A method for verifying the strength of a hydrogen storage buoy of a hydrogen energy seaplane under impact

Abstract

The invention relates to a strength verification method for a hydrogen storage buoy of a hydrogen energy seaplane under impact, belongs to the technical field of impact strength verification methods, solves the problem that the aircraft structure verification method in the prior art does not consider the water surface impact, and comprises: step S1, obtaining the design parameters of the hydrogen storage buoy of the hydrogen energy seaplane, calculating the impact load, and obtaining the water entry impact load of the hydrogen storage buoy; step S2, establishing a finite element model of the hydrogen storage buoy; step S3, performing unstructured grid division on the finite element model of the hydrogen storage buoy; step S4, setting loads and boundary conditions based on the obtained water entry impact load of the hydrogen storage buoy; step S5, submitting the set loads and boundary conditions to perform finite element calculation to obtain the load result of the hydrogen storage buoy, and judging whether the hydrogen storage buoy can work safely. If it can work safely, the parameter design of the hydrogen storage buoy meets the requirements and subsequent production and manufacturing can be carried out, otherwise, returning to step S1.

Description

Technical Field

[0001] The present invention relates to the technical field of impact strength verification methods, and more specifically, to a strength verification method for a hydrogen storage buoy of a hydrogen energy seaplane under impact. Background Art

[0002] A seaplane refers to a multifunctional special aircraft that can take off and land on the water surface. The surface load refers to the load caused by the impact between the aircraft and the water surface during the seaplane's takeoff and landing. The hydrogen storage buoy is designed for hydrogen-powered seaplanes, taking into account the functions of taking off and landing on the water surface as well as hydrogen storage. The hydrogen storage buoy structure directly bears the impact load of the water surface during the seaplane's takeoff and landing on the water surface. In order to ensure the reliability of the structure, there is a need in this technical field to use reasonable means to calculate and verify the impact load of the buoy when the seaplane lands on the water surface.

[0003] The Chinese invention patent application, publication number CN117371293A, titled "A method for assessing damage to aircraft structures after multiple impacts", discloses a method for assessing damage to aircraft structures after impact. However, this method is for conventional impacts on aircraft structures and does not take into account the impact on the aircraft structure during takeoff and landing on the water.

[0004] The Chinese invention patent application, publication number CN115809512A, titled "Impact Strength Analysis Method for Aircraft Landing Gear Retraction and Extension Mechanism Locking Strut Limiting Boss", discloses a method for analyzing the impact loads on an aircraft landing gear structure when it is in contact with the ground. However, it does not involve a strength verification method for the impact of water on an aircraft structure, especially the buoy of a seaplane.

[0005] At present, in the technical field, there is a lack of a complete strength verification method specifically for seaplane-carrying buoys. Since hydrogen storage buoys have the function of storing hydrogen, in order to avoid the risk of hydrogen leakage caused by impact, more complete impact load evaluation and strength verification are required than ordinary buoys. The difficulty in this evaluation and verification lies in the fact that when simulating the impact load during landing on the water surface, the water surface impact is difficult to model, and the conventional fluid-solid coupling method is too cumbersome and requires a large amount of calculation. Therefore, a method is needed that can accurately and effectively calculate the impact load and verification of the hydrogen storage buoy when the seaplane lands on the water surface, and has a small amount of calculation. Summary of the invention

[0006] In order to solve the above problems, an embodiment of the present invention provides a method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact.

[0007] According to an embodiment of the present invention, a method for verifying the strength of a hydrogen storage buoy of a hydrogen energy seaplane under impact is provided, comprising:

[0008] Step S1, obtaining design parameters of a hydrogen storage buoy of a hydrogen energy seaplane, calculating an impact load on the hydrogen storage buoy of the hydrogen energy seaplane, and obtaining an impact load of the hydrogen storage buoy upon entry into water;

[0009] Step S2, establishing a finite element model of the hydrogen storage buoy based on the design parameters of the hydrogen storage buoy;

[0010] Step S3, performing unstructured meshing on the finite element model of the hydrogen storage buoy;

[0011] Step S4, setting loads and boundary conditions based on the obtained water entry impact load of the hydrogen storage buoy;

[0012] Step S5, based on the set load and boundary conditions, finite element calculation is performed to obtain the load result of the hydrogen storage buoy, and whether the hydrogen storage buoy can work safely is determined. If it can work safely, the design parameters of the hydrogen storage buoy meet the requirements, and the output is performed for subsequent production and manufacturing. Otherwise, the design parameters of the hydrogen storage buoy are optimized and the process returns to step S1;

[0013] Wherein step S1 specifically includes:

[0014] Step S1.1, obtaining design parameters of a hydrogen storage buoy of a hydrogen energy seaplane;

[0015] Step S1.2, simplify the structure of the hydrogen storage buoy to obtain a wedge-shaped body, and use the design parameters of the hydrogen storage buoy as the parameters of the wedge-shaped body for subsequent processing to obtain the actual wetted half-width of the wedge-shaped body: , the density of water ;

[0016] Step S1.3, calculate the impact load of the wedge-shaped body to obtain the maximum water entry impact pressure value of the wedge-shaped body, and use it as the water entry impact load of the hydrogen storage buoy.

[0017] Optionally, the step S1.3 further comprises:

[0018] The expression of the impact pressure on the wedge when entering the water is:

[0019]

[0020] in, is atmospheric pressure, represents the impact pressure of water on the wedge, represents the velocity potential function of the wedge, Indicates time;

[0021]

[0022] in, is a calculated variable;

[0023] Get the wedge in The impact of the moment sinks to depth

[0024]

[0025] in, represents the series coefficient, Indicates the number of times,

[0026]

[0027]

[0028] in, To calculate the variable, The wedge is measured at The speed of the moment;

[0029] When the wedge enters the water, the part of the water surface adjacent to the wedge that rises above the still water surface is the raised water surface. The impact load on the wedge from the root of the raised water surface is the largest, and the calculation results are:

[0030]

[0031] Among them, ignore ,get ,

[0032] The maximum water impact pressure value of the hydrogen storage buoy is Output and save as the water entry impact load of the wedge.

[0033] Optionally, the step S4 specifically includes:

[0034] The load settings include: The load form is a uniform load, the load position is the V-shaped bottom surface of the hydrogen storage buoy, and the load direction is perpendicular to the V-shaped bottom surface;

[0035] The setting of boundary conditions includes constraining the z-direction translational freedom of the top of the hydrogen storage buoy.

[0036] A method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact provided in an embodiment of the present invention can accurately calculate the impact load on the hydrogen storage buoy during the seaplane's water landing process. By combining the verification process provided subsequently, a preliminary strength verification can be performed only by the explicit finite element method, and the amount of calculation is significantly reduced, providing a good safety assessment and guarantee for the application of hydrogen storage buoys in seaplanes. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the drawings. The drawings are schematic and should not be understood as limiting the present invention in any way. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 A flow chart of a hydrogen storage buoy design process for a hydrogen energy seaplane using a method for verifying the strength of the hydrogen storage buoy under impact provided in accordance with an embodiment of the present invention.

[0039] Figure 2 A schematic cross-sectional view of a hydrogen storage buoy in an embodiment of a method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact provided in accordance with an embodiment of the present invention.

[0040] Figure 3 In an embodiment of a method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact provided in accordance with an embodiment of the present invention, the hydrogen storage buoy is simplified into a schematic diagram of a wedge-shaped body impacting the water surface.

[0041] Figure 4 A schematic diagram of the initial moment before a hydrogen storage buoy touches water in an embodiment of a method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact provided in accordance with an embodiment of the present invention.

[0042] Figure 5 A schematic diagram of the load and boundary condition settings of a hydrogen storage buoy in an embodiment of a method for verifying the strength of a hydrogen storage buoy of a hydrogen-powered seaplane under impact provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0044] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clearly expressed, the technical solutions of the present invention will be fully described below with reference to the accompanying drawings.

[0046] Explanation of symbols:

[0047] The mass per unit length of the wedge;

[0048] The slope angle of the wedge;

[0049] The vertical descent speed of the wedge immediately before it hits the water;

[0050] The wedge-shaped body impacts and sinks to a depth below the surface of the water;

[0051] The wedge sinks to a depth of The vertical descent speed corresponding to ;

[0052] half-width of still water surface;

[0053] Actual infiltration half-width;

[0054] Velocity potential function of a wedge;

[0055] Coordinates along the width direction of the cross section of the hydrogen storage buoy;

[0056] time;

[0057] Vertical coordinates within the cross section of the hydrogen storage buoy;

[0058] The component velocity of the water particle along the normal direction of the outer surface of the wedge;

[0059] Density of water;

[0060] The semi-infinite entire flow field bounded by the free surface of the water;

[0061] All boundaries of the entire flow field;

[0062] The direction vector of the normal direction of the outer surface of the wedge;

[0063] Additional quality;

[0064] The wedge measured at The speed of the moment;

[0065] Atmospheric pressure;

[0066] The impact pressure of the water on the wedge;

[0067] The vertical velocity of a water particle perpendicular to the horizontal plane;

[0068] Amount of water surface rise;

[0069] The amount of water surface bulge between the highest position of the water free surface and the bottom of the wedge;

[0070] series coefficient;

[0071] series coefficient;

[0072] The wedge The impact of the moment sinks deep;

[0073] frequency;

[0074] Calculate variables;

[0075] of Power;

[0076] Gamma function;

[0077] Calculate variables;

[0078] Minimum impact pressure value;

[0079] Maximum shock pressure value.

[0080] refer to Figure 1 , shows a flow chart of the design process of a hydrogen storage buoy according to a method for verifying the strength of a hydrogen storage buoy of a hydrogen energy seaplane under impact provided by an embodiment of the present invention. Figure 2 The impact load calculation and strength verification of the hydrogen storage buoy with the cross-sectional structure shown are carried out.

[0081] Step S1, obtaining design parameters of the hydrogen storage buoy of the hydrogen energy seaplane, calculating the impact load of the hydrogen storage buoy of the hydrogen energy seaplane, and obtaining the water entry impact load of the hydrogen storage buoy. Figure 1 , this step specifically includes the following steps.

[0082] Step S1.1, obtain the design parameters of the hydrogen storage buoy. The cross-sectional shape of the hydrogen storage buoy is as follows: Figure 1 The structure and related design parameters of the hydrogen storage buoy are obtained, and the mass per unit length of the hydrogen storage buoy, the inclined rise angle of the hydrogen storage buoy, the instantaneous vertical descent speed of the hydrogen storage buoy before it touches the water, the vertical descent speed corresponding to the hydrogen storage buoy when it hits a certain sinking depth, and the half width of the still water surface are obtained. The actual infiltration half width is The vertical descent speed is the speed in the direction perpendicular to the horizontal plane.

[0083] Step S1.2, simplifying the structure of the hydrogen storage buoy to obtain a wedge-shaped body. The cross section of the hydrogen storage buoy processed in this embodiment is as follows: Figure 2 As shown, the cross-sectional shape is simplified to a V-shaped wedge, that is, the bilge of the hydrogen storage buoy is ignored and the surface is assumed to be smooth. The design parameters of the hydrogen storage buoy obtained in the previous step S1.1 are used as the parameters of the wedge for subsequent processing, and the mass per unit length of the wedge is obtained as , the slope angle of the wedge is , the vertical descent speed of the wedge at the initial moment before it touches the water is , the wedge sinks to a depth of The corresponding vertical descent speed is , the half-width of the still water surface is The actual infiltration half width is . See Figure 3 , showing a schematic diagram of the hydrogen storage buoy impacting the water surface after being simplified into a wedge-shaped body.

[0084] Step S1.3, impact load calculation, using the obtained design parameters to calculate the impact load of the wedge, and using the maximum water entry impact pressure value of the wedge as the water entry impact load of the hydrogen storage buoy. The specific process of this step is as follows.

[0085] Assuming that water is an ideal, incompressible fluid, and the flow of the hydrogen storage buoy after entering the water is irrotational, the boundary conditions satisfied by the flow field of the wedge-shaped body of the hydrogen storage buoy after impacting the water can conform to the Laplace equation, which is expressed as:

[0086] (1)

[0087] in, represents the velocity potential function of the wedge, represents the coordinates along the width direction of the cross section of the hydrogen storage buoy, Indicates time, Represents the vertical coordinate within the cross section of the hydrogen storage buoy.

[0088] The boundary conditions that must be satisfied for the surface of the wedge to be wetted by water are:

[0089] (2)

[0090] in, It represents the velocity component of the water particle along the normal direction of the outer surface of the wedge, and the direction of the velocity component points to the flow field. The water particle is the water particle in the water part attached to the surface of the wedge.

[0091] The initial conditions for the impact of the wedge into the water are that the velocity potential of the wedge is zero and the horizontal plane is a free surface without water bulge (i.e., ignoring the ripples that may appear on the water surface and considering it as completely horizontal), as shown in Figure 3 As shown. According to the velocity potential function, the additional mass can be obtained , expressed as:

[0092] (3)

[0093] in, is the density of water; is the semi-infinite entire flow field bounded by the free surface of water; are all boundaries of the entire flow field, The direction vector representing the normal direction of the outer surface of the wedge, represents the velocity of the wedge. The above additional mass It refers to the mass of water attached to the surface of the wedge when it hits the water surface at high speed. This phenomenon of water attached to the surface of the wedge increases the effective mass of the object, causing the object to generate a greater impact force when it interacts with the water surface. Attached to the surface of the wedge, so this part of the water particles has the same speed as the wedge. Can store data for evaluating impact acceleration and water impact loads.

[0094] Step S1.3.2, the expression of the impact pressure on the wedge when entering the water can be obtained by using the Bernoulli equation without considering the influence of weight:

[0095] (4)

[0096] in, is atmospheric pressure, Represents the impact pressure of water on the wedge.

[0097] See also Figure 3 The schematic diagram of the wedge-shaped body hitting the water surface is shown in the figure. Further calculation is performed according to the Von Karman linear theory, taking into account the effect of the water surface bulge at the free surface of the wedge-shaped body entering the water, and using a width of 2 Approximate actual wetted half-width of potential flow around a two-dimensional flat plate . So on the free surface The vertical velocity of the water particle at a position perpendicular to the horizontal plane It can be expressed as

[0098] (5).

[0099] After the wedge hits the water surface, the height difference between the highest point of the water's free surface and the lowest point of the wedge's cross section is the water surface bulge. ,as follows

[0100] (6).

[0101] Wet half width As a parameter variable, , , the water surface uplift can be obtained The expression is:

[0102] (7)

[0103] in,

[0104] (8).

[0105] in, is a calculated variable.

[0106] When the water point When the water surface reaches the wedge surface at The vertical coordinate at the cross-sectional shape of the wedge is The ordinates at the same place are the same, that is:

[0107] (9)

[0108] in, Indicates the amount of water surface bulge where the water free surface contacts the wedge.

[0109] Since at this time, the water surface The vertical coordinate at the cross-sectional shape of the wedge is The ordinates at the same position are consistent, and the shape of the wedge can be expressed by the following series:

[0110] (10)

[0111] And among them,

[0112] (11)

[0113] in, represents the series coefficient, represents the series coefficient, express of Power, express of Power, Indicates the number of times.

[0114] By comparing the coefficients, we can get the series coefficients. The expression is:

[0115] (12)

[0116] in, represents the gamma function.

[0117] Then we can get the wedge The impact of the moment sinks to depth

[0118] (13)

[0119] in

[0120] (14).

[0121] The velocity potential of the wedge Substituting into the above formula (4), the impact force acting on a point on the cross section of the wedge can be expressed as:

[0122] (15)

[0123] in,

[0124] (16)

[0125] (17)

[0126] (18)

[0127] in, is the calculated variable.

[0128] For any impact instant, Department, is the minimum value, and substituting it into the above formula (15) we can get:

[0129] (19)

[0130] in, Indicates the minimum impact pressure value.

[0131] exist This is the splash root at the root of the raised water surface and also the bifurcation point of the streamline cluster. At this point, the impact pressure of the root of the raised water surface on the wedge is the largest. Substituting it into the above formula (15) yields:

[0132] (20)

[0133] Among them, ignore ,available See also Figure 3 The raised water surface is the part of the water surface adjacent to the wedge-shaped body that rises above the still water surface when the wedge-shaped body enters the water.

[0134] The obtained The water entry impact load of the wedge-shaped body (ie, the hydrogen storage buoy) is output and saved for subsequent processing.

[0135] refer to Figure 1 After obtaining the water impact load of the hydrogen storage buoy from step S1, simulation verification can be performed in combination with finite element technology. Next, the finite element analysis pre-processing of the hydrogen storage buoy is performed, including modeling, unstructured meshing, and load and boundary condition settings.

[0136] Step S2, establishing a finite element model of the hydrogen storage buoy based on the design parameters of the hydrogen storage buoy.

[0137] Step S3, assigning material attributes to the hydrogen storage buoy finite element model and performing unstructured meshing. The meshing adopts unstructured mesh, i.e., tetrahedral mesh, and the mesh size is based on the minimum global mesh.

[0138] Step S4, based on the obtained water entry impact load of the hydrogen storage buoy, setting the load and boundary conditions. The load setting includes: the load is based on the water entry impact load of the hydrogen storage buoy obtained in step S1. is a fixed value, the load form is a uniform load, and the time parameters are set. For example, the load loading time can be set to 0.2s, the load duration can be set to 0.5s, and the load unloading time can be set to 0.1s. Figure 4 As shown, the setting of boundary conditions and loads includes that the top of the hydrogen storage buoy adopts constrained z-direction translational freedom, the load arrangement position is the V-shaped bottom surface of the hydrogen storage buoy as shown in the figure, the load direction is the direction perpendicular to the V-shaped bottom surface, and the load magnitude is the water entry impact load of the hydrogen storage buoy obtained from step S1.

[0139] Step S5, the set load and boundary conditions are subjected to finite element calculation to obtain the load results of the hydrogen storage buoy, and to determine whether the hydrogen storage buoy can work safely. If it can work safely, the parameter design of the hydrogen storage buoy meets the requirements and can be subsequently manufactured. Otherwise, the design parameters of the hydrogen storage buoy are optimized and the process returns to step S1. The load and boundary conditions set above are submitted to finite element calculation to obtain the load results of the hydrogen storage buoy and to perform impact dynamics verification. According to the verification results, the hydrogen storage buoy is moved at a speed of The maximum impact load of the impact on the water surface is compared with the preset load threshold that the hydrogen storage buoy can withstand to determine whether the hydrogen storage buoy can work safely in this case. If it can work safely, the parameter design of the hydrogen storage buoy meets the requirements and can be subsequently manufactured; if it cannot work safely, return to step S1 to redesign the parameters.

[0140] To determine whether the hydrogen storage buoy can work safely in this case, analyze the stress cloud diagram of the hydrogen storage buoy after being loaded, analyze the maximum force position and the maximum stress value, and determine whether the design meets the requirements by comparing the strength limit of the material.

[0141] All the above optional technical solutions can be arbitrarily combined to form optional embodiments of the present application, which will not be described one by one here.

[0142] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0143] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for verifying the strength of a hydrogen storage buoy of a hydrogen energy seaplane under impact. It is characterized in that include: Step S1, obtaining design parameters of a hydrogen storage buoy of a hydrogen energy seaplane, calculating an impact load on the hydrogen storage buoy of the hydrogen energy seaplane, and obtaining an impact load of the hydrogen storage buoy upon entry into water; Step S2, establishing a finite element model of the hydrogen storage buoy based on the design parameters of the hydrogen storage buoy; Step S3, performing unstructured meshing on the finite element model of the hydrogen storage buoy; Step S4, setting loads and boundary conditions based on the obtained water entry impact load of the hydrogen storage buoy; Step S5, based on the set load and boundary conditions, finite element calculation is performed to obtain the load result of the hydrogen storage buoy, and whether the hydrogen storage buoy can work safely is determined. If it can work safely, the design parameters of the hydrogen storage buoy meet the requirements, and the output is performed for subsequent production and manufacturing. Otherwise, the design parameters of the hydrogen storage buoy are optimized and the process returns to step S1; Wherein step S1 specifically includes: Step S1.1, obtaining design parameters of a hydrogen storage buoy of a hydrogen energy seaplane; Step S1.2, simplify the structure of the hydrogen storage buoy to obtain a wedge-shaped body, and use the design parameters of the hydrogen storage buoy as the parameters of the wedge-shaped body for subsequent processing to obtain the actual wetted half-width of the wedge-shaped body: , the density of water ; Step S1.3, calculating the impact load of the wedge-shaped body, obtaining the maximum water entry impact pressure value of the wedge-shaped body, and using it as the water entry impact load of the hydrogen storage buoy; Wherein, the step S1.3 further comprises: The expression of the impact pressure on the wedge when entering the water is: in, is atmospheric pressure, represents the impact pressure of water on the wedge, represents the velocity potential function of the wedge, Indicates time; in, is a calculated variable; Get the wedge in The impact of the moment sinks to depth in, represents the series coefficient, Indicates the number of times, in, To calculate the variable, The wedge is measured at The speed of the moment; When the wedge enters the water, the part of the water surface adjacent to the wedge that rises above the still water surface is the raised water surface. The impact pressure of the root of the raised water surface on the wedge is the largest, and the calculation results are: Among them, ignore ,get , The maximum water impact pressure of the wedge obtained is Output and save as the impact load of the hydrogen storage buoy entering the water; Wherein, the step S4 specifically includes: The load settings include: The load form is a uniform load, the load position is the V-shaped bottom surface of the hydrogen storage buoy, and the load direction is perpendicular to the V-shaped bottom surface; The setting of boundary conditions includes constraining the z-direction translational freedom of the top of the hydrogen storage buoy.

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