Compressor numerical simulation method based on variable camber guide vane low-order model

Abstract

The invention belongs to the technical field of turbine fluid dynamics, and discloses a gas compressor numerical simulation method based on a variable camber guide vane low-order model. The method comprises the following steps: firstly, constructing a characteristic interface for replacing a variable camber guide vane three-dimensional model; then, according to the three-dimensional flow field data of the variable camber guide vane, a characteristic function that the total pressure loss changes along with the air flow pressure is constructed; then, the action of the variable camber guide vane on flow is simulated through the relation between upstream and downstream flow field parameters of a given characteristic interface, and then a variable camber guide vane low-order model is established; then, the low-order model is combined with a three-dimensional model of the gas compressor, and a high / low-order mixed model is constructed; and finally, carrying out flow field iterative calculation by adjusting the total pressure loss coefficient and the airflow deflection angle value until a calculation result converges. According to the numerical simulation method provided by the invention, the modeling cost can be effectively reduced, the calculation cost and time can be greatly reduced, and meanwhile, the flow field information can be comprehensively obtained.

Description

Technical Field

[0001] The present application belongs to the technical field of impeller fluid dynamics, and specifically relates to a compressor numerical simulation method based on a low-order model of variable-curvature guide vanes. Background Art

[0002] As a key component of aircraft engines, the performance of axial-flow compressors has a crucial impact on their overall performance. Currently, advanced axial-flow compressors are continuously advancing towards higher compression ratios, higher efficiency, and higher stability. Against this backdrop, imported variable guide vane technology has become an important means of improving compressor performance.

[0003] Adjustable guide vanes are mainly divided into two types: constant camber and variable camber. When the angle adjustment range of the constant camber guide vanes is large, serious airflow separation is prone to occur on the suction surface of the blades, which will greatly affect the performance of the compressor. The emergence of variable camber guide vanes effectively solves this problem and can better meet the performance requirements of the compressor when adjusted over a wide range. In the research and development of axial flow compressors, it is extremely important to accurately evaluate their performance under estimated design and non-design conditions. With the continuous deepening of compressor theory and the rapid development of computer technology, the compressor performance prediction method has also evolved from low-dimensional to high-dimensional.

[0004] Currently, the most typical high-dimensional method is three-dimensional numerical simulation. This method requires detailed geometric modeling of the entire compressor, followed by a series of operations such as meshing and preprocessing, numerical calculations, and finally post-processing. Three-dimensional numerical simulation methods can accurately predict the compressor flow field distribution and various performance indicators. However, the situation becomes more complicated when the compressor inlet is equipped with variable camber guide vanes. Since each adjustment of the variable camber guide vanes changes the compressor geometry, even for the same compressor, every adjustment of the inlet variable camber guide vanes requires a completely new model, starting from geometric modeling and completing numerical calculations. This requires a significant investment of time and computing resources, significantly increasing the research workload and computational cost. In contrast, existing low-dimensional prediction methods adopt a different approach. By defining characteristic sections that cause sudden changes in flow parameters, they establish a correlation between aerodynamic parameters between compressor stages. Compared with three-dimensional numerical simulation methods, low-dimensional prediction methods are simpler to implement, eliminating the need for repeated modeling, and can predict compressor performance with a certain degree of accuracy, thus saving time and computing resources. However, the low-dimensional prediction method also has obvious limitations and cannot obtain the three-dimensional flow field information of each stage inside the compressor.

[0005] Therefore, it is necessary to develop a simplified model and a simplified algorithm which are efficient and convenient and can obtain the three-dimensional flow field inside the compressor to accurately predict the performance of the compressor with variable camber vanes. SUMMARY

[0006] In view of the deficiencies in the existing compressor performance prediction technology, the present application aims to provide a numerical simulation method for a compressor based on a low-order model of variable camber vanes, which takes into account the efficiency and convenience of research and can obtain three-dimensional flow field information inside the compressor.

[0007] In one aspect of the present application, a numerical simulation method for a compressor based on a low-order model of variable camber vanes is provided, comprising the following steps:

[0008] S1: constructing a characteristic interface for replacing the three-dimensional model of the variable camber vanes, the characteristic interface being an interface between an upstream fluid domain and a downstream fluid domain along the airflow direction of the variable camber vanes;

[0009] S2: establishing a flow field parameter relationship on the upstream and downstream of the characteristic interface, the flow field parameter relationship including at least a mass conservation equation, an energy conservation equation, a total pressure loss equation and an airflow deflection equation;

[0010] S3: establishing a characteristic function of total pressure loss and airflow dynamic pressure according to the three-dimensional flow field data of the variable camber vanes:

[0011]

[0012] wherein, ΔP * represents the total pressure loss of the airflow flowing through the characteristic interface, k is a total pressure loss coefficient varying with the vane angle, ρ1 is the upstream airflow density of the characteristic interface, and v1 is the upstream airflow axial velocity of the characteristic interface;

[0013] S4: applying the characteristic function to the flow field parameter relationship to establish a low-order model of the variable camber vanes;

[0014] S5: combining the low-order model with the three-dimensional model of the compressor to construct a high / low-order hybrid model, and performing flow field iterative calculation by adjusting the total pressure loss coefficient k and the airflow deflection angle value until convergence.

[0015] In one embodiment, constructing the characteristic interface comprises: dividing the fluid domain containing the vanes into an upstream fluid domain and a downstream fluid domain at the central position of the variable camber vanes, and forming the characteristic interface by the interface intersecting the upstream fluid domain and the downstream fluid domain after removing the vane blades.

[0016] In one embodiment, the mass conservation equation is:

[0017]

[0018] in, are the gas mass flow rates upstream and downstream of the characteristic interface, respectively.

[0019] In one embodiment, the energy conservation equation is:

[0020]

[0021] in, are the total temperatures upstream and downstream of the characteristic interface, respectively.

[0022] In one embodiment, the total pressure loss equation is:

[0023]

[0024] in, are the total pressure upstream and downstream of the characteristic interface, ΔP * is the total pressure loss of airflow passing through the characteristic interface.

[0025] In one embodiment, the airflow deflection equation is:

[0026] β2-β1=α

[0027] Among them, β1 and β2 are the airflow angles upstream and downstream of the characteristic intersection surface, respectively, and α is the angle difference of the airflow deflection when flowing through the characteristic intersection surface.

[0028] In one embodiment, the determination of the total pressure loss coefficient k in step S3 includes:

[0029] S31: Establish a three-dimensional model of variable-camber guide vanes at different angles and calculate the flow field;

[0030] S32: Take the total pressure loss ΔP* and dynamic pressure 1 / 2ρv within the compressor working range 2 data;

[0031] S33: Obtain coefficient k through linear fitting.

[0032] In one embodiment, the low-order model includes:

[0033]

[0034] in, are the gas mass flow rates at the upstream outlet and downstream inlet of the characteristic interface, respectively; are the total temperatures at the upstream outlet and downstream inlet of the characteristic interface, respectively; are the total pressures at the upstream outlet and downstream inlet of the characteristic interface, respectively.

[0035] In one embodiment, the iterative calculation in step S5 uses the flow field result before the variable camber guide vane angle is adjusted as an initial value.

[0036] In another aspect of the present application, an electronic device is provided, comprising a processor and a memory, wherein the memory stores a computer program, and when the processor executes the computer program, the above-mentioned compressor numerical simulation method is implemented.

[0037] The beneficial effects of this application are:

[0038] 1) Modeling costs are significantly reduced

[0039] Compared to full 3D modeling flow field calculation methods, which require repeated 3D modeling and meshing when the guide vane angle changes, the compressor numerical simulation method based on the variable-camber guide vane low-order model in this application only requires a single modeling run, significantly reducing modeling costs. Specifically, the modeling cost can be reduced to 1 / n of the full 3D modeling cost (n is the number of times the guide vane angle needs to change), significantly improving modeling efficiency and cost-effectiveness.

[0040] 2) Computational cost and time are significantly reduced

[0041] When calculating the flow field for each guide vane angle model, the full 3D method must start with a very rough initialization flow field and solve it until the final converged flow field is reached. This process consumes a lot of computing time and resources. However, the numerical simulation method of this application uses the same calculation model for different guide vane angles. The flow field calculation after the angle change can be calculated based on the result of the previous angle flow field calculation, resulting in rapid convergence and significantly reducing computing time and resource consumption.

[0042] 3) Comprehensive acquisition of flow field information

[0043] While low-dimensional calculation methods can obtain average parameters and overall performance for each section of the compressor, they cannot provide detailed information about the flow field and parameters within the compressor. The numerical simulation method proposed in this application can significantly reduce computing resources and costs while accurately obtaining the three-dimensional flow field of the compressor rotor and stator, as well as the radial distribution of inter-stage parameters. This provides more detailed and accurate data support for compressor design and optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the characteristic intersection surface of the low-order model of the variable camber guide vane according to an embodiment of the present application;

[0045] Figure 2 This is a theoretical schematic diagram of a low-order model of a variable camber guide vane according to an embodiment of the present application;

[0046] Figure 3 is a total pressure loss characteristic curve of the variable camber guide vane according to an embodiment of the present application;

[0047] Figure 4 The computational grid of the high / low order hybrid model of the variable camber guide vane compressor according to the embodiment of the present application;

[0048] Figure 5 This is a comparison of the calculation results of the compressor characteristics of the embodiment of the present application;

[0049] Figure 6 This is a comparison of the radial distribution of aerodynamic parameters of the inter-stage cross-section of the embodiments of the present application. DETAILED DESCRIPTION

[0050] The technical solutions of the present application will be described clearly and completely below in conjunction with specific embodiments. However, those skilled in the art will understand that the embodiments described below are part of the embodiments of the present application, not all of them, and are only used to illustrate the present application and should not be considered to limit the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0051] In one embodiment of the present application, a numerical simulation method for a compressor based on a low-order model of a variable camber guide vane is provided, comprising the following steps:

[0052] S1: establishing a characteristic interface surface replacing the three-dimensional model of the variable camber guide vane, wherein the characteristic interface surface is located at the interface between the upstream fluid domain and the downstream fluid domain along the airflow direction of the variable camber guide vane.

[0053] In certain embodiments, a method for establishing a characteristic intersection surface is to divide the fluid domain of the variable-camber guide vane into upstream and downstream portions at the center of the guide vane, then remove the vanes. The intersection of the two fluid domains without the vanes is the characteristic intersection surface. By adjusting the relationship between flow field parameters before and after the characteristic intersection surface, the effects of the variable-camber guide vane on the flow field can be characterized, including total pressure loss, airflow deflection, mass conservation, and energy conservation.

[0054] S2: Establishing a flow field parameter relationship upstream and downstream of the characteristic intersection surface, wherein the flow field parameter relationship at least includes a mass conservation equation, an energy conservation equation, a total pressure loss equation, and an airflow deflection equation.

[0055] In certain embodiments, the mass conservation equation, energy conservation equation, total pressure loss equation, and airflow deflection equation are introduced to express the relationship between the flow field parameters upstream and downstream of the characteristic interface:

[0056] a) Conservation of mass

[0057] In any flow, mass conservation must be ensured, that is, the airflow rate flowing upstream of the blade is equal to the airflow rate flowing downstream of the blade. Therefore, in the low-order model, the following should be satisfied:

[0058]

[0059] in, are the gas mass flow rates upstream and downstream of the characteristic interface, respectively.

[0060] b) Conservation of energy

[0061] The flow through the variable-curvature guide vane is an absolute energy flow and complies with the law of energy conservation. Therefore, the low-order model should satisfy the following:

[0062]

[0063] Right now

[0064]

[0065] in, are the total enthalpy upstream and downstream of the characteristic interface, are the total temperatures upstream and downstream of the characteristic interface, respectively.

[0066] c) Total pressure loss

[0067] Airflow passing through the guide vanes will produce wake loss, separation loss, and mixing loss, and the larger the guide vane angle, the greater the total pressure loss. Therefore, the total pressure of the airflow flowing downstream of the blade should be equal to the total pressure of the airflow flowing upstream of the blade minus the corresponding total pressure loss. Therefore, in the low-order model, the following should be satisfied:

[0068]

[0069] in, are the total pressure upstream and downstream of the characteristic interface, ΔP * is the total pressure loss of airflow passing through the characteristic interface.

[0070] d) Airflow deflection

[0071] Adjusting the angle of the variable-camber guide vane will cause airflow deflection. In this embodiment, the influence of the airflow lagging angle is ignored, and the outlet airflow direction is assumed to be consistent with the guide vane outlet geometric angle direction. Therefore, the outlet airflow in the low-order model should satisfy the following relative to the inlet airflow:

[0072] β2-β1=α;

[0073] Among them, β1 and β2 are the airflow angles upstream and downstream of the characteristic intersection surface, respectively, and α is the angle difference of the airflow deflection when flowing through the characteristic intersection surface.

[0074] Furthermore, the downstream airflow direction is given in the form of axial and circumferential velocity components, where the axial component is 1 and the circumferential component is the tangent of the blade deflection angle.

[0075] S3: Establishing the relationship between total pressure loss and dynamic pressure according to the three-dimensional flow field data of the variable-pitch guide vane.

[0076] Specifically, the step of introducing the total pressure loss coefficient comprises:

[0077] S31: Establishing a three-dimensional model of the variable-pitch guide vane at different angles and performing calculation;

[0078] S32: Obtaining a curve of ΔP* with 1 / 2ρv 2 according to the calculation results;

[0079] S33: Selecting data in the stable working range of the compressor in the curve to obtain a linear relationship between ΔP* and 1 / 2ρv 2 and calculating the coefficient k;

[0080] S34: Obtaining a characteristic function conforming to the theory of throttling loss characteristics by combining the characteristic interface:

[0081]

[0082] wherein ρ1 is the density of the upstream airflow at the characteristic interface, v1 is the axial velocity of the upstream airflow at the characteristic interface, k is the total pressure loss coefficient, which changes with the guide vane angle and represents the size of the blocking effect of the variable-pitch guide vane at different opening angles on the airflow.

[0083] S4: Applying the characteristic function in S3 to the characteristic interface established in S1 to establish a low-order model of the variable-pitch guide vane.

[0084] The boundary condition of the upstream outlet surface is defined as The boundary condition of the downstream inlet surface is defined as The axial component of the airflow velocity is 1; and the circumferential component of the airflow velocity is tanα.

[0085] wherein are the mass flow rates of the upstream outlet and the downstream inlet at the characteristic interface, respectively; are the total temperatures of the upstream outlet and the downstream inlet at the characteristic interface, respectively; are the total pressures of the upstream outlet and the downstream inlet at the characteristic interface, respectively.

[0086] S5: Establishing a high / low-order hybrid model of the variable-pitch guide vane compressor and performing iterative calculation on the hybrid model.

[0087] In certain embodiments, a hybrid model is constructed and iteratively calculated by combining the low-order variable guide vane model in S4 with the three-dimensional compressor model to form a high- / low-order hybrid model of the variable guide vane compressor. When the variable guide vane angle changes, the values ​​of k and α are correspondingly changed, and the flow field is iteratively calculated until convergence conditions are met. Convergence conditions typically include residuals less than a certain threshold or no significant change in flow parameters. Through iteration, the model gradually approaches the actual flow state, ensuring the accuracy and reliability of the results.

[0088] Exemplary embodiments

[0089] like Figure 1 As shown, the fluid domain of the variable curvature guide vane is divided into two parts, upstream and downstream, at the center of the guide vane. The blades are removed, and the surface where the two fluid domains without the blades intersect is the characteristic intersection surface.

[0090] like Figure 2 As shown in the figure, the main parameters upstream and downstream of the variable curvature guide vane are flow rate, temperature, pressure, and airflow deflection angle. Considering the total pressure loss, airflow deflection, mass conservation, and energy conservation, the following characteristic function is introduced to represent the relationship between the flow field parameters before and after the S1 characteristic intersection surface:

[0091]

[0092] β2-β1=α(4)

[0093] The relationship between total pressure loss and airflow pressure is established by using the three-dimensional flow field data of variable curvature guide vanes, and the total pressure loss coefficient is introduced:

[0094] Establish and calculate three-dimensional models of variable-camber guide vanes at different angles;

[0095] According to the calculation results, ΔP * Follow-up pressure 1 / 2ρv 2 The change curve of Figure 3 As shown in the figure, by analyzing the total pressure loss characteristic curve of the variable curvature guide vane, it can be known that within the stable working range of the compressor, ΔP * and 1 / 2ρv 2 There is a certain relationship between the total pressure loss and the characteristic function that can represent the change of the variable curvature guide vane angle can be obtained by the total pressure loss relationship (3). Select the data within the stable working range of the compressor in the curve to obtain ΔP * and 1 / 2ρv 2 There is a linear relationship and its coefficient k is calculated. Combined with the characteristic intersection surface, the characteristic function that conforms to the throttling loss characteristic theory is obtained:

[0096]

[0097] The characteristic function is applied to the characteristic interface to establish a low-order model of the variable camber guide vane. Figure 1 The boundary conditions defining the upstream and midstream outlet surfaces are: exist Figure 1 The boundary conditions for the mid- and downstream inlet surfaces are: The axial component of the air flow velocity is 1, and the circumferential distribution of the air flow velocity is tanα.

[0098] The variable camber guide vane low-order model is combined with the compressor three-dimensional model to form a variable camber guide vane compressor high / low order hybrid model. Figure 4 As shown, the example used in this application is a two-stage and a half compressor model, which uses a characteristic interface surface instead of the guide vane (IGV). When the angle of the variable curvature guide vane changes, the values ​​of k and α on the characteristic interface surface are changed accordingly, and then the flow field is iteratively calculated until the convergence condition is met.

[0099] In this embodiment, the results calculated using the CFX software platform are used to demonstrate the effectiveness of the compressor numerical simulation method based on the variable camber guide vane low-order model.

[0100] Specifically, compared with conventional three-dimensional model calculation methods, this calculation method greatly saves modeling costs and computing resources, and significantly shortens calculation time while ensuring that the compressor characteristics and flow field characteristics can be accurately obtained. Figure 5 A comparison of the compressor characteristics calculation results is given. Through the comparison, it can be seen that the compressor pressure ratio / efficiency-flow characteristics and their changing trends predicted by the high / low-order hybrid calculation model are basically consistent with the prediction results of the full three-dimensional model. The average relative error of the flow calculation results under the six operating conditions is 0.91%, the average relative error of the pressure ratio is 0.45%, and the average relative error of the efficiency is 1.17%, which is in good agreement overall.

[0101] This calculation method can obtain accurate interstage flow field parameters while saving modeling costs and computing resources. Figure 6 A comparison of the radial distribution of aerodynamic parameters across the interstage cross-section is presented. It can be seen that at the first-stage rotor inlet, with only minor differences at the blade tip and root, the high- and low-order hybrid model accurately predicts the variations in various parameters across most blade heights, agreeing well with the results calculated using the full three-dimensional model. The radial distribution at the second-stage rotor inlet is more accurately predicted than that at the first-stage rotor inlet, with significant improvements in prediction accuracy at the blade root and tip. This suggests that the elimination of the true guide vane structure primarily impacts the flow field distribution at the guide vane outlet and at the first-stage rotor inlet, with a gradually decreasing impact on the flow field at subsequent stages.

[0102] Although the embodiments of the present application have been described above with reference to the accompanying drawings, the present application is not limited to the above-described specific embodiments and areas of application, and the above-described specific embodiments are merely illustrative and instructive, but are not restrictive. Many modifications can be made by those skilled in the art under the teachings of the present specification and without departing from the scope of the present application as defined by the claims.

Claims

1. A numerical simulation method for a compressor based on a low-order model of variable camber guide vanes, characterized in that: include: S1: constructing a characteristic interface surface for replacing the three-dimensional model of the variable camber guide vane, wherein the characteristic interface surface is located at the interface between the upstream fluid domain and the downstream fluid domain along the airflow direction of the variable camber guide vane; S2: establishing a flow field parameter relationship upstream and downstream of the characteristic interface, wherein the flow field parameter relationship includes at least a mass conservation equation, an energy conservation equation, a total pressure loss equation, and an airflow deflection equation; S3: Based on the three-dimensional flow field data of the variable curvature guide vane, the characteristic function of total pressure loss and airflow dynamic pressure is established: Where ΔP * represents the total pressure loss of the airflow passing through the characteristic intersection surface, k is the total pressure loss coefficient that changes with the guide vane angle, ρ1 is the airflow density upstream of the characteristic intersection surface, and v1 is the axial velocity of the airflow upstream of the characteristic intersection surface; S4: applying the characteristic function to the flow field parameter relationship to establish a low-order model of a variable-camber guide vane; S5: Combining the low-order model with the compressor three-dimensional model to construct a high / low-order hybrid model, and performing flow field iterative calculation until convergence by adjusting the total pressure loss coefficient k and the airflow deflection angle value.

2. The compressor numerical simulation method according to claim 1, characterized in that: Constructing the characteristic intersection surface includes: dividing the fluid domain containing the guide vane into an upstream fluid domain and a downstream fluid domain at the center position of the variable curvature guide vane, and after removing the guide vane blades, the interface where the upstream fluid domain and the downstream fluid domain intersect to form the characteristic intersection surface.

3. The compressor numerical simulation method according to claim 1, characterized in that: The mass conservation equation is: in, are the gas mass flow rates upstream and downstream of the characteristic interface, respectively.

4. The compressor numerical simulation method according to claim 1, characterized in that: The energy conservation equation is: in, are the total temperatures upstream and downstream of the characteristic interface, respectively.

5. The compressor numerical simulation method according to claim 1, characterized in that: The total pressure loss equation is: in, are the total pressure upstream and downstream of the characteristic interface, ΔP * is the total pressure loss of airflow passing through the characteristic interface.

6. The compressor numerical simulation method according to claim 1, characterized in that: The airflow deflection equation is: β2-β1＝α Among them, β1 and β2 are the airflow angles upstream and downstream of the characteristic intersection surface, respectively, and α is the angle difference of the airflow deflection when flowing through the characteristic intersection surface.

7. The compressor numerical simulation method according to claim 1, characterized in that: The determination of the total pressure loss coefficient k in step S3 includes: S31: Establish a three-dimensional model of variable-camber guide vanes at different angles and calculate the flow field; S32: Take the total pressure loss ΔP* and dynamic pressure 1 / 2ρv within the compressor working range 2 data; S33: Obtain coefficient k through linear fitting.

8. The compressor numerical simulation method according to claim 1, characterized in that: The low-level model includes: in, are the gas mass flow rates at the upstream outlet and downstream inlet of the characteristic interface, respectively; are the total temperatures at the upstream outlet and downstream inlet of the characteristic interface, respectively; are the total pressures at the upstream outlet and downstream inlet of the characteristic interface, respectively.

9. The compressor numerical simulation method according to claim 1, characterized in that: The iterative calculation in step S5 uses the flow field result before the variable camber guide vane angle is adjusted as an initial value.

10. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores a computer program, and when the processor executes the computer program, the method for numerical simulation of a compressor according to any one of claims 1 to 9 is implemented.

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