CN114297791A - Pneumatic vibration reduction design method for turbine guider - Google Patents

Abstract

The invention relates to a design method for aerodynamic vibration reduction of a turbine guide, belonging to the technical field of engines. According to the actual flow conditions inside the turbine, the invention carries out aerodynamic vibration reduction design for the turbine guide, and forms various aerodynamic vibration reduction design schemes for the turbine guide. The results of the research on the space circumferential bending, meridional sweep, compound bending sweep and suction surface profile optimization of the turbine guide vane channel show that under the premise that the aerodynamic performance of the turbine stage does not change much, the aerodynamic circumferential direction of the turbine bucket is 1 times the frequency. The magnitude of the components is significantly reduced.

Description

A design method for aerodynamic vibration reduction of turbine guide

technical field

The invention belongs to the technical field of engines, and in particular relates to a design method for aerodynamic vibration reduction of a turbine guide.

Background technique

There are many factors that cause blade vibration in turbines, which can generally be divided into two categories: one is mechanical excitation force, and the other is aerodynamic excitation force. The mechanical load mainly produces low-frequency and large-scale stress, which causes plastic strain in the local area of the blade. When the number of cycles is small (generally below 10 ⁴ ～ 10 ⁵ ), it will lead to fatigue failure, which is called low cycle fatigue (or low cycle fatigue). cycle fatigue, plastic fatigue, strain fatigue). The load caused by the fluid-induced blade vibration is small, and the stress amplitude is also small. When cyclic loading, the blade will produce elastic strain, and the blade life is relatively long, but when the number of cycles is large (10 ⁴ ～ 10 ⁵ or more) The blade produces fatigue fracture, which is called high cycle fatigue fracture (or high cycle fatigue, stress fatigue). A large number of research materials and engineering practice show that the unsteady aerodynamic force of the fluid acting on the blade is one of the important factors to excite the blade vibration. The blade rotates in the circumferential direction, and any variation of the airflow parameters in the circumferential direction or the non-uniform distribution of space and time is an unsteady aerodynamic excitation force for the blade. The main factors affecting the unsteady aerodynamic excitation force are: structure, manufacturing or installation error, unsteady shock disturbance inside the channel, and the inherent unsteady flow of the turbomachinery, such as periodic wake sweep, gap flow, secondary flow, etc. Induce vortex motion, etc.

Therefore, it is necessary to design an aerodynamic vibration reduction design method for turbine guides for practical engineering problems such as the enhancement of unsteady effects such as the dynamic and static interference of the turbine blade, the blade vibration induced by the unsteady aerodynamic excitation force, and the high cycle fatigue.

SUMMARY OF THE INVENTION

(1) Technical problems to be solved

The technical problem to be solved by the present invention is: how to solve practical engineering problems such as the enhancement of unsteady effects such as high-pressure turbine blade discharge static interference, unsteady aerodynamic excitation force-induced blade vibration, high cycle fatigue, etc., to propose a turbine guide aerodynamic vibration reduction design method.

(2) Technical solutions

In order to solve the above-mentioned technical problems, the present invention provides a design method for aerodynamic vibration reduction of a turbine guide. The method performs aerodynamic vibration reduction design on the turbine guide, and performs circumferential bending of the guide vane channel and radial guide vane channel on the turbine guide. The three-dimensional modeling design of swept and guide vane passages combined with bending and sweeping and the optimization of the suction surface profile of the guide vane reduce the unsteady aerodynamic excitation force on the downstream turbine rotor blades.

Preferably, in this method, the guide vane channel is designed for circumferential bending: five control points are selected along the leaf height direction of the stacking line, two control points for fixing the position of the casing and the hub are fixed, and by adjusting the three control points in the middle Circumferential coordinate variation range, complete the parametric modeling design of guide vane channel circumferential bending.

Preferably, in the process of parametric modeling design for the circumferential bending of the guide vane channel, the design variables include the root angle and the bending height, the top bending angle and the bending height: only the axial coordinates of the second and fourth control points along the blade height direction The values are -0.053928 and 0.052718, respectively. The three-dimensional modeling feature of the root of the guide vane is a positive bending design, and the top is a reverse bending design.

Preferably, in this method, a radial sweep design is also performed on the guide vane channel: 5 control points are selected along the leaf height direction of the stacking line, two control points for fixing the position of the casing and the hub, and by adjusting the three control points in the middle Axial coordinate variation range, complete the parametric modeling design of guide vane channel meridian sweep.

Preferably, in the parametric modeling design process for the meridian sweep of the guide vane channel, the design variables include the sweep angle and sweep height of the root, the sweep angle and sweep height of the top: the axial coordinate values of the three control points in the middle along the blade height direction are - 0.117752, -0.140669, -0.127938, the three-dimensional modeling features of the root and top of the guide vane are all swept-back designs.

Preferably, in this method, the guide vane channel is also designed for compound bending and sweeping: 5 control points are selected along the leaf height direction of the stacking line, and two control points for fixing the position of the casing and the hub are adjusted. Circumferential and axial coordinate variation range, complete the parametric modeling design of guide vane channel sweep.

Preferably, in the parametric modeling design process for the guide vane channel sweep, the design variables include the root angle and height, the top angle and height, the root angle and height, and the root angle and height.

Preferably, in this method, the design and optimization of the profile characteristics of the suction surface of the guide vane is also carried out: 6 control points are respectively selected along the suction surface side and the pressure surface side of the airfoil section, and the two control points of the maximum thickness and the position of the tangent point of the trailing edge are fixed. By adjusting the coordinate variation range of the four control points in the middle of the airfoil section, the parametric modeling design of the profile line of the guide vane section is completed.

Preferably, in the process of parametric modeling design of the profile line of the guide vane, the design variables include the coordinate values of the six control points on the suction surface side and the pressure surface side.

The present invention also provides a turbine guide obtained by the method.

(3) Beneficial effects

According to the actual flow conditions inside the turbine, the invention carries out aerodynamic vibration reduction design for the turbine guide, and forms various aerodynamic vibration reduction design schemes for the turbine guide. The results of the research on the space circumferential bending, meridional sweep, compound bending sweep and suction surface profile optimization of the turbine guide vane channel show that under the premise that the aerodynamic performance of the turbine stage does not change much, the aerodynamic circumferential direction of the turbine bucket is 1 times the frequency. The magnitude of the components is significantly reduced. The mechanism of the aerodynamic vibration reduction design of turbine guide vanes to reduce the unsteady aerodynamic excitation force on the downstream blades can be expressed as follows: the three-dimensional channel structure of the guide vanes in the aerodynamic vibration reduction design scheme superimposes and reorganizes the unsteady flow fields of different frequencies and phases. component, which increases the valley value and decreases the peak value of the unsteady aerodynamic load of the moving blade, and at the same time distributes the peak value of the unsteady aerodynamic load of the moving blade to other phases in the circumferential direction, so as to make the amplitude of the unsteady aerodynamic excitation force on the moving blade. decrease.

Description of drawings

Figure 1 shows the three-dimensional flow field structure of the turbine director prototype scheme;

Figures 2a to 2c are the parameterized models of the turbine guide prototype scheme;

Figures 3a to 3c are parametric models of the circumferential bending design scheme of the turbine guide according to the present invention;

4a to 4c are the parametric models of the radial sweep design scheme of the turbine guide according to the present invention;

5a-5b are parametric models of the composite bending and sweeping design scheme of the turbine guide according to the present invention;

Figures 6a to 6c are the parametric models of the optimized design scheme for the profile design of the suction surface of the turbine guide according to the present invention;

Figure 7 is a comparison diagram of parameters before and after the optimized design of the suction surface profile design of the turbine guide.

Detailed ways

In order to make the purpose, content, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Aiming at the actual engineering problems such as the enhancement of unsteady effects such as the dynamic and static interference of the turbine blade, the blade vibration induced by the unsteady aerodynamic excitation force, and the high cycle fatigue, the invention proposes a three-dimensional bending and sweeping shape of the guide vane space and the suction surface shape of the downstream of the guide vane throat. Aerodynamic vibration reduction design methods such as line optimization, and propose suppression measures and design methods that are helpful for turbine engineering design at the aerodynamic design level, so as to reduce the dynamic stress of turbine blades and ensure the safety of turbine components on the premise of ensuring the expected aerodynamic performance of the turbine. The purpose of reliable work.

The invention reduces the unsteady aerodynamic excitation of the downstream turbine rotor blades by carrying out aerodynamic vibration damping design for the turbine guide, three-dimensional modeling design such as circumferential bending, radial sweep, compound bending sweep, etc. and suction surface profile optimization for the turbine guide. Vibration. For different turbines, the internal flow conditions are very different. Although the three-dimensional modeling design of the turbine guide vane channel circumferential bending, meridian sweep, compound sweep sweep and other methods, and the design and optimization of the suction surface profile feature can be used to reorganize the downstream The three-dimensional flow field structure can reduce the unsteady aerodynamic load of turbine rotor blades, but the improvement effect is closely related to the design parameters. It is worth noting that the aerodynamic vibration reduction scheme of the turbine guide changes the original flow field structure, which affects the flow field structure inside the turbine, which will definitely affect the aerodynamic performance of the turbine. In order to minimize the influence of the turbine guide vane aerodynamic vibration damping design on the turbine aerodynamic performance, and to minimize the unsteady load on the rotor blades, before the turbine guide vane aerodynamic vibration damping design, it is necessary to pass experiments, numerical calculations or theoretical The actual flow inside the turbine can be obtained through analysis and other methods, and the flow characteristics and distribution form of the wake causing the unsteady aerodynamic excitation force are known, and the key design parameters of the turbine guide vane aerodynamic vibration reduction scheme are determined based on this information.

The aerodynamic vibration damping design method of the turbine guide of the present invention is proposed on the basis of the parameterized design scheme of the prototype turbine guide. Firstly, the three-dimensional flow field of the prototype turbine director is analyzed, as shown in Figure 1, to determine the characteristics of the flow field, so as to propose a targeted aerodynamic vibration reduction scheme.

As shown in Figures 2a to 2c, the static pressure distribution characteristics of the outlet section of the turbine guide prototype scheme are that the high pressure area of the blade tip is relatively small, the low pressure area of the blade root is relatively large, and the scale of the low pressure area of the blade root varies with the blade circumference. It varies greatly depending on the swipe position. Restricted by the law of radial balance, the minimum pressure at the inlet of the bucket is located near the root of the channel corresponding to the wake of the upstream guide vane. Because the periodically rotating buckets repeatedly pass through the wake and the main flow area after the guide vanes, the high and low pressure areas of the inlet section of the buckets change periodically along the circumferential direction. This characteristic of the inlet pressure distribution of the bucket leads to an increase in the amplitude of the aerodynamic excitation force of the bucket, and weakens its structural strength and high-cycle fatigue resistance.

Based on the above analysis, one of the design methods for the aerodynamic vibration reduction of the turbine guide provided by the present invention is to design the circumferential bending of the guide vane channel. On the basis of the three-dimensional parameterization scheme of the guide vane prototype scheme, five control points are selected along the leaf height direction of the stacking line, two control points are fixed for the position of the casing and the hub, and the circumferential coordinates of the three intermediate control points are adjusted to change. range, and complete the parametric modeling design of the circumferential bending of the guide vane channel. During the parametric design of the circumferential bending of the radial stacking line of the guide vane, the design variables include the root bending angle and bending height, and the top bending angle and bending height. The axial coordinate values of the five control points of the radial stacking line of the guide vane prototype scheme are all 0. After the circumferential bending design of the guide vane, only the axial coordinate values of the second and fourth control points occur along the blade height direction. The changes are -0.053928 and 0.052718 respectively, and the axial coordinate value of the third control point is still the same as the prototype scheme. In the circumferential bending design scheme of the guide vane, the three-dimensional modeling feature of the root of the guide vane is a positive bending design, and the top is a reverse bending design.

The second method for designing the aerodynamic vibration reduction of the turbine guide provided by the present invention is to design the meridian sweep of the guide vane channel. Figures 4a to 4c show the parameterized model of the design scheme of the guide vane meridian sweep. On the basis of the parametric model of the prototype scheme of the guide vane, five control points are selected along the leaf height direction of the stacking line, two control points are fixed for the position of the casing and the hub, and the axial coordinate variation range of the three middle control points is adjusted by adjusting the range. , to complete the parametric modeling design of the guide vane channel meridian sweep. During the parametric design of the radial stacking line of the guide vane, the design variables include the root sweep angle and sweep height, and the top sweep angle and sweep height. The axial coordinate values of the five control points of the radial stacking line of the guide vane prototype scheme are all 0. After the meridian sweep design of the guide vane, the axial coordinate values of the three control points in the middle along the blade height direction are -0.117752, -0.140669, -0.127938. In the swept design scheme of the guide vane, the three-dimensional modeling features of the root and the top of the guide vane are all swept back.

The third method for designing the aerodynamic vibration damping of the turbine guide provided by the present invention is to carry out a composite bending and sweeping design for the guide vane channel. On the basis of the parametric model of the guide vane prototype scheme, five control points are selected along the leaf height direction of the stacking line, and two control points are fixed for the position of the casing and the hub. By adjusting the circumferential and axial directions of the three middle control points Coordinate change range, complete the parametric modeling design of guide vane channel sweep. In the process of compound bend-sweep parametric design of guide vane radial stacking line, the design variables include root/top bend angle and bend height, root/top sweep angle and sweep height.

The fourth method for designing the aerodynamic vibration reduction of the turbine guide provided by the present invention is to design and optimize the profile characteristics of the suction surface of the guide vane. On the basis of the parametric model of the guide vane prototype scheme, six control points are selected along the suction side and the pressure side of the blade section, and the two control points of the maximum thickness and the position of the tangent point of the trailing edge are fixed. The coordinate variation range of the four control points in the middle of the section completes the parametric modeling design of the guide vane section profile. In the process of parametric optimization design of the profile characteristics of the guide vane suction surface, the design variables include the coordinate values of the six control points on the suction surface side and the pressure surface side.

As shown in Figure 7, the design optimization of the guide vane section profile is mainly adjusted for the section profile downstream of the maximum thickness position, and mainly focuses on the section profile near the end wall. Among them, the curvature of the airfoil mid-arc from the leading edge point to the maximum thickness position increases slightly, the adjustment range of the mid-arc of the blade root section is greater than that of the blade tip, and the adjustment range of the mid-arc of the blade mid-section is relatively small. The geometric characteristics of the optimized airfoil section are as follows: the channel width of the section near the blade root increases, and the convergence gradient of the channel increases; the channel width of the section near the blade tip decreases, and the convergence gradient of the channel decreases. In addition, in order to control the high-efficiency expansion of the airflow and control the shock wave intensity of the chamfered part of the blade outlet, the root section is appropriately designed to be convex. At the same time, the throat area near the outlet of the guide vane is constrained in the optimization design process to ensure that the mass flow rate of the turbine remains unchanged.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principle of the present invention, several improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. a design method for aerodynamic vibration damping of a turbine guide, is characterized in that, the method carries out aerodynamic vibration damping design to the turbine guide, and carries out the circumferential bending of the guide vane channel, the radial sweep of the guide vane channel, the guide vane to the turbine guide. The three-dimensional modeling design of the channel compound bending and sweeping and the optimization of the suction surface profile of the guide vane reduce the unsteady aerodynamic excitation force on the downstream turbine rotor blades. 2. method as claimed in claim 1 is characterized in that, in this method, carry out circumferential bending design to guide vane channel: select 5 control points along the stacking line leaf height direction, and fix two positions of casing and hub. By adjusting the circumferential coordinate variation range of the three control points in the middle, the parametric modeling design of the circumferential bending of the guide vane channel is completed. 3. The method according to claim 2, characterized in that, in the process of parametric modeling design for the circumferential bending of the guide vane channel, the design variables include the root angle and the bending height, the top bending angle and the bending height: along the blade height direction Only the axial coordinate values of the 2nd and 4th control points are -0.053928 and 0.052718 respectively. The three-dimensional modeling features of the root of the guide vane show a positive bending design, and the top shows a reverse bending design. 4. method as claimed in claim 2 is characterized in that, in this method, also carry out meridian sweep design to guide vane channel: select 5 control points along the stacking line leaf height direction, fix the two positions of the casing and the hub. By adjusting the axial coordinate variation range of the three control points in the middle, the parametric modeling design of the guide vane channel meridian sweep is completed. 5. The method according to claim 4, characterized in that, in the process of parametric modeling design of guide vane channel meridian sweep, the design variables include root sweep angle and sweep height, top sweep angle and sweep height: along the middle of the blade height direction The axial coordinate values of the three control points are -0.117752, -0.140669, -0.127938, respectively, and the three-dimensional modeling features of the root and top of the guide vane are all swept-back designs. 6. The method according to claim 4, characterized in that, in the method, the guide vane channel is also designed for compound bending and sweeping: 5 control points are selected along the stacking line leaf height direction, two of the fixed casing and the hub position are selected. By adjusting the circumferential and axial coordinate variation ranges of the three control points in the middle, the parametric modeling design of the guide vane channel sweep is completed. 7. The method according to claim 6, characterized in that, in the process of parametric modeling design of the guide vane channel bend and sweep, the design variables include root angle and bend height, top bend angle and bend height, root sweep angle and sweep angle High, root swept angle and swept height. 8. The method according to claim 6, characterized in that, in the method, design optimization is also performed on the profile feature of the suction surface of the guide vane: 6 control points are selected respectively along the suction surface side and the pressure surface side of the airfoil section , the two control points of the maximum thickness and the position of the tangent point of the trailing edge are fixed, and the parametric modeling design of the guide vane section profile is completed by adjusting the coordinate variation range of the four control points in the middle of the airfoil section. 9 . The method according to claim 8 , wherein, in the process of parametric modeling and design of the profile of the guide vane section, the design variables include the coordinate values of six control points on the suction side and the pressure side. 10 . 10. A turbine guide obtained using the method of any one of claims 1 to 9.

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