Non-circular fixed-width curve floating ring oil film damper

Abstract

The invention relates to a non-circular fixed-width curve floating ring oil film damper which comprises a damper shaft neck, a damper outer ring and a floating ring located between the damper shaft neck and the damper outer ring, and the outer ring of the section of the floating ring is a floating ring outer ring fixed-width curve. The inner ring of the section of the damper outer ring is provided with a damper outer ring fixed-width curve matched with the floating ring outer ring fixed-width curve, and an evenly-distributed outer layer oil film is formed between the floating ring and the damper outer ring. A plurality of wedge-shaped gaps which are connected end to end are formed between the floating ring outer ring fixed-width curve and the damper outer ring fixed-width curve, the oil film pressure at the thin positions of the gaps is larger, and return torque is dynamically generated on the floating ring by changes generated by oil film pressure distribution. The defects of the floating ring squeeze film damper in the application of aero-engines are overcome, and the floating ring squeeze film damper is particularly important for improving the technical maturity and application and popularization of FSFDs.

Description

Technical Field

[0001] The invention relates to the technical field of oil film dampers, in particular to a non-circular fixed-width curve floating ring oil film damper. Background Art

[0002] Squeeze Film Dampers (SFDs) are a type of support damping structure device commonly used in aircraft engines. They improve the dynamic characteristics of the rotor system through the fluid dynamic pressure effect generated by the precession of the damper journal, thereby improving the rotor system's ability to pass critical speeds, reducing vibration, and reducing support force transmission.

[0003] When the system parameters are not designed properly, the rotor system may produce bistable vibration, amplitude jump behavior and uncoordinated precession response due to the action of the squeeze film damper, which will endanger the operation safety of the aircraft engine. Floating ring squeeze film dampers have been proven to effectively overcome the shortcomings of squeeze film dampers. Floating ring squeeze film dampers (FSFDs) can overcome the bistable response and uncoordinated precession of the rotor system caused by the highly nonlinear oil film reaction force of traditional squeeze film dampers, inhibit the generation of cavitation, and improve the nonlinearity of the oil film. However, compared with ordinary dampers, floating ring squeeze film dampers have an additional moving part, which increases the complexity of the system and also leads to some potential problems, such as solid contact and friction caused by the positioning pins or bosses used to limit the self-rotation of the floating ring (to prevent the damper from failing).

[0004] The damper journal of the squeeze film damper deviates from the geometric center and precesses without self-rotation during operation. The relative motion between it and the outer ring wall of the damper is translational, and relative rotation or sliding cannot occur. Otherwise, the squeeze film cannot play a vibration reduction role, but will increase the amplitude of the engine rotor (damper failure). Therefore, the concentric squeeze film damper ensures that the damper journal and the damper outer ring do not rotate relative to each other by installing squirrel cage elastic support, and the non-concentric squeeze film damper ensures that the damper journal and the damper outer ring do not rotate relative to each other by installing anti-rotation pins.

[0005] In order to prevent the floating ring from rotating and causing the damper to fail, for the floating ring squeeze film damper, it is necessary to ensure that the floating ring has no relative rotation or sliding relative to the damper shaft neck. Therefore, in actual applications, certain structural improvements are often made to limit the rotation. Common methods to limit the floating ring include installing locating pins and adding bosses to the floating ring. Installing a locating pin means opening a hole slightly larger than the cross-section of the locating pin on the floating ring, and passing the locating pin through the hole (clearance fit) during installation, while the locating pin is fixed to the outer ring of the damper. The floating ring boss is two protrusions machined on the arc surface of the floating ring, distributed at 180° on the diameter line close to one end face of the floating ring. When installing, the floating ring needs to be placed with the boss into the corresponding notch of other components of the damper.

[0006] According to the geometric conditions for the hydrodynamic effect, the liquid needs to flow through the wedge-shaped gap, and there must be relative motion between the walls on both sides of the gap. The ring can only form two wedge-shaped gaps at most during the floating process.

[0007] The floating ring of the partial floating ring squeeze film damper has elastic support, a very small floating range, and no self-rotation, but its damping effect is not as good as that of the full floating ring without elastic support.

[0008] The floating ring is positioned by a positioning pin or a boss is added on the surface to limit the self-rotation, which reduces the effective extrusion area of ​​the floating ring arc surface and destroys the integrity of the oil film. The boss will affect the center of gravity of the floating ring and the movement state of the floating ring. The positioning pin will affect the circulation of the outer layer of the floating ring oil film.

[0009] The two methods of limiting the self-rotation of the floating ring, the locating pin and the boss, basically hinder the self-rotation of the floating ring by the reaction force (torque on the floating ring) generated by the small area of ​​solid contact. Since the solid contact area is very small (point contact or line contact), a large stress concentration will be formed at the contact position. Continuous solid contact will greatly increase the possibility of the floating ring generating low-frequency modes, and at the same time have a negative impact on the service life and reliability of the floating ring.

[0010] Regardless of whether the positioning pin or the boss is used, the changes in the structure of the floating ring itself and the changes in other components of the damper will reduce the reliability of the system. Summary of the invention

[0011] The invention aims at the deficiencies of the prior art and provides a non-circular constant-width curve floating ring oil film damper.

[0012] The present invention is achieved through the following technical scheme, which provides a non-circular fixed-width curve floating ring oil film damper, including a damper shaft neck, a damper outer ring and a floating ring located between the damper shaft neck and the damper outer ring, an outer oil film is formed between the floating ring and the damper outer ring, the damper outer ring is provided with an oil supply hole connected to the outer oil film, the outer ring of the floating ring cross section is a floating ring outer ring fixed-width curve, and the inner ring of the damper outer ring cross section is provided with a damper outer ring fixed-width curve adapted to the floating ring outer ring fixed-width curve.

[0013] As an optimization, the outer ring of the damper journal is provided with an annular groove, and the floating ring is arranged in the annular groove.

[0014] As an optimization, the floating ring outer ring width-fixing curve includes an odd number of arcs, and the number of arcs is greater than or equal to 3.

[0015] As an optimization, the circumscribed circle of the floating ring outer ring constant width curve and the damper outer ring constant width curve have an intersection.

[0016] As an optimization, the inner circle of the floating ring cross section is a circle or a fixed width curve of the inner circle of the floating ring.

[0017] As an optimization, the oil supply hole is connected to the middle position in the length direction of the floating ring.

[0018] As an optimization, the number of the oil supply holes is equal to the number of arcs of the fixed width curve of the outer ring of the floating ring, and the oil supply holes are connected to the middle position of the arc.

[0019] The beneficial effects of the present invention are: (1) The present invention fully retains the advantages of the fully floating floating ring squeeze film damper while improving its application maturity and practicality.

[0020] (2) The geometric center of the circumscribed circle of the constant width curve (i.e., the center of the circle) is not concentric with the center of gravity of the floating ring. Under reasonable design, the floating stability of the floating ring can be improved.

[0021] (3) The present invention avoids the solid contact low-frequency mode that may be generated by the traditional method of limiting the rotation of the floating ring, as well as the damage to the integrity of the oil film.

[0022] (4) The present invention can form a plurality of wedge-shaped oil film gaps, which can adaptively limit the self-rotation of the floating ring and make the force on the floating ring more uniform and more reliable.

[0023] (5) The curvature of a non-circular constant-width curve is lower than that of a circular one, and the oil film extrusion effect produced is better.

[0024] (6) The oil film is squeezed to produce a damping effect, which makes the floating ring float and also limits the rotation of the floating ring. The lubricating oil space utilization rate is high and the damper is highly maintainable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention; Figure 2 For the present invention Figure 1 Enlarged view of part A in the middle; Figure 3 is a schematic cross-sectional view of the outer oil film of the present invention; Figure 4 For the present invention Figure 3 Enlarged view of middle part B; Figure 5 It is a cross-sectional schematic diagram of the outer oil film when the floating ring of the present invention rotates relatively; Figure 6 It is a structural schematic diagram of the floating ring of the present invention; Figure 7 Design curve for the number of sides of fixed width curve and the outer oil film gap of anti-rotation floating ring damper; As shown in the figure: 1. Damper journal, 2. Damper outer ring, 3. Floating ring, 4. Oil supply hole, 5. Bearing, 6. Rotor, 7. Outer oil film, 8. Circumscribed circle of floating ring outer ring fixed width curve, 9. Inscribed regular polygon of floating ring outer ring fixed width curve, 10. Damper outer ring fixed width curve, 11. Floating ring outer ring fixed width curve. DETAILED DESCRIPTION

[0026] In order to clearly illustrate the technical features of this solution, this solution is described below through a specific implementation method.

[0027] like Figures 1 to 7 As shown, the non-circular constant width curve floating ring oil film damper of the present invention comprises a damper journal 1 and a damper outer ring 2 , and the inner ring of the damper journal 1 is connected to the rotor 6 through a bearing 5 .

[0028] It also includes a floating ring 3 located between the damper journal 1 and the damper outer ring 2, wherein the outer ring of the damper journal 1 is provided with an annular groove, and the floating ring 3 is arranged in the annular groove. The two ends of the floating ring 3 are planes, and there are oil films at both ends, the inner ring and the outer ring of the floating ring 3, wherein an outer oil film 7 is formed between the floating ring 3 and the damper outer ring 2, and the damper outer ring 2 is provided with an oil supply hole 4 connected to the outer oil film 7. The oil supply hole 4 extends radially along the damper outer ring 2, and the oil supply hole 4 is connected to the middle position in the length direction of the floating ring 3, so that the oil evenly enters the outer oil film 7.

[0029] A convex closed curve on a plane, whose width in any direction never changes no matter how it is rotated, is called a constant width curve or a constant width curve. Every regular polygon with an odd number of sides can generate a constant width curve by drawing circular arcs. Such constant width curves are called Reuleaux polygons. Constant width curves are composed of an odd number of identical circular arcs. For example, a Reuleaux triangle (three-sided constant width curve) is a common constant width curve.

[0030] The inner circle of the cross section of the floating ring 3 is a circle or a constant-width curve of the inner circle of the floating ring, and the bottom of the corresponding annular groove is also a circle or a constant-width curve.

[0031] The outer ring of the cross section of the floating ring 3 is a floating ring outer ring width-fixing curve 11, which is a Reuleaux polygon. The floating ring outer ring width-fixing curve 11 includes an odd number of arcs, and the number of arcs is greater than or equal to 3. The inner ring of the cross section of the damper outer ring 2 is provided with a damper outer ring width-fixing curve 10 adapted to the floating ring outer ring width-fixing curve 11.

[0032] The number of the oil supply holes 4 is equal to the number of arcs of the floating ring outer ring fixed width curve 11, and the oil supply holes 4 are connected to the middle position of the arc.

[0033] When the inner ring of the floating ring 3 is concentric with the damper journal 1, the gap of the outer oil film 7 is evenly distributed. Figure 3 As shown (taking a heptagon as an example), the dotted line of the regular heptagon is a regular polygon 9 inscribed in the fixed width curve of the outer ring of the floating ring, and the dotted line of the circle is a circumscribed circle 8 of the fixed width curve of the outer ring of the floating ring. It is known that for all non-circular fixed width curves, the circumscribed circle of the inscribed regular polygon is the circumscribed circle of the fixed width curve. In this embodiment, the circumscribed circle of the regular polygon 9 inscribed in the fixed width curve of the outer ring of the floating ring is the circumscribed circle 8 of the fixed width curve of the outer ring of the floating ring.

[0034] The two solid lines are both seven-sided constant-width curves, of which the one with a smaller enclosed area is the floating ring outer ring constant-width curve 11, and the one with a larger enclosed area is the damper outer ring constant-width curve 10. Figure 4 As shown, without using positioning pins or bosses, the floating ring 3 is immersed in oil as a whole, and the gap thickness of the outer oil film 7 between the damper outer ring 2 and the floating ring 3 is uniform. When the damper journal 1 drives the floating ring 3 to move, the outer ring wall of the floating ring 3 squeezes the outer oil film 7, and the torque generated by the outer oil film 7 adaptively limits the rotation of the floating ring 3.

[0035] The specific anti-rotation mechanism is: once the floating ring 3 has a tendency to rotate relative to the damper outer ring 2 during the floating process, multiple wedge-shaped gaps connected end to end will be formed between the floating ring outer ring fixed width curve 11 and the damper outer ring fixed width curve 10. The oil film pressure is greater where the gap is thinner, and the change caused by the oil film pressure distribution dynamically generates a return torque on the floating ring. Figure 5 As shown, the floating ring outer ring constant width curve 11 tends to rotate clockwise relative to the damper outer ring constant width curve 10, and a larger oil film force is generated at the smaller oil film gap (arrow position), and the oil film force generates a counterclockwise restoring torque on the floating ring.

[0036] If the rotor support system of the aircraft engine performs maneuvering flight with the aircraft, especially when the aircraft performs rolling maneuvers around the longitudinal axis of the fuselage, the damper outer ring fixed width curve 10 will be twisted first relative to the floating ring, and multiple wedge-shaped gaps will also be formed between the floating ring outer ring fixed width curve 11 and the damper outer ring fixed width curve 10. The torque generated by the rolling maneuvering flight is transmitted to the outer surface of the floating ring 3 through the pressure of the outer oil film 7, so that the floating ring 3 hardly rotates relative to the damper outer ring 2, but floats within a small range.

[0037] The geometric condition for the floating ring oil film damper with non-circular constant width curve to limit the self-rotation of the floating ring is: the distance from a certain part of the damper outer ring constant width curve 10 to the center of the circumscribed circle 8 of the floating ring outer ring constant width curve is less than the radius of the circumscribed circle 8 of the floating ring outer ring constant width curve. That is, the circumscribed circle of the floating ring outer ring constant width curve 11 and the damper outer ring constant width curve 10 have an intersection.

[0038] In order to meet the geometric conditions of the non-circular fixed width curve damper to limit the rotation of the floating ring, the design criteria of the fixed width curve floating ring damper can be derived. Assuming that the number of edges of the fixed width curve of the outer ring of the floating ring is n (n=3,5,7,11…), the radius of the circumscribed circle of the fixed width curve of the outer ring of the floating ring is The overall geometric parameters of the floating ring damper are dimensionless, and the radius of the circumscribed circle of the fixed-width curve of the outer ring of the floating ring is converted to unit 1. The dimensionless width of the fixed-width curve is: According to the geometric conditions of the non-circular fixed-width curve damper to limit the self-rotation of the floating ring, the corresponding fixed-width curve floating ring damper anti-rotation design criteria are deduced as follows: Where C is the outer oil film gap.

[0039] According to the above design criteria, by substituting the number of edges of different fixed-width curves into formula (2), a design curve of the number of edges of a fixed-width curve and the outer oil film gap of the anti-rotation floating ring damper can be obtained. The value of must be below the design curve to ensure that the floating ring is limited in rotation. Figure 7 When the outer oil film gap C of the floating ring squeeze film damper is relatively fixed, the number of edges n of the fixed-width curve between the floating ring and the outer ring of the damper should be adjusted to meet the design criteria for limiting the self-rotation of the floating ring.

[0040] Of course, the above description is not limited to the above examples. Technical features not described in the present invention can be achieved by or by using existing technologies, which will not be described here. The above embodiments and drawings are only used to illustrate the technical scheme of the present invention and are not limitations of the present invention. The present invention is described in detail with reference to the preferred implementation methods. Ordinary technicians in this field should understand that changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention do not depart from the purpose of the present invention, and should also fall within the scope of protection of the claims of the present invention.

Claims

1. A non-circular fixed width curved floating ring oil film damper, comprising a damper journal (1), a damper outer ring (2), and a floating ring (3) located between the damper journal (1) and the damper outer ring (2), an outer oil film (7) being formed between the floating ring (3) and the damper outer ring (2), the damper outer ring (2) being provided with an oil supply hole (4) connected to the outer oil film (7), characterized in that: The outer ring of the floating ring (3) cross section is a floating ring outer ring fixed width curve (11), and the inner ring of the damper outer ring (2) cross section is provided with a damper outer ring fixed width curve (10) adapted to the floating ring outer ring fixed width curve (11).

2. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The outer ring of the damper shaft journal (1) is provided with an annular groove, and the floating ring (3) is arranged in the annular groove.

3. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The floating ring outer ring width-fixing curve (11) includes an odd number of arcs, and the number of arcs is greater than or equal to 3.

4. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The circumscribed circle of the floating ring outer ring constant width curve (11) and the damper outer ring constant width curve (10) have an intersection point.

5. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The inner circle of the cross section of the floating ring (3) is a circle or a fixed width curve of the inner circle of the floating ring.

6. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The oil supply hole (4) is connected to the middle position of the floating ring (3) in the length direction.

7. The non-circular constant width curve floating ring oil film damper according to claim 1, characterized in that: The number of the oil supply holes (4) is equal to the number of arcs of the floating ring outer ring fixed width curve (11), and the oil supply holes (4) are connected to the middle position of the arc.

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