Impeller machine capable of increasing stability and reducing axial force and regulation and control method

Abstract

The impeller machine capable of stabilizing and reducing the axial force comprises a turbine impeller and a nozzle base, the nozzle base is arranged on the blade back side of the turbine impeller, and a gap is formed between the impeller back of the turbine impeller and the nozzle base; a groove is formed in the nozzle base in the circumferential direction of the nozzle base, and an adjusting piece used for adjusting the geometric space of a fluid domain of a turbine impeller back cavity is arranged in the groove. The adjustable rib-shaped structure is driven by the power structure to move back and forth in the axial direction, so that leakage flow in the wheel back cavity does not perform simple rotary Taylor-Couette flow any more, but performs complex flow behaviors under the action of the protrusions or the grooves in combination with the rotary friction action of the wheel back disc, and the flow speed is increased. Under the condition, the pressure drop rate of the wheel back leakage flow in the radius direction of the wheel disc can be increased or decreased so as to achieve the state of being balanced with axial load adjustment generated by a pressure field of a working medium at the impeller.

Description

Technical Field

[0001] The present invention belongs to the field of thermal power and fluid machinery, and particularly relates to an impeller machine capable of increasing stability and reducing axial force and a control method thereof. Background Art

[0002] Nowadays, with the rapid development of science and technology in various fields, energy consumption is increasing dramatically. From a global perspective, traditional fossil energy is still the mainstream application in the energy structure of most countries. However, the crisis of fossil energy depletion and related environmental protection issues have become imminent. With the proposal of the dual carbon goals of "carbon peak" and "carbon neutrality", the field of energy and power engineering has also ushered in huge challenges. In the context of the immature development of various new types of clean energy and the inability to completely replace traditional energy in a short period of time in practical applications, it is more practical and effective to study how to more efficiently realize the conversion of thermal energy and mechanical work.

[0003] In terms of thermodynamic cycles of functional conversion, electricity production based on water steam cycles currently accounts for 80% of the world's total electricity production. However, based on long-term scientific research and progress, the technology of the traditional water steam Rankine cycle is very mature and has reached a very high level. Due to the nature of water steam itself, turbine machinery materials and structural limitations, it is quite difficult to continue to develop and significantly improve efficiency. In recent years, facing this common bottleneck in the energy field for all mankind, researchers from all over the world have begun to turn their attention to the Brayton cycle of supercritical carbon dioxide.

[0004] Supercritical carbon dioxide (SCO2) refers to a carbon dioxide fluid whose temperature and pressure both exceed the critical value (temperature 304.13K, pressure 7.3773MPa). Carbon dioxide itself is non-toxic and harmless and has stable chemical properties, so it has extremely high safety both in the experimental stage and in industrial production. In addition, carbon dioxide is widely distributed in the atmosphere, accounts for a certain proportion in the air, and does not directly pollute the environment, which also makes it easy to obtain and environmentally friendly. Carbon dioxide fluid in the supercritical state has many physical properties such as high density, low viscosity and large specific heat capacity, which makes it an ideal working fluid with excellent properties in thermal cycles. Compared with other supercritical fluids, the critical point of carbon dioxide is not harsh and is relatively easy to reach. These properties can effectively reduce costs and greatly improve energy conversion efficiency in thermal cycles.

[0005] In addition, the supercritical carbon dioxide Brayton cycle can be more compact than the common traditional thermal cycle. In the field of energy and power engineering, reducing the size of the equipment without reducing efficiency can make the device more applicable and widely applicable to power generation systems with various forms of energy such as traditional fossil energy, nuclear energy, solar energy and geothermal energy.

[0006] The SCO2 centrifugal turbine machinery is the core device for converting heat energy into mechanical work in the SCO2 Brayton cycle. Its efficiency, safety and other performances will be directly related to the operation of the entire system. Every 1% increase in turbine efficiency can bring about a 1% increase in cycle efficiency. Furthermore, the benefits of the centrifugal turbine in practical applications are far more than theoretical improvements. It has brought many practical improvements to the rotor system, such as more economical and efficient use of seals, stronger stability in the face of mechanical vibrations, higher blade load bearing capacity, and the ability to build a simpler and clearer system structure. These improvements enable the centrifugal turbine to not only adapt to various complex operating conditions, but also ensure low maintenance costs in long-term operation.

[0007] During the operation of the SCO2 centrifugal turbine, the leakage flow of the wheel back cavity generates a large pressure field in the cavity, causing a huge axial load. This partial load is difficult to balance with the axial load generated by the hub surface. The combined force of the two has a great impact on the stability and safety of the turbine wheel operation. In the few experiments conducted worldwide, the existence of this ultra-high axial force has seriously shortened the service life of the SCO2 turbine device and posed a great safety hazard. Therefore, when designing the turbine impeller, it is also necessary to focus on the flow field characteristics in the wheel back cavity, so that the flow in the wheel back cavity also meets the safety requirements, and in order to find an optimal solution to balance the axial force. Summary of the invention

[0008] The purpose of the present invention is to provide an impeller machine and a control method that can increase stability and reduce axial force, thereby solving the problem that the pressure field formed by the leakage flow in the wheel back cavity of the existing high-speed impeller is difficult to balance with the stress on the hub surface, resulting in a large axial load and causing a large safety hazard for the impeller.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is: The present invention provides an impeller machine capable of increasing stability and reducing axial force, comprising a turbine impeller and a nozzle base, wherein the nozzle base is disposed on the back side of the turbine impeller, and a gap is provided between the back of the turbine impeller and the nozzle base; The nozzle base is provided with a groove arranged along its circumference, and an adjustment member for adjusting the fluid domain geometric space of the turbine impeller wheel back cavity is arranged in the groove.

[0010] Preferably, the adjusting member comprises an adjustable rib-shaped structure and a power structure, and the power structure is arranged between the adjustable rib-shaped structure and the bottom of the groove.

[0011] Preferably, the turbine impeller and the nozzle base are both mounted on the main shaft.

[0012] Preferably, a plurality of nozzles are arranged on the nozzle base along its circumference, and the outlets of the plurality of nozzles face one side of the blades of the turbine impeller, so as to facilitate the supercritical carbon dioxide working fluid to enter from the radial direction of the turbine impeller.

[0013] Preferably, the nozzle base is connected to the main shaft via a bearing.

[0014] Preferably, a casing is mounted on the main shaft, and the casing is located at the blade side of the turbine impeller.

[0015] Preferably, it further comprises a control system, wherein the input end of the control system is connected to the load acquisition unit, and the output end of the control system is connected to the power structure.

[0016] Preferably, the load collection unit is a thrust sensor, which is used to collect the axial load on the measuring point.

[0017] Preferably, the load collection unit is also connected to an axial load monitoring device for visually reading the collected axial load.

[0018] A method for regulating the axial force of an impeller machine, based on the impeller machine, comprises the following steps: In an initial state, a surface of the adjustable rib structure away from the power structure is flush with the surface of the nozzle base; After the impeller machinery starts running, the axial load of the set measuring point is obtained in real time; The movement of the adjusting member is controlled according to the obtained axial load, and the adjusting member is used to adjust the geometric space of the fluid domain of the turbine impeller back cavity, thereby achieving the purpose of balancing the axial force.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an impeller machine capable of increasing stability and reducing axial force. A groove is provided on a nozzle base disposed on the rear side of a turbine impeller wheel back cavity, and an adjustable rib structure and a power structure are arranged in the groove. The adjustable rib structure is driven by the power structure to move back and forth along the axial direction, so that the leakage flow in the wheel back cavity is no longer a simple rotational Taylor-Couette flow, but a complex flow behavior under the action of protrusions or grooves combined with the rotational friction of the wheel back disk. Under this condition, the pressure drop rate of the wheel back leakage flow along the radial direction of the wheel disk will become faster or slower, so as to achieve a state of balance with the axial load adjustment generated by the pressure field of the working fluid at the impeller.

[0020] The present invention provides a method for regulating the axial force of an impeller machine. In the initial state, the left side of the rib structure should be in the same plane as the surface of the base, and after receiving the command of the control system, it can move axially under the traction of the rear connecting rod stretching device. After the axial movement, the rib structure can form a protrusion (pushing outward a certain distance) or a groove (dragging inward a certain distance) in the wheel back cavity. At this time, the leakage flow in the wheel back cavity is no longer a simple rotational Taylor-Couette flow, but a complex flow behavior under the action of the protrusion or groove combined with the rotational friction of the wheel back disk. In this case, the pressure drop rate of the wheel back leakage flow along the radial direction of the wheel disk will become faster or slower, thereby increasing or reducing the axial thrust generated by the wheel back cavity leakage flow, so as to achieve a state of balance with the axial load regulation generated by the pressure field of the working fluid at the impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of an embodiment of the present invention; Figure 2 This is a cloud diagram of the pressure field distribution of the wheel back cavity in an embodiment of the present invention (side view); Figure 3 This is a cloud diagram of the pressure field distribution of the wheel back cavity in an embodiment of the present invention (front view); Among them: 1-nozzle and its base, 2-casing, 3-turbine impeller, 4-main shaft, 5-bearing and thrust sensor, 6-adjustable rib structure, 7-power structure, 8-axial load monitoring equipment, 9-control system. DETAILED DESCRIPTION

[0022] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0023] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0024] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0025] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0026] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0027] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0028] Example 1 The present embodiment provides an impeller machine capable of increasing stability and reducing axial force, comprising a turbine impeller and a nozzle base, wherein the nozzle base is disposed on the back side of the turbine impeller, and a gap is provided between the back of the turbine impeller and the nozzle base; The nozzle base is provided with a groove arranged along its circumference, and an adjustment member for adjusting the fluid domain geometric space of the turbine impeller wheel back cavity is arranged in the groove.

[0029] The adjusting member comprises an adjustable rib-shaped structure and a power structure, and the power structure is arranged between the adjustable rib-shaped structure and the bottom of the groove.

[0030] Example 2 The present embodiment provides an impeller machine capable of increasing stability and reducing axial force, which comprises: a nozzle base 1, a casing 2, a turbine impeller 3, a main shaft 4, a bearing and a thrust sensor 5, an adjustable rib structure 6, a power mechanism 7, an axial load monitoring device 8 and a control system 9, wherein: The main shaft 4 is mounted with a turbine impeller 3, a casing 2 and a nozzle base 1, wherein the casing 2 is disposed on one side of the turbine blade 3, and the nozzle base 1 is disposed on the back side of the turbine impeller.

[0031] The nozzle base 1 is provided with a plurality of nozzles along its circumference, and the outlets of the plurality of nozzles face the blade side of the turbine impeller, so as to facilitate the supercritical carbon dioxide working fluid to enter from the radial direction of the turbine impeller 3 .

[0032] Gaps are arranged between the casing 2 , the turbine blades 3 and the nozzle base 1 .

[0033] A gap is provided between the turbine impeller 3 and the nozzle base 1 .

[0034] The nozzle base 1 is connected to the main shaft 4 via a bearing 5 .

[0035] The nozzle base 1 is provided with a groove arranged along its circumference, and the groove is provided with an adjustable rib structure 6 and a power structure 7. The adjustable rib structure 6 and the power structure 7 are placed in the groove provided on the nozzle base 1.

[0036] After entering the high-speed impeller machinery, the supercritical carbon dioxide working fluid first flows through the nozzle part. Under the guidance of the nozzle, the pressure energy of the working fluid is quickly converted into kinetic energy and enters the subsequent components. The working fluid is divided into three paths from the nozzle outlet. One path flows directly along the blade tip gap between the casing 2 and the turbine impeller 3 until the turbine outlet. The second path enters the main flow channel between the turbine blades 3. After sufficient expansion, the enthalpy of the working fluid is converted into shaft work output, and finally flows out from the turbine outlet in the axial direction; the third path leaks into the wheel back cavity. Under the rotational friction of the impeller disc back, the working fluid performs Taylor-Couette flow and finally leaks out in the opposite direction in the axial direction.

[0037] The nozzle and its base are mainly used for guiding the working medium and supporting the structure. The nozzle can change the velocity angle of the moving blade into which the working medium flows, and quickly convert the pressure energy into kinetic energy to drive the impeller to rotate and do work; the base at the rear provides improvement space for the adjustable rib structure and power structure, so that the geometric space of the fluid domain of the wheel back cavity can be adjusted; The turbine impeller is the core component to achieve functional conversion. Supercritical carbon dioxide high-temperature and high-pressure working fluid flows in radially, and after sufficient expansion, the enthalpy of the working fluid is converted into shaft work output, and the exhaust steam flows out axially. The main shaft, casing and other components are key parts of the turbine machinery, providing the most basic guarantee for basic functions and safety.

[0038] The bearing 5 is an angular contact ceramic ball bearing, located behind the turbine impeller, the stationary ring of the bearing 5 cooperates with the nozzle base 1, and the dynamic ring of the bearing 5 cooperates with the main shaft 4. A thrust sensor is placed between the inner ring of the bearing 5 and the main shaft to measure the axial load on this point.

[0039] The axial load monitoring device 8 performs visual reading processing on the signal result measured by the thrust sensor, and its upstream is connected to the thrust sensor so that the user can monitor the axial force change state in real time.

[0040] The control system 9 is connected to the axial load monitoring device 8 and the power structure 7, so that the user can appropriately adjust the structure of the wheel back cavity according to the axial force monitoring result to achieve the purpose of balancing the axial force.

[0041] The working principle of this embodiment is: The adjustable rib structure 6 and the power structure 7 are embedded in the nozzle base 1 and are located on the rear side of the wheel back cavity. In the initial state, the left side of the adjustable rib structure should be in the same plane as the surface of the nozzle base 1, and can move axially under the traction of the power structure after receiving the command of the control system. After the axial movement, the adjustable rib structure can form a protrusion (pushing outward a certain distance) or a groove (dragging inward a certain distance) in the wheel back cavity. At this time, the leakage flow in the wheel back cavity is no longer a simple rotational Taylor-Couette flow, but a complex flow behavior under the action of the protrusion or groove combined with the rotational friction of the wheel back disk. In this case, the pressure drop rate of the wheel back leakage flow along the radial direction of the wheel disk will become faster or slower, so as to achieve a state of balance with the axial load adjustment generated by the pressure field of the working fluid at the impeller.

[0042] When the high-speed impeller machinery starts working, the working fluid first flows through the nozzle part. Under the guidance of the nozzle, the pressure energy of the working fluid is quickly converted into kinetic energy and enters the subsequent components. The working fluid is divided into three paths from the nozzle outlet. One path flows directly along the blade tip gap between the casing and the turbine impeller until the turbine outlet. The second path enters the main flow channel between the turbine blades. After sufficient expansion, the enthalpy of the working fluid is converted into shaft work output, and finally flows out from the turbine outlet axially; the third path leaks into the impeller back cavity. Under the rotational friction of the impeller back, the working fluid flows in Taylor-Couette flow, and finally leaks out in the opposite direction axially. In this process, the axial load of the pressure field formed by the working fluid in the first and second paths is too different from the axial force formed by the leakage flow in the third path, which causes problems and risks in operation safety and stability. Since the flow paths of the first and second paths are closely related to the working performance of the turbine and will not be changed after the impeller design is completed, if the fluid domains of these two paths are adjusted, the turbine efficiency will be greatly reduced. Therefore, this embodiment can effectively avoid this problem while balancing the axial force by monitoring the axial resultant force and adjusting the fluid domain of the third leakage flow.

[0043] In order to verify whether there is any influence on the axial force, Figure 2 and Figure 3 This is the pressure field diagram of the new configuration. At the entrance of the wheel back cavity, a small range of pressure changes caused by the influence of backflow can still be observed. By observing the pressure field distribution in the wheel back gap and comparing it with the original configuration in Chapter 4, it can be found that the pressure decay is slower. At this time, the pressure at the exit of the wheel back cavity is 7.25716 MPa, which is about 1.80139 MPa higher than the original configuration, about 33.02% higher than the original basis.

[0044] Using the calculation function in ANSYS CFX-Post post-processing, the axial loads of each part on the impeller disk are calculated as shown in the following table. Obviously, the axial thrust of the main flow channel area on the impeller disk remains basically unchanged, the axial load generated by the leakage flow in the wheel back cavity increases, and the final balanced axial force is about 24.05% smaller than the prototype. Therefore, this configuration is effective.

[0045] Table 5-3 Axial loads of different surfaces subjected to corresponding flow channel fluids

[0046] Example 3 This embodiment provides a method for regulating the axial force of an impeller machine, based on the impeller machine described in Embodiment 1, comprising the following steps: In an initial state, a surface of the adjustable rib structure away from the power structure is flush with the surface of the nozzle base; After the impeller machinery starts running, the axial load of the set measuring point is obtained in real time; The movement of the adjusting member is controlled according to the obtained axial load, and the adjusting member is used to adjust the geometric space of the fluid domain of the turbine impeller back cavity, thereby achieving the purpose of balancing the axial force.

[0047] Example 4 Based on Example 2, this embodiment provides a method for regulating the axial force of an impeller machine, comprising the following steps: In the initial state, a surface of the adjustable rib structure 6 away from the power structure is flush with the surface of the nozzle base 1; After the impeller machinery starts running, the axial load of the set measuring point is obtained in real time; The movement of the power structure is controlled according to the obtained axial load, thereby driving the axial movement of the adjustable rib-shaped structure to achieve the purpose of balancing the axial force.

[0048] The working principle of this embodiment is: During the operation of the equipment, the axial load monitoring device will read the corresponding axial force data in real time through the thrust sensor and transmit it to the control system. Based on this, the control system will send a signal command to the power structure at the rear of the adjustable rib structure under manual operation or self-programming control. The adjustable rib structure and the power structure are embedded in the nozzle and its base, located at the rear side of the turbine impeller back cavity. In the initial state, the left side of the rib structure should be in the same plane as the surface of the base, and after receiving the command of the control system, it can move axially under the traction of the rear connecting rod tensioning device. After axial movement, the rib structure can form a protrusion (pushing outward a certain distance) or a groove (dragging inward a certain distance) in the wheel back cavity. At this time, the leakage flow in the wheel back cavity is no longer a simple rotational Taylor-Couette flow, but a complex flow behavior under the action of the protrusion or groove combined with the rotational friction of the wheel back disk. Under this condition, the pressure drop rate of the wheel back leakage flow along the radial direction of the wheel disk will become faster or slower, thereby increasing or decreasing the axial thrust generated by the wheel back cavity leakage flow, so as to achieve a state of balance with the axial load regulation generated by the pressure field of the working fluid at the impeller.

[0049] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An impeller machine capable of increasing stability and reducing axial force, characterized in that: It comprises a turbine impeller and a nozzle base, wherein the nozzle base is placed on the back side of the turbine impeller, and a gap is provided between the back of the turbine impeller and the nozzle base; The nozzle base is provided with a groove arranged along its circumference, and an adjustment member for adjusting the fluid domain geometric space of the turbine impeller wheel back cavity is arranged in the groove.

2. The impeller machine capable of increasing stability and reducing axial force according to claim 1, characterized in that: The adjusting member comprises an adjustable rib-shaped structure and a power structure, and the power structure is arranged between the adjustable rib-shaped structure and the bottom of the groove.

3. The impeller machine capable of increasing stability and reducing axial force according to claim 1, characterized in that: The turbine impeller and the nozzle base are both sleeved on the main shaft.

4. The impeller machine capable of increasing stability and reducing axial force according to claim 3, characterized in that: A plurality of nozzles are arranged on the nozzle base along its circumference, and the outlets of the plurality of nozzles face one side of the blade of the turbine impeller, so as to facilitate the supercritical carbon dioxide working fluid to enter from the radial direction of the turbine impeller.

5. The impeller machine capable of increasing stability and reducing axial force according to claim 3 or 4, characterized in that: The nozzle base is connected to the main shaft through a bearing.

6. The impeller machine capable of increasing stability and reducing axial force according to claim 5, characterized in that: A casing is mounted on the main shaft, and the casing is located at the blade side of the turbine impeller.

7. The impeller machine capable of increasing stability and reducing axial force according to claim 1, characterized in that: It also includes a control system, wherein the input end of the control system is connected to the load acquisition unit, and the output end of the control system is connected to the power structure.

8. The impeller machine capable of increasing stability and reducing axial force according to claim 7, characterized in that: The load collection unit is a thrust sensor, which is used to collect the axial load on the measuring point.

9. The impeller machine capable of increasing stability and reducing axial force according to claim 7 or 8, characterized in that: The load collection unit is also connected to an axial load monitoring device for visually reading the collected axial load.

10. A method for regulating the axial force of an impeller machine, characterized in that: The impeller machine according to any one of claims 1 to 9 comprises the following steps: In an initial state, a surface of the adjustable rib structure away from the power structure is flush with the surface of the nozzle base; After the impeller machinery starts running, the axial load of the set measuring point is obtained in real time; The movement of the adjusting member is controlled according to the obtained axial load, and the adjusting member is used to adjust the geometric space of the fluid domain of the turbine impeller back cavity, thereby achieving the purpose of balancing the axial force.

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