Apparatus and method for simulating hot surface fires in aircraft engine core compartment lines

Abstract

This invention provides a device and experimental method for simulating hot surface fires in the piping of an aircraft engine core compartment. The core compartment simulator is constructed as a double-shell structure, forming a confined annular space. A hot surface module simulates piping heating conditions. A fuel leak module simulates fuel line leakage failure scenarios. A ventilation module introduces airflow at a preset velocity into the confined space. An eccentric adjustment module, located within the confined space, drives the hot surface module to generate axial deflection to simulate changes in piping space constraints during engine operation. A data monitoring and control module includes a thermocouple array, a thermal radiometer, and a collaborative control system. The collaborative control system inputs data from the temperature sensor, fuel leak module, ventilation module, and thermocouple array into an embedded near-field vapor concentration prediction model, and adjusts the temperature controller or ventilation module in response to the near-field vapor concentration output by the prediction model, bringing the near-field vapor concentration close to the ignition critical threshold.

Description

Technical Field

[0001] This invention relates to the field of aircraft fire prevention and airworthiness certification testing technology, and more specifically, to a device and method for simulating fires on the hot surface of pipelines inside an aircraft engine core compartment. Background Technology

[0002] With the continuous advancement of globalization, the civil aviation transportation industry has maintained rapid and sustained development, and the scale of air transport has been constantly expanding. Against this backdrop, the operational safety of civil aircraft has received increasing attention. Among these incidents, aircraft fires account for a significant proportion of all flight safety incidents; once they occur, they often cause serious casualties and equipment damage, posing a major threat to flight safety.

[0003] In civil aircraft structures, high-temperature pipelines are widely distributed in areas such as the engine nacelle, auxiliary power unit nacelle, engine pylons, and wing areas. These areas are constantly exposed to high temperatures during engine or auxiliary power unit operation, making them typical sources of fire risk. During aircraft operation, if flammable liquids leak due to pipeline damage, joint failure, or aging seals and come into contact with high-temperature pipelines, the fuel will rapidly evaporate under the high temperature, forming flammable vapors. These vapors then mix with the surrounding air above the hot surface to form a flammable mixture. Under the continuous heating of the hot surface, this flammable mixture may be ignited by the hot surface of the pipelines, leading to a fire or even an explosion, seriously threatening the structural integrity of the aircraft and flight safety. Therefore, in-depth research into the evaporation, diffusion, and ignition characteristics of fuel leaking into high-temperature pipelines under real aircraft cabin conditions is of significant engineering practical value and theoretical importance for revealing the formation mechanism of tubular hot surface fires, establishing ignition critical criteria under different operating conditions, and improving relevant design guidelines and quantitative safety margin indicators in civil aircraft airworthiness certification.

[0004] In related technologies, research on fires caused by high-temperature hot surfaces largely focuses on idealized planar high-temperature hot surfaces and is usually conducted in open environments without significant spatial constraints. This makes it difficult to reflect the actual high-temperature piping configurations, cabin space constraints, flight vibrations, and the influence of wall thermal environments within aircraft. Existing research methods struggle to simultaneously consider key factors such as the tubular geometry of high-temperature piping, the complex ventilation and airflow environment within the cabin during aircraft operation, and the three-dimensional diffusion and accumulation behavior of fuel vapors under confined space conditions. This results in significant deficiencies in the representativeness of related research findings for engineering applications and actual operating conditions. Therefore, it is necessary to design and construct an engineering-representative fire simulation experimental device based on the actual geometric characteristics of high-temperature piping within civil aircraft cabins and the typical confined space operating environment conditions, and to develop corresponding experimental methods to meet the practical needs of fire safety airworthiness certification and engineering verification. Summary of the Invention

[0005] In view of this, the present invention provides a device and experimental method for simulating a fire on the hot surface of pipelines in the core compartment of an aircraft engine. The device simulates the characteristics of the hot surface of the high-temperature pipelines in the core compartment of an aircraft engine and the evaporation and ignition process after fuel leakage through a core compartment simulator, a hot surface module, a fuel leakage module, a ventilation module and an eccentric adjustment module. At the same time, a collaborative control system is used to perform continuous feedback adjustment based on a predictive model.

[0006] To achieve the above objectives, the present invention provides a thermal surface fire simulation device for pipelines within an aircraft engine core compartment, comprising a core compartment simulator constructed as a double-shell structure with an annular confined space; a thermal surface module for simulating pipeline heating conditions, including: a tubular base located within the confined space for simulating pipeline structural features; multiple heating units disposed within the tubular base along its circumferential direction for heating the tubular base; multiple temperature sensors disposed within the tubular base along its circumferential direction for monitoring the temperature of the tubular base at different circumferential positions; a temperature controller for adjusting the heating power of the heating units based on the temperature information from the temperature sensors, thereby forming a preset temperature field on the outer surface of the tubular base; a fuel leakage module for simulating fuel pipeline leakage failure scenarios, including: a fuel injection device configured to output fuel at a preset flow rate; a fuel injection line with its inlet end connected to the fuel injection device and its outlet end extending into the confined space for guiding fuel to spread along the outer surface of the tubular base; and a ventilation module for... An airflow at a preset velocity is introduced into the confined space. The oil outlet is constructed with an arc-shaped skirt structure to reduce the impact of airflow during fuel slippage and increase the contact area between the fuel and the hot air above the tubular base. An eccentric adjustment module, located within the confined space, drives the tubular base to rotate around an axis extending vertically, thereby changing the airflow cross-section of the windward and leeward sides of the tubular base, thus simulating the changes in pipeline space constraints caused by thermal expansion and contraction or vibration during engine operation. A data monitoring and control module includes: a thermocouple array for monitoring the temperature above the tubular base and the spatial distribution of temperature during fuel combustion; a thermal radiation meter for monitoring the external thermal radiation intensity of the tubular base and fuel combustion; and a collaborative control system for inputting the data parameters from the temperature sensor, the fuel leakage module, the ventilation module, and the thermocouple array into an embedded near-field vapor concentration prediction model, and adjusting the temperature controller or the ventilation module in response to the near-field vapor concentration output by the prediction model, so that the near-field vapor concentration approaches the ignition critical threshold.

[0007] According to an embodiment of the present invention, the tubular base is made of 310S stainless steel, and the ratio of axial length to cross-sectional radius is in the range of 4:1 to 6:1. The heating process of the tubular base is less than or equal to 10 minutes.

[0008] According to an embodiment of the present invention, the heating unit includes silicon carbide rods, and the temperature controller is configured to independently control the heating power of each silicon carbide rod to compensate for heat loss caused by airflow convection heat transfer of the ventilation module.

[0009] According to an embodiment of the present invention, the core module simulator includes an inner shell and an outer shell arranged coaxially nested. The inner shell includes a small-diameter section and a gradually expanding section formed sequentially in the axial direction, and the outer shell includes a large-diameter section and a gradually narrowing section formed sequentially in the axial direction. The inner shell and the outer shell define the confined space.

[0010] According to an embodiment of the present invention, a plurality of thin-film heating units are provided on the inner wall surface of the aforementioned housing, and are configured to form a controllable wall surface temperature field not exceeding 400°C within the aforementioned confined space.

[0011] According to an embodiment of the present invention, the eccentric adjustment module includes: a first support frame disposed on the outer wall surface of the inner shell; a first motor mounted on the first support frame; a first lead screw adapted to rotate under the drive of the first motor; a support slider slidably mounted on the first support frame and threadedly connected to the first lead screw, the support slider being configured to be rotatably connected to one end of the tubular base; and a support protrusion disposed on the outer wall surface of the inner shell and configured to be rotatably connected to the other end of the tubular base, so that the tubular base rotates around the support protrusion under the drive of the support slider.

[0012] According to an embodiment of the present invention, the ventilation module includes: a centrifugal fan for generating an air volume of 600-1200 m³ / h. 3 / h, airflow with a wind pressure of 1500-4000 Pa; multiple ventilation ducts, an annular plate arranged vertically is connected between the inner shell and the outer shell, multiple air inlets are formed on the annular plate, one end of the ventilation duct is connected to the air inlet, and the other end is connected to the centrifugal fan, the side of the tubular base facing the air inlet is used as the windward side; preferably, a honeycomb grid is provided at the end of the ventilation duct connected to the air inlet, which is suitable for adjusting the turbulence intensity of the airflow entering the confined space.

[0013] According to an embodiment of the present invention, the thermocouple array includes three strings of thermocouple trees, respectively arranged above the center of the tubular base, at an axial distance of 10 cm above the center, and at a radial distance of 10 cm above the center. Each string of thermocouple trees is disposed on the inner wall surface of the outer shell and includes five K-type thermocouples evenly arranged at 2 cm intervals in the vertical direction. Two thermal radiometers are provided and suspended at 10 cm intervals in the horizontal direction on the inner wall surface of the outer shell, and the connection line between the two thermal radiometers passes through the center of the tubular base.

[0014] According to an embodiment of the present invention, the above-mentioned injection device includes: a second support frame; a second motor mounted on the second support frame; a second lead screw adapted to rotate under the drive of the second motor; a push block slidably mounted on the second support frame and threadedly connected to the second lead screw; and an injection syringe adapted to output fuel to the injection pipeline under the push of the push block.

[0015] According to an embodiment of the present invention, the above-mentioned near-field vapor concentration field prediction model is a reduced-order response surface model constructed based on computational fluid dynamics transient numerical simulation and intrinsic orthogonal decomposition technology; the above-mentioned cooperative control system is configured to take the temperature spatial distribution data obtained by the above-mentioned thermocouple array, the thermal radiation data obtained by the above-mentioned thermal radiation meter, the tubular base temperature obtained by the above-mentioned temperature sensor, the airflow velocity of the above-mentioned ventilation module, and the fuel leakage flow rate of the above-mentioned injection device as input parameters, output the three-dimensional distribution of fuel vapor concentration in the above-mentioned confined space within a second-level time scale, and automatically adjust the output power of the above-mentioned temperature controller or the airflow velocity of the above-mentioned ventilation module in a closed loop when the above-mentioned concentration approaches the ignition critical threshold.

[0016] According to an embodiment of the present invention, the core module simulator is provided with a viewing window made of high borosilicate fire-resistant glass, which is used to observe and record the oil film sliding path and ignition situation on the tubular base.

[0017] This invention also provides an experimental method based on the aircraft engine core compartment hot surface fire simulation device in any of the above embodiments. The experimental method includes: setting experimental scenario parameters according to the airworthiness certification requirements for fire prevention of leaking oil on the high-temperature hot surface in the aircraft engine core compartment, and calibrating the temperature sensor, injection device, and ventilation module; activating the eccentric adjustment module and inputting the engine vibration spectrum signal to drive the tubular base to periodically oscillate in the confined space; activating the ventilation module to introduce airflow into the confined space, and simultaneously activating the heating unit to heat the tubular base; the temperature controller adjusting the heating power according to the temperature feedback difference between the windward and leeward sides to establish the preset temperature field on the outer surface of the tubular base; and activating the injection device. Fuel is injected through an injection pipeline and spreads and evaporates on the outer surface of the tubular base via an arc-shaped skirt structure. Temperature spatial distribution data and thermal radiation data above the tubular base are acquired synchronously through a thermocouple array and a thermal radiation meter. The collaborative control system inputs the temperature spatial distribution data, thermal radiation data, base surface temperature, airflow parameters, and leakage flow rate into the near-field vapor concentration field prediction model to reconstruct the three-dimensional vapor concentration distribution field within the confined space. When the local concentration in the reconstructed three-dimensional vapor concentration distribution field approaches the ignition critical threshold, the collaborative control system automatically adjusts the output power of the temperature controller or the airflow parameters of the ventilation module to dynamically oscillate the experimental conditions within the critical range between ignition and non-ignition, and records the temperature, ventilation volume, and leakage rate data under the corresponding conditions.

[0018] The aircraft engine core compartment hot surface fire simulation device provided by this invention can simultaneously reproduce the high-temperature hot surface characteristics, tubular geometry, cabin space constraints, aircraft vibration and ventilation conditions of aircraft hot pipes. It reveals the evaporation, diffusion and ignition mechanism of fuel leakage onto the tubular hot surface under confined space conditions, and dynamically approximates the minimum hot surface ignition temperature and minimum ventilation volume, etc., of airworthiness quantitative indicators in hot surface ignition experiments. It provides experimental basis for the establishment of margin design criteria and related quantitative indicators in civil aircraft airworthiness certification documents. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the aircraft engine core compartment piping hot surface fire simulation device provided by an exemplary embodiment of the present invention;

[0020] Figure 2 This is a three-dimensional structural diagram of the thermal surface module provided by an exemplary embodiment of the present invention;

[0021] Figure 3 This is a perspective structural diagram of the fuel leak module provided by an exemplary embodiment of the present invention;

[0022] Figure 4This is a three-dimensional structural diagram of the core cabin simulator provided by an exemplary embodiment of the present invention;

[0023] Figure 5 This is a three-dimensional structural diagram of the outer shell of the core cabin simulator provided by an exemplary embodiment of the present invention, showing the thin-film heating unit;

[0024] Figure 6 This is a partial enlarged view of the tubular base in the aircraft engine core compartment hot surface fire simulation device provided by an exemplary embodiment of the present invention;

[0025] Figure 7 This is a flowchart of an experimental method provided by an exemplary embodiment of the present invention.

[0026] In the accompanying drawings, the meanings of the reference numerals are as follows:

[0027] 1. Core module simulator;

[0028] 11. Inner shell;

[0029] 12. Outer shell;

[0030] 121. Thin-film heating unit;

[0031] 13. Circular plate;

[0032] 131. Air intake;

[0033] 14. Visual window;

[0034] 2. Hot surface module;

[0035] 21. Tubular base;

[0036] 22. Heating unit;

[0037] 23. Temperature sensor;

[0038] 24. Temperature controller;

[0039] 3. Fuel leak module;

[0040] 31. Injection device;

[0041] 311. Second support frame;

[0042] 312. Second motor;

[0043] 313. Second lead screw;

[0044] 314. Push the block;

[0045] 315. Oil injection syringe;

[0046] 32. Oil injection pipeline;

[0047] 321. Curved skirt structure;

[0048] 4. Ventilation module;

[0049] 41. Centrifugal fan;

[0050] 42. Ventilation ducts;

[0051] 5. Eccentricity adjustment module;

[0052] 51. First support frame;

[0053] 52. First motor;

[0054] 53. First lead screw;

[0055] 54. Support slider;

[0056] 55. Support protrusion;

[0057] 6. Data monitoring and control module;

[0058] 61. Thermocouple array;

[0059] 611. Thermocouple tree;

[0060] 62. Thermal radiometer. Detailed Implementation

[0061] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0062] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0063] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0064] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0065] Figure 1 This is a three-dimensional structural diagram of the aircraft engine core compartment piping hot surface fire simulation device provided by an exemplary embodiment of the present invention. Figure 2 This is a three-dimensional structural diagram of the thermal surface module provided in an exemplary embodiment of the present invention. Figure 3 This is a perspective structural diagram of the fuel leak module provided in an exemplary embodiment of the present invention. Figure 4 This is a three-dimensional structural diagram of the core cabin simulator provided by an exemplary embodiment of the present invention. Figure 5 This is a three-dimensional structural diagram of the outer shell of the core cabin simulator provided by an exemplary embodiment of the present invention, showing the thin-film heating unit. Figure 6 This is a partial enlarged view of the tubular base in the aircraft engine core compartment hot surface fire simulation device provided by an exemplary embodiment of the present invention.

[0066] An exemplary embodiment of the present invention provides a device for simulating hot surface fires in piping within the core compartment of an aircraft engine, such as... Figures 1 to 5As shown, the system includes a core module 1, a hot surface module 2, a fuel leak module 3, a ventilation module 4, an eccentric adjustment module 5, and a data monitoring and control module 6. The core module 1 is constructed as a double-shell structure with an annular confined space. The hot surface module 2 simulates pipeline heating conditions and includes a tubular base 21, multiple heating units 22, multiple temperature sensors 23, and a temperature controller 24. The tubular base 21 is located within the confined space and simulates pipeline structural features. Multiple heating units 22 are arranged circumferentially within the tubular base 21 for heating it. Multiple temperature sensors 23 are arranged circumferentially within the tubular base 21 to monitor the temperature of the tubular base 21 at different circumferential positions. The temperature controller 24 adjusts the heating power of the heating units 22 based on the temperature information from the temperature sensors 23 to create a preset temperature field on the outer surface of the tubular base 21. The fuel leakage module 3 is used to simulate fuel pipeline leakage failure scenarios, including a fuel injection device 31 and a fuel injection line 32. The fuel injection device 31 is configured to output fuel at a preset flow rate. The inlet end of the fuel injection line 32 is connected to the fuel injection device 31, and the outlet end extends into the confined space, suitable for guiding fuel to spread along the outer surface of the tubular base 21. The ventilation module 4 is used to introduce airflow at a preset velocity into the confined space. The outlet end is configured with an arc-shaped skirt structure 321, suitable for reducing the impact of airflow during fuel sliding and increasing the contact area between fuel and the hot air above the tubular base 21. The eccentric adjustment module 5 is set in the confined space and is used to drive the tubular base 21 to rotate around an axis extending in the vertical direction, so as to change the airflow cross section of the windward and leeward sides of the tubular base 21, thereby simulating the changes in pipeline space constraints caused by thermal expansion and contraction or vibration during engine operation. The data monitoring and control module 6 includes a thermocouple array 61, a thermal radiation meter 62, and a cooperative control system. Thermocouple array 61 is used to monitor the temperature above tubular base 21 and the spatial distribution of temperature during fuel combustion. Thermal radiation meter 62 is used to monitor the external thermal radiation intensity of tubular base 21 and fuel combustion. The coordinated control system inputs data parameters from temperature sensor 23, fuel leakage module 3, ventilation module 4, and thermocouple array 61 into an embedded near-field vapor concentration prediction model, and adjusts the temperature controller 24 or ventilation module 4 in response to the near-field vapor concentration output by the prediction model, bringing the near-field vapor concentration close to the ignition critical threshold.

[0067] In this implementation, by constructing a double-shell annular confined space consistent with the geometry of a real engine core compartment, the three-dimensional accumulation and diffusion behavior of fuel vapor under complex spatial constraints can be realistically reproduced. The tubular base 21 simulates the geometry of typical high-temperature pipelines inside the engine. Its circumferentially distributed independent heating units 22 and temperature sensors 23, combined with the precise control of the temperature controller 24, ensure that accurate preset thermal boundary conditions can be maintained even in strong convection environments. The arc-shaped skirt structure 321 of the fuel leakage module 3 effectively solves the problems of fuel trajectory deviation and atomization under high-speed airflow, ensuring the formation of a stable oil film and allowing more fuel to contact the hot air above the tubular base 21. The eccentric adjustment module 5 introduces dynamic vibration factors, more comprehensively simulating actual operating conditions. The collaborative control system breaks through the bottleneck of the inability to obtain the invisible vapor concentration field in real time in traditional experiments. Through model prediction, it achieves active and adaptive approximation of the ignition critical boundary, thereby providing high-fidelity and quantitative key indicator data for airworthiness certification.

[0068] In some alternative embodiments, the preset temperature field is determined according to experimental requirements, for example, it may be a uniform circumferential temperature field or an offset temperature field.

[0069] In one exemplary embodiment, the tubular base 21 is made of 310S stainless steel, and the ratio of axial length to cross-sectional radius ranges from 4:1 to 6:1. The heating process of the tubular base 21 is less than or equal to 10 minutes.

[0070] In this implementation, 310S stainless steel possesses good oxidation resistance and mechanical strength, enabling it to withstand the high-temperature environment within the core module simulator 1 for extended periods. The length-to-diameter ratio range of 4:1 to 6:1 is determined based on the geometrical statistical characteristics of typical high-temperature gas source pipelines (such as high-pressure pipes and bleed air pipes) in civil aircraft, ensuring that the simulated hot surface has sufficient engineering representativeness in terms of geometry, accurately reflecting the constraint effect of the tubular structure on fuel spread path, evaporation area, and gas-solid heat transfer. By shortening the heating time, experimental time can be reduced, increasing efficiency.

[0071] In some optional embodiments, the tubular base 21 has at least eight mounting holes that are evenly spaced in the circumferential direction and extend in the axial direction for mounting the heating unit 22 to ensure heating uniformity.

[0072] According to an embodiment of this disclosure, the heating unit 22 includes silicon carbide rods, and the temperature controller 24 is configured to independently control the heating power of each silicon carbide rod to compensate for heat loss caused by airflow convection heat transfer from the ventilation module 4.

[0073] In this implementation, silicon carbide rods have advantages such as rapid heating, long service life, and resistance to deformation at high temperatures. After a high-speed airflow is introduced into the ventilation module, the convective heat transfer coefficient of the tubular base 21 on the windward side is significantly higher than that on the leeward side. By independently adjusting the power of each silicon carbide rod through the temperature controller 24, the additional heat loss on the windward side can be compensated in real time. Under dynamic airflow conditions, a uniform circumferential temperature field on the outer wall of the tubular base can be precisely maintained, or a specific non-uniform bias temperature field can be established according to experimental requirements, thereby ensuring the accuracy and controllability of thermal boundary conditions.

[0074] In one exemplary embodiment, such as Figure 4 As shown, the core module simulator 1 includes an inner shell 11 and an outer shell 12 arranged coaxially. The inner shell 11 includes a small-diameter section and a gradually expanding section formed sequentially in the axial direction, and the outer shell 12 includes a large-diameter section and a gradually narrowing section formed sequentially in the axial direction. A confined space is defined between the inner shell 11 and the outer shell 12.

[0075] In this implementation, the annular structure transitioning from a small-diameter section to a gradually expanding section is designed proportionally based on the actual geometry of an aero-engine core compartment, which features a compact front end and a gradually expanding rear end. Specifically, the small-diameter and large-diameter sections form the first part of the annular confined space, with a fixed width. The gradually expanding and contracting sections form the second part of the confined space, with the annular width gradually decreasing from the junction with the first part. This effectively replicates the axial acceleration and expansion characteristics of the airflow within the actual core compartment, as well as the impact of changes in the cross-sectional area of ​​the confined space on the three-dimensional diffusion, accumulation, and final ignition location of fuel vapor, resulting in experimental results with higher fidelity to actual operating conditions.

[0076] According to the disclosed embodiments, such as Figure 5 As shown, multiple thin-film heating units 121 are provided on the inner wall surface of the outer casing 12, which are configured to form a controllable wall surface temperature field not exceeding 400°C in the confined space.

[0077] In this implementation, when the engine is actually running, the core compartment wall will heat up due to radiation and conduction from nearby high-temperature components. A thin-film heating unit 121 is installed to simulate this background thermal environment.

[0078] The thin-film heating unit 121 is preferably a resistance heating film, uniformly distributed along the axial and / or circumferential directions and attached to the inner wall surface of the outer casing 12, directly heating the outer casing 12 after being energized. This is to study the influence of the hot wall surface on the evaporation of leaking fuel in the pipeline, and its impact on the stability of the vapor layer. The upper limit of 400℃ is set based on the typical core compartment wall temperature range, allowing the experiment to examine the interference of the wall thermal environment, an important coupling factor, on the ignition mechanism.

[0079] In one exemplary embodiment, such as Figure 6As shown, the eccentric adjustment module 5 includes a first support frame 51, a first motor 52, a first lead screw 53, a support slider 54, and a support protrusion 55. The first support frame 51 is disposed on the outer wall surface of the inner shell 11. The first motor 52 is mounted on the first support frame 51. The first lead screw 53 is adapted to rotate under the drive of the first motor 52. The support slider 54 is slidably mounted on the first support frame 51 and threadedly connected to the first lead screw 53. The support slider 54 is also configured to be rotatably connected to one end of the tubular base 21. The support protrusion 55 is disposed on the outer wall surface of the inner shell 11 and is configured to be rotatably connected to the other end of the tubular base 21, so that the tubular base 21 rotates around the support protrusion 55 under the drive of the support slider 54.

[0080] In this embodiment, the first support frame 51 is fixed to the inner shell 11. The first motor 52 is preferably a servo motor, which drives the first lead screw 53 to rotate, converting the rotational motion into linear translation of the support slider 54 along the lead screw axis. Since the support slider 54 is rotatably connected to the front end of the tubular base 21, and the rear support protrusion 55 is rotatably connected to the tubular base 21 as a fixed hinge point, when the support slider 54 moves back and forth, it will pull the front end of the tubular base 21 to swing, forcing the entire tubular base 21 to undergo axial angular deflection with the rear support protrusion 55 as the center. This kind of cooperation is highly reliable and has a fast response. By inputting a specific vibration spectrum signal to drive the servo motor, it can accurately simulate the dynamic eccentricity of the pipeline caused by engine vibration and thermal deformation, thereby changing the airflow cross section of the windward and leeward sides in real time.

[0081] Those skilled in the art will understand that, Figure 6 As shown, the first support frame 51 includes at least two mounting plates, one of which is used to fix the first motor 52, and the other supports the lead screw through a bearing seat. A guide rod parallel to the first lead screw 53 is connected between the two mounting plates and slides with the support slider 54 to limit the rotation of the support slider 54 with the first lead screw 53.

[0082] In one exemplary embodiment, such as Figure 1 As shown, the ventilation module 4 includes a centrifugal fan 41 and multiple ventilation ducts 42. The centrifugal fan 41 is used to generate an air volume of 600-1200 m³ / h. 3 The airflow has a pressure of 1500-4000 Pa per hour. An annular plate 13, arranged vertically, connects the inner shell 11 and the outer shell 12. Multiple air inlets 131 are formed on the annular plate 13. One end of the ventilation duct 42 is connected to the air inlet 131, and the other end is connected to the centrifugal fan 41. The side of the tubular base 21 facing the air inlet 131 serves as the windward side. Preferably, a honeycomb grille is provided at the end of the ventilation duct 42 connected to the air inlet, which is suitable for adjusting the turbulence intensity of the airflow entering the confined space.

[0083] In this implementation, the large volume and high pressure airflow provided by the centrifugal fan 41 can meet the airworthiness standards' requirements for the ventilation capacity of the core compartment. For example... Figure 1 As shown, the airflow passes through six ventilation ducts 42 and enters the confined space through six air inlets 131 arranged in a realistic layout on the annular plate 13. A honeycomb grid is set at the interface between the ventilation ducts 42 and the air inlets 131, which can effectively break up large-scale vortices in the airflow and generate a uniform airflow with controllable turbulence intensity, thereby simulating the actual ventilation environment of non-uniform and strongly turbulent flow inside the engine, making the diffusion process of fuel vapor in the experiment closer to the actual situation.

[0084] In some optional embodiments, the total ventilation volume is configured to be 0.2-0.4 kg / s, corresponding to a volumetric air volume of 600-1200 m³ / s. 3 / h, the wind speed at air inlet 131 ranges from 0 to 78 m / s, the total pressure ranges from 1500 to 4000 Pa, the rated power ranges from 2 kW to 22 kW, and the adjustment method is variable frequency speed control.

[0085] In one exemplary embodiment, such as Figure 1 and Figure 6 As shown, the thermocouple array 61 includes three strings of thermocouple trees 611, respectively arranged above the center of the tubular base 21, at an axial distance of 10 cm above the center, and at a radial distance of 10 cm above the center. Each string of thermocouple trees 611 is disposed on the inner wall surface of the outer casing 12 and includes five K-type thermocouples evenly arranged at 2 cm intervals in the vertical direction. Two thermal radiometers 62 are provided, suspended at 10 cm intervals in the horizontal direction on the inner wall surface of the outer casing 12, and the line connecting the two thermal radiometers 62 passes through the center of the tubular base 21.

[0086] In this implementation, three strings of thermocouples 611 form a spatial three-dimensional monitoring network, capturing temperature field changes directly above the leak point, axially downstream, and radially outward. Each string of thermocouples 611 is fixed to the inner wall of the outer casing 12 by a bracket, and the 2cm vertical spacing provides high spatial resolution near the wall and in the flame core area. Two radiometers 62 are fixed to the inner wall of the outer casing 12 by suspension, with their measuring probes facing the central area of ​​the tubular base 21 to accurately measure the dominant direction and intensity of radiation from the flame or hot surface, providing direct data for assessing the thermal threat of the fire to adjacent structures.

[0087] In some optional embodiments, the K-type thermocouple has a temperature measurement range of 0-1100°C. The thermal radiation meter 62 has a measurement range of 0-20 kW / m². 2 .

[0088] In one exemplary embodiment, such as Figure 1 and Figure 3As shown, the injection device 31 includes a second support frame 311, a second motor 312, a second lead screw 313, a pusher block 314, and an injection syringe 315. The second support frame 311 is mounted on the experimental platform. The second motor 312 is mounted on the second support frame 311. The second lead screw 313 is adapted to rotate under the drive of the second motor 312. The pusher block 314 is slidably mounted on the second support frame 311 and threadedly connected to the second lead screw 313. The injection syringe 315 is adapted to output fuel into the injection line 32 under the push of the pusher block 314.

[0089] In this embodiment, the second motor 312 drives the second lead screw 313 to rotate, converting the rotational motion into linear movement of the push block 314 along the second support frame 311. The push block 314 abuts against the piston tail of the injection syringe 315, pushing the piston to slide inside the syringe, thereby squeezing the fuel inside the syringe into the injection line 32 at a preset flow rate.

[0090] In some preferred embodiments, the second motor 312 is a servo motor.

[0091] In some preferred embodiments, the output flow rate of the injection syringe 315 ranges from 0 to 2 ml / s. The flow rate accuracy is ±0.01 ml / s, meeting the experimental requirements for multi-mode leakage, such as continuous leakage and pulsating leakage.

[0092] According to an embodiment of this disclosure, an injection probe with a buffer chamber is provided inside the injection line 32, and the arc-shaped skirt structure 321 is constructed as an arc-shaped patch made of high-temperature resistant metal material. After the fuel is depressurized by the buffer chamber, it leaks evenly to the surface of the tubular base 21 through the arc-shaped patch, thereby resisting the shearing damage of the oncoming airflow.

[0093] In one exemplary embodiment, the near-field vapor concentration field prediction model is a reduced-order response surface model constructed based on computational fluid dynamics transient numerical simulation and intrinsic orthogonal decomposition technology. The collaborative control system is configured to take the temperature spatial distribution data acquired by the thermocouple array 61, the thermal radiation data acquired by the thermal radiation meter 62, the temperature of the tubular base 21 acquired by the temperature sensor 23, the airflow velocity of the ventilation module 4, and the fuel leakage flow rate of the injection device 31 as input parameters, output the three-dimensional distribution of fuel vapor concentration in the confined space on a second-level time scale, and automatically adjust the output power of the temperature controller 24 or the airflow velocity of the ventilation module 4 in a closed loop when the concentration approaches the ignition critical threshold.

[0094] In this implementation, before the experiment begins, computational fluid dynamics software is used to simulate experimental scenarios under different combinations of tubular base 21 temperature, airflow velocity, and fuel leakage rate, collecting three-dimensional vapor concentration distribution data to form an initial database. Subsequently, mathematical dimensionality reduction techniques such as intrinsic orthogonal decomposition are used to compress the database, eliminate redundant information, and extract characteristic modes that represent the spatial distribution law of vapor concentration. Using temperature, wind speed, and leakage rate as input conditions and characteristic mode coefficients as output results, a model is trained to establish a nonlinear mapping model between macroscopic parameters and the microscopic flow field. During the experiment, the collaborative control system inputs real-time collected macroscopic parameters (such as the temperature of the tubular base 21, airflow velocity, leakage flow rate, temperature spatial distribution data obtained by the thermocouple array 61, and thermal radiation data obtained by the thermal radiation meter 62) into the trained reduced-order response surface model (ROM). This model can back-calculate and reconstruct the three-dimensional distribution field of fuel vapor concentration within the current confined space within seconds. Based on this, the system extracts the combustible concentration range, and once it approaches the ignition critical threshold, it immediately and automatically closes the loop to fine-tune the hot surface power or wind speed, achieving precise capture of the critical boundary.

[0095] In one exemplary embodiment, such as Figure 1 and Figure 4 As shown, the core module simulator 1 is equipped with a viewing window 14, which is made of high borosilicate fire-resistant glass and is used to observe and record the oil film sliding path and ignition situation on the tubular base 21.

[0096] In this implementation, high borosilicate glass has the advantages of low thermal expansion coefficient and high light transmittance, can withstand the high temperature environment inside the core compartment and is easy to observe.

[0097] In some optional embodiments, the viewing window 14 is 150 mm * 150 mm in size and is respectively arranged on the windward side of the tubular base 21, that is, on the annular plate 13, and on the side of the tubular base 21, that is, on the outer shell 12. This allows researchers to use optical instruments such as high-speed cameras to intuitively record dynamic images of the entire process of fuel spreading, evaporation, ignition and flame development, providing direct visual evidence for analyzing the ignition core location and flame morphology evolution.

[0098] Figure 7 This is a flowchart of an experimental method provided by an exemplary embodiment of the present invention.

[0099] Exemplary embodiments of this disclosure also provide an experimental method based on the aircraft engine core compartment piping hot surface fire simulation device in any of the above embodiments, such as... Figure 7 As shown, the method includes steps S1-S7.

[0100] Step S1: Set the experimental scenario parameters according to the airworthiness certification requirements for fire prevention of oil leakage from the high-temperature hot surface inside the core compartment of the aircraft engine, and perform accuracy calibration on the temperature sensor 23, the injection device 31, and the ventilation module 4.

[0101] Step S2: Start the eccentric adjustment module 5 and input the engine vibration spectrum signal to drive the tubular base 21 to oscillate periodically in the confined space.

[0102] Step S3: Activate the ventilation module 4 to introduce airflow into the confined space, and simultaneously activate the heating unit 22 to heat the tubular base 21. The temperature controller 24 adjusts the heating power according to the temperature feedback difference between the windward and leeward sides to establish a preset temperature field on the outer surface of the tubular base 21.

[0103] Step S4: Start the injection device 31. Fuel spreads and evaporates on the outer surface of the tubular base 21 by relying on the arc-shaped skirt structure 321 through the injection pipeline 32.

[0104] Step S5: Simultaneously acquire temperature spatial distribution data and thermal radiation data above the tubular base 21 through thermocouple array 61 and thermal radiation meter 62.

[0105] Step S6: The collaborative control system inputs the spatial temperature distribution data, thermal radiation data, base surface temperature, airflow parameters and leakage flow rate into the near-field vapor concentration field prediction model to reconstruct the three-dimensional vapor concentration distribution field in the confined space.

[0106] Step S7: When the local concentration in the reconstructed three-dimensional vapor concentration distribution field approaches the ignition critical threshold, the collaborative control system automatically adjusts the output power of the temperature controller 24 or the airflow parameters of the ventilation module 4 to make the experimental conditions dynamically oscillate within the critical range between ignition and non-ignition, and records the temperature, ventilation volume and leakage rate data under the corresponding conditions.

[0107] More specifically, in step S1, corresponding experimental scenarios are comprehensively designed to meet the quantitative requirements of the minimum hot surface ignition temperature and minimum ventilation volume for fire prevention and airworthiness certification of oil leakage from high-temperature hot surfaces in the core compartment of the aircraft engine. The temperature sensor 23 and the injection device 31 are calibrated, with the measurement error of the temperature sensor 23 within ±1℃ and the output flow control accuracy of the injection device 31 within ±0.01ml / s. The wind speed measuring device at the air outlet of the ventilation module 4 is calibrated to achieve a wind speed measurement accuracy of ±0.1 m / s.

[0108] The digital twin environment and eccentricity preset are then initialized. The pre-built computational fluid dynamics reduced-order response surface model is then imported into the cooperative control system.

[0109] In step S2, the eccentricity adjustment module 5 is activated, and the vibration spectrum signal of the real aero-engine under specific operating conditions is input to drive the tubular base 21 to continuously deflect axially within the core cabin simulator 1, thereby establishing a dynamically changing windward surface of the tubular base 21.

[0110] In step S3, the ventilation module 4 is activated to output airflow at a preset velocity, and the heating unit 22 is turned on simultaneously. Based on feedback from multiple temperature sensors 23, the temperature controller 24 automatically increases the output power of the heating unit 22 on the windward side to address the heat loss caused by strong convective heat transfer on the windward side due to airflow, thereby maintaining a preset non-uniform circumferential temperature field on the outer wall of the tubular base 21 in a dynamic airflow environment.

[0111] In step S4, the injection device 31 is activated, causing the fuel to be depressurized in the buffer chamber inside the injection pipeline 32 and then seep out along the arc-shaped skirt structure 321. Under the shearing action of the lateral airflow formed by the ventilation module 4, the fuel relies on the arc-shaped skirt structure to resist trajectory deviation, and expands and evaporates along the outer wall of the tubular base 21 in a stable oil film form.

[0112] In step S5, during the fuel evaporation process, data such as the temperature of the tubular base 21, the temperature field above the tubular base 21, thermal radiation, and wind speed are collected.

[0113] In step S6, the cooperative control system uses a built-in reduced-order response surface model (ROM) to transform macroscopic measurement data into a three-dimensional distribution field of local vapor concentration that is invisible in the confined space within a second-level period.

[0114] In step S7, when the collaborative control system predicts that the local vapor concentration is approaching the critical ignition threshold, it automatically triggers the feedback adjustment mechanism to fine-tune the fuel leakage rate, the power of the temperature controller 24 (i.e., the power of the heating unit 22), or the airflow velocity, causing the system to oscillate repeatedly in the critical state between ignition and non-ignition. Finally, the system automatically records the minimum ignition temperature, corresponding ventilation volume, and fuel leakage rate of the critical ignition range, and outputs quantitative indicators for fire protection and airworthiness certification based on safety margin design criteria.

[0115] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0116] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A device for simulating hot surface fires in piping within the core compartment of an aircraft engine, characterized in that, include: The core module simulator is constructed as a double-shell structure, forming a ring-shaped confined space; A hot surface module, used to simulate piping heating conditions, includes: A tubular base, located within a confined space, is used to simulate the structural characteristics of pipelines; Multiple heating units are arranged inside the tubular base along the circumferential direction of the tubular base, and are suitable for heating the tubular base; Multiple temperature sensors are disposed within the tubular base along the circumferential direction to monitor the temperature of the tubular base at different circumferential positions; A temperature controller is used to adjust the heating power of the heating unit according to the temperature information from the temperature sensor, so as to form a preset temperature field on the outer surface of the tubular base; The fuel leak module is used to simulate fuel line leak failure scenarios, including: The injection device is configured to output fuel at a preset flow rate; The oil injection line has an inlet end connected to the injection device and an outlet end extending into the confined space, which is suitable for guiding fuel to spread along the outer surface of the tubular base. A ventilation module is used to introduce airflow at a preset flow rate into a confined space. The oil outlet is constructed with an arc-shaped skirt structure, which is suitable for reducing the impact of airflow during fuel sliding and increasing the contact area between fuel and hot air above the tubular base. An eccentric adjustment module, set within a confined space, is used to drive the tubular base to rotate around an axis extending vertically, thereby changing the airflow cross-section of the windward and leeward sides of the tubular base, thus simulating the changes in pipeline space constraints caused by thermal expansion and contraction or vibration during engine operation. The data monitoring and control module includes: A thermocouple array is used to monitor the temperature above the tubular base and the spatial distribution of temperature during fuel combustion. A thermal radiation meter is used to monitor the intensity of external thermal radiation emitted by the tubular base during fuel combustion. The collaborative control system is used to input the data parameters of the temperature sensor, the fuel leak module, the ventilation module and the thermocouple array into the embedded near-field vapor concentration field prediction model, and adjust the temperature controller or the ventilation module in response to the near-field vapor concentration output by the prediction model, so that the near-field vapor concentration approaches the ignition critical threshold.

2. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 1, characterized in that, The tubular base is made of 310S stainless steel, and the ratio of axial length to cross-sectional radius is in the range of 4:1 to 6:

1. The heating process of the tubular base is less than or equal to 10 minutes.

3. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 2, characterized in that, The heating unit includes silicon carbide rods, and the temperature controller is configured to independently control the heating power of each silicon carbide rod to compensate for heat loss caused by airflow convection heat transfer in the ventilation module.

4. The aircraft engine core compartment piping hot surface fire simulation device according to claim 1, characterized in that, The core module simulator includes an inner shell and an outer shell arranged coaxially. The inner shell includes a small-diameter section and a gradually expanding section formed sequentially in the axial direction, and the outer shell includes a large-diameter section and a gradually narrowing section formed sequentially in the axial direction. The inner shell and the outer shell define the confined space.

5. The aircraft engine core compartment piping hot surface fire simulation device according to claim 4, characterized in that, Multiple thin-film heating units 121 are provided on the inner wall surface of the outer shell, and are configured to form a controllable wall surface temperature field not exceeding 400°C within the confined space.

6. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 4, characterized in that, The eccentricity adjustment module includes: The first support frame is disposed on the outer wall surface of the inner shell; The first motor is mounted on the first support frame; The first lead screw is adapted to rotate under the drive of the first motor; A support slider is slidably mounted on the first support frame and threadedly connected to the first lead screw. The support slider is also configured to be rotatably connected to one end of the tubular base. A support protrusion is disposed on the outer wall surface of the inner shell and is configured to be rotatably connected to the other end of the tubular base so that the tubular base rotates around the support protrusion under the drive of the support slider.

7. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 4, characterized in that, The ventilation module includes: Centrifugal fans are used to generate air volumes of 600-1200 m³ / h. 3 / h, airflow with a pressure of 1500-4000 Pa; Multiple ventilation ducts are provided, and an annular plate arranged in a vertical direction is connected between the inner shell and the outer shell. Multiple air inlets are formed on the annular plate. One end of the ventilation duct is connected to the air inlet, and the other end is connected to the centrifugal fan. The side of the tubular base facing the air inlet serves as the windward side. Preferably, a honeycomb grille is provided at one end of the ventilation duct connected to the air inlet, which is suitable for adjusting the turbulence intensity of the airflow entering the confined space.

8. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 4, characterized in that, The thermocouple array includes three strings of thermocouple trees, respectively arranged above the center of the tubular base, at an axial distance of 10cm above the center, and at a radial distance of 10cm above the center. Each string of thermocouple trees is set on the inner wall of the outer shell and includes five K-type thermocouples evenly arranged at 2cm intervals in the vertical direction. Two thermal radiometers are provided and suspended at 10cm intervals in the horizontal direction on the inner wall of the outer shell, and the line connecting the two thermal radiometers passes through the center of the tubular base.

9. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 1, characterized in that, The injection device includes: Second support frame; The second motor is mounted on the second support frame; The second lead screw is adapted to rotate under the drive of the second motor; The push block is slidably mounted on the second support frame and threadedly connected to the second lead screw; The fuel injection syringe is suitable for dispensing fuel into the fuel injection line under the push of the pusher block.

10. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 1, characterized in that, The near-domain vapor concentration field prediction model is a reduced-order response surface model constructed based on computational fluid dynamics transient numerical simulation and intrinsic orthogonal decomposition technology. The cooperative control system is configured to take the temperature spatial distribution data obtained by the thermocouple array, the thermal radiation data obtained by the thermal radiation meter, the tubular base temperature obtained by the temperature sensor, the airflow velocity of the ventilation module, and the fuel leakage flow rate of the injection device as input parameters, output the three-dimensional distribution of fuel vapor concentration in the confined space within a second-level time scale, and automatically adjust the output power of the temperature controller or the airflow velocity of the ventilation module in a closed loop when the concentration approaches the ignition critical threshold.

11. The fire simulation device for hot surface of pipelines in the core compartment of an aircraft engine according to claim 1, characterized in that, The core module simulator is equipped with a viewing window made of high borosilicate fire-resistant glass, which is used to observe and record the oil film sliding path and ignition of the tubular base.

12. An experimental method, characterized in that, Based on the aircraft engine core compartment piping hot surface fire simulation device as described in any one of claims 1-11, the experimental method includes: The experimental scenario parameters were set according to the airworthiness certification requirements for fire prevention of oil leakage from high-temperature hot surfaces in the core compartment of the aircraft engine, and the temperature sensor, injection device and ventilation module were calibrated for accuracy. The eccentricity adjustment module is activated and the engine vibration spectrum signal is input to drive the tubular base 21 to oscillate periodically within the confined space; The ventilation module is activated to introduce airflow into the confined space, and the heating unit is activated simultaneously to heat the tubular base; the temperature controller adjusts the heating power according to the temperature feedback difference between the windward and leeward sides to establish the preset temperature field on the outer surface of the tubular base; When the injection device is activated, fuel spreads and evaporates along the injection pipeline, which is attached to the outer surface of the tubular base by the arc-shaped skirt structure. Temperature spatial distribution data and thermal radiation data above the tubular base are acquired synchronously using a thermocouple array and a thermal radiation meter. The collaborative control system inputs the temperature spatial distribution data, thermal radiation data, base surface temperature, airflow parameters, and leakage flow rate into the near-field vapor concentration field prediction model to reconstruct the three-dimensional vapor concentration distribution field within the confined space. When the local concentration in the reconstructed three-dimensional vapor concentration distribution field approaches the ignition critical threshold, the collaborative control system automatically adjusts the output power of the temperature controller or the airflow parameters of the ventilation module to make the experimental conditions dynamically oscillate within the critical range between ignition and non-ignition, and records the temperature, ventilation volume and leakage rate data under the corresponding conditions.

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