxide centrifugal compressor.

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