CN113027548A - Elastic buffer casing and rigidity coefficient design method thereof - Google Patents
Elastic buffer casing and rigidity coefficient design method thereof Download PDFInfo
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- CN113027548A CN113027548A CN202110446442.9A CN202110446442A CN113027548A CN 113027548 A CN113027548 A CN 113027548A CN 202110446442 A CN202110446442 A CN 202110446442A CN 113027548 A CN113027548 A CN 113027548A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/24—Casings; Casing parts, e.g. diaphragms, casing fastenings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/04—Antivibration arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/16—Arrangement of bearings; Supporting or mounting bearings in casings
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/24—Casings; Casing parts, e.g. diaphragms, casing fastenings
- F01D25/243—Flange connections; Bolting arrangements
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/17—Mechanical parametric or variational design
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- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
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Abstract
The elastic buffer casing sequentially comprises a flange part section, a first bearing seat section, a transition section and a second bearing seat section along the axial direction, wherein the flange part section is provided with a flange edge, and the flange edge is fixedly connected with an outer casing through a bolt, so that one end of the elastic buffer casing is fixed on the outer casing; the inner hole of the first bearing seat section is matched with the excircle of a first bearing arranged on the power output shaft assembly; the inner hole of the second bearing seat section is matched with the outer circle of a second bearing arranged on the power output shaft assembly; the diameter of the transition section gradually changes from the diameter of the first bearing seat section to the diameter of the second bearing seat section along the axial direction. The rigidity coefficient of elastic buffer machine casket is reduced, the action time of impact force is prolonged, so that the action that the power turbine rotor system and the machine casket are prevented from being damaged by vibration impact is achieved, and the complete machine of the aero-engine is ensured to work safely and stably.
Description
Technical Field
The application relates to the field of aviation turboshaft engines, in particular to an elastic buffer casing and a rigidity coefficient design method thereof.
Background
At present, the power of a front output type turboshaft engine is transmitted to an output shaft through a power turbine shaft by a power turbine, so that the power turbine shaft is slender, the length-diameter ratio is large and flexible, elastic supports are arranged at two ends of the power turbine shaft, an extruded oil film is generally required to be designed for vibration reduction of the elastic supports, when an engine rotor system impacts or vibrates greatly, an oil film gap disappears, rigid collision between the rotor system and a casing is caused, and if protection is not performed, damage is caused to the rotor system and each bearing casing. Therefore, there is a need for an elastic buffer casing which can play a role of flexible protection to avoid or reduce the vibration impact damage of the rotor system and the rigid casing.
Disclosure of Invention
The application provides an elastic buffer casing on the one hand to solve the technical problem that impact damage is finally caused to a rotor system and each bearing casing due to rigid collision of the rotor system and the casing caused by disappearance of oil film gaps of an elastic support when an existing engine rotor system is impacted or vibrates greatly instantly.
The technical scheme adopted by the application is as follows:
an elastic buffer casing comprises a flange part section, a first bearing seat section, a transition section and a second bearing seat section in sequence along the axial direction,
the flange part section is provided with a flange edge, and the flange edge is fixedly connected with the outer casing through a bolt, so that one end of the elastic buffering casing is fixed on the outer casing;
the inner hole of the first bearing seat section is matched with the excircle of a first bearing arranged on the power output shaft assembly;
the inner hole of the second bearing seat section is matched with the outer circle of a second bearing arranged on the power output shaft assembly;
the diameter of the transition section is gradually transited from the diameter of the first bearing seat section to the diameter of the second bearing seat section along the axial direction, and the transition section is used for reducing the rigidity coefficient K of the elastic buffering casing, so that the action time of impact force is prolonged, and the purpose of reducing the impact force is achieved.
Further, the span M between the central cross section of the first bearing and the mounting edge of the outer casing has a value range of: 10 mm-100 mm;
the value range of the span N between the central cross section of the second bearing and the mounting edge of the outer casing is as follows: m + (20 mm-100 mm).
Furthermore, the transition section comprises a thickening conical section and an equal-thickness conical section which are sequentially arranged along the axial direction, and the joint of the thickening conical section and the first bearing seat section, the joint of the thickening conical section and the equal-thickness conical section and the joint of the equal-thickness conical section and the second bearing seat section are all in smooth transition through circular arcs.
Further, the longitudinal section profile of the transition section is a circular arc line with a radius of R.
Furthermore, the longitudinal section profile of the transition section is an arc line which is concave inwards towards the central axis direction of the elastic buffer casing.
Furthermore, the longitudinal section profile of the transition section is in a circular arc shape protruding outwards in the direction far away from the central axis of the elastic buffer casing.
Furthermore, the transition section is an equal wall thickness transition section or a variable wall thickness transition section, and the thickness of the variable wall thickness transition section is gradually reduced from the first bearing seat section to the second bearing seat section.
The application also provides a rigidity coefficient design method of the elastic buffer casing, which comprises the following steps:
1) determining the total length L of a casing, the inner diameter R1 of a first bearing seat section and the thickness ratio s of h1/h2 (R1-R1)/(R2-R2) according to the size of a bearing and a rotating shaft and the rotor dynamic requirement, wherein the outer diameter of the first bearing seat section is R1, the thickness of h1 is R1-R1, the outer diameter of the second bearing seat section is R2, the inner diameter of the second bearing seat section is R2, and the thickness of h2 is R2-R2;
2) determining a division parameter t, and setting a calculation precision e0, wherein when a golden division method is adopted, the division parameter t is 0.618, when a bisection method is adopted, the division parameter t is 0.5, and the calculation precision e0 is 0.001-0.0001;
3) setting the upper limit value Hh of h1 to 10mm and the lower limit value Hg to 0.1 mm;
4) setting a current thickness h1 ═ Hg + t × (Hh-Hg) of the first bearing seat section of the elastomeric snubber case;
5) obtaining a complete geometric model of the support structure from the current thickness h1 of the first bearing block section and the relevant structural dimensions given in step 1);
6) calculating the rigidity coefficient K of the first bearing seat section by adopting a finite element method or a beam theory formula;
7) if | K-K0|/K0E0 is less than or equal to e, then the step 9) is carried out, otherwise, the step 8) is carried out, K is carried out0Presetting a rigidity coefficient according with requirements;
8) if K-K0≦ 0? If Hg is set to h1, go to step 4), otherwise, if Hh is set to h1, go to step 4);
9) outputting a calculation result to obtain the thickness h1 and the rigidity coefficient K of the first bearing block section;
10) and (3) keeping the thickness h1 of the obtained first bearing seat section unchanged, replacing h1 with the thickness h2 of the second bearing seat section as a design variable, and repeating the steps 1) to 9) to obtain the thickness h2 and the rigidity coefficient K of the second bearing seat section.
Further, the process of calculating the stiffness coefficient K of the first bearing block section by using the finite element method specifically includes the steps of:
1) dividing a finite element grid into the elastic buffer casing model, and applying boundary conditions, wherein the boundary conditions comprise applying unit load to the first bearing block section, and the unit load vertically points to the central axis direction of the elastic buffer casing model; constraining the axial displacement, the radial displacement and the circumferential displacement of the fixed end of the elastic buffer casing model so as to generate an elastic buffer casing finite element model;
2) running a finite element program, selecting a Fourier ring unit, and inputting the generated elastic buffer casing finite element model;
3) inputting material parameters including the elastic modulus E and Poisson ratio mu of the material;
4) setting the Fourier circumferential wave number to be 1;
5) calculating a Fourier ring unit stiffness matrix [ K ], an assembled system overall stiffness matrix [ K ] and a load vector { F }, calling a linear equation set solving module to solve a system equation, [ K ] { U } - { F }, and obtaining a displacement vector { U };
6) and obtaining the displacement value of each node in the outer ring width range of the first bearing according to the displacement vector { U }, wherein the average value of the obtained displacement values is the flexibility coefficient lambda of the first bearing seat section, and the reciprocal of the flexibility coefficient lambda is the rigidity coefficient K of the first bearing seat section.
Further, the process of calculating the stiffness coefficient K of the first bearing seat section by using the beam theory formula specifically includes the steps of:
selecting a single-section cylindrical beam, two sections of cylindrical beams or three sections of cylindrical beams to perform approximate calculation according to the specific shape of the elastic buffer casing structure and the precision requirement of rigidity calculation;
for the simulation of the elastic buffer casing which is close to a cylinder shape and adopts a single-section cylindrical beam, the calculation formula of the rigidity coefficient K is as follows:
wherein: r1Is the outer diameter r of a single-section cylindrical beam1The inner diameter of the single-section cylindrical beam is shown, E is the elastic modulus, pi is 3.14159 is the circumference ratio, and L is the length of the single-section cylindrical beam;
the calculation formula of the rigidity coefficient K of the two sections of cylindrical beams is as follows:
wherein: λ is the compliance coefficient, L1Is the length, L, of the first section of the two sections of cylindrical beams2Is the length, R, of the second section of the two sections of cylindrical beams1Is the outer diameter r of the first section of the two sections of cylindrical beams1Is the inner diameter, R, of the first section of the two sections of cylindrical beams2Is the outer diameter r of the second section of the two sections of cylindrical beams2The inner diameter of the second section of cylindrical beam in the two sections of cylindrical beams meets the following requirements: l is1>L2，r1>r2；
The calculation formula of the rigidity coefficient K of the three-section cylindrical beam is as follows:
wherein; l is1Is the length, L, of the first section of the three sections of cylindrical beams2Is the length, L, of the second section of the three sections of cylindrical beams3Is the length, R, of the third section of the three sections of cylindrical beams1Is the outer diameter r of the first section of cylindrical beam in the three sections of cylindrical beams1Is the inner diameter, R, of the first section of the two sections of cylindrical beams2Is the outer diameter r of the second section of the three sections of cylindrical beams2The inner diameter of the second section of the three sections of cylindrical beams; r3Is the outer diameter r of the third section of the three sections of cylindrical beams2The inner diameter of the third section of cylindrical beam in the three sections of cylindrical beams meets the following requirements: l is1>L2>L3，r1>r2>r3；
And when the elastic buffer casing structure comprises a non-cylindrical beam, adopting three sections of cylindrical beams to perform approximate simulation and calculating the rigidity coefficient K of the elastic buffer casing structure.
Compared with the prior art, the method has the following beneficial effects:
the elastic buffer casing sequentially comprises a flange subsection, a first bearing seat section, a transition section and a second bearing seat section along the axial direction, wherein the flange subsection is provided with a flange edge, and the flange edge is fixedly connected with an outer casing through a bolt, so that one end of the elastic buffer casing is fixed on the outer casing; the inner hole of the first bearing seat section is matched with the excircle of a first bearing arranged on the power output shaft assembly; the inner hole of the second bearing seat section is matched with the outer circle of a second bearing arranged on the power output shaft assembly; the diameter of the transition section gradually changes from the diameter of the first bearing seat section to the diameter of the second bearing seat section along the axial direction. The utility model provides an elastic buffer machine casket suitably reduces the rigidity coefficient K of elastic buffer machine casket through setting up the changeover portion, the effect time of extension impact force to reach the purpose that reduces the impact force. The stiffness coefficient K of the aero-engine is determined through design steps of gradual iteration, so that the stiffness coefficient K meets the preset stiffness coefficient as much as possible, the elastic buffer casing can be flexibly protected, damage to a power turbine rotor system, the casing and the like caused by vibration impact is reduced or prevented, and the complete aero-engine is ensured to work safely and stably.
In addition to the objects, features and advantages described above, other objects, features and advantages will be apparent from the present application. The present application will now be described in further detail with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. In the drawings:
FIG. 1 is a schematic view of a preferred embodiment of the present application showing a spring-damper casing.
Fig. 2 is a schematic structural view of an elastic buffer casing according to another preferred embodiment of the present application.
FIG. 3 is a schematic view of a spring buffer casing according to another preferred embodiment of the present application.
Fig. 4 is a schematic cross-sectional structure diagram of a single-segment cylindrical beam.
Fig. 5 is a longitudinal sectional (partial) structural view of a single-segment cylindrical beam.
Fig. 6 is a longitudinal sectional (partial) structural view of two-segment cylindrical beams.
Fig. 7 is a longitudinal sectional (partial) structural view of a three-segment cylindrical beam.
FIG. 8 is a schematic view of a casing with a cylindrical beam approximating a non-cylindrical beam.
FIG. 9 is a schematic view of an elastic buffer casing for simulating a non-cylindrical beam by approximation using a multi-segment cylindrical beam.
FIG. 10 is a simplified model of a longitudinal cross-section of a complex cross-sectional shape elastomeric snubber casing.
FIG. 11 is a schematic diagram of a Fourier finite element model of a complex-shaped elastomeric snubber casing.
In the figure:
1. an outer case; 2. a flange edge; 3. a first bearing housing section; 4. a first bearing; 5. a transition section; 6. a vibration damping oil film; 7. a second bearing housing section; 8. a second bearing; 9. a flange segment; 10. a non-cylindrical beam; 11. a cylindrical beam; 12. a first section of cylindrical beam; 13. a second section of cylindrical beam; 14. a third section of cylindrical beam; 15. a fixed end; 16. a first cylindrical section; 17. a circular arc transition section; 18. a second cylindrical section; 19. a first bearing mount; 20. and a second bearing mounting part.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
Referring to fig. 1 and 2, the preferred embodiment of the present application provides an elastomeric snubber casing including, in axial sequence, a flange segment 9, a first bearing block segment 3, a transition segment 5, a second bearing block segment 7,
the flange subsection 9 is provided with a flange edge 2, and the flange edge 2 is fixedly connected with the outer casing 1 through a bolt, so that one end of the elastic buffer casing is fixed on the outer casing 1;
the inner hole of the first bearing seat section 3 is matched with the excircle of a first bearing 4 arranged on a power output shaft assembly;
the inner hole of the second bearing seat section 7 is matched with the outer circle of a second bearing 8 arranged on the power output shaft assembly;
the diameter of the transition section 5 gradually transits from the diameter of the first bearing seat section 3 to the diameter of the second bearing seat section 7 along the axial direction, and the transition section is used for reducing the rigidity coefficient K of the elastic buffer casing, so that the action time of impact force is prolonged, and the purpose of reducing the impact force is achieved.
The embodiment provides an elastic buffer casing, which sequentially comprises a flange part section, a first bearing seat section, a transition section and a second bearing seat section along the axial direction, wherein the flange part section is provided with a flange edge, and the flange edge is fixedly connected with an outer casing through a bolt, so that one end of the elastic buffer casing is fixed on the outer casing; the inner hole of the first bearing seat section is matched with the excircle of a first bearing arranged on the power output shaft assembly; the inner hole of the second bearing seat section is matched with the outer circle of a second bearing arranged on the power output shaft assembly; the diameter of the transition section gradually changes from the diameter of the first bearing seat section to the diameter of the second bearing seat section along the axial direction. The elastic buffering casing of the embodiment properly reduces the rigidity coefficient K of the elastic buffering casing through the arrangement of the transition section, and prolongs the action time of the impact force, so that the purpose of reducing the impact force is achieved, the elastic buffering casing can play a role in flexible protection, the damage to a power turbine rotor system, the casing and the like caused by vibration impact is reduced or prevented, and the complete machine of the aero-engine is ensured to work safely and stably.
Specifically, the span M between the central cross section of the first bearing 4 and the mounting edge of the outer casing 1 has a value range of: 10 mm-100 mm; the value range of the span N between the central cross section of the second bearing 8 and the mounting edge of the outer casing 1 is as follows: m + (20 mm-100 mm).
As shown in fig. 1, in the preferred embodiment of the present invention, the transition section 5 comprises a thickened cone section and an equal-thickness cone section which are sequentially arranged along the axial direction, wherein the included angle between the inner wall of the thickened cone section and the axial line is α, the included angle between the outer wall of the thickened cone section and the axial line is β, and the included angle between the inner wall of the equal-thickness cone section and the axial line is γ. The connecting part of the variable-thickness conical section and the first bearing seat section 3, the connecting part of the variable-thickness conical section and the equal-thickness conical section and the connecting part of the equal-thickness conical section and the second bearing seat section 7 are in smooth transition through circular arcs. The thickened conical section and the equal-thickness conical section which are sequentially arranged can reduce the rigidity coefficient K of the elastic buffer casing, so that the action time of impact force is prolonged, the purpose of reducing the impact force is achieved, the connection part of the thickened conical section and the first bearing seat section 3, the connection part of the thickened conical section and the equal-thickness conical section and the connection part of the equal-thickness conical section and the second bearing seat section 7 can reduce stress concentration through circular arc smooth transition, local fatigue damage caused by stress concentration is prevented from occurring in the deformation process of the elastic buffer casing, and the reliability and the service life of the elastic buffer casing are improved.
In a preferred embodiment of the present invention, a longitudinal cross-sectional profile of the transition section 5 is a circular arc line with a radius R, wherein the transition section 5 is an equal wall thickness transition section or a variable wall thickness transition section, and a thickness of the variable wall thickness transition section gradually decreases from the first bearing seat section 3 to the second bearing seat section 7.
As shown in fig. 2, in a preferred embodiment of the present invention, a longitudinal cross-sectional profile of the transition section 5 is a circular arc line recessed toward a central axis of the elastic buffer casing, the transition section 5 is a transition section with an equal wall thickness or a transition section with a variable wall thickness, and a thickness of the transition section with the variable wall thickness is gradually reduced from the first bearing seat section 3 toward the second bearing seat section 7. In this embodiment, the transition section 5 is an equal wall thickness transition section, and has a simple structure and is convenient to process.
As shown in fig. 3, in a preferred embodiment of the present invention, the longitudinal cross-sectional profile of the transition section 5 is a circular arc shape protruding outward in a direction away from the central axis of the elastic buffer casing, and similarly, the transition section 5 is a transition section with an equal wall thickness or a transition section with a variable wall thickness, and the thickness of the transition section with the variable wall thickness is gradually reduced from the first bearing seat section 3 to the second bearing seat section 7. In this embodiment, the transition section 5 is an equal wall thickness transition section, and has a simple structure and is convenient to process.
The preferred embodiment of the present invention also provides a method for designing the rigidity of a bearing support of an elastic buffer casing, comprising the steps of:
1) determining the total length L of a casing, the inner diameter R1 of the first bearing seat section 3 and the thickness ratio s of h1/h2 (R1-R1)/(R2-R2) according to the size of a bearing and a rotating shaft and the rotor dynamic requirement, wherein the outer diameter of the first bearing seat section 3 is R1, the thickness of h1 is R1-R1, the outer diameter of the second bearing seat section 7 is R2, the inner diameter of the second bearing seat section is R2, and the thickness of h2 is R2-R2;
2) determining a division parameter t, and setting a calculation precision e0, wherein when a golden division method is adopted, the division parameter t is 0.618, when a bisection method is adopted, the division parameter t is 0.5, and the calculation precision e0 is 0.001-0.0001;
3) setting the upper limit value Hh of h1 to 10mm and the lower limit value Hg to 0.1 mm;
4) setting the current thickness h1 ═ Hg + t × (Hh-Hg) of the first bearing block section 3 of the elastomeric snubber casing;
5) obtaining a complete geometric model of the support structure from the current thickness h1 of the first bearing block section 3 and the relevant structural dimensions given in step 1);
6) calculating the rigidity coefficient K of the first bearing block section 3 by adopting a finite element method or a beam theory formula;
7) if | K-K0|/K0E0 is less than or equal to e, then the step 9) is carried out, otherwise, the step 8) is carried out, K is carried out0Presetting a rigidity coefficient according with requirements;
8) if K-K0≦ 0? If Hg is set to h1, go to step 4), otherwise, if Hh is set to h1, go to step 4);
9) outputting a calculation result to obtain the thickness h1 and the rigidity coefficient K of the first bearing block section 3;
10) the thickness h1 of the first bearing block section 3 is kept unchanged, the thickness h2 of the second bearing block section 7 is used as a design variable to replace h1, and then the steps 1) to 9) are repeated, so that the thickness h2 and the rigidity coefficient K of the second bearing block section 7 are obtained.
The present embodiment takes the determination of the stiffness coefficient K of the first bearing block section 3 in FIG. 10 as an example, and the elastic buffer casing is givenThe design step of the rigidity coefficient golden section method (or dichotomy method) is that the structure of the elastic buffer casing has (or gradually approaches) the preset rigidity coefficient K meeting the requirement by selecting the proper thickness h1, namely, taking h1 as the design variable (other parameters are not variable) and carrying out iteration0Therefore, the designed elastic buffer casing has the optimal rigidity coefficient K to prolong the action time of the impact force, so that the power turbine subsystem, the casing and the like are prevented from being damaged by vibration impact, and the complete machine of the aero-engine is ensured to work safely and stably.
Specifically, in the embodiment of the method for designing the stiffness of the bearing support of the elastic buffer casing, a beam theory formula is adopted to calculate the stiffness coefficient K of the first bearing seat section 3, and the method specifically includes the following steps:
selecting a single-section cylindrical beam, two sections of cylindrical beams or three sections of cylindrical beams to perform approximate calculation according to the specific shape of the elastic buffer casing structure and the precision requirement of rigidity calculation;
as shown in fig. 4 and 5, for the simulation of the elastic buffer casing which is nearly cylindrical and adopts a single-section cylindrical beam, the calculation formula of the stiffness coefficient K is as follows:
wherein: r1Is the outer diameter r of a single-section cylindrical beam1The inner diameter of the single-section cylindrical beam is shown, E is the elastic modulus, pi is 3.14159 is the circumference ratio, and L is the length of the single-section cylindrical beam;
as shown in fig. 6, the calculation formula of the stiffness coefficient K of the two cylindrical beams is as follows:
wherein: λ is the compliance coefficient, L1Is two sections of circlesLength, L, of the first section 12 of the column beam2Is the length, R, of the second section 13 of the two sections of cylindrical beams1Is the outer diameter r of the first section 12 of the two sections of cylindrical beams1Is the inner diameter, R, of the first section 12 of the two sections of cylindrical beams2Is the outer diameter r of the second section of the two sections of cylindrical beams 132The inner diameter of the second section of cylindrical beam 13 in the two sections of cylindrical beams meets the following requirements: l is1>L2，r1>r2；
As shown in fig. 7, the calculation formula of the stiffness coefficient K of the three-section cylindrical beam is as follows:
wherein; l is1Is the length, L, of the first section 12 of the three sections of cylindrical beams2Is the length, L, of the second section of the three sections of cylindrical beams 133Is the length, R, of the third section 14 of the three sections of cylindrical beams1Is the outer diameter r of the first section of cylindrical beam 12 in the three sections of cylindrical beams1Is the inner diameter, R, of the first section 12 of the two sections of cylindrical beams2Is the outer diameter r of the second section of cylindrical beam 13 in the three sections of cylindrical beams2The inner diameter of the second section of cylindrical beam 13 in the three sections of cylindrical beams; r3Is the outer diameter, r, of the third section 14 of the three sections of cylindrical beams2The inner diameter of the third section of cylindrical beam 14 in the three sections of cylindrical beams meets the following requirements: l is1>L2>L3，r1>r2>r3；
As shown in fig. 8 and 9, when the structure of the elastic buffer case includes the non-cylindrical beam 10, the stiffness coefficient K of the structure of the elastic buffer case is approximately simulated and calculated using three sections of cylindrical beams. As shown in fig. 8, when the non-cylindrical beam 10 is approximately simulated using the cylindrical beam 11, the cylindrical beam 11 is placed at a middle position of the non-cylindrical beam 10 in the radial direction. As shown in fig. 9, for the structure of the elastic buffer casing including the non-cylindrical beam 10, in the embodiment, the stiffness coefficient K of the structure of the elastic buffer casing is approximately simulated and calculated by three sections of cylindrical beams, that is, the first section of cylindrical beam 12, the second section of cylindrical beam 13, and the third section of cylindrical beam 14, so that the calculation is simplified, and a more accurate stiffness coefficient K can be obtained, thereby providing accurate data for the design of the elastic buffer casing.
The beam theory method is suitable for the situation that the section shape is simple and the ratio (larger than 1) of the length of the buffer casing to the outer radius is large, and the buffer casing with the complex section shape adopts a finite element method to calculate the rigidity coefficient K, so in the embodiment of the rigidity design method of the bearing support of the elastic buffer casing, the process of calculating the rigidity coefficient K of the first bearing seat section 3 by adopting the finite element method is described by taking fig. 10 as an example. FIG. 10 shows a spring-damper casing comprising three sections: the first cylindrical section 16 at the left end, the circular arc transition section 17 in the middle and the second cylindrical section 18 at the right end have two bearings mounted at a first bearing mounting location 19 and a second bearing mounting location 20, respectively: the first cylindrical section 16 has an outer diameter R1, an inner diameter R1, and a thickness h1 ═ R1-R1. The second cylindrical section 18 has an outer diameter R2, an inner diameter R2, and a thickness h2 ═ R2-R2, and the circular arc transition section 17 gradually and uniformly (linearly transits according to the arc length) transits from h1 to h2 in thickness. The rigidity of the first bearing installation position 19 and the rigidity of the second bearing installation position 20 are calculated twice respectively, and the calculation of the beam with the complex cross-sectional shape shown in the figure 10 by adopting the Fourier ring unit specifically comprises the following steps:
1) dividing a finite element mesh into the elastic buffer casing model, and applying boundary conditions, wherein the boundary conditions comprise applying a unit load F1 (or a unit load F2) to the first bearing block section 3 (or the second bearing block section 7), and the unit load F1 (or the unit load F2) is vertically directed to the central axis direction of the elastic buffer casing model; constraining the axial, radial, circumferential displacement of the elastic buffer casing model fixed end 15, thereby generating an elastic buffer casing finite element model (as shown in fig. 11);
2) running a finite element program, selecting a Fourier ring unit, and inputting the generated elastic buffer casing finite element model;
3) inputting material parameters including the elastic modulus E and Poisson ratio mu of the material;
4) setting the Fourier circumferential wave number to be 1;
5) calculating a Fourier ring unit stiffness matrix [ K ], assembling a system overall stiffness matrix [ K ] and a load vector { F }, calling a linear equation set solving module (such as a Gaussian elimination method) to solve a system equation [ K ] { U } ═ { F }, and obtaining a displacement vector { U };
6) and obtaining the displacement value of each node in the outer ring width range of the first bearing 4 near the unit load F1 (or the second bearing 8 near the unit load F2) according to the displacement vector { U }, wherein the average value of the obtained displacement values is the compliance coefficient lambda of the first bearing block section 3 (or the second bearing block section 7), and the reciprocal of the compliance coefficient lambda is the stiffness coefficient K of the first bearing block section 3 (or the second bearing block section 7).
At present, an engine is designed by adopting the elastic buffer casing designed by the method of the embodiment, and the engine is stable in test operation, stable in vibration and free of vibration damage.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. An elastic buffer casing is characterized by comprising a flange subsection (9), a first bearing seat section (3), a transition section (5) and a second bearing seat section (7) in sequence along the axial direction,
the flange subsection (9) is provided with a flange edge (2), and the flange edge (2) is fixedly connected with the outer casing (1) through a bolt, so that one end of the elastic buffer casing is fixed on the outer casing (1);
the inner hole of the first bearing seat section (3) is matched with the excircle of a first bearing (4) arranged on the power output shaft assembly;
the inner hole of the second bearing seat section (7) is matched with the excircle of a second bearing (8) arranged on the power output shaft assembly;
the diameter of the transition section (5) gradually transits from the diameter of the first bearing seat section (3) to the diameter of the second bearing seat section (7) along the axial direction, and the transition section is used for reducing the rigidity coefficient K of the elastic buffer casing, so that the action time of impact force is prolonged, and the purpose of reducing the impact force is achieved.
2. The elastomeric snubber casing of claim 1,
the span M between the central cross section of the first bearing (4) and the mounting edge of the outer casing (1) has the value range as follows: 10 mm-100 mm;
the span N between the central cross section of the second bearing (8) and the mounting edge of the outer casing (1) has the value range as follows: m + (20 mm-100 mm).
3. The elastomeric snubber casing of claim 1, wherein:
the transition section (5) comprises a thickening conical section and an equal-thickness conical section which are sequentially arranged along the axial direction, and the joint of the thickening conical section and the first bearing seat section (3), the joint of the thickening conical section and the equal-thickness conical section and the joint of the equal-thickness conical section and the second bearing seat section (7) are in smooth transition through circular arcs.
4. The elastomeric snubber casing of claim 1,
the longitudinal section profile of the transition section (5) is a circular arc line with the radius of R.
5. The elastomeric snubber casing of claim 4,
the longitudinal section profile of the transition section (5) is an arc line which is concave inwards towards the central axis direction of the elastic buffer casing.
6. The elastomeric snubber casing of claim 4,
the longitudinal section profile of the transition section (5) is in a circular arc shape protruding outwards in the direction far away from the central axis of the elastic buffer casing.
7. The elastomeric snubber casing of any one of claims 4-6,
the transition section (5) is an equal wall thickness transition section or a variable wall thickness transition section, and the thickness of the variable wall thickness transition section is gradually reduced from the first bearing seat section (3) to the second bearing seat section (7).
8. A rigidity coefficient design method of an elastic buffer casing is characterized by comprising the following steps:
1) determining the overall length L of a casing, the inner diameter R1 of a first bearing seat section (3) and the thickness ratio s (H1/H2) to (R1-R1)/(R2-R2) according to the size of a bearing and a rotating shaft and the rotor dynamic requirement, wherein the outer diameter of the first bearing seat section (3) is R1, the thickness h1 is R1-R1, the outer diameter of the second bearing seat section (7) is R2, the inner diameter is R2, and the thickness h2 is R2-R2;
2) determining a division parameter t, and setting a calculation precision e0, wherein when a golden division method is adopted, the division parameter t is 0.618, when a bisection method is adopted, the division parameter t is 0.5, and the calculation precision e0 is 0.001-0.0001;
3) setting the upper limit value Hh of h1 to 10mm and the lower limit value Hg to 0.1 mm;
4) setting a current thickness h1 ═ Hg + t × (Hh-Hg) of the first bearing seat section (3) of the elastomeric snubber casing;
5) obtaining a complete geometric model of the support structure from the current thickness h1 of the first bearing block section (3) and the relevant structural dimensions given in step 1);
6) calculating the stiffness coefficient K of the first bearing block section (3) by adopting a finite element method or a beam theory formula;
7) if | K-K0|/K0E0 is less than or equal to e, then the step 9) is carried out, otherwise, the step 8) is carried out, K is carried out0Presetting a rigidity coefficient according with requirements;
8) if K-K0≦ 0? If Hg is set to h1, go to step 4), otherwise, if Hh is set to h1, go to step 4);
9) outputting the calculation result to obtain the thickness h1 and the rigidity coefficient K of the first bearing block section (3);
10) and (3) keeping the thickness h1 of the obtained first bearing seat section (3) unchanged, replacing h1 with the thickness h2 of the second bearing seat section (7) as a design variable, and repeating the steps 1 to 9 to obtain the thickness h2 and the rigidity coefficient K of the second bearing seat section (7).
9. The stiffness coefficient design method of an elastomeric snubber casing as claimed in claim 8, wherein the process of calculating the stiffness coefficient K of the first bearing block section (3) using a finite element method specifically includes the steps of:
1) dividing a finite element grid into the elastic buffer casing model, and applying boundary conditions, wherein the boundary conditions comprise that a unit load is applied to the first bearing seat section (3), and the unit load vertically points to the central axis direction of the elastic buffer casing model; constraining the axial, radial and circumferential displacement of the fixed end (15) of the elastic buffer casing model so as to generate an elastic buffer casing finite element model;
2) running a finite element program, selecting a Fourier ring unit, and inputting the generated elastic buffer casing finite element model;
3) inputting material parameters including the elastic modulus E and Poisson ratio mu of the material;
4) setting the Fourier circumferential wave number to be 1;
5) calculating a Fourier ring unit stiffness matrix [ K ], an assembled system overall stiffness matrix [ K ] and a load vector { F }, calling a linear equation set solving module to solve a system equation, [ K ] { U } - { F }, and obtaining a displacement vector { U };
6) and obtaining the displacement value of each node in the outer ring width range of the first bearing (4) according to the displacement vector { U }, wherein the average value of the obtained displacement values is the flexibility coefficient lambda of the first bearing seat section (3), and the reciprocal of the flexibility coefficient lambda is the rigidity coefficient K of the first bearing seat section (3).
10. The method for designing the stiffness coefficient of the elastomeric snubber casing as claimed in claim 8, wherein the process of calculating the stiffness coefficient K of the first bearing block section (3) using the beam theory formula includes the steps of:
selecting a single-section cylindrical beam, two sections of cylindrical beams or three sections of cylindrical beams to perform approximate calculation according to the specific shape of the elastic buffer casing structure and the precision requirement of rigidity calculation;
for the simulation of the elastic buffer casing which is close to a cylinder shape and adopts a single-section cylindrical beam, the calculation formula of the rigidity coefficient K is as follows:
wherein: r1Is the outer diameter r of a single-section cylindrical beam1The inner diameter of the single-section cylindrical beam is shown, E is the elastic modulus, pi is 3.14159 is the circumference ratio, and L is the length of the single-section cylindrical beam;
the calculation formula of the rigidity coefficient K of the two sections of cylindrical beams is as follows:
wherein: λ is the compliance coefficient, L1Is the length L of the first section of the two sections of the cylindrical beam (12)2Is the length R of the second section (13) of the two sections of cylindrical beams1Is the outer diameter r of the first section of cylindrical beam (12) in the two sections of cylindrical beams1Is the inner diameter R of the first section of cylindrical beam (12) in the two sections of cylindrical beams2Is the outer diameter r of the second section of cylindrical beam (13) of the two sections of cylindrical beams2The inner diameter of a second section of cylindrical beam (13) in the two sections of cylindrical beams meets the following requirements: l is1>L2，r1>r2；
The calculation formula of the rigidity coefficient K of the three-section cylindrical beam is as follows:
wherein; l is1Is the length L of the first section of cylindrical beam (12) in the three sections of cylindrical beams2Is the length L of the second section of the three sections of cylindrical beams (13)3Is the length, R, of the third section (14) of the three sections of cylindrical beams1Is the outer diameter r of the first section of cylindrical beam (12) in the three sections of cylindrical beams1Is the inner diameter R of the first section of cylindrical beam (12) in the two sections of cylindrical beams2Is the outer diameter r of the second section of cylindrical beam (13) in the three sections of cylindrical beams2The inner diameter of a second section of cylindrical beam (13) in the three sections of cylindrical beams; r3Is the outer diameter r of the third section of the cylindrical beam (14) in the three sections of the cylindrical beam2Is the inner diameter of a third section of cylindrical beam (14) in the three sections of cylindrical beams, and meets the following requirements: l is1>L2>L3，r1>r2>r3；
When the elastic buffer casing structure comprises the non-cylindrical beam (10), the rigidity coefficient K of the elastic buffer casing structure is approximately simulated and calculated by adopting three sections of cylindrical beams.
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