Numerical simulation ice shape calculation method for overcooled large water drop icing of rotating cap hood

Abstract

The invention discloses a numerical simulation ice shape calculation method, system, equipment and medium for overcooled large water drop icing of a rotating cap hood, and relates to the technical field of aviation anti-icing. Comprising the following steps: calculating the impact characteristics of the supercooled large water drops; an engine rotating cap cover icing thermodynamic model is established, and the icing quality is solved; the moving height and the moving direction of the icing boundary grid nodes are calculated, and the icing boundary is moved. According to the method, in the icing calculation of the rotating cap hood of the engine, the mass loss of water drops caused by breakage of large supercooled water drops in the movement process and rebound and splashing of the water drops is considered, the influence of the pressure gradient, the air shear force and the centrifugal force on water film flowing is comprehensively considered, and an icing thermodynamic model suitable for a three-dimensional rotating part is established; according to the method, the ice shape of the engine rotating cap hood in the supercooled large water drop icing environment is calculated by using a multi-step method, the accuracy of the ice shape calculation result is high, and support is provided for supercooled large water drop icing airworthiness conformity verification.

Description

Technical Field

[0001] The present application relates to the field of aviation anti-icing technology, and in particular to a numerical simulation ice shape calculation method, system, equipment and medium for the freezing of supercooled large water droplets on a rotating cap. Background Art

[0002] Due to the complex structure of aircraft engines, many parts will freeze as long as certain conditions are met. In particular, when the engine's inlet parts are severely frozen, such as the lip and rotating cap, the flow channel will be blocked, the flow area will be reduced, the air flow will be reduced, and the engine thrust will be reduced; secondly, the engine icing will increase the intake distortion, which may cause the engine to stall and surge; when the detached ice is sucked into the engine, it may damage the compressor blades and even cause the engine to stall.

[0003] Since aircraft engine icing seriously threatens the operational safety of aircraft engines, in order to further improve the safety level of engines in icing environments, the FAA issued Amendment No. 140 to FAR Part 25 in 2014. Based on the original provisions on supercooled water droplets icing, this amendment adds requirements for the airworthiness of turbine engines in supercooled large water droplets (supercooled water droplets with an average volume diameter of water droplets greater than 50μm) icing environments. The rotating cap is an important imported component of aircraft engines and is also a component that is prone to icing. When severe icing occurs, it will seriously affect the operational safety of the engine.

[0004] At present, the theoretical research, experimental research and numerical simulation technology of supercooled water droplet freezing have been relatively mature, but the research on supercooled large water droplets is still in the development stage. The traditional theory of supercooled water droplet freezing believes that supercooled water droplets always maintain a spherical shape during movement, and there is no deformation, breakage, splashing and rebound of water droplets. However, due to its large diameter, supercooled water droplets will produce deformation, breakage, splashing and rebound, which brings great difficulties to the numerical simulation of supercooled large water droplet freezing. Moreover, the current research on supercooled large water droplet freezing is mostly aimed at stationary parts, and there is less research on rotating parts. At the same time, there is a lack of ice shape data from supercooled large water droplet freezing experiments on rotating parts to verify the numerical simulation method. In recent years, the secondary development of commercial software FLUENT to achieve ice shape prediction has gradually become the mainstream, but there is a lack of ice shape prediction methods for three-dimensional components based on multi-step methods, which brings great difficulties to the calculation of ice shape of rotating cap icing.

[0005] It can be seen that in the traditional numerical simulation calculation of supercooled large water droplets freezing, the deformation, breakage, splashing and rebound of water droplets in motion are not taken into account, and the single-step method is often used to calculate the freezing time of rotating parts, resulting in large errors in the ice shape calculation results. Summary of the invention

[0006] Based on this, it is necessary to provide a numerical simulation ice shape calculation method, system, equipment and medium for the freezing of supercooled large water droplets on a rotating cap to address the above technical problems.

[0007] This manual adopts the following technical solutions:

[0008] This specification provides a numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap, including:

[0009] Read the computational grid file into the numerical simulation software and determine the air flow field;

[0010] According to the water drop motion control equation, the breakup of supercooled large water droplets during motion is considered, and the motion trajectory of supercooled large water droplets in the air flow field is obtained; at the same time, according to the water drop motion control equation, the mass loss of water droplets caused by rebound and splashing of supercooled large water droplets is considered, and the local water collection coefficient of the engine rotating cap is obtained;

[0011] According to the motion trajectory of supercooled large water droplets in the air flow field and the local water collection coefficient of the engine rotating cap, a thermodynamic model of engine rotating cap ice formation is established, and the ice mass is obtained by solving the model.

[0012] According to the ice mass, the moving height and moving direction of the ice boundary grid node are calculated; and the ice boundary is moved according to the moving height and moving direction to obtain the geometric shape after ice formation;

[0013] It is determined whether the engine rotating cap has reached the freezing time according to the current calculation time. If so, the geometric shape after freezing corresponding to the current calculation time is used as the final ice shape; if not, the geometric shape after freezing is re-determined by re-reading the calculation grid file after the calculation grid is re-divided into the numerical simulation software until the freezing time is reached, and the geometric shape after freezing corresponding to the current calculation time is used as the final ice shape.

[0014] Preferably, obtaining the motion trajectory of the supercooled large water droplets in the air flow field specifically comprises the following steps:

[0015] The water drop drag coefficient is calculated by weighting the spherical drag coefficient and the disk drag coefficient;

[0016] The air resistance of a single water droplet is obtained through the water droplet drag coefficient, water droplet diameter, air relative velocity vector, and water droplet relative velocity vector;

[0017] Based on the change in the number of water droplets caused by the breakup of supercooled large water droplets, the water droplet number density equation is solved;

[0018] The control equation of water drop motion under steady-state calculation is obtained from the air resistance of a single water drop, water drop number density, water drop relative velocity vector, air density, water drop density, water drop volume fraction and gravity acceleration vector.

[0019] Based on FLUENT UDS, the water droplet motion control equation under the Euler method is solved to obtain the motion trajectory of supercooled large water droplets in the air flow field.

[0020] Preferably, the step of establishing a thermodynamic model of icing of the engine rotary cap and solving the model to obtain the icing mass specifically comprises the following steps:

[0021] The momentum equation of the water film on the engine rotating cap is established based on the average velocity of the water film, the dynamic viscosity coefficient of the water droplets, the pressure gradient, the rotating velocity vector of the rotating cap, the water droplet density and the rotating radius vector of the rotating cap.

[0022] The boundary conditions of the water film momentum equation are introduced, and the water film momentum equation is solved to obtain the distribution of the water film velocity along the thickness direction of the water film.

[0023] Then integrate the water film velocity along the water film thickness direction and take the average to obtain the average velocity of the water film;

[0024] The mass of water flowing out of the control body is calculated based on the average velocity of the water film, the area of ​​the water film outflow surface and the surface normal vector of the water film outflow surface;

[0025] Establish the water film energy conservation equation of the engine rotating cap: the sum of the total energy brought by the overflow water from the adjacent control body into the current control body, the energy brought by the water droplets hitting the rotating cap, the heat released by the water freezing into ice, and the aerodynamic heating is equal to the sum of the total energy taken away by the overflow water from the current control body, the heat absorbed by the evaporation of water in the control body, and the heat taken away by the convective heat exchange in the control body;

[0026] Establish the mass conservation equation of the water film on the engine rotating cap: the sum of the mass of water flowing into the current control body from the adjacent control body and the mass of water droplets hitting the rotating cap is equal to the sum of the mass of water flowing out of the control body, the mass of water frozen into ice in the control body, and the mass of water evaporated in the control body;

[0027] When the temperature of the ice control body is 0℃ and the initial water film thickness is 0, the water film momentum equation, the water film mass conservation equation and the water film momentum conservation equation are combined to solve the ice mass through an iterative cycle.

[0028] Preferably, judging whether the engine rotary cap has reached the freezing time according to the current calculation time specifically includes the following steps:

[0029] If the calculated time does not reach the freezing time, the boundary mesh file after the boundary movement needs to be output through the FLUENT software, and the file needs to be read by the FLUENT MESHING software to re-divide the calculation mesh;

[0030] After the meshing is completed, the updated mesh file is read through the FLUENT software, and the geometric shape and time after freezing are repeatedly calculated until the calculated time reaches the freezing time.

[0031] Preferably, the calculation of the moving height and moving direction of the grid nodes of the icing boundary specifically includes:

[0032] The moving height of the icing boundary grid nodes is calculated based on the icing mass, icing density, icing time step and the number of icing grid surfaces with common nodes;

[0033] The moving direction of the mesh node is obtained by calculating the average value of the surface normal vectors of the common node surface mesh.

[0034] Preferably, the step of moving the freezing boundary according to the moving height and the moving direction to obtain the geometric shape after freezing specifically includes:

[0035] The diffusion smoothing method in the dynamic mesh function of FLUENT numerical simulation software is used to move the ice boundary and obtain the mesh geometry after ice formation.

[0036] Preferably, the determining of the air flow field specifically includes:

[0037] The air flow field is obtained by solving the Reynolds-averaged Navier-Stokes equations in a steady-state rotating coordinate system using FLUENT software.

[0038] This specification provides a numerical simulation ice shape calculation system for supercooled large water droplets freezing on a rotating cap, including:

[0039] An air flow field calculation module, used to determine the air flow field;

[0040] The water drop impact characteristic calculation module is used to obtain the motion trajectory of the supercooled large water droplets in the air flow field according to the water drop motion control equation and consider the breakage of the supercooled large water droplets during the motion process; at the same time, according to the water drop motion control equation, the water drop mass loss caused by the rebound and splashing of the supercooled large water droplets is considered to obtain the local water collection coefficient of the engine rotating cap cover;

[0041] The icing thermodynamic model calculation module is used to establish an icing thermodynamic model of the engine rotating cap according to the motion trajectory of the supercooled large water droplets in the air flow field and the local water collection coefficient of the engine rotating cap, and solve the model to obtain the icing mass;

[0042] The icing shape calculation module is used to calculate the moving height and moving direction of the icing boundary grid node according to the icing mass; and move the icing boundary according to the moving height and moving direction to obtain the geometric shape after icing;

[0043] The multi-step time determination module is used to determine whether the engine rotating cap has reached the freezing time according to the current calculation time. If so, the freezing geometric shape corresponding to the current calculation time is used as the final freezing ice shape; if not, the freezing geometric shape is re-determined by re-reading the calculation grid file after the calculation grid is re-divided in the numerical simulation software until the freezing time is reached, and the freezing geometric shape corresponding to the current calculation time is used as the final freezing ice shape.

[0044] The present specification provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap.

[0045] The present specification provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the above-mentioned numerical simulation ice shape calculation method for supercooled large water droplet freezing of a rotating cap is implemented.

[0046] The numerical simulation ice shape calculation method for supercooled large water droplets on a rotating cap provided in this specification has the following beneficial effects compared with the prior art:

[0047] The numerical simulation calculation method for supercooled large water droplet icing on the rotating cap proposed in this manual not only takes into account the breakup of supercooled large water droplets in the process of movement, and the mass loss of water droplets caused by rebound and splashing of water droplets, but also comprehensively considers the influence of pressure gradient, air shear force and centrifugal force on water film flow, and realizes the calculation of ice shape of the engine rotating cap in the supercooled large water droplet icing environment using a multi-step method. The ice shape calculation results are highly accurate, providing data support for the airworthiness compliance verification of supercooled large water droplet icing. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0049] Figure 1 A schematic diagram of a flow chart of a numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap provided in this specification;

[0050] Figure 2A schematic diagram of an ice surface boundary movement method in a numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap provided in this specification;

[0051] Figure 3 This is the ice shape of the supercooled large water droplet freezing experiment of the rotating cap in the embodiment;

[0052] Figure 4 is a rotating cap geometric model used for numerical calculation in the embodiment;

[0053] Figure 5 The ice shape verification result of Exp1 in the embodiment;

[0054] Figure 6 This is the ice shape verification result of Exp2 in the embodiment. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of this specification more clear, the technical solutions of this application will be clearly and completely described below in combination with the specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in the specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0056] At present, a thermodynamic model of water film flow and freezing on a three-dimensional rotating surface has been established based on the Messinger model, and the ice shape of the rotating cap has been calculated using this model. The model realizes the distribution of overflow water on the rotating cap surface by establishing the water film momentum equation under rotating coordinates. The equation mainly considers centrifugal force, Coriolis force, and shear force, and does not consider the effect of pressure on water film flow. The FLUENT UDF is used to solve the model. However, the single-step method is still used for the calculation of ice shape, and the droplet size studied is still in the range of supercooled water droplets.

[0057] By solving the water drop impact characteristics of the rotating cap through FLUENT UDS, a thin water film icing model on the rotating surface in a body-fitting non-orthogonal curvilinear coordinate system was developed, and a multi-step method for calculating the icing of the rotating cap was realized. However, its icing calculation module does not use FLUENT UDF to write a solution program, but relies on Tecplot software for data extraction and combines it with a self-programmed calculation program for calculation, and the reconstruction of the grid depends on ICEM software.

[0058] The present invention proposes a three-dimensional numerical calculation method for supercooled large water droplet icing on a rotating cap, and provides an implementation method for single-step and multi-step calculation of three-dimensional ice shapes based entirely on FLUENT software, thereby realizing the calculation of ice shapes of the rotating cap in a supercooled large water droplet icing environment, and providing support for the airworthiness compliance verification of supercooled large water droplet icing.

[0059] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0060] Figure 1 This is a flow chart of a numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap in this specification, which specifically includes the following steps:

[0061] S1: The computational grid file is read into the FLUENT software, and the Reynolds-averaged Navier-Stokes (NS) equations in the steady-state rotating coordinate system are solved by the FLUENT software to obtain the air flow field. The turbulence model is calculated as the standard k-ε turbulence model, and is matched with the standard wall function.

[0062] S2: Calculate the characteristics of supercooled large water droplets impacting the rotating cap according to the air flow field, including the following steps:

[0063] S21: Based on FLUENT UDS, the water drop motion control equation under the Euler method is solved to obtain the motion trajectory of the water drop in the flow field. The water drop motion control equation under steady-state calculation is as follows:

[0064]

[0065] Where α is the water drop volume fraction, ρ d is the water drop density, V d is the relative velocity vector of the water drop, ρ a is the air density, N is the water droplet density, which indicates the number of water droplets per unit volume, and F d represents the air resistance of a single water droplet, and g is the gravitational acceleration vector.

[0066]

[0067] Among them, V a is the air relative velocity vector, C d is the water drop drag coefficient, and d is the water drop diameter.

[0068] Water drop drag coefficient C d The spherical drag coefficient C d,sphere and the disk drag coefficient C d,disk By weighted calculation:

[0069] C d =(1-ψ)C d,sphere +eC d,disk (4)

[0070] Here, ψ represents the additive coefficient.

[0071] N is solved by the number density equation:

[0072]

[0073] Among them, S bu The source term of the number density equation caused by the breakup of supercooled large water droplets can be calculated by the following formula:

[0074]

[0075] Among them, m is 0.2, T bu is the dimensionless droplet breakup time, d stab Indicates the diameter of the water drop after the water drop breaks.

[0076] S22: Calculate the local water collection coefficient β based on the solution of the water droplet motion equation. The formula is as follows:

[0077]

[0078] Among them, V dr is the relative velocity vector of the water drop, n is the unit normal vector of the wall microelement surface, α ∞ V is the volume fraction of the incoming water droplets, d,∞ is the speed of the incoming water droplets.

[0079] f m is the water drop mass loss coefficient, which indicates the water drop mass loss caused by the rebound and splashing of supercooled large water droplets. The calculation formula is as follows:

[0080]

[0081] Among them, m loss is the mass of water droplets lost due to rebound and splashing, m total represents the mass of water droplets collected on the wall without considering rebound splash, θ is the water drop impact angle, K L It is the judgment parameter for the rebound and splash of water droplets.

[0082] S3: According to the motion trajectory of the water droplet flow field, the FLUENT UDF is used to solve the icing thermodynamic model of the rotating parts. This model is developed based on the Messinger model. The icing thermodynamic model mainly includes the water film mass conservation equation, the water film energy conservation equation and the water film momentum equation.

[0083] Water film mass conservation equation:

[0084]

[0085] in, is the water mass flowing into the current control body from the adjacent control body; is the mass of the water droplet impact; is the mass of water flowing out of the current control volume; To control the quality of water in the body that freezes into ice; To control the quality of water evaporation in the body.

[0086] In order to facilitate the solution of the equation, the freezing coefficient f is introduced to indirectly represent the ice mass, which is defined as follows:

[0087]

[0088] Water film energy conservation equation:

[0089]

[0090] in, Total energy brought by overflow water inflow to adjacent control; The energy brought by the impact of water droplets; The heat released by freezing water into ice; is the aerodynamic heating amount; is the total energy carried away by the overflow water; The heat absorbed by the evaporation of water; The heat carried away by convection.

[0091] Water film momentum equation:

[0092]

[0093] The boundary conditions of the water film momentum equation are introduced, and the water film momentum equation is solved to obtain the distribution of the water film velocity along the thickness direction of the water film. Then, the water film velocity is integrated along the thickness direction of the water film and averaged to obtain the average velocity of the water film.

[0094]

[0095] Among them, μ d is the dynamic viscosity coefficient of the water drop, h is the water film thickness, P is the pressure, ω is the rotation velocity vector, r is the rotation radius vector, τ a is the air shear force on the water film.

[0096] After obtaining the average velocity of the water film, the total outflow mass of the overflow water can be expressed as:

[0097]

[0098] Among them, A j represents the area of ​​the water film outflow surface, n j Represents the surface normal vector of the water film outflow surface.

[0099] Combining equations (9), (10), (11), and (14), assuming that the temperature of the ice control body is 0°C and the initial water film thickness is 0, the ice mass is solved by iterative loop:

[0100] S4: Calculate the moving height h of the grid node at the icing boundary according to the calculation results of the icing mass ice and direction of movement.

[0101] Ice growth height h of the grid nodes at the ice boundary ice The calculation formula is as follows:

[0102]

[0103] in, represents the ice mass of the i-th common node mesh surface, n represents the number of common node mesh surfaces, ρ ice represents the freezing density, and Δt represents the freezing time step.

[0104] The moving direction of the mesh node is calculated by the average value of the surface normal vectors of the mesh with the same node:

[0105]

[0106] Among them, n node The vector representing the direction of movement of the grid node, n face,i Represents the face normal vector of the i-th common node mesh face.

[0107] For clear ice, the ice density is 917 kg / m 3 , the density of frost ice is calculated according to the following formula:

[0108]

[0109] S5: According to the ice growth height and movement direction, the diffusion smoothing method in the FLUENT dynamic mesh function is used to move the ice boundary to obtain the geometric shape after ice formation.

[0110] S6: Determine whether the engine rotary cap has reached the freezing time according to the current calculation time. If so, use the current calculation time as the final freezing time. If not, continue to execute the above steps.

[0111] If the calculated time does not reach the freezing time, it is necessary to output the boundary mesh file after the boundary movement through the FLUENT software, and use the FLUENT MESHING software to read the file to re-divide the calculation mesh; after the mesh division is completed, read the updated mesh file through the FLUENT software, repeat steps S1-S6, and enter the next step of freezing time calculation until the calculated time reaches the final freezing time.

[0112] Example:

[0113] According to the three-dimensional numerical simulation calculation method for supercooled large water droplets icing on a rotating cap proposed in this specification, a supercooled large water droplet icing experiment on a rotating cap was carried out in an icing wind tunnel using the rotating cap icing experimental conditions in Table 1. The experimental icing conditions are as follows: Figure 3 shown.

[0114] Figure 3 The freezing temperature of Exp1 in Figure (a) is relatively high, and the experimental ice shape is complex. The multi-step method is used for numerical simulation, and the time step is set to 60s.

[0115] and Figure 3 The freezing temperature of Exp4 in Figure (b) is low, and the experimental ice shape is relatively smooth. Accurate results can be obtained by using the single-step method for numerical simulation.

[0116] Figure 4 The geometric model of the rotating cap for numerical calculation is given, and the cap cone tip is chamfered.

[0117] Table 1 Rotating cap icing test conditions

[0118]

[0119] The ice shape verification results of Exp1 are as follows Figure 5 As shown in the figure, this condition is the freezing condition of supercooled large water droplets. At the tip of the cap cone, the difference between the numerical simulation results and the experiment is less than 15%, and a clear concave area is formed behind the tip of the cap cone, which is basically consistent with the experimental ice shape change trend. As the rotation radius increases, the ice shape thickness calculated by the numerical simulation is basically the same as the experimental results.

[0120] It is one of the recognized difficulties in the industry to simulate the uniformity of supercooled large water droplet cloud conditions in a ground wind tunnel. Since this experiment is the first supercooled large water droplet ice wind tunnel test conducted in China, it is limited by the experimental equipment and objective factors such as the gravity sedimentation of supercooled large water droplets. At present, it can only ensure that the water droplet cloud conditions near the tip of the rotating cap cone have a certain uniformity. According to the measurement results of the cloud field, the cloud conditions have good uniformity in the range of r / D<0.124. Therefore, Figure 5 The ice thickness near the inhomogeneous region is lower than the experimental results.

[0121] The ice shape verification results of Exp2 are as follows Figure 6As shown in the figure. Due to the obvious gravity sedimentation of supercooled large water droplets, the diameter of water droplets in the non-uniform area is relatively low, so it is more easily affected by the air flow field and deviates from the rotating cap surface. Therefore, the experimental ice thickness in this area is also relatively low. In the uniform area, the numerical calculation is in good agreement with the experimental results, and the ice thickness is basically the same. At the tip of the cap cone, the deviation between the numerical calculation results and the experiment is about 14.2%.

[0122] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap, characterized in that: include: Read the computational grid file into the numerical simulation software and determine the air flow field; According to the water drop motion control equation, the breakup of supercooled large water droplets during motion is considered, and the motion trajectory of supercooled large water droplets in the air flow field is obtained; at the same time, according to the water drop motion control equation, the mass loss of water droplets caused by rebound and splashing of supercooled large water droplets is considered, and the local water collection coefficient of the engine rotating cap is obtained; According to the motion trajectory of supercooled large water droplets in the air flow field and the local water collection coefficient of the engine rotating cap, a thermodynamic model of engine rotating cap ice formation is established, and the ice mass is obtained by solving the model. According to the ice mass, the moving height and moving direction of the ice boundary grid nodes are calculated; And the ice boundary is moved according to the moving height and moving direction to obtain the geometric shape after ice formation; It is determined whether the engine rotating cap has reached the freezing time according to the current calculation time. If so, the geometric shape after freezing corresponding to the current calculation time is used as the final ice shape; if not, the geometric shape after freezing is re-determined by re-reading the calculation grid file after the calculation grid is re-divided into the numerical simulation software until the freezing time is reached, and the geometric shape after freezing corresponding to the current calculation time is used as the final ice shape.

2. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1 is characterized in that: The step of obtaining the motion trajectory of supercooled large water droplets in the air flow field specifically comprises the following steps: The water drop drag coefficient is calculated by weighting the spherical drag coefficient and the disk drag coefficient; The air resistance of a single water droplet is obtained through the water droplet drag coefficient, water droplet diameter, air relative velocity vector, and water droplet relative velocity vector; Based on the change in the number of water droplets caused by the breakup of supercooled large water droplets, the water droplet number density equation is solved; The control equation of water drop motion under steady-state calculation is obtained from the air resistance of a single water drop, water drop number density, water drop relative velocity vector, air density, water drop density, water drop volume fraction and gravity acceleration vector. Based on FLUENT UDS, the water droplet motion control equation under the Euler method is solved to obtain the motion trajectory of supercooled large water droplets in the air flow field.

3. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1 is characterized in that: The method of establishing an engine rotary cap hood icing thermodynamic model and solving the model to obtain icing mass specifically includes the following steps: The momentum equation of the water film on the engine rotating cap is established based on the average velocity of the water film, the dynamic viscosity coefficient of the water droplets, the pressure gradient, the rotating velocity vector of the rotating cap, the water droplet density and the rotating radius vector of the rotating cap. The boundary conditions of the water film momentum equation are introduced, and the water film momentum equation is solved to obtain the distribution of the water film velocity along the thickness direction of the water film. Then integrate the water film velocity along the water film thickness direction and take the average to obtain the average velocity of the water film; The mass of water flowing out of the control body is calculated based on the average velocity of the water film, the area of ​​the water film outflow surface and the surface normal vector of the water film outflow surface; Establish the water film energy conservation equation of the engine rotating cap: the sum of the total energy brought by the overflow water from the adjacent control body into the current control body, the energy brought by the water droplets hitting the rotating cap, the heat released by the water freezing into ice, and the aerodynamic heating is equal to the sum of the total energy taken away by the overflow water from the current control body, the heat absorbed by the evaporation of water in the control body, and the heat taken away by the convective heat exchange in the control body; Establish the mass conservation equation of the water film on the engine rotating cap: the sum of the mass of water flowing into the current control body from the adjacent control body and the mass of water droplets hitting the rotating cap is equal to the sum of the mass of water flowing out of the control body, the mass of water frozen into ice in the control body, and the mass of water evaporated in the control body; When the temperature of the ice control body is 0℃ and the initial water film thickness is 0, the water film momentum equation, the water film mass conservation equation and the water film momentum conservation equation are combined to solve the ice mass through an iterative cycle.

4. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1 is characterized in that: The method of judging whether the engine rotary cap has reached the freezing time according to the current calculation time specifically includes the following steps: If the calculated time does not reach the freezing time, the boundary mesh file after the boundary movement needs to be output through the FLUENT software, and the file needs to be read by the FLUENT MESHING software to re-divide the calculation mesh; After the meshing is completed, the updated mesh file is read through the FLUENT software, and the geometric shape and time after freezing are repeatedly calculated until the calculated time reaches the freezing time.

5. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1 is characterized in that: The calculation of the moving height and moving direction of the grid nodes of the icing boundary specifically includes: The moving height of the icing boundary grid nodes is calculated based on the icing mass, icing density, icing time step and the number of icing grid surfaces with common nodes; The moving direction of the mesh node is obtained by calculating the average value of the surface normal vectors of the common node surface mesh.

6. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1, characterized in that: The step of moving the ice boundary according to the moving height and the moving direction to obtain the geometric shape after ice formation specifically includes: The diffusion smoothing method in the dynamic mesh function of FLUENT numerical simulation software is used to move the ice boundary and obtain the mesh geometry after ice formation.

7. The numerical simulation ice shape calculation method for supercooled large water droplets freezing on a rotating cap as claimed in claim 1 is characterized in that: The determining of the air flow field specifically includes: The air flow field is obtained by solving the Reynolds-averaged Navier-Stokes equations in a steady-state rotating coordinate system using FLUENT software.

8. A numerical simulation ice shape calculation system for supercooled large water droplets freezing on a rotating cap, characterized in that: include: An air flow field calculation module, used to determine the air flow field; The water drop impact characteristic calculation module is used to obtain the motion trajectory of the supercooled large water droplets in the air flow field according to the water drop motion control equation and consider the breakage of the supercooled large water droplets during the motion process; at the same time, according to the water drop motion control equation, the water drop mass loss caused by the rebound and splashing of the supercooled large water droplets is considered to obtain the local water collection coefficient of the engine rotating cap cover; The icing thermodynamic model calculation module is used to establish an icing thermodynamic model of the engine rotating cap according to the motion trajectory of the supercooled large water droplets in the air flow field and the local water collection coefficient of the engine rotating cap, and solve the model to obtain the icing mass; The icing shape calculation module is used to calculate the moving height and moving direction of the icing boundary grid nodes according to the icing mass; And the ice boundary is moved according to the moving height and moving direction to obtain the geometric shape after ice formation; The multi-step time determination module is used to determine whether the engine rotating cap has reached the freezing time according to the current calculation time. If so, the freezing geometric shape corresponding to the current calculation time is used as the final freezing ice shape; if not, the freezing geometric shape is re-determined by re-reading the calculation grid file after the calculation grid is re-divided in the numerical simulation software until the freezing time is reached, and the freezing geometric shape corresponding to the current calculation time is used as the final freezing ice shape.

9. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in any one of claims 1 to 7 is implemented.

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