Centrifugal compressor with built-in PCHE and tubular heat exchanger

Abstract

The invention provides a centrifugal compressor with built-in PCHE and a tubular heat exchanger, belongs to the technical field of compressor heat exchanger structures, and can at least partially solve the problem that circulating cooling water possibly works in a laminar flow area due to the fact that the cold side through-flow area of an existing printed circuit board type heat exchanger of a reverse flow structure or a direct flow structure is too large. The compressor comprises a shell, a rotor assembly, a stator assembly, a volute chamber and a tubular heat exchanger are arranged in the shell, the tubular heat exchanger is arranged between compression stages to cool gas in a segmented mode, the specific work needed by the next stage is reduced, the power consumption of the compressor is reduced, the full-cycle heat efficiency is improved, and the stable operation range is expanded; the diffusion type PCHE adopts small-angle straight wall diffusion, kinetic energy is gently converted into static pressure, separation is restrained, and high static pressure recovery and low total pressure loss are kept in a quasi-critical zone with the thermal capacity changing drastically.

Description

Technical Field

[0001] This invention belongs to the technical field of compressor heat exchanger structure, specifically relating to a centrifugal compressor with a built-in PCHE and tubular heat exchanger. Background Technology

[0002] Currently, in supercritical carbon dioxide Brayton cycle power generation systems, the main compressor and recompressor are the most critical energy-consuming devices. Reducing the power consumption of the compressor will greatly improve the power generation efficiency of the system. The power consumption of the compressor is directly related to the inlet temperature of the compressed working fluid. The lower the inlet temperature, the less compression work and the lower the energy consumption. Compared with isentropic compression and polytropic compression processes, isothermal compression is the process with the least power consumption and is the only choice we most want to achieve in terms of energy saving and consumption reduction. In order to achieve isothermal compression, a cooler needs to be added inside or outside the compressor, especially internal cooling. To achieve high-efficiency heat exchange in a limited space, a compact heat exchanger must be used, and the PCEH printed circuit board heat exchanger is the most suitable choice.

[0003] However, in the PCHE of a supercritical carbon dioxide Brayton cycle power generation system, the supercritical carbon dioxide on the hot side operates near the quasi-critical temperature point (i.e., the high specific heat region of supercritical fluids), while the water on the cold side is in the subcooled region, resulting in a significant difference in the isobaric specific heat capacity between the hot and cold side working fluids. If a traditional counter-flow or co-flow printed circuit board heat exchanger is still used, the cold side flow area will be too large, causing the circulating cooling water to potentially operate in the laminar flow region, leading to a low heat transfer coefficient. To address this, we propose a centrifugal compressor with an integrated PCHE and tubular heat exchanger. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a centrifugal compressor with a built-in PCHE and tubular heat exchanger.

[0005] This invention provides a centrifugal compressor with a built-in PCHE and tubular heat exchanger, including a housing, wherein the housing contains: The rotor assembly includes a main shaft extending through the housing and a plurality of impellers disposed on the main shaft; The stator assembly, located downstream of each stage of the impeller along the airflow direction, includes a diffuser-type PCHE and a rectifier-type PCHE arranged in sequence, for converting airflow kinetic energy into pressure energy during operation. The volute chamber, located downstream of the rectifier PCHE, is connected to the downstream conveyor channel; and A tubular heat exchanger is disposed on the conveying channel downstream of the volute for heat exchange during operation; The shell and the outer wall of the heat exchange channel of the tubular heat exchanger are provided with a heat insulation cavity, which is formed together with the tubular heat exchanger through the volute.

[0006] Furthermore, the rotor assembly includes four closed-loop centrifugal three-dimensional impellers arranged sequentially along the main shaft.

[0007] Specifically, the diffuser-type PCHE is a straight-wall diffuser-type PCHE.

[0008] Specifically, the rectified PCHE is a spiral rectified PCHE.

[0009] Preferably, the tubular heat exchanger is formed by 3D printing and integrally formed with the shell.

[0010] Specifically, the tubular heat exchanger is provided in multiple sets and the tubular heat exchanger is arranged in segments along the main axis.

[0011] Furthermore, bearing housings are provided at both ends of the main shaft, and support bearings and thrust bearings are provided inside the bearing housings.

[0012] Furthermore, each end of the housing is provided with an inflation sealing port.

[0013] Furthermore, the outlet of the volute is connected to the gas-side inlet of the tubular heat exchanger via a conveying channel to guide the cooled gas to the inlet of the next stage impeller during operation.

[0014] Specifically, the flow channel cross-sections of the diffuser type PCHE and the rectifier type PCHE are of the broken line type, and the flow channels of the diffuser type PCHE and the rectifier type PCHE are arranged according to a logarithmic spiral pattern.

[0015] The beneficial effects of this invention are as follows: By arranging tubular heat exchangers between compression stages to cool the gas in stages, the specific work required for the next stage is reduced, compressor power consumption is decreased, the overall cycle thermal efficiency is improved, and the stable operating range is expanded. The diffuser-type PCHE uses a small-angle straight-wall diffusion to smoothly convert kinetic energy into static pressure and suppress separation, maintaining high static pressure recovery and low total pressure loss in the quasi-critical region where heat capacity changes drastically. The rectifier-type PCHE corrects inlet swirl and velocity distortion, providing uniform, near-rotation-free boundary conditions for the volute and downstream heat exchangers, reducing inter-stage matching sensitivity and the resulting performance fluctuations. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a centrifugal compressor with a built-in PCHE and tubular heat exchanger according to a specific embodiment of the present invention. Figure 2This is a schematic diagram of the diffuser-type PCHE of a centrifugal compressor with a built-in PCHE and tubular heat exchanger, according to a specific embodiment of the present invention. Figure 3 This is a schematic diagram of the rectifier-type PCHE of a centrifugal compressor with a built-in PCHE and tubular heat exchanger, according to a specific embodiment of the present invention. Figure 4 This is a schematic diagram of the structure of a tubular heat exchanger in a centrifugal compressor with a built-in PCHE and tubular heat exchanger, according to a specific embodiment of the present invention.

[0017] Among them, 1 is the left bearing housing, 2 is the thrust bearing, 3 is the left support bearing, 4 is the left air filling seal, 5 is the housing, 6 is the inlet and outlet of the first-stage pre-tube top cooler, 7 is the first-stage pre-tube top cooler, 8 is the first-stage rectifier PCHE, 9 is the first-stage diffuser PCHE, 10 is the first-stage impeller, 11 is the inlet and outlet of the second-stage tube top cooler, 12 is the second-stage tube cooler, 13 is the second-stage diffuser PCHE, 14 is the second-stage impeller, 15 is the second-stage rectifier PCHE, 16 is the third-stage tube top cooler, 17 is the third-stage rectifier PCHE, 18 is the third-stage diffuser PCHE, 19 is the third-stage impeller, 20 is the inlet and outlet of the fourth-stage tube top cooler, 21 is the fourth-stage tube top cooler, and 22 is the fourth-stage rectifier PCHE. PCHE, 23 Fourth-stage diffuser PCHE, 24 Fourth-stage after-tube top cooler, 25 Fourth-stage after-tube top cooler inlet and outlet, 26 Fourth-stage impeller, 27 Right charging seal, 28 Right support bearing, 29 Right bearing housing, 30 Fourth-stage inlet pipe, 31 Fourth-stage after-tube bottom cooler, 32 Fourth-stage after-tube bottom cooler inlet and outlet, 33 Fourth-stage volute, 34 Third-stage inlet pipe, 35 Third-stage bottom cooler inlet and outlet, 36 Third-stage volute, 37 Third-stage tube bottom cooler, 38 Second-stage volute, 39 Second-stage inlet pipe, 40 First-stage volute, 41 First-stage pre-tube bottom cooler inlet and outlet, 42 First-stage pre-tube bottom cooler, 43 First-stage inlet pipe. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] like Figure 1As shown in the figure, a centrifugal compressor with a built-in PCHE and tubular heat exchanger provided by a specific embodiment of the present invention includes a housing 5, which contains: a rotor assembly including a main shaft penetrating the housing 5 and multiple impellers disposed on the main shaft; a stator assembly disposed downstream of each stage of impellers along the airflow conveying direction, including a diffuser-type PCHE and a rectifier-type PCHE arranged sequentially to convert airflow kinetic energy into pressure energy during operation; a volute located downstream of the rectifier-type PCHE and connected to a downstream conveying channel; and a tubular heat exchanger disposed on the conveying channel downstream of the volute for heat exchange during operation; wherein, a heat insulation cavity is provided between the housing 5 and the outer wall of the heat exchange channel of the tubular heat exchanger, which is formed together by the volute and the tubular heat exchanger; PCHE refers to a dense channel structure made by processing tiny channels from thin metal sheets, stacking them layer by layer, and then diffusion-welding them into a whole. It is essentially a network of fluid channels with high strength, high pressure resistance, and small volume formed by incorporating many small and customizable flow channels into a solid metal. The shape and orientation of the channels can be designed as needed, and they can be used not only for heat exchange, but also for pure flow organization functions such as diffusion and rectification.

[0020] Specifically, the impeller includes a first impeller 10, a second impeller 14, a third impeller 19, and a fourth impeller 26 arranged sequentially, and the impellers are mounted on the main shaft using a red-sleeve method; the diffuser-type PCHE includes a first diffuser-type PCHE9, a second diffuser-type PCHE13, a third diffuser-type PCHE18, and a fourth diffuser-type PCHE23 correspondingly arranged downstream of the airflow of each stage impeller; the rectifier-type PCHE includes a first rectifier-type PCHE8, a second rectifier-type PCHE15, a third rectifier-type PCHE17, and a fourth rectifier-type PCHE22 correspondingly arranged downstream of each diffuser-type PCHE.

[0021] Furthermore, the tubular heat exchanger includes a first-stage pre-tubular upper cooler 7, a second-stage tubular cooler 12, a third-stage tubular upper cooler 16, a fourth-stage tubular upper cooler 21, a fourth-stage post-tubular upper cooler 24, a fourth-stage post-tubular lower cooler 31, a third-stage tubular lower cooler 37, and a first-stage pre-tubular lower cooler 42, which are correspondingly installed at each stage of the impeller.

[0022] Furthermore, the first-stage pre-pipe cooler 7 has a first-stage pre-pipe cooler inlet and outlet 6, the second-stage pipe cooler 12 has a second-stage pipe cooler inlet and outlet 11, the fourth-stage pipe cooler 21 has a fourth-stage pipe cooler inlet and outlet 20, the fourth-stage rear-pipe cooler 24 has a fourth-stage rear-pipe cooler inlet and outlet 25, the third-stage cooler 37 has a third-stage cooler inlet and outlet 35, and the first-stage pre-pipe cooler 42 has a first-stage pre-pipe cooler inlet and outlet 41.

[0023] Based on the above basic implementation method, the rotor assembly includes four closed centrifugal three-dimensional flow impellers arranged sequentially along the main shaft; the housing is provided with an air inlet pipe, including a first air inlet pipe 43, a second air inlet pipe 39, a third air inlet pipe 34 and a fourth air inlet pipe 30, the first end of each air inlet pipe is connected to the gas side outlet of the tubular heat exchanger at the corresponding position, and the second end is connected to the inlet housing of the next stage impeller.

[0024] Specifically, each stage of impeller is thermally mounted on the main shaft. The four-stage impeller is arranged in two pairs back-to-back to reduce axial aerodynamic force. The airflow from each stage enters the corresponding diffuser-type PCHE for diffusion and primary heat exchange from the impeller outlet, and then enters the corresponding rectifier volute-type PCHE printed circuit board heat exchanger for rectification and secondary heat exchange according to the spiral pattern. Finally, it is introduced into the corresponding built-in volute chamber for collection.

[0025] In one specific implementation, the diffuser type PCHE is a straight-wall diffuser type PCHE; the rectifier type PCHE is a spiral rectifier PCHE.

[0026] In this embodiment, the tubular heat exchanger is formed by 3D printing and integrally formed with the shell; multiple sets of tubular heat exchangers are provided and the tubular heat exchangers are segmented along the main axis, and the tubular heat exchanger includes at least a front section tubular heat exchanger, an interstage section tubular heat exchanger and a rear section tubular heat exchanger.

[0027] Furthermore, the diffuser-type PCHE smoothly converts the kinetic energy at the impeller outlet into static pressure by gradually enlarging the channel cross-section and unfolding the flow channel according to a logarithmic spiral law, minimizing boundary layer separation and strong vortices. The straightener-type PCHE redistributes and homogenizes the non-uniform airflow after diffusion, making the flow field entering the volute and downstream channel smoother and reducing secondary flow and pulsation.

[0028] In another specific embodiment, bearing housings are provided at both ends of the main shaft, and a support bearing and a thrust bearing 2 are provided inside the bearing housings; air-filled sealing ports are provided at both ends of the housing.

[0029] Specifically, the bearing housing includes a left bearing housing 1 and a right bearing housing 29, the support bearings include a left support bearing 3 and a right support bearing 28, and the air-filled sealing port includes a left air-filled sealing port 4 and a right air-filled sealing port 27. The bearing housing serves as the mounting cavity and protective shell for bearings and seals, providing lubrication and cooling channels, isolating the external environment, providing an interface for shaft positioning and maintenance, and offering the first line of defense against vibration, noise, and leakage. The support bearings bear the radial load of the rotor, limit the radial displacement of the main shaft, ensure the rotor runs smoothly on the designed rotor center track, and reduce the impact of rotor-stator friction. Clearance fluctuations suppress misalignment and instability near critical speeds; thrust bearings bear the aerodynamic forces and unbalanced forces of the rotor in the axial direction, limit the axial displacement of the main shaft, maintain the designed axial clearance between stages and ends, ensure that the impeller and stator components do not axially rub against each other, and transfer the axial load to the housing; the gas-filled sealing port provides stable, clean, and controlled pressure sealing gas to the shaft end sealing cavity, forming a slightly positive pressure flow from inside the housing to the outside, preventing the working fluid from leaking out and external impurities from intruding back, reducing the possibility of lubricating oil entering the process gas, and working with the emission and monitoring interfaces to achieve the adjustment and monitoring of the sealing status.

[0030] In one specific embodiment, the outlet of the volute is connected to the gas-side inlet of the tubular heat exchanger via a conveying channel to guide the cooled gas to the inlet of the next stage impeller during operation; the flow channel cross-section of the diffuser-type PCHE and the rectifier-type PCHE is of the broken line type, and the flow channels of the diffuser-type PCHE and the rectifier-type PCHE are arranged according to the logarithmic spiral law; wherein, the flow channels are formed by chemical etching and diffusion welding in alternating stacks; the volute includes a first volute 40, a second volute 38, a third volute 36, and a fourth volute 33 correspondingly arranged at each stage of the impeller.

[0031] In this embodiment, the volute is used to collect the circumferentially distributed airflow downstream of the impeller and further convert kinetic energy into static pressure, while balancing the circumferential pressure and flow distribution, reducing circumferential distortion and pulsation. Its gradually increasing cross-sectional area and volute geometry help control unfavorable pressure gradients, suppress separation and backflow, and smoothly guide the airflow to the delivery channel and downstream heat exchanger. The heat insulation cavity formed between the volute and the shell also reduces the heat conduction from the high-temperature medium to the shell, improving the overall thermal efficiency and component life.

[0032] Specifically, the polygonal cross-section, through its multifaceted small-angle polygons, creates controllable secondary flow and lateral mixing within a unit length, enhancing temperature and velocity homogenization and improving heat transfer and pressure recovery efficiency. The segmented wall shape refines and distributes unfavorable pressure gradients during diffusion, reducing local peak values ​​and delaying or preventing boundary layer separation, thus achieving lower losses at the same diffusion ratio. The polygonal cross-section facilitates plate fabrication and interlayer alignment, enhancing the in-plane stiffness and pressure-bearing capacity of the channel, making it suitable for high-pressure differential and compact integrated structures. For rectifying PCHEs, the transitions between polygonal surfaces effectively disperse large-scale vortices, reducing residual vorticity and making the outlet flow field closer to irrotation.

[0033] In another specific embodiment, during operation, external gas enters the first impeller via the main inlet and is accelerated by the impeller to form a high-energy airflow. The airflow first enters the diffuser-type PCHE located downstream of the impeller, spreading along the small-angle straight wall to smoothly convert kinetic energy into static pressure and reduce local unfavorable pressure gradients. Subsequently, the airflow enters the rectifying PCHE, where the broken-line cross-section and volute arrangement eliminate residual swirl and circumferential distortion, homogenizing the velocity and temperature fields and creating stable inlet conditions for subsequent flow collection.

[0034] Furthermore, the rectified airflow enters the volute, where it is collected along a gradually increasing cross-sectional area, further achieving dynamic and static pressure conversion, and balancing the circumferential pressure distribution. The volute outlet connects to the downstream conveying channel, and the airflow is guided into the gas-side channel of the tubular heat exchanger, where it exchanges heat with the water-side cooling water for cooling. The heat-exchanged gas returns to the inlet of the next stage impeller through the interstage inlet pipe, forming an axially uniform, essentially irrotational inflow, which is then accelerated again by the impeller and enters the subsequently arranged diffuser-type PCHE and rectifier-type PCHE. The above process of "impeller compression—PCHE diffusion—PCHE rectification—volute collection—heat exchange and cooling—interstage return" is repeated sequentially in the multi-stage structure, progressively increasing the pressure and density of the medium.

[0035] Furthermore, the volute and tubular heat exchanger within the casing 5 together form a heat insulation cavity between their outer sides and the casing, reducing heat backflow of high-temperature gas into the casing and improving thermal efficiency and component lifespan. Inside the bearing housings at both ends of the main shaft, the support bearings bear the radial load to limit radial displacement, while the thrust bearings bear the axial load to maintain stable axial clearance. The gas-filled sealing ports at both ends of the casing provide clean and stable sealing gas to the sealing cavity, creating a slight positive pressure to prevent media leakage and impurity backflow. Through the aforementioned synergistic flow, heat exchange, and insulation, the entire unit achieves efficient multi-stage compression and reliable operation within a compact structure.

[0036] To aid in a better understanding of the invention, a more comprehensive and specific embodiment is described. In this embodiment, the invention provides a centrifugal compressor with a built-in PCHE and a tubular heat exchanger, comprising a housing 5. The housing 5 contains: a rotor assembly including a main shaft penetrating the housing 5 and a plurality of impellers mounted on the main shaft; a stator assembly, located downstream of each impeller stage along the airflow direction, including a diffuser-type PCHE and a rectifier-type PCHE arranged sequentially to convert airflow kinetic energy into pressure energy during operation; a volute located downstream of the rectifier-type PCHE and connected to a downstream conveying channel; and a tubular heat exchanger located on the conveying channel downstream of the volute for heat exchange during operation; wherein a heat insulation cavity is formed between the housing 5 and the outer wall of the heat exchange channel of the tubular heat exchanger, the heat insulation cavity being formed jointly by the volute and the tubular heat exchanger.

[0037] In this embodiment, the rotor assembly includes four closed-loop centrifugal three-dimensional impellers arranged sequentially along the main shaft; the diffuser-type PCHE is a straight-wall diffuser-type PCHE; the rectifier-type PCHE is a volute rectifier PCHE; the tubular heat exchanger is formed by 3D printing and integrally formed with the shell; multiple sets of tubular heat exchangers are provided and the tubular heat exchangers are segmented along the main shaft; bearing housings are respectively provided at both ends of the main shaft, and support bearings and thrust bearings are provided in the bearing housings; and air-filled sealing ports are respectively provided at both ends of the shell.

[0038] Specifically, the outlet of the volute is connected to the gas-side inlet of the tubular heat exchanger via a conveying channel to guide the cooled gas to the inlet of the next stage impeller during operation; the flow channel cross-section of the diffuser type PCHE and the rectifier type PCHE is of the broken line type, and the flow channels of the diffuser type PCHE and the rectifier type PCHE are arranged according to the logarithmic spiral law.

[0039] In summary, the embodiments disclosed herein have at least the following technical effects: By arranging tubular heat exchangers between compression stages to cool the gas in stages, the specific work required for the next stage is reduced, compressor power consumption is reduced, the overall cycle thermal efficiency is improved, and the stable operating range is expanded. PCHE's zigzag microchannels can induce controllable secondary flow and lateral mixing even at low Reynolds numbers, improving the convective heat transfer coefficient between the cold-side water side and the hot-side supercritical carbon dioxide, and alleviating heat transfer degradation caused by cold-side laminar flow. The PCHE flow channels are arranged in a logarithmic spiral pattern to make the equivalent flow resistance of each circumferential branch more consistent, improve the circumferential flow and temperature distribution, reduce unevenness between channels and bypass flow, and improve the utilization rate of effective heat exchange area. The diffuser-type PCHE uses a small-angle straight-wall diffusion to smoothly convert kinetic energy into static pressure and suppress separation, maintaining high static pressure recovery and low total pressure loss in the quasi-critical region where heat capacity changes drastically. The rectifier PCHE corrects inlet swirl and velocity distortion, providing uniform, near-rotation-free boundary conditions for the volute and downstream heat exchangers, reducing interstage matching sensitivity and the resulting performance fluctuations; The vortex chamber balances the circumferential pressure while collecting and re-diffusing, making the airflow returned to the tubular heat exchanger more stable, reducing inlet pulsation at the heat exchange end, and improving the time-averaged utilization of the heat transfer driving force. By appropriately controlling the flow area and channel geometry on the cold side, the characteristic velocity can be increased at a given flow rate, keeping the water-side Reynolds number at the upper edge of the turbulent or transition zone, thus significantly improving the cold-side film coefficient. The compact, integrated layout of the PCHE with the shell 5 and the tubular heat exchanger shortens the process path, reduces additional pressure drop and heat leakage caused by piping and joints, and reduces installation errors and leakage risks. A heat insulation cavity is formed between the shell and the heat exchange components, which reduces the heat backflow of the high-temperature working fluid to the shell, bearings and seals, reduces thermal stress and thermal deformation, and improves long-term operational reliability. Interstage return uses a small-angle tangential connection and reserves an axial straight section. Combined with the rectification structure, it reduces the reintroduction of swirl and secondary flow, ensuring uniform inlet flow at each stage and improving the cumulative efficiency when multiple stages are connected in series. Chemical etching forms microchannels, which are then densified by diffusion welding to obtain a high-strength, high-density metal heat exchange core that is resistant to high pressure differentials and high temperatures, has short leakage channels, and is suitable for the harsh conditions of supercritical carbon dioxide. The tubular heat exchanger is manufactured using additive manufacturing and integrally formed with the shell, which can integrate manifolds, flow straightening fins and measuring point seats, making it easier to optimize the cold side flow velocity distribution and monitoring point layout, and improving manufacturing consistency and maintainability; The sequential coupling of multi-stage impellers with PCHE, volute, and tubular heat exchangers will closely link energy recovery, rectification and homogenization, and segmented cooling, achieving higher pressure ratio, lower specific energy consumption, and better thermal management under the same volume and material constraints. For the high specific heat side of the quasi-critical region, the area gradient and path expansion design of PCHE can adaptively change the heat capacity along the path, reduce single-point undercooling or overheating, improve temperature glide matching, and increase the effective heat transfer driving force. By improving the cold-side flow pattern, reducing total pressure loss, and stabilizing the inlet boundary, this scheme reduces the risk of surge and improves the rotor dynamic boundary friendliness, enabling the device to maintain high efficiency and reliability under partial load and variable operating conditions.

[0040] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A centrifugal compressor with a built-in PCHE and tubular heat exchanger, characterized in that, Includes a housing, which contains: The rotor assembly includes a main shaft extending through the housing and a plurality of impellers disposed on the main shaft; The stator assembly, located downstream of each stage of the impeller along the airflow direction, includes a diffuser-type PCHE and a rectifier-type PCHE arranged in sequence, for converting airflow kinetic energy into pressure energy during operation. The volute chamber, located downstream of the rectifier PCHE, is connected to the downstream conveyor channel; and A tubular heat exchanger is disposed on the conveying channel downstream of the volute for heat exchange during operation; The shell and the outer wall of the heat exchange channel of the tubular heat exchanger are provided with a heat insulation cavity, which is formed together with the tubular heat exchanger through the volute.

2. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The rotor assembly includes four closed-loop centrifugal three-dimensional impellers arranged sequentially along the main shaft.

3. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The diffuser-type PCHE is a straight-wall diffuser-type PCHE.

4. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The rectifier PCHE is a spiral rectifier PCHE.

5. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The tubular heat exchanger is formed by 3D printing and integrally molded with the shell.

6. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 5, characterized in that, The tubular heat exchanger is provided in multiple sets and the tubular heat exchanger is arranged in sections along the main axis.

7. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, Bearing housings are provided at both ends of the main shaft, and support bearings and thrust bearings are installed inside the bearing housings.

8. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The shell has an inflation sealing port at each end.

9. The centrifugal compressor with built-in PCHE and tubular heat exchanger according to claim 1, characterized in that, The outlet of the volute is connected to the gas-side inlet of the tubular heat exchanger via a conveying channel to guide the cooled gas to the inlet of the next stage impeller during operation.

10. The centrifugal compressor with a built-in PCHE and tubular heat exchanger according to any one of claims 1 to 9, characterized in that, The flow channel cross-sections of the diffuser type PCHE and the rectifier type PCHE are polygonal, and the flow channels of the diffuser type PCHE and the rectifier type PCHE are arranged according to a logarithmic spiral pattern.

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