Variable geometry non-axisymmetric device for actively controlling turbine blade tip clearance

Abstract

The invention provides a variable geometry non-axisymmetric elastic device for actively controlling a turbine blade tip clearance. The variable geometry non-axisymmetric elastic device is composed of an elastic retaining ring, a micro motor, a lead screw, a clearance sensor and a displacement plate. The execution unit and the controller jointly form a control part, the elastic retaining rings are evenly arranged on the inner wall of the air cylinder, and the control part is connected with the movable ends of the retaining rings and used for controlling the displacement of the movable ends of the retaining rings in the radial direction so as to adjust the turbine blade tip gap size under different working conditions, and therefore the turbine blade tip gap size is always close to the optimal blade tip gap size. The deformation of the elastic retaining ring enables the whole annular surface formed by the elastic retaining ring and the inner wall of the air cylinder to present different non-axisymmetric space curved surface shapes. The variable geometry non-axisymmetric elastic retaining ring for actively controlling the turbine blade tip clearance has the following advantages of being high in response speed, simple in structure, convenient to install, low in cost, light in weight, high in reliability, easy to maintain, long in service life of components and the like.

Description

Technical Field

[0001] This invention relates to the field of rapid active control technology for turbine tip clearance of ground-based gas turbines, specifically a variable geometry non-axisymmetric elastic retaining ring for active control of turbine tip clearance. 1.2 Research Background and Significance

[0002] Gas turbines are hailed as the "jewel in the crown" of industry. This device, composed of a compressor, combustion chamber, and gas turbine, converts thermal energy into mechanical energy through air compression, fuel combustion, and exhaust gas expansion. The turbine, as a key component in the energy conversion process, directly affects the performance of the entire gas turbine system. To prevent frictional failure caused by contact between the turbine blades and the stationary endwalls, a certain clearance is unavoidable between the blade tips and the endwalls to ensure the long-term stable operation of the gas turbine unit.

[0003] During the operation of a gas turbine unit, the high-temperature mainstream flow in the turbine tip region flows from the pressure side to the suction side through the gap under the influence of pressure difference, forming a leakage flow. This part of the mainstream does no work, reducing turbine efficiency and also bringing more heat to the blade tip. Secondly, the blade tip leakage flow encounters the mainstream flow on the suction side and generates secondary flow downstream of the suction side, causing aerodynamic losses. Studies have shown that gap leakage flow affects the flow within approximately 70% to 100% of the blade height in the blade passage, resulting in more than one-third of the flow losses in the turbine originating from leakage flow in the blade tip gap. Furthermore, for every 1% increase in the ratio of blade tip gap to blade height, turbine efficiency decreases by 0.8% to 1.2%, and the corresponding fuel consumption rate increases by approximately 2%. Research by General Electric Company (GE) indicates that fuel consumption caused by turbine blade tip gap leakage accounts for approximately 67% of the total losses. Therefore, the design of turbine blade tips must not only ensure high cooling efficiency but also minimize leakage losses caused by leakage flow in the blade tip gap. This necessitates minimizing the blade tip gap as much as possible when designing gas turbines.

[0004] However, during the actual startup of a gas turbine, it needs to reach its maximum speed to generate maximum thrust. At this time, the rotating turbine blades are subjected to centrifugal force, causing the moving blades to elongate. Simultaneously, the high-temperature gas heats the moving blades and cylinders, and both the moving blades and cylinders exhibit thermal expansion and contraction. This expansion and contraction is often not synchronous; the stationary cylinder expands much slower than the moving blades, which undoubtedly reduces the tip clearance. Gas turbines prioritize long-term stable operation and maintenance costs. Therefore, the design considers uncertainties such as thermal expansion and mechanical wear, leaving sufficient clearance to accommodate these changes, ensuring the equipment's service life and ease of maintenance. For a period after startup, the rotor continues to expand and eventually reaches a stable state, while the cylinder continues to expand, causing the tip clearance to gradually increase. After stable operation, the thermal and mechanical loads acting on the rotor and cylinder remain essentially constant, and their expansion reaches equilibrium, resulting in a relatively constant tip clearance. However, due to the relatively large clearance reserved in the design, the clearance at stable operation will not be small. Furthermore, changes in the operating conditions and loads of the gas turbine, as well as factors such as corrosion and wear during long-term operation, can also cause changes in the blade tip clearance. These factors combined make the variation in blade tip clearance height more complex and difficult to predict. Therefore, it is crucial to develop a control system that can monitor the size of the turbine blade tip clearance and then reduce it through control components.

[0005] In addition, modern gas turbine aerodynamic design and testing methods can achieve turbine efficiency of over 90%. It is very difficult to further improve the efficiency of gas turbines by improving aerodynamic design. Therefore, in order to further improve the performance of gas turbines, it is essential to design a system to control the turbine blade tip clearance.

[0006] Therefore, in response to this situation, this invention proposes a variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine tip clearance in ground-based gas turbines. The structural characteristics of the non-axisymmetric toroidal surface generated after the elastic retaining ring deforms are utilized to reduce tip clearance leakage flow. This invention improves and develops the rapid active control system for gas turbine tips, and provides new ideas for the design and optimization of turbine tip clearance control structures in my country's gas turbines. 1.3 Current Status of Research at Home and Abroad

[0007] In the design of gas turbine engines, the sealing technology for the blade tip and endwall clearance plays a crucial role. As early as the 1960s and 70s, research on the leakage characteristics of turbine blade tip clearances began abroad, and corresponding control methods were explored. These findings were applied to both civilian and military applications, primarily by Pratt & Whitney, GE, and Rolls-Royce. Domestic research on the leakage characteristics and control methods of turbine blade tip clearances began as early as the 1990s. However, with increasing national attention over the past two decades, related research has only recently gained traction with research institutes and universities, and has developed rapidly in recent years. Nevertheless, there is still a gap between current research and mature engineering applications.

[0008] Currently, turbine blade tip clearance control technology mainly encompasses two major areas: passive clearance control and active clearance control. Passive clearance control refers to maintaining a small clearance between the turbine blade and the casing through design and material selection, without involving real-time dynamic adjustments. This control method is simple and low-cost, but it cannot cope with clearance changes caused by factors such as temperature variations and mechanical wear during operation. In contrast, active clearance control involves real-time monitoring and dynamic adjustment of the clearance between the turbine blade and the endwall. This is typically achieved through the use of control components and actuators, which can automatically adjust the clearance size according to the turbine's operating state and environmental conditions to maintain optimal performance and efficiency. Although active control methods are technically complex and more expensive, they can significantly improve turbine performance and reliability.

[0009] Passive clearance control primarily involves reducing the clearance between the blade tip and the casing through special structures such as minimizing assembly clearance, using double-layer casings, and employing wear-resistant coatings. Alternatively, it may involve using alloy materials with low linear thermal expansion coefficients to construct the casing, thereby reducing blade tip clearance under specific operating conditions. The former method relies heavily on material properties and the stress conditions between the rotor and casing under various operating conditions to design the optimal clearance control structure. For example, Pratt & Whitney's JT8D uses a nickel-chromium polyester wear-resistant material sprayed onto the outer ring of the high-pressure compressor. As the rotor blades rotate, the annular grooves worn by the blades on the outer ring reduce the clearance. Rolls-Royce's RB211 employs a double-layer casing structure. The inner casing, which maintains the airflow channel, only bears aerodynamic loads, while the outer casing bears and transmits structural loads. The more rigid outer casing experiences less deformation, allowing the RB211 to maintain a uniform blade tip clearance during flight. The latter belongs to the passive thermal deformation control system. It designs engine components with different expansion rates according to the temperature changes during engine operation to achieve precise matching of expansion between the rotor and stator, thereby controlling the blade tip clearance. However, unlike the thermal deformation control in active clearance control, this method can only be used under a certain fixed operating condition and cannot be adjusted according to the engine's operating conditions, thus limiting the wide application of this method.

[0010] Active clearance control mainly includes three categories: active pressure clearance control, thermal deformation clearance control, and mechanical clearance control. Active pressure clearance control uses compressor bleed air to control blade tip clearance. It utilizes the pressure difference between the compressor bleed air and the combustion gas at the blade tip to induce radial displacement of the turbine outer ring. For example, when designing the high-pressure turbine assembly of the E3 engine, GE introduced compressed gas from the bypass duct and adjusted the gas supply according to engine operating conditions to ultimately regulate casing temperature and thermal deformation, achieving a blade tip clearance control target of 0.41 mm during cruise. However, the actuators in the active pressure control system are very sensitive to pressure changes and are subject to high-cycle fatigue. Clearance control requires a large amount of bleed air from the compressor, which has no work capacity, thus reducing engine efficiency to some extent.

[0011] Since the 1960s and 70s, Active Thermal Clearance Control (ATCC) was once the mainstream turbine tip clearance control technology. It adjusts the clearance size by regulating the thermal deformation of the casing, thereby effectively reducing tip leakage. This method can also adjust asymmetric clearances, compensating for the shortcomings of traditional clearance control methods, and has therefore been widely used. Engines such as GE's GE90, Pratt & Whitney's JT9D-59 / 70, PW2000 and PW4000 series, and International Aero Engines' V2500 have all adopted ATCC to achieve active control of tip clearance. my country's aviation industry developed relatively late, but with the increasing emphasis placed on aviation in recent years, some progress has been made in ATCC. For example, Nanjing University of Aeronautics and Astronautics has built an ATCC test bench in its School of Energy and Power Engineering and conducted extensive experimental research; many other scholars have also conducted experiments, simulations, and theoretical analyses related to thermal deformation. The research mainly focuses on the casing temperature distribution and deformation during the operation of the ATCC control system, and analyzes the radial deformation deviation of the casing. However, the working mechanism of the active thermal deformation clearance control system in real-world environments is quite complex, involving comprehensive issues such as gas flow and distribution during the thermo-fluid-structure interaction analysis of the casing, impact heat transfer and deformation on the casing surface, and engine wear. Furthermore, the active thermal deformation clearance control method typically uses the blade tip clearance value as the feedback quantity (and in some cases, even no feedback is provided). This means that it cannot take into account these complex factors in the engine, and its slow operation makes it unable to quickly respond to sudden changes in conditions.

[0012] Furthermore, NASA's Green Research Center has developed a novel active thermal deformation clearance control system based on high-temperature shape memory alloys (SMAs). SMA clearance control is a scheme that uses shape memory alloys as the driving force to adjust blade tip clearance. This clearance control scheme offers a faster response, overcoming the shortcomings of traditional active pressure and thermal deformation clearance control systems, such as excessive consumption of compressed gas and slow response. It also boasts a simple structure; by applying appropriate excitation to the shape memory alloy, it can deform, ultimately achieving a wide range of blade tip clearance adjustment. Common shape memory alloys include thermo-induced, photo-induced, magneto-induced, and electro-induced types. Schetky et al. were among the first to conduct related research, proposing a blade tip clearance control scheme using a specific axial-flow engine as a case study, as shown. They designed a segmented O-shaped SMA ring and placed it inside the casing. At high temperatures, the SMA ring can shrink to reduce the blade tip clearance; at low temperatures, it can return to its original state through an elastic ring inside the SMA ring, thus achieving blade tip clearance control. Domestic research on blade tip clearance control based on SMAs has also been conducted, focusing primarily on the construction of clearance control schemes and theoretical analysis. Zhang Xueren et al. from Beijing University of Aeronautics and Astronautics proposed a compressor tip clearance control scheme based on the self-recovery characteristics of SMA, as shown in the figure. This structure can adaptively control the compressor tip clearance according to the changes in engine operating state.

[0013] Experiments show that the SMA (Screen Memory Alloy) clearance control method can improve compressor efficiency by 0.8% and reduce fuel dissipation rate by 0.2%–0.4%. However, this method not only requires precise knowledge of the tip clearance variation beforehand, but is also extremely expensive. Domestic and international research on SMA-based tip clearance control schemes has only proposed some relatively advanced ideal structures, which still have many theoretical shortcomings. In particular, research on the temperature-clearance matching relationship is not yet mature, and corresponding experimental research has not yet begun. Therefore, active tip clearance control based on high-temperature shape memory alloys has not been widely promoted and applied in general turbomachinery.

[0014] Mechanical active clearance control mainly includes connecting devices and driving devices, such as hydraulic, electromechanical, and electromagnetic systems. Compared with the thermal deformation method, mechanical control offers faster response, higher control precision, and a more compact structure. Since it eliminates the need for intermediate air extraction, it has minimal negative impact on unit performance. It has been reported that Rolls-Royce's RB211 engine used a hydraulic actuator to control the forward and backward movement of the conical casing to achieve active control of blade tip clearance. NASA has independently developed a mechanical active turbine blade tip clearance control system based on a hydraulic servo device and verified its feasibility on a real unit. Qi Xingming invented a novel design scheme for a rapid active turbine blade tip clearance control system, as shown. This scheme uses a mechanical actuator with an adjusting plate and sealing plate in the inner casing, and actively controls the turbine blade tip clearance through a clearance sensor and control unit. Zhang Xiaodong et al. invented an electromechanical actuation device for actively controlling turbine blade tip clearance, as shown. This device utilizes the inverse piezoelectric phenomenon of a piezoelectric crystal—that is, when subjected to an electric field, the piezoelectric crystal deforms, driving the pressure input rod of a hydraulic amplifier to move a diaphragm, thereby controlling the blade tip clearance. However, most of the above active mechanical control systems have relatively complex structures, which increases the weight of the engine and the difficulty of assembly. What is even more challenging is that the mechanical device must operate at high temperatures for a long time, which is a problem that the system must face and solve.

[0015] Currently, the commonly used method in my country's mechanical active clearance control technology is to completely deform the inner casing to reduce clearance. However, this control method generates significant local stress at certain deformation locations, compromising safety and affecting operational stability and lifespan. Therefore, this paper proposes an innovative structural design that aims to respond quickly to clearance changes while reliably reducing clearance. Through this improvement, we hope to bring new breakthroughs to mechanical active clearance control technology, further enhancing the overall performance and reliability of machinery.

[0016] As the above introduction demonstrates, research on blade tip clearance both domestically and internationally covers a wide range of topics and is of paramount importance for improving the reliability and economy of gas turbines. Although my country has been researching active control of gas turbine blade tip clearance for decades, with the increasing demands of national defense and power generation, further improving gas turbine efficiency is urgently needed. This efficiency improvement is inseparable from precise control of blade tip clearance. In-depth exploration and research into blade tip clearance control technology will have a profound impact on promoting technological progress and practical applications in related fields. Summary of the Invention

[0017] The technical problem to be solved:

[0018] To address the problems existing in the prior art, this invention proposes a variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance.

[0019] Technical solution

[0020] The technical solution of this invention is as follows:

[0021] The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized by comprising: a rotor, rotor blades, an elastic retaining ring, a cylinder, cooling holes, a clearance sensor, a micro motor, a lead screw, a fixed end of the retaining ring, a movable end of the retaining ring, and a displacement plate; multiple rotor blades are distributed circumferentially along the rotor; the micro motor is fixed inside the cylinder groove, and the output shaft of the micro motor is set as a lead screw, which can move repeatedly and has an internal limiter to prevent excessive displacement from contacting the rotating blade; the elastic retaining ring is fixed to the cylinder by the fixed end of the retaining ring, one end of the displacement plate is connected to the lead screw driven by the micro motor, and the other end is embedded in the movable end layer of the elastic retaining ring, which can drive the movable end of the retaining ring to move radially elastically; the clearance sensor is located at the location of the maximum displacement of the movable end of the retaining ring and is directly opposite the blade tip, used to detect the size of the blade tip clearance at its current position.

[0022] The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized in that: the width of the elastic retaining ring is greater than the chord length of the rotor blade, and the area covered can range from 0.5 times the chord length in front of the leading edge to 0.5 times the chord length behind the trailing edge.

[0023] The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized in that: the micro motor is composed of three layers of materials, the middle layer is made of heat-insulating material, and the outer layer is made of heat-resistant alloy material, which ensures the strength and rigidity requirements of the shell and prevents high temperature from affecting the micro motor.

[0024] The variable geometry non-axisymmetric elastic retainer ring for actively controlling turbine blade tip clearance is characterized in that: each elastic retainer ring is equipped with a high-sensitivity sensor and controller at its location, which can monitor the turbine blade tip clearance size and the deformation of the elastic retainer ring in real time, and calculate the optimal control strategy through advanced control algorithms.

[0025] The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized in that: the cylinder is made of a high-strength, high-temperature resistant, and low-thermal-expansion-coefficient material to ensure that it can maintain good mechanical properties under high-temperature and high-stress environments.

[0026] The variable geometry non-axisymmetric elastic retainer ring for actively controlling turbine blade tip clearance is characterized in that: the elastic retainer ring is made of a high-strength, high-temperature resistant, elastic, and low thermal expansion coefficient material to ensure that it can maintain good mechanical properties and elasticity under high temperature and high stress environments.

[0027] The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized in that: the lead screw and the displacement plate are made of heat-resistant alloy by casting or forging, the displacement plate on the lead screw can move back and forth, and the lead screw is provided with a limiter to limit the maximum displacement of the movable end of the retaining ring to move inward.

[0028] The aforementioned variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance is characterized by: the elastic retaining rings being uniformly distributed on the cylinder, with the specific number of retaining rings depending on the ideal operating conditions of different gas turbines. The optimal number is 8 to 12 rings. Multi-point active control technology is implemented through an actuator, using multiple independent elastic retaining rings to achieve non-axisymmetric deformation of the entire ring surface for precise adjustment of the blade tip clearance.

[0029] Beneficial effects

[0030] This invention employs an elastic retaining ring as a key component, proposing a variable geometry non-axisymmetric elastic retaining ring for active control of turbine tip clearance. Compared to passive clearance control, this invention is applicable to various operating conditions, can sense clearance size, and has a fast response speed. Compared to traditional thermal deformation clearance control, this invention does not generate large temperature differences, thus avoiding increased thermal stress between the cylinder and the elastic retaining ring. Compared to active pressure clearance control, this invention does not consume a large amount of cooling gas from the compressor section, does not significantly impact unit performance, and improves the efficiency of the entire gas turbine system. Compared to traditional active mechanical clearance control, this invention is lower in cost, simpler in system, lighter in weight, does not negatively affect the important performance characteristics of the gas turbine, is easier to install, easier to design, and has good reliability. It does not require complete deformation of the cylinder inner ring and can be used for cylinder non-axisymmetric deformation clearance control. This breakthrough provides a new design concept for the design of active mechanical turbine tip clearance control in gas turbines, bringing more possibilities and flexibility.

[0031] Traditional cylinder designs by engineers are often constrained by axisymmetric geometry, which to some extent limits performance improvements and room for innovation. Non-axisymmetric elastic retaining rings can better adapt to complex load distributions, reduce stress concentration, thereby extending equipment lifespan and achieving higher efficiency, better performance, and optimized weight distribution. Furthermore, this design simplifies the production and assembly process, reduces production costs, and improves production efficiency. This innovation not only solves problems existing in current technologies but also provides new ideas for the development of mechanical active clearance control technology, promoting technological progress in mechanical design and bringing new opportunities to related industries. In the future, we plan to apply this technology to more gas turbine models to improve overall performance and safety. Attached Figure Description

[0032] The accompanying drawings illustrate exemplary embodiments of the invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification.

[0033] Figure 1 This is an exemplary three-dimensional structural diagram of the present invention.

[0034] Figure 2 This is an exemplary cross-sectional structural diagram of the present invention.

[0035] Figure 3 This is a schematic cross-sectional view of the deformation of the movable end of the elastic retaining ring of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Rotor 2. Rotor blades 3. Protective ring fixing end

[0038] 4. Cylinder 5. Elastic retaining ring 6. Cooling holes

[0039] 7. Miniature motor 8. Lead screw 9. Gap sensor

[0040] 10. Displacement plate 11. Moving end of retaining ring Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Currently, in the field of turbines with rotor blades 2 and cylinders 4, the cylinder 4 is generally cast or forged from pure metal or other alloys, with a certain gap between the rotor blade tip and the cylinder wall, known as the tip clearance. The size of the tip clearance has a certain impact on the efficiency of the gas turbine; a smaller tip clearance corresponds to a higher turbine efficiency. However, due to machining errors, assembly errors, and different operating conditions, the turbine is often not in the optimal tip clearance state, or it only maintains the optimal tip clearance in the initial stage of use, and then the tip clearance changes and deviates from the optimal state. Therefore, this invention adds an elastic retaining ring 5 structure to the turbine cylinder, aiming to solve or at least alleviate at least one of the above-mentioned technical problems, and discloses a tip clearance structure and control method of a variable geometry non-axisymmetric elastic retaining ring for actively controlling the turbine tip clearance.

[0044] A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance includes a rotor 1, rotor blades 2, a cylinder 4, an elastic retaining ring 5, cooling holes 6, and an actuator unit: a micro motor 7, a lead screw 8, a clearance sensor 9, and a displacement plate 10. The actuator unit and the controller together constitute the control component. The rotor 1 can rotate around an axis, the direction of which is called the axial direction of the rotor 1, and the direction that extends radially outward from the axis is called the radial direction of the rotor 1. Multiple rotor blades 2 are evenly distributed along the circumference of the rotor 1. The rotor blades 2 have a root, a blade body, and a tip; the root is fixed to the rotor 1, and the blade body extends in a certain spatial curved surface form along the radial direction of the rotor 1. The tip is located at the outermost radial direction of the rotor blade 2, and the rotor blades 2 rotate around the axis together with the rotor 1. When the rotor 1 drives the rotor blades 2 to rotate, the movement trajectory of the tips of multiple rotor blades 2 will form a circular curved surface, and the distance between this circular curved surface and the elastic retaining ring 5 is the tip clearance. The cylinder 4 has a recessed groove to accommodate the actuator and includes a cooling channel for the intake of high-pressure cooling gas from the compressor section. The gas exits through cooling holes 6 within the groove, cooling the cylinder 4, the elastic retaining ring 5, and the actuator, thus providing mechanical safety protection. The inner wall of the cylinder 4, located radially near the blade tip, has a structure matching the retaining ring fixing end 3 for securing the elastic retaining ring 5. The elastic retaining ring 5 is flexible and can be bent. It is fixed to the inner wall of the cylinder 4 by the retaining ring fixing end 3. The width of the elastic retaining ring 5 is greater than the chord length of the rotor blade 2, covering an area from 0.5 times the chord length in front of the leading edge to 0.5 times the chord length behind the trailing edge. In this text, "inner side" refers to the radial direction approaching the rotor blade 2, and "outer side" refers to the radial direction away from the rotor blade 2.

[0045] Cylinder 4 is made of high-strength, high-temperature resistant, and low-thermal-expansion-coefficient material to ensure good mechanical performance under high-temperature and high-stress conditions. The elastic retaining ring 5 is also made of high-strength, high-temperature resistant, elastic, and low-thermal-expansion-coefficient material to ensure good mechanical performance and elasticity under high-temperature and high-stress conditions. The micro-motor 7 housing consists of three layers. The outer two layers are made of the same alloy material to ensure the strength and rigidity requirements of the enclosure. The middle layer is a heat-insulating material because even with cooling gas passing through the cylinder 4, the temperature reaches approximately 600℃. To ensure stable operation of the motor, heat insulation measures are needed to reduce the impact of the high temperature inside the cylinder 4 on the micro-motor 7. The micro-motor 7 is fixedly connected to the internal groove of the cylinder 4. A small gap is left between the movable end 11 of the retaining ring and the cylinder groove to allow for radial displacement of the movable end 11.

[0046] When this device is in operation, the micro motor 7 is activated by the controller to rotate the lead screw 8, which in turn drives the displacement plate 10 embedded in the movable end 11 of the retaining ring to move the movable end 11 of the retaining ring radially inward. This causes the movable end 11 of the retaining ring to undergo elastic deformation inward, thereby reducing the turbine blade tip clearance. The lead screw 8 and the displacement plate 10 are made of heat-resistant alloy by casting or forging. The displacement plate on the lead screw can move back and forth, and the lead screw is equipped with a limiter to limit the maximum displacement of the movable end 11 of the retaining ring inward. In the event of a sudden failure of the control system, it can limit the movable end 11 of the retaining ring from moving too downward, thus preventing excessively small blade tip clearance, friction failure caused by contact between the rotor blade tip and the movable end 11 of the retaining ring, and serious accidents caused by broken turbine blades.

[0047] In this scheme, the scope of the control components includes the supporting components required to cause displacement or deformation of the movable end 11 of the retaining ring, such as a controller (the controller can be set in different positions, so it is not shown in the figure) that judges and calculates when deformation occurs and how much deformation occurs, and detection components (such as gap sensors) that transmit the required signals to the controller.

[0048] The gap sensor 9 is positioned on the side of the retaining ring's movable end 11 with the largest deformation, directly facing the blade tip, and is connected to the controller. It detects the size of the blade tip gap and transmits the detection signal to the controller, which then adjusts the control components based on the detected gap, thereby regulating the blade tip gap. Currently, gap sensors utilize various working principles, including capacitance, eddy current, optical, and microwave methods, all of which have been applied to the detection of turbine blade tip gaps. For example, a microwave gap measurement sensor operates on the principle of electromagnetic induction. Its basic structure consists of a transmitter and a receiver. The transmitter emits an electromagnetic wave that propagates through the air. When it encounters the blade tip, a portion of the wave is reflected back, and this reflected wave is received by the receiver. The receiver measures the intensity and duration of the reflected electromagnetic wave, and from this data, the distance between the blade tip and the sensor can be calculated. As the distance between the object and the sensor changes, the intensity and duration of the reflected electromagnetic wave also change. Therefore, the gap measurement sensor can measure the distance between the blade tip and the sensor, i.e., the distance between the blade tip and the retaining ring's movable end 11, in real time.

[0049] Furthermore, in this invention, the inner wall portion of the cylinder 4 used to fix the retaining ring fixing end 3 can be coupled with the retaining ring fixing end 3 in various ways, such as countersunk bolt threaded connection, countersunk bolt threaded connection, etc., so they are not shown in the figure.

[0050] Furthermore, in this invention, each elastic retaining ring 5 corresponds to a set of execution units. Multiple sets of execution units individually control the gap size at the position of each elastic retaining ring 5 through a controller. The deformation of the elastic retaining ring 5 causes the entire annular surface formed by the elastic retaining ring 5 and the inner wall of the cylinder 4 to exhibit different non-axisymmetric spatial curved surface shapes. A schematic diagram of the deformation of each elastic retaining ring 5 is shown below. Figure 3 As shown, the dashed line represents the position of the movable end 11 of the elastic retaining ring after it has deformed to a certain value. In this implementation scheme, the thickness of a single elastic retaining ring 5 can be reasonably determined according to the design, ensuring the accuracy of local or overall control over the blade tip clearance.

[0051] Furthermore, in practical applications, an appropriate number of elastic retaining rings can be selected for different types of gas turbines and installed in a symmetrical distribution, with the optimal number being 8 to 12. Driving any one of the actuators can change the tip clearance in the corresponding direction, thus achieving tip clearance control.

[0052] Optionally, for the different implementation methods described above, the micro motor 7 can be replaced with an electromagnetic actuator. The drive shaft of the electromagnetic actuator is a lead screw, and the other end of the electromagnetic actuator is fixed in the groove of the cylinder 4, so that the axis of the lead screw is perpendicular to the wall of the movable end 11 of the retaining ring. The displacement plate 10 uses a nut that mates with the lead screw. The electromagnetic actuator drives the lead screw to rotate, causing the displacement plate 10 to reciprocate along the axis of the lead screw, thereby moving the movable end 11 of the retaining ring. The control terminal of the electromagnetic actuator is connected to a controller, which controls the operation of the electromagnetic actuator.

[0053] Furthermore, in one alternative embodiment of the control component, the displacement plate 10 can be a flat plate in various shapes such as rectangle, rhombus, or pentagon. The displacement plate 10 can also be implemented in various ways, but a common feature of different embodiments is that it is connected to or in contact with the movable end 11 of the retaining ring, and the movable end 11 of the retaining ring is displaced or deformed radially by applying a force to it.

[0054] For the different implementation methods described above, multiple sets of cooling holes and cooling channels can be designed. The shapes of the cooling holes can also be varied; this invention uses a cylindrical air film hole as an example. Other shapes include fan-shaped holes, arrow-shaped holes, and tripod holes.

[0055] Furthermore, in an optional embodiment of this invention, the positions of the movable end 11 and the fixed end 3 of the retaining ring can be interchanged, such as... Figure 1 That is, the groove inside the actuator and cylinder 4 is on the right side of the retaining ring fixing end 3. After the switch, the groove inside the actuator and cylinder 4 is on the left side of the retaining ring fixing end 3. Both the structure shown in the figure and the structure shown in the figure can achieve the effect of actively controlling the blade tip gap.

[0056] The blade tip clearance control system of this invention uniformly arranges elastic retaining rings 5 ​​on the inner wall of the cylinder 4, forming a blade tip clearance between the elastic retaining rings 5 ​​and the blade tips of the rotor blades 2. A control component connected to the movable end 11 of the retaining ring controls the deformation of the movable end 11 to adjust the size of the blade tip clearance. This solution makes it possible to achieve and maintain the optimal blade tip clearance according to operating conditions, solving the problem in existing technologies where, due to machining errors, assembly errors, and varying operating conditions, the gas turbine is not in the optimal blade tip clearance state, or only maintains the optimal blade tip clearance in the initial stage of use, subsequently deviating from the optimal state. By replacing the complete deformation of the inner wall surface in traditional mechanical active clearance control with the partial deformation of the elastic retaining ring 5, the working stability and reliability of the rotor blades 2 and the elastic retaining ring 5 are enhanced, ensuring the working margin of the blade tip clearance and the service life of the system. This invention can be used not only in axisymmetric deformation clearance control of the cylinder 4 but also in non-axisymmetric deformation clearance control of the cylinder 4. The control method of this invention can dynamically control the size of the blade tip clearance, ensuring that the turbine is always within the minimum allowable error range of the blade tip clearance, thereby increasing the efficiency of the gas turbine under different operating conditions and reducing blade tip leakage losses.

[0057] It should be noted that, in this application, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance, comprising: The rotor can rotate around an axis, with multiple rotor blades evenly distributed circumferentially around the rotor, rotating in a circle with the rotor around the axis. The cylinder has internal grooves to accommodate the actuator and internal cooling channels for introducing cooling gas from the compressor section, which exits through cooling holes inside the grooves to cool components such as the micro-motor and lead screw. The cylinder inner wall has a structure matching the retaining ring fixing end to secure the elastic retaining ring. The elastic retaining ring is flexible and can be bent; it is fixed to the cylinder inner wall by the retaining ring fixing end. Multiple elastic retaining rings are evenly arranged around the multiple blades, with a tip gap between the elastic retaining ring and the blade tips. The actuator consists of a micro-motor... The actuator consists of a micro motor, a lead screw, a gap sensor, and a displacement plate. The micro motor in each actuator is fixed within a cylinder groove. One end of the displacement plate in the actuator is embedded in the movable end of the retaining ring, and the other end is connected to the output shaft (lead screw) of the micro motor. This displacement plate controls the radial deformation of the movable end of the retaining ring to adjust the size of the blade tip gap. A control component comprises multiple actuators and a controller. The controller connects to the multiple actuators and controls their actions. The controller generates a fluctuation control signal based on the blade tip gap information transmitted by the gap sensor. The actuators control the radial direction and displacement of the movable end of the retaining ring based on this fluctuation control signal.

2. The variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 1, characterized in that: The width of the elastic retaining ring is greater than the chord length of the rotor blade, and the area it covers can range from 0.5 times the chord length in front of the leading edge to 0.5 times the chord length behind the trailing edge.

3. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 1 or 2, characterized in that: The micro motor is composed of three layers of materials: the middle layer is made of heat-insulating material, and the outer layer is made of heat-resistant alloy material. This ensures the strength and rigidity of the shell while preventing high temperatures from affecting the micro motor.

4. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 3, characterized in that: The cylinder is made of high-strength, high-temperature resistant, and low-thermal-expansion-coefficient materials to ensure that it can maintain good mechanical properties under high-temperature and high-stress environments.

5. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 4, characterized in that: Each elastic retaining ring is equipped with a highly sensitive sensor and controller, which can monitor the turbine blade tip clearance and the deformation of the elastic retaining ring in real time, and calculate the optimal control strategy through advanced control algorithms.

6. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 5, characterized in that: The elastic retaining ring is made of high-strength, high-temperature resistant, elastic, and low thermal expansion coefficient material to ensure that it can maintain good mechanical properties and elasticity under high temperature and high stress environments.

7. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 6, characterized in that: The lead screw and displacement plate are made of heat-resistant alloy by casting or forging. The displacement plate on the lead screw can move back and forth, and the lead screw is equipped with a limiter to limit the maximum displacement of the moving end of the retaining ring to the inward side.

8. A variable geometry non-axisymmetric elastic retaining ring for actively controlling turbine blade tip clearance according to claim 7, characterized in that: For different types of gas turbines, an appropriate number of elastic retaining rings can be selected and installed in a symmetrical and evenly distributed manner. The optimal number of rings is 8 to 12.

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