CN110427677B - Rapid design method for elbow structure in external pipeline system of aircraft engine - Google Patents
Rapid design method for elbow structure in external pipeline system of aircraft engine Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L43/00—Bends; Siphons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
- F16L55/02—Energy absorbers; Noise absorbers
- F16L55/033—Noise absorbers
- F16L55/035—Noise absorbers in the form of specially adapted hangers or supports
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Abstract
The invention relates to the field of external accessories of aviation and aerospace equipment, and discloses a method for quickly designing a bent pipe structure in an external pipeline system of an aero-engine, which is used for finishing the lightweight design of the bent pipe structure in the external pipeline system, reducing the vibration fault of the bent pipe structure and increasing the vibration resistance of the bent pipe structure. In the initial design stage of the bent pipe structure in the external pipeline system of the aviation and aerospace equipment, the vibration condition of the bent pipe structure is estimated by the bent pipe structure rapid design method, and the technical variable parameters of the bent pipe structure are optimized according to the estimation result, so that the rapid design of the bent pipe structure is completed. The invention can reduce the design cost, shorten the development period and improve the success rate of installation and arrangement of the bent pipe structure in the external pipeline system.
Description
Technical Field
The invention belongs to the field of external accessories of aviation and aerospace equipment, and relates to a method for quickly designing a bent pipe structure in an external pipeline system.
Background
Aviation, space flight external pipeline structure have a large amount of bent pipe structural style because reasons such as installation space and installation environmental restriction, bent pipe structure includes "Z" type, "L" type, "S" type etc. and bend radius is not unified, and the clamp position is unfixed, and there is very big uncertainty in whole bent pipe structural design. The bent pipe structure can cause the change of the whole rigidity and mass distribution of the pipeline system while changing the trend of the pipeline, so that the inherent characteristics and the vibration behavior of the pipeline system can be changed along with the change of the bent pipe form, which is a place essentially different from a straight pipe system.
The design of the elbow structure in the external pipeline system has no unified design method and evaluation standard, and generally, engineering technicians design the elbow structure by means of personal experience. Usually, CAD modeling and finite element analysis are firstly adopted to process test samples, after actual installation and arrangement, a test run test is carried out, and in order to ensure the vibration requirement of the whole machine, the pipeline structure is optimized according to the test result. If a problem occurs in the initial design stage of the bent pipe structure, the problem can be found only when equipment is subjected to test run, and the equipment is returned to the initial design stage for redesign, so that long modification time is needed, and the production cycle of the product is seriously influenced.
Engineers often do not consider their boundary conditions in the initial design phase of the bent-tube structure. The piping takes over the task of transporting the fluid medium and its working environment is very complex. In the pump source excited bent pipe structure, when the pump source pressure acts on the bent pipe structure, the axial pressure can directly act on the corner of the bent pipe, so that the exciting force of the bent pipe structure is obviously higher than that of a straight pipe, and the vibration of the bent pipe structure is generally higher than that of the straight pipe structure. In the presence of a water hammer impact, the excitation force is increased more significantly, in particular in the case of a fastening with a rubber clamp. The bent pipe structure has the other vibration characteristic that the lower-order natural frequency is relatively low, and resonance and large-amplitude forced vibration are easier to excite.
The pipeline structural design and installation workload is large, the precision cannot be guaranteed, and the experimental test and the theoretical analysis are seriously disconnected. How to analyze and clearly understand the boundary conditions of the bent pipe structure in the initial design stage of the bent pipe structure in an external pipeline system, and design reasonable bent pipe structure parameters, and obtain the optimal bent pipe structure through parameter optimization, so that the vibration characteristics of the bent pipe structure can be comprehensively mastered in the initial design stage without producing test samples, and the vibration estimation is completed, so that the vibration estimation is very necessary to meet the vibration requirements of the whole machine. Therefore, the technical invention of a method for quickly designing the elbow structure in the external pipeline system is very urgent.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method for quickly designing the bent pipe structure in the external pipeline system of the aircraft engine is provided, so that the lightweight design of the bent pipe structure is completed, meanwhile, the vibration fault of the bent pipe structure is avoided to the greatest extent, the vibration resistance of the bent pipe structure is improved, the vibration prediction of the bent pipe structure can be realized, and the vibration requirement of the whole machine is met.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for quickly designing a bent pipe structure in an external pipeline system of an aircraft engine comprises the following steps:
(1) determining vibration index of bent pipe structure
The vibration index of the whole equipment is distributed to various accessory devices including a pump source, an external pipeline system, a bracket, other accessories and the like, and the maximum value of vibration borne by different structural systems is used as the vibration index of the system. The bent pipe has different structural forms and bears different maximum vibration values. And determining the vibration index of the designed bent pipe structure by combining the designed bent pipe structure form including bent pipes, joints, other connecting accessories and the like, and taking the vibration index as the evaluation standard of vibration estimation.
Further, in the initial design stage of the bent pipe structure, the vibration index of the bent pipe bearing structure system is determined according to the vibration index distribution principle. The evaluation standard of the vibration index of the bent pipe structure is 0.8 times lower than the vibration index distributed by the bearing structure system or 1.5 times higher than the vibration index distributed by the bearing structure system.
(2) Determining a bent pipe-hoop system model
According to the model reduction principle, a section of bent pipe supported by two hoops is simplified into a bent pipe-hoop system which serves as a research object, and the boundary conditions of the bent pipe-hoop system comprise a structure boundary condition and a load boundary condition. After the structural boundary conditions and the specific parameters of the load boundary conditions of the elbow-hoop system are determined, simplifying the elbow-hoop system into a single-degree-of-freedom equivalent mass-spring system model with external load force shock excitation, and obtaining the elbow-hoop system model.
Further, the structural boundary conditions are determined by structural characteristics of the elbow-clamp system. The support characteristics of the support band include a rigid support and a resilient support, with different forms of support bands being considered for corresponding equivalent stiffness and equivalent damping in the direction of vibration. In the conventional design, the installation distance of the support clamps is 400mm, the support clamps can be additionally arranged at the bent pipe to increase the rigidity of the system structure, and if the installation environment does not allow, the bent pipe structure needs to be considered to be optimized to change the vibration frequency of the integral bent pipe-clamp system. If no other accessories are connected on the two sides of the researched elbow-hoop system, the body rigidity of the pipeline can be ignored, the pipeline is considered as concentrated mass, and the elbow is considered as model analysis of adding the concentrated mass to the straight pipe. If other accessories are connected to the two sides, including the accessory, the valve body, the pump source and the like, the accessories can be simplified into concentrated mass or concentrated mass plus spring constraint according to the structural characteristics of the accessories.
Further, the load boundary condition is determined according to the parameters of the fluid medium conveyed by the elbow-clamp system and the installation environment. The fluid medium parameters comprise pressure pulsation, flow pulsation, temperature and the like of the fluid medium; the installation environment typically has fundamental vibrations as well as other load vibrations. In the modeling process, the pulsation excitation of the fluid medium and the basic excitation of the installation environment or the vibration excitation of other loads are simplified into the external load force of the single-degree-of-freedom mass-spring system.
(3) Determining bend-clamp system design variables
Design variables include the radius of curvature of the elbow, the bend angle, and the mounting spacing of the support clips, among others. The determination of the design variables is influenced by factors such as the installation environment and the vibration index.
Further, the installation interval of return bend support clamp must satisfy aeroengine pipeline and lay the requirement, and the interval is within 400mm promptly, because aeroengine exterior structure is complicated, and the space is limited, supports the clamp installation interval and hardly guarantees to lay the requirement, needs according to actual installation environment, confirms to support the clamp installation interval.
Further, after the installation intervals of the support hoops are determined, when the direction of a pipeline connected between the installation intervals of the support hoops is designed, the structure of the installation casing limits, the bending radius and the bending angle of the bent pipe cannot be selected at will, namely the designed bent pipe structure cannot be designed at will, and the bending radius and the bending angle can only be determined under the installation condition according with the installation condition of the casing structure.
Further, according to the installation environment and the installation conditions, design variables such as the curvature radius and the bending angle of the bent pipe in the bent pipe-hoop system, the installation distance of the supporting hoop and the like are preliminarily determined, and different design variables can cause the change of the whole rigidity and the mass distribution of the bent pipe-hoop system, so that the vibration characteristic of the bent pipe-hoop system is influenced.
(4) Optimizing vibration parameters of a pipe-clamp system
Preliminarily determining design variables, simplifying the bent pipe-hoop system into an equivalent mass-spring system model, and carrying out vibration parameter optimization design on the bent pipe-hoop system by taking the optimal system vibration amount as a target. By optimizing the vibration parameters of the bent pipe-hoop system model, the vibration characteristics of the system meet the vibration indexes.
Further, in a pipeline bending area in the middle of the bent pipe-hoop system, because the hoop support span is increased, when the pipeline vibrates, the natural frequency of the system is reduced due to the influence of concentrated mass in the middle area, and the vibration of the pipeline is intensified. The equivalent mass of the system in the vibration process caused by the bending structure of the bent pipe is larger than the real mass, and strong vibration is caused, which is defined as the equivalent mass effect of the bent pipe. The equivalent mass of the system is significantly greater than the true mass of the pipeline.
Further, the vibration parameters of the elbow-hoop system model comprise equivalent mass mdAnd equivalent stiffness kdAnd the like. Equivalent mass m of the systemdFrom the true mass m of the bendpAnd a simplified lumped mass meThe equivalent mass is as follows:
md＝mp+me
in the vibration process of the bent pipe-hoop system, because the first-order vibration mainly takes bending vibration in the vertical direction as the main vibration, the system rigidity is determined by the support rigidity in the vertical direction of the hoop. The support rigidity of the hoops at the two ends of the system along the vertical direction is respectively ky1And ky2Since the clamp models are the same and the characteristics are the same, k isy1＝ky2The hoops at the two ends are connected in parallel, so that the equivalent rigidity k is achievedd：
kd＝ky1+ky2；
Equivalent mass m of the systemdCan be obtained by carrying out vibration analysis on a single-degree-of-freedom mass-spring system according to the vibration index of the bent pipe structure, and further can obtain the concentrated mass me. Through parameter optimization calculation, the optimal centralized mass value can be obtained, the optimal design variable of the bent pipe structure can be further determined, and then the quick design of the bent pipe structure is completed.
(5) Evaluation of vibration index of bent pipe-hoop system
And if the optimized vibration parameters of the bent pipe-hoop system meet the distribution result of the vibration indexes of the whole machine, the vibration indexes of the bent pipe-hoop system are qualified, and the design is finished.
And (4) if the optimized vibration parameters of the bent pipe-hoop system do not meet the distribution result of the vibration indexes of the whole machine, indicating that the vibration indexes of the bent pipe-hoop are unqualified, returning to the step (3) to re-confirm the design variables until the design requirements are met and the design is finished.
The invention has the beneficial effects that:
in the initial design stage of the bent pipe structure, the boundary conditions and the design variables of the bent pipe structure and the simplified system parameters such as the equivalent mass and the equivalent rigidity of the bent pipe-hoop system are determined, and the vibration parameters of the bent pipe-hoop system are optimally designed, so that the vibration indexes are met, the design and manufacturing period of the bent pipe-hoop system is shortened, the reliability of the bent pipe structure is improved, and the rapid design of the bent pipe structure is finally completed.
Drawings
Fig. 1 is a flowchart of a technical solution for rapidly designing a bent pipe structure in an external pipe system according to an embodiment of the present invention.
Fig. 2 is a mechanical diagram of an elbow-clamp system and a simplified mechanical diagram of an elbow-clamp system equivalent to a straight pipe plus a lumped mass according to an embodiment of the invention. FIG. 2(a) is a simplified mechanical diagram of a pipe-clamp system, wherein k isx1Denotes the one-side support hoop support stiffness in the x-direction, kx2Representing the support stiffness, k, of the other side of the hoop in the x-directiony1Denotes one-side support hoop y-direction support stiffness, ky2Showing the support rigidity of the other side support hoop in the y direction; FIG. 2(b) is a simplified mechanical diagram of an elbow-clamp system equivalent to a straight pipe plus concentrated mass, where meRepresenting a simplified quality of concentration.
Fig. 3 is a model of a single degree of freedom equivalent mass-spring system with out-of-band loading force for a bent tube-clamp system in an embodiment of the present invention. In the figure, kdRepresenting the equivalent support stiffness of the system, c representing the equivalent damping of the system, mdRepresenting the equivalent mass of the system, F0cos (Ω t) represents the equivalent external load force of the system.
Detailed description of the preferred embodiments
The invention aims to provide a method for quickly designing a bent pipe structure in an external pipeline system, which can realize the vibration estimation of the bent pipe structure at the initial design stage of the bent pipe structure in the external pipeline system, complete the lightweight design of the bent pipe structure, avoid the vibration fault of the bent pipe structure, improve the vibration resistance of the bent pipe structure and enable the vibration characteristic of the bent pipe structure to meet the vibration requirement of the whole machine.
The solution of the invention is further described below with reference to the accompanying figure 1 and examples:
(1) in the initial design stage of the elbow structure, the maximum value of vibration borne by different accessory device structural systems of the external structure of the aircraft engine is used as the vibration index of the structural system. Firstly, the vibration index of the whole equipment is distributed to various accessory devices including a pump source, an external pipeline system, a bracket and other accessories. And determining the vibration index of the designed bent pipe structure by combining the designed bent pipe structure form including bent pipes, joints, other connecting accessories and the like, and taking the vibration index as the evaluation standard of vibration estimation.
The characteristics of the supporting hoop are considered, and the supporting hoop is used as a bearing structure of the bent pipe structure to form a bent pipe-hoop system. The vibration index evaluation standard of the bent pipe-hoop system is lower than 0.8 times of the distributed vibration index or higher than 1.5 times of the distributed vibration index.
(2) After the vibration index of the bent pipe-hoop system is obtained, a section of bent pipe supported by the two hoops is simplified into the bent pipe-hoop system to be used as a research object, and the structural boundary condition and the load boundary condition of the system are further determined.
The structural boundary conditions are determined by the structural characteristics of the elbow-clamp system. The support characteristics of the band include a rigid support and a resilient support, with different forms of support bands being considered for corresponding equivalent stiffness and equivalent damping in the direction of vibration. In the conventional design, the installation distance of the support clamps is 400mm, the support clamps can be additionally arranged at the bent pipe to increase the rigidity of the system structure, and if the installation environment does not allow, the bent pipe structure needs to be considered to be optimized to change the vibration frequency of the integral bent pipe-clamp system.
If no other accessories are connected on the two sides of the support hoop of the elbow-hoop system, the two sides of the support hoop of the elbow-hoop system are only simple pipelines, and according to experimental test analysis, the pipelines on the outer side of the support hoop do not influence the vibration characteristic of the elbow-hoop system, namely, a section of elbow supported by two hoops is simplified into the elbow-hoop system according to a model reduction principle and serves as a research object, so that the structure of the elbow-hoop system can be simplified in the analysis process, and a mechanical diagram of the elbow-hoop system can be established, as shown in an attached figure 2 (a). Because the support rigidity of the hoop is far less than the rigidity of the pipe body, the rigidity of the body of the pipeline is ignored, the pipeline is considered as concentrated mass, and the bent pipe is considered as model analysis of a straight pipe and concentrated mass, as shown in the attached figure 2 (b). If other accessories are connected to the two sides, the accessories can be simplified into concentrated mass or concentrated mass plus spring constraint according to the structural characteristics of the accessories.
The load boundary condition is determined according to the parameters of the fluid medium conveyed by the elbow-clamp system and the installation environment. The parameters of the conveyed fluid medium comprise pressure pulsation, flow pulsation, temperature and the like of the fluid. The installation environment of the elbow-clamp system typically presents fundamental vibrations as well as other load vibrations. After the structural boundary conditions of the elbow-hoop system are clarified, in the modeling process, the pulsation excitation of the fluid medium, the basic excitation of the installation environment and other external load excitations are simplified into the external load force of the system, and the system is simplified into a single-degree-of-freedom equivalent mass-spring system model with the external load force excitation, as shown in fig. 3.
(3) And after the boundary conditions of the system are clarified, further designing the design variables of the finished bent pipe structure. Design variables include the radius of curvature of the elbow, the bend angle, and the mounting spacing of the support clips, among others. The determination of the design variables is influenced by factors such as the installation environment and the vibration index.
The installation interval of the bent pipe support hoop must meet the requirement of laying the pipeline of the aircraft engine, namely the interval is within 400mm, and because the external structure of the aircraft engine is complex and the space is limited, the installation interval of the support hoop is difficult to guarantee the laying requirement, and the installation interval of the support hoop needs to be determined according to the actual installation environment.
After the installation distance of the support clamp is determined, when the direction of a pipeline connected between two connecting points is designed, the design variable cannot be selected at will due to the limitation of the position of an installation casing and the vibration evaluation index. Design variables of the pipe bending-hoop system directly influence the centralized quality m of the system modeleAnd thus the vibration characteristics of the elbow-clamp system.
(4) After the design variables are determined, the vibration parameter optimization design of the bent pipe-hoop system is carried out by taking the simplified vibration characteristic optimization of the equivalent mass-spring system as a target. By optimizing the vibration parameters of the bent pipe-hoop system model, the vibration characteristics of the system meet the evaluation standard of vibration indexes.
In the pipeline bending area in the middle of the elbow-hoop system, because the hoop support span is increased, when the pipeline vibrates, the natural frequency of the system is reduced due to the influence of concentrated mass in the middle area, and the vibration of the pipeline is intensified. The vibration parameters of the elbow-hoop system model comprise equivalent mass, equivalent rigidity and the like. Equivalent mass m of the systemdFrom the true mass m of the bendpAnd a simplified lumped mass meThe equivalent mass is as follows:
md＝mp+me
through experimental tests, the vibration frequency of the aircraft engine is mostly below 300Hz, the first-order dominant frequency vibration of the pipeline-clamp system is mostly between 100 Hz and 200Hz, and therefore, the vibration in the vertical direction is mainly analyzed in the vibration process of the elbow-clamp systemThe first order bending vibration is dominant, and the system stiffness is determined by the support stiffness in the vertical direction of the clamp. The support rigidity of the hoops at the two ends of the system along the vertical direction is respectively kx1And kx2Because the clamp model is the same, the characteristic is the same, then has:
kx1＝kx2。
for example, a 12mm diameter unigang elbow-clamp system was analyzed using an elastomeric clamp for the support clamp with a support stiffness of 1.131 x 105N/m, the shape of the bent pipe is Z-shaped, the outer diameter is 12mm, the inner diameter is 10mm, and the density of the pipe is 7800kg/m3The length of the bent pipe is 0.81m, and the bent pipe is excited by an electromagnetic vibration table. The first-order natural frequency f of the system can be determined by carrying out frequency sweep and fixed frequency tests on the bent pipe-hoop systemn69.12Hz, 34.19g vibration response amplitude a, and the system equivalent mass is obtained by the system natural frequency formula
Calculated, the true mass m of the pipelinep0.218kg, and the equivalent mass m of the systemdThe equivalent mass of the system is significantly greater than the true mass of the pipeline at 0.623kg, and therefore, the equivalent mass of the system can be considered to be the true mass m of the pipelinepAnd a simplified lumped mass meOf composition, i.e. having mass value me＝0.405kg。
Therefore, in the middle pipeline bending area of the pipe bending system, the hoop support span is increased, when the pipeline vibrates, the natural frequency of the system is reduced due to the influence of concentrated mass in the middle area, and the vibration of the pipeline is intensified. The equivalent mass of the system caused by the bent structure of the pipeline is larger than the real mass in the vibration process, and the phenomenon of strong vibration is caused, which is defined as the equivalent mass effect of the bent pipe.
Equivalent mass m of the systemdCan be obtained by carrying out vibration analysis on a single-degree-of-freedom mass-spring system according to the vibration index of the bent pipe structure, and further can obtain the concentrated mass me. Through parameter optimization calculation, the optimal centralized mass value can be obtained, the optimal design variable of the bent pipe structure can be further determined, and then the quick design of the bent pipe structure is completed.
(5) The vibration characteristics of the equivalent mass-spring system model generated by simplifying the bent pipe-hoop system meet the set evaluation standard of the vibration index. And if the optimized vibration parameters of the bent pipe-hoop system meet the distribution result of the vibration indexes of the whole machine, the vibration indexes of the bent pipe-hoop system are qualified, and the design is finished. If the optimized vibration parameters of the bent pipe-hoop system do not meet the distribution result of the vibration indexes of the whole machine, the vibration indexes of the bent pipe-hoop are unqualified, and the design variables need to be confirmed again until the design requirements are met and the design is finished.
The above-mentioned embodiments only express the embodiments of the present invention, but not should be understood as the limitation of the scope of the invention patent, it should be noted that, for those skilled in the art, many variations and modifications can be made without departing from the concept of the present invention, and these all fall into the protection scope of the present invention.
Claims (1)
1. A method for quickly designing a bent pipe structure in an external pipeline system of an aircraft engine is characterized by comprising the following steps:
(1) determining vibration index of bent pipe structure
Distributing the vibration index of the whole equipment to each accessory device, and taking the maximum value of the vibration born by different structural systems as the distributed vibration index; in the initial design stage of the bent pipe structure, the vibration index of the designed bent pipe structure is determined according to the vibration index distribution principle by combining the designed bent pipe structure form, and the vibration index is used as the evaluation standard of vibration estimation;
the evaluation standard of the vibration index of the bent pipe structure is 0.8 times lower than the vibration index distributed by the bearing structure system or 1.5 times higher than the vibration index distributed by the bearing structure system;
(2) determining a bent pipe-hoop system model
Simplifying a section of bent pipe supported by two hoops into a bent pipe-hoop system according to a model reduction principle, wherein the bent pipe-hoop system is used as a research object, and the boundary conditions of the bent pipe-hoop system comprise a structure boundary condition and a load boundary condition; after the boundary condition and the specific load boundary parameter of the bent pipe-hoop system structure are determined, simplifying the bent pipe-hoop system into a single-degree-of-freedom equivalent mass-spring system model with external load force shock excitation, namely determining a bent pipe-hoop system model;
the structural boundary condition is determined by the structural characteristics of the bent pipe-hoop system; the support characteristics of the support clamp include rigid support and elastic support, and the support clamps of different forms are considered as corresponding equivalent rigidity and equivalent damping in the vibration direction; if no other accessories are connected on the two sides of the researched bent pipe-hoop system, the body rigidity of the pipeline can be ignored, the pipeline is considered as concentrated mass, and the bent pipe is considered as model analysis of adding the concentrated mass to the straight pipe; if other accessories are connected to the two sides, the accessories can be simplified into concentrated mass or concentrated mass plus spring constraint according to the structural characteristics of the accessories;
the load boundary condition is determined according to the parameters of the fluid medium conveyed by the elbow-clamp system and the installation environment; in the modeling process, the pulsating excitation of a fluid medium and the basic excitation of an installation environment or the vibration excitation of other loads are simplified into the external load force of a single-degree-of-freedom mass-spring system; the fluid medium parameters comprise pressure pulsation, flow pulsation and temperature of the fluid medium; the installation presents foundation vibrations and other load vibrations;
(3) determining bend-clamp system design variables
The design variables comprise the curvature radius and the bending angle of the bent pipe and the installation distance of the support hoop, and the determination of the design variables is influenced by the installation environment and the vibration index factors; the installation distance of the bent pipe support hoop meets the laying requirements of an aircraft engine pipeline, and the installation distance of the support hoop is determined according to the actual installation environment; after the installation intervals of the support hoops are determined, when the trend of pipelines connected between the installation intervals of the support hoops is designed, under the condition of conforming to the installation condition of a casing structure, the bending radius and the bending angle are determined;
(4) optimizing vibration parameters of a pipe-clamp system
Preliminarily determining design variables, simplifying a bent pipe-hoop system into an equivalent mass-spring system model, and carrying out vibration parameter optimization design on the bent pipe-hoop system by taking the optimal system vibration quantity as a target; the vibration parameters of the bent pipe-hoop system model are optimized, so that the vibration characteristics of the system meet the vibration indexes;
the vibration parameters of the bent pipe-hoop system model comprise equivalent mass mdAnd equivalent stiffness kd；
The equivalent mass mdFrom the true mass m of the bendpAnd a simplified lumped mass meThe equivalent mass is as follows:
md＝mp+me
in the vibration process of the bent pipe-hoop system, the first-order vibration mainly takes bending vibration in the vertical direction as the main vibration, and the system rigidity is determined by the support rigidity in the vertical direction of the hoop; the support rigidity of the hoops at the two ends of the system along the vertical direction is respectively ky1And ky2Since the clamp models are the same and the characteristics are the same, k isy1＝ky2The hoops at the two ends are connected in parallel, so that the equivalent rigidity k is achievedd：
kd＝ky1+ky2；
Equivalent mass m of the systemdCan be obtained by carrying out vibration analysis on a single-degree-of-freedom mass-spring system according to the vibration index of the bent pipe structure, and further can obtain the concentrated mass me(ii) a Through parameter optimization calculation, the optimal concentration mass m can be obtainedeNumerical values, so that the optimal design variable of the bent pipe structure can be determined, and then the rapid design of the bent pipe structure is completed, namely the design variable optimization of the curvature radius, the bending angle and the installation distance of the support clamp of the pipeline is completed;
(5) evaluation of vibration index of bent pipe-hoop system
If the optimized vibration parameters of the bent pipe-hoop system meet the distribution result of the vibration indexes of the whole machine, the vibration indexes of the bent pipe-hoop system are qualified, and the design is finished;
and (4) if the optimized vibration parameters of the bent pipe-hoop system do not meet the distribution result of the vibration indexes of the whole machine, indicating that the vibration indexes of the bent pipe-hoop are unqualified, returning to the step (3) to re-confirm the design variables until the design requirements are met and the design is finished.
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