阅读说明：本技术 一种考虑挤压油膜阻尼器的发动机转子动平衡方法及系统 (Dynamic balance method and system of engine rotor considering squeeze film damper ) 是由 谷宇 *** 李维博 于 2019-10-09 设计创作，主要内容包括：本发明实施例提供了一种考虑挤压油膜阻尼器的发动机转子动平衡方法及系统,涉及发动机转子动平衡技术领域,以解决现有的动平衡技术中存在的无法有效平衡带有挤压油膜阻尼器的转子系统的振动这个问题。通过曲线交叉法,得出目标阻尼器在实际工况下的离心率,并利用运动微分方程,将阻尼器非线性阻尼力转化成等效刚度和阻尼,解决在转子工作过程中阻尼器轴颈的进动位移和挤压油膜产生的阻尼力之间的非线性关系问题,能够求得转子系统各节点处的振动情况。以此为基础,开发基于双转速、双平衡面的影响系数法的动平衡程序,构建相应的程序界面,通过选取阻尼器非线性特性较弱时的两平衡转速,对转子系统进行动平衡,取得了较好的平衡效果。(The embodiment of the invention provides a dynamic balance method and system of an engine rotor considering a squeeze film damper, relates to the technical field of dynamic balance of the engine rotor, and aims to solve the problem that the vibration of a rotor system with the squeeze film damper cannot be effectively balanced in the conventional dynamic balance technology. The eccentricity of a target damper under the actual working condition is obtained through a curve intersection method, the nonlinear damping force of the damper is converted into equivalent rigidity and damping through a motion differential equation, the problem of nonlinear relation between the precession displacement of a damper journal and the damping force generated by an extrusion oil film in the working process of a rotor is solved, and the vibration condition of each node of a rotor system can be obtained. Based on the dynamic balance program, a dynamic balance program based on an influence coefficient method of double rotating speeds and double balance surfaces is developed, a corresponding program interface is constructed, and the dynamic balance is carried out on the rotor system by selecting the two balance rotating speeds when the nonlinear characteristic of the damper is weaker, so that a better balance effect is obtained.)

1. A dynamic balancing method of an engine rotor considering a squeeze film damper is characterized in that the dynamic balancing method can perform dynamic balancing on a real engine rotor system with the squeeze film damper.

In the case of a squeeze film damper, the excitation and time of the system are considered as a function of time, and at time t, the differential equation of motion of the rotor is generally expressed as:

wherein, F_tThe method not only comprises unbalanced force, but also comprises damping force generated by a damper squeezing an oil film, and the damping force and the precession displacement of the journal are in a nonlinear relation.

After determining the functional relationship, the method further comprises: determining the actual eccentricity of the damper at a certain moment based on a curve intersection method, converting the damping force of the damper changing along with the precession displacement of the shaft neck into equivalent rigidity and equivalent damping under the condition of determining other damper parameters, wherein the correlation between the bearing and the damper is represented as follows:

subscripts s and b respectively represent nodes of the bearing and the damper, nonlinear damping force of the damper can be obtained through expansion, arrangement and deformation of the matrix, the equation after the nonlinear damping force is converted into equivalent rigidity and equivalent damping can be obtained, and the equation is brought into a motion differential equation of the rotor, and the motion differential equation of the whole rotor system with the SFD after the damping force is equivalent can be obtained.

And based on the conversion relation, obtaining the vibration response of each node in the rotor system, including the vibration condition of the damper.

2. The method as claimed in claim 1, wherein for the case that the critical rotation speed changes with the change of the unbalance amount and the vibration response and the lag angle change nonlinearly with the linear change of the unbalance amount in the rotor system with the damper, the two rotation speeds with weaker influence of the nonlinear characteristic of the damper are selected as the balance rotation speed in the subsequent dynamic balance, thereby avoiding the vibration sudden change, the lag angle change and other nonlinear conditions possibly caused by the change of the unbalance amount and ensuring the stability of the influence coefficient.

3. The method for dynamically balancing the engine rotor with the squeeze film damper as claimed in claim 1, wherein the two balancing rotation speeds are selected based on the condition that the nonlinear characteristic of the damper is weak, and the engine rotor system with the squeeze film damper is dynamically balanced by combining the influence coefficient method of the double rotation speeds and the double balancing surfaces.

4. A squeeze film damper-considered dynamic balancing system for an engine rotor, comprising the squeeze film damper-considered dynamic balancing method for an engine rotor according to any one of claims 1 to 4. The dynamic balance program interface of the engine rotor system considering the squeeze film damper is provided, an engine rotor system model can be introduced into the interface, and the vibration condition of each node of the rotor system is obtained based on a curve intersection method and a related motion differential equation.

5. The system of claim 4, wherein the system interface further obtains the balance weight value after dynamic balance by inputting relevant condition parameters of the influence coefficient method.

Technical Field

The invention relates to the field of dynamic balance of an engine rotor, in particular to dynamic balance of a nonlinear rotor system with a squeeze film damper.

Background

With the rapid development of industrialization in China, the application of the rotary machine in the aerospace field is increasingly wide, and as an important component of the rotary machine, the balance of a rotor plays a very critical role in whether the rotary machine can stably and safely operate. The unbalance of the rotor can be caused by the reasons of non-standard design and manufacture, non-uniform material distribution, inaccurate installation and positioning and the like, and the rotor can vibrate violently under the action of the unbalance force, so that more serious problems are caused.

In recent years, the dynamic balance technology of the rotor is developed rapidly, and the dynamic balance method which is widely applied at present has an influence coefficient method and a vibration mode balance method, and the dynamic balance method is applied to a linear rotor system. The influence coefficient method can balance a plurality of vibration modes at the same time, is more convenient to balance the shafting, can utilize computer-aided balance, and is convenient to realize the automation of data processing. However, the number of times of starting the balance at a high rotation speed is large, and in the case of a high-order mode shape, the sensitivity is lowered, and a correct correction amount may not be obtained in some cases by using a non-independent balance plane. The mode balance method needs to measure the mode of each step of the rotor, so that the vibration of the rotor must be directly measured. For general aeroengines, there are many inconveniences to measure the vibration mode of the rotor in the machine, so the method is more suitable for the dynamic balance of the rotor of the tester in the development of the tester and the engine.

In the development process of modern aeroengines, the high thrust-weight ratio and wide adaptability are more and more emphasized, so that the structure is more and more flexible, and the load is more and more increased in the working process, which can cause the vibration of the engine to be intensified. In order to reduce vibration of the whole system, a squeeze film damper is added on an engine rotor to provide damping, so that a vibration reduction effect is achieved. However, due to the existence of the squeeze film damper, the rotor system has nonlinear characteristics, and therefore, research on a balance method of the rotor system is necessary.

Disclosure of Invention

In view of the above, the present invention provides a dynamic balancing method and system for an engine rotor considering a squeeze film damper, which solves the dynamic balancing problem of a nonlinear rotor system with a squeeze film damper.

The embodiment of the invention provides a dynamic balance method of an engine rotor considering a squeeze film damper, which comprises the following steps:

in a rotor system with squeeze film dampers, excitation and time are considered as a function of time, and at time t, the differential equation of motion of the rotor is generally expressed as:

wherein, F_tThe method not only comprises unbalanced force, but also comprises damping force generated by a damper squeezing an oil film, and the damping force and the shaft neck precession displacement are in a nonlinear relation.

After the functional relationship is determined, further, the actual eccentricity of the damper at a certain moment is determined based on a curve intersection method, under the condition that other damper parameters are determined, the damping force of the damper changing along with the precession displacement of the shaft neck is converted into the equivalent rigidity and the equivalent damping at the moment, and the mutual relationship between the bearing and the damper is expressed as follows:

subscripts s and b respectively represent nodes of the bearing and the damper, nonlinear damping force of the damper can be obtained through expansion, arrangement and deformation of the matrix, the equation after the nonlinear damping force of the damper is converted into equivalent rigidity and equivalent damping can be obtained, the equation is brought into a motion differential equation of the rotor, and the integral motion differential equation of the rotor with the SFD after the damping force is equivalent is obtained.

And obtaining the vibration response of each node in the rotor system based on the conversion relation, wherein the vibration response comprises the vibration condition of the damper.

Further, after determining the vibration condition of each node of the rotor system based on the curve crossing method, the method further comprises the following steps:

aiming at the condition that in a rotor system with a damper, the critical rotating speed can change along with the change of the unbalance amount, and the vibration response and the lag angle can both change along with the linear change of the unbalance amount in a nonlinear mode, in the method, two rotating speeds with weaker influence of the nonlinear characteristic of the damper are selected as the subsequent dynamic balance rotating speed, so that the vibration sudden change, the lag angle change and other nonlinear conditions possibly caused along with the change of the unbalance amount are avoided, and the stability of an influence coefficient is ensured.

Further, two balance rotating speeds are selected under the condition that the nonlinear characteristic of the damper is weak, and the dynamic balance is carried out on the engine rotor system with the squeeze film damper based on the influence coefficient method of the double rotating speeds and the double balance surfaces.

The embodiment of the invention also provides a dynamic balance program interface of the engine rotor system considering the squeeze film damper, wherein an engine rotor system model can be introduced into the interface, and the dynamic characteristic analysis of the rotor system is carried out based on a curve intersection method to obtain the vibration response of each node.

Furthermore, the interface can also obtain a counterweight value obtained through dynamic balance under the condition of the initial unbalance of the rotor system by inputting relevant condition parameters of an influence coefficient method, so that a balance effect is achieved.

Compared with the prior art, the dynamic balance method and the dynamic balance system have the following advantages:

the dynamic balance method is implemented on the basis of accurate rotor dynamics analysis results of the damper with the squeeze film. The eccentricity corresponding to the damper under the actual working condition is obtained through a curve intersection method, the nonlinear relation between the movement displacement of the shaft neck and the damping force of the squeeze film is converted into equivalent rigidity and equivalent damping, the vibration condition of each node of the rotor system with the SFD is obtained through solving a movement differential equation, and a good premise is provided for comparison of the dynamic balance result of the next step.

The dynamic balance method is based on a double-rotating-speed and double-balance-surface influence coefficient method, two balance rotating speeds under the condition that the influence of the nonlinear characteristic of the damper is weak are selected, the relationship between the vibration response and the change of the lag angle and the unbalance amount under the condition is approximately the same as that of a linear system without the damper, the influence of the damper is considered in the vibration response, the influence of the nonlinear characteristic of the damper is weakened in the balance, and a good effect is obtained after the balance.

The engine rotor system is based on a certain real engine rotor structure, and the hollow unequal-section structure is more suitable for the actual situation. The system is provided with an extrusion oil film damper supported by a central spring, and the central spring has certain rigidity and plays a role in preventing the rotation of the journal while supporting the journal. The damper has certain length and diameter, and a certain gap is reserved between the shaft neck and the bearing seat, so that viscous lubricating oil is filled in the gap, the damper provides damping, and the damping effect is achieved; the support mode of the bearing adopts a 1-1-0 structure, and the damper and one of the rolling bearings are connected in series at the first support.

Based on the method and the system, a dynamic balance program interface is established, the functions are completed in the interface, and the dynamic balance work of the rotor system with the SFD is convenient.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a flow diagram for dynamic balancing of an engine rotor system with squeeze film dampers;

FIG. 2 is a schematic illustration of the relationship between the bearing and the damper;

FIG. 3 is a schematic diagram of solving eccentricity under an objective function by using a curve intersection method;

FIG. 4 is a dynamic analysis comparison result of the rotor system after converting the nonlinear damping force in the rotor motion differential equation into equivalent stiffness and equivalent damping based on a curve crossing method.

Fig. 5 is a dynamic balance program interface under two rotating speeds and two balance surfaces based on an influence coefficient method according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a two-dimensional finite element model of an engine rotor according to an embodiment of the present invention;

FIG. 7 is a graph showing the variation of the nonlinear characteristics of the rotor with different amounts of unbalance, according to the embodiment of the present invention;

fig. 8 is a comparison of vibration conditions before and after dynamic balance under double rotating speed and double balance surfaces based on an influence coefficient method according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as presented in the figures, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.

First, we introduce an application scenario to which the present application is applicable. The method can be applied to national defense and aerospace systems, and the aero-engine rotor system with the squeeze film damper is subjected to dynamic balance so as to reduce the vibration of the engine rotor system, thereby achieving the purpose of safe and stable operation of the system.

Firstly, a two-dimensional finite element model diagram of a certain real engine rotor system with the SFD is established, the actual eccentricity of a damper at a certain time is determined based on a curve crossing method, and under the condition that other damper parameters are determined, the damping force of the damper changing along with the precession displacement of a shaft neck is converted into equivalent rigidity and equivalent damping which are respectively brought into a rigidity matrix and a damping matrix on the left side of an equation. Through the transformation relation, the vibration response of each node in the rotor system, including the vibration condition of the damper, can be obtained.

Further, different unbalanced excitation forces are applied to the rotor system, and nonlinear change conditions of vibration response of two bearing nodes, a lag angle and eccentricity of the damper along with rotation speed change are obtained. And selecting two balance rotating speeds within the rotating speed range with less influence of the nonlinear characteristic of the damper.

Furthermore, based on a double-rotating-speed and double-balance-surface influence coefficient method, under the condition that the nonlinear characteristic of the damper is considered, two balance rotating speeds with weak nonlinear characteristic action are selected to balance a certain real engine rotor structure, and the effectiveness of the method in dynamic balance of the rotor system with the SFD is shown through comparison of results before and after balance.

Further, based on the above, a dynamic balance program interface is established, the functions of the dynamic balance method and system are utilized in the interface, and the result is obtained by directly inputting parameters on the interface, so that the dynamic balance work is more convenient and faster.

Fig. 2 shows a schematic diagram of the relationship between the bearing and the damper, and the rotor system is excited by the damping force of the squeeze film damper in addition to the unbalanced force during the operation, and the excitation and the time are regarded as a certain functional relation, and at the time t, the motion differential equation of the rotor is generally expressed as:

wherein, F_tThe method not only comprises unbalanced force, but also comprises damping force generated by a damper squeezing an oil film, and the damping force and the shaft neck precession displacement are in a nonlinear relation.

After determining the functional relationship, the method further comprises: determining the actual eccentricity of the damper at a certain moment based on a curve intersection method, converting the damping force of the damper changing along with the precession displacement of the shaft neck into equivalent rigidity and equivalent damping under the condition of determining other damper parameters, wherein the correlation between the bearing and the damper is represented as follows:

through the expansion, the arrangement and the deformation of the matrix, an equation obtained after the nonlinear damping force of the damper is converted into the equivalent rigidity and the equivalent damping is brought into a motion differential equation of the rotor, and the integral motion differential equation of the rotor with the SFD after the damping force is equivalent is obtained. And solving the equation to obtain the vibration condition of each node of the rotor system.

Fig. 3 shows a curve intersection method, which is a novel nonlinear solution method, based on the correlation between the precession displacement of the damper journal and the related damping characteristic parameters, the eccentricity of the damper journal varies within the range of 0 to 1, and at any point within the range, the damper characteristic parameters corresponding to the journal position can be calculated, and these calculated values form a characteristic curve of the damper, where curve a is the characteristic curve of the target damper, curve B is the characteristic curve of the damper under an ideal condition, and is a straight line with a slope of 1. The intersection point of the two lines is the steady state solution of the target damper, i.e., the eccentricity of the damper under actual conditions.

Fig. 4 shows a comparison diagram of two bearing nodes under two conditions with and without dampers, when dampers exist in a rotor system, the critical rotation speed and vibration response of a rotor can be effectively reduced, the vibration reduction effect is achieved, and meanwhile, the analysis result of the rotor dynamics program with the squeeze film damper based on the curve crossing method developed in the text is verified to be correct.

Fig. 5 shows a dynamic balance program interface under double rotating speed and double balance surfaces based on an influence coefficient method, test weights with the sizes of 0.2kg.mm and 0.15kg.mm and phase angles of 30 degrees and 60 degrees are applied at a node 5 and a node 25 respectively, and the counterweight values of the two balance surfaces are displayed in the program interface through analysis and calculation.

FIG. 6 shows a schematic diagram of a two-dimensional finite element model of an engine rotor with SFD, the rotor is of a hollow unequal-section structure and better accords with the actual condition of the engine rotor, and comprises a 14-stage compressor and a 2-stage turbine, the support mode of a bearing is 1-1-0, and an extrusion film damper is arranged at the 1 st support position and is connected with a rolling bearing in series. The damper is supported by a central spring, and the central spring has certain rigidity and plays a role in preventing the journal from rotating while supporting the journal. The damper has certain length and diameter, and a certain gap is formed between the shaft neck and the bearing seat, so that viscous lubricating oil is filled in the gap, and when the shaft neck precesses, a vibration damping effect is generated by squeezing an oil film.

Fig. 7 is a graph showing the nonlinear characteristic change curves of two bearing nodes of the rotor under different unbalance amounts with the damper, when the damper exists, the critical rotating speed at the two bearing nodes changes under different unbalance amounts, the response amplitude changes nonlinearly with the linear increase of the unbalance amount, and in addition, the phase lag angle changes in a certain middle rotating speed range, which shows that the influence coefficient of the rotor system under the same balance rotating speed changes, so that the rotor system is not suitable for dynamic balance by using the influence coefficient method in the rotating speed range. Furthermore, when the initial imbalance increases from 1kg.mm to 2kg.mm, the eccentricity at the damper node changes significantly, especially near the critical speed, and the non-linear characteristic is significant when the eccentricity of the damper is greater than 0.4.

Further, we selected the initial unbalance size to be 0.1kg.mm, the phase to be 0 °, and the selected balance rotation speeds to be 4000rpm and 10000rpm, respectively.

Fig. 8 shows a comparison of vibration conditions at two bearing nodes before and after balancing, and from the results, we can see that the dynamic balancing program can effectively perform dynamic balancing on an engine rotor system with a squeeze film damper under the condition that the nonlinear characteristic of the damper is weak.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.