Lightweight high-pressure-resistant helicopter blade structure design method

Abstract

The present application belongs to the technical field of helicopter structure component design, and particularly relates to a lightweight high-pressure-resistant helicopter blade structure design method. The steps are as follows: step one: developing a lightweight high-pressure-resistant helicopter blade multi-objective optimization design; step two: establishing a finite element model according to the blade multi-objective optimization design result, and performing a pressure-resistant simulation analysis; step three: analyzing the blade simulation analysis result to determine whether the multi-objective optimization design blade meets the requirements, if yes, then entering step five, if not, then performing step four; step four: perfecting the optimization target, and repeating steps one to three; step five: trial-producing the blade according to the design result; and step six: performing a water pressure test on the molded blade to confirm whether the blade meets the water pressure resistance requirements.

Description

Technical Field

[0001] This invention belongs to the field of helicopter structural component design technology, and specifically relates to a lightweight, high-pressure-resistant helicopter rotor blade structure design method. Background Technology

[0002] Currently, tiltrotor technology is one of the development directions for helicopter rotor technology, especially requiring aerodynamic / hydrodynamic efficiency in airborne helicopter mode, fixed-wing level flight mode, and underwater navigation mode. China lacks practical engineering experience in large conventional tiltrotor systems, and there are no precedents for large rotor systems that meet the requirements for air-water reuse. Basically, tiltrotor systems are used in airborne flight mode, where the rotor blades only need to fulfill the basic function of providing lift. However, for underwater navigation mode, the rotor blades need to be submerged for extended periods, so the blades must also meet hydrodynamic performance requirements and possess a certain degree of resistance to hydrostatic pressure during deep diving to prevent the blades from being crushed underwater, thus losing their basic lift-providing function. Currently, there is a lack of design experience in the domestic helicopter rotor blade structure design process. Summary of the Invention

[0003] Objective: To propose a lightweight, high-compression-resistance helicopter rotor blade structure design method. Based on this method, lightweight, high-compression-resistance rotor blade structures can be designed, avoiding design iterations, reducing development costs, and improving flight safety.

[0004] Technical solution

[0005] A lightweight, high-pressure-resistant helicopter rotor blade structure design method, comprising the following steps:

[0006] Step 1: Conduct multi-objective optimization design of lightweight, high-pressure-resistant helicopter rotor blades;

[0007] Step 2: Establish a finite element model based on the multi-objective optimization design results of the blades and conduct compressive simulation analysis;

[0008] Step 3: Analyze the simulation analysis results of the blade to determine whether the multi-objective optimization design of the blade meets the requirements. If it meets the requirements, proceed to Step 5; otherwise, proceed to Step 4.

[0009] Step 4: Refine the optimization goals and repeat steps 1 through 3;

[0010] Step 5: Prototype blades based on the design results;

[0011] Step 6: Conduct a water pressure resistance test on the molded blades to confirm whether the blades meet the water pressure resistance requirements.

[0012] Furthermore, step one includes the following processes:

[0013] a) Set optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity;

[0014] b) Set optimization constraints: installation interface, blade aerodynamic shape, rotor dynamics, rotor aeroelastic stability, blade static strength and blade fatigue strength;

[0015] c) Set optimization goals: lightest blade weight and strongest compressive strength;

[0016] d) Set the optimization algorithm: multi-population genetic algorithm.

[0017] Furthermore, in step one, the specific process is as follows:

[0018] a) Optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity;

[0019] b) Optimization constraints:

[0020] 1) Installation interface: Double pin connection to the propeller hub;

[0021] 2) Blade aerodynamic shape: The airfoil starts at 0.2R, with a large aerodynamic twist angle of -35° / R and a minimum thickness of 5.8mm;

[0022] 3) Rotor dynamics: At operating speeds of 700 r / min and 400 r / min, the rotor satisfies the requirement that the intervals between the natural frequencies of each mode of the rotor and the aerodynamic excitation frequency are greater than the minimum interval requirement, thus avoiding large vibrations;

[0023] 4) Rotor aeroelastic stability: The rotor is aeroelastically stable across the entire total torque control range at both 700 r / min and 400 r / min operating speeds; no flutter or other aeroelastic coupling instability occurs.

[0024] 5) Static strength of the blade: Minimum static strength margin ≥ 20.37%;

[0025] 6) Blade fatigue strength: fatigue life not less than 1000 Fh;

[0026] c) Optimization objective: The weight of a single propeller blade should not exceed 15 kg, theoretically meeting the requirement of normal operation at a depth of 150 meters underwater;

[0027] d) Optimized design results:

[0028] 1) High modulus composite material is used as the main material of the blade. The skin (1) is made of T800 woven carbon cloth with a tensile modulus E1 of 72Gpa, and the main beam (2) is made of T800 carbon fiber prepreg tape with a tensile modulus E1 of 130Gpa.

[0029] 2) The cavity is filled with foam (3), and the selected foam (3) has a compressive strength ≥ 1.5 MPa;

[0030] 3) The design weight of a single propeller blade is 14.2 kg;

[0031] 4) Meets normal operating requirements at a depth of 150 meters underwater;

[0032] 5) The blades meet the static strength requirements and have a fatigue life > 1000 Fh;

[0033] 6) The blades must meet the requirements of rotor dynamic characteristics and aeroelastic stability.

[0034] Furthermore, in step two, the specific process is as follows:

[0035] a) The simulation analysis components include skin (1), main beam (2), foam (3), reinforcing ribs (4), counterweight support (5), and frequency-modulated counterweight (6);

[0036] b) Structural pretreatment: The skin components are divided into sections according to the cutting position;

[0037] c) Material property settings: Set the material properties of the selected material;

[0038] d) Load setting: Apply a pressure of 1.5 MPa to the upper / lower surface of the blade;

[0039] e) Contact settings: The skin and foam are set to interference fit with an interference of 0.2mm; all other components are set to bond fit.

[0040] f) Boundary conditions: The left and right end faces of the blade are fixedly constrained, restricting the degrees of freedom in six directions;

[0041] g) Mesh setting: Due to the complex shape of the skin (1), main beam (2), foam (3), and frequency modulation counterweight (6), it is set as a tetrahedral mesh; the regular reinforcing rib (4) and counterweight support (5) are structural hexahedral meshes.

[0042] Furthermore, in step three, the first simulation analysis results show that the maximum stress near the counterweight support (5) and the tip of the paddle reaches 1.4 MPa. After analysis, it is found that the compressive strength margin of the foam (3) among the currently selected materials is not large, so we proceed to step four.

[0043] Furthermore, in step four, since the compressive strength margin of foam (3) is not large, the optimization objective "theoretically meets the normal operation at 150 meters underwater" is modified to "theoretically meets the normal operation at 200 meters underwater". The multi-objective optimization design of the blade is carried out again, and foam (3) with a compressive strength ≥ 2.0 MPa is selected. At the same time, there is a sudden change in stiffness at the junction of foam (3) and reinforcing rib (4), which leads to stress concentration. Therefore, the position and length of reinforcing rib (4) are adjusted.

[0044] Furthermore, in step four, the simulation analysis results are as follows: The stress simulation analysis results show that the area with the greatest stress is still the area near the counterweight support (5), with a stress of 1.5MPa. The stress level of each component of the blade is lower than the strength value of the material of each component. The weight of a single blade is 14.5Kg. The blade operates normally at a depth of 150 meters underwater, meeting the multiple objectives of the lightest blade weight and the strongest pressure resistance.

[0045] Furthermore, in step six, the water pressure test process is as follows:

[0046] a) Secure the blades in the water tank, ensuring that the blades are completely submerged in the water and do not come into contact with the water tank;

[0047] b) Place the water tank containing the paddles into the pressure tank;

[0048] c) Apply pressure through a pressurization tank, increasing the pressure from 0 MPa to 1.5 MPa, and then stabilizing the pressure at 1.5 MPa for one hour;

[0049] d) After the test, the blades were removed, their surfaces were dried, and they were weighed and visually inspected. The blades were found to be in good condition, with no skin dents or crushing. The weight change before and after the test was within 0.3%.

[0050] e) Increase the pressure to 1.6 MPa and repeat steps a), b), c), and d).

[0051] In summary, the beneficial effects of the present invention are as follows:

[0052] This invention proposes a lightweight, high-pressure-resistant helicopter rotor blade structure design method, forming a rapid and efficient design method that greatly improves design efficiency, avoids design iterations due to improper material selection and design, mitigates risks, reduces development costs, and improves helicopter safety. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of a design method for a lightweight, high-pressure-resistant helicopter rotor blade structure.

[0054] Figure 2 This is a schematic diagram of a lightweight, high-pressure-resistant helicopter rotor blade structure. Detailed Implementation

[0055] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0056] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0057] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0058] A lightweight, high-pressure-resistant helicopter rotor blade structure design method is proposed, which involves research on three aspects: multi-objective optimization design of the blade, finite element pressure simulation analysis, and hydrostatic verification test. Specific implementation details can be found by referring to [the relevant documentation / reference]. Figure 1 The specific steps and calculation examples are as follows:

[0059] Step 1: Conduct multi-objective optimization design of lightweight, high-pressure-resistant helicopter rotor blades;

[0060] a) Define the optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity;

[0061] b) Define optimization constraints: installation interface, blade aerodynamic shape, rotor dynamics, rotor aeroelastic stability, blade static strength, and blade fatigue strength;

[0062] c) Define optimization goals: lightest blade weight and strongest compressive strength.

[0063] d) Optimization algorithm: Multi-population genetic algorithm

[0064] Calculation example:

[0065] a) Optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity;

[0066] b) Optimization constraints:

[0067] 1) Installation interface: Double pin connection to the propeller hub;

[0068] 2) Blade aerodynamic shape: The airfoil starts at 0.2R, with an aerodynamic twist angle of -35° / R and a minimum thickness of 5.8mm;

[0069] 3) Rotor dynamics: At operating speeds of 700 r / min and 400 r / min, the rotor should maintain a certain interval between the natural frequencies of each mode and the aerodynamic excitation frequency to avoid large vibrations.

[0070] 4) Rotor aeroelastic stability: The rotor should be aeroelastically stable within the entire total torque control range at both operating speeds of 700 r / min and 400 r / min, without flutter or other aeroelastic coupling instability phenomena.

[0071] 5) Static strength of the blade: Minimum static strength margin ≥ 20.37%;

[0072] 6) Blade fatigue strength: fatigue life not less than 1000Fh.

[0073] c) Optimization objective: The weight of a single propeller blade should not exceed 15 kg, theoretically meeting the requirement of normal operation at a depth of 150 meters underwater;

[0074] d) Optimized design results:

[0075] 1) High modulus composite material is used as the main material of the blade. The skin (1) is made of T800 woven carbon cloth with a tensile modulus E1 of 72Gpa, and the main beam (2) is made of T800 carbon fiber prepreg tape with a tensile modulus E1 of 130Gpa.

[0076] 2) The cavity is filled with foam (3). In order to meet the normal operation at a depth of 150 meters underwater, the selected foam (3) has a compressive strength ≥1.5MPa;

[0077] 3) The design weight of a single propeller blade is 14.2 kg;

[0078] 4) The blades meet the static strength requirements and have a fatigue life of 1500 Fh;

[0079] 5) The blades must meet the requirements of rotor dynamic characteristics and aeroelastic stability.

[0080] Step 2: In order to confirm that the blades can work normally at a depth of 150 meters underwater, a finite element model was established based on the multi-objective optimization design results of the blades, and a pressure simulation analysis was performed.

[0081] a) The simulation analysis components include skin (1), main beam (2), foam (3), reinforcing ribs (4), counterweight support (5), and frequency-modulated counterweight (6);

[0082] b) Structural pretreatment: The skin components are divided into sections according to the cutting position;

[0083] c) Material property settings: Set the material properties of the selected material;

[0084] d) Load setting: Apply a pressure of 1.5 MPa to the upper / lower surface of the blade;

[0085] e) Contact settings: The skin and foam are set to interference fit with an interference of 0.2mm; all other components are set to bond fit.

[0086] f) Boundary conditions: The left and right end faces of the blade are fixedly constrained, restricting the degrees of freedom in six directions;

[0087] g) Mesh setting: Due to the complex shape of the skin (1), main beam (2), foam (3), and frequency modulation counterweight (6), it is set as a tetrahedral mesh; the regular reinforcing rib (4) and counterweight support (5) are structural hexahedral meshes.

[0088] Step 3: Analyze the simulation analysis results of the blade to determine whether the multi-objective optimization design of the blade meets the requirements. If it meets the requirements, proceed to step 6; otherwise, proceed to step 4.

[0089] Simulation analysis results: The maximum stress near the counterweight support (5) and the tip of the blade reaches 1.4MPa, which theoretically meets the requirements. However, considering the actual working conditions of the blade, a margin of 0.2MPa is required. After considering the margin, the selected foam compression strength does not meet the requirements. Therefore, we proceed to the fourth step to improve and optimize the target.

[0090] The fourth step is to refine the optimization objectives and redesign the multi-objective optimization of the blades according to the first step.

[0091] As can be seen from the third step, considering that the composite blade process has a significant impact on product quality, there will be some deviation between the actual and the design. The compressive strength margin of foam (3) is not large. Therefore, the optimization objective "theoretically meets the normal operation at 150 meters underwater" is improved to "theoretically meets the normal operation at 200 meters underwater". The multi-objective optimization design of the blade is carried out again, and foam (3) with a compressive strength ≥2.0MPa is selected. At the same time, there is a sudden change in stiffness at the junction of foam (3) and reinforcing rib (4), which leads to stress concentration. Therefore, the position and length of reinforcing rib (4) are adjusted.

[0092] Step 5: Repeat steps 2 and 3 until the blades meet multiple objectives, such as the lightest blade weight and the strongest compressive strength, and then proceed to step 6;

[0093] The results of the pressure simulation analysis show that the area with the greatest stress is still the area near the counterweight support (5), with a stress of about 1.5 MPa. The stress level of each component of the blade is lower than the strength value of the material of each component. The weight of a single blade is 14.5 Kg. The blade operates normally at a depth of 150 meters underwater, meeting the multiple objectives of the lightest blade weight and the strongest pressure resistance.

[0094] Step 6: Prototype blades based on the design results;

[0095] Step 7: Conduct a water pressure resistance test on the molded blades to confirm whether the blades meet the water pressure resistance requirements.

[0096] The method for water pressure resistance test is as follows:

[0097] a) Secure the blades in the water tank, ensuring that the blades are completely submerged in the water and do not come into contact with the water tank;

[0098] b) Place the water tank containing the paddles into the pressure tank;

[0099] c) Apply pressure through a pressurization tank, increasing the pressure from 0 MPa to 1.5 MPa, and then stabilizing the pressure at 1.5 MPa for one hour;

[0100] d) After the test, the blades were removed, their surfaces were dried, and they were weighed and visually inspected. The blades were found to be in good condition, with no skin dents or crushing. The weight change before and after the test was within 0.3%.

[0101] e) Taking into account a certain margin of safety, increase the pressure to 1.6 MPa and repeat steps a), b), c), and d).

[0102] The test results show that this example meets the water pressure resistance requirements, thus verifying the feasibility of the present invention.

[0103] In the multi-objective optimization design of helicopter rotor structure, water pressure resistance performance and lightweight performance indicators are added;

[0104] The skin (1) is made of T800 woven carbon cloth, and the beam (2) is made of T800 carbon fiber prepreg tape;

[0105] Foam (3) has a compressive strength ≥ 2.0 MPa;

[0106] The skin and foam are set to interference fit, with an interference amount of 0.2mm.

[0107] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A design method for a lightweight, high-pressure-resistant helicopter rotor blade structure, characterized in that: The steps are as follows: Step 1: Conduct multi-objective optimization design of lightweight, high-pressure-resistant helicopter rotor blades; Step 2: Establish a finite element model based on the multi-objective optimization design results of the blades and conduct compressive simulation analysis; Step 3: Analyze the simulation analysis results of the blade to determine whether the multi-objective optimization design of the blade meets the requirements. If it meets the requirements, proceed to Step 5; otherwise, proceed to Step 4. Step 4: Refine the optimization goals and repeat steps 1 through 3; Step 5: Prototype blades based on the design results; Step 6: Conduct a water pressure resistance test on the molded blades to confirm whether the blades meet the water pressure resistance requirements.

2. The method according to claim 1, characterized in that: Step one includes the following processes: a) Set optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity; b) Set optimization constraints: installation interface, blade aerodynamic shape, rotor dynamics, rotor aeroelastic stability, blade static strength and blade fatigue strength; c) Set optimization goals: lightest blade weight and strongest compressive strength; d) Set the optimization algorithm: multi-population genetic algorithm.

3. The method according to claim 2, characterized in that: Step one, the specific process is as follows: a) Optimization variables: blade flapping stiffness, oscillation stiffness, torsional stiffness, weight, and center of gravity; b) Optimization constraints: 1) Installation interface: Double pin connection to the propeller hub; 2) Blade aerodynamic shape: The airfoil starts at 0.2R, with a large aerodynamic twist angle of -35° / R and a minimum thickness of 5.8mm; 3) Rotor dynamics: At operating speeds of 700 r / min and 400 r / min, the rotor satisfies the requirement that the intervals between the natural frequencies of each mode of the rotor and the aerodynamic excitation frequency are greater than the minimum interval requirement. 4) Aeroelastic stability of the rotor: The rotor is aeroelastically stable across the entire total torque control range at both operating speeds of 700 r / min and 400 r / min. 5) Static strength of the blade: Minimum static strength margin ≥ 20.37%; 6) Blade fatigue strength: fatigue life not less than 1000 Fh; c) Optimization objective: The weight of a single propeller blade should not exceed 15 kg, theoretically meeting the requirement of normal operation at a depth of 150 meters underwater; d) Optimized design results: 1) High modulus composite material is used as the main material of the blade. The skin (1) is made of T800 woven carbon cloth with a tensile modulus E1 of 72Gpa, and the main beam (2) is made of T800 carbon fiber prepreg tape with a tensile modulus E1 of 130Gpa. 2) The cavity is filled with foam (3), and the selected foam (3) has a compressive strength ≥ 1.5 MPa; 3) The design weight of a single propeller blade is 14.2 kg; 4) Meets normal operating requirements at a depth of 150 meters underwater; 5) The blades meet the static strength requirements and have a fatigue life > 1000 Fh; 6) The blades must meet the requirements of rotor dynamic characteristics and aeroelastic stability.

4. The method according to claim 3, characterized in that: Step two involves the following specific steps: a) The simulation analysis components include skin (1), main beam (2), foam (3), reinforcing ribs (4), counterweight support (5), and frequency-modulated counterweight (6); b) Structural pretreatment: The skin components are divided into sections according to the cutting position; c) Material property settings: Set the material properties of the selected material; d) Load setting: Apply a pressure of 1.5 MPa to the upper / lower surface of the blade; e) Contact settings: The skin and foam are set to interference contact with an interference amount of 0.2mm, and all other components are set to bonded contact; f) Boundary conditions: The left and right end faces of the blade are fixedly constrained, restricting the degrees of freedom in six directions; g) Mesh setting: Due to the complex shape of the skin (1), main beam (2), foam (3), and frequency modulation counterweight (6), it is set as a tetrahedral mesh; the regular reinforcing rib (4) and counterweight support (5) are structural hexahedral meshes.

5. The method according to claim 4, characterized in that: In step three, the first simulation analysis results are: the maximum stress near the counterweight support (5) and the tip of the paddle reaches 1.4 MPa. After analysis, it is found that the compressive strength margin of the foam (3) among the currently selected materials is not large, so we proceed to step four.

6. The method according to claim 5, characterized in that: In step four, since the compressive strength margin of foam (3) is not large, the optimization objective "theoretically meets the normal operation at 150 meters underwater" is changed to "theoretically meets the normal operation at 200 meters underwater". The multi-objective optimization design of the blade is carried out again, and foam (3) with a compressive strength ≥2.0MPa is selected. At the same time, there is a sudden change in stiffness at the junction of foam (3) and reinforcing rib (4), which leads to stress concentration. Therefore, the position and length of reinforcing rib (4) are adjusted.

7. The method according to claim 6, characterized in that: In step four, the simulation analysis results are as follows: The stress simulation analysis results show that the area with the greatest stress is still the area near the counterweight support (5), with a stress of 1.5MPa. The stress level of each component of the blade is lower than the strength value of the material of each component. The weight of a single blade is 14.5Kg. The blade operates normally at a depth of 150 meters underwater, meeting the multiple objectives of the lightest blade weight and the strongest pressure resistance.

8. The method according to claim 7, characterized in that: In step six, the water pressure test process is as follows: a) Secure the blades in the water tank, ensuring that the blades are completely submerged in the water and do not come into contact with the water tank; b) Place the water tank containing the paddles into the pressure tank; c) Apply pressure through a pressurization tank, increasing the pressure from 0 MPa to 1.5 MPa, and then stabilizing the pressure at 1.5 MPa for one hour; d) After the test, the blades were removed, their surfaces were dried, and they were weighed and visually inspected. The blades were found to be in good condition, with no skin dents or crushing. The weight change before and after the test was within 0.3%. e) Increase the pressure to 1.6 MPa and repeat steps a), b), c), and d).

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