A method for predicting compressor corner separation / stall with dihedral angle variation
By comparing the MDJ diffusion factor of the compressor blade with the critical MDJ diffusion factor, the problem of angle separation and stall caused by dihedral angle changes in the prior art is solved, and high-precision prediction of the flow state of the compressor three-dimensional blade is achieved, which improves the design accuracy.
Patent Information
- Application Number
- CN202411116005.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-14
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2044-08-14
AI Technical Summary
The prior art cannot accurately predict the separation and stalling of the angle region caused by dihedral angle changes in three-dimensional blades of modern compressors, especially the method of discriminating end bend and composite bend swept blades, and the process changes along dihedral angles cannot be effectively considered.
By comparing the MDJ diffusion factor of the compressor blade with the critical MDJ diffusion factor, combining the physical model of the variable dihedral angle expansion pipeline and the inverse pressure gradient environment, quantization parameters are established to distinguish the angle separation or stalling, and flow state prediction is used using the MDJ diffusion factor expression.
The prediction accuracy of the flow phenomenon of the three-dimensional blades in the compressor is improved, the accuracy of the plane cage flow state is ensured, and the prediction ability of modern compressor blade design is improved.
Smart Images
Figure CN119026508B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a compressor angular zone separation / stall prediction method targeting dihedral angle changes, and belongs to the technical field of compressor blade design and manufacturing. Background Art
[0002] Corner-area stall can seriously affect the aerodynamic performance of compressor blades. Therefore, in the design and operation of compressor blades, it is necessary to consider and strive to avoid the occurrence of this flow phenomenon. The use of compressor corner-area separation / stall prediction technology can quickly determine whether the corner area is stalled or not, which is of great significance to the design, application and development of compressor blades. At present, the design of advanced compressor blades has entered the full three-dimensional modeling stage. Analysis of the existing compressor corner-area separation / stall prediction methods shows that the reason for the failure of the judgment of end-bend and compound-bend blades is that, in addition to ignoring the dihedral angle factor in the corner area, the change of dihedral angle along the process is an important factor that has not been considered so far. Summary of the Invention
[0003] The purpose of the present invention is to solve the technical problem that the existing technology cannot accurately predict the separation / stall of the angular area of modern compressor three-dimensional blades with end bend and compound bend sweep characteristics. A method for predicting the separation / stall of the angular area of a compressor with a changing dihedral angle is creatively proposed. By comparing the MDJ diffusion factor of the compressor blade with the critical MDJ diffusion factor, a high-precision prediction of the flow state in the angular area of the blade channel is achieved.
[0004] This method is implemented using the following technical solutions.
[0005] Firstly, based on the geometric parameters of the compressor blades, the quantitative parameters that can characterize the development speed of the corner zone intersection boundary layer under different inlet dihedral angles, inlet / outlet dihedral angle differences, and adverse pressure gradient environments are calculated through a large number of variable dihedral angle expansion duct physical models.
[0006] Then, the quantitative parameters of the boundary layer in the corner area are calculated and combined with the influence of secondary flow to establish an MDJ diffusion factor that can reflect the development of the flow in the corner area under the condition of variable dihedral angle.
[0007] Finally, the MDJ diffusion factor of the compressor blade is compared with the critical MDJ diffusion factor to determine whether corner separation or corner stall occurs in the blade channel.
[0008] Beneficial effects
[0009] The method of the present invention not only ensures the prediction accuracy of the flow state of the plane blade cascade, but also effectively improves the prediction ability of the flow phenomenon in the three-dimensional blade corner area of the modern compressor. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 is a flow chart of the method of the present invention;
[0011] Figure 2 This is a schematic diagram of the geometric shape of a compressor cascade;
[0012] Figure 3 This is a geometric diagram of the blade profile of a compressor cascade. DETAILED DESCRIPTION
[0013] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.
[0014] like Figure 1 As shown, a method for predicting compressor angular separation / stall with respect to dihedral angle variation includes the following steps:
[0015] Step 1: Based on the geometric parameters of the compressor blade, calculate the quantitative parameters that characterize the development speed of the intersection boundary layer in the corner region under different inlet dihedral angles, inlet / outlet dihedral angle differences, and adverse pressure gradient conditions, constructed using the variable dihedral angle expansion duct physical model. The variable dihedral angle expansion duct physical model is an expansion duct with different inlet and outlet dihedral angles. The dihedral angle is the angle formed by the adjacent walls on either side of the corner region; in the case of a compressor blade, it is the angle formed between the suction surface and the end wall.
[0016] The empirical relationship of the quantization parameters is as follows:
[0017]
[0018] in, is a quantitative parameter for the boundary layer in the corner region. e is a natural constant. Since this parameter needs to be applied to evaluate the development of the flow in the corner region of the compressor, ε1 is the dihedral angle of the leading edge of the compressor blade under the angle system, and Δε is the difference between the dihedral angle of the leading edge and the dihedral angle of the trailing edge under the angle system, where the dihedral angle is the angle formed between the suction surface of the compressor blade and the end wall;
[0019] C p The term is calculated using the ideal static pressure lift coefficient formula of the compressor, which is as follows:
[0020]
[0021] Among them, α1 and α2 are the inlet and outlet airflow angles of the compressor blade in radians, respectively.
[0022] When the inlet and outlet airflow angles of the compressor blades are unknown, the metal angle of the blades is used for estimation.
[0023] Step 2: Based on the geometric parameters of the compressor blades, calculate the quantitative parameters of the boundary layer in the corner area and combine them with the influence of the secondary flow to establish an MDJ diffusion factor that can reflect the development of the flow in the corner area under the condition of variable dihedral angle. The expression of the MDJ diffusion factor is as follows:
[0024]
[0025] Where σ represents the compressor blade density, c is the blade chord length, and s is the blade pitch.
[0026] Step 3: Compare the MDJ diffusion factor of the compressor blade with the critical MDJ diffusion factor to determine whether corner separation or corner stall occurs in the blade passage.
[0027] The critical MDJ diffusion factor is: MDJ crit =0.038±0.0013, where ±0.0013 is the error range.
[0028] Furthermore, the process of judging compressor blade corner separation / stall is as follows:
[0029] When MDJ>(0.038+0.0013), it is predicted that corner stall will occur in the compressor blade passage;
[0030] When MDJ < (0.038-0.0013), angular separation is considered to have occurred;
[0031] When the MDJ diffusion factor value is in the range of (0.038+0.0013) to (0.038-0.0013), it is considered that the flow state in the corner area of the compressor blade channel cannot be predicted.
[0032] Example
[0033] Taking a compressor blade cascade as an example, the method of the present invention is used to predict the flow state in the blade corner area. Figure 2 As shown, its blade geometry and geometric parameters are as follows Figure 3 and as shown in Table 1.
[0034] Table 1 Blade geometry parameters
[0035]
[0036] Based on the cascade's geometric parameters, the calculated quantitative parameter for the boundary layer in the angular region of the cascade is 0.0457, corresponding to a MDJ diffusion factor of 0.0196. Since the MDJ is less than (0.038-0.0013), angular separation is considered to occur. The results indicate that angular separation does occur in the cascade channel, confirming the correctness of the prediction.
Claims
1. A method for predicting compressor angular separation / stall with respect to dihedral angle variation, characterized in that: The following steps are involved: Step 1: Based on the geometric parameters of the compressor blades, calculate the quantitative parameters that can characterize the development speed of the corner boundary layer under different inlet dihedral angles, inlet / outlet dihedral angle differences, and adverse pressure gradient environments constructed by the variable dihedral angle expansion duct physical model; Among them, the empirical relationship of the quantization parameter is as follows: in, is the quantitative parameter of the boundary layer in the corner area; e is a natural constant; ε1 is the dihedral angle of the leading edge of the compressor blade under the angle system, Δε is the difference between the dihedral angle of the leading edge and the dihedral angle of the trailing edge under the angle system, where the dihedral angle is the angle formed between the suction surface and the end wall of the compressor blade; C p The term is calculated using the ideal static pressure lift coefficient formula of the compressor, which is as follows: Among them, α1 and α2 are the inlet and outlet airflow angles of the compressor blade under the radian system respectively; Step 2: Based on the geometric parameters of the compressor blades, the quantitative parameters of the boundary layer in the corner area are calculated and combined with the influence of the secondary flow to establish an MDJ diffusion factor that can reflect the flow development in the corner area under the condition of variable dihedral angle. The expression of the MDJ diffusion factor is as follows: Where, σ represents the compressor blade density, c is the blade chord length, and s is the blade pitch; Step 3: Compare the MDJ diffusion factor of the compressor blade with the critical MDJ diffusion factor to determine whether corner separation or corner stall occurs in the blade passage.
2. The method for predicting compressor angular separation / stall with respect to dihedral angle variation according to claim 1, wherein: The physical model of the variable dihedral angle expansion pipe is an expansion pipe with different inlet dihedral angles and outlet dihedral angles.
3. The method for predicting compressor angular separation / stall with respect to dihedral angle variation according to claim 2, wherein: The dihedral angle is the angle formed by the adjacent walls on both sides of the corner area. In the compressor blade, it is the angle formed between the suction surface and the end wall.
4. The method for predicting compressor angular separation / stall with respect to dihedral angle variation according to claim 1, wherein: During the design phase, when the inlet and outlet airflow angles of the compressor blades are unknown, the metal angle of the blades is used for estimation.
5. The method for predicting compressor angular separation / stall with respect to dihedral angle variation according to claim 1, wherein: The critical MDJ diffusion factor is: MDJ crit =0.038±0.0013, where ±0.0013 is the error range.
6. The method for predicting compressor angular separation / stall with respect to dihedral angle variation according to claim 1, wherein: The process for determining compressor blade corner separation / stall is as follows: When MDJ>0.038+0.0013, it is predicted that corner stall will occur in the compressor blade passage; When MDJ < 0.038-0.0013, angular separation is considered to have occurred; When the MDJ diffusion factor value is within the range of 0.038±0.0013, it is considered that the flow state in the corner area of the compressor blade channel cannot be predicted.