A test bench for testing the dynamic stiffness of a squirrel cage elastic support based on a rotary exciter

Abstract

This invention relates to a test bench for testing the dynamic stiffness of a squirrel cage elastic support based on a rotary exciter, comprising: a support, a bracket, a fixed ring, a rotary exciter, and an eddy current displacement sensor; the support is used to support the squirrel cage, the rotary exciter, and the eddy current displacement sensor; the fixed ring has threaded holes in both the axial and radial directions, the outer surface of the fixed ring is clearance-fitted with the inner surface of the squirrel cage, and the fixed ring and the squirrel cage are assembled using a hexagonal set screw passing through the radial threaded hole of the fixed ring; the rotary exciter and the fixed ring are assembled using a hexagonal screw and a spring washer passing through the axial threaded hole of the fixed ring; the bracket is mounted on the support, and the eddy current displacement sensor passes through the bracket and is placed at the center of the outer surface of the squirrel cage, used to detect the displacement signal of the squirrel cage under the action of the rotary exciter, and outputs the signal to an external signal acquisition system for subsequent data acquisition and analysis.

Description

Technical Field

[0001] This invention relates to a dynamic stiffness measuring device for a squirrel cage elastic support based on a rotary exciter, belonging to the technical field of rotor system design. Background Technology

[0002] During operation, gas turbine rotors may pass through critical speeds. At this point, the rotor system will resonate, and strong resonance can lead to damage to the rotating machinery.

[0003] Squirrel-cage elastic supports can reduce the system's support stiffness by designing cage bars with lower stiffness, thereby altering the critical speed of the rotor support system and avoiding the resonance range of rotating machinery. Measurement of the dynamic stiffness of squirrel-cage elastic supports can provide a basis for determining the resonance range of rotating machinery. Current methods for measuring the dynamic stiffness of squirrel-cage supports include applying excitation force using a rotating shaft, but high-speed shafts present safety and unbalanced force measurement challenges. Alternatively, two mutually perpendicular exciter structures can be used to simulate shaft motion, but this has drawbacks such as difficulty in simulating the actual operating conditions of rotating machinery. Summary of the Invention

[0004] The technical problem solved by this invention is to address the safety issues and difficulty in measuring unbalanced forces in existing squirrel cage dynamic stiffness measuring devices that use high-speed rotating shafts, and to provide a dynamic stiffness measuring device based on a squirrel cage elastic support using a rotary exciter.

[0005] The solution of the present invention is: a test bench for testing the dynamic stiffness of a squirrel cage elastic support based on a rotary exciter, comprising: a support, a bracket, a fixing ring, and an eddy current displacement sensor;

[0006] The bracket supports the squirrel cage, rotary vibrator, and eddy current displacement sensor. The fixing ring has threaded holes in both the axial and radial directions. The outer surface of the fixing ring is clearance-fitted with the inner surface of the squirrel cage, and a hexagonal set screw passes through the radial threaded hole of the fixing ring to assemble the fixing ring and the squirrel cage. A hexagonal screw and a spring washer pass through the axial threaded hole of the fixing ring to assemble the rotary vibrator and the fixing ring. A bracket is mounted on the bracket, and the eddy current displacement sensor passes through the bracket and is placed at the center of the outer surface of the squirrel cage. It is used to detect the displacement signal of the squirrel cage under the action of the rotary vibrator and outputs the signal to an external signal acquisition system for subsequent data acquisition and analysis.

[0007] Preferably, the bracket is composed of a base plate 1, a reinforcing plate 1, a seat plate, an upright plate 1, a reinforcing plate 2, a reinforcing plate 3, and an upright plate 2.

[0008] The base plate is symmetrically provided with multiple U-shaped holes, which are fixed to the test platform by anchor bolts, thereby ensuring the stability of the entire rat cage stiffness test bench. The reinforcing plate I is provided with a welding bevel, with its bottom surface in contact with the base plate and its side surface in contact with the upright plate II. The base plate, upright plate II and two symmetrically arranged reinforcing plates I are combined by welding. The lower surface of the seat plate is corner-welded to the upright plate II and the reinforcing plate III. The upper surface of the seat plate is corner-welded to the upright plate I and the reinforcing plate II. The base plate and the seat plate are installed on opposite sides of the upright plate II.

[0009] Preferably, the upright plate I is a rectangular plate with a circular hole of a certain diameter in the center. The size of the circular hole is matched with the clearance of the rat cage so that the rat cage can pass through the upright plate I. The circular array of threaded holes around the circular hole is used for assembly connection with the rat cage flange. At the same time, threaded holes are symmetrically provided on the wall of the upright plate for connection with the bracket.

[0010] Preferably, the bracket is an assembly formed by welding a support plate and a connecting plate; the connecting plate is symmetrically provided with two threaded holes, and the bracket is connected to the upright plate I in the bracket by using hexagonal socket screws.

[0011] Preferably, the number of eddy current displacement sensors is one or two. When it is necessary to determine the influence of the anisotropy of the squirrel cage on the dynamic stiffness, two sensors are set at 90 degrees to each other to measure the displacement in two directions respectively, so as to realize the simultaneous measurement of the dynamic stiffness of the squirrel cage in two directions. The eddy current displacement sensors are connected to the bracket by threads and fixed with nuts. During the welding process, the center line of the bracket is ensured to pass through the exact center of the squirrel cage.

[0012] Preferably, the rotary exciter is used to generate excitation force to replace the rotor for testing. A force sensor inside the rotary exciter is used to collect force signals. The stiffness of the squirrel cage is obtained by using the magnitude of the force of the rotary exciter and the displacement amplitude signal obtained by the eddy current displacement sensor.

[0013] The advantages of this invention compared to the prior art are:

[0014] This invention presents a test bench for testing the dynamic stiffness of a squirrel cage's elastic support, based on a rotary exciter. The squirrel cage, rotary exciter, and eddy current displacement sensor are connected and fixed using components such as a bracket and fixing rings. An adjustable imbalance is added inside the rotary exciter, and the magnitude of the imbalance force applied to the squirrel cage is obtained through a force sensor within the exciter. The displacement signal of the squirrel cage is monitored, acquired, and analyzed using the eddy current displacement sensor and a data acquisition system. This enables the testing and calculation of the squirrel cage's dynamic stiffness, creating a novel test bench for squirrel cage dynamic stiffness. This bench offers advantages such as simple structure, high safety, fast response, wide applicability, and strong operability. Attached Figure Description

[0015] Figure 1 This is a front view of a dynamic stiffness measuring device for an elastic support of a squirrel cage according to the present invention.

[0016] Figure 2 This is a left view of a dynamic stiffness measuring device for an elastic support of a squirrel cage according to the present invention.

[0017] Figure 3 This is a schematic diagram of the support for the measuring device of the present invention;

[0018] Figure 4 This is a schematic diagram of the bracket of the measuring device of the present invention;

[0019] Figure 5 This is a schematic diagram of the fixing ring of the measuring device of the present invention;

[0020] In the diagram: 1. Bracket, 2. Bracket, 3. Fixing ring, 4. Socket head cap screw, 5. Socket head cap screw, 6. Spring washer, 7. Rotary vibrator, 8. Eddy current displacement sensor, 9. Squirrel cage, 10. Reinforcing plate I, 11. Base plate, 12. Vertical plate I, 13. Reinforcing plate II, 14. Reinforcing plate III, 15. Vertical plate II, 16. Base plate, 17. Support plate, 18. Connecting plate. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments.

[0022] like Figure 1 and Figure 2 As shown, a test bench for testing the dynamic stiffness of a squirrel cage elastic support is provided. The test bench mainly consists of 12 components, including a bracket 1, a support frame 2, a fixing ring 3, a hexagonal tapered set screw 4, a hexagonal screw 5, a spring washer 6, a rotary vibrator 7, an eddy current displacement sensor 8, and a squirrel cage 9.

[0023] like Figure 3 As shown, the support frame of the test bench is an assembly, consisting of seven parts: base plate 16, reinforcing plate I 10, base plate 11, upright plate I 12, reinforcing plate II 13, reinforcing plate III 14, and upright plate II 15.

[0024] The base plate has four symmetrically arranged U-shaped holes, which can be used to fix it to the test platform with anchor bolts, thus ensuring the stability of the entire cage stiffness test bench. The reinforcing plate I has a welding bevel; its bottom surface contacts the base plate, and its side surface contacts the vertical plate II. The base plate, vertical plate II, and two symmetrically arranged reinforcing plates I are combined by welding. The lower surface of the seat plate is fillet welded to vertical plate II and reinforcing plate III; the upper surface of the seat plate is fillet welded to vertical plate I and reinforcing plate II. Vertical plate I is a rectangular plate with a circular hole of a certain diameter in the center. Around the circular hole are 12 threaded holes arranged in a circular array for easy assembly and connection with the cage flange. Simultaneously, two threaded holes are symmetrically arranged on the wall of the vertical plate for subsequent connection with the bracket.

[0025] like Figure 4 As shown, bracket 2 is an assembly formed by welding bracket 17 and connecting plate 18. Connecting plate 18 has two threaded holes symmetrically arranged. Bracket 2 is connected to upright plate I12 in bracket 1 by using hex socket screws 5.

[0026] The eddy current displacement sensor is mounted on the outside of the rat cage via a bracket, and multiple sensors can be arranged in different positions as needed. The center line of each sensor passes exactly through the center of the rat cage to detect the displacement signal of the rat cage, and is subsequently connected to a data acquisition system for vibration signal acquisition and analysis.

[0027] The rat cage is assembled and connected to the upright plate I using hexagonal screws and spring washers. This fixes the rat cage on the support of the test bench, laying the groundwork for subsequent dynamic stiffness tests of the rat cage.

[0028] The rotary exciter is an attachment to the squirrel cage to generate excitation force for dynamic stiffness testing. Using a rotary exciter replaces the rotor, resulting in a simpler, more controllable, and safer test structure. The rotary exciter allows for force control by increasing the imbalance, and a force sensor within the exciter collects the force signal. The stiffness of the squirrel cage can be determined by the magnitude of the force from the rotary exciter and the displacement amplitude signal obtained from the eddy current displacement sensor, and the stiffness of the squirrel cage was tested.

[0029] The fixing ring has multiple through threaded holes symmetrically arranged radially and multiple threaded holes of a certain depth symmetrically arranged axially. The fixing ring is placed on the inner wall of the squirrel cage, with a clearance fit between the outer surface of the fixing ring and the inner surface of the squirrel cage. The fixing ring and the squirrel cage are fixedly assembled by using a hexagonal socket head cap screw passing through the radial threaded holes of the fixing ring. The rotary vibrator is assembled with the fixing ring by using a hexagonal socket head cap screw and a spring washer, in conjunction with the axially arranged threaded holes of a certain depth on the fixing ring. In summary, the fixing ring serves to connect and fix the rotary vibrator and the squirrel cage. Figure 5As shown, the retaining ring 3 has six through threaded holes symmetrically arranged in the radial direction and six threaded holes of a certain depth symmetrically arranged in the axial direction. The retaining ring 3 serves to connect the squirrel cage 9 and the rotary vibrator 7.

[0030] The design concept of this invention is as follows: A support structure for supporting components such as the squirrel cage, rotary vibrator, and sensors is constructed by welding seven components: a base plate, reinforcing plate I, a seat plate, upright plate I, reinforcing plate II, reinforcing plate III, and upright plate II. The base plate features U-shaped holes for anchor bolts to secure the support to the test platform. An upright plate with a hollow center and a series of threaded holes facilitates connection to the squirrel cage's flange, thus fixing the squirrel cage to the support. A retaining ring with a series of threaded holes in both the axial and radial directions is designed. The outer surface of the retaining ring has a clearance fit with the inner surface of the squirrel cage, and a hexagonal headstock set screw passes through the radial threaded hole of the retaining ring to assemble the retaining ring and the squirrel cage. A hexagonal headstock screw and a spring washer pass through the axial threaded hole of the retaining ring to assemble the rotary vibrator and the retaining ring. Experiments are conducted using a rotary vibrator instead of a rotor in accordance with actual conditions. The bracket is designed with its side surface bolted to the support. An eddy current displacement sensor passes through the upper surface of the bracket and is placed at the center of the outer surface of the cage. The sensor is used to detect the displacement signal of the cage under the action of the rotary exciter and output the signal to the signal acquisition system to realize subsequent data acquisition and analysis.

[0031] This invention provides a test bench for testing the dynamic stiffness of a squirrel cage elastic support based on a rotary exciter. The main components, including a bracket and fixing rings, connect and fix the squirrel cage, rotary exciter, and eddy current displacement sensor. An adjustable imbalance is added inside the rotary exciter, and the magnitude of the imbalance force applied to the squirrel cage is obtained through a force sensor inside the exciter. The displacement signal of the squirrel cage is monitored, acquired, and analyzed using the eddy current displacement sensor and a data acquisition system. This allows for the experimental and calculation of the dynamic stiffness of the squirrel cage. The test bench, following the steps outlined below, completes the squirrel cage test and offers advantages such as simple structure, high safety, fast response, wide applicability, and strong operability.

[0032] 1. Fix the base plate 16 to the test platform using anchor bolts, thereby fixing the entire squirrel cage stiffness test platform.

[0033] 2. The bottom surface of reinforcing plate I10 is in contact with the upper surface of base plate 16, and the side surface of reinforcing plate I10 is in contact with vertical plate II15. The base plate 16, vertical plate II15 and two symmetrically arranged reinforcing plates I10 are combined by welding.

[0034] 3. Weld the lower surface of the base plate 11 to the vertical plate II 15 and the reinforcing plate III 14 with fillet welds; weld the upper surface of the base plate 11 to the vertical plate I 12 and the reinforcing plate II 13 with fillet welds.

[0035] 4. Assemble and connect the upright plate I12 and the mouse cage 9 using hex socket screws 5 and spring washers 6.

[0036] 5. Connect bracket 2 to the upright plate I12 in bracket 1 using hex socket screws 5.

[0037] 6. Install the eddy current displacement sensor 8 on the outside of the squirrel cage 9. Multiple eddy current displacement sensors 8 can be arranged in different positions as needed. The center line of each eddy current displacement sensor 8 passes exactly through the center of the squirrel cage 9 and is used to detect the displacement signal of the squirrel cage 9.

[0038] 7. The rat cage 9 and the upright plate I 12 are assembled and connected by using hex socket screws 5 and spring washers 6.

[0039] 8. Place the fixing ring 3 on the inner wall of the cage 9, with the outer surface of the fixing ring 3 in contact with the inner surface of the cage 9. The fixing ring 3 and the cage 9 are fixedly assembled by passing the internal hexagonal tapered set screw 5 through the radial threaded hole of the fixing ring.

[0040] 9. Assemble the rotary vibrator 7 with the retaining ring 3. This is done by using an internal hex screw 5 and a spring washer 6, passing through the axial threaded hole of the retaining ring 3.

[0041] 10. The rotary vibrator 7 replaces the rotor in the stiffness test. By adjusting the position of the pre-reserved assembly imbalance within the rotary vibrator 7, the magnitude of the assembly imbalance can be changed, thereby achieving adjustable excitation force acting on the squirrel cage 9. The magnitude of the imbalance can be arbitrarily set, as long as it does not exceed the measurement range of the force sensor and the generated excitation force will not damage the squirrel cage. The magnitude of the excitation force is obtained through the force sensor inside the rotary vibrator 7. The structure is simple and highly controllable.

[0042] The aforementioned imbalance is the product of the mass of the screw at the pre-reserved position inside the rotary vibrator 7 and its radius. Different screw masses generate different magnitudes of excitation force, which then acts on the squirrel cage. The magnitude of the excitation force is obtained through a force sensor inside the rotary vibrator 7. The structure is simple and highly controllable.

[0043] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A test bench for testing the dynamic stiffness of a squirrel cage elastic support based on a rotary exciter, characterized in that... include: Bracket, support, retaining ring, eddy current displacement sensor; The bracket supports the squirrel cage, rotary vibrator, and eddy current displacement sensor. The fixing ring has threaded holes in both the axial and radial directions. The outer surface of the fixing ring is clearance-fitted to the inner surface of the squirrel cage, and a hexagonal set screw passes through the radial threaded hole of the fixing ring to assemble the fixing ring and the squirrel cage. A hexagonal screw and a spring washer pass through the axial threaded hole of the fixing ring to assemble the rotary vibrator and the fixing ring. A bracket is mounted on the bracket, and the eddy current displacement sensor passes through the bracket and is placed at the center of the outer surface of the squirrel cage. It is used to detect the displacement signal of the squirrel cage under the action of the rotary vibrator and output the signal to an external signal acquisition system for subsequent data acquisition and analysis. The number of eddy current displacement sensors is two. When it is necessary to determine the influence of the anisotropy of the squirrel cage on the dynamic stiffness, the two sensors are set at 90 degrees to each other and measure the displacement in two directions respectively, so as to realize the simultaneous measurement of the dynamic stiffness of the squirrel cage in two directions. The eddy current displacement sensors are connected to the bracket by threads and fixed with nuts. During the welding process, the center line of the bracket is ensured to pass through the center of the squirrel cage. The rotary exciter is used to generate excitation force to replace the rotor for testing. The force signal is collected by a force sensor inside the rotary exciter. The dynamic stiffness of the squirrel cage is obtained by the magnitude of the force of the rotary exciter and the displacement amplitude signal obtained by the eddy current displacement sensor.

2. The test bench according to claim 1, characterized in that: The bracket consists of a base plate, reinforcing plate I, a seat plate, upright plate I, reinforcing plate II, reinforcing plate III, and upright plate II. The base plate is symmetrically provided with multiple U-shaped holes, which are fixed to the test platform by anchor bolts, thereby ensuring the fixation of the entire rat cage dynamic stiffness test bench; the reinforcing plate I is provided with a welding bevel, its bottom surface contacts the base plate, and its side surface contacts the vertical plate II, and the base plate, vertical plate II and two symmetrically arranged reinforcing plates I are combined by welding; the lower surface of the seat plate is corner welded to the vertical plate II and the reinforcing plate III; the upper surface of the seat plate is corner welded to the vertical plate I and the reinforcing plate II; the base plate and the seat plate are installed on opposite sides of the vertical plate II.

3. The test bench according to claim 2, characterized in that: The upright plate I is a rectangular plate with a circular hole of a certain diameter in the center. The size of the circular hole is matched with the clearance of the rat cage so that the rat cage can pass through the upright plate I. The circular array of threaded holes around the circular hole is used for assembly and connection with the rat cage flange. At the same time, threaded holes are symmetrically provided on the wall of the upright plate for connection with the bracket.

4. The test bench according to claim 2, characterized in that: The bracket is an assembly formed by welding a support plate and a connecting plate; the connecting plate has two threaded holes symmetrically arranged, and the bracket is connected to the upright plate I in the bracket by using hexagonal screws.

Images