A method for controlling wake vortex excitation of a compressor blade based on non-uniform serrations

Abstract

The application discloses a method for controlling wake excitation of a compressor blade based on non-uniform serrations, and relates to the technical field of aeronautical dynamics. CFD modeling in a three-dimensional flow field is carried out to obtain wake velocity of original stator blades in the compressor at different blade height positions; several different bird wing shapes are selected to carry out flow field analysis, and the shape of serration structure is selected; a single variable analysis method is used to set multiple groups of uniform serration arrangement schemes of the compressor stator blade tail edge with the selected serration structure, and the best serration structure and the geometric parameters of the serration structure are selected; the correlation mechanism between the wake velocity v n and the geometric parameters of the serration structure is analyzed to construct a design criterion of the non-uniform serration parameters of the stator blade tail edge; serration arrangement is performed on the tail edge at each blade height position of the compressor stator blade to obtain a non-uniform serration stator blade of the compressor, and the non-uniform serration stator blade with the maximum pressure ratio, efficiency and flow rate is obtained through iterative calculation by a Latin hypercube test method.

Description

Technical Field

[0001] This invention relates to the field of aerodynamics, specifically to a method for controlling compressor blade wake disturbance based on non-uniform sawtooth. Background Technology

[0002] Twisted blades, due to their advantages of balancing high load and high efficiency, have become one of the main directions in the design and development of advanced aero-engines. The three-dimensional twisted design, coupled with super-maneuverability, causes them to exhibit more complex excitation forms in the mixing and conversion of subsonic and supersonic airflows, which restricts the improvement of aero-engine performance and service safety.

[0003] The gas flow generated by the blades during operation creates a wake, a phenomenon caused by the velocity and pressure differences generated as the airflow passes through the blade passage. However, the presence of the wake can disturb downstream blades or other components, leading to problems such as decreased aerodynamic performance, flow instability, and vibration. This flow disturbance generated by the blades is called unsteady wake excitation of compressor blades. To reduce blade wake excitation, a series of methods and technologies have been proposed. The most common method is to optimize the blade geometry and spacing. By adjusting parameters such as blade curvature and torsion angle, the intensity and non-uniformity of the wake can be reduced. However, the design requirements of high pressure ratio and high efficiency in compressors strictly limit the aerodynamic design of the blades, making it difficult to achieve ideal wake disturbance control. In addition, devices such as wake traps, disturbance generators, and vortex generators are designed to intervene in the shape and motion characteristics of the wake at the blade passage exit. Wake traps can guide, deflect, or disperse the wake to reduce its disturbance impact on downstream blades. Disturbance generators improve wake characteristics through additional turbulent energy or vortex structures. Vortex generators are used to enhance the mixing of the wake with the mainstream, promoting rapid diffusion and dissipation of the wake. However, such powerful or complex devices may increase the load on the compressor and reduce its efficiency. Summary of the Invention

[0004] The problem this invention aims to solve is to address the shortcomings of the prior art by providing a compressor blade wake disturbance control method based on non-uniform sawtooth, thereby solving the problem that wake disturbance control is difficult to achieve the ideal target and will increase the compressor load and reduce the compressor efficiency.

[0005] To achieve the above-mentioned objectives of this invention, this invention provides a method for controlling compressor blade wake disturbance based on non-uniform sawtooth blades, the method comprising the following steps:

[0006] Step 1 involves performing CFD modeling of the three-dimensional flow field based on the compressor's structural characteristics and boundary conditions. The wake velocity ν of the original stator blades at different blade heights is then obtained through simulation of the three-dimensional flow field. n The boundary conditions include inlet conditions, outlet conditions, blade surface conditions, and surrounding environmental conditions.

[0007] Step 2: Select several different bird feather shapes to conduct flow field analysis. Based on the distribution of their wakes, select the shape with the smallest wake velocity loss as the shape of the sawtooth structure, and apply the sawtooth structure of this shape to the trailing edge of the compressor stator blade.

[0008] Step 3: Based on the geometric parameters of the serrated structure, use univariate analysis to set up multiple uniform serrated arrangement schemes at the trailing edge of the compressor stator blades with the selected serrated structure. Analyze the influence of the arrangement scheme on the wake of the compressor stator blades, and select the serrated structure with the best aerodynamics at different blade height positions and the geometric parameters of the serrated structure. The geometric parameters include serrated height, serrated width, and blade chord length.

[0009] The method of using univariate analysis to set up multiple application schemes for uniform serrated arrangement at the trailing edge of the compressor stator blades with serrated structure includes:

[0010] a. The height and width of the serrations are enlarged proportionally;

[0011] b. Keep the sawtooth width constant and change the sawtooth height;

[0012] c. Keep the sawtooth height constant, and change the sawtooth width.

[0013] Step 4 is based on the wake velocity ν of the original stator blade at each blade height position. n The optimal aerodynamic serrated structure and its geometric parameters at different blade height positions were selected, and the wake velocity v was analyzed. n The correlation mechanism with the geometric parameters of the serrated structure is used to construct the design criteria for the non-uniform serration parameters of the stator blade trailing edge;

[0014] The design criteria for the non-uniform serration parameters of the stator blade trailing edge are as follows:

[0015]

[0016] h n =αL n (2)

[0017] λ n =βL n (3)

[0018] In the formula, L nThe serration parameters at different blade height positions; a i b is the fitting coefficient, related to the stator blade wake velocity distribution; α and β are the tooth height coefficient and tooth width coefficient, respectively, related to the serration shape; m is the blade shape coefficient, related to the geometric twist of the blade trailing edge. When m = 1, the stator blade is a straight blade; when m = 2, the stator blade is a twisted blade; when m > 2, the twist of the stator blade gradually increases with the increase of m value; n is the number of sections along the blade height direction; v n h represents the wake velocity at different blade height positions. n , λ n These represent the serration height and serration width at different leaf height positions.

[0019] Step 5: Based on the design criteria of non-uniform serration parameters of stator blade trailing edge, serrations are arranged at the trailing edge of each blade height position of the compressor stator blade to obtain non-uniform serrated stator blades of the compressor. The non-uniform serrated stator blades with the largest pressure ratio, efficiency and flow rate are obtained by iterative calculation using the Latin hypercube test method, so as to achieve the optimized design of compressor stator blade vibration reduction and noise reduction.

[0020] The Latin hypercube test method is based on the wake velocity v at different leaf height positions. n With the goal of expanding the compressor's operating margin, and considering the cascade pressure ratio and aerodynamic efficiency, non-uniform serrated stator blades with the highest pressure ratio, efficiency, and flow rate are obtained.

[0021] Compared with the prior art, the technical solution adopted in this invention has the following technical effects:

[0022] This invention provides a compressor blade wake disturbance control method based on non-uniform sawtooth blades. The method constructs a correlation function and criterion between the blade wake velocity and the geometric parameters of the sawtooth structure, realizing the design and optimization of the non-uniform sawtooth parameters. By introducing sawtooth structures of different sizes at the blade trailing edge, the mixing of the wake and the mainstream is promoted, thereby accelerating the diffusion and dissipation of the wake and reducing the disturbance of the wake to the downstream blades. At the same time, the application of non-uniform sawtooth blades can also effectively improve the compressor efficiency and stable operating range, and achieve blade weight reduction. Attached Figure Description

[0023] Figure 1 This is a flowchart of a compressor blade wake disturbance control method based on non-uniform sawtooth pattern in an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the non-uniform serrated structure at the trailing edge of the stator blade in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of a compressor stator blade stage with non-uniform trailing edge serrations in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the stator blade stage of an axial compressor with non-uniform trailing edge serrations in an embodiment of the present invention.

[0027] Figure 5 The compressor operating characteristic curves for the original blade, the blade with uniform trailing edge serrations, and the blade with non-uniform serrations in the embodiments of the present invention are shown.

[0028] Among them, (a) is the flow-pressure ratio characteristic curve; (b) is the flow-efficiency characteristic curve. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0030] This embodiment provides a compressor blade wake disturbance control method based on non-uniform sawtooth blades, such as... Figure 1 As shown, it includes the following steps:

[0031] Step 1 involves performing CFD modeling of the three-dimensional flow field based on the compressor's structural characteristics and boundary conditions. The wake velocity ν of the original stator blades at different blade heights is then obtained through simulation of the three-dimensional flow field. n ;

[0032] In this embodiment, firstly, based on the actual blade geometry in the compressor, the shape of the blade, the blade clearance, and the details of the surrounding flow field are accurately captured, and a three-dimensional geometric model of the blade is created using computer-aided design software. Then, a mesh is generated, dividing the three-dimensional geometric model of the blade into discrete small units. The quality of the mesh and an appropriate mesh density are crucial for accurately simulating the flow behavior. After the mesh is established, the boundary conditions of the flow field are set. The applied boundary conditions depend on the actual operating conditions and maneuverability of the compressor. These include specifying inlet conditions (velocity, pressure, temperature, etc.), outlet conditions (static pressure or total pressure), blade surface conditions (wall friction, heat transfer, etc.), and surrounding environmental conditions (pressure, temperature, turbulence intensity, etc.).

[0033] The appropriate CFD solver should be selected based on the simulation requirements and the availability of computing resources. The choice of solver is influenced by the flow type (compressible, incompressible, etc.) and the turbulence model. When setting solver parameters, factors such as numerical stability, convergence, and computational efficiency need to be considered. In boundary layer modeling and turbulence simulation, the flow on compressor blades usually involves boundary layer and turbulence phenomena. Therefore, boundary layer modeling and turbulence simulation are important steps in the CFD modeling process. Appropriate turbulence models and boundary layer treatment methods, such as RANS, LES, or DNS models, need to be selected. After running the CFD simulation, results on compressor performance and flow characteristics are obtained. Then, the simulation output data is further processed, including flow field visualization, data extraction, and performance evaluation, to obtain the CFD-calculated output data.

[0034] Post-processing analysis was performed on the CFD output data. Velocity contour maps were plotted at 10%, 30%, 50%, 70%, and 90% of the original stator blade height. These maps visually demonstrate the velocity distribution at different blade heights. Simultaneously, a monitoring line was created at the exit point of the original stator blade, and sampling points were set along this line to extract the wake velocity v of the original stator blade at these five blade height positions. n .

[0035] Step 2: Select several different bird feather shapes to conduct flow field analysis. Based on the distribution of their wakes, select the shape with the smallest wake velocity loss as the shape of the sawtooth structure, and apply the sawtooth structure of this shape to the trailing edge of the compressor stator blade.

[0036] In this embodiment, flow field analysis is performed on the conventional bird wing shapes in a two-dimensional flow field. The conventional bird wing shapes include square, circular, triangular and trapezoidal. By comparing the aerodynamic performance of these shapes, it is found that the velocity change in the wake region of the triangle is the smallest and the distribution is the most uniform, which effectively improves the wake characteristics. Therefore, the triangle is selected as the shape of the sawtooth structure, and the sawtooth structure of this shape is applied to the trailing edge of the compressor blade.

[0037] Step 3: Based on the geometric parameters of the serrated structure, use univariate analysis to set up multiple uniform serrated arrangement schemes at the trailing edge of the compressor stator blades with the selected serrated structure. Analyze the influence of the arrangement scheme on the wake of the compressor stator blades, and select the serrated structure with the best aerodynamics at different blade height positions and the geometric parameters of the serrated structure. The geometric parameters include serrated height, serrated width, and blade chord length.

[0038] In this embodiment, based on the geometric parameters of the triangular sawtooth structure, a univariate analysis method is employed. For example, the sawtooth height is kept constant while the sawtooth width is varied; the sawtooth width is kept constant while the sawtooth height is varied; or the equilateral triangular characteristic of the sawtooth is maintained, i.e., both the sawtooth height and width are changed simultaneously, but their ratio remains constant. Through these methods, multiple uniform sawtooth arrangement schemes are obtained. These schemes are then applied to the compressor and CFD numerical calculations are performed. By comparing the calculation results, the sawtooth structure and its parameters that minimize wake disturbance at different blade height positions are selected. The scheme where both sawtooth width and height are changed simultaneously but the width-to-height ratio remains constant (i.e., equilateral triangular sawtooth) performs particularly well in reducing wake disturbance, thereby effectively improving the aerodynamic performance of the compressor stator blades at this position.

[0039] Step 4 is based on the wake velocity v of the original stator blade at each blade height position. n The optimal aerodynamic serrated structure and its geometric parameters at different blade height positions were selected, and the wake velocity v was analyzed. n The correlation mechanism with the geometric parameters of the serrated structure is used to construct the design criteria for the non-uniform serration parameters of the stator blade trailing edge;

[0040] Each blade of the original stator blade has a wake velocity v at its highest position. n Simultaneously, based on the optimal aerodynamic serrated structure and its geometric parameters at different blade height positions, the corresponding serrated structure is applied to the corresponding blade height positions, and the wake velocity v at each blade height position is calculated. n and the geometric parameters of the sawtooth structure (sawtooth height h) n serration width λ n Correlation was performed to establish the non-uniform serration parameter L at the trailing edge of the stator blade. n The design principles are as follows:

[0041]

[0042] h n =αL n (2)

[0043] λ n =βL n (3)

[0044] In formula (1), L n The serration parameters at different blade height positions; a ib is the fitting coefficient, related to the stator blade wake velocity distribution; α and β are the tooth height coefficient and tooth width coefficient, respectively, related to the serration shape; m is the blade shape coefficient, related to the geometric twist of the blade trailing edge. When m = 1, the stator blade is a straight blade; when m = 2, the stator blade is a twisted blade; when m > 2, the twist of the stator blade gradually increases with the increase of m value; n is the number of sections along the blade height direction; ν n h represents the wake velocity at different blade height positions. n , λ n The serration height and serration width at different blade height positions are given. Based on the optimal aerodynamic performance of the serration structure and its geometric parameters, and by fitting the wake velocity of the original stator blade at a specified blade height position, a can be obtained. i The value of b.

[0045] In this embodiment, the serration parameter L of the stylus blade at different blade height positions is... n and the original stator blade wake velocity ν n As shown in Table 1;

[0046] Table 1. Initial stator blade wake velocity ν n With sawtooth parameter L n

[0047]

[0048] Based on the above parameters and in conjunction with the design criteria, we can obtain:

[0049]

[0050] h n =L n (5)

[0051] λ n =L n (6)

[0052] Among them, the coefficients a2=0.0003, a1=-0.0113, b=4.5701; based on the equilateral triangular sawtooth shape, α and β are both 1.

[0053] Step 5: Based on the design criteria of non-uniform serration parameters of stator blade trailing edge, serrations are arranged at the trailing edge of each blade height position of the compressor stator blade to obtain non-uniform serrated stator blades of the compressor. The non-uniform serrated stator blades with the largest pressure ratio, efficiency and flow rate are obtained by iterative calculation using the Latin hypercube test method, so as to achieve the optimized design of compressor stator blade vibration reduction and noise reduction.

[0054] In this embodiment, the non-uniform serration parameter L of the stator blade trailing edge is used. nThe design principles were followed to arrange serrated edges at the trailing edges of each compressor stator blade at its highest position, resulting in a non-uniform serrated blade. A Latin hypercube experimental design was employed to optimize the non-uniform serrated blade, using the blade's leading and trailing edge installation angles as design variables. The optimization range for the blade installation angle was selected, taking into full account the rationality of the design space and computational efficiency. To ensure the capture of trends within the design space, a sufficient number of optimization samples was ensured. The optimization objectives were the compressor blade's pressure ratio, efficiency, and flow rate. In each iteration, CFD calculations were performed based on the current optimization variable settings to obtain the compressor's pressure ratio, efficiency, and flow rate values ​​for each sample point's parameter combination. After each iteration, the performance indicators of each sample point were evaluated, ultimately yielding a non-uniform serrated stator blade with optimal pressure ratio, efficiency, and flow rate within the design space. Figure 2 As shown. This improves the aerodynamic performance of the compressor blades and reduces disturbance to downstream blades, thereby achieving optimized design for vibration reduction and noise reduction of the compressor blades.

[0055] Will Figure 2 The non-uniform serrated stator blade shown is used in a compressor. In terms of overall layout, the serrations at the trailing edge of the stator blade are arranged in ascending order of size, extending from the blade tip to the blade root. Figure 3 The invention showcases a compressor stator blade stage with non-uniform trailing edge serrations and an axial compressor stator blade stage with non-uniform trailing edge serrations, a configuration that guides a superior flow pattern during air compression. Figure 4 This paper demonstrates an axial-flow compressor stage composed of rotor blades and non-uniform trailing-edge serrated stator blades, which serves to achieve efficient gas compression and kinetic energy transfer. By applying the non-uniform serrated stator blades to the compressor, the flow-pressure ratio and flow-efficiency characteristic curves at 100% speed are calculated, as shown below. Figure 5 As shown in the diagram, the calculated data and characteristic graphs clearly show that at 100% speed, the serrated trailing-edge stator blades affect the overall aerodynamic performance of the compressor. Compared to the compressor under the action of the original blades, the serrated trailing-edge stator blades improve the compressor efficiency to a certain extent, and the flow rate at the choke point tends to shift to the right, thus enhancing the flow capacity. Furthermore, the pressure ratio-flow characteristic curve shows that under high flow conditions, the pressure ratio of the trailing-edge serrated stator blades is improved, while the pressure ratio does not change significantly under the design point condition. It is worth noting that the non-uniform trailing-edge serrated compressor stator blades perform particularly well. This design not only maintains the compressor's pressure ratio stability but also significantly improves the compressor's efficiency and flow capacity, while also expanding its stable operating range. This innovative design is of great significance for optimizing compressor performance, improving its efficiency, and adapting to a wider range of operating conditions.

Claims

1. A method for controlling compressor blade wake disturbance based on non-uniform sawtooth blades, characterized in that, The steps include the following: Step 1 involves CFD modeling of the three-dimensional flow field based on the compressor's structural characteristics and boundary conditions. The wake velocity v of the original stator blades at different blade heights is then obtained through simulation of the three-dimensional flow field. n ; Step 2: Select several different bird wing shapes to conduct flow field analysis. Based on the distribution of their wakes, select the shape with the smallest wake velocity loss as the shape of the serrated structure, and apply the serrated structure of this shape to the trailing edge of the compressor stator blade. Step 3: Based on the geometric parameters of the sawtooth structure, use the univariate analysis method to set up multiple uniform sawtooth arrangement schemes at the trailing edge of the compressor stator blades with the selected sawtooth structure, analyze the influence of the arrangement scheme on the wake of the compressor stator blades, and select the sawtooth structure with the best aerodynamics at different blade height positions and the geometric parameters of the sawtooth structure. Step 4 is based on the wake velocity v of the original stator blade at each blade height position. n The optimal aerodynamic serrated structure and its geometric parameters at different blade height positions were selected, and the wake velocity v was analyzed. n The correlation mechanism with the geometric parameters of the serrated structure is used to construct the design criteria for the non-uniform serration parameters of the stator blade trailing edge; Step 5: Based on the design criteria of non-uniform serration parameters of stator blade trailing edge, serrations are arranged at the trailing edge of each blade height position of the compressor stator blade to obtain non-uniform serrated stator blades of the compressor. The non-uniform serrated stator blades with the largest pressure ratio, efficiency and flow rate are obtained by iterative calculation using the Latin hypercube test method, so as to achieve the optimized design of compressor stator blade vibration reduction and noise reduction.

2. The compressor blade wake disturbance control method based on non-uniform sawtooth as described in claim 1, characterized in that, The geometric parameters in step 3 include sawtooth height, sawtooth width, and blade chord length.

3. The compressor blade wake disturbance control method based on non-uniform sawtooth as described in claim 1, characterized in that, The design criteria for the non-uniform serration parameters of the stator blade trailing edge in step 4 are as follows: h n =αL n (2) l n =βL n (3) In the formula, L n The serration parameters are given at different blade height positions; a i b is the fitting coefficient, related to the stator blade wake velocity distribution; α and β are the tooth height coefficient and tooth width coefficient, respectively, related to the serration shape; m is the blade shape coefficient, related to the geometric twist of the blade trailing edge. When m = 1, the stator blade is a straight blade; when m = 2, the stator blade is a twisted blade; when m > 2, the twist of the stator blade gradually increases with the increase of m value; n is the number of sections along the blade height direction; v n h represents the wake velocity at different blade height positions. n , λ n These represent the serration height and serration width at different leaf height positions.

4. The compressor blade wake disturbance control method based on non-uniform sawtooth as described in claim 1, characterized in that, In step 3, the univariate analysis method is used to set multiple sets of uniform serrated arrangement schemes at the trailing edge of the compressor stator blades with the selected serrated structure, including: a. The height and width of the serrations are enlarged proportionally; b. Keep the sawtooth width constant and change the sawtooth height; c. Keep the sawtooth height constant, and change the sawtooth width.

5. The compressor blade wake disturbance control method based on non-uniform sawtooth as described in claim 1, characterized in that, The Latin hypercube test method described in step 5 is based on the wake velocity v at different leaf height positions. n With the goal of expanding the compressor's operating margin, and considering the cascade pressure ratio and aerodynamic efficiency, non-uniform serrated stator blades with the highest pressure ratio, efficiency, and flow rate are obtained.

6. The compressor blade wake disturbance control method based on non-uniform sawtooth as described in claim 1, characterized in that, The boundary conditions in step 1 include inlet conditions, outlet conditions, blade surface conditions, and surrounding environmental conditions.

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