A method for designing an equivalent scaled-down fuel tank for fuel quantity testing

Abstract

This invention relates to an equivalent scaled-down fuel tank design method for fuel quantity testing, comprising the following steps: Step (a) Based on a real three-dimensional digital model of the fuel tank, identify and classify various occupier components, and establish a fuel occupier space model that retains only the space occupied by fuel through Boolean operations; Step (b) After spatially rotating the fuel occupier space model according to the aircraft's parking attitude, slice it horizontally along the gravity direction with equal thickness, calculate the net fuel volume layer by layer, and generate a theoretical correspondence between liquid level and fuel quantity; Step (c) Scale the horizontal section of the fuel occupier space model proportionally with a linear scaling factor, keeping the size in the gravity direction unchanged, to obtain an equivalent scaled-down fuel quantity, and introduce a correction value for non-equivalent scaled-down occupiers, accurately compensating for the volume distribution differences of irregular fuel tanks through occupier blocks, so that the liquid level-fuel quantity curve of the scaled-down model is highly fitted to the prototype (Ri). 2 >0.99), which solves the problem of distorted liquid level-oil quantity relationship.

Description

Technical Field

[0001] This invention relates to the field of capacitive fuel quantity measurement technology for aircraft, and specifically to a design method for an equivalent scaled-down fuel tank for fuel quantity testing. Background Technology

[0002] The aircraft capacitive fuel measurement system reflects the fuel level by the change in the capacitance value between the sensor plates. Its accuracy directly affects flight safety and range judgment. Existing ground inspection and calibration tests rely on real fuel tank environments, which presents the following significant drawbacks: 1. Significant safety hazards: Tests require injecting large quantities of fuel into real fuel tanks, which are flammable and explosive. Furthermore, the aircraft needs to be repeatedly powered on and off to verify sensor responses, posing a risk of combustion and explosion accidents caused by live operation; 2. High reliance on manual labor and low efficiency: The test process has low automation, relying heavily on manual operations (such as level adjustment, data recording, and safety monitoring), which are cumbersome and time-consuming; 3. High resource consumption costs: Tests require the use of aircraft and supporting ground equipment, and other tasks cannot be carried out concurrently, significantly increasing time costs and equipment scheduling pressure. These drawbacks restrict the efficiency and safety of ground inspection and calibration of aviation fuel measurement systems, and the high resource consumption and scheduling costs necessitate an equivalent simulation testing method that can significantly reduce fuel consumption and eliminate the need for real fuel tanks. Summary of the Invention

[0003] (1) Technical problems to be solved The purpose of this invention is to overcome the shortcomings of the aviation fuel measurement system, which is greatly restricted in terms of efficiency and safety, and also has the technical problems of occupying aircraft and supporting equipment and high resource scheduling costs. To this end, this invention provides an equivalent scaled-down fuel tank design method for fuel quantity testing.

[0004] (2) Technical solution To achieve the objectives of this invention, the technical solution adopted is as follows: A method for designing an equivalent scaled-down fuel tank for fuel quantity testing includes the following steps: Step (a): Based on the real three-dimensional digital model of the fuel tank, identify and classify various space-occupying components, and establish a fuel space-occupying space model that retains only the space that fuel can occupy through Boolean operations; Step (b): After the fuel space model is spatially rotated according to the aircraft's parking attitude, it is sliced ​​horizontally with equal thickness along the direction of gravity, and the net fuel volume is calculated layer by layer to generate the theoretical correspondence between liquid level and fuel quantity. Step (c): Scale the horizontal cross-section of the fuel occupancy space model proportionally with a linear scaling factor, keeping the size in the direction of gravity unchanged, to obtain the equivalent scaled fuel volume, and introduce the correction value of the non-equivalent scaled occupancy body to establish the correspondence between the equivalent scaled fuel tank level and the fuel volume. Step (d): Based on the maximum single-layer volume in the equivalent scaled-down tank, design an equivalent scaled-down tank with a uniform cylindrical inner wall. The main dimensions of the tank include the inner diameter and height of the tank. Step (e): Design a series of hollow cylindrical volume correction occupants, whose outer diameter matches the inner diameter of the tank, and whose inner diameter is calculated based on the volume of the corresponding liquid level, so that the remaining volume inside the oil tank after all volume correction occupants are installed is consistent with the volume distribution of the equivalent scaled-down oil tank. Step (f): Assemble the processed volume correction occupant block into the housing to form an equivalent scaled-down oil tank; Step (g): Using a non-flammable liquid as the medium, measure the actual inlet volume segment by segment using a mass flow meter and a pressure transmitter to obtain the correspondence between the liquid level and the measured oil volume, and compare it with the theoretical correspondence of the equivalent scaled-down oil tank. Step (h): If the single-layer relative deviation or the cumulative relative deviation exceeds the set limit, the material of the occupant block at the corresponding height position is removed or supplemented according to the absolute deviation. Step (i) is repeated, and steps (h) to (i) are repeated until all deviations meet the accuracy requirements.

[0005] Preferably, the formula for calculating the slice thickness is: Where Δh is the slice thickness, and D min For the minimum machining feature size, δ sensor For sensor accuracy, A max Let λ be the maximum cross-sectional area of ​​the fuel tank, and λ be the linear proportionality coefficient.

[0006] Preferably, in step (c), the correction value of the non-equivalent scaled-down occupant is obtained by the difference between the volume of the actual scaled-down model occupant and the volume of the scaled-down model occupant at the same liquid level, and a correction dataset is formed.

[0007] Preferably, the formula for calculating the equivalent scaled volume is: in, For the equivalent scaled volume, V i Let ΔV be the net fuel volume of the i-th layer in the theoretical dataset. i λ is the corresponding correction value, and λ is the linear scaling factor.

[0008] Preferably, the formula for calculating the inner diameter of the box is: Among them, D 箱径 t is the inner diameter of the box. min This is the minimum machinable wall thickness for the placeholder block; Preferably, the formula for calculating the height of the box is: Among them, H 箱高 H is the height of the enclosure. N For the highest working liquid level, H 上 H 下 Safety and rectification space are reserved at the top and bottom, respectively.

[0009] Preferably, the volume correction occupant block adopts one or more of the following: a stepped variable inner diameter integrated structure, a segmented fan-shaped structure, or a one-time molding structure through additive manufacturing.

[0010] Preferably, the material removal method involves drilling shallow holes with a diameter of 2 mm and a depth of 2 mm ± 0.5 mm on the inner annular surface of the occupier block, with the volume removed by a single drill hole conforming to N(5 mm²). 3 (1.5mm) 3 ) 2 The normal distribution of ).

[0011] Preferably, the non-flammable liquid in step (g) is water.

[0012] Preferably, in step (i), the relative deviation of the single-layer volume is ≤0.15%, and the cumulative relative deviation of the volume is ≤0.12%.

[0013] Beneficial effects: This invention discloses an equivalent scaled-down fuel tank design method for fuel volume testing. By using a spacer block to accurately compensate for the volume distribution differences of irregular fuel tanks, the level-fuel volume curve of the scaled-down model closely matches the prototype (Ri). 2 >0.99), solving the problem of distorted liquid level-oil quantity relationship, achieving the following effects: 1. Reduced fuel consumption: Fuel consumption is directly proportional to the square of the linear proportionality coefficient λ of the equivalent fuel tank. Taking a linear proportionality coefficient λ = 1 / 3 as an example, fuel consumption reduced to 11.1% of the prototype (e.g., 62 kg / cycle) still meets the test accuracy requirements (mass measurement error ≤ 1%). 2. Reduced testing costs: The equivalent scaled-down tank has a regular columnar structure, eliminating the need to replicate complex internal components, thus reducing processing costs by more than 90% (theoretical calculation value). 3. Improved test efficiency: The rate of liquid level change is increased by λ after scaling down. -2 For example, with λ=1 / 3, the liquid level change rate increases by 9 times at the same fuel flow rate, and the single test cycle is shortened to 1 / 9 of the prototype; 4. Precision Guarantee: The placeholder block supports local fine-tuning (tolerance ±5mm) 3 The overall test error is ≤1% (theoretical estimate). Attached Figure Description

[0014] Figure 1 This is a diagram illustrating the identification and classification of typical structures and spacer components of aviation fuel tanks in this invention; Figure 2 This is a schematic diagram of the precise modeling and slicing of the fuel space occupied in this invention; Figure 3 This is a schematic diagram of the principle of the equivalent scaled-down oil tank of the present invention; Figure 4 This is a schematic diagram of the integrated structure of the volume correction occupant block in this invention; Figure 5 This is a schematic diagram of the equivalent scaled-down fuel tank structure and calibration device of the present invention; Figure 6 This is a convergence plot of the cumulative error distribution during the calibration process in this invention. The plot is in the form of a box plot and is used to show the statistical distribution change of the cumulative relative deviation Δ of the equivalent scaled-down tank during the calibration process. In the figure, the horizontal axis represents the four stages of calibration: initial state, first simulation, second simulation, and third simulation; the vertical axis represents the cumulative relative deviation (Δ, %); each chamber represents the statistical distribution of the cumulative error of all liquid points under the corresponding calibration stage. The upper and lower boundaries of the chambers represent the 75th and 25th percentiles of the data, the horizontal line inside the chamber represents the median, and the endpoints of the chamber represent the maximum and minimum values ​​of the data. Figure 7 This is a statistical chart of calibration workload in this invention. The chart is in the form of a stacked bar chart and is used to show the changes in the amount of additional drilling work in each correction operation. In the diagram, the horizontal axis represents the layer number of the placeholder block; the vertical axis represents the number of newly drilled holes. Each column is composed of stacked segments representing the number of holes drilled in each correction operation. Figure 8 This is a comparison chart of the slice error distribution across the entire liquid level range in this invention. The chart consists of four horizontally arranged sub-charts, which are used to show the change of the relative deviation δ of the slice volume with the liquid level height during the calibration process. The four sub-charts correspond from left to right to the error in the initial state and the upper limit distribution of the error after the first correction, the second correction, and the third correction. The coordinate axis scales of each sub-chart are consistent. Figure 9 This is a graph showing the calibration results of the liquid level-oil volume relationship in this invention. This graph is used to evaluate the global measurement accuracy after the calibration algorithm of this invention is completed. In the figure, the horizontal axis represents the liquid level height in mm; the vertical axis represents the relative deviation of the oil volume in percentage. The two curves in the figure represent the upper and lower limits of the deviation of the system measurement results from the theoretical value, respectively. In the diagram: 1. Fuel tank body; 2. Permanent occupant assembly; 3. Maximum fuel level in the tank; 4. Fuel tank control pipeline; 5. Fuel pump filling valve; 6. Capacitive fuel quantity sensor; 7. Level sensor; 8. Fuel occupancy space model; 9. Dynamic occupant; 10. Non-equivalent scaled-down occupancy space; 11. Fuel slice; 12. Actual fuel occupancy space model; 13. Equivalent scaled-down fuel quantity; 14. Maximum scaled-down fuel quantity slice; 15. Scaled-down fuel quantity level slice; 16. Inner cylinder 17. Outer cylindrical slice; 18. Volume correction occupant block; 19. Cylindrical inner wall; 20. Continuous slice part assembly; 21. Variable inner diameter integrated part; 22. Segmented part; 23. Fuel tank vent; 24. Housing; 25. Volume correction occupant block assembly; 26. Fuel inlet / outlet port; 27. Pressure transmitter; 28. Fuel quantity sensor mounting base; 29. ​​Mass flow meter; 30. Bidirectional fuel pump; 31. Flow valve; 32. Fuel tank; 33. Industrial computer; 34. Integrated control module. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] The following embodiments further illustrate the present invention: Examples, such as Figure 1-9 As shown, an equivalent scaled-down fuel tank design method for fuel quantity testing includes the core implementation steps of establishing a real fuel space model, establishing theoretical data on fuel level and quantity, designing an equivalent scaled-down fuel tank, designing a volume correction spacer block, machining the spacer block and installing it into the fuel tank, and calibrating the equivalent scaled-down fuel tank. These steps are detailed below: 1. Establish a realistic fuel space model Based on the actual fuel tank design digital model, the fuel space is accurately modeled, excluding the volume of all non-fuel space-occupying components. The specific steps are as follows: (1) Identification and classification of space-occupying components (e.g.) Figure 1 (As shown) Permanent spacer: oil pump (5), pipeline (4) that is always filled with oil, sensor bracket, reinforcing ribs and partition (2) and other fixed structures; Non-structural spacers: Spacers such as sealants, adhesives, and rivet head protrusions are not typically modeled in 3D in the design model; Dynamic occupant: movable pipeline, float of float-type liquid level sensor (7), amount of oil in pipeline and equipment cavity that changes with the liquid level in oil tank, etc. Non-equivalent scaled-down spacer: The capacitive oil level sensor (6) is the test object, but it still exists in the true scale in the equivalent scaled-down oil tank.

[0017] (2) Precise modeling of fuel space (e.g.) Figure 2 (As shown) (a) Removal of permanent and unstructured occupants In CAD software, a volume model of the fuel tank body (1) is established and cut along the highest filling level (2) of the fuel tank. Through Boolean difference set operation, the volume of permanent occupants, non-structural occupants and non-equivalent scaled occupant space (10) are removed one by one from the total volume of the fuel tank to obtain the fuel occupant space model (8). Permanent occupants are obtained directly from the design model, while non-structural occupants are modeled based on standard part dimensions, design requirements, and process requirements. The impact of non-equivalent scaled-down occupants on liquid level is corrected when establishing the liquid level-oil volume theoretical model.

[0018] (b) Establishment of dynamic occupant constraint rules and location preset In CAD software, the physical constraint relationship and motion simulation rules between the dynamic occupiers (9) such as floats and movable pipelines and the fuel level are established. For example, when the float's center position (9A) and the fuel level (9B) are in the working state, the difference between the two is constant. When the float drops to the mechanical limit (9C), the float stops moving. Based on the constraint rules, the spatial position of the dynamic occupiers corresponding to each liquid level slice layer is preset for subsequent layered slicing processing to ensure that its state is consistent with the actual physical behavior during slice calculation.

[0019] In summary, by removing permanent, unstructured, and non-equivalent scaled-down occupiers through Boolean operations and establishing physical constraints on dynamic occupiers, precise fuel slices of arbitrary liquid level and specified thickness can be obtained (11).

[0020] 2. Establish a theoretical dataset of liquid level and oil volume. This step, based on the accurate modeling results of the fuel space, generates a theoretical dataset corresponding to the liquid level and fuel quantity using a discretization method. The specific process is as follows: (1) Model space attitude preprocessing The fuel space model is rotated once according to the aircraft's parking attitude angle (such as takeoff / landing attitude) required by the test, so that the model coordinate system matches the direction of gravity and ensures that subsequent slice calculations meet the actual test conditions.

[0021] (2) Setting horizontal slicing parameters The slicing direction is horizontal layering along the vertical direction (gravity direction) of the transformed model; Slice thickness Δh: Determined by a theoretical formula based on the minimum machining feature size of the occupant block (e.g., 2mm) and sensor accuracy constraints (e.g., ±0.1%FS), as follows: in: D min Minimum feature size; δ sensor For sensor accuracy; A max This represents the maximum cross-sectional area of ​​the fuel tank. λ is the linear proportionality coefficient; ; L 等效 L is the linear dimension of the equivalent model. 实际 This corresponds to the linear dimension of the actual object.

[0022] (3) Calculation of net fuel volume (a) Layered volume integral Perform the following operations on each slice (thickness Δh): Modeling the fuel space occupied by the slice: In CAD software, the model is cut by Boolean operation to generate a horizontal slice with a thickness of Δh, and the dynamic spacer position parameters (such as float coordinates and pipeline offset) preset above are called to exclude its spacer volume by difference operation. Net volume calculation: Obtain the net fuel volume V of a single layer through geometric calculations using CAD software. i (i is the slice layer number).

[0023] (b) Generation of discrete datasets Accumulate the net volume of each layer to generate discrete liquid level-oil volume data: in: i = 1, 2, ..., N (N is the total number of slices) (4) Output of theoretical dataset To facilitate the detection and calibration of the level sensor and the correction of fuel quantity errors in subsequent scaled-down tests, the net fuel volume V of a single layer is pre-stored in the dataset. i The final output is a discrete dataset D-theory: D 理论 ={(H i V i Q i )|i=1,2,…,N} The data storage format supports the following features: (a) Dynamic computing capability: Supports real-time interpolation, error correction and other mathematical operations (such as through database queries or Excel formulas); (b) Standardized interface: Provides data call interface (such as API function or data table association field) for the scaled-down test system to read directly; (c) Scalability: The data structure includes the liquid level height H i Single-layer net fuel volume V i and cumulative oil volume Q i Key fields such as...

[0024] 3. Design an equivalent scaled-down fuel tank (e.g.) Figure 3 (As shown) (1) Non-equivalent scaled placeholder correction value dataset To address the oil quantity measurement error caused by the asynchronous scaling of non-equivalent scaled-down occupiers in the scaled-down model, a dedicated correction value dataset is constructed, and high-precision correction is achieved through a lookup table method. The correction value is defined as follows: in: i=1,2,…,N (N is the total number of slices); Let be the volume of the placeholder in the i-th slice of the actual scale model; Let be the volume of the occupant in the i-th slice of the scaled-down model; Both were obtained by layering and slicing according to the method described in (3)(a).

[0025] The output is a discrete dataset. D 修正 : D 修正 ={( H i , ΔV 修正i )∣ i =1,2,…, N} (2) Equivalent scaled-down oil tank level-oil quantity dataset (a) Scaled-down volume conversion Based on a real fuel tank level-volume theoretical dataset, the equivalent scaled volume is calculated by scaling the horizontal plane dimension using a linear scaling factor λ (while keeping the direction of gravity constant). This scaling principle is... Figure 3 This is illustrated by schematically converting the real fuel space model (12) into an equivalent scaled-down fuel volume (13). The liquid level H in the scaled-down fuel volume... i The equivalent scaled volume Vi of the slice (15) is calculated by the following formula: in: V iThe net fuel volume of the i-th slice (11) in the theoretical dataset; The correction value is the corresponding slice of the i-th layer in the non-equivalent scaled placeholder correction value dataset.

[0026] (b) Generation of discrete datasets Accumulate the net volume of each layer to generate discrete data of liquid level-equivalent oil volume: in: i = 1, 2, ..., N (N is the total number of slices) The output is a discrete dataset: D 等效 ={( H i , V 等效i , Q 等效i )∣ i =1,2,…, N} (3) Main dimensional parameters of the equivalent scaled-down fuel tank The equivalent scaled-down oil tank has a uniform cylindrical inner wall (19) within its liquid level variation range. The main dimensional design parameters include the inner diameter of the tank. D 箱径 Box height H 箱高 : Based on the equivalent volume of the slice with the largest volume in the equivalent oil volume of dataset D (14), the equivalent volume is: Calculate the inner diameter using the cylinder volume formula, and determine the minimum machinable wall thickness t of the hollow cylindrical occupier. min Correction: Among them, t min It is determined by the materials used in the placeholder block, the machining capabilities, and the assembly capabilities.

[0027] Box height H 箱高 Mainly determined by the highest working height of the liquid level H N Reserved space above H 上 and reserved space H 下 It consists of three parts: in: H 上The main consideration is to reserve a safety space at the top of the fuel tank to allow time for emergency operations in special circumstances such as control failure or operational errors, and to prevent fuel leakage. H 下 The main consideration is that the fuel passage at the bottom of the fuel tank has sufficient rectification space, so that the flow field tends to be static throughout the test, reducing the impact on the differential pressure sensor and the fuel quantity sensor.

[0028] 4. Design volume correction spacer block The volume correction occupant block (18) is a hollow cylinder, constructed based on two cylindrical slices of equal thickness and volume: the outer cylindrical slice (17) is derived from the slice (14) with the largest volume in the reduced oil volume, and the inner cylindrical slice (16) is derived from the specified liquid level H. i The hollow cylinder is obtained by converting the scaled-down oil volume slice (15) at that time. After performing Boolean difference operation between the two, the final volume correction occupant block (18) is obtained after correction.

[0029] The main dimensional design parameters include the outer diameter of the spacer block. D 外径 Inner diameter of the placeholder block and the thickness H of the placeholder block, where: D 外径 Theoretically equal to the inner diameter of the box D 箱径 For ease of assembly, this size can be slightly smaller. D 箱径 After assembly, fill the installation gaps with glue; H 厚度 equal to slice thickness Δh ; It is derived from the volume formula and a correction allowance is subtracted. D 修正 : D 修正 This is the machining allowance reserved for calibration; it can be a fixed value or a variable. Related variables.

[0030] 5. Machining the spacer block and installing it into the oil tank. (1) Limitations of the original method Solve according to equation (8) Select according to formula (1) Δh The theoretically calculated data processing occupant block is based on the highest working height of the liquid level. H N Taking 900mm as an example and Δh=2mm as an example, the part to be processed This design, using a hollow cylinder, has a significant drawback: (a) Large processing volume: The large number of thin-walled parts significantly increases the manufacturing cycle and cost; (b) Significant material waste: The materials inside the ring structure cannot be reused; (c) High accuracy risk: A large number of stacked assemblies lead to cumulative errors, reducing the accuracy of the system.

[0031] (2) Optimization scheme for placeholder block processing (e.g.) Figure 4 (As shown) To address the aforementioned issues, it is necessary to simplify the processing flow through structural optimization and technological innovation to achieve the goals of cost reduction, efficiency improvement, and precision enhancement. The specific solution is as follows: (a) Merging adjacent layers – Variable inner diameter integrated design D 内径i Continuous slices (20) that remain unchanged or have a consistent trend of change are merged into a stepped hollow cylinder assembly (21) to reduce the number of parts; (b) Segmented Circular Ring – Petal-shaped Structure Design The hollow cylinder (or a combination thereof) is divided into multiple identical sector-shaped parts (22), which are then machined by CNC to improve material utilization. (c) Additive manufacturing – integrated molding technology The structure is manufactured directly using 3D printing technology, which reduces the difficulty of processing and improves calibration efficiency.

[0032] 6. Equivalent scaled-down fuel tank calibration (e.g.) Figure 5 (As shown) The calibration device consists of an equivalent scaled-down oil tank, a media supply system, and a measurement and recording system, which are interconnected through oil and electrical circuits.

[0033] The equivalent scaled-down oil tank has a built-in volume correction occupant block group (25) in the tank body (24), an oil tank vent (23) and an oil quantity sensor mounting base (28) on the top, and an oil filling / draining port (26) at the bottom.

[0034] The medium supply system is controlled by the integrated control module (34), which uses a two-way fuel pump (30) and a flow valve (31) to precisely deliver the medium from the fuel tank (32) to the equivalent scaled-down fuel tank, or to empty it.

[0035] In the measurement and recording system, the mass flow meter (29) is used to measure parameters such as instantaneous flow rate, cumulative flow rate, density, and temperature of the medium. The pressure transmitter (27) is used to measure the medium pressure at the bottom of the equivalent scaled-down oil tank. The industrial control computer (33) collects the above physical quantities through the integrated control module (34) and calculates and records the cumulative flow rate and liquid level.

[0036] In this calibration method, water is used as the test medium instead of fuel oil. The specific steps are as follows: (1) Install the oil quantity sensor or its process dummy, add water to the starting position of the working fluid level in the oil tank, and record the measurement zero point through the pressure transmitter; (2) Water is slowly injected into the oil tank. The rise in liquid level is recorded by a mass flow meter for every Δh. V 实测 Generate discrete data of liquid level and measured oil volume: in: i = 1, 2, ..., N (N is the total number of slices) The output is a discrete dataset. D 实测 : D 实测 ={( H i , V 实测i , Q 实测i )∣ i =1,2,…, N} (3) Through discrete datasets D 等效 and D 实测 Calculate the single-layer deviation and cumulative deviation, and determine the accuracy criteria: (a) Single-layer deviation: for each liquid level height H i Calculate the absolute deviation between the equivalent oil quantity and the measured oil quantity. ΔV 校准i and relative deviation δ 校准i : in: absolute deviation ΔV 校准i This serves as the basis for correcting the corresponding placeholder blocks; relative deviation δ 校准i This serves as a single-layer accuracy criterion.

[0037] (b) Cumulative deviation: from the initial liquid level H 1 Up to current liquid level H i Calculate the cumulative relative deviation Δ 校准i : Wherein: relative deviation Δ校准i This serves as the criterion for cumulative accuracy.

[0038] (c) Accuracy criterion setting Set permissible limits for single-layer deviation δ max and cumulative deviation allowable limit Δ max (like δ max =0.01, Δ max =0.05).

[0039] If all single-layer deviations satisfy | δ 校准i |≤ δ max And the cumulative deviation satisfies | Δ 校准i |≤ Δ max If the accuracy meets the design requirements, the calibration is complete. If any condition is not met, the accuracy of the judgment is deemed insufficient, and the absolute deviation must be considered. ΔV 校准i After cutting or supplementing the corresponding height position of the occupant block group, repeat steps (1) to (3) to recalibrate.

[0040] This application, through equivalent scaled design and simulation testing of a certain type of UAV fuel tank, and after three simulation corrections, achieves the following global measurement accuracy results for the calibration algorithm of this invention: Figure 6-9 As shown: like Figure 6 As shown in the convergence plot of the cumulative error distribution during the calibration process, the statistical distribution of the box plot narrows significantly with the increase of the number of calibrations, and both the median and the error band rapidly approach zero. This clear downward trend indicates that the calibration procedure proposed in this method can effectively compensate for the initial error, enabling the system accuracy to gradually approach the theoretical limit. Figure 7 The height of the stacked histogram decreased significantly with the number of iterations, which intuitively shows that the amount of drilling work required for subsequent corrections was reduced sharply, proving the efficiency of the calibration process; Figure 8 The upper limit of the relative volume deviation (δ upper limit) of all slices across the entire liquid level range after each correction is shown in scatter plot form. It can be clearly seen that as the number of iterations increases, the distribution range of the scatter points decreases significantly and they cluster more closely near the zero point. This indicates that even with processing randomness, this method can still systematically reduce its impact on measurement accuracy and ensure the reliability of the final results; Figure 9The two curves clearly show the upper and lower limits of the deviation of the system measurement results from the theoretical value. The relative deviation is strictly controlled within the band area of ​​0~0.2% throughout the entire liquid level working range.

[0041] Simulation results show that the theoretical scheme is feasible.

[0042] The iterative calibration algorithm can gradually correct a system with an initial error of 2.16% to a high-precision state with a final cumulative deviation of no more than 0.12% under simulated real-world measurement and manufacturing constraints. This method has been proven to be convergent, efficient, and robust, providing a reliable and quantifiable technical path for high-precision scale-up testing.

[0043] The embodiments disclosed herein are preferred embodiments, but are not limited thereto. Those skilled in the art can readily grasp the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for designing an equivalent scaled-down fuel tank for fuel quantity testing, characterized in that, Includes the following steps: Step (a): Based on the real three-dimensional digital model of the fuel tank, identify and classify various space-occupying components, and establish a fuel space-occupying space model that retains only the space that fuel can occupy through Boolean operations; Step (b): After the fuel space model is spatially rotated according to the aircraft's parking attitude, it is sliced ​​horizontally with equal thickness along the direction of gravity, and the net fuel volume is calculated layer by layer to generate the theoretical correspondence between liquid level and fuel quantity. Step (c): Scale the horizontal cross-section of the fuel occupancy space model proportionally with a linear scaling factor, keeping the size in the direction of gravity unchanged, to obtain the equivalent scaled fuel volume, and introduce the correction value of the non-equivalent scaled occupancy body to establish the correspondence between the equivalent scaled fuel tank level and the fuel volume. Step (d): Based on the maximum single-layer volume in the equivalent scaled-down tank, design an equivalent scaled-down tank with a uniform cylindrical inner wall. The main dimensions of the tank include the inner diameter and height of the tank. Step (e): Design a series of hollow cylindrical volume correction occupants, whose outer diameter matches the inner diameter of the tank, and whose inner diameter is calculated based on the volume of the corresponding liquid level, so that the remaining volume inside the oil tank after all volume correction occupants are installed is consistent with the volume distribution of the equivalent scaled-down oil tank. Step (f): Assemble the processed volume correction occupant block into the housing to form an equivalent scaled-down oil tank; Step (g): Using a non-flammable liquid as the medium, measure the actual inlet volume segment by segment using a mass flow meter and a pressure transmitter to obtain the correspondence between the liquid level and the measured oil volume, and compare it with the theoretical correspondence of the equivalent scaled-down oil tank. Step (h): If the single-layer relative deviation or the cumulative relative deviation exceeds the set limit, the material of the occupant block at the corresponding height position is removed or supplemented according to the absolute deviation. Step (i) is repeated, and steps (h) to (i) are repeated until all deviations meet the accuracy requirements.

2. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The formula for calculating the slice thickness is: Where Δh is the slice thickness, and D min For the minimum machining feature size, δ sensor For sensor accuracy, A max Let λ be the maximum cross-sectional area of ​​the fuel tank, and λ be the linear proportionality coefficient.

3. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, In step (c), the correction value of the non-equivalent scaled-down occupant is obtained by the difference between the volume of the actual scaled-down model occupant and the volume of the scaled-down model occupant at the same liquid level, and a correction dataset is formed.

4. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 2, characterized in that, The formula for calculating the equivalent scaled volume is: in, For the equivalent scaled volume, V i Let ΔV be the net fuel volume of the i-th layer in the theoretical dataset. i λ is the corresponding correction value, and λ is the linear scaling factor.

5. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The formula for calculating the inner diameter of the box is: in, t is the inner diameter of the box. min This is the minimum machinable wall thickness for the placeholder block.

6. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The formula for calculating the height of the box is: Among them, H 箱高 H is the height of the enclosure. N For the highest working liquid level, H 上 H 下 Safety and rectification space are reserved at the top and bottom, respectively.

7. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The volume correction occupant block adopts one or more of the following: a stepped variable inner diameter integrated structure, a segmented fan-shaped structure, or a one-time molding structure through additive manufacturing.

8. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The material removal method involves drilling shallow holes with a diameter of 2 mm and a depth of 2 mm ± 0.5 mm on the inner annular surface of the occupier. The volume removed by a single drill hole follows the order N(5 mm²). 3 (1.5mm) 3 ) 2 The normal distribution of ).

9. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, The non-flammable liquid in step (g) is water.

10. The equivalent scaled-down fuel tank design method for fuel quantity testing as described in claim 1, characterized in that, In step (i), the relative deviation of the single-layer volume is ≤0.15%, and the cumulative relative deviation of the volume is ≤0.12%.

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