Design method of double flap check valve for aircraft

Abstract

The application discloses a design method of a double-flap check valve for an airplane. Through a series, flow, and theoretical data design method, based on the working condition of the double-flap check valve and the index to be achieved, the double-flap check valve is subjected to series modification and optimization of structure, dynamic balance, material strength, and flow channel structure, so that the weight, structure, and strength of the double-flap check valve can be optimized, and the strength, sealing performance, and response speed of the double-flap check valve are ensured on the premise of simplifying the structure of the double-flap check valve and reducing the weight of the double-flap check valve.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of double-poppet check valves for aircraft, and particularly relates to a design method of a double-poppet check valve for aircraft. BACKGROUND

[0002] In the nacelle system of an aero-engine, the check valve is a core component for airflow control, and its reliability and response performance directly determine the safety and reliability of the engine under complex working conditions. The main failure modes of the existing check valve are sealing failure, structural fatigue failure, and response sticking. Especially in a high-temperature, high-pressure, and high-frequency vibration environment, the existing check valve design mainly has the following three problems:

[0003] 1. Insufficient high-temperature sealing, the sealing surface deforms by ≥0.1mm under the reverse pressure at 600℃, thereby causing the leakage rate at the sealing surface to exceed the standard;

[0004] 2. Insufficient fatigue life of the valve body component, especially the valve disc and the hinge shaft as movable components, the wear rate is usually ≥0.01mm / 1000h, which is difficult to meet the requirement of MTBF≥50000h;

[0005] 3. Lightweight and strength are contradictory, the traditional valve disc is made of Incenel718 material, and the density is 8.2g / cm 3 , which causes the weight of the traditional valve disc to be ≥0.5kg, resulting in the overall weight of the valve body exceeding the standard; after reducing the weight of the valve body, the strength requirement is not met.

[0006] Therefore, in view of the above-mentioned deficiencies in the existing check valve design, the application discloses a design method of a double-poppet check valve for aircraft. SUMMARY

[0007] The application discloses a design method of a double-poppet check valve for aircraft, which can optimize the weight, structure, and strength of the double-poppet check valve, and ensure the strength, sealing performance, and response speed of the double-poppet check valve under the premise of simplifying the structure and reducing the weight of the double-poppet check valve.

[0008] The application is implemented by the following technical scheme:

[0009] A design method of a double-poppet check valve for aircraft, comprising the following steps:

[0010] Step 1, based on the installation position of the double-poppet check valve, performing dynamic analysis on the double-poppet check valve to obtain working condition parameters, and establishing a performance index quantization model of the valve body based on the working condition parameters;

[0011] Step 2, unequal heavy dynamic balance design, stop design, material compatibility and corrosion prevention design are carried out on the double valve clappers of the valve body according to the performance index quantification model;

[0012] Step 3, based on the design results of step 2, the valve body and valve clapper are modeled and fluid mechanics design simulation is carried out, and the flow channel and structural strength of the valve body are optimized based on the fluid mechanics simulation results;

[0013] Step 4, based on the optimization results in step 3, the valve body and valve clapper are processed and manufactured, and the valve body and valve clapper are assembled;

[0014] Step 5, performance test and reliability verification are carried out on the assembled valve body and valve clapper;

[0015] Step 6, iteration optimization is carried out on the valve body and valve clapper, and steps 2-5 are repeated until the valve body and valve clapper meet the design requirements.

[0016] The design requirements refer to the weight requirement of the valve body composed of the valve body, i.e. the weight of the entire valve body is less than or equal to 500g; the sealing requirement, i.e. the fluid leakage rate when the valve clapper is closed is less than or equal to 5x10 -9 mbar·L / s, the opening and closing response speed requirement, i.e. the opening and closing action response time of the valve clapper is less than or equal to 0.1s; the strength requirement, i.e. the fatigue safety factor of the valve body under the vibration environment system of 10-2000Hz is greater than or equal to 1.5, and the fatigue service life is greater than or equal to 50000 hours.

[0017] In order to better realize the present application, further, the performance index quantification model established in step 1 includes a leakage rate control model and a weight optimization model, and the leakage rate control model is specifically:

[0018] ;

[0019] Wherein: Q represents the leakage rate after the valve clapper is closed; represents the sealing gap; represents the pressure difference on both sides of the valve clapper; represents the viscosity of the gas fluid; L represents the sealing length between the valve body and the valve clapper;

[0020] The weight optimization model is specifically:

[0021] ;

[0022] Wherein: represents the material density of the valve body; V represents the volume of the valve body; represents the weight of the moving parts, i.e. the weight of the valve clapper and the hinge shaft; represents the optimal weight under the premise of meeting the leakage rate requirement.

[0023] In order to better realize the present application, further, the performance index quantification model established in step 1 includes a leakage rate control model and a weight optimization model, and the constraint condition of the performance index quantification model is:

[0024] ;

[0025] Wherein: represents the maximum working stress borne by the valve body; represents the material allowable stress; f represents the modal frequency of the valve body; represents the working frequency of the engine in which the valve body is located.

[0026] In order to better realize the present application, further, step 2 specifically includes:

[0027] Step 2.1, a double-valve clack torque dynamic balance model is established, and the opening angle and motion trajectory of the valve clack are optimized through the double-valve clack torque dynamic balance model;

[0028] Step 2.2, an adjustable stop device is designed, and the opening angle of the valve clack is adjusted to 75±2° through the adjustable stop device;

[0029] Step 2.3, galvanic corrosion control is performed on the two valve clacks, so that the potential difference between the two valve clacks is less than or equal to 0.1V; corrosion-resistant treatment is performed on the surface of the valve body; nitriding treatment is performed on the hinge shaft between the valve clack and the valve body;

[0030] Step 2.4, a stress distribution model of the contact sealing surface between the valve body and the valve clack is established, and a conical sealing surface is established between the valve body and the valve clack;

[0031] Step 2.5, a damping bushing is arranged between the valve clack and the hinge shaft, so that the viscous damping force when the valve clack is closed is less than or equal to 5N; the sealing surface between the valve body and the valve clack is calculated by specific pressure, so as to optimize the area of the sealing surface between the valve body and the valve clack.

[0032] In order to better realize the present application, further, the double-valve clack torque dynamic balance model in step 2.1 is specifically:

[0033] M= ;

[0034] Wherein: represents the weight of the first valve clack; represents the weight of the second valve clack; represents the moment length of the first valve clack relative to the center of mass; represents the moment length of the second valve clack relative to the center of mass; T represents the torque received by the valve clack; represents the opening angle of the valve clack; M represents the torque of the valve clack.

[0035] To better realize the present application, further, the step 3 specifically includes:

[0036] Step 3.1, the assembly model of the valve body and the valve disc is established, tetrahedral mesh is divided, the inlet pressure boundary and the outlet mass flow boundary of the assembly model are determined, the turbulent flow model of the flow channel is established to analyze the maximum flow velocity position, the pressure drop position and the pressure recovery position of the assembly model;

[0037] Step 3.2, the NACA0012 airfoil curve is used to optimize the diffusion angle of the flow channel inlet and the flow channel outlet, and the flow guide boss is arranged on the flow surface of the valve disc to reduce the impact of the airflow on the sealing surface between the valve body and the valve disc;

[0038] Step 3.3, the strength representation of the valve disc, the valve body and the hinge shaft under different flow channel optimization results is analyzed by using solid solution treatment simulation, aging treatment simulation and nitriding treatment simulation;

[0039] Step 3.4, based on the working condition parameters, the temperature field simulation is carried out on the valve body, the valve disc, the hinge shaft and the sealing surface, the thermal expansion amount of the valve body, the valve disc and the hinge shaft is calculated, and the gap between the valve body, the valve disc, the hinge shaft and the sealing surface is compensated based on the thermal expansion amount.

[0040] To better realize the present application, further, the step 4 specifically includes:

[0041] Step 4.1, the valve body is manufactured by using isothermal forging process, and the inner wall of the valve body is treated by pulse electroplating hard chromium, the thickness of the electroplated hard chromium layer is 0.03-0.05mm, the porosity is less than or equal to 5%, and the roughness of the inner wall of the valve body is less than or equal to 1.6μm;

[0042] Step 4.2, the valve disc is cast by using the lost wax method, the surface roughness of the valve disc is less than or equal to 3.2μm, and the sealing surface of the valve disc is processed in the order of rough grinding, fine grinding and grinding, so that the flatness of the sealing surface is less than or equal to 0.001mm;

[0043] Step 4.3, the valve body and the valve disc are cleaned by using the ultrasonic cleaning process, and the valve body, the valve disc and the hinge shaft are assembled, the assembly gap between the valve disc and the hinge shaft is 0.01-0.03mm;

[0044] Step 4.4, the surface of the valve body is pretreated by sand blasting, the sand blasting particle size is 80-120mesh; then the PTFE coating is applied on the surface of the valve body by using the electrostatic spraying process, the thickness of the PTFE coating is 50±5μm; the titanium sacrificial anode is embedded in the flange surface of the valve body, so that the potential difference between the titanium sacrificial anode and the valve body is less than or equal to 0.05V.

[0045] To better realize the present application, further, the step 5 specifically includes:

[0046] Step 5.1, the assembled double-poppet check valve is subjected to positive pressure test and reverse leakage test;

[0047] Step 5.2, the double-poppet check valve is subjected to fatigue test;

[0048] Step 5.3, the double-poppet check valve is subjected to accelerated life test and MTBF evaluation.

[0049] In order to better realize the present application, further, the step 6 specifically comprises:

[0050] Step 6.1, a mathematical model related to pressure drop and curvature radius of flow channel is established based on response surface method, and a constraint condition of curvature radius is set;

[0051] Step 6.2, the optimal curvature radius of flow channel is solved by genetic algorithm;

[0052] Step 6.3, the wall thickness of valve body is subjected to lightweight iteration, and the optimal wall thickness of valve body is searched under the premise of meeting the safety factor requirement and modal frequency avoidance requirement.

[0053] The safety factor requirement refers to that the fatigue safety factor of the entire double-poppet check valve body is greater than or equal to 1.5, and the modal frequency avoidance requirement refers to that the natural vibration frequency of the double-poppet check valve itself cannot be the same as the engine vibration frequency of the working environment.

[0054] In order to better realize the present application, further, the mathematical model established in the step 6.1 is specifically:

[0055] ;

[0056] Wherein: represents pressure drop; R represents curvature radius of flow channel;

[0057] The constraint condition of curvature radius is: R≥5mm.

[0058] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0059] (1) The present application establishes a torque balance equation of double-poppet opening through unequal weight design and centroid offset design of double valve, realizes rapid response of valve within 0.1s and low torque opening under the premise of reducing valve weight, effectively reduces impact load received by valve, and makes the wear rate of sealing surface between valve and valve body reduce by more than 35%, and the leakage rate is improved by 20% compared with the industry average standard;

[0060] (2) The application carries out series transformation and optimization of the structure, dynamic balance, material strength and flow channel structure of the double-disc check valve based on the working condition of the double-disc check valve and the index to be achieved, thereby guaranteeing the strength, sealing performance and response speed of the double-disc check valve under the premise of simplifying the structure of the double-disc check valve and reducing the weight of the double-disc check valve. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The flow step schematic diagram of the application. DETAILED DESCRIPTION

[0062] Example 1:

[0063] The design method of the double-disc check valve for an airplane of the embodiment, as shown in the figure, comprises the following steps: Figure 1

[0064] Step 1, based on the installation position of the double-disc check valve, dynamic analysis is carried out on the double-disc check valve to obtain working condition parameters, and a performance index quantization model of the valve body is established based on the working condition parameters;

[0065] Step 2, according to the performance index quantization model, unequal weight dynamic balance design, stop design, material compatibility and corrosion prevention design are carried out on the double valve disc of the valve body;

[0066] Step 3, based on the design result of step 2, modeling is carried out on the valve body and valve disc and fluid mechanics design simulation is carried out, and based on the fluid mechanics simulation result, the flow channel and structural strength of the valve body are optimized;

[0067] Step 4, based on the optimization result in step 3, the valve body and valve disc are processed and manufactured, and the valve body and valve disc are assembled;

[0068] Step 5, performance test and reliability verification are carried out on the assembled valve body and valve disc;

[0069] Step 6, iterative optimization is carried out on the valve body and valve disc, and steps 2-5 are repeated until the valve body and valve disc meet the design requirements.

[0070] In order to better realize the application, further, the performance index quantization model established in step 1 comprises a leakage rate control model and a weight optimization model, and the leakage rate control model specifically comprises:

[0071] ;

[0072] Wherein, Q represents the leakage rate after the valve disc is closed; represents the sealing gap; represents the pressure difference on both sides of the valve disc; represents the viscosity of the gas fluid; and L represents the sealing length between the valve body and the valve disc.​

[0073] The weight optimization model is specifically:

[0074]

[0075] Wherein: represents the material density of the valve body; V represents the volume of the valve body; represents the weight of the moving part, i.e. the weight of the valve disc and the hinge shaft; represents the optimal weight under the premise of meeting the leakage rate requirement.

[0076] In order to better realize the present application, further, the performance index quantification model established in step 1 includes a leakage rate control model and a weight optimization model, and the constraint condition of the performance index quantification model is:

[0077]

[0078] Wherein: represents the maximum working stress borne by the valve body; represents the material allowable stress; f represents the modal frequency of the valve body; represents the working frequency of the engine in which the valve body is located.

[0079] In order to better realize the present application, further, step 2 specifically includes:

[0080] Step 2.1, a double-valve disc torque dynamic balance model is established, and the opening angle and motion trajectory of the valve disc are optimized through the double-valve disc torque dynamic balance model;

[0081] Step 2.2, an adjustable stop device is designed, and the opening angle of the valve disc is adjusted to 75±2° through the adjustable stop device;

[0082] Step 2.3, galvanic corrosion control is performed on the two valve discs, so that the potential difference between the two valve discs is less than or equal to 0.1V; corrosion-resistant treatment is performed on the surface of the valve body; nitriding treatment is performed on the hinge shaft between the valve disc and the valve body;

[0083] Step 2.4, a stress distribution model of the contact sealing surface between the valve body and the valve disc is established, and a conical sealing surface is established between the valve body and the valve disc;

[0084] Step 2.5, a damping bushing is arranged between the valve disc and the hinge shaft, so as to ensure that the viscous damping force when the valve disc is closed is less than or equal to 5N; the sealing surface between the valve body and the valve disc is calculated by pressure ratio, so as to optimize the area of the sealing surface between the valve body and the valve disc.

[0085] In order to better realize the present application, further, the double-valve disc torque dynamic balance model in step 2.1 is specifically: ​​

[0086] M= ;

[0087] wherein: represents the weight of the first valve disc; represents the weight of the second valve disc; represents the moment length of the first valve disc relative to the center of mass; represents the moment length of the second valve disc relative to the center of mass; T represents the torque received by the valve disc; represents the opening angle of the valve disc; M represents the torque of the valve disc.

[0088] In order to better realize the present application, further, the step 3 specifically comprises:

[0089] Step 3.1, establish the assembly model of the valve body and the valve disc, perform tetrahedral meshing, determine the inlet pressure boundary and the outlet mass flow boundary of the assembly model, and establish the turbulent flow model of the flow channel to analyze the maximum flow velocity position, the pressure drop position and the pressure recovery position of the assembly model;

[0090] Step 3.2, optimize the diffusion angle of the flow channel inlet and the flow channel outlet by using the NACA0012 airfoil curve, and set a flow guide boss on the flow surface of the valve disc to reduce the impact of airflow on the sealing surface between the valve body and the valve disc;

[0091] Step 3.3, optimize and analyze the strength representation of the valve disc, the valve body and the hinge shaft under different flow channel optimization results by using solid solution treatment simulation, aging treatment simulation and nitriding treatment simulation;

[0092] Step 3.4, based on the working condition parameters, perform temperature field simulation on the valve body, the valve disc, the hinge shaft and the sealing surface, calculate the thermal expansion amount of the valve body, the valve disc and the hinge shaft, and compensate the gap between the valve body, the valve disc, the hinge shaft and the sealing surface based on the thermal expansion amount.

[0093] In order to better realize the present application, further, the step 4 specifically comprises:

[0094] Step 4.1, manufacture the valve body by using isothermal forging process, and perform pulse electroplating hard chromium treatment on the inner wall of the valve body, the thickness of the electroplated hard chromium layer is 0.03-0.05mm, the porosity is less than or equal to 5%, and the roughness of the inner wall of the valve body is less than or equal to 1.6μm;

[0095] Step 4.2, cast the valve disc by using the lost wax method, the surface roughness of the valve disc is less than or equal to 3.2μm; process the sealing surface of the valve disc in the order of rough grinding, fine grinding and grinding, so that the flatness of the sealing surface is less than or equal to 0.001mm;

[0096] Step 4.3, the valve body and the valve disc are cleaned by using an ultrasonic cleaning process, the valve body, the valve disc and the hinge shaft are assembled, and the assembly gap between the valve disc and the hinge shaft is 0.01-0.03 mm;

[0097] Step 4.4, the surface of the valve body is pretreated by sand blasting, the sand blasting particle size is 80-120 mesh; then the PTFE coating is applied on the surface of the valve body by using an electrostatic spraying process, the thickness of the PTFE coating is 50±5 μm; and the titanium sacrificial anode is embedded in the flange surface of the valve body, so that the potential difference between the titanium sacrificial anode and the valve body is less than or equal to 0.05 V.

[0098] In order to better realize the present application, further, the step 5 specifically comprises:

[0099] Step 5.1, the assembled double-disc one-way valve is subjected to forward pressure resistance test and reverse leakage test;

[0100] Step 5.2, the double-disc one-way valve is subjected to fatigue test;

[0101] Step 5.3, the double-disc one-way valve is subjected to accelerated life test and MTBF evaluation.

[0102] In order to better realize the present application, further, the step 6 specifically comprises:

[0103] Step 6.1, a mathematical model related to the pressure drop and the curvature radius of the flow channel is established based on the response surface method, and a constraint condition of the curvature radius is set;

[0104] Step 6.2, the optimal curvature radius of the flow channel is solved by using a genetic algorithm;

[0105] Step 6.3, the wall thickness of the valve body is iteratively lightened, and the optimal wall thickness of the valve body is searched under the premise of meeting the safety coefficient requirement and the modal frequency avoidance requirement.

[0106] In order to better realize the present application, further, the mathematical model established in the step 6.1 is specifically:

[0107] ;

[0108] Wherein: represents the pressure drop; R represents the curvature radius of the flow channel;

[0109] The constraint condition of the curvature radius is: R≥5 mm.

[0110] Example 2

[0111] The embodiment discloses a design method of a double-disc one-way valve for an airplane, which is improved on the basis of the embodiment 1, and specifically:

[0112] The existing double flap check valve for aircraft mainly has the following shortcomings:

[0113] 1. Insufficient high temperature sealing, the sealing surface deforms ≥0.1mm under the reverse pressure at 600℃ temperature environment, thereby causing the leakage rate at the sealing surface to exceed the standard;

[0114] 2. Insufficient fatigue life of the valve body component, especially the valve flap and hinge shaft as movable components, the wear rate is usually more than 0.01mm / 1000h, which is difficult to meet the requirement of MTBF≥50000h;

[0115] 3. Lightweight and strength are contradictory, the traditional valve flap is made of Incenel718 material, and its density is 8.2g / cm 3 , which causes the weight of the traditional valve flap to be ≥0.5kg, resulting in the overall weight of the valve body exceeding the standard; reducing the weight of the valve body does not meet the strength requirement.

[0116] Therefore, based on the above problems of the existing double flap check valve for aircraft, the embodiment proposes a design method of a double flap check valve for aircraft, first determines the performance indicators of the double flap check valve as shown in Table 1:

[0117] Table 1, performance index table

[0118]

[0119] The reliability indicators of the double flap check valve are determined as shown in Table 2:

[0120] Table 2, reliability index table

[0121]

[0122] Determine the airworthiness indicators of the double flap check valve

[0123] The double flap check valve fully meets the CAAC25 structural strength requirements and passes the following certifications:

[0124] (1) Fireproof design: material flame retardant registration V-0, no failure after 30min of flame exposure;

[0125] (2) Failure safety: double flap redundancy design, still maintains 50% sealing capacity when a single flap fails;

[0126] (3) Environmental adaptability: meets the requirements of RTCA DO-160G salt spray, sand dust, and mold test.

[0127] Based on the installation position of the double flap check valve, the double flap check valve is dynamically analyzed: the double flap check valve is installed in the outlet pipeline of the airborne compressor, and bears the axial air inlet impact and the radial vibration impact. The first order natural frequency of the double flap check valve is determined to be 185Hz through modal analysis, so as to avoid the range of 150Hz±20% of the engine main frequency. The dynamic balance level of the double flap check valve reaches G2.5, so as to avoid resonance to cause structural fatigue. Meanwhile, the size of the flange interface of the double flap check valve and the bolt pretightening force are optimized, so as to ensure the installation reliability of the double flap check valve. Among them: the flange interface adopts 4Y X0 INAS 16.0518.5 standard flange.

[0128] The working condition parameters obtained from the working condition environment of the double flap check valve are extended to obtain the following table 3:

[0129] Table 3, working condition parameter boundary condition expansion table

[0130]

[0131] The fluid medium characteristics passing through the double flap check valve are determined, the forward medium is high-pressure air containing 0.1% oil mist, and the reverse medium is high-temperature gas containing 5% water vapor and 1% SO2.

[0132] The performance index quantization model is established, and the performance index quantization model includes a leakage rate control model and a weight optimization model, and the leakage rate control model is specifically:

[0133] ;

[0134] Wherein: Q represents the leakage rate after the valve flap is closed; represents the sealing gap; represents the pressure difference on both sides of the valve flap; represents the viscosity of the gas fluid; and L represents the sealing length between the valve body and the valve flap.

[0135] The weight optimization model is specifically:

[0136] ;

[0137] Wherein: represents the material density of the valve body, which is 8.2g / cm 3 here; and V represents the volume of the valve body. represents the weight of the moving part, that is, the weight of the valve flap and the hinge shaft; represents the optimal weight under the premise of meeting the leakage rate requirement.

[0138] In order to better realize the present application, further, the performance index quantization model established in the step 1 includes a leakage rate control model and a weight optimization model, and the constraint condition of the performance index quantization model is:

[0139] ;

[0140] wherein: represents the maximum working stress of the valve body; represents the material allowable stress; f represents the modal frequency of the valve body; represents the working frequency of the engine in which the valve body is located, which is taken as = 150 Hz.

[0141] The two valve discs are designed to be dynamically balanced with different weights, the first valve disc weighs 30 g, the second valve disc weighs 25 g, and the center of mass of the two valve discs is offset by 2 mm relative to the center of mass of the valve body. A torque dynamic balance model of the two valve discs is established in this way:

[0142] M= ;

[0143] wherein: represents the weight of the first valve disc; represents the weight of the second valve disc; represents the moment length of the first valve disc relative to the center of mass, which is taken as = 15 mm; represents the moment length of the second valve disc relative to the center of mass, which is taken as = 12 mm; T represents the torsion received by the valve disc, which is taken as T = 0.045 N; represents the opening angle of the valve disc, which is taken as = 75°; M represents the torque of the valve disc.

[0144] The valve disc is stopped, and an adjustable stop device is designed. Through the adjustable stop device, for example, a stop bolt, a pre-tightening force of 5 N·m is applied to the valve disc, and the maximum opening angle of the valve disc is limited to 75 ± 2°.

[0145] The galvanic corrosion of the two valve discs is controlled, so that the potential difference between the two valve discs is less than or equal to 0.1 V. The first valve disc is made of Inconel material, and its potential is +0.35 V; the second valve disc is made of A286 material, and its potential is +0.28 V, the potential difference of the two valve discs is 0.07 V < 0.1 V.

[0146] The surface of the valve body is subjected to corrosion-resistant treatment, the inner surface of the valve body is plated with hard chromium and coated with PTFE; the hinge shaft between the valve disc and the valve body is subjected to nitriding treatment, the nitriding depth is greater than or equal to 0.15 mm, and the hinge shaft is lubricated with molybdenum disulfide, so that the friction coefficient between the hinge shaft and the valve disc is less than or equal to 0.15.

[0147] A stress distribution model of the sealing surface in contact between the valve body and the valve disc is established:

[0148] ;

[0149] wherein: represents the stress on the contact surface; P represents the pressure on the contact surface; D represents the diameter of the contact surface; b represents the width of the contact surface.

[0150] The taper surface sealing is adopted between the valve disc and the valve body, the damping bushing is arranged between the valve disc and the hinge shaft, and when the valve disc is closed, the viscous damping force provided by the damping bushing ensures that the closing speed of the valve disc is less than or equal to 1 m / s, thereby effectively reducing the impact on the valve disc when the valve disc is closed, and reducing the wear rate of the sealing surface by 35%.

[0151] The assembly model of the valve body and the valve disc is established, the tetrahedral mesh is divided for the assembly model, the mesh size is ≤2 mm, and the number of meshes is ≥800000. The inlet pressure boundary and the outlet mass flow boundary of the assembly model are determined, the turbulent flow model of the flow channel is established, and the convergence residual of the turbulent flow model of the flow channel is ≤10 -5 . The maximum fluid flow velocity of the valve disc throat is 29.5 m / s, the pressure drop is 1.4 bar, and the pressure recovery coefficient is 0.88.

[0152] The NACA0012 airfoil curve is used to optimize the inlet and outlet diffusion angle of the flow channel, the curvature radius R of the preselected flow channel is 60 mm, and the outlet diffusion angle is 15°, so as to reduce vortex separation and reduce the flow resistance of the flow channel by 12%.

[0153] A height of 3 mm of the flow guide boss is arranged on the flow surface of the valve disc, the flow guide boss guides the fluid to the middle of the flow channel, so that the scouring speed of the fluid on the sealing surface is reduced from 40 m / s to 25 m / s, so as to reduce the impact of the airflow on the sealing surface between the valve body and the valve disc, and reduce the wear rate of the sealing surface by 40%.

[0154] The strength representation of the valve disc, the valve body and the hinge shaft under different flow channel optimization results is analyzed by using solid solution treatment simulation, aging treatment simulation and nitriding treatment simulation.

[0155] For the valve disc, solid solution treatment is adopted: 1080℃×2h air cooling, so that the valve disc obtains uniform austenite;

[0156] For the valve body, aging treatment is adopted: 720℃×16h furnace cooling, so that the valve body precipitates phase strengthening, and the tensile strength at 271℃ is greater than or equal to 1300Mpa; The phase refers to the γ phase strengthening crystal precipitated in the Inconel alloy material during heat treatment.

[0157] The hinge shaft is treated by nitriding: 560℃×8h, the nitriding layer depth is 0.15mm, and the surface hardness of the hinge shaft reaches HV850.

[0158] The temperature field simulation is performed, and through finite element analysis, under the reverse 600℃ working condition, the following is obtained:

[0159] The sealing surface temperature is 580℃, the allowable temperature of the sealing surface material is 650℃, and the margin is 10%; the hinge shaft temperature is 450℃, the allowable temperature of the hinge shaft is 600℃, and the margin is 25%; the valve body temperature variation gradient is ≤50℃ / mm.

[0160] The valve body is manufactured by isothermal forging process, the temperature is controlled at about 950℃, the strain rate is 0.01 / s, and the grain size of the valve body is ensured to be less than or equal to 5 levels. After the valve body is forged, annealing treatment is performed, so that the hardness HB of the valve body is ≤220. The inner wall of the valve body is treated by pulse electroplating hard chromium, the thickness of the electroplated hard chromium layer is 0.03-0.05mm, the porosity is less than or equal to 5%, and the roughness of the inner wall of the valve body is less than or equal to 1.6μm.

[0161] The valve disc is cast by the lost wax method, the mold shell is high-temperature baked at 1500℃, and the metal liquid pouring temperature is 1380℃, so as to ensure that the size precision of the valve disc forming reaches CT4 level. The surface roughness of the valve disc is less than or equal to 3.2μm; the sealing surface of the valve disc is processed in the order of rough grinding, fine grinding and polishing, so that the flatness of the sealing surface is less than or equal to 0.001mm.

[0162] The valve body and the valve disc are cleaned by the ultrasonic cleaning process with a frequency of 40kHz and a power of 200w, the cleaning medium is isopropyl alcohol, and the cleaning time is greater than or equal to 15min. The valve body, the valve disc and the hinge shaft are assembled, and the assembly gap between the valve disc and the hinge shaft is 0.01-0.03mm.

[0163] The surface of the valve body is pretreated by sand blasting, the sand blasting particle size is 80-120mesh, and the surface roughness Ra of the valve body is ensured to be greater than or equal to 3.2μm; then PTFE coating is applied on the surface of the valve body by electrostatic spraying process, the spraying voltage is 60kV, the curing temperature is 380℃, the curing time is 30min, the thickness of the PTFE coating is 50±5μm; the titanium sacrificial anode is embedded in the flange surface of the valve body, so that the potential difference between the titanium sacrificial anode and the valve body is less than or equal to 0.05V.

[0164] The assembled double-disc one-way valve is subjected to forward pressure resistance test:

[0165] 35.3bar pressure is applied, the temperature is 271℃, the pressure is maintained for 5min, the valve body deformation amount is monitored by a laser displacement sensor, and the valve body deformation amount is required to be less than or equal to 0.05mm.

[0166] Reverse leakage test is conducted on the assembled double-disc check valve:

[0167] 3 bar reverse pressure is applied at room temperature 20℃, and the leakage rate is monitored by using a helium mass spectrometer leak detector, and the leakage rate is required to be less than or equal to 5x10 -9 mbar·L / s.

[0168] Vibration fatigue test is conducted on the assembled double-disc check valve, an electric vibration table is used to apply vibration load to the double-disc check valve, the acceleration range is 0-20g, the vibration frequency is 10-2000Hz, the test duration is equivalent to 50000h, and the machine is stopped every 2000h for detection.

[0169] Wear detection is conducted on the sealing surface, an industrial endoscope with a precision of 0.1mm is used to observe the morphology of the sealing surface and calculate the wear depth of the sealing surface.

[0170] The gap between the hinge shaft and the valve disc is detected, and the allowable gap error is less than or equal to 0.02mm.

[0171] Thermal cycle test is conducted on the assembled double-disc check valve, the double-disc check valve is tested in a high-low temperature alternating box at a cycle temperature of-50℃-600℃, the temperature change rate is 50℃ / s, the cycle test is 30min, the key size changes of the valve body, the valve disc and the hinge shaft are measured by a laser measuring instrument, and the allowable size change rate is less than or equal to 0.1%.

[0172] Acceleration life test is conducted on the double-disc check valve, the stress acceleration factor of the double-disc check valve is calculated, and the MTBF of the double-disc check valve is evaluated.

[0173] Finally, the following is obtained:

[0174] The valve body wall thickness is 2.5mm, the flow passage curvature radius R is 5mm, the valve disc opening angle is 70±2°, the 15° conical surface sealing is used between the valve body and the valve disc, and the leakage rate is 0.44g / s.

[0175] The first valve disc weighs 30g, the second valve disc weighs 25g, the mass center offset is 2mm, and the valve disc opening response speed is 0.1s.

[0176] The remaining contents of the embodiment are the same as those of embodiment 1, and thus will not be described again.

[0177] The above is only a preferred embodiment of the present application, and does not limit the present application in any form, and any simple modification or equivalent change made according to the technical essence of the present application to the above embodiment falls within the protection scope of the present application.

Claims

1. A design method of a double flap check valve for an aircraft, characterized in that, The method comprises the following steps: Step 1, based on the installation position of the double-poppet check valve, performing dynamic analysis on the double-poppet check valve to obtain working condition parameters, and establishing a performance index quantification model of the valve body based on the working condition parameters; Step 2, according to the performance index quantification model, performing unequal weight dynamic balance design, stop design, material compatibility and corrosion prevention design on the double valve poppet of the valve body; Step 3, based on the design result of step 2, modeling the valve body and valve poppet and performing fluid mechanics design simulation, and optimizing the flow channel and structural strength of the valve body based on the fluid mechanics simulation result; Step 4, based on the optimization result in step 3, processing and manufacturing the valve body and valve poppet, and assembling the valve body and valve poppet; Step 5, performing performance test and reliability verification on the assembled valve body and valve poppet; Step 6, iteratively optimizing the valve body and valve poppet, and repeating steps 2-5 until the valve body and valve poppet meet the design requirements; The performance index quantification model established in step 1 comprises a leakage rate control model and a weight optimization model, and the leakage rate control model is specifically: ； wherein: Q represents the leakage rate after the valve disc is closed; represents the sealing gap; represents the pressure difference on both sides of the valve disc; represents the viscosity of the gas fluid; L represents the sealing length between the valve body and the valve disc; The weight optimization model is specifically: ； wherein: represents the material density of the valve body; V represents the volume of the valve body; represents the weight of the moving parts, i.e. the weight of the valve disc and the hinge shaft; represents the optimal weight under the premise of meeting the leakage rate requirement; The performance index quantification model established in step 1 comprises a leakage rate control model and a weight optimization model, and the constraint condition of the performance index quantification model is: ； Wherein: represents the maximum working stress of the valve body; represents the material allowable stress; f represents the modal frequency of the valve body; represents the working frequency of the engine in which the valve body is located.

2. The method of designing a double flap check valve for an aircraft as defined in claim 1, wherein, The step 2 specifically comprises: Step 2.1, establishing a double-valve poppet torque dynamic balance model, and optimizing the opening angle and motion trajectory of the valve poppet through the double-valve poppet torque dynamic balance model; Step 2.2, designing an adjustable stop device, and adjusting the opening angle of the valve poppet to 75±2° through the adjustable stop device; Step 2.3, controlling the galvanic corrosion of the two valve poppets, so that the potential difference between the two valve poppets is less than or equal to 0.1V; performing corrosion-resistant treatment on the surface of the valve body; and performing nitriding treatment on the hinge shaft between the valve poppet and the valve body; Step 2.4, establishing a stress distribution model of the contact sealing surface between the valve body and the valve poppet, and establishing a conical sealing surface between the valve body and the valve poppet; Step 2.5, setting a damping bushing between the valve poppet and the hinge shaft to ensure that the viscous damping force when the valve poppet is closed is less than or equal to 5N; and calculating the specific pressure of the sealing surface between the valve body and the valve poppet to optimize the area of the sealing surface between the valve body and the valve poppet.

3. The method of designing a double flap check valve for an aircraft as defined in claim 2, wherein, The double-valve poppet torque dynamic balance model in step 2.1 is specifically: M= ； wherein: represents the weight of the first valve disc; represents the weight of the second valve disc; represents the length of the moment of force of the first valve disc relative to the center of mass; represents the length of the moment of force of the second valve disc relative to the center of mass; T represents the torque to which the valve disc is subjected; represents the opening angle of the valve disc; M represents the torque of the valve disc.

4. The method of designing a double flap check valve for an aircraft as defined in claim 1, wherein, The step 3 specifically comprises: Step 3.1, establishing an assembly model of the valve body and the valve poppet, performing tetrahedral mesh division, determining the inlet pressure boundary and outlet mass flow boundary of the assembly model, establishing a turbulent flow model of the flow channel to analyze the maximum flow velocity position, pressure drop position and pressure recovery position of the assembly model; Step 3.2, optimizing the flow channel inlet and flow channel outlet diffusion angle by using NACA0012 airfoil curve, and setting a flow guide boss on the flow surface of the valve poppet to reduce the impact of airflow on the sealing surface between the valve body and the valve poppet; Step 3.3, performing solid solution treatment simulation, aging treatment simulation and nitriding treatment simulation to optimize and analyze the strength characteristics of the valve poppet, valve body and hinge shaft under different flow channel optimization results; Step 3.4, based on the working condition parameters, temperature field simulation is performed on the valve body, valve disc, hinge shaft and sealing surface, the thermal expansion amount of the valve body, valve disc and hinge shaft is calculated, and the gap between the valve body, valve disc, hinge shaft and sealing surface is compensated based on the thermal expansion amount.

5. The method of designing a double flap check valve for an aircraft as defined in claim 1, wherein, The step 4 specifically comprises: Step 4.1, the valve body is manufactured by adopting isothermal forging process, and the inner wall of the valve body is subjected to pulse electroplating hard chromium treatment, the thickness of the electroplated hard chromium layer is 0.03-0.05mm, the porosity is less than or equal to 5%, and the roughness of the inner wall of the valve body is less than or equal to 1.6μm; Step 4.2, the valve disc is cast by adopting the lost wax method, the surface roughness of the valve disc is less than or equal to 3.2μm, and the sealing surface of the valve disc is processed by adopting the sequence of rough grinding, fine grinding and grinding, so that the flatness of the sealing surface is less than or equal to 0.001mm; Step 4.3, the valve body and valve disc are cleaned by adopting the ultrasonic cleaning process, and the valve body, valve disc and hinge shaft are assembled, the assembly gap between the valve disc and hinge shaft is 0.01-0.03mm; Step 4.4, the surface of the valve body is subjected to sand blasting pretreatment, the sand blasting particle size is 80-120mesh, then the PTFE coating is applied on the surface of the valve body by adopting the electrostatic spraying process, the thickness of the PTFE coating is 50±5μm, and the titanium sacrificial anode is embedded on the flange surface of the valve body, so that the potential difference between the titanium sacrificial anode and the valve body is less than or equal to 0.05V.

6. The method of designing a double flap check valve for an aircraft as defined in claim 1, wherein, The step 5 specifically comprises: Step 5.1, the assembled double-disc one-way valve is subjected to forward pressure resistance test and reverse leakage test; Step 5.2, the double-disc one-way valve is subjected to fatigue test; Step 5.3, the double-disc one-way valve is subjected to accelerated life test and MTBF evaluation.

7. The method of designing a double flap check valve for an aircraft as defined in claim 1, wherein, The step 6 specifically comprises: Step 6.1, a mathematical model related to the pressure drop and the curvature radius of the flow channel is established based on the response surface method, and a constraint condition of the curvature radius is set; Step 6.2, the optimal curvature radius of the flow channel is solved by adopting the genetic algorithm; Step 6.3, the wall thickness of the valve body is subjected to lightweight iteration, and the optimal wall thickness of the valve body is searched under the premise of meeting the safety coefficient requirement and the modal frequency avoidance requirement.

8. The method of designing a double flap check valve for an aircraft as defined in claim 7, wherein, The mathematical model established in the step 6.1 is specifically: ； wherein: represents the pressure drop; R represents the radius of curvature of the flow channel; The constraint condition of the curvature radius is R≥5mm.

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