Aircraft electrothermal deicing non-steady-state process prediction method, device and medium

Abstract

The present invention belongs to the technical field of electric deicing of aircraft and engines, and discloses a method, device and medium for predicting the non-steady-state process of electric deicing of aircraft, wherein the method first calculates the air flow field and the water droplet field, obtains the external convective heat transfer coefficient and the water droplet impact amount results, and provides external data for the non-steady-state simulation calculation of deicing. During the non-steady-state simulation calculation, the freezing / melting rate and temperature distribution are obtained through the coupled iteration of the exchange boundary, and the ice amount and overflow state are updated according to the freezing / melting rate and temperature distribution. In the coupled iteration of the exchange boundary, two calculation processes of overflow phase change and diversion are included. The calculation results of overflow phase change and diversion are respectively used as the boundary conditions for executing diversion and overflow phase change. The present invention can obtain the instantaneous change results of surface temperature and ice thickness during the deicing process, and provide a theoretical basis for deicing effect analysis and electric heating deicing strategy design.

Description

Technical Field

[0001] The present invention relates to the technical field of electric deicing of aircraft and engines, and more specifically, to a method, device and medium for predicting a non-steady-state process of electric deicing of aircraft. Background Art

[0002] Aircraft icing seriously threatens flight safety and requires certain icing protection methods to deal with it. The electric heating anti-icing / de-icing system has the characteristics of high heating efficiency, relatively simple structure, easy control and monitoring, and is an important development direction for future icing protection.

[0003] In the design and research of electrothermal anti-icing / deicing systems, it is challenging to conduct flight anti-icing and deicing compliance certification tests on aircraft under natural icing conditions. The electrothermal deicing effect of the wing skin is not only affected by flight conditions and meteorological parameters, but also by the heating and control laws of the electrothermal deicing system. Therefore, the electrothermal deicing process is a complex non-steady-state thermodynamic process involving multiple physical phenomena. Establishing a prediction model and method for the non-steady-state process of aircraft electrothermal deicing is of great significance to the design and verification of aircraft electrothermal deicing systems.

[0004] In the existing simulation models and algorithms of the electrothermal deicing process, there are few complete studies on the surface overflow water freezing-melting-ice shedding considering ice shedding. However, the influence of ice shedding on the non-steady-state process of electrothermal deicing is very important. The melting and detachment behavior of the ice layer during the heating process needs to be deeply explored and taken into account in the prediction of the deicing process. Summary of the invention

[0005] The present invention is provided to solve the above problems existing in the prior art. Therefore, a method, device and medium for predicting the non-steady-state process of aircraft electric heating deicing are needed, which takes into account the melting and separation behavior of the ice layer during the heating process in the prediction of the deicing process, thereby obtaining the instantaneous change results of the surface temperature and ice thickness during the deicing process, and providing a theoretical basis for the deicing effect analysis and the design of electric heating deicing strategy.

[0006] The present invention adopts the following technical solution:

[0007] According to a first aspect of the present invention, a method for predicting a non-steady-state process of electrothermal deicing of an aircraft is provided, the method comprising:

[0008] Step 1, according to the heat and mass transfer process on the surface of the object, establish a control body mass conservation equation and a control body energy conservation equation, solve the control body mass conservation equation and the control body energy conservation equation to obtain the deicing heat load of the control body;

[0009] Step 2, establish a solid wall heat conduction equation, use the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature, which provides a temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1;

[0010] Step 3, within a single time step, continuously and iteratively execute steps 1 and 2 to obtain the freezing or melting rate and the surface temperature under the time step;

[0011] Step 4, judging whether deicing occurs according to the deicing judgment criterion, and updating the ice thickness;

[0012] Step 5: When deicing occurs in the current time step, repeat steps 1 to 4 to calculate the freezing-melting-shedding process of the next time step, and finally obtain the changes of surface ice thickness and surface temperature over time during the entire electric deicing process.

[0013] Preferably, the control body mass conservation equation is expressed as:

[0014]

[0015] In the formula, and are the amount of water on the surface of the object flowing into and out of the control body due to overflow; is the mass flow rate of water impinging on the control volume; is the mass flow rate evaporated from the control volume; is the mass flow of frozen ice. When there is ice melting during the electric heating process, is negative.

[0016] Preferably, the control volume energy conservation equation is expressed as:

[0017]

[0018] In the formula, is the convective heat transfer heat flux density; The heat flux density for evaporative heat dissipation; The heat flux required to heat the collection water; is the heat flux density converted from the kinetic energy of water droplets; The heating heat flux density applied to the surface by heat conduction of the skin; and are the unit area enthalpy of overflow water flowing into and out of the control body respectively; It is the heat flow released by ice formation, which exists in the overflow ice during the cooling process of electric thermal deicing. When the electric thermal deicing is heated, the ice melts. Represents the heat flow absorbed by the melting of ice.

[0019] Preferably, the step 4, judging whether deicing occurs according to the deicing judgment basis and updating the ice thickness, comprises:

[0020] Establishing an ice shedding model as a basis for shedding judgment; wherein the ice shedding model includes a physical model and an empirical model;

[0021] The physical model indicates that ice accumulation on the surface of the heating zone is controlled by air shear force and ice adhesion force. When the resultant force of the air flow field acting on the ice accumulation surface is greater than the adhesion force between the ice accumulation and the surface, it is determined that the ice accumulation in the heating zone falls off.

[0022] The empirical model indicates that when the ratio between the water film length and the ice accumulation length in the heating zone is greater than a limit value, it is determined that the ice accumulation in the heating zone falls off from the structure surface.

[0023] Preferably, the ice shedding model is expressed as:

[0024]

[0025] Where: Ice-Shedding represents the comprehensive criterion for ice accretion and shedding, F τ F is the resultant force of the air flow field on the ice accumulation surface. adhesion Indicates the ice adhesion force, L f Indicates the water film length, L t Indicates the length of ice accumulation.

[0026] Preferably, the step 4, judging whether deicing occurs according to the deicing judgment basis and updating the ice thickness, further includes:

[0027] After the calculation reaches convergence in each time step, the mass mass_ice of the control volume and the freezing / melting rate m are obtained. so ;

[0028] According to the mass of ice on the control body mass_ice and the freezing / melting rate m so , determine the state of each heating zone in each time step; wherein the state includes an icing state and a non-icing state;

[0029] When the heating partition is in an iced state, the air shear force and adhesion force of the heating partition are integrated, and the water film length of the heating partition is calculated at the same time; based on the shedding judgment basis, the relative size of the air shear force and the ice accumulation adhesion force in the heating partition is judged, and / or the ratio between the water film length and the ice accumulation length is judged. If the shedding criterion is met, the ice falls off and the surface ice mass is reset to zero.

[0030] Preferably, according to the mass of ice mass_ice and the ice formation / melting rate mso , determine the state of each heating zone within each time step, including:

[0031] If mass_ice>0, m so <0, it is determined that the heating zone is in the first state, which indicates that ice is present on the surface, and the heating heat flow makes the surface in a two-phase state of ice melting, and there is a water film between the ice on the wall and the surface, and the ice adhesion force F of the control body adhesion =0;

[0032] If mass_ice>0, m so ≥0, it is determined that the heating zone is in the second state, and the second state indicates that ice is accumulated on the surface, the overflow water on the surface is frozen, and ice adhesion exists on the control body;

[0033] If mass_ice=0, m so <0, it is determined that the heating zone is in the third state, which means that there is no ice accumulation on the surface, and the heating heat flow makes the surface in a melting state, and the temperature T s >273.15K, the surface is in liquid phase, the adhesion force F of ice accumulation surface adhesion =0;

[0034] If mass_ice=0, m so =0, it is determined that the heating zone is in the fourth state, and the fourth state indicates that there is no ice accumulation on the surface, and the ice accumulation surface adhesion force F adhesion =0.

[0035] Preferably, based on the shedding judgment basis, the relative magnitude of the air shear force and the ice accumulation adhesion force in the heating zone is judged, and / or the ratio between the water film length and the ice accumulation length is judged. If the shedding criterion is met, the ice is shed and the surface ice mass is cleared, including:

[0036] First, the relative size of the air shear force and the ice accumulation adhesion force in the heating zone is determined. If the shedding criterion is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero. If the shedding criterion is not met, the ratio between the water film length and the ice accumulation length is determined again. If the judgment basis is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero.

[0037] According to a second aspect of the present invention, a device for predicting a non-steady-state process of electrothermal deicing of an aircraft is provided, the device comprising:

[0038] The overflow phase change module is configured as a circuit model building unit, and is configured to establish a control body mass conservation equation and a control body energy conservation equation according to the heat and mass transfer process on the surface of the object, and solve the control body mass conservation equation and the control body energy conservation equation to obtain the deicing heat load of the control body;

[0039] The heat conduction calculation module is configured to establish a solid wall heat conduction equation, take the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature, wherein the surface temperature provides a temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1;

[0040] The rate and temperature distribution calculation module is configured to make the overflow phase change module and the heat conduction calculation module iteratively perform calculation operations within a single time step to obtain the freezing or melting rate and surface temperature under the time step;

[0041] A shedding judgment module is configured to judge whether deicing occurs according to the deicing judgment basis and update the ice thickness;

[0042] The iterative calculation module is configured to control the overflow phase change module, the heat conduction calculation module, the rate and temperature distribution calculation module and the shedding judgment module to work when shedding occurs in the current time step, so as to calculate the freezing-melting-shedding process of the next time step, and finally obtain the changes of the surface ice thickness and the surface temperature with time in the whole electric thermal deicing process.

[0043] According to a third aspect of the present invention, there is provided a readable storage medium storing one or more programs, wherein the one or more programs can be executed by one or more processors to implement the method as described above.

[0044] The present invention has at least the following beneficial effects:

[0045] The present invention conducts physical modeling of the ice shedding phenomenon, introduces the shedding behavior of the ice layer during the heating process, and combines the icing-melting mathematical model in the electrothermal deicing process to establish a complete icing-melting-shedding model and calculation method for the electrothermal deicing system, which can obtain the instantaneous change results of the surface temperature and ice thickness during the deicing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram showing the physical phenomena occurring when the electric heating anti-icing system according to the prior art is in operation;

[0047] Figure 2 A flowchart of a method for predicting a non-steady-state process of electrothermal deicing of an aircraft according to an embodiment of the present invention is shown;

[0048] Figure 3 A schematic diagram of a physical deicing criterion according to an embodiment of the present invention is shown;

[0049] Figure 4 A schematic diagram of an empirical deicing criterion according to an embodiment of the present invention is shown;

[0050] Figure 5 A schematic diagram of an implementation process considering ice shedding according to an embodiment of the present invention is shown;

[0051] Figure 6 The cross-sectional structure of the protection zone heating assembly according to an embodiment of the present invention is shown;

[0052] Figure 7 A schematic diagram of the heating control rate of the Khalil experiment according to an embodiment of the present invention is shown;

[0053] Figure 8 The temperature rise curve at the position of the heating plate 3 according to the embodiment of the present invention is shown;

[0054] Fig. 9 A 2.5D wing model and heating zones according to an embodiment of the present invention are shown;

[0055] Fig.10 A schematic diagram of zoning and heating control rate according to an embodiment of the present invention is shown;

[0056] Fig.11 The thickness of ice accumulation at a typical time at the location of the heating zone 1 according to an embodiment of the present invention is shown;

[0057] Fig.12 The results of ice accumulation thickness and surface temperature variation over time of the heating zone 2 according to an embodiment of the present invention are shown;

[0058] Fig.13 The results of ice accumulation thickness and surface temperature variation over time of the heating zone 5 according to an embodiment of the present invention are shown;

[0059] Fig.14 A structural diagram of a device for predicting a non-steady-state process of electrothermal deicing of an aircraft according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments, but are not intended to limit the present invention. For the various steps described herein, if there is no necessity for a causal relationship between each other, the order in which they are described as examples herein should not be regarded as a limitation, and those skilled in the art should know that they can be adjusted in order, as long as the logic between them is not destroyed, resulting in the inability to implement the entire process.

[0061] The electrothermal deicing process is a multi-physics process involving air flow, water droplet impact, surface icing, surface melting during heating, ice shedding, etc. The specific physical phenomenon diagram is shown in the figure below. Figure 1 shown. Figure 1In the invention, a heating plate is arranged inside the object, and an air flow field will exist on the surface of the object. The object refers to the parts of the aircraft that require electric thermal deicing, such as wings. Under the action of the air flow field, supercooled water droplets will contact the surface of the object, and ice will be formed on the surface of the object at this time. Under the action of the heating plate, the ice on the surface will melt, such as ice cracks appearing from the inside of the ice, and the ice will melt to form a melt water film in contact with the surface of the object. Overflow water will be formed due to the contact between the outer surface of the ice and the moisture in the air or the melting of the surface. In the prior art, the entire process of surface overflow water freezing-melting-ice shedding considering ice shedding has not been studied, and the influence of ice shedding on the non-steady-state process of electric thermal deicing is very important. The melting and detachment behavior of the ice layer during the heating process needs to be deeply discussed and taken into account in the prediction of the deicing process. Therefore, how to take the melting and detachment behavior into account in the prediction of the deicing process during the heating process is the technical problem to be solved by the present invention.

[0062] Based on this, an embodiment of the present invention proposes a method for predicting a non-steady-state process of aircraft electrothermal deicing. Figure 2 The schematic diagram of a method for predicting the non-steady-state process of aircraft electrothermal deicing is shown in Figure 2. Figure 2 As shown in the figure, in the prediction of the unsteady-state process of electric thermal deicing considering deicing, the air flow field and water droplet field are first calculated to obtain the external convective heat transfer coefficient and the water droplet impact amount results, providing external data for the unsteady-state simulation calculation of deicing. During the unsteady-state simulation calculation, the freezing / melting rate and temperature distribution are obtained through the coupled iteration of the exchange boundary, and the freezing amount and overflow state are updated according to the freezing / melting rate and temperature distribution. In the coupled iteration of the exchange boundary, two calculation processes are included, namely overflow phase change and diversion. The calculation results of overflow phase change and diversion are used as the boundary conditions for executing diversion and overflow phase change, respectively, so as to calculate the freezing / melting rate and temperature distribution.

[0063] Specifically, the aircraft electrothermal deicing non-steady-state process prediction method includes the following steps:

[0064] Step 1: According to the heat and mass transfer process on the surface of the object, a control body mass conservation equation and a control body energy conservation equation are established, and the control body mass conservation equation and the control body energy conservation equation are solved to obtain the deicing heat load of the control body.

[0065] In this embodiment, step 1 realizes the surface overflow phase change simulation by solving the mass and energy conservation equations of ice formation / melting. The heat and mass transfer process of the surface is analyzed, the mass and energy conservation model of ice formation / melting is established and solved, and the deicing heat load of the surface control volume is obtained to provide an external thermal boundary for solving the solid wall heat conduction equation.

[0066] In some embodiments, the control volume mass conservation equation is:

[0067]

[0068] In the above formula: is the mass flow rate of water impinging on this control volume; is the mass flow rate evaporated from the control volume;

[0069] and The amount of water on the surface of the object flowing into and out of the control body due to overflow; is the mass flow of frozen ice. When there is ice melting during the electric heating process, is negative.

[0070] The energy conservation equation of the control volume is:

[0071]

[0072] In the above formula: is the convective heat transfer heat flux density; The heat flux density for evaporative heat dissipation; The heat flux required to heat the collection water; is the heat flux density converted from the kinetic energy of water droplets; The heating heat flux density applied to the surface by heat conduction of the skin; and are the unit area enthalpy of overflow water flowing into and out of the control body respectively; It is the heat flow released by ice formation, which exists in the overflow ice during the cooling process of electric thermal deicing. When the electric thermal deicing is heated, the ice melts. Represents the heat flow absorbed by the melting of ice.

[0073] Step 2, establish the solid wall heat conduction equation, use the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature. The surface temperature provides the temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1.

[0074] In this embodiment, step 2 is used to solve the solid wall heat conduction equation to obtain the surface temperature. In this calculation process, the outer surface heat flux boundary is loaded according to the deicing heat load obtained in step 2, and the electric heating heat flux density is provided according to the electric heating deicing control strategy. The surface temperature result obtained provides the temperature boundary for the overflow phase change simulation in step 1.

[0075] Step 3, within a single time step, continuously iteratively execute steps 1 and 2 to obtain the freezing or melting rate and surface temperature under the time step.

[0076] Step 4: determine whether deicing has occurred based on the deicing judgment criterion and update the ice thickness.

[0077] In some embodiments, the basis for judging the shedding in step 4 is described as follows:

[0078] The de-icing criterion combines two parts: one is the physical model and the other is the empirical model. The schematic diagrams of the two criteria are as follows: Figure 3 and Figure 4 As shown. The physical model and the empirical model are combined to form an ice shedding model as the basis for shedding judgment. The physical model means that the surface ice accumulation is mainly controlled by the air shear force and the ice adhesion force. When the air flow field acts on the ice surface, the resultant force F τ Greater than the ice adhesion force F between the ice and the surface adhesion When L is equal to the length of the water film, the ice in this area will fall off. The empirical model assumes that if the distance L between the length of the water film and the length of the ice f / L t When the ratio is greater than a certain limit value (the specific limit value can be further obtained through experimental data, and 80% is recommended in this embodiment), the accumulated ice will fall off from the surface of the structure. In general, the ice shedding model is as follows, and if any one of the items is met, it is considered that the ice in the area has fallen off.

[0079] The ice shedding model is expressed as:

[0080]

[0081] Where: Ice-Shedding represents the comprehensive criterion for ice accretion and shedding, F τ F is the resultant force of the air flow field on the ice accumulation surface. adhesion Indicates the ice adhesion force, L f Indicates the water film length, L t Indicates the length of ice accumulation.

[0082] In this embodiment, when using the ice shedding model to judge ice shedding, the relative sizes of the air shear force and the ice accumulation adhesion force in the heating zone can be judged first. If the shedding criterion is met, the ice is determined to have shed and the surface ice mass is cleared to zero. If the shedding criterion is not met, the ratio between the water film length and the ice accumulation length is judged again. If the judgment basis is met, the ice is determined to have shed and the surface ice mass is cleared to zero.

[0083] Of course, when using the ice shedding model to judge ice shedding, you can also first judge the ratio between the water film length and the ice accumulation length. If the judgment criteria are met, it is determined that the ice has fallen off and the surface ice mass is reset to zero; if the shedding criterion is not met, the relative size of the air shear force and the ice accumulation adhesion force in the heating zone is judged again. If the shedding criterion is met, it is determined that the ice has fallen off and the surface ice mass is reset to zero.

[0084] When using the ice shedding model to judge ice shedding, the ratio between the water film length and the ice accumulation length and the relative size of the air shear force and the ice accumulation adhesion force in the heating zone can also be judged at the same time. As long as any one of them is met, it is considered that the ice in the area has shed.

[0085] In some implementations, in step 4, judging whether deicing occurs according to the deicing judgment basis and updating the ice thickness are specifically described as follows:

[0086] Consider the implementation process of ice shedding as follows Figure 5 As shown. After reaching convergence, the mass mass_ice and the freezing / melting rate m of the frozen ice in the control volume are calculated in each time step. so (less than 0 means ice melting) to monitor the ice thickness h ice and the thickness of the ice-melting water film h waterfilm The calculation can be based on mass_ice and m so The discussion of these two physical quantities can intuitively represent the different states of each heating partition wall in each time step, which is convenient for the integral calculation of ice adhesion and ice removal judgment. The different states of the heating partition wall include four states, namely the first state, the second state, the third state and the fourth state.

[0087] 1) mass_ice>0, m so <0

[0088] This is the first state, where ice is accumulated on the surface, and the heating heat flow makes the surface in a two-phase state of ice melting, and there is a water film between the ice on the wall and the surface. The ice adhesion force F of this control body ad =0, recorded as part1, belongs to Figure 4 Medium f scope.

[0089] 2) mass_ice>0, m so ≥0

[0090] This is the second state, with ice accretion on the surface and frozen water overflowing the surface. This control body has ice accretion adhesion, and an ice accretion adhesion model needs to be introduced, which is recorded as part2.

[0091] 3) mass_ice = 0, m so <0

[0092] This is the third state, there is no ice accumulation on the surface, and the heating heat flow makes the surface in a melting state, the temperature T s >273.15K, the surface is in liquid phase, the adhesion force F of ice accumulation surface ad =0, recorded as part3, belongs to Figure 4 Medium f scope.

[0093] 4) mass_ice = 0, m so =0

[0094] This is the fourth state, there is no ice accumulation on the surface, and the adhesion force F ad =0, recorded as part4, belongs to Figure 4 Medium f scope.

[0095] Calculate the air shear force and adhesion force data of each wall control body. Traverse the wall control body, integrate the air shear force and adhesion force of each heating zone, and calculate the melting ice film L of each heating zone. f Finally, the ice shedding model is used to determine the relative size of the air shear force and the ice adhesion force in the partition, and the ratio between the water film area and the ice accumulation area. If the shedding criterion is met, the ice will fall off and the surface ice mass will be reset to zero. When the next time step is calculated, the initial value of the surface ice thickness is 0.

[0096] It should be noted that if the wing is a two-dimensional wing, the ratio between the water film length and the ice accumulation length is used. If it is a three-dimensional part, the water film length and the ice accumulation length can be replaced by the water film area and the ice accumulation area to improve the accuracy of the judgment.

[0097] In this embodiment, the mass of the frozen ice mass_ice and the freezing / melting rate m are controlled. so To determine the different states of each heating partition wall in each time step. Among them, the third and fourth states are unfrozen states, that is, there is no ice on the surface. At this time, it can be directly determined that the ice has fallen off and the surface ice mass is cleared. In the first state, the ice adhesion force F of the control body ad = 0, it can also be directly determined that the ice has fallen off and the surface ice mass is cleared. Therefore, only in the second state does it need to perform integral calculation of ice adhesion, and the other states can be directly judged, thereby saving part of the complex data calculation and improving the calculation efficiency.

[0098] Step 5: When deicing occurs in the current time step, repeat steps 1 to 4 to calculate the freezing-melting-shedding process of the next time step, and finally obtain the changes of surface ice thickness and surface temperature over time during the entire electric deicing process.

[0099] The following embodiments of the present invention will further illustrate the feasibility and advancement of the present invention in combination with two specific implementation cases.

[0100] Implementation Case 1: Simulation Verification

[0101] The NACA0012 airfoil structure is selected as the calculation model, and the chord length is 0.9144m. For verification, the calculation conditions are selected from the Khalil experimental environment conditions as shown in Table 1. The electric heating structure and the wing ply structure are combined to form an electric heating unit assembly. The electric heating ply structure in the protection zone is composed of four layers of materials. The physical properties of each layer of material in the protection zone are shown in Table 2. The heating assembly adopts a deicing method, such as Figure 6 The rubber layer within the protection range is set to 7 heating zones along the chord direction, and the heating control rate used is as follows: Figure 7 As shown, the heating heat flow setting is: the heating plate 4 is 0.775W / cm 2 , heating plates 3 and 5 are 1.55W / cm 2 , heating plates 1, 2, 6, 7 are 1.24W / cm 2 .

[0102] Table 1 Khalil experimental environmental conditions

[0103]

[0104] Table 2 Physical properties of materials in each layer of Khalil experimental protection area

[0105]

[0106]

[0107] The above electric heating simulation model considering ice shedding is calculated and solved, as shown in Figure 8 As shown, the temperature at the heating plate 3 position changes with time, and there is no obvious ice shedding during the calculation process. The calculation results are compared with the experimental measurement results, and the temperature change trends are similar, and the temperature error is within 6K, which shows the correctness of the present invention.

[0108] Implementation Case 2: Practical Application Case

[0109] For example Fig. 9 The non-steady-state process of electric heating deicing of the 2.5D airfoil shown in the figure is calculated, and there are 5 heating zones. The calculation conditions are shown in Table 3, and the heating control rate diagram is shown in Fig.10 shown.

[0110] Table 3 Calculation conditions

[0111]

[0112] Analysis of deicing results:

[0113] Take a time period during the de-icing cycle when ice shedding occurs and is easily observed in heating zone 1 for analysis. Fig.11As shown, a scatter plot of ice thickness and y coordinate at typical moments 94s, 95s, 103s and 127s was drawn. By comparing the calculations, it was found that at the 94th second, after a period of icing, the ice shape calculated using the deicing model and the non-deicing model was basically consistent. The ice thickness results calculated without considering the ice shedding model continued to increase from 95s to 127s. The results of the calculation considering the deicing model showed that ice shedding occurred at the 95th second. At this time, it was in the heating period of heating partition 1. Due to the heat conduction of the structure, the ice in this area melted and fell off. Considering the shedding model, the ice thickness calculated became 0, and the calculation result was reasonable. The ice shape was calculated again after 95s, and a heating cycle ended at 127s. After adding the ice shedding model at 95s, the mass of ice accumulated on the airfoil was reduced by 37% (the density of ice was taken as 917kg / m 3 ), after 127s of calculation, the mass of ice accumulated on the airfoil was reduced by 28%, indicating that the ice shedding model is of great significance for predicting the deicing time and studying the efficient electric heating deicing strategy.

[0114] Ice accretion thickness and surface temperature results:

[0115] Analysis of heating zone 2, such as Fig.12 As shown, the ice thickness, skin temperature, and heating plate heat flux density-time images are plotted. The maximum ice thickness at the heating zone 2 position is 0.1054 cm at 127 seconds, and the highest temperature is 278.3.K at the 4th second. The heating zone 2 is turned on from 0 to 4 seconds. During this period, there is no ice accumulation on the skin surface. The skin temperature quickly rises to above the freezing point. After 4 seconds, the heating plate is turned off and the skin temperature drops. The increase in skin temperature is basically only due to the activation of the heating plate at this position, and the adjacent heating plates have almost no effect on it. After 4 seconds, after the skin temperature drops to the freezing point, the surface is in a two-phase state of ice formation, and ice begins to form. The ice thickness increases, but the skin temperature remains at the freezing point and does not drop below 0°C, resulting in more serious icing. After a period of icing, the heating zone 2 works from 53 to 57 seconds and begins to de-ice. The calculated data shows that the skin temperature is still at 0℃ for a period of time after the heating starts, and the surface is in a two-phase state of melting ice. In the last 1s of the operation of the heating plate, the ice accumulation at this location is removed. It can be seen in the image that ice shedding has occurred, the ice thickness has become 0, and the temperature has risen to above 0℃. Ice shedding occurs when the heating plate is in the melting state, and the calculated results are reasonable. After 57s, the skin temperature quickly dropped to 0℃ and began to freeze, and the ice thickness continued to increase.

[0116] The calculation results of heating zones 3 and 4 are similar to those of heating zone 2. The difference is that since the amount of water impacting is not as large as that of heating zone 2, the ice thickness is smaller, and the ice is quickly removed when the second heating plate is turned on, and the skin temperature quickly rises to above 0°C. The area where heating zone 1 is located is an overflow area, which is mainly affected by the overflow water formed after the heating of heating zone 2 is turned on. The ice thickness is thinner and can be removed after heating starts at 98 seconds.

[0117] The anti-icing strategy is relatively reasonable. The surface temperature is greater than zero for a short time and the maximum temperature is not particularly high. The energy consumption is low while ensuring the effect of electric deicing. Since the ice thickness in the first two freezing cycles is thin, the ice can be removed quickly.

[0118] Analysis of heating zone 5, such as Fig.13 As shown, the ice thickness, skin temperature, and heating plate heat flux density-time images are plotted. The heating period of heating zone 5 is 98-103s. The maximum ice thickness of this zone is 0.0442cm at 97s, and the highest temperature is 283.3.K at 103s. Before the heating plate works, due to the small amount of impact water at the location of heating zone 5, the skin temperature is at the freezing point, the surface is in a two-phase state of ice, and the ice thickness increases, but the skin temperature has always been at the freezing point and has not dropped below 0℃, resulting in more serious icing. After the heating of heating zone 5 is turned on at 98s, due to the thin ice accumulation, the skin temperature is first at 0℃, and the surface is in a two-phase state of melting ice and solid-liquid coexistence, and then the ice accumulation is quickly completely removed, the ice accumulation thickness drops to 0, and the temperature rises to above 0℃ to reach a peak. After the heating plate stops working, the skin temperature slowly decreases. When the calculation stops at 127s, the temperature is still above 0℃, and there is no ice accumulation on the surface.

[0119] It can be seen that the anti-icing strategy is relatively reasonable. The maximum temperature is not particularly high, but because the amount of water impacting this position is small, the ice formation rate is slow, the ice accumulation is thin, and the ice can be removed quickly. While ensuring the effect of electric deicing, energy consumption can be reduced by reducing the heat flow of the heating plate.

[0120] The embodiment of the present invention also provides a device for predicting the non-steady-state process of aircraft electric thermal deicing. Fig.14 As shown, the device comprises:

[0121] The overflow phase change module 141 is configured as a circuit model building unit, and is configured to establish a control body mass conservation equation and a control body energy conservation equation according to the heat and mass transfer process on the surface of the object, and solve the control body mass conservation equation and the control body energy conservation equation to obtain the deicing heat load of the control body;

[0122] The heat conduction calculation module 142 is configured to establish a solid wall heat conduction equation, take the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature, and the surface temperature provides a temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1;

[0123] The rate and temperature distribution calculation module 143 is configured to make the overflow phase change module and the heat conduction calculation module iteratively perform calculation operations within a single time step to obtain the freezing or melting rate and the surface temperature under the time step;

[0124] The shedding judgment module 144 is configured to judge whether deicing occurs according to the deicing judgment basis and update the ice thickness;

[0125] The iterative calculation module 145 is configured to control the overflow phase change module, the heat conduction calculation module, the rate and temperature distribution calculation module and the shedding judgment module to work when shedding occurs in the current time step, so as to calculate the freezing-melting-shedding process of the next time step, and finally obtain the change of the surface ice thickness and the surface temperature with time during the entire electric thermal deicing process.

[0126] In some embodiments, the control volume mass conservation equation is expressed as:

[0127]

[0128] In the formula, and are the amount of water on the surface of the object flowing into and out of the control body due to overflow; is the mass flow rate of water impinging on the control volume; is the mass flow rate evaporated from the control volume; is the mass flow of frozen ice. When there is ice melting during the electric heating process, is negative.

[0129] In some embodiments, the control volume energy conservation equation is expressed as:

[0130]

[0131] In the formula, is the convective heat transfer heat flux density; The heat flux density for evaporative heat dissipation; The heat flux required to heat the collection water; is the heat flux density converted from the kinetic energy of water droplets; The heating heat flux density applied to the surface by heat conduction of the skin; and are the unit area enthalpy of overflow water flowing into and out of the control body respectively; It is the heat flow released by ice formation, which exists in the overflow ice during the cooling process of electric thermal deicing. When the electric thermal deicing is heated, the ice melts. Represents the heat flow absorbed by the melting of ice.

[0132] In some embodiments, the shedding judgment module is further configured to:

[0133] Establishing an ice shedding model as a basis for shedding judgment; wherein the ice shedding model includes a physical model and an empirical model;

[0134] The physical model indicates that ice accumulation on the surface of the heating zone is controlled by air shear force and ice adhesion force. When the resultant force of the air flow field acting on the ice accumulation surface is greater than the adhesion force between the ice accumulation and the surface, it is determined that the ice accumulation in the heating zone falls off.

[0135] The empirical model indicates that when the ratio between the water film length and the ice accumulation length in the heating zone is greater than a limit value, it is determined that the ice accumulation in the heating zone falls off from the structure surface.

[0136] In some embodiments, the ice shedding model is expressed as:

[0137]

[0138] Where: Ice-Shedding represents the comprehensive criterion for ice accretion and shedding, F τ F is the resultant force of the air flow field on the ice accumulation surface. adhesion Indicates the ice adhesion force, L f Indicates the water film length, L t Indicates the length of ice accumulation.

[0139] In some embodiments, the shedding judgment module is further configured to:

[0140] After the calculation reaches convergence in each time step, the mass mass_ice of the control volume and the freezing / melting rate m are obtained. so ;

[0141] According to the mass of ice on the control body mass_ice and the freezing / melting rate m so , determine the state of each heating zone in each time step; wherein the state includes an icing state and a non-icing state;

[0142] When the heating partition is in an iced state, the air shear force and adhesion force of the heating partition are integrated, and the water film length of the heating partition is calculated at the same time; based on the shedding judgment basis, the relative size of the air shear force and the ice accumulation adhesion force in the heating partition is judged, and / or the ratio between the water film length and the ice accumulation length is judged. If the shedding criterion is met, the ice falls off and the surface ice mass is reset to zero.

[0143] In some embodiments, the shedding judgment module is further configured to:

[0144] If mass_ice>0, m so <0, it is determined that the heating zone is in the first state, which indicates that ice is present on the surface, and the heating heat flow makes the surface in a two-phase state of ice melting, and there is a water film between the ice on the wall and the surface, and the ice adhesion force F of the control body adhesion =0;

[0145] If mass_ice>0, m so ≥0, it is determined that the heating zone is in the second state, and the second state indicates that ice is accumulated on the surface, the overflow water on the surface is frozen, and ice adhesion exists on the control body;

[0146] If mass_ice=0, m so <0, it is determined that the heating zone is in the third state, which means that there is no ice accumulation on the surface, and the heating heat flow makes the surface in a melting state, and the temperature T s >273.15K, the surface is in liquid phase, the adhesion force F of ice accumulation surface adhesion =0;

[0147] If mass_ice=0, m so =0, it is determined that the heating zone is in the fourth state, and the fourth state indicates that there is no ice accumulation on the surface, and the ice accumulation surface adhesion force F adhesion =0.

[0148] In some embodiments, the shedding judgment module is further configured to:

[0149] First, the relative size of the air shear force and the ice accumulation adhesion force in the heating zone is determined. If the shedding criterion is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero. If the shedding criterion is not met, the ratio between the water film length and the ice accumulation length is determined again. If the judgment basis is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero.

[0150] It should be noted that the device structure described in this embodiment and the method described previously belong to the same technical concept, and achieve the same technical effect through the same principle, which will not be repeated here.

[0151] An embodiment of the present invention further provides a readable storage medium, which stores one or more programs. The one or more programs can be executed by one or more processors to implement the method described in any of the above embodiments.

[0152] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for predicting the non-steady-state process of aircraft electrothermal deicing, characterized in that: The method comprises: Step 1, according to the heat and mass transfer process on the surface of the object, establish a control body mass conservation equation and a control body energy conservation equation, solve the control body mass conservation equation and the control body energy conservation equation to obtain the deicing heat load of the control body; Step 2, establish a solid wall heat conduction equation, use the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature, which provides a temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1; Step 3, within a single time step, continuously and iteratively execute steps 1 and 2 to obtain the freezing or melting rate and the surface temperature under the time step; Step 4, judging whether deicing occurs according to the deicing judgment criterion, and updating the ice thickness; Step 5: When deicing occurs in the current time step, repeat steps 1 to 4 to calculate the freezing-melting-shedding process of the next time step, and finally obtain the changes of surface ice thickness and surface temperature over time during the entire electric deicing process.

2. The method according to claim 1, characterized in that The control volume mass conservation equation is expressed as: In the formula, and are the amount of water on the surface of the object flowing into and out of the control body due to overflow; is the mass flow rate of water impinging on the control volume; is the mass flow rate evaporated from the control volume; is the mass flow of frozen ice. When there is ice melting during the electric heating process, is negative.

3. The method according to claim 1, characterized in that The control volume energy conservation equation is expressed as: In the formula, is the convective heat transfer heat flux; The heat flux density for evaporative heat dissipation; The heat flux required to heat the collection water; is the heat flux density converted from the kinetic energy of water droplets; The heating heat flux density applied to the surface by heat conduction of the skin; and are the unit area enthalpy of overflow water flowing into and out of the control body respectively; It is the heat flow released by ice formation, which exists in the overflow ice during the cooling process of electric thermal deicing. When the electric thermal deicing is heated, the ice melts. Represents the heat flow absorbed by the melting of ice.

4. The method according to claim 1, characterized in that: The step 4, judging whether deicing occurs according to the deicing judgment criterion and updating the ice thickness, comprises: Establishing an ice shedding model as a basis for shedding judgment; wherein the ice shedding model includes a physical model and an empirical model; The physical model indicates that ice accumulation on the surface of the heating zone is controlled by air shear force and ice adhesion force. When the resultant force of the air flow field acting on the ice accumulation surface is greater than the adhesion force between the ice accumulation and the surface, it is determined that the ice accumulation in the heating zone falls off. The empirical model indicates that when the ratio between the water film length and the ice accumulation length in the heating zone is greater than a limit value, it is determined that the ice accumulation in the heating zone falls off from the structure surface.

5. The method according to claim 4, characterized in that The ice shedding model is expressed as: Where: Ice-Shedding represents the comprehensive criterion for ice accretion and shedding, F τ F is the resultant force of the air flow field on the ice accumulation surface. adhesion Indicates the ice adhesion force, L f Indicates the water film length, L t Indicates the length of ice accumulation.

6. The method according to claim 4, characterized in that The step 4, judging whether deicing has occurred according to the deicing judgment criterion and updating the ice thickness, also includes: After the calculation reaches convergence in each time step, the mass mass_ice of the control volume and the freezing / melting rate m are obtained. so ; According to the mass of ice on the control body mass_ice and the freezing / melting rate m so , determine the state of each heating zone in each time step; wherein the state includes an icing state and a non-icing state; When the heating partition is in an iced state, the air shear force and adhesion force of the heating partition are integrated, and the water film length of the heating partition is calculated at the same time; based on the shedding judgment basis, the relative size of the air shear force and the ice accumulation adhesion force in the heating partition is judged, and / or the ratio between the water film length and the ice accumulation length is judged. If the shedding criterion is met, the ice falls off and the surface ice mass is reset to zero.

7. The method according to claim 6, characterized in that According to the mass of ice on the control body mass_ice and the freezing / melting rate m so , determine the state of each heating zone within each time step, including: If mass_ice>0, m so <0, it is determined that the heating zone is in the first state, which indicates that ice is present on the surface, and the heating heat flow makes the surface in a two-phase state of ice melting, and there is a water film between the ice on the wall and the surface, and the ice adhesion force F of the control body adhesion =0; If mass_ice>0, m so ≥0, it is determined that the heating zone is in the second state, and the second state indicates that ice is accumulated on the surface, the overflow water on the surface is frozen, and ice adhesion exists on the control body; If mass_ice=0, m so <0, it is determined that the heating zone is in the third state, which means that there is no ice accumulation on the surface, and the heating heat flow makes the surface in a melting state, and the temperature T s >273.15K, the surface is in liquid phase, the adhesion force F of ice accumulation surface adhesion =0; If mass_ice=0, m so =0, it is determined that the heating zone is in the fourth state, and the fourth state indicates that there is no ice accumulation on the surface, and the ice accumulation surface adhesion force F adhesion =0.

8. The method according to claim 6, characterized in that Based on the shedding judgment basis, the relative magnitude of the air shear force and the ice accumulation adhesion force in the heating zone is judged, and / or the ratio between the water film length and the ice accumulation length is judged. If the shedding criterion is met, the ice is shed and the surface ice mass is cleared, including: First, the relative size of the air shear force and the ice accumulation adhesion force in the heating zone is determined. If the shedding criterion is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero. If the shedding criterion is not met, the ratio between the water film length and the ice accumulation length is determined again. If the judgment basis is met, it is determined that the ice has fallen off and the surface ice mass is cleared to zero.

9. A device for predicting the non-steady-state process of aircraft electrothermal deicing, characterized in that: The device comprises: The overflow phase change module is configured as a circuit model building unit, and is configured to establish a control body mass conservation equation and a control body energy conservation equation according to the heat and mass transfer process on the surface of the object, and solve the control body mass conservation equation and the control body energy conservation equation to obtain the deicing heat load of the control body; The heat conduction calculation module is configured to establish a solid wall heat conduction equation, take the deicing heat load of the control body as the external boundary, and provide the electric heating heat flux density according to the electric heating deicing control strategy to obtain the surface temperature, wherein the surface temperature provides a temperature boundary for solving the control body mass conservation equation and the control body energy conservation equation in step 1; The rate and temperature distribution calculation module is configured to make the overflow phase change module and the heat conduction calculation module iteratively perform calculation operations within a single time step to obtain the freezing or melting rate and surface temperature under the time step; A shedding judgment module is configured to judge whether deicing occurs according to the deicing judgment basis and update the ice thickness; The iterative calculation module is configured to control the overflow phase change module, the heat conduction calculation module, the rate and temperature distribution calculation module and the shedding judgment module to work when shedding occurs in the current time step, so as to calculate the freezing-melting-shedding process of the next time step, and finally obtain the changes of the surface ice thickness and the surface temperature with time in the whole electric thermal deicing process. 10 . A non-transitory computer-readable storage medium storing instructions, which, when executed by a processor, perform the method according to claim 1 .

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