A method for determining parameters of a fuel state equation for studying sloshing load of an aircraft fuel tank

Abstract

This application relates to a method for determining the parameters of the fuel equation of state in aircraft fuel tank sloshing load research, comprising: Step 1, conducting a fuel tank sloshing principle test under multiple test conditions; Step 2, dividing the multiple test conditions into parameter optimization conditions and parameter verification conditions; Step 3, initializing the bulk modulus and dimensionless state parameters of the fuel equation of state, and calculating the pressure of the fuel on the fuel tank wall under the parameter optimization conditions; Step 4, comparing the pressure of the fuel on the fuel tank wall obtained from the fuel tank sloshing principle test under the parameter optimization conditions with the pressure of the fuel on the fuel tank wall calculated by the fuel equation of state, and adjusting and optimizing the bulk modulus and dimensionless state parameters; Step 5, comparing the pressure of the fuel on the fuel tank wall obtained from the fuel tank sloshing principle test under the parameter verification conditions with the pressure of the fuel on the fuel tank wall calculated by the fuel equation of state, and verifying the bulk modulus and dimensionless state parameters.

Description

Technical Field

[0001] This application belongs to the technical field of aircraft fuel tank sloshing load research, specifically relating to a method for determining the parameters of the fuel state equation in aircraft fuel tank sloshing load research. Background Technology

[0002] There are three main methods for studying aircraft fuel tank sloshing loads:

[0003] The theoretical research method is suitable for small linear sloshing, but it cannot provide an accurate solution for large nonlinear sloshing or when the oil splashes or other motions.

[0004] Experimental research methods can provide very intuitive results, but for large fuel tanks, the test cycle is long, the cost is high, and the requirements for test equipment are high.

[0005] With the rapid development of computer technology, numerical research methods have seen a rapid improvement in computational efficiency and accuracy. Furthermore, they are unaffected by the morphology of oil sloshing and can effectively solve large-scale nonlinear sloshing problems. The cycle time and cost are also significantly reduced compared to experiments.

[0006] Meshless smooth particle numerical computation methods have developed rapidly and are widely used due to their mature modeling methods and high computational accuracy, making them one of the most widely used and accurate methods for fluid-structure interaction computation. Meshless particle algorithms use the Monaghan equations of state to simulate the constitutive model of particle elements, simulating the pressure exerted on the structure by oil-fluid particle elements, which can be obtained by solving the equations of state. However, solving the equations of state requires two relevant parameters. Information on these two parameters, γ and γ, is scarce in publicly available data, especially given the variety of fuel types and the difficulty in obtaining such information. These two parameters significantly impact the solution for oil sloshing, and precise values ​​are required for fuel tank sloshing load analysis to ensure accuracy.

[0007] In view of the above, this application is hereby filed. Summary of the Invention

[0008] The purpose of this application is to provide a method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load. This method is based on a meshless particle algorithm to optimize the parameters of the fuel state equation, and finally determines the optimal solution parameters, thus solving the problems of missing and inaccurate fuel state equation parameters in the numerical analysis of fuel tank sloshing.

[0009] The technical solution of this application is:

[0010] 1. A method for determining fuel state equation parameters in aircraft fuel tank sloshing load research, characterized in that it includes:

[0011] Step 1: Conduct a principle test of tank swaying under multiple test conditions;

[0012] Step 2: Divide the multiple test conditions into parameter optimization conditions and parameter verification conditions;

[0013] Step 3: Initialize the bulk modulus of the fuel equation of state. 1. Dimensionless state parameter γ, calculated parameter optimization for the pressure of oil on the tank wall under the working condition;

[0014] Step 4: Compare the pressure of the oil on the tank wall obtained from the principle test of tank sloshing under the operating condition, and the pressure of the oil on the tank wall calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ is adjusted and optimized.

[0015] Step 5: Compare the parameters used to verify the pressure of the oil on the tank wall plate obtained from the tank sloshing principle test under the operating condition, and the pressure of the oil on the tank wall plate calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ was used for verification.

[0016] The fuel state equation is:

[0017] ;

[0018] in,

[0019] This refers to the pressure of the oil on the tank wall. This represents the initial pressure of the oil on the tank wall. For the density of the oil, The initial density of the oil is given.

[0020] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step one, a scaled-down fuel tank is designed, and under multiple test conditions, a multi-degree-of-freedom sloshing platform is used to conduct a principle test of fuel tank sloshing and collect the pressure of the oil on the fuel tank wall.

[0021] According to at least one embodiment of this application, in the above-described method for determining fuel state equation parameters in the study of aircraft fuel tank sloshing load, in step one, a test scaled-down fuel tank is manufactured using aluminum alloy material.

[0022] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step one, the designed test condition has a filling rate of 1 / 2 to 2 / 3, a sloshing frequency of 0.5 Hz to 1 Hz, and a sloshing amplitude of -30° to +30°.

[0023] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step two, there is one operating condition for setting parameter optimization and multiple operating conditions for parameter verification.

[0024] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step three, the bulk modulus of the fuel state equation is initialized. =0.015.

[0025] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step three, the dimensionless state parameter γ of the fuel state equation is initialized to 7.

[0026] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step four, the bulk modulus of the fuel state equation is... The dimensionless state parameter γ is set with a variation range of ±20%. Iterative calculations optimize the parameters by measuring the oil pressure on the tank wall under the operating conditions, comparing it to the oil pressure on the tank wall obtained from a tank sway principle test, and adjusting the bulk modulus. The dimensionless state parameter γ is adjusted and optimized.

[0027] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, in step five, if the relative error between the pressure of the fuel fluid on the fuel tank wall plate calculated by the fuel state equation under the parameter verification operating condition and the pressure of the fuel fluid on the fuel tank wall plate obtained by the fuel tank sloshing principle test is greater than the relative error threshold, then the bulk modulus is recalculated. The dimensionless state parameter γ is adjusted and optimized until the error value is less than the relative error threshold.

[0028] According to at least one embodiment of this application, in the above-described method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load, the relative error threshold in step five is 15%. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the method for determining fuel state equation parameters in the study of aircraft fuel tank sloshing load provided in this application embodiment.

[0030] To better illustrate this embodiment, some content in the accompanying drawings may be omitted. They are for illustrative purposes only and should not be construed as limiting the scope of this application. Detailed Implementation

[0031] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, and other related parts can be referred to the general design.

[0032] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The word "comprising" as used in this application description indicates that the concept preceding the word encompasses the concepts listed following the word and their equivalents, without excluding other related concepts.

[0033] For the study of aircraft fuel tank sloshing loads, the meshless particle algorithm uses the Monaghan fuel state equation as follows:

[0034] ;

[0035] in,

[0036] This refers to the pressure of the oil on the tank wall. This represents the initial pressure of the oil on the tank wall. This refers to the bulk modulus of the oil. For the density of the oil, Let ρ be the initial density of the oil, and γ be a dimensionless state parameter.

[0037] To solve for the fuel condition, the initial pressure of the fuel is... and density Both can be used as known quantities, bulk modulus The dimensionless state parameter γ is an indispensable constant for solving the equation and affects the accuracy of the solution results; therefore, it is an optimization parameter.

[0038] A method for determining fuel state equation parameters in aircraft fuel tank sloshing load research, such as... Figure 1 As shown.

[0039] Step 1: Conduct a principle test of tank swaying under multiple test conditions.

[0040] Design a scaled-down oil tank for testing. It can be made of aluminum alloy. Under multiple test conditions, a multi-degree-of-freedom shaking platform is used to conduct a principle test of the oil tank shaking. The pressure of the oil on the tank wall is collected and can be calculated from the strain on the tank wall.

[0041] The test conditions included a filling rate of 1 / 2 to 2 / 3, a shaking frequency of 0.5 Hz to 1 Hz, and a shaking amplitude of -30° to +30°.

[0042] Step 2: Divide the multiple test conditions into parameter optimization conditions and parameter verification conditions.

[0043] There is one operating condition for parameter optimization and multiple operating conditions for parameter verification, which are selected based on the results of the principle test of oil tank swaying.

[0044] Step 3: Initialize the bulk modulus of the fuel equation of state. The dimensionless state parameter γ is used to calculate the pressure of the oil on the tank wall plate under the working condition for parameter optimization.

[0045] The bulk modulus of the fuel equation of state can be initialized by referring to existing similar fluids. The dimensionless state parameter γ can be initialized. =0.015, γ=7.

[0046] Step 4: Compare the pressure of the oil on the tank wall obtained from the principle test of tank sloshing under the operating condition, and the pressure of the oil on the tank wall calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ is adjusted and optimized.

[0047] Bulk modulus of fuel equation of state The dimensionless state parameter γ is set with a variation range of ±20%. Iterative calculations optimize the parameters by measuring the oil pressure on the tank wall under the operating conditions, comparing it to the oil pressure on the tank wall obtained from a tank sway principle test, and adjusting the bulk modulus. The dimensionless state parameter γ is adjusted and optimized, with the optimization objective being that the relative error is less than the relative error threshold, which can be taken as 15%, or the difference is minimized.

[0048] ,in, The pressure of the fuel fluid on the fuel tank wall plate is calculated using the fuel state equation. The pressure of the oil on the tank wall plate is obtained from the principle test of tank sloshing. (Subscript) Indicates the first Pressure data at each measuring point.

[0049] Step 5: Compare the parameters used to verify the pressure of the oil on the tank wall plate obtained from the tank sloshing principle test under the operating condition, and the pressure of the oil on the tank wall plate calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ was used for verification.

[0050] If, under the operating conditions used for parameter verification, the pressure of the fuel fluid on the fuel tank wall calculated by the fuel state equation has a relative error greater than the relative error threshold compared to the pressure of the fuel fluid on the fuel tank wall obtained from the fuel tank sloshing principle test, then the bulk modulus should be recalculated. The dimensionless state parameter γ is adjusted and optimized until the error value is less than the relative error threshold. Steps four and five can be repeated.

[0051] In a specific example, the method for determining the parameters of the fuel state equation in the study of aircraft fuel tank sloshing load disclosed in the above example is implemented as follows.

[0052] 1. Design and conduct a principle test of fuel tank sloshing, measure the test data and record and analyze it.

[0053] The test conditions are shown in the table below:

[0054] The pressure of the oil on the tank wall is collected.

[0055] 2. Use working condition 1 as the working condition for parameter optimization, and use working conditions 2 to 6 as the working conditions for parameter verification.

[0056] 3. Initialize the bulk modulus of the fuel equation of state. =0.015, dimensionless state parameter γ=7, calculate the pressure of oil on the tank wall plate under the working condition for parameter optimization.

[0057] 4. Bulk modulus of fuel according to the equation of state The dimensionless state parameter γ is set by varying the range of ±20%, and some combinations are shown in the table below:

[0058] Under iterative calculation condition 1, the pressure of the oil on the tank wall is compared with the pressure of the oil on the tank wall obtained from the principle test of tank swaying. Overall, =0.015、 =5.6 and =0.018、 In both cases (e.g., 5.6), the relative error is relatively small, as shown in the table below:

[0059] Reducing the γ value to a certain extent can make the calculated results closer to the experimental results. =0.015、 =5.6 and =0.018、 Based on γ = 5.6, we further reduced γ to 4 and 3 to explore the optimal parameter combination. The relative error comparison is shown in the table below:

[0060] Overall, When γ = 0.015, reducing γ can decrease the relative error, but reducing it too much will cause the relative error to increase again. When γ = 0.018, reducing γ can gradually decrease the relative error, but the rate of decrease is very slow, and the relative error at the S1 measuring point remains above 15%.

[0061] When γ = 0.015 and γ = 4, the relative errors of the two measuring points S1 and S2 are both within 15%, which meets the optimization target requirements.

[0062] Step 5: Compare the pressure of the fuel on the fuel tank wall obtained from the fuel tank sloshing principle test under operating conditions 2 to 6 with the pressure of the fuel on the fuel tank wall calculated by the fuel state equation. Both meet the optimization target requirements; therefore, the determination will be made... =0.015, γ=4.

[0063] The method for determining fuel state equation parameters in the study of aircraft fuel tank sloshing load disclosed in the above embodiments can efficiently and accurately determine fuel state equation parameters, support efficient and accurate calculation of fuel state parameters, support the study of fuel tank sloshing load, and reduce cycle time and cost.

[0064] The technical solution of this application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A method for determining fuel state equation parameters in aircraft fuel tank sloshing load research, characterized in that, include: Step 1: Conduct a principle test of tank swaying under multiple test conditions; Step 2: Divide the multiple test conditions into parameter optimization conditions and parameter verification conditions; Step 3: Initialize the bulk modulus of the fuel equation of state.

1. Dimensionless state parameter γ, calculated parameter optimization for the pressure of oil on the tank wall under the working condition; Step 4: Compare the pressure of the oil on the tank wall obtained from the principle test of tank sloshing under the operating condition, and the pressure of the oil on the tank wall calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ is adjusted and optimized. Step 5: Compare the parameters used to verify the pressure of the oil on the tank wall plate obtained from the tank sloshing principle test under the operating condition, and the pressure of the oil on the tank wall plate calculated by the fuel state equation, and compare the bulk modulus. The dimensionless state parameter γ was used for verification. The fuel state equation is: ； in, This refers to the pressure of the oil on the tank wall. This represents the initial pressure of the oil on the tank wall. For the density of the oil, The initial density of the oil is given.

2. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 1, characterized in that, In step one, a scaled-down oil tank is designed for testing. Under multiple test conditions, a multi-degree-of-freedom swaying platform is used to conduct a principle test of the oil tank swaying and to collect the pressure of the oil on the tank wall.

3. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 2, characterized in that, In step one, a scaled-down test tank is manufactured using aluminum alloy.

4. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 3, characterized in that, In step one, the designed test conditions are as follows: the liquid filling rate is 1 / 2 to 2 / 3, the shaking frequency is 0.5 Hz to 1 Hz, and the shaking amplitude is -30° to +30°.

5. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 4, characterized in that, In step two, there is one operating condition for setting parameter optimization, and multiple operating conditions for parameter verification.

6. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 5, characterized in that, In step three, the bulk modulus of the fuel equation of state is initialized. =0.

015.

7. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 6, characterized in that, In step three, the dimensionless state parameter γ=7 of the fuel state equation is initialized.

8. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 7, characterized in that, In step four, the bulk modulus of the fuel equation of state is... The dimensionless state parameter γ is set with a variation range of ±20%. Iterative calculations optimize the parameters by measuring the oil pressure on the tank wall under the operating conditions, comparing it to the oil pressure on the tank wall obtained from a tank sway principle test, and adjusting the bulk modulus. The dimensionless state parameter γ is adjusted and optimized.

9. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 8, characterized in that, In step five, if the relative error between the pressure of the fuel on the tank wall plate calculated by the fuel state equation under the parameter verification condition and the pressure of the fuel on the tank wall plate obtained by the fuel tank sloshing principle test is greater than the relative error threshold, then the bulk modulus is recalculated. The dimensionless state parameter γ is adjusted and optimized until the error value is less than the relative error threshold.

10. The method for determining fuel state equation parameters in aircraft fuel tank sloshing load research according to claim 9, characterized in that, In step five, the relative error threshold is 15%.

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