Variable cycle engine complete machine vibration energy transfer characteristic analysis method based on power flow method

Abstract

The invention relates to the technical field of aero-engine vibration analysis, and discloses a variable cycle engine complete machine vibration energy transfer characteristic analysis method based on a power flow method, and the method specifically comprises the following steps: 1, calculating an instantaneous power flow and a steady state power flow of a structure through a vibration power flow calculation method; 2, calculating the power flow of the structure through comsol software, and achieving the visualization of power flow energy transmission; and step 3, calculating the transmissibility of the power flow and quantifying the transmission of the vibration energy, specifically, assuming that the instantaneous load borne by the structure at the node i is Fi (t) at a certain moment and the response speed caused at the node i is vi (t), and calculating the transmissibility of the power flow by combining a power flow visualization method and a steady-state power flow calculation method. The vibration energy flow can be visualized, the size of the transmitted energy is quantified, and the method has important theoretical significance and practical value for optimizing the vibration characteristics of a new generation of aero-engines and improving the stability and reliability of the engines.

Description

Technical Field

[0001] The invention relates to the technical field of aviation engine vibration analysis, and in particular to a method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method. Background Art

[0002] There are two main methods for studying the vibration transfer characteristics of structures: the traditional vibration path analysis method TPA based on experiments and the power flow method based on theoretical analysis. The traditional vibration path analysis method TPA is to obtain the transfer function and working condition data through actual tests, and then conduct TPA analysis. It is widely used in aircraft, automobiles and other vibroacoustic structures. However, for aircraft engines, the whole-machine experiment of aircraft engines is in a high-temperature and high-pressure environment, and engineering experiments and data collection are extremely difficult. It will cost a lot to obtain the excitation source load and transfer path function through the whole-machine experiment. Therefore, the TPA method based on experimental data is not suitable for the analysis of the vibration transfer characteristics of the whole aircraft engine.

[0003] At present, the quantitative evaluation of the vibration of the research object is mostly based on single structural response parameters such as vibration acceleration, displacement and stress. Structural vibration control only reduces the value of a single response parameter. In fact, vibration energy covers force, velocity and the phase information between them, and continues to propagate to the surroundings. Controlling force or velocity alone while ignoring the phase relationship between them cannot guarantee the effectiveness of vibration control, nor can it accurately describe the vibration energy transfer characteristics composed of force and motion.

[0004] Therefore, we propose a method to analyze the vibration energy transfer characteristics of a variable cycle engine based on the power flow method. Summary of the invention

[0005] The present invention mainly solves the technical problems existing in the above-mentioned prior art and provides a method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme, a method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method, which specifically includes the following steps:

[0007] Step 1: Use the vibration power flow calculation method to calculate the instantaneous power flow and steady-state power flow of the structure;

[0008] Step 2: Calculate the power flow of the structure through Comsol software to visualize the power flow energy transfer;

[0009] Step 3: Calculate the power flow transfer rate to quantify the transfer of vibration energy.

[0010] As a preferred method, the specific method of the first step is: Assume that at a certain moment, the instantaneous load borne by the structure at node i is F i (t), the response speed caused by this is v i (t), then the instantaneous power flow of the structure at point i can be expressed as:

[0011] p i =F i (t)·v i (t)

[0012] When the structure is subjected to simple harmonic loads, the response of the structure also has the form of simple harmonic motion. The short instantaneous power flow cannot reflect the overall energy flow of the structure. At this time, the average power flow needs to be calculated. The average power flow of node i is defined as:

[0013]

[0014] in, is the period of steady-state vibration, θ is F i With v i The phase difference, superscript * indicates complex conjugate, Re indicates taking the real part of the complex number, variable cycle engines are often modeled using solid units, which contain 8 nodes, each of which has translational degrees of freedom in the x, y, and z directions, marked as 1, 2, and 3. Each unit surface can bear normal stress and corresponding shear stress, and the power flow per unit area of ​​the solid unit can be expressed as:

[0015] p x =σ 11 v1+σ 12 v2+σ 13 v3

[0016] p y =σ 21 v1+σ 22 v2+σ 23 v3

[0017] p z =σ 31 v1+σ 32 v2+σ 33 v3

[0018] Where v represents the velocity in all directions, σ is the element stress component, and p x 、p y 、p z can be combined into a vector field p.

[0019] As a preferred method, the specific method of the second step is: vibration energy visualization can intuitively reflect the energy source, transfer path and energy convergence point, providing a basis for energy transfer analysis. The tangent direction of any point on the curve is consistent with the vector direction of the point, so the streamline expression of the vibration power flow is:

[0020] dr×p(r,t)=0

[0021] Among them, r represents the spatial position of any point of power flow, p(r, t) is the vibration power flow vector of the point at time t, which can also be expressed as:

[0022]

[0023] Preferably, the specific method of the third step is: simplify the engine into a two-degree-of-freedom system, analyze the transmission characteristics of vibration energy between the rotor and the stator, simplify the variable cycle engine rotor structure to mass m1, simplify the stator structure to mass m2, assume that the support of the rotor and the stator is simplified to k1, c1, the support of the stator structure and the aircraft installation node is k2, c2, and the simple harmonic excitation force caused by the mass imbalance borne by the rotor is f1(t)=m e ew 2 sin(wt), the rotor output power can be expressed as:

[0024]

[0025] The power received by the stator casing is:

[0026]

[0027] Define the average power transfer rate T p for:

[0028]

[0029] Beneficial Effects

[0030] The present invention provides a method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method. It has the following beneficial effects:

[0031] 1. This is a variable cycle engine vibration energy transfer characteristics analysis method based on the power flow method. By combining the power flow visualization method and the steady-state power flow calculation method, this method can visualize the vibration energy flow and quantify the amount of transferred energy. It has important theoretical significance and practical value for optimizing the vibration characteristics of the new generation of aircraft engines and improving engine stability and reliability.

[0032] 2. This method for analyzing the vibration energy transfer characteristics of a variable cycle engine as a whole based on the power flow method provides a method for analyzing the vibration energy transfer characteristics of a variable cycle engine as a whole, thereby recognizing the vibration problem of the variable cycle engine as a whole structure from a more essential vibration energy perspective, and providing strong theoretical support and engineering guidance for the vibration suppression strategy of the entire aircraft engine from the perspective of vibration energy transfer control.

[0033] 3. This variable cycle engine whole machine vibration energy transfer characteristics analysis method based on the power flow method can more accurately predict and control the vibration characteristics of the engine under different working conditions, and provide a new analysis method for engine maintenance and fault diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the rotor power flow streamline diagram of the present invention;

[0035] Figure 2 It is the power flow streamline diagram of the casing surface of the present invention. DETAILED DESCRIPTION

[0036] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings described below are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0037] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] In the description of the embodiments of the present invention, it should be noted that the terms "center", "upper", "lower", "inner", "outer", "side", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invented product is usually placed when in use, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0040] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Embodiment 1: A method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method, such as Figure 1-Figure 2 As shown, it specifically includes the following steps: Step 1: Use the vibration power flow calculation method to calculate the instantaneous power flow and steady-state power flow of the structure; Step 2: Calculate the power flow of the structure through the comsol software to realize the visualization of power flow energy transfer; Step 3: Calculate the power flow transfer rate to quantify the transmission of vibration energy. The specific method of the first step is: Assume that at a certain moment, the instantaneous load on the structure at node i is F i (t), the response speed caused by this is v i (t), then the instantaneous power flow of the structure at point i can be expressed as:

[0043] p i =F i (t)·v i (t)

[0044] When the structure is subjected to simple harmonic loads, the response of the structure also has the form of simple harmonic motion. The short instantaneous power flow cannot reflect the overall energy flow of the structure. At this time, the average power flow needs to be calculated. The average power flow of node i is defined as:

[0045]

[0046] in, is the period of steady-state vibration, θ is F i With v i The phase difference, superscript * indicates complex conjugate, Re indicates taking the real part of the complex number, variable cycle engines are often modeled using solid units, which contain 8 nodes, each of which has translational degrees of freedom in the x, y, and z directions, marked as 1, 2, and 3. Each unit surface can bear normal stress and corresponding shear stress, and the power flow per unit area of ​​the solid unit can be expressed as:

[0047] p x =σ 11 v1+σ 12 v2+σ 13 v3

[0048] p y =σ 21 v1+σ 22 v2+σ 23 v3

[0049] p z =σ 31 v1+σ 32 v2+σ 33 v3

[0050] Where v represents the velocity in all directions, σ is the element stress component, and p x 、p y 、p z can be combined into a vector field p. The specific method of the second step is: vibration energy visualization, which can intuitively reflect the energy source, transfer path and energy convergence point, providing a basis for energy transfer analysis. The tangent direction of any point on the curve is consistent with the vector direction of the point, so the streamline expression of the vibration power flow is:

[0051] dr×p(r,t)=0

[0052] Among them, r represents the spatial position of any point of power flow, p(r, t) is the vibration power flow vector of the point at time t, which can also be expressed as:

[0053]

[0054] The specific method of the third step is: simplify the engine into a two-degree-of-freedom system, analyze the transmission characteristics of vibration energy between the rotor and the stator, simplify the variable cycle engine rotor structure to mass m1, and simplify the stator structure to mass m2. Suppose the support of the rotor and the stator is simplified to k1 and c1, and the support of the stator structure and the aircraft installation node is k2 and c2. The simple harmonic excitation force caused by the mass imbalance of the rotor is f 1(t)=m e ew 2 sin(wt), the rotor output power can be expressed as:

[0055]

[0056] The power received by the stator casing is:

[0057]

[0058] Define the average power transfer rate T p for:

[0059]

[0060] Embodiment 2: Based on Embodiment 1, Figure 1-Figure 2As shown in the figure, the specific implementation steps are as follows: Step 1: Establish a finite element model of the entire engine, set the rotor speed range, and calculate the critical speed of the engine system based on finite element calculation. Because the engine system vibrates greatly near the critical speed of the rotor, selecting the speed near the critical speed for vibration energy transfer analysis is of great help to the vibration suppression of the entire aircraft engine. Using transient analysis, calculate the speed and stress of the entire machine within a unit period, and multiply the two to get the size of the transient power flow of the entire machine. Using power flow visualization technology, the energy source, transfer path and energy convergence point of the transient power flow of the entire machine can be obtained; Step 2: Steady-state power flow is the average result of transient power flow within a unit period, reflecting the average transfer characteristics of transient vibration energy within a period. Compared with transient power flow, although steady-state power flow cannot see the process of vibration energy transfer and transformation over time, it can quantify the vibration level of the structure at a specific frequency. Therefore, it is necessary to calculate the steady-state average power flow. By integrating the transient power flow in unit time, the size of the steady-state power flow can be obtained. Similarly, by integrating the transient power flow of each unit of the engine in a unit period, a steady-state power flow streamline diagram can be obtained, which can reflect the total flow of vibration energy over a period of time; Step 3: By calculating the power flow transfer rate at different fulcrums at different speeds, the size of vibration energy transfer is quantitatively characterized, so that the size of energy transferred by each transfer path can be quantitatively described, which can provide an indicator reference for structural optimization design. The vibration energy transfer of the aircraft engine rotor is mainly transmitted to the stator casing through the support. For this purpose, the rotor fulcrum corresponding to the support is selected as the source surface, and the surface where the stator casing contacts the support is selected as the target surface. The power flow transfer rate from the source surface to the target surface is calculated. When the speed of the aircraft engine is r, the input energy of the source surface and the energy received by the target surface can be expressed as:

[0061]

[0062] Among them, p i , p j They represent the power flow distribution of the energy input source surface and the target surface respectively. The absolute value of the power flow is first integrated over the surface and then further integrated over the unit period, where T is the vibration period.

[0063] Working principle of the present invention: During the operation of the engine, the transmission and distribution of vibration energy are key factors affecting its performance. The present invention analyzes the whole-machine vibration energy transfer characteristics of the variable cycle engine through the power flow method, which can reveal the flow path and distribution law of energy inside the engine. Specifically, by calculating the instantaneous power flow and the steady-state power flow, the energy flow of the structure under different working conditions can be obtained. By using the COMSO software for simulation calculation, the transmission path and energy convergence point of the vibration energy can be intuitively displayed, thereby providing a scientific basis for the structural optimization and vibration control of the engine. In addition, by defining the average power transfer rate, the transmission efficiency of the vibration energy between the rotor and the stator can be quantified, providing a new perspective for the performance evaluation and fault diagnosis of the engine. In summary, the present invention can not only improve the stability and reliability of the engine, but also provide theoretical support for the vibration suppression strategy of the aircraft engine, and has important practical value and theoretical significance.

[0064] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on a power flow method, characterized in that: The specific steps include: Step 1: Use the vibration power flow calculation method to calculate the instantaneous power flow and steady-state power flow of the structure; Step 2: Calculate the power flow of the structure through the Comsol software to visualize the power flow energy transfer; Step 3: Calculate the power flow transfer rate to quantify the transfer of vibration energy.

2. The method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on the power flow method according to claim 1 is characterized in that: The specific method of the first step is: Assume that a certain time is t, and the instantaneous load on the structure at node i is F i (t), the response speed caused by this is v i (t), then the instantaneous power flow of the structure at point i can be expressed as: p i =F i (t)·v i (t) When the structure is subjected to simple harmonic loads, the response of the structure also has the form of simple harmonic motion. The short instantaneous power flow cannot reflect the overall energy flow of the structure. At this time, the average power flow needs to be calculated. The average power flow of node i is defined as: in, is the period of steady-state vibration, θ is F i With v i The phase difference, superscript * indicates complex conjugate, Re indicates taking the real part of the complex number, variable cycle engines are often modeled using solid units, which contain 8 nodes, each of which has translational degrees of freedom in the x, y, and z directions, marked as 1, 2, and 3. Each unit surface can bear normal stress and corresponding shear stress, and the power flow per unit area of ​​the solid unit can be expressed as: p x =s 11 v1+s 12 v2+s 13 v3 p y =s 21 v1+s 22 v2+s 23 v3 p z =s 31 v1+s 32 v2+s 33 v3 Where v represents the velocity in all directions, σ is the element stress component, and p x 、p y 、p z can be combined into a vector field p.

3. The method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on the power flow method according to claim 1 is characterized in that: The specific method of the second step is: vibration energy visualization can intuitively reflect the energy source, transfer path and energy convergence point, providing a basis for energy transfer analysis. The tangent direction of any point on the curve is consistent with the vector direction of the point, so the streamline expression of the vibration power flow is: dr×p(r, t)=0 Among them, r represents the spatial position of any point of power flow, p(r, t) is the vibration power flow vector of the point at time t, which can also be expressed as:

4. The method for analyzing the vibration energy transfer characteristics of a variable cycle engine based on the power flow method according to claim 1 is characterized in that: The specific method of the third step is: simplify the engine into a two-degree-of-freedom system, analyze the transmission characteristics of vibration energy between the rotor and the stator, simplify the variable cycle engine rotor structure to mass m1, simplify the stator structure to mass m2, assume that the support of the rotor and the stator is simplified to k1, c1, the support of the stator structure and the aircraft installation node is k2, c2, and the simple harmonic excitation force caused by the mass imbalance of the rotor is f1(t)=m e ew 2 sin(wt), the rotor output power can be expressed as: The power received by the stator casing is: Define the average power transfer rate T p for:

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