Compression expansion co-extruder for supercritical carbon dioxide Brayton system

Abstract

The present invention relates to a compression-expansion co-machine for a supercritical carbon dioxide Brayton system, comprising a compressor and an expander installed in a cylinder body, the compressor and the expander share a co-machine impeller, the co-machine impeller and the cylinder body form a compressor chamber and an expander chamber that are independent and closed from each other, the compressor chamber is provided with a compressor air inlet end and a compressor air outlet end, the expander chamber is provided with an expander air inlet end and an expander air outlet end, the co-machine impeller is installed on the main shaft of a support unit, the compressor is located between the expander and the support unit, one side of the compressor chamber is sealed with the expander chamber by a mechanical gap seal, and the other side of the compressor chamber is sealed with the external space by a mechanical dynamic seal. The present invention eliminates the dynamic seal that is extremely difficult to design to prevent the high-temperature and high-pressure supercritical carbon dioxide gas of the expander from leaking to the external space.

Description

Technical Field

[0001] The invention relates to a Brayton system, in particular to a compression-expansion co-machine for a supercritical carbon dioxide Brayton system. Background Art

[0002] Since the Brayton cycle has no phase change in principle, as a source of energy and power, its thermal efficiency is much higher than the current thermal power generation (Rankine cycle) of about 40%, and theoretically it can reach more than 75%. Moreover, the required heat source comes from a wide range of sources, such as fossil fuels, solar energy, biofuels and even waste heat. The temperature range of the heat source is relatively wide, and it can generally be used as long as it reaches above 500°C. The energy density is high, and the same installed power requires less and more sophisticated equipment. Fewer auxiliary conditions are required, such as the amount of cooling water used is far less than that of a thermal power plant, which is more environmentally friendly. Domestic and foreign experts and institutions have invested a lot of research on the supercritical carbon dioxide Brayton cycle.

[0003] In order to pursue the miniaturization and integration of the overall system structure, it is a feasible solution to arrange the compressor and expander in the same cylinder. The structure is that the compressor impeller and the expander impeller are cantilevered on the extended shaft of the support system, and a sealing component is set between the impellers; the compressor and the expander are independently provided with flow-through stationary components. How to shorten the extended section of the support system in order to improve the overall rigidity of the rotor is of great significance to improving the rotor dynamics of the unit.

[0004] At the same time, the operating temperature of the expander is above 500°C and the working pressure is above 20MPa. There is currently no mechanical dynamic seal that meets the conditions. Even if a load-bearing mechanical dynamic seal is developed in the future, the cost will be extremely high. This is also one of the technical difficulties in the current global research on supercritical carbon dioxide Brayton cycle. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention provides a compression-expansion co-machine for a supercritical carbon dioxide Brayton system, in which the compressor and the expander share the same co-machine impeller, thereby eliminating the dynamic seal, which is extremely difficult to design, for preventing the high-temperature and high-pressure supercritical carbon dioxide gas of the expander from leaking into the external space.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A compression-expansion co-machine for a supercritical carbon dioxide Brayton system comprises a compressor and an expander installed in a cylinder body, the compressor and the expander share a co-machine impeller, the co-machine impeller and the cylinder body form a compressor chamber and an expander chamber that are independent and closed from each other, the compressor chamber is provided with a compressor air inlet end and a compressor air outlet end, the expander chamber is provided with an expander air inlet end and an expander air outlet end, the co-machine impeller is installed on the main shaft of a support unit, the compressor is located between the expander and the support unit, one side of the compressor chamber is sealed with the expander chamber by a mechanical gap seal, and the other side of the compressor chamber is sealed with an external space by a mechanical dynamic seal.

[0008] Preferably, the common impeller comprises a wheel disc, compressor blades and expander blades, and the compressor blades and expander blades are respectively fixedly mounted on both sides of the wheel disc.

[0009] Preferably, the common impeller further comprises a compressor wheel cover and an expander wheel cover, the compressor blades are fixedly mounted between the wheel disc and the compressor wheel cover, and the expander blades are fixedly mounted between the wheel disc and the expander wheel cover.

[0010] Preferably, the wheel disc includes a compressor wheel disc, an expander wheel disc and a middle disc, the compressor wheel disc and the expander wheel disc are respectively located on both sides of the middle disc, the wheel disc is an integrally formed part, or at least one of the compressor wheel disc and the expander wheel disc is welded to the middle disc, and the mechanical gap seal is radially or axially sleeved on the middle disc.

[0011] Preferably, the wheel disc comprises a compressor wheel disc, an expander wheel disc and a spacer sleeve, the compressor wheel disc and the expander wheel disc are respectively mounted on both sides of the spacer sleeve, and the mechanical gap seal is radially or axially sleeved on the spacer sleeve.

[0012] Preferably, the mechanical gap seal is a comb seal, the mechanical dynamic seal is a tandem dry gas seal structure, and the supporting device is a high-speed generator or a bearing seat.

[0013] Preferably, the expander air inlet end is arranged along the radial direction of the cylinder body, the expander air outlet end is arranged along the axial direction of the cylinder body, and the compressor air inlet end and the compressor air outlet end are both arranged along the radial direction of the cylinder body.

[0014] The beneficial effects of the present invention are as follows: the compressor and the expander in the present invention share a common impeller, and the compressor and the expander are installed in the same cylinder body. On the one hand, the requirement for the length of the main shaft of the unit is greatly reduced, which is of great significance to improving the rotor dynamic characteristics, and provides the possibility for further improving the working speed and increasing the installed power of the system; on the other hand, for the expansion end, one side is the exhaust end of the expander, and no dynamic seal is required, and the other side is a gap seal between the mechanical gap seal and the compression end, and a small amount of high-temperature and high-pressure supercritical carbon dioxide leaks from the expander chamber to the compressor chamber, which does not affect the operation of the compressor, and eliminates the design difficulty. The dynamic seal can greatly prevent the high-temperature and high-pressure supercritical carbon dioxide gas of the expander from leaking to the external space; for the external dynamic seal of the expander and the compressor, it is only necessary to rely on the mechanical dynamic seal on the compressor side. Since the temperature of carbon dioxide on the compressor side is low, the mechanical dynamic seal with mature technology can be used for sealing, thereby converting the problem of high-temperature and high-pressure dynamic sealing into a problem of low-temperature sealing, solving a major problem of the supercritical carbon dioxide Brayton cycle system and realizing the implementation and application of the system; in the working state of the system, the expander impeller directly drives the compressor impeller, avoiding the driving energy conversion at the compression end and improving the system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of Example 1 of the present invention;

[0016] Figure 2 for Figure 1 Schematic diagram of medium flow direction;

[0017] Figure 3 This is a schematic diagram of the structure using axial gap sealing in Example 1;

[0018] Figure 4 This is a schematic diagram of the structure of Example 2 of the present invention;

[0019] Figure 5 A schematic diagram of a Brayton system in the present invention;

[0020] In the figure: 10-compressor, 11-compressor air inlet end, 12-compressor air outlet end, 20-expander, 21-expander air inlet end, 22 expander air outlet end, 30-common impeller, 31-compressor wheel disc, 32-compressor blades, 33-compressor wheel cover, 34-expander wheel disc, 35-expander blades, 36-expander wheel cover, 37-center disc, 38-spacer, 40-cylinder body, 41-mechanical gap seal, 42-mechanical dynamic seal, 50-support unit, 51-main shaft, 61-heat source, 62-cooler, 63-gas control unit, 64-regulating valve, 65-preheater. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0024] like Figure 1-5As shown, a compression-expansion co-machine for a supercritical carbon dioxide Brayton system includes a compressor 10 and an expander 20 installed in a cylinder body 40, wherein the compressor 10 and the expander 20 share a co-machine impeller 30, wherein the co-machine impeller 30 and the cylinder body 40 form a compressor chamber and an expander chamber which are independent and closed from each other, wherein the compressor chamber is provided with a compressor inlet end 11 and a compressor outlet end 12, wherein the expander chamber is provided with an expander inlet end 21 and an expander outlet end 22, wherein the co-machine impeller 30 is installed on a main shaft 51 of a support unit 50, wherein the compressor 10 is located between the expander 20 and the support unit 50, wherein one side of the compressor chamber is sealed with the expander chamber by a mechanical gap seal 41, and the other side of the compressor chamber is sealed with the external space by a mechanical dynamic seal 42.

[0025] One end of the main shaft 51 is supported by the support unit 50, and the other end is fixedly mounted with the co-body impeller 30; Figure 5 As shown in the figure, the arrows indicate the gas flow direction. The Brayton system includes a compressor 10, a heat source 61, an expander 20 and a cooler 62 which are connected in sequence to form a gas circuit, and the high-temperature gas from the expander 20 passes through a preheater 65 to preheat the gas from the compressor 10 before it enters the heat source 61. A gas control unit 63 is provided on the gas circuit, and a regulating valve 64 is provided between the gas control unit and the gas circuit. The gas control unit 63 is used to supplement or discharge gas.

[0026] In the present invention, the compressor 10 and the expander 20 are installed in the same cylinder body 40, and two independent closed spaces are formed in the cylinder body. Therefore, the working medium of the compressor and the expander circulates through independent flow paths. The compressor chamber and the expander chamber are sealed by a commonly used mechanical gap seal. The sealing requirement is not high. Even if a small amount of high-temperature and high-pressure supercritical carbon dioxide leaks from the expander chamber into the compressor chamber, it will not affect the normal operation of the compressor. In the present invention, the compressor 10 and the expander 20 use a common impeller 30. On the one hand, the requirement for the length of the main shaft of the unit is greatly reduced, which is of great significance to improving the rotor dynamic characteristics. It is large, which makes it possible to further increase the working speed and the installed power of the system; on the other hand, it eliminates the dynamic seal that is extremely difficult to design to prevent the high-temperature and high-pressure supercritical carbon dioxide gas of the expander from leaking to the external space; for the external dynamic seal of the expander and the compressor, it is only necessary to rely on the mechanical dynamic seal on the compressor side. Since the temperature of carbon dioxide on the compressor side is low, it is sufficient to use mature mechanical dynamic seals, such as the tandem dry gas seal structure, thereby converting the problem of high-temperature and high-pressure dynamic sealing into a problem of low-temperature sealing, solving a major problem of the supercritical carbon dioxide Brayton cycle system and realizing the implementation and application of the system.

[0027] The co-body impeller 30 comprises a wheel disc, compressor blades 32 and expander blades 35, wherein the compressor blades 32 and expander blades 35 are respectively fixedly mounted on both sides of the wheel disc. In this embodiment, the co-body impeller is a semi-open impeller.

[0028] The co-body impeller 30 further includes a compressor wheel cover 33 and an expander wheel cover 36. The compressor blades 32 are fixedly installed between the wheel disc and the compressor wheel cover 33, and the expander blades 35 are fixedly installed between the wheel disc and the expander wheel cover 36. In this embodiment, the co-body impeller is a closed impeller.

[0029] Example 1: Figure 1-3 As shown, the impeller includes a compressor impeller 31, an expander impeller 34 and a middle disk 37. The compressor impeller 31 and the expander impeller 34 are respectively located on both sides of the middle disk 37. The impeller is an integrally formed part, or at least one of the compressor impeller 31 and the expander impeller 34 is welded to the middle disk 37. The mechanical gap seal 41 is radially or axially sleeved on the middle disk 37. The compressor impeller 31, the compressor blades 32 and the compressor wheel cover 33 form a compressor impeller, and the compressor impeller is located in the compressor sealing cavity. The expander impeller 34, the expander blades 35 and the expander wheel cover 36 form an expander impeller, and the expander impeller is located in the expander sealing cavity. The compressor impeller and the expander impeller are arranged back to back, as shown in Figure 1. The working medium of the compressor and the expander circulates through independent circulation channels. A radial gap seal is provided on the outer diameter of the middle disk of the compressor impeller and the expander impeller (as shown in Figure 2), and the middle disk structure can also be adjusted to be set as an axial gap seal (as shown in Figure 3). Figure 3 As shown in the figure, the expander impeller is located between the expander outlet end and the compressor impeller. For the expansion end, one side is the expander outlet end, so no dynamic seal is required, and the other side is the compression end. The expander chamber and the compressor chamber are sealed by a commonly used mechanical gap seal. The sealing requirement is not high. Even if a small amount of high-temperature and high-pressure supercritical carbon dioxide leaks from the expander chamber into the compressor chamber, it will not affect the normal operation of the compressor.

[0030] Example 2: Figure 4As shown, the impeller includes a compressor impeller 31, an expander impeller 34 and a spacer 38, wherein the compressor impeller 31 and the expander impeller 34 are respectively mounted on both sides of the spacer 38, and the mechanical gap seal 41 is radially or axially sleeved on the spacer 38. The compressor impeller 31 and the expander impeller 34 are processed separately, and then the two impellers are respectively mounted on the spacer 38 to form an integral part, and the spacer generally has a heat insulation function, the compressor impeller 31, the compressor blades 32 and the compressor wheel cover 33 form a compressor impeller, and the compressor impeller is located in the compressor sealing chamber, the expander impeller 34, the expander blades 35 and the expander wheel cover 36 form an expander impeller, and the expander impeller is located in the expander sealing chamber, the compressor impeller and the expander impeller are arranged back to back, and the expander impeller is located between the expander outlet and the compressor impeller.

[0031] like Figure 1 As shown, the mechanical gap seal 41 is a comb seal, the mechanical dynamic seal 42 is a series dry gas seal structure, and the support device 81 is a high-speed generator or a bearing seat. The series dry gas seal structure is a container structure in which the medium side mechanical seal and the atmosphere side dry gas seal are arranged in series. The first-level mechanical seal is the main seal, and the second-level dry gas seal is an auxiliary safety seal. The series dry gas seal structure is a mature structure in this field and will not be described in detail here. The series dry gas seal structure is used for dynamic sealing between the compressor and the outside world, which can meet the sealing requirements of the compressor; the comb seal is also a commonly used sealing structure in the compressor 10. A technically mature comb seal is set between the compressor chamber and the expander chamber. As the dynamic seal of the expander, it can seal most of the high-temperature gas in the expander chamber. Even if a small amount of high-temperature gas in the expander chamber leaks and mixes into the intake air of the compressor and enters the compressor impeller, it will not affect the normal operation of the compressor, and will not cause harm to the environment.

[0032] like Figure 2As shown, the arrows in the figure indicate the flow direction of the medium, the expander air inlet end 21 is arranged along the radial direction of the cylinder body 40, the expander air outlet end 22 is arranged along the axial direction of the cylinder body 40, and the compressor air inlet end 11 and the compressor air outlet end 12 are both arranged along the radial direction of the cylinder body. Two independent closed spaces are formed in the cylinder body, so the working medium of the compressor and the expander circulates through independent flow paths. The medium in the compressor is taken in through the compressor inlet end 11 and discharged from the compressor outlet end, and the medium in the expander is taken in through the expander inlet end 21 and discharged from the expander outlet end 22; that is, the compressor 10 adopts radial intake and radial exhaust, and the expander adopts radial intake and axial exhaust. Therefore, for the expander impeller, one side is the exhaust end of the expander and does not require dynamic sealing, and the other side is a gap seal between the mechanical gap seal 41 and the compressor impeller. A small amount of high-temperature and high-pressure supercritical carbon dioxide leaks from the expander chamber to the compressor chamber without affecting the operation of the compressor, thereby eliminating the dynamic seal that is extremely difficult to design to prevent the high-temperature and high-pressure supercritical carbon dioxide gas of the expander from leaking to the outside.

[0033] The implementation process of the present invention: the steps are as follows:

[0034] Step 1: Processing of the common impeller 30

[0035] Method 1: directly processing an integral impeller, one side of the impeller is a compressor impeller, and the other side is an expander impeller, and then processing blades and wheel covers on the integral impeller to form a common impeller 30;

[0036] Method 2: The compressor impeller 31 and the expander impeller 34 share a middle disk 37, and the middle disk 37 is processed separately, or the middle disk contains one of the compressor blade disk and the expander blade disk, and then the compressor blade disk is welded to the middle disk, or the expander blade disk is welded to the middle disk, or the compressor blade disk and the expander blade disk are connected to the middle disk by welding to form an integral impeller, and then blades and wheel covers are processed on the integral impeller to form a common impeller 30;

[0037] Method 3: The compressor impeller 31 and the expander impeller 34 are processed separately, and the compressor impeller and the expander impeller are installed on both sides of the spacer 38 to form an integral impeller, and then blades and wheel covers are processed on the integral impeller to form a common impeller 30;

[0038] In the common impellers processed by the three processing methods, the compressor impeller and the expander impeller are arranged back to back along the axial direction;

[0039] Step 2: Install the processed common impeller 30 on the protruding end of the main shaft 51 of the support unit, and make the compressor impeller side close to the proximal end of the cantilever, and the expander impeller side close to the distal end of the cantilever;

[0040] Step 3: The common impeller 30 is installed in the common cylinder body 40, and its working medium flows through independent flow paths. One side of the compressor chamber is sealed with the expander chamber by a mechanical gap seal 41, and the other side of the compressor chamber is sealed with the external space by a mechanical dynamic seal 42.

[0041] It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A compression expansion co-extruder for a supercritical carbon dioxide Brayton system, characterized in that: The invention comprises a compressor (10) and an expander (20) installed in a cylinder body (40), wherein the compressor (10) and the expander (20) share a common impeller (30), wherein the common impeller (30) and the cylinder body (40) form a compressor chamber and an expander chamber that are independent and closed from each other, wherein the compressor chamber is provided with a compressor air inlet end (11) and a compressor air outlet end (12), wherein the expander chamber is provided with an expander air inlet end (21) and an expander air outlet end (22), wherein the common impeller (30) is installed on a main shaft (51) of a support unit (50), wherein the compressor (10) is located between the expander (20) and the support unit (50), wherein one side of the compressor chamber is sealed with the expander chamber by a mechanical gap seal (41), and the other side of the compressor chamber is sealed with an external space by a mechanical dynamic seal (42); The common impeller (30) comprises a wheel disc, a compressor blade (32) and an expander blade (35), wherein the compressor blade (32) and the expander blade (35) are respectively fixedly mounted on both sides of the wheel disc, the wheel disc comprises a compressor wheel disc (31), an expander wheel disc (34) and a middle disc (37), wherein the compressor wheel disc (31) and the expander wheel disc (34) are respectively located on both sides of the middle disc (37), the wheel disc is an integrally formed part, or at least one of the compressor wheel disc (31) and the expander wheel disc (34) is welded to the middle disc (37), and the mechanical gap seal (41) is radially or axially sleeved on the middle disc (37); The mechanical gap seal (41) is a comb-tooth seal, the mechanical dynamic seal (42) is a series dry gas seal structure, the expander air inlet end (21) is arranged along the radial direction of the cylinder body (40), the expander air outlet end (22) is arranged along the axial direction of the cylinder body (40), and the compressor air inlet end (11) and the compressor air outlet end (12) are both arranged along the radial direction of the cylinder body.

2. The compression-expansion co-machine for supercritical carbon dioxide Brayton system according to claim 1, characterized in that: The common impeller (30) further comprises a compressor wheel cover (33) and an expander wheel cover (36), wherein the compressor blades (32) are fixedly mounted between the wheel disc and the compressor wheel cover (33), and the expander blades (35) are fixedly mounted between the wheel disc and the expander wheel cover (36).

3. The compression-expansion co-machine for supercritical carbon dioxide Brayton system according to claim 1, characterized in that: The wheel disc comprises a compressor wheel disc (31), an expander wheel disc (34) and a spacer sleeve (38); the compressor wheel disc (31) and the expander wheel disc (34) are respectively mounted on two sides of the spacer sleeve (38); and the mechanical gap seal (41) is radially or axially sleeved on the spacer sleeve (38).

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