Electric heating device with oil-proof and flow-guiding functions for inner channel of engine air inlet channel

Abstract

The invention discloses an electric heating device for an inner channel of an engine air inlet channel with oil-proof and flow-guiding functions, which comprises a heating component adhered to a groove of the inner channel of the engine air inlet channel 1 through a substrate adhesive layer 2, and the heating component consists of an insulating functional layer 3 and a heating element 4. The oil-proof flow guide filling structure is composed of a filling foam layer 5, an oil-proof flow guide covering layer 6 and an oleophobic coating 7. A flow guide groove 8 is formed in the oil-proof filling layer. The anti-icing device has the oil-proof and flow-guiding functions while preventing icing of the inner channel of the engine air inlet channel, ensures the flight safety of an airplane, and has more excellent service life and performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft engine anti-icing, and particularly relates to an electric heating device for an engine inlet duct inner channel with oil-proof and flow-guiding functions. BACKGROUND

[0002] Aircraft engine inlet duct anti-icing is one of the core technologies to ensure flight safety. In a low-temperature and high-humidity environment, icing of the inlet duct can cause serious consequences such as engine inlet efficiency decline, airflow distortion, and even surge and flameout.

[0003] At present, the electric heating anti-icing technology gradually becomes the mainstream scheme for replacing the traditional hot air anti-icing technology due to the advantages of fast response speed, flexible layout, and controllable energy consumption. The technology integrates electric heating elements (such as metal films, conductive polymers, or graphene-based materials) in the inner wall of the inlet duct or the composite material interlayer, and directly converts electric energy into heat energy to prevent icing.

[0004] However, the environment of the inlet duct inner channel close to the engine core area is extremely complex, and the polymer material on the surface of the electric heating device faces multiple severe challenges: Chemical corrosion of high-temperature oil vapor: The lubricating oil vapor and unburned hydrocarbons generated during engine operation condense on the inner wall of the inlet duct, forming a viscous oil film on the surface of the electric heating layer. The esters, acidic additives, and pyrolysis products contained in these oily substances can gradually penetrate into the polymer matrix (such as epoxy resin, silicone rubber, or polyurethane), causing swelling, plasticization, or molecular chain rupture. For example, the crosslinking density of a modified epoxy resin hydrophobic coating can decrease by more than 30% after long-term oil immersion, resulting in the failure of superhydrophobic function; and the volume expansion rate of a nitrile rubber insulation function layer in a 150℃ high-temperature oil vapor environment exceeds 15%, accelerating the decay of insulation performance and possibly causing circuit short circuit.

[0005] Oil-heat synergistic aging effect: The electric heating element generates local high temperature (usually >100℃) when working, which together with the oil film induces thermal oxidative decomposition of the polymer material. The lubricating oil undergoes coking reaction at high temperature to generate carbonized deposits that block the flow-guiding structure and accelerate material embrittlement. Experiments show that the tensile strength retention rate of filled conductive silicone rubber is less than 60% after continuous work in an oil-heat coupling environment for 500 hours, and the resistivity fluctuation amplitude reaches ±25% of the initial value, seriously affecting the heating uniformity.

[0006] Therefore, it is urgent to develop an engine intake passage inner channel electric heating device integrated with oil-proof and flow-guiding functions, to solve the core problems of heat transfer efficiency attenuation, insulation failure and fire hazards caused by oil accumulation, and to provide a reliable electric heating anti-icing solution for the near-engine area through the synergistic innovation of oil corrosion resistant composite material system, flow-guiding and heating integrated structure and self-adaptive thermal management technology. SUMMARY

[0007] The purpose of the present application is to solve the problems of oil accumulation, heat efficiency decline and material aging of existing engine intake passage electric heating devices in high temperature oil vapor environment, to provide an electric heating device with oil-proof and flow-guiding functions through innovative multi-layer composite structure and optimized manufacturing process, and to significantly improve the reliability and service life of the near-engine area anti-icing system. The device effectively prevents the influence of lubricating oil accumulation on heating performance through a specially designed flow-guiding structure and oil-resistant material system, while ensuring stable operation under severe working conditions.

[0008] The present application provides an electric heating device for an engine intake passage inner channel with oil-proof and flow-guiding functions, comprising: a base adhesive layer 2; a heating assembly adhered to the recess of the engine intake passage 1 inner channel through the base adhesive layer 2; an oil-proof and flow-guiding filling structure composed of a filling foam layer 5, an oil-proof and flow-guiding cover layer 6 and an oil-repellent coating layer 7, the filling foam layer 5 being able to fill the recess, the oil-proof and flow-guiding cover layer 6 being adhered to the filling foam layer 5, and the oil-repellent coating layer 7 being coated on the oil-proof and flow-guiding cover layer 6, the oil-proof and flow-guiding cover layer 6 being designed in the shape of a flow-guiding groove.

[0009] Preferably, the heating assembly comprises: an insulation functional layer 3 adhered to the recess of the engine intake passage 1 inner channel through the base adhesive layer 2; a heating element 4 wrapped by the insulation functional layer 3.

[0010] Preferably, the base adhesive layer 2 is composed of a medium temperature curing epoxy adhesive film; the insulation functional layer 3 is composed of polyimide; and the heating element 4 is composed of graphene heating film.

[0011] Preferably, the filling foam layer 5 is composed of flame-retardant polyurethane foam.

[0012] Preferably, the flame-retardant polyurethane foam is generated by the reaction of modified polyether polyol and polymethylene polyphenyl isocyanate.

[0013] Preferably, the oil-proof and flow-guiding cover layer 6 is composed of fluorosilicone rubber; and the oil-repellent coating layer 7 is composed of perfluoropolyether.

[0014] Preferably, the flow guide groove is a V-shaped flow guide groove, the depth of the V-shaped flow guide groove is 5-10 mm, the top width of the V-shaped flow guide groove is 8 mm-15 mm, and the inclination angle of the V-shaped flow guide groove is 10-20°.

[0015] Preferably, the preparation process of the oil-proof flow guide filling structure is as follows: Mold inner application: the pre-cut fluorosilicone rubber raw rubber is laid on the cavity, and the whole area is ensured to be attached through a vacuum adsorption system, and the gap is ≤0.1 mm; Coating process: the surface of the rubber is grid coated with vinyl tri-tert-butyl peroxysilane, the coating amount is 75±3 g / m², and the rubber is left to stand for 180±15 s in an environment at 25 ℃, so as to promote the hydrolysis of the silane to form active groups; Closed mold: modified polyether polyol and polymethylene polyphenyl isocyanate are injected at high pressure through the injection hole, the modified polyether polyol and the polymethylene polyphenyl isocyanate are premixed at a mass ratio of 100:85; the injection pressure is 15.0±0.5 MPa, the material temperature is 45±0.5 ℃, the pressure holding foaming time is 20±1 min, a foam structure with a closed cell rate of >97% and a density of 215±3 kg / m³ is formed, and the foam structure is left to stand for 30 minutes; Vulcanization tank vulcanization: pre-curing temperature 70±1 ℃, time 30 min, pressure 0.8 MPa; main vulcanization temperature 130±0.5 ℃, time 90 min, pressure 1.0 MPa, and the mold is demolded after cooling to room temperature at a rate of ≤5 ℃ / min; Gas deposition of perfluoropolyether solution, solid content 12%, film thickness 6±1 μm, 130 ℃ curing for 30 min; Trimming: the excess fluorosilicone rubber is cut off.

[0016] The advantages of the present application are: The present application provides an electric heating device with oil-proof and flow guide functions while ensuring ice-proof performance, which significantly improves the reliability and service life of the ice-proof system in the near-engine area. The device effectively prevents the influence of accumulated lubricating oil on heating performance through a specially designed flow guide structure and an oil-resistant material system, prevents chemical corrosion of foam high-temperature oil vapor, and prevents oil-heat synergistic aging effects, ensuring stable operation under severe working conditions.

[0017] The present application has three oil-proof functions of flow guide groove, oil-repellent coating, and oil-resistant material body. The flow guide groove prevents oil accumulation and corrosion on the surface of the electric heating device, the polyurethane foam has good thermal insulation property, which can reduce the temperature of the oil droplet contact surface, prevent chemical corrosion of high-temperature oil vapor, and prevent oil-heat synergistic aging effects, so as to ensure the stable and reliable operation of the electric heating device in the environment of the engine inlet.

[0018] The polyurethane foam, polyimide film and other light structures are adopted in the application, the weight of the structure is reduced to the maximum, and the light weight of the structure is maintained while the channel structure recess in the air inlet is filled. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A cross-sectional view of the engine electric heating device according to the application; Figure 2 A schematic view of the flow direction of the liquid drops on the cross section of the flow guide groove; Figure 3 A schematic view of the flow direction of the liquid drops on the cross section of the flow guide groove; DETAILED DESCRIPTION

[0020] The application will be further described below with reference to the accompanying drawings Figure 1 - the accompanying drawings Figure 3 and examples, but not as a basis for limiting the application.

[0021] The technical solution of the application is: Overall structure and function The device adopts a 6-layer composite structure, and each layer cooperates with each other to form a complete protection system: The base bonding layer serves as an interface connecting layer between the device and the inner wall of the air inlet, realizes reliable combination of the structure body and the metal base, and ensures effective transmission of mechanical load.

[0022] The heating assembly comprises two functional units: The insulating functional layer integrates the functions of electrical insulation and heat management, supports the heating layer and blocks current leakage.

[0023] The heating layer serves as a core functional unit, undertakes the task of converting electrical energy into heat energy, and provides a proactive anti-icing heat source; The oil-proof flow guide filling structure is composed of a filling foam layer, an oil-proof flow guide cover layer, and an oil-repellent coating, and provides a triple protection mechanism: The filling foam layer is composed of flame-retardant polyurethane foam, fills the gap area, absorbs high-frequency vibration energy of the engine, relieves the impact of mechanical stress on the functional layer, and simultaneously isolates heat to prevent heat from spreading to non-anti-icing areas; The oil-proof flow guide cover layer is composed of fluorosilicone rubber, guides the directional flow of oil through the physical structure of the flow guide groove, and prevents local accumulation of oil stains; The oil-repellent coating reduces the surface adhesion of oil stains through chemical modification, and cooperatively improves the oil discharge efficiency.

[0024] The base adhesive layer in the aforementioned electric heating device is a medium-temperature curing epoxy resin structural adhesive film, which has a curing temperature of 120℃, a lap shear strength ≥18.5MPa, and a 90° peeling strength ≥6.3kN / m, and has good adhesive strength, and its low curing temperature can prevent adverse effects on the engine inlet passage.

[0025] In the aforementioned electric heating device, the flame-retardant polyurethane foam filling layer is generated by the reaction of modified polyether polyol (hydroxyl value 380±10mgKOH / g) and polymethylene polyphenyl isocyanate (PMDI, NCO% 31.5±0.5). The closed cell rate is more than 97%, the average cell diameter is 150±20μm, the cell wall thickness is 2.0±0.3μm, the density is 200±10kg / m³, and the thermal conductivity is not more than 0.022W / m·K. Its internal porous structure can effectively insulate heat, making heat conduct in the heating direction, and at the same time, it can play a buffering and damping role, preventing the base adhesive layer from fatigue failure under high-frequency vibration of the aircraft engine. Its low-density characteristics can also greatly reduce the overall weight of the electric heating device.

[0026] In the aforementioned electric heating device, the hardness of the fluorosilicone rubber of the oil-proof flow guide covering layer is Sha A 35-40, the thickness is 1±0.1mm, the tensile strength is >12MPa, 10MPa, the elongation at break is ≥250%, and the continuous temperature resistance is -50℃~180℃. The volume change rate under the action of aviation lubricating oil at 150℃×72h is less than ≤3%. It has good structural strength and fuel resistance, and can work stably in a heavy oil environment.

[0027] The flow guide groove in the aforementioned electric heating device is a V-shaped groove with a depth of 5-10mm, a top width of 8mm-15mm, and an inclination angle of 10-20°. This angle not only guides the oil droplets to flow upwards, but also facilitates demolding during the manufacturing process.

[0028] The oil-repellent coating in the aforementioned electric heating device has a surface energy characteristic of a static contact angle >128° and a rolling angle <8°. This improves the efficiency of oil droplets flowing in the flow guide groove and prevents oil droplets from remaining in the flow guide groove.

[0029] The preparation process of the aforementioned oil-proof flow guide filling structure is as follows: Mold lining The pre-cut fluorosilicone rubber raw rubber (Sha A 35-40, thickness 1±0.1mm) is laid on the cavity, and the vacuum suction system (-98±1kPa, 5min) is used to ensure full-area adhesion with a gap ≤0.1mm.

[0030] Coating process: The surface of the rubber is grid-coated with vinyl tri-tert-butyl peroxysilane at a coating amount of 75±3g / m², and is left to stand for 180±15s in a 25℃ environment to promote the hydrolysis of the silane to form active groups.

[0031] The mold is closed, and flame-retardant polyurethane mixture is injected under high pressure through the injection port. Modified polyether polyol and polymethylene polyphenyl isocyanate are premixed at a mass ratio of 100:85. The injection pressure is 15.0±0.5MPa, and the material temperature is 45±0.5℃. The mixture is held under pressure for 20±1 min to form a foam structure with a closed-cell rate >97% and a density of 215±3 kg / m³. (30 min) Vulcanization in a vulcanizing tank: pre-curing temperature 70±1℃, time 30min, pressure 0.8MPa; main vulcanization temperature 130±0.5℃, time 90min, pressure 1.0MPa; demolding after cooling to room temperature at a rate ≤5℃ / min.

[0032] Vapor deposition of perfluoropolyether solution (solid content 12%), film thickness 6±1μm, cured at 130℃ for 30min.

[0033] Trim the edges and remove excess fluorosilicone rubber.

[0034] Example 1. As... Figure 1 As shown: The electric heating device includes a substrate bonding layer 2 (contacting the inner wall of the air intake duct 1), an insulating functional layer 3, a heating element layer 4, a filling foam layer 5, an oil-proof and flow-guiding covering layer 6, and an oleophobic coating 7.

[0035] The substrate adhesive layer 2 is a medium-temperature curing epoxy film with a thickness of 0.15 mm, ensuring sufficient peel strength after bonding; The insulating functional layer 3 is a polyimide composite film with a thickness of 0.42mm, which can withstand a dielectric withstand voltage test of 1500VAC and wraps around the heating element.

[0036] Heating element 4 is a graphene heating film with a thickness of 0.50 mm and a power density of 2 W / cm². 2 Its power density can meet the anti-icing requirements of the air intake passage of aircraft engines.

[0037] The filling foam layer 5 is flame-retardant polyurethane foam, which fills the recessed area of ​​the air intake channel structure to reduce weight and provide cushioning.

[0038] The oil-proof and flow-guiding cover layer 6 is made of fluorosilicone rubber with a thickness of 1mm, which prevents oil stains from entering while ensuring structural strength.

[0039] The surface of the oil-resistant and flow-guiding coating has flow-guiding grooves, the cross-sectional characteristics of which vary along the direction of the grooves, with a depth of 5-10mm, a top width of 8mm-15mm, and an inclination angle of 13°. The oleophobic coating 7 is a perfluoropolyether with a thickness of 6±1μm, which allows oil droplets to flow more smoothly on the oil-repellent and flow-guiding coating.

[0040] The electric heating device is powered by 270VDC and connected to the power supply on the aircraft through wires.

[0041] When the aircraft is in icing environment, the electric heating device is powered on As shown in Figure 2 When the engine lubricating oil drops onto the surface of the electric heating device, in the cross-sectional direction of the flow guide groove, as shown in Figure 2 , the oil droplets will first flow into the low point of the cross-section of the flow guide groove in the direction indicated by the arrow. Then, as shown in Figure 3 , the oil droplets will flow from high to low along the flow guide groove. Due to the installation angle, the height of the bottom of the left flow guide groove is lower than that of the right flow guide groove, so the oil droplets will move from right to left in the flow guide groove as indicated by the arrow, and finally flow out of the electric heating device, avoiding accumulation on its surface.

[0042] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements that can be easily thought of by those skilled in the art within the scope disclosed by the present application should be covered within the protection scope of the present application.

Claims

1. An electric heating device for an engine intake manifold with oil-preventing and deflecting function, characterized in that, The electric heating device includes: Matrix adhesive layer (2); The heating assembly is bonded to the groove of the inner channel of the engine intake manifold (1) through the substrate adhesive layer (2); The oil-proof and flow-guiding filling structure consists of a filling foam layer (5), an oil-proof and flow-guiding covering layer (6), and an oleophobic coating (7). The filling foam layer (5) can fill the groove. The oil-proof and flow-guiding covering layer (6) is bonded to the filling foam layer (5). The oleophobic coating (7) is applied to the oil-proof and flow-guiding covering layer (6). The oil-proof and flow-guiding covering layer (6) is designed in the shape of a flow-guiding groove.

2. The electric heating device according to claim 1, characterized in that, The heating component includes: The insulating functional layer (3) is bonded to the groove of the inner channel of the engine intake manifold (1) through the substrate adhesive layer (2); The heating element (4) is wrapped by the insulating functional layer (3).

3. The electric heating device according to claim 2, characterized in that, The substrate adhesive layer (2) is composed of a medium-temperature curing epoxy film; the insulating functional layer (3) is composed of polyimide; and the heating element (4) is composed of a graphene heating film.

4. The electric heating device according to claim 1, characterized in that, The filling foam layer (5) is composed of flame-retardant polyurethane foam.

5. The electric heating device according to claim 4, characterized in that, The flame-retardant polyurethane foam is generated by reacting modified polyether polyol with polymethylene polyphenyl isocyanate.

6. The electric heating device according to claim 5, characterized in that, The oil-repellent and flow-guiding cover layer (6) is made of fluorosilicone rubber; the oleophobic coating layer (7) is made of perfluoropolyether.

7. The electric heating device according to claim 1, characterized in that, The guide channel is a V-shaped guide channel with a depth of 5-10mm, a top width of 8mm-15mm, and an inclination angle of 10-20°.

8. The electric heating device according to claim 6, characterized in that, The fabrication process of the oil-resistant and flow-guiding filling structure is as follows: In-mold application: Pre-cut fluorosilicone rubber raw material is laid in the mold cavity, and a vacuum adsorption system is used to ensure full-area adhesion with a gap of ≤0.1mm; Coating process: Vinyl tritert-butyl peroxysilane is applied to the rubber surface in a grid pattern with a coating amount of 75±3 g / m². The surface is left to stand at 25°C for 180±15 s to promote the hydrolysis of silane and the formation of active groups. Closed mold: Modified polyether polyol and polymethylene polyphenyl isocyanate are injected under high pressure through the injection hole. The modified polyether polyol and polymethylene polyphenyl isocyanate are premixed at a mass ratio of 100:

85. The injection pressure is 15.0±0.5MPa, the material temperature is 45±0.5℃, and the foaming is carried out under pressure for 20±1min to form a foam structure with a closed cell rate of >97% and a density of 215±3kg / m³. The foam is then allowed to stand for 30 minutes. Vulcanization in a vulcanizing tank: Pre-curing temperature 70±1℃, time 30min, pressure 0.8MPa; main vulcanization temperature 130±0.5℃, time 90min, pressure 1.0MPa, and demolding after cooling to room temperature at a rate of ≤5℃ / min; Vapor-deposited perfluoropolyether solution, solid content 12%, film thickness 6±1μm, cured at 130℃ for 30min; Trimming: Remove excess fluorosilicone rubber.

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