Design method of watertight compartment water level detector and aircraft watertight compartment water level measuring system

Abstract

The invention provides a design method of a watertight compartment water level detector and an airplane watertight compartment water level measuring system. The method comprises the steps that a CATIA digital-analog model of a watertight compartment is established; calculating and determining a gravity center safety margin value; determining the maximum allowable water inflow of each watertight compartment; according to the finally determined maximum allowable water inflow of each watertight compartment, simulating the water level of the maximum allowable water inflow of each watertight compartment on the CATIA digital-analog model under the horizontal attitude of the airplane; the alarm water inlet line of the airplane in the horizontal attitude is used as the height position reference of the water level detector in the watertight compartment; determining heading positions of water level detectors at the front and rear parts of the watertight compartment; and determining the spanwise position of the water level detector in the watertight compartment, wherein the spanwise position is selected on the plane of symmetry at the bottom of the aircraft ship. The layout design of the water level detector is optimized according to the shape of the ship body of the airplane, the distribution condition of the watertight compartment, the maximum allowable water inflow of the watertight compartment and the water surface operation posture change of the airplane, and the accuracy and practicability of monitoring the water inflow condition of the watertight compartment are improved.

Description

Technical Field

[0001] The invention relates to the technical field of liquid level detection, and in particular to a design method for a watertight compartment water level detector and an aircraft watertight compartment water level measurement system using the method. Background Art

[0002] When amphibious aircraft are operating on the water surface, due to the influence of the natural environment, aerodynamic characteristics and the sealing design of the watertight compartment structure, leakage water and condensed water will inevitably exist in the watertight compartment. After accumulation, it will affect the safety of the aircraft's center of gravity. In order to ensure the safety and reliability of the aircraft's flight on the water surface, the water ingress of the watertight compartment must be monitored. Therefore, the layout design of the water level detector is particularly important.

[0003] In order to quickly detect the warning boundary specified by the watertight design requirements, the water level detector is generally placed at the lowest point of the watertight compartment structure. When the aircraft is flying in a pitch attitude, the accumulated water flows and gathers in the direction of the flight pitch angle. When the position of the water level detector is consistent with the tilt direction of the accumulated water, the accumulation of water triggers an alarm. The amount of water entering is much lower than the alarm value of water inflow in the horizontal attitude, which is a false alarm and affects the aircraft's attendance rate; when the position of the water level detector is opposite to the tilt direction of the accumulated water, the amount of water entering exceeds the alarm value of water inflow in the horizontal attitude and cannot be detected, affecting the safety of the aircraft's center of gravity. Summary of the invention

[0004] In order to solve the problems existing in the installation position of traditional water level detectors, the purpose of the present invention is to provide a design method for a watertight compartment water level detector and an aircraft watertight compartment water level measurement system, which optimizes the layout design of the water level detector through the aircraft hull shape, watertight compartment distribution, maximum allowable water inflow into the watertight compartment and changes in the aircraft's surface operation posture, thereby improving the accuracy and practicality of monitoring the watertight compartment water inflow.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A design method for a watertight compartment water level detector, the method comprising the following steps:

[0007] According to the hull shape and watertight compartment distribution of the aircraft, a CATIA digital model of the watertight compartment is established;

[0008] Calculate and determine the center of gravity safety margin value;

[0009] Carry out weight and balance calculations on water inflow into watertight compartments to determine the maximum allowable water inflow into each watertight compartment;

[0010] According to the final determined maximum allowable water inflow of each watertight compartment, the water level of each watertight compartment with the maximum allowable water inflow when the aircraft is in a horizontal attitude is simulated on the CATIA digital model. This water level is the alarm water inflow line of the water level detector in the watertight compartment;

[0011] The warning water inlet line of the aircraft in the horizontal attitude is used as the height position reference of the water level detector in the watertight compartment;

[0012] The intersection position when the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum pitch attitude are consistent is determined as the heading position of the water level detector at the front of the watertight compartment;

[0013] The intersection position when the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum elevation attitude are consistent is determined as the heading position of the water level detector at the rear of the watertight compartment;

[0014] After determining the height position and heading position of the water level detector in the watertight compartment, determine the spanwise position of the water level detector in the watertight compartment. The spanwise position is selected on the symmetrical surface of the aircraft bottom.

[0015] According to a design method of a watertight compartment water level detector provided by the present invention, when determining the heading position of the water level detector at the front of the watertight compartment, according to the pitch angle limit of the aircraft on the water surface, the total warning water inflow of the aircraft at the maximum pitch angle attitude is calculated and determined to be ≤ the total warning water inflow in the horizontal attitude, and the warning waterline of the watertight compartment at the maximum pitch angle attitude of the aircraft is determined on the CATIA digital model of the watertight compartment;

[0016] By comparing the warning water inflow when the aircraft is at its horizontal attitude and at its maximum pitch angle, the intersection position when the two are consistent is determined, which is the heading position of the water level detector at the front of the watertight compartment.

[0017] According to a design method of a watertight compartment water level detector provided by the present invention, when determining the heading position of the water level detector at the rear of the watertight compartment, according to the finally determined aircraft surface pitch angle limit, the total warning water inflow amount of the aircraft at the maximum elevation attitude is calculated and determined to be ≤ the total warning water inflow amount at the horizontal attitude, and the warning waterline of the watertight compartment at the maximum elevation attitude of the aircraft is determined on the watertight compartment CATIA digital model;

[0018] By comparing the warning water inflow of the aircraft's horizontal attitude and maximum elevation attitude, the intersection position when the two are consistent is determined, which is the heading position of the water level detector at the rear of the watertight compartment.

[0019] According to a design method of a watertight compartment water level detector provided by the present invention, the establishment of a CATIA digital model of the watertight compartment comprises:

[0020] According to the CATIA appearance digital model of the aircraft, the basic geometric model of the hull is extracted. According to the basic geometric model of the hull and the distribution of watertight compartments, the hull is segmented by generating planes to form the geometric models of each watertight compartment. After segmentation, the CATIA part design module is used to generate the CATIA digital model of the watertight compartment.

[0021] According to a design method for a watertight compartment water level detector provided by the present invention, the calculation and determination of the center of gravity safety margin value includes:

[0022] The center of gravity safety margin value is determined based on the aircraft's weight center of gravity envelope and the preset center of gravity tolerance range, where the aircraft's weight center of gravity envelope refers to the envelope of all center of gravity positions allowed for use in civil aircraft during various flight phases, and the aircraft's weight center of gravity envelope range is determined by the aircraft's allowed forward and rear center of gravity limits; the preset range center of gravity tolerance is 7% of the entire center of gravity range.

[0023] According to a design method of a watertight compartment water level detector provided by the present invention, the step of determining the maximum allowable water inflow of each watertight compartment comprises:

[0024] Firstly, the size relationship between the center of gravity of each watertight compartment and the center of gravity of the empty aircraft is determined, and the center of gravity of the watertight compartment is divided into two data sets before and after the center of gravity of the empty aircraft. The volume coefficient ratio of each watertight compartment relative to the reference watertight compartment is determined according to the determined outer volume of the watertight compartment; using the volume coefficient ratio, the No. 1 watertight compartment is selected as the calculation basis, and the preliminary maximum allowable water inflow of each watertight compartment is defined. The center of gravity of the maximum allowable water inflow of each watertight compartment is determined on the CATIA numerical model. The weight and balance analysis of water inflow before and after the center of gravity of the watertight compartment is carried out in combination with the data sets before and after the center of gravity of the watertight compartment. The calculation is iterated until the allowable value Δx of the safety center of gravity margin is met, and finally the maximum allowable water inflow of each watertight compartment is determined.

[0025] According to a design method for a watertight compartment water level detector provided by the present invention, the height position of the water level detector in the watertight compartment is positively correlated with the maximum allowable water inflow into the watertight compartment. The greater the maximum allowable water inflow, the higher the height position of the water level detector in the watertight compartment.

[0026] According to a design method for a watertight compartment water level detector provided by the present invention, fluid dynamics software is used to dynamically simulate the water flow conditions of the watertight compartment at different attitude angles to more accurately predict the water inflow conditions and liquid level changes.

[0027] A water level measurement system for an aircraft watertight compartment comprises: a water level detector, a watertight cable, a water level computer, and a watertight compartment. The water level detector is arranged inside the watertight compartment by using the design method of a watertight compartment water level detector as claimed in claim 1, and is connected to the water level computer through the watertight cable to detect the water level of the watertight compartment; the watertight compartment is distributed on the bottom of the aircraft, and two water level detectors are arranged in a single watertight compartment, which are arranged at the front and rear of the watertight compartment respectively along the heading of the aircraft to cover and measure the water inlet level of the watertight compartment at different attitude angles of the aircraft; the watertight cable is installed and fixed on the watertight compartment wall plate; the water level signal of the water level detector is sent to the water level computer in real time, and the water level computer processes the water level signal in real time.

[0028] According to the aircraft watertight compartment water level measurement system provided by the present invention, the watertight cable is installed and fixed on the watertight bulkhead plate through a bracket and a clamp.

[0029] It can be seen that the present invention has the following beneficial effects:

[0030] 1. The present invention establishes an accurate model of the watertight compartment through the CATIA digital model, which can highly restore the actual structure of the aircraft and ensure the accuracy of subsequent calculations and analysis.

[0031] 2. The present invention optimizes the layout design of the water level detector by considering the aircraft hull shape, the distribution of watertight compartments, the maximum allowable water inflow into the watertight compartments and the changes in the aircraft's surface operation posture, thereby improving the accuracy and practicality of monitoring the water inflow into the watertight compartments.

[0032] 3. The present invention avoids the traditional arrangement of the water level detector at the lowest point of the watertight compartment structure, thereby minimizing false alarms and missed alarms, and avoiding the problem that when the water level detector is located in the opposite direction of the water inclination, the water inflow exceeding the alarm value cannot be detected.

[0033] 4. The method of the present invention not only considers the warning water inflow line of the aircraft in the horizontal attitude, but also considers the warning water inflow volume of the aircraft in the attitudes of maximum pitch angle and maximum elevation angle, ensuring that the water level detector can accurately reflect the water inflow situation of the watertight compartment in different flight attitudes. By simulating on the CATIA digital model, the water level changes in various parts and attitudes of the aircraft are fully considered, making the design of the water level detector more comprehensive and systematic.

[0034] 5. After the height position, heading position and span position of the water level detector are determined, the present invention can directly guide the actual installation work, thereby improving the feasibility of the design.

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a flow chart of a design method embodiment of a watertight compartment water level detector.

[0037] Figure 2 The present invention is a schematic structural diagram of an embodiment of a water level measurement system for a watertight compartment of an aircraft. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] See also Figure 1 The present invention provides a design method for a watertight compartment water level detector, the method comprising the following steps:

[0041] Step S1, establishing a CATIA digital model of the watertight compartment according to the hull shape and watertight compartment distribution of the aircraft;

[0042] Step S2, calculating and determining the center of gravity safety margin value;

[0043] Step S3, performing weight and balance calculation on the water inflow into the watertight compartments to determine the maximum allowable water inflow into each watertight compartment;

[0044] Step S4, based on the maximum allowable water inflow of each watertight compartment finally determined, simulate the water level of the maximum allowable water inflow of each watertight compartment in the horizontal posture of the aircraft on the CATIA digital model, and the water level is the alarm water inflow line of the water level detector in the watertight compartment;

[0045] Step S5, using the warning water inlet line of the aircraft in the horizontal posture as the height position reference of the water level detector in the watertight compartment;

[0046] Step S6, determining the intersection position of the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum pitch attitude as the heading position of the water level detector at the front of the watertight compartment;

[0047] Step S7, determining the intersection position of the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum elevation attitude as the heading position of the water level detector at the rear of the watertight compartment;

[0048] Step S8, after determining the height position and heading position of the water level detector in the watertight compartment, determine the spanwise position of the water level detector in the watertight compartment, and the spanwise position is selected on the symmetric plane of the aircraft bottom.

[0049] In the above step S1, a CATIA digital model of the watertight compartment is established, including:

[0050] According to the CATIA shape digital model of the aircraft, the basic geometric model (skeleton model) of the hull is extracted, which is generally composed of points, lines, planes, patches, coordinate systems, parts, etc. According to the basic geometric model of the hull and the distribution of watertight compartments, the hull is segmented by generating planes to form the geometric models of each watertight compartment. After segmentation, the CATIA part design module is used to generate the CATIA digital model of the watertight compartment.

[0051] Specifically, first use CATIA's import function (such as "Import Geometry" in "Import" or "Digital Mock-Up") to import the preliminary geometric data of the hull into CATIA. In CATIA, use modules such as "Generative Shape Design" to build a basic geometric model of the hull based on the imported geometric data or manually entered data. This may include the drawing of key lines such as the hull contour line, deck line, and bottom line. Determine the distribution and size of watertight compartments based on the ship design drawings or specifications. Watertight compartments are usually located in the lower part of the hull and are used to separate different compartments to improve the ship's anti-sinking performance.

[0052] Then, using CATIA's "Generative Structural Design" or "Multi-Body Design" modules, the corresponding segmentation planes are generated on the basic geometric model of the hull according to the distribution of watertight compartments. These planes divide the hull into different watertight compartment areas.

[0053] Using CATIA's segmentation tool, the basic hull geometry model is segmented into multiple independent watertight compartment geometry models according to the generated segmentation planes. Switch to CATIA's "Part Design" module to further refine the design of each segmented watertight compartment geometry model. Use commands such as "Pad", "Pocket", and "Shaft" to add or modify the structural details of the watertight compartment, such as bulkhead thickness, stiffeners, etc., and define the necessary attribute information for each watertight compartment's CATIA digital model, such as compartment name, size, material, etc.

[0054] Finally, use CATIA's annotation function to add necessary comments and instructions to the model, save the completed CATIA digital model of each watertight compartment to the specified location, and prepare for subsequent manufacturing, assembly or simulation analysis.

[0055] In the above step S2, calculating and determining the center of gravity safety margin value includes:

[0056] The center of gravity safety margin value is determined based on the aircraft's weight center of gravity envelope and the preset center of gravity tolerance range, where the aircraft's weight center of gravity envelope refers to the envelope of all center of gravity positions allowed for use in civil aircraft during various flight phases, and the aircraft's weight center of gravity envelope range is determined by the aircraft's allowed forward and rear center of gravity limits; the preset range center of gravity tolerance is 7% of the entire center of gravity range.

[0057] Specifically, the weight center of gravity envelope of the aircraft is determined by the front and rear center of gravity limits allowed for the aircraft. These two limit positions are the farthest boundaries allowed for the center of gravity of the aircraft in flight. For example, the weight center of gravity envelope of a certain type of aircraft is 10% to 30% MAC. The preset center of gravity tolerance range can be determined by the center of gravity tolerance limit required by airworthiness regulations. According to airworthiness regulations, such as CCAR25, the tolerance of the center of gravity of the aircraft is generally ±7% of the center of gravity range of the aircraft of this type. For example, the calculated center of gravity safety margin value is (30-10)*7%=1.4% MAC.

[0058] In the above step S3, the maximum allowable water inflow of each watertight compartment is determined, including:

[0059] Firstly, the size relationship between the center of gravity of each watertight compartment and the center of gravity of the empty aircraft is determined, and the center of gravity of the watertight compartment is divided into two data sets before and after the center of gravity of the empty aircraft. The volume coefficient ratio of each watertight compartment relative to the reference watertight compartment is determined according to the determined outer volume of the watertight compartment; using the volume coefficient ratio, the No. 1 watertight compartment is selected as the calculation basis, and the preliminary maximum allowable water inflow of each watertight compartment is defined. The center of gravity of the maximum allowable water inflow of each watertight compartment is determined on the CATIA numerical model. The weight and balance analysis of water inflow before and after the center of gravity of the watertight compartment is carried out in combination with the data sets before and after the center of gravity of the watertight compartment. The calculation is iterated until the allowable value Δx of the safety center of gravity margin is met, and finally the maximum allowable water inflow of each watertight compartment is determined.

[0060] In the above steps S4 and S5, in the horizontal posture of the aircraft, the water level of the maximum allowable water inflow into the watertight compartment (i.e., the height position of the water level detector in the watertight compartment) is determined according to the volume of the maximum allowable water inflow (maximum allowable water inflow / water density). The maximum allowable water inflow of the aircraft refers to the maximum volume of water inflow that the aircraft can safely withstand under specific conditions (such as horizontal posture, specific flight phase, etc.). The height position of the water level detector needs to be determined according to the maximum allowable water inflow of the aircraft in the horizontal posture. Through reasonable setting and effective maintenance, it can be ensured that the water level detector can promptly issue an alarm when the aircraft is flooded and ensure the safety performance of the aircraft.

[0061] In the above step S6, when determining the heading position of the water level detector at the front of the watertight compartment, according to the pitch angle limit of the aircraft on the water surface, calculate and determine that the total alarm water inflow when the aircraft is at the maximum pitch angle attitude ≤ the total alarm water inflow in the horizontal attitude, and determine the alarm waterline of the watertight compartment at the maximum pitch angle attitude of the aircraft on the CATIA digital model of the watertight compartment; by comparing the horizontal attitude of the aircraft and the alarm water inflow of the aircraft at the maximum pitch angle attitude, determine the intersection position when the two are consistent, that is, the heading position of the water level detector at the front of the watertight compartment.

[0062] In the above step S7, when determining the heading position of the water level detector at the rear of the watertight compartment, according to the finally determined aircraft surface pitch angle limit, calculate and determine that the total alarm water inflow at the maximum elevation attitude of the aircraft is ≤ the total alarm water inflow at the horizontal attitude, and determine the alarm waterline of the watertight compartment at the maximum elevation attitude of the aircraft on the CATIA digital model of the watertight compartment; by comparing the alarm water inflow at the horizontal attitude and the maximum elevation attitude of the aircraft, determine the intersection position when the two are consistent, which is the heading position of the water level detector at the rear of the watertight compartment.

[0063] In this embodiment, the height position of the water level detector in the watertight compartment is positively correlated with the maximum allowable water inflow into the watertight compartment. The greater the maximum allowable water inflow, the higher the height position of the water level detector in the watertight compartment.

[0064] Furthermore, when watertight cables pass through surface bulkhead plates and bulkhead frames, watertight treatment should be performed to ensure the watertightness of the watertight compartment.

[0065] Furthermore, the height position of the water level detector in the watertight compartment is positively correlated with the maximum allowable water inflow into the watertight compartment. The greater the maximum allowable water inflow, the higher the height position of the water level detector in the watertight compartment.

[0066] Furthermore, the heading position of the water level detector in the watertight compartment is related to the pitch angle limit of the aircraft. The larger the pitch angle, the closer the water level detector is to the front and rear bulkheads of the watertight compartment.

[0067] Furthermore, considering other equipment or pipelines in the watertight compartment, if they interfere with the position of the water level detector, the position of the water level detector can be fine-tuned according to the total alarm water inflow at the maximum pitch angle < the total alarm water inflow in the horizontal attitude.

[0068] Furthermore, the liquid level detection in the aircraft watertight compartment is regulated to an expected warning water level range through the aircraft attitude angle limit. Among them, the aircraft attitude angle includes pitch, roll and yaw, which describe the spatial position and direction of the aircraft relative to the horizontal plane. When the aircraft attitude changes, the liquid level in the watertight compartment will also change accordingly, which is due to the redistribution of liquid caused by gravity and attitude angle changes.

[0069] Furthermore, the warning threshold and logic are dynamically adjusted according to the flight phase and attitude changes to reduce the occurrence of false alarms and missed alarms.

[0070] In this embodiment, fluid dynamics software is used to dynamically simulate the water flow conditions of the watertight compartment at different attitude angles to more accurately predict the water inflow conditions and liquid level changes.

[0071] In this embodiment, the entire system is simulated and tested in combination with the aircraft attitude control system and flight simulation software to verify the performance and accuracy of the water level detector in different flight phases and attitudes.

[0072] Specifically, the CATIA digital model of the watertight compartment is imported into the fluid dynamics software for meshing.

[0073] Set the physical properties of the fluid, such as density, viscosity, etc. For watertight compartment flooding simulation, water is usually selected as the fluid medium.

[0074] Set the boundary conditions of the watertight compartment, including the location, size, flow rate, etc. of the water inlet. At the same time, it is necessary to define the gravity direction of the watertight compartment at different attitude angles to simulate the water flow conditions under different attitudes.

[0075] Set the initial conditions for the simulation, such as initial liquid level, initial flow rate, etc.

[0076] Solution settings: Set the solver parameters in the fluid dynamics software, including the solution algorithm, number of iterations, convergence criteria, etc.

[0077] Run simulation: Start the simulation calculation, and the software will automatically solve the fluid dynamics equations to simulate the water flow in the watertight compartment at different attitude angles.

[0078] Monitoring process: During the simulation process, key indicators such as fluid flow and liquid level changes can be monitored in real time to ensure the accuracy of the simulation results.

[0079] After the simulation is completed, the post-processing function of the fluid dynamics software is used to visualize the results and generate graphs such as flow velocity vector diagrams and liquid level change curves.

[0080] Based on the simulation results, the water ingress and liquid level changes of the watertight compartment at different attitude angles are analyzed, and the sealing performance and anti-water ingress capability of the watertight compartment are evaluated.

[0081] Embodiment of a water level measurement system for aircraft watertight compartment

[0082] like Figure 2As shown, the present invention provides an aircraft watertight compartment water level measurement system, comprising: a water level detector, a watertight cable 3, a water level computer 4, and a watertight compartment 5. The water level detector is arranged inside the watertight compartment 5 using the above-mentioned design method of a watertight compartment water level detector, and is connected to the water level computer 4 through the watertight cable 3 to detect the water level of the watertight compartment 5; the watertight compartment 5 is distributed on the bottom of the aircraft, and two water level detectors are arranged in a single watertight compartment 5, which are arranged at the front and rear of the watertight compartment 5 along the heading of the aircraft, such as a water level detector 1 at the front of the watertight compartment and a water level detector 2 at the rear of the watertight compartment, so as to cover and measure the water inlet level of the watertight compartment 5 at different attitude angles of the aircraft; the watertight cable 3 is installed and fixed on the wall plate of the watertight compartment 5; the water level signal of the water level detector is sent to the water level computer 4 in real time, and the water level computer 4 processes the water level signal in real time.

[0083] Furthermore, the watertight cable 3 is fixed on the wall panel of the watertight compartment 5 by means of a bracket and a clamp, which can ensure a firm installation and prevent the cable from being loosened or damaged due to aircraft vibration or external impact.

[0084] Furthermore, two water level detectors are arranged in a single watertight compartment 5, respectively located at the front and rear of the watertight compartment 5, to ensure that the water level can be accurately measured at different attitude angles. This layout can effectively avoid measurement errors caused by changes in aircraft attitude (such as take-off and landing, fluctuations in waves).

[0085] Furthermore, you can choose a high-precision, high-sensitivity water level detector to ensure accurate measurement even when the water level changes slightly. Common sensors include ultrasonic water level gauges, pressure water level gauges, etc.

[0086] Furthermore, in order to ensure that the cable connector and the cabin penetration part have good waterproof performance, special waterproof connectors and sealing materials can be used to prevent moisture from penetrating and affecting data transmission and cable life.

[0087] Furthermore, the water level computer has the ability to process water level signals in real time, including data acquisition, conversion, analysis and storage, etc. It uses a high-speed processor and a stable operating system to ensure processing speed and stability.

[0088] Furthermore, by setting a reasonable alarm threshold, when the water level exceeds the preset value, the system can automatically send out an alarm signal to prompt the crew to take corresponding measures.

[0089] In summary, the present invention establishes an accurate model of the watertight compartment through the CATIA digital model, which can highly restore the actual structure of the aircraft and ensure the accuracy of subsequent calculations and analyses. The present invention optimizes the layout design of the water level detector through the aircraft hull shape, the distribution of the watertight compartment, the maximum allowable water inflow of the watertight compartment and the change of the aircraft's surface operation posture, thereby improving the accuracy and practicality of monitoring the water inflow of the watertight compartment.

[0090] The present invention avoids the traditional arrangement of the water level detector at the lowest point of the watertight compartment structure, reduces false alarms and missed alarms as much as possible, and avoids the problem that when the water level detector is located in the opposite direction of the water accumulation inclination, the water inflow exceeding the warning value cannot be detected. The method of the present invention not only considers the warning water inflow line of the aircraft in the horizontal attitude, but also considers the warning water inflow volume of the aircraft in the attitudes of the maximum depression angle and the maximum elevation angle, ensuring that the water level detector can accurately reflect the water inflow situation of the watertight compartment in different flight attitudes.

[0091] The present invention simulates on the CATIA digital model, comprehensively considers the water level changes in various parts and postures of the aircraft, and makes the design of the water level detector more comprehensive and systematic. After determining the height position, heading position and span position of the water level detector, the present invention can directly guide the actual installation work, thereby improving the feasibility of the design.

[0092] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A design method for a watertight compartment water level detector. It is characterized in that The method comprises the following steps: According to the hull shape and watertight compartment distribution of the aircraft, a CATIA digital model of the watertight compartment is established; Calculate and determine the center of gravity safety margin value; Carry out weight and balance calculations on water inflow into watertight compartments to determine the maximum allowable water inflow into each watertight compartment; According to the final determined maximum allowable water inflow of each watertight compartment, the water level of each watertight compartment with the maximum allowable water inflow when the aircraft is in a horizontal attitude is simulated on the CATIA digital model. This water level is the alarm water inflow line of the water level detector in the watertight compartment; The warning water inlet line of the aircraft in the horizontal attitude is used as the height position reference of the water level detector in the watertight compartment; The intersection position when the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum pitch attitude are consistent is determined as the heading position of the water level detector at the front of the watertight compartment; The intersection position when the horizontal attitude of the aircraft and the warning water inflow amount of the aircraft at the maximum elevation attitude are consistent is determined as the heading position of the water level detector at the rear of the watertight compartment; After determining the height position and heading position of the water level detector in the watertight compartment, determine the spanwise position of the water level detector in the watertight compartment. The spanwise position is selected on the symmetrical surface of the aircraft bottom.

2. The method according to claim 1, Features: When determining the heading position of the water level detector at the front of the watertight compartment, according to the pitch angle limit of the aircraft on the water surface, calculate and determine that the total water inflow warning amount at the maximum pitch angle of the aircraft is ≤ the total water inflow warning amount at the horizontal attitude, and determine the warning waterline of the watertight compartment at the maximum pitch angle of the aircraft on the CATIA digital model of the watertight compartment; By comparing the warning water inflow when the aircraft is at its horizontal attitude and at its maximum pitch angle, the intersection position when the two are consistent is determined, which is the heading position of the water level detector at the front of the watertight compartment.

3. The method according to claim 1, Features: When determining the heading position of the water level detector at the rear of the watertight compartment, according to the final determined aircraft pitch angle limit on the water surface, calculate and determine that the total warning water inflow at the maximum elevation attitude of the aircraft is ≤ the total warning water inflow at the horizontal attitude, and determine the warning waterline of the watertight compartment at the maximum elevation attitude of the aircraft on the CATIA digital model of the watertight compartment; By comparing the warning water inflow of the aircraft's horizontal attitude and maximum elevation attitude, the intersection position when the two are consistent is determined, which is the heading position of the water level detector at the rear of the watertight compartment.

4. The method according to claim 1, It is characterized in that The CATIA digital model of the watertight compartment is established, including: According to the CATIA appearance digital model of the aircraft, the basic geometric model of the hull is extracted. According to the basic geometric model of the hull and the distribution of watertight compartments, the hull is segmented by generating planes to form the geometric models of each watertight compartment. After segmentation, the CATIA part design module is used to generate the CATIA digital model of the watertight compartment.

5. The method according to claim 1, It is characterized in that The calculation and determination of the center of gravity safety margin value includes: The center of gravity safety margin value is determined based on the aircraft's weight center of gravity envelope and the preset center of gravity tolerance range, where the aircraft's weight center of gravity envelope refers to the envelope of all center of gravity positions allowed for use in civil aircraft during various flight phases, and the aircraft's weight center of gravity envelope range is determined by the aircraft's allowed forward and rear center of gravity limits; the preset range center of gravity tolerance is 7% of the entire center of gravity range.

6. The method according to claim 5, It is characterized in that Determining the maximum allowable water inflow of each watertight compartment includes: Firstly, the size relationship between the center of gravity of each watertight compartment and the center of gravity of the empty aircraft is determined, and the center of gravity of the watertight compartment is divided into two data sets before and after the center of gravity of the empty aircraft. The volume coefficient ratio of each watertight compartment relative to the reference watertight compartment is determined according to the determined outer volume of the watertight compartment; using the volume coefficient ratio, the No. 1 watertight compartment is selected as the calculation basis, and the preliminary maximum allowable water inflow of each watertight compartment is defined. The center of gravity of the maximum allowable water inflow of each watertight compartment is determined on the CATIA numerical model. The weight and balance analysis of water inflow before and after the center of gravity of the watertight compartment is carried out in combination with the data sets before and after the center of gravity of the watertight compartment. The calculation is iterated until the allowable value Δx of the safety center of gravity margin is met, and finally the maximum allowable water inflow of each watertight compartment is determined.

7. The method according to any one of claims 1 to 6, Features: The height position of the water level detector in the watertight compartment is positively correlated with the maximum allowable water inflow into the watertight compartment. The greater the maximum allowable water inflow, the higher the height position of the water level detector in the watertight compartment.

8. The method according to any one of claims 1 to 6, Features: Fluid dynamics software is used to dynamically simulate the water flow in the watertight compartment at different attitude angles to more accurately predict the water ingress and liquid level changes.

9. An aircraft watertight compartment water level measurement system, It is characterized in that include: A water level detector, a watertight cable, a water level computer, and a watertight compartment. The water level detector is arranged inside the watertight compartment using the design method of a watertight compartment water level detector according to claim 1, and is connected to the water level computer through a watertight cable to detect the water level of the watertight compartment. The watertight compartments are distributed on the bottom of the aircraft, and two water level detectors are arranged in a single watertight compartment, which are arranged at the front and rear of the watertight compartment respectively along the heading of the aircraft to cover and measure the water level of the watertight compartment at different attitude angles of the aircraft; The watertight cable is installed and fixed on the watertight bulkhead plate; The water level signal of the water level detector is sent to the water level computer in real time, and the water level computer processes the water level signal in real time.

10. The system according to claim 9, Features: The watertight cable is installed and fixed on the watertight bulkhead plate through a bracket and a clamp.

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