Method for calculating low-rotating-speed characteristic of fan component of aero-engine

Abstract

The invention discloses an aero-engine fan component low-rotating-speed characteristic calculation method. The method comprises the steps that a fan component model is defined; three-dimensional pneumatic simulation is executed, characteristic calculation is carried out, and the state of a design point is obtained; performing three-dimensional pneumatic simulation on the fan component model in the design point state, extracting design point load parameters, and obtaining a cold state; performing three-dimensional pneumatic simulation on the fan component model in the cold state, extracting cold state load parameters, and obtaining a hot state; according to the cold state of the fan component model, a hot runner of the fan component model at each rotating speed is obtained; the blade tip gaps at different rotating speeds are calculated by combining the thermal-state flow channel and the thermal-state state; and carrying out three-dimensional pneumatic simulation by combining the thermal-state blade profile, the thermal-state flow channel and the blade tip gap, and carrying out characteristic calculation to obtain the low-rotating-speed characteristic of the fan component. According to the technical scheme, the problem that the low-rotating-speed state characteristic calculation of the fan component is inaccurate can be solved, and more accurate component characteristics are provided to support a component design scheme.

Description

Technical Field

[0001] This invention relates to the field of heat transfer in aero-engine impellers based on simulation design, and more specifically, to a method for calculating the low-speed characteristics of aero-engine fan components. Background Technology

[0002] Since their introduction in the 1940s, aero-gas turbine engines have made tremendous technological progress in just over half a century, playing a crucial role in driving the development of the entire aviation industry. As key components of aero-engines, the fan / compressor is technically demanding and complex to analyze, often becoming a significant obstacle to the successful development of new engines. This is not only reflected in its decisive role in performance parameters such as thrust-to-weight ratio and fuel consumption rate, but also in its significant impact on the overall stability and reliability of the engine. Experience in fan / compressor development shows that its success or failure directly affects the overall development of aero-engines. With the continuous improvement of the thrust-to-weight ratio of aero-engines, the requirements for the performance, efficiency, and stability of the fan / compressor are also increasing. Therefore, it is necessary to continuously develop and improve design and calculation methods adapted to the aerodynamic design system of the fan / compressor.

[0003] In the design of fan components, performance calculation and analysis at non-design points is a crucial part of the aerodynamic design system and an indispensable component throughout the entire design process. Currently, single-channel steady-state CFD methods are primarily used in engineering applications to calculate fan characteristics. Practical experience shows that calculated and experimental characteristics agree well in the high-speed range, but deviate significantly from experimental characteristics in the low-speed range. Large discrepancies exist in efficiency-flow rate, pressure ratio, efficiency, and surge margin, with the characteristic curve shifting generally to the left and the stability boundary moving significantly outward. This leads to optimistic surge margin evaluations and negative efficiency evaluations, as illustrated by the comparison results. Figure 1 As shown.

[0004] The reasons are analyzed as follows: 1. Due to the effects of aerodynamic loads, temperature loads, and centrifugal force, fan blades will undergo torsional deformation during operation, resulting in changes in the fan blade profile and angle of attack at different speeds, which in turn leads to changes in aerodynamic performance. Simulating the full-speed characteristics using the designed blade profile will show that the blade profile at low speeds changes significantly compared to the designed blade profile, resulting in inaccurate characteristic calculation results. 2. During operation, the wheel and casing parts deform, meaning the flow channel changes: The deformation of the wheel and casing parts has a significant impact on the flow capacity of the fan components. The flow area directly determines the airflow of the fan components, which in turn determines the thrust of the aero-engine, and has a significant impact on the performance of the aircraft. Using the flow channel at the design point state for full-speed characteristic simulation will result in deviations between the simulation results at medium and high speeds and the actual state, leading to inaccurate characteristic calculation results. 3. Tip clearance varies significantly at different speeds: Tip clearance generates tip leakage flow, which degrades the flow field quality, reduces the efficiency of fan components, and consequently increases the fuel consumption of aero engines, affecting effective range and economy; at low speeds, tip clearance can often differ from the design speed by more than double. Using the tip clearance at the design point for full-speed characteristic simulation will lead to an overly optimistic assessment of fan component efficiency in the simulation results.

[0005] Therefore, a calculation method is needed for the characteristics of aero-engine fan components under low-speed conditions to solve the problem of inaccurate calculation of the low-speed characteristics of fan components. Summary of the Invention

[0006] To achieve the above objectives, this application provides a method for calculating the low-speed characteristics of an aero-engine fan component, comprising the following steps: Define a fan component model, whose structure includes blade profile and flow channel, and whose parameters include load parameters and blade tip clearance; the load parameters are the static temperature and static air pressure of the first layer of mesh on the blade surface, and the load parameters include: aerodynamic load and temperature load; Perform 3D aerodynamic simulation, calculate characteristics, and obtain the design point state of the fan component model; A three-dimensional aerodynamic simulation was performed on the fan component model at the design point state to extract the load parameters at the design point and obtain the cold state of the fan component model. A three-dimensional aerodynamic simulation was performed on the fan component model in a cold state to extract the cold load parameters and obtain the hot state of the fan component model. Based on the cold state of the fan component model, obtain the hot flow channel of the fan component model at each speed. By combining the hot flow channel and the fan component model under hot conditions, the tip clearance at different speeds is calculated; by combining the hot airfoil, the hot flow channel and the tip clearance, three-dimensional aerodynamic simulation is performed to calculate the characteristics and obtain the low-speed characteristics of the fan component; the low-speed characteristics include: pressure ratio, efficiency, airflow and surge margin.

[0007] When performing characteristic calculations, the turbulence model is set to the Spalart-Allmaras single-equation model, the working fluid is an ideal gas, the inlet boundary conditions are given as total temperature and total pressure, and the outlet boundary conditions are given as static temperature and static pressure. When performing characteristic calculations, the outlet static pressure is adjusted to obtain performance parameters at different pressure ratio points; when the performance parameters reach the standard state, the pressure ratio point corresponding to the outlet static pressure reaches a stable state.

[0008] Furthermore, obtaining the cold state of the fan component model includes the following steps: The design point load parameters are applied to the blade surface of the fan component model; Combined with centrifugal force and blade material characteristics; Deformation calculations are performed on the blades to generate a cold state.

[0009] Obtaining the thermal state of the fan component model includes the following steps: Apply cold load parameters to the blade surface of the fan component model; The superposition of centrifugal force and blade material characteristics; Deformation calculations were performed on the blades to generate hot blade profiles at different rotational speeds.

[0010] Furthermore, obtaining the hot flow path of the fan component model at various speeds includes the following steps: Based on the cold state fan component model, the cold state flow field is obtained, and the surface temperature and pressure of the impeller and casing are extracted. Deformation calculations were performed on the casing; After performing deformation calculations on the centrifugal force superimposed on the wheel, the hot flow channels at different rotational speeds are obtained.

[0011] Calculating the tip clearance at different speeds involves the following steps: Obtain the deformation of the wheel and the deformation of the casing in the hot flow channel; Three-dimensional aerodynamic simulation was performed based on the fan component model in the aforementioned thermal state. Calculate the tip clearance at different speeds to construct the hot tip clearance.

[0012] Among them, three-dimensional aerodynamic simulation is achieved through third-party tools such as NUMECA or ANSYS CFX, while deformation simulation can be achieved through finite element analysis tools.

[0013] This invention considers the deformation of the blade profile at different speeds of fan components, the flow channel deformation caused by the deformation of the impeller and casing, the changes in blade profile, and the changes in tip clearance caused by the changes in the flow channel. It regenerates the blade profile, flow channel, and tip clearance for aerodynamic simulation based on the aerodynamic loads, temperature loads, and centrifugal forces acting on the blades, impeller, and casing at different speeds. This solves the problem of inaccurate calculation of the low-speed characteristics of fan components. More accurate component characteristics are beneficial for component design evaluation and overall machine performance matching. Attached Figure Description

[0014] Figure 1This is a schematic diagram comparing the pressure ratio-mass flow rate characteristics and efficiency-mass flow rate characteristics at the design point with experimental results, based on existing technologies. Figure 2 This is a step diagram of a method for calculating the characteristics of an aero-engine fan component according to an embodiment of the present invention; Figure 3 The first layer of mesh aerodynamic load and temperature load on the airfoil surface at the design point state provided by the embodiment of the present invention; Figure 4 This is a schematic diagram of the deformation distribution on the blade surface provided according to an embodiment of the present invention; Figure 5 This is a schematic diagram comparing blades in hot and cold states according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the surface temperature and pressure distribution of the wheel and casing at a certain rotational speed according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the wheel deformation distribution at a certain rotational speed according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the casing deformation distribution at a certain rotational speed according to an embodiment of the present invention; Figure 9 This is a schematic diagram comparing hot and cold flow channels according to an embodiment of the present invention; Figure 10 This is a schematic diagram comparing the pressure ratio-mass flow rate characteristics and efficiency-mass flow rate characteristics obtained by the calculation method provided in the embodiments of the present invention with the experimental results. Detailed Implementation

[0015] The specific implementation of the present invention will now be described in detail with reference to the accompanying drawings.

[0016] The steps of the method for calculating the low-speed characteristics of aero-engine fan components considering hot and cold airfoil transitions, flow channel deformation, and tip clearance provided by this invention are as follows: Figure 2 As shown, it includes the following steps: Step S100: Define a fan component model. The structure of the fan component model includes blade profile and flow channel. The flow channel includes a disk and a casing. The parameters include load parameters and blade tip clearance. The load parameters include aerodynamic load and temperature load. In this step, a fan component model is constructed based on the blade design for subsequent 3D aerodynamic simulation. In this invention, the 3D aerodynamic simulation is achieved using third-party tools such as NUMECA or ANSYS CFX, while deformation simulation can be performed using finite element analysis tools.

[0017] Step S110: Perform three-dimensional aerodynamic simulation, calculate characteristics, and obtain the design point state of the fan component model; When performing characteristic calculations, the turbulence model is set as the Spalart-Allmaras single-equation model, the working fluid is an ideal gas, the inlet boundary conditions are given as total temperature and total pressure, and the outlet boundary conditions are given as static temperature and static pressure. The performance parameters are obtained at different pressure ratio points by adjusting the outlet static pressure. When the performance parameters reach the standard state, the pressure ratio point corresponding to the outlet static pressure reaches the stable state, which is the design point state, that is, the design point is found.

[0018] The static temperature and static pressure of the first layer of mesh on the airfoil surface are as follows: Figure 3 As shown, these are the load parameters used for calculating airfoil deformation under various conditions. The load parameters at the design point are the design point load parameters and can be used for subsequent airfoil deformation calculations.

[0019] Step S120: Perform three-dimensional aerodynamic simulation on the fan component model at the design point state, extract the load parameters at the design point, and obtain the cold state of the fan component model; This step is implemented using the general finite element method, and includes the following steps: The design point load parameters are applied to the blade surface of the fan component model under the design point condition. Simultaneously, centrifugal force is superimposed, and blade material characteristics are set; blade material characteristics include Young's modulus, Poisson's ratio, and density, as shown in the table below: Deformation calculations are performed on the blade to generate a cold state, at which point the deformation distribution on the blade surface is as follows: Figure 4 As shown.

[0020] Step S130: Perform three-dimensional aerodynamic simulation on the fan component model under cold state, extract cold load parameters, and obtain the hot state of the fan component model; In this step, based on the airfoil in the cold state, a three-dimensional aerodynamic simulation is performed, and characteristic calculations are carried out. The static temperature and static pressure of the first layer of mesh on the airfoil surface in the cold state are further obtained as cold load parameters. Apply cold load parameters to the blade surface of the fan component model in a cold state; Superimpose centrifugal force and set blade material characteristics; Deformation calculations are performed on the blades, which can then generate hot blade profiles at different rotational speeds.

[0021] Comparison of blade shapes in cold and hot states, for example Figure 5 As shown.

[0022] Step S140: Based on the cold state of the fan component model, obtain the hot flow channel of the fan component model at each speed. The hot flow channel is obtained based on the cold state of the fan component model, specifically generated through calculation using the finite element method, including the following steps: Based on the cold-state fan component model, the cold-state flow field is obtained, and the surface temperature and pressure of the impeller and casing are extracted. The surface temperature and pressure distribution of the impeller and casing are as follows: Figure 6 As shown; Deformation calculations were performed on the casing based on its surface temperature and pressure. The deformation distribution of the casing is shown below. Figure 8 As shown in the table below: Based on the surface temperature and pressure of the disk, centrifugal force is superimposed to calculate the deformation of the disk; the deformation distribution of the disk is as follows: Figure 7 As shown in the table below, the deformation of the wheel is as follows: At this point, the hot flow channel at different rotation speeds can be obtained, and the comparison between the hot and cold flow channels is as follows: Figure 9 As shown.

[0023] Step S150: Combine the hot flow channel and the blade profile under the hot state of the fan component model to calculate the tip clearance at different speeds; Calculating the tip clearance at different speeds involves the following steps: Obtain the deformation of the wheel and the deformation of the casing in the hot flow channel in step S140; Three-dimensional aerodynamic simulation is performed based on the blade shape of the fan component model generated by S130 in its thermal state. Calculate the tip clearance at different speeds to generate a hot tip clearance.

[0024] The hot blade tip clearance at different rotational speeds is shown in the table below: Step S160: Perform three-dimensional aerodynamic simulation and characteristic calculation on the fan component model under the hot state to obtain the low speed characteristics of the fan component; the low speed characteristics include: pressure ratio, efficiency, airflow and surge margin.

[0025] In this step, a three-dimensional aerodynamic simulation is performed by combining the hot airfoil, hot flow channel, and hot tip clearance. Characteristic calculations are then performed, and the fan component characteristics are obtained by adjusting the outlet static pressure until the calculation cannot converge at the same rotational speed.

[0026] A comparison of the pressure ratio-mass flow rate characteristics and efficiency-mass flow rate characteristics under design point conditions, the method provided by this invention, and experimental conditions is shown below. Figure 9 As shown in the figure, the calculated characteristics obtained by the calculation method provided by the present invention, such as surge boundary, efficiency, pressure ratio, and mass flow rate, are closer to the experimental results.

[0027] This invention considers the impact of blade deformation caused by aerodynamic loads, temperature loads, and centrifugal forces on aerodynamic performance at different speeds, making the design point state of the fan components closer to the actual working conditions. It generates hot-state blade profiles for characteristic calculations at different speeds. Simultaneously, it also considers the changes in the flow channel caused by the deformation of the impeller and casing parts under aerodynamic loads, temperature loads, and centrifugal forces at different speeds, generating hot-state flow channels for characteristic calculations at different speeds. Furthermore, it incorporates the influence of blade profile and flow channel changes on tip clearance at different speeds, calculating hot-state tip clearances for hot-state blade profiles and hot-state flow channels at different speeds to obtain tip clearances closer to actual working conditions. This allows for the setting of different tip clearances for different speeds and characteristic calculations. The final calculated characteristics, including surge boundary, efficiency, pressure ratio, and mass flow rate, are closer to experimental results, facilitating accurate evaluation of design schemes and the implementation of overall machine matching.

[0028] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the present invention is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for calculating the low-speed characteristics of an aero-engine fan component, characterized in that, Includes the following steps: Define a fan component model, the structure of which includes blade profile and flow channel, and the parameters include load parameters and blade tip clearance; The load parameters are the static temperature and static air pressure of the first layer of the airfoil surface, and the load parameters include: aerodynamic load and temperature load; Perform three-dimensional aerodynamic simulation, calculate characteristics, and obtain the design point state of the fan component model; A three-dimensional aerodynamic simulation was performed on the fan component model at the design point state to extract the load parameters at the design point and obtain the cold state of the fan component model. A three-dimensional aerodynamic simulation was performed on the fan component model in the cold state to extract the cold load parameters and obtain the hot state of the fan component model. Based on the cold state of the fan component model, obtain the hot flow channel of the fan component model at each speed. By combining the hot flow channel and the fan component model under the hot state, the tip clearance at different speeds is calculated; by combining the hot airfoil, the hot flow channel and the tip clearance, a three-dimensional aerodynamic simulation is performed to calculate the characteristics and obtain the low-speed characteristics of the fan component; the low-speed characteristics include: pressure ratio, efficiency, airflow and surge margin.

2. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 1, characterized in that, When performing characteristic calculations, the turbulence model is set to the Spalart-Allmaras single-equation model, the working fluid is an ideal gas, the inlet boundary conditions are given as total temperature and total pressure, and the outlet boundary conditions are given as static temperature and static pressure. When performing characteristic calculations, the outlet static pressure is adjusted to obtain performance parameters at different pressure ratio points; when the performance parameters reach the standard state, the pressure ratio point corresponding to the outlet static pressure reaches a stable state.

3. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 1, characterized in that, Obtaining the cold state of the fan component model includes the following steps: The design point load parameters are applied to the blade surface of the fan component model; Superimposed centrifugal force and blade material characteristics; Deformation calculations are performed on the blades to generate a cold state.

4. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 1, characterized in that, The process of obtaining the thermal state of the fan component model includes the following steps: The cold load parameters are applied to the blade surface of the fan component model; The superposition of centrifugal force and blade material characteristics; Deformation calculations were performed on the blades to generate hot blade profiles at different rotational speeds.

5. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 1, characterized in that, The process of obtaining the hot flow channel of the fan component model at various speeds includes the following steps: Based on the cold state fan component model, the cold state flow field is obtained, and the surface temperature and pressure of the impeller and casing are extracted. Deformation calculations were performed on the casing; After performing deformation calculations on the superimposed centrifugal force of the wheel, the hot flow channels at different rotational speeds are obtained.

6. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 5, characterized in that, The calculation of the blade tip clearance at different speeds includes the following steps: Obtain the deformation of the wheel and the deformation of the casing in the hot flow channel; Three-dimensional aerodynamic simulation was performed based on the fan component model in the aforementioned thermal state. Calculate the tip clearance at different speeds to construct the hot tip clearance.

7. The method for calculating the low-speed characteristics of an aero-engine fan component according to claim 5, characterized in that, Three-dimensional aerodynamic simulation is achieved using third-party tools such as NUMECA or ANSYS CFX, while deformation simulation can be achieved using finite element analysis tools.

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