Method for analyzing influence of helicopter fairing on vibration

Abstract

The invention belongs to the technical field of helicopter dynamics design, and discloses a method for analyzing the influence of a helicopter fairing on vibration, which comprises the following steps of: 1, acquiring test flight actual measurement data, and processing and analyzing vibration data characteristics of typical positions at typical moments; 2, determining the vibration influence mechanism of the fairing; 3, classifying vibration mechanisms, and analyzing main influence factors; 4, classifying ways for solving the vibration problem; 5, fairing optimization is conducted according to different ways; step 6, carrying out test flight verification and result comparison; step 7, if verification shows that the vibration problem disappears, ending; and if the verification shows that the vibration problem still exists, repeating the steps 5-6 until the vibration problem disappears. According to the method, the problem that helicopter vibration is caused by fairing design is solved, a universal method for solving the problem can be obtained, and the method has high engineering value in vibration problem investigation, vibration control plans and other work.

Description

Technical Field

[0001] The present invention belongs to the technical field of helicopter dynamics design and vibration control, and in particular relates to a method for analyzing the influence of a helicopter fairing on vibration. Background Art

[0002] Helicopter fairing design affects both drag and performance, and can also cause vibration issues. With increasing user demand for high-speed, highly maneuverable, and comfortable helicopter missions, fairing-induced vibration issues are becoming increasingly prominent. Fairings with protruding features, such as the rotor hub, radar antenna, and rescue winch, are particularly susceptible to vibration issues. Furthermore, due to the varying airflow directions created by the helicopter's attitude and the speed combinations associated with forward flight, climb, and descent, the tail structure can, under certain conditions, be trapped in the vortex behind the fairing, leading to significant performance variations, vibration, and structural fatigue. This interaction between aerodynamic forces and the structure presents a new challenge in helicopter design. This interaction is exacerbated by higher rotor blade loads, more compact overall layouts, and the need for increased maneuverability. Helicopter fairings are typically streamlined. However, changes in helicopter attitude and incoming airflow can cause these streamlined shapes to become blunt or even form drag surfaces, generating strong downstream vortices. The airflow drives the trailing vortex downstream, and at a specific combination of horizontal and vertical velocities, it hits the helicopter's tail structures, including the vertical and horizontal tail, causing excitation to the helicopter's tail structure. The trailing vortex, acting as a pulsating excitation, can stimulate the response of the structural components' natural modes. For the entire helicopter, this causes a response dominated by the first-order lateral bending mode of the fuselage. Due to the presence of structural damping, the natural mode response will decay freely, and the next vortex pulsation will again stimulate a vibration response. The resulting alternating process of increasing, decaying, and then increasing again in the vibration response creates a special vibration phenomenon known as sieving or shaking. Sieving or shaking is a vibration problem often encountered during helicopter flight tests. Its source is generally the fairings on the hub, main reducer, rotor shaft, engine intake and exhaust, and equipment compartment. The relative position of the fairing and the tail structure determines the state of vibration problems, such as the screening vibration problem in a certain state of a certain type of helicopter, the shaking problem of an antenna installed on a certain type of aircraft, the screening vibration problem after a certain type of aircraft is installed with test and modification equipment, and the abnormal fatigue life problem of the horizontal tail load on a certain type of aircraft.

[0003] This paper analyzes the causes and mechanisms of helicopter vibration problems caused by fairings, which are often encountered in the current domestic model development process. From an aerodynamic perspective, it explains the key factors of aerodynamic interference between the rotor and the fuselage, analyzes the causes and mechanisms of helicopter vibration problems caused by fairings, and provides a design method to avoid or eliminate the influence of fairings on helicopter vibrations.

[0004] The innovation of the present invention is that it proposes for the first time that a streamlined fairing design can reduce helicopter vibration problems caused by disturbances. Traditional fairings are generally designed from the perspective of reducing resistance, and rarely pay attention to the vibration and fatigue problems caused by the fairing and whether they can improve helicopter performance. Only when problems are encountered during test flights are corresponding problems addressed and remedial measures are taken to solve the problems. The present invention forms a general analysis method for solving the vibration problems affected by helicopter fairings and applies it to actual engineering design.

[0005] Through a typical engineering example, the vibration levels of two helicopter fairings with slight differences were compared, demonstrating that even small differences in fairings can cause significant vibration problems in helicopters, and that the design method proposed in this invention can be a universal solution to such problems. The development of an engineering design method that can address the significant vibration caused by helicopter fairings is particularly important. Flight tests have verified the accuracy and feasibility of this analysis method, demonstrating its high engineering value in vibration problem troubleshooting and vibration control planning. Summary of the Invention

[0006] Aiming at the problem of helicopter vibration caused by fairing, this paper proposes an analysis method for the influence of helicopter fairing on vibration. From the perspective of aerodynamics, this paper explains the key factors of aerodynamic interference such as the rotor and the fuselage, analyzes the causes and mechanisms of the helicopter vibration problem caused by the fairing, and provides a design method to avoid or eliminate the influence of the fairing on helicopter vibration.

[0007] The technical solution of the present invention is achieved as follows:

[0008] In a first aspect, the present invention discloses a method for analyzing the effect of a helicopter fairing on vibration, comprising the following steps:

[0009] Step 1: Obtain flight test data and process and analyze the vibration data characteristics at typical locations at typical times;

[0010] Step 2: Determine the mechanism by which the fairing affects vibration;

[0011] Step 3: Classify the vibration mechanism and analyze the main influencing factors;

[0012] Step 4: Categorize the approaches to solving the vibration problem;

[0013] Step 5: Optimize the fairing according to different approaches;

[0014] Step 6: Test flight verification and result comparison;

[0015] Step 7: If the verification shows that the vibration problem has disappeared, then end; if the verification shows that the vibration problem still exists, repeat steps 5-6 until the vibration problem disappears.

[0016] As a further solution of the present invention: Step 1 specifically includes the following steps:

[0017] Step 11: Based on the flight test data, find the flight parameter data and vibration data characteristics of the typical speed during the period of high vibration;

[0018] Step 12: Determine the abnormal vibration state through flight parameter test data. Specifically, when the pilot reports abnormal vibration, locate the abnormal state described by the pilot based on the speed, altitude, and vertical speed parameters corresponding to the vibration described by the pilot through flight parameter test data.

[0019] Step 13: Based on the abnormal vibration status determined in the above steps, analyze the vibration data of the corresponding status: use a general filtering program to perform bandpass filtering of different frequency bands on the selected vibration data to determine the vibration data characteristics of the corresponding status.

[0020] As a further solution of the present invention: the flight parameter data includes:

[0021] Helicopter flight status parameters: speed, pressure altitude, and ascent and descent rate;

[0022] Helicopter attitude parameters: pitch angle, roll angle, sideslip angle, angular rate;

[0023] Helicopter control parameters: collective pitch, cyclic pitch;

[0024] The flight parameter data used can be one of the above parameters or a combination of several parameters.

[0025] As a further solution of the present invention: Step 2 is specifically:

[0026] The low-frequency jitter / sifting abnormal vibration problem caused by the fairing occurs in a specific state. The excitation source and the main propagation path can be determined by combining the speed, lift rate, attitude angle and the relative position of the tail structure.

[0027] At the corresponding speed and attitude combination, strong vortex shedding is generated. The vortex shedding acts as a pulsating excitation on the tail structure, causing a response mainly in the lateral mode of the fuselage, resulting in lateral screening problems under the corresponding state. The fairing vortex shedding causes abnormal vibration of the whole aircraft, such as low-frequency screening / shaking.

[0028] According to the data characteristics given in step 1, it is determined that there is obvious lateral screening phenomenon, which occurs at intervals of about 1 to 2 seconds. This is a typical problem of helicopter vibration caused by aerodynamic interference.

[0029] As a further solution of the present invention: Step 3 is specifically:

[0030] The mechanism by which the fairing affects vibration is determined to be aerodynamic interference. Aerodynamic interference is divided into downwash, ground-level, and other types. The main influencing factors are as follows:

[0031] Downwash: This includes the wake generated by the main rotor, main hub, fuselage, and landing gear, which interferes with the tail structure. The main problems caused include changes in the fuselage angle of attack, tail load redistribution, load chaos, and vibration of the entire aircraft / tail structure.

[0032] Near-ground type: including the main rotor, tail rotor, and fuselage under the influence of turbulent vortex and boundary effects on the ground, causing load changes, power demand changes, and noise increase;

[0033] Other types: including mutual interference between helicopters and other aircraft and obstacles.

[0034] As a further solution of the present invention: Step 4 is specifically:

[0035] The problem of helicopter vibration or screening caused by the fairing can be solved from the source, path or other three aspects;

[0036] Solve the problem from the source: optimize the design of the fairing at the corresponding position to improve its streamline in various possible flow directions. Try to use curved surfaces instead of flat surfaces to prevent serious shedding vortices.

[0037] Solution from the perspective of path: By optimizing the relative position of the fairing and the tail structure, the shedding vortex generated under the possible flight attitude, speed and downwash combination of the helicopter can be prevented from exciting the tail structure;

[0038] Others: When the fairing itself and its relative position cannot be changed, it is possible to add turbulence in the path to change the direction of the airflow to prevent the shedding vortex from exciting the tail structure.

[0039] As a further solution of the present invention: the step 5 is specifically: adopting a method of solving the vibration from the source - optimizing the fairing design;

[0040] Changes in the helicopter's attitude and the direction of the incoming flow cause some streamlined shapes to become blunt bodies, and even form drag surfaces. Based on the combination of attitude and incoming flow direction, the blunt surfaces at the corresponding positions are optimized to streamlined shapes to avoid the generation of strong wake vortices downstream.

[0041] As a further solution of the present invention: the method for judging the streamline is:

[0042] Use the Reynolds number to measure the streamline of an object:

[0043] ;

[0044] Where U is the incoming flow velocity, D is the width perpendicular to the flow velocity, and ν is the kinematic viscosity;

[0045] When the Reynolds number is greater than 50, a regular vortex appears behind the object, and the tail vortex has a pulsating characteristic. The flow characteristics of the incoming flow and the tail vortex are the direct cause of the exciting force acting on the object.

[0046] In a second aspect, the present invention discloses an electronic device, comprising: a processor and a memory storing a computer program, wherein when the processor runs the computer program, the steps of the above-mentioned analysis method are executed.

[0047] In a third aspect, the present invention discloses a computer storage medium storing a computer program, which, when executed by a processor, performs the steps of the above-mentioned analysis method.

[0048] The beneficial effects of this application are:

[0049] 1. This application proposes a method and approach for analyzing and processing the vibration affected by helicopter fairings, which can obtain a general method for solving such problems, meet the pilot's physical needs before and after fairing adjustment, and provide an accurate and reliable vibration level assessment method for strength design.

[0050] 2. This application analyzes the characteristics of the test flight data to derive the mechanism and solution of the vibration data. The lateral screening problem in the corresponding state disappears. Within the entire flight envelope, there is no lateral screening problem caused by the fairing. The problem of the fairing affecting the high-frequency vibration is solved, and a general analysis method and process for this type of problem is formed.

[0051] 3. According to the present invention, an effective analysis method for helicopter vibration problems caused by helicopter fairings can be obtained, ensuring the requirement for reducing vibration levels after fairing adjustment, providing an accurate and reliable vibration level assessment method for helicopter strength design, and enabling more precise strength design. It has high universality and engineering application value.

[0052] The present application is described in further detail below with reference to the accompanying drawings of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of a method for analyzing the influence of a helicopter fairing on vibration according to the present invention;

[0054] Figure 2 This is a schematic diagram of a time domain curve of flight speed involved in the present invention;

[0055] Figure 3 This is a schematic diagram of a time domain curve of a flight rate of ascent and descent involved in the present invention;

[0056] Figure 4 This is a schematic diagram of a time domain curve of vibration at the driver's position involved in the present invention;

[0057] Figure 5 This is a schematic diagram of aerodynamic interference involved in the present invention;

[0058] Figure 6 1. It is a schematic diagram comparing the propeller hub fairing before and after optimization according to the present invention;

[0059] Figure 7 This is a typical schematic diagram of vortex flow through a cylinder. DETAILED DESCRIPTION

[0060] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Throughout the drawings, identical or similar reference numerals represent identical or similar elements or elements having identical or similar functions. The described embodiments are only some, not all, of the embodiments of the present invention.

[0061] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0062] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0063] The following is combined with Figure 1-7 The embodiments of the present invention are described in detail.

[0064] Example 1

[0065] The present invention provides a method for analyzing the influence of a helicopter fairing on vibration, which comprises the following steps:

[0066] Step 1: Obtain the actual test flight data, and process and analyze the vibration data characteristics at typical times and locations within the valid time period of the test flight data.

[0067] The step 1 specifically includes the following steps:

[0068] Step 11: Based on the flight test data, find the flight parameter data and vibration data characteristics of the typical speed during the period of high vibration;

[0069] Step 12: Determine the abnormal vibration state through flight parameter test data. Specifically, when the pilot reports abnormal vibration, locate the abnormal state described by the pilot through flight parameter test data based on the speed, altitude, and lift speed corresponding to the vibration described by the pilot. The flight parameter test data can be helicopter flight state parameters such as speed, pressure altitude, and lift rate; helicopter attitude parameters such as pitch angle, roll angle, sideslip angle, and angular rate; helicopter control parameters such as collective pitch and cyclic pitch; or a combination of several parameters.

[0070] Step 13: Based on the abnormal vibration status determined in the above steps, analyze the vibration data of the corresponding status: use a general filtering program to perform bandpass filtering of different frequency bands on the selected vibration data to determine the vibration data characteristics of the corresponding status.

[0071] Step 2: Determine the mechanism by which the fairing affects vibration.

[0072] The step 2 is specifically as follows:

[0073] Usually, the low-frequency jitter / screening abnormal vibration problem caused by the fairing occurs in a specific state. According to the combination of the level flight speed, ascent and descent rate, attitude angle, etc. in the corresponding state, combined with the relative position of the tail structure, the location of the excitation source and the main propagation path can be basically achieved.

[0074] Under the corresponding speed and attitude combination, strong shedding vortex is generated. The shedding vortex acts as a pulsating excitation on the tail structure, causing a response mainly in the lateral mode of the fuselage, causing a lateral screening problem under the corresponding state. The shedding vortex of the fairing causes abnormal vibration of the whole machine with low-frequency screening / shaking.

[0075] According to the data characteristics given in step 1, there is obvious lateral screening phenomenon, which generally occurs at intervals of about 1 to 2 seconds. This problem is a typical problem of helicopter vibration caused by aerodynamic interference.

[0076] Step 3: Classify the vibration mechanism and analyze the main influencing factors.

[0077] The step 3 is specifically as follows:

[0078] The mechanism by which the fairing affects vibration is determined to be aerodynamic interference, a common phenomenon in helicopters. Research on aerodynamic interference primarily focuses on the interaction between the dynamic characteristics of the airflow, the helicopter's aerodynamic unit, and the ground. A helicopter's aerodynamic unit primarily consists of the main rotor, tail rotor, fuselage, fairing, and horizontal stabilizer. Aerodynamic interference is primarily determined by factors such as the unit's geometry, relative position, relative wind speed and direction, and downwash velocity.

[0079] Aerodynamic interference is divided into downwash, near-ground, and other types. The main influencing factors are as follows:

[0080] For downwash, the main influencing factors include the wake generated by the main rotor, main hub, fuselage, and landing gear, which interferes with the tail structure such as the tail rotor, vertical stabilizer, and horizontal stabilizer. The problems caused mainly include changes in the fuselage angle of attack, tail load redistribution, load chaos, and vibration of the entire aircraft / tail structure.

[0081] For near-ground aircraft, the main influencing factors include load changes, power demand changes, and noise increases caused by the turbulent vortex and boundary effects on the ground for the main rotor, tail rotor, and fuselage.

[0082] For other types, the main influencing factors include mutual interference between the helicopter and other aircraft and obstacles.

[0083] Step 4: Categorize approaches to resolving the vibration problem.

[0084] The step 4 is specifically as follows:

[0085] The problem of helicopter vibration or screening caused by the fairing can be solved from the source, path or other three aspects;

[0086] Solve the problem from the source: optimize the design of the fairing at the corresponding position to improve its streamline in various possible incoming flow directions. Try to use curved surfaces and avoid flat surfaces (drag surfaces) to prevent the generation of serious shedding vortices.

[0087] Solution from the perspective of path: By optimizing the relative position of the fairing and the tail structure, the shedding vortex generated under the possible flight attitude, speed and downwash combination of the helicopter can be prevented from exciting the tail structure;

[0088] Others: When the fairing itself and its relative position cannot be changed, it is possible to add turbulence in the path to change the direction of the airflow to prevent the shedding vortex from exciting the tail structure.

[0089] Step 5: Optimize the fairing according to different approaches.

[0090] The step 5 specifically includes: in order to reduce the vibration level, according to the characteristics of the vibration data, the mechanism of the fairing affecting the vibration is determined, and the fairing is optimized: the method of solving the vibration from the source is adopted - optimizing the fairing design;

[0091] Generally, the fairing of a helicopter is designed to be streamlined. Changes in the helicopter's attitude and the direction of the incoming flow will cause some streamlined shapes to become blunt bodies, and even form drag surfaces. Based on the combination of attitude and incoming flow direction, the blunt surfaces at the corresponding positions are optimized to streamlined shapes to avoid the generation of strong tail vortices downstream.

[0092] The method for determining the streamline is as follows:

[0093] Use the Reynolds number to measure the streamline of an object:

[0094] ;

[0095] Where U is the incoming flow velocity, D is the width perpendicular to the flow velocity, and ν is the kinematic viscosity;

[0096] When the Reynolds number is greater than 50, a regular vortex appears behind the object, and the tail vortex has a pulsating characteristic. The flow characteristics of the incoming flow and the tail vortex are the direct cause of the exciting force acting on the object.

[0097] Step 6: Test flight verification and result comparison;

[0098] Step 7: If the verification shows that the vibration problem has disappeared, then end; if the verification shows that the vibration problem still exists, repeat steps 5-6 until the vibration problem disappears.

[0099] Ultimate goal:

[0100] The vibration levels before and after the fairing was changed were verified through test flights. The test flight results showed that the lateral screening problem in the corresponding state disappeared, and within the entire flight envelope, there was no lateral screening problem caused by the hub fairing.

[0101] By analyzing the characteristics of the test flight data, the mechanism of the vibration data and the solution are derived. The lateral screening problem in the corresponding state disappears. Within the entire flight envelope, the lateral screening problem caused by the fairing no longer exists. The problem of the fairing affecting vibration is solved, and a general analysis method and process for this type of problem are formed.

[0102] Example 2

[0103] In order to prove the applicability and effectiveness of the present invention, an analysis and comparison is conducted through actual measured data of a certain type of machine. The specific process is as follows:

[0104] S1. During a certain helicopter research test flight, at a speed of 180 km / h and a descent rate of about 3-5 m / s, there was an obvious lateral screening phenomenon, which occurred at intervals of about 1 to 2 seconds. The corresponding level flight speed, ascent rate, and vibration signals at the pilot's position were as follows: Figures 1 to 4 shown.

[0105] S2. Determine that the mechanism by which the fairing affects vibration is aerodynamic interference.

[0106] According to aerodynamic analysis, there is a plane on the top of the hub fairing in the original state, which generates strong shedding vortices under the corresponding speed and attitude combination. The shedding vortex acts as a pulsating excitation on the tail structure, causing a response mainly in the lateral mode of the fuselage, causing a lateral screening problem under the corresponding state. The shedding vortex of the fairing causes low-frequency screening / shaking of the entire machine, which is a common aerodynamic interference problem in the current helicopter development.

[0107] S3. Classification of aerodynamic interference and its main influencing factors;

[0108] For downwash, the main influencing factors include the wake generated by the main rotor, main hub, fuselage, and landing gear, which interferes with the tail structure, such as the tail rotor, vertical stabilizer, and horizontal stabilizer. This can cause problems such as changes in the fuselage's angle of attack, tail load redistribution, load dislocation, and vibration of the entire aircraft / tail structure. For localized problems, the main factors include the interaction between adjacent components, such as the main rotor, tail rotor, fuselage, power plant, and landing gear. These problems can include surface pressure fluctuations, load fluctuations, increased power demand, and tail rotor blockage. Near-ground problems primarily involve load changes, power demand changes, and increased noise caused by the turbulent ground vortices and boundary effects on the main rotor, tail rotor, and fuselage. Other types include interference between the helicopter and other aircraft and obstacles. This example falls into the downwash category, primarily due to the backward shedding vortex generated by the blunt surface of the hub fairing at the appropriate speed and attitude. This vortex acts as a pulsating pressure, generating an excitation force on the tail, causing a modal response of the entire aircraft and resulting in lateral screening.

[0109] S4. Process for handling large vibration caused by fairing;

[0110] For helicopter vibration or screening problems caused by the fairing, we usually start from two aspects: the source or the path.

[0111] Regarding the source, the fairing in the corresponding position needs to be optimized to improve its streamline in all possible incoming flow directions. Curved surfaces should be used whenever possible, avoiding flat surfaces (drag surfaces) to prevent the generation of severe shedding vortices. Regarding the path, it is recommended to optimize the relative position of the fairing and the tail structure to prevent the shedding vortices generated under the helicopter's possible flight attitude, speed, and downwash combinations from exciting the tail structure. On the other hand, when the fairing itself and its relative position cannot be changed, adding turbulence to the path can be used to redirect the airflow and prevent the shedding vortices from exciting the tail structure.

[0112] S5. Solve the vibration from the source - optimize the fairing;

[0113] In order to reduce the vibration level, this embodiment determines the mechanism of the fairing affecting the vibration based on the characteristics of the vibration data and optimizes the fairing; the hub fairing is optimized to eliminate the top plane. Figure 5 shown.

[0114] S6. Test flight verification and comparison results;

[0115] The test flight verification results show that the lateral screening problem in the corresponding state has disappeared, and within the entire flight envelope, there is no lateral screening problem caused by the hub fairing.

[0116] S7. Conclusion.

[0117] By analyzing the characteristics of the test flight data, the mechanism of the vibration data and the solution are derived. The lateral screening problem in the corresponding state disappears. Within the entire flight envelope, the lateral screening problem caused by the fairing no longer exists. The problem of the fairing affecting the high-frequency vibration is solved, and a general analysis method and process for this type of problem is formed.

[0118] Example 3

[0119] The present invention provides an electronic device comprising: a processor and a memory storing a computer program. In practical applications, the number of processors may be one or more, and the number of memories may be one or more. When the processor executes the computer program, the analysis method applied to the electronic device is implemented.

[0120] The memory may be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. Non-volatile memory may include read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), ferromagnetic random access memory (FRAM), flash memory, magnetic surface memory, optical disk, or compact disc read-only memory (CD-ROM); magnetic surface memory may include magnetic disk memory or magnetic tape memory. Volatile memory may include random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), synchronous static random access memory (SSRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct rambus random access memory (DRRAM).

[0121] The memory of the present invention is used to store various types of data to support the operation of the electronic device. Examples of these data include: any computer program for operating on the electronic device, such as an operating system and an application; contact data; phone book data; messages; pictures; videos, etc. Among them, the operating system includes various system programs, such as a framework layer, a core library layer, a driver layer, etc., which are used to implement various basic services and process hardware-based tasks. The application program can include various applications, such as a media player (Media Player), a browser (Browser), etc., which are used to implement various application services. Here, the program that implements the method of the embodiment of the present invention can be included in the application program.

[0122] Example 4

[0123] The present invention also provides a computer storage medium storing a computer program. The computer storage medium may be a memory such as a ferromagnetic random access memory (FRAM), a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory, a magnetic surface mount memory, an optical disc, or a compact disc read-only memory (CD-ROM); or various devices including one or any combination of the above memories, such as a mobile phone, a computer, a tablet device, a personal digital assistant, etc. When the computer program stored in the computer storage medium is executed by a processor, the analysis method applied to the above electronic device is implemented.

[0124] So far, the purpose of the present invention has been achieved.

[0125] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing the influence of helicopter fairing on vibration, characterized in that: The following steps are involved: Step 1: Obtain flight test data and process and analyze the vibration data characteristics at typical locations at typical times; Step 2: Determine the mechanism by which the fairing affects vibration; Step 3: Classify the vibration mechanism and analyze the main influencing factors; Step 4: Categorize the approaches to solving the vibration problem; Step 5: Optimize the fairing according to different approaches; Step 6: Test flight verification and result comparison; Step 7: If the verification shows that the vibration problem has disappeared, then end; if the verification shows that the vibration problem still exists, repeat steps 5-6 until the vibration problem disappears.

2. The method for analyzing the influence of helicopter fairing on vibration according to claim 1, characterized in that: The step 1 specifically includes the following steps: Step 11: Based on the flight test data, find the flight parameter data and vibration data characteristics of the typical speed during the period of high vibration; Step 12: Determine the abnormal vibration state through flight parameter test data. Specifically, when the pilot reports abnormal vibration, locate the abnormal state described by the pilot based on the speed, altitude, and vertical speed parameters corresponding to the vibration described by the pilot through flight parameter test data. Step 13: Based on the abnormal vibration status determined in the above steps, analyze the vibration data of the corresponding status: use a general filtering program to perform bandpass filtering of different frequency bands on the selected vibration data to determine the vibration data characteristics of the corresponding status.

3. The method for analyzing the effect of helicopter fairing on vibration according to claim 2, characterized in that: The flight parameter data includes: Helicopter flight status parameters: speed, pressure altitude, and ascent and descent rate; Helicopter attitude parameters: pitch angle, roll angle, sideslip angle, angular rate; Helicopter control parameters: collective pitch, cyclic pitch; The flight parameter data used can be one of the above parameters or a combination of several parameters.

4. The method for analyzing the effect of helicopter fairing on vibration according to claim 3, characterized in that: The step 2 is specifically as follows: The low-frequency jitter / sifting abnormal vibration problem caused by the fairing occurs in a specific state. The excitation source and the main propagation path can be determined by combining the speed, lift rate, attitude angle and the relative position of the tail structure. At the corresponding speed and attitude combination, strong vortex shedding is generated. The vortex shedding acts as a pulsating excitation on the tail structure, causing a response mainly in the lateral mode of the fuselage, resulting in lateral screening problems under the corresponding state. The fairing vortex shedding causes abnormal vibration of the whole aircraft, such as low-frequency screening / shaking. According to the data characteristics given in step 1, it is determined that there is obvious lateral screening phenomenon, which occurs at intervals of about 1 to 2 seconds. This is a typical problem of helicopter vibration caused by aerodynamic interference.

5. The method for analyzing the effect of helicopter fairing on vibration according to claim 4, characterized in that: The step 3 is specifically as follows: The mechanism by which the fairing affects vibration is determined to be aerodynamic interference. Aerodynamic interference is divided into downwash, ground-level, and other types. The main influencing factors are as follows: Downwash: This includes the wake generated by the main rotor, main hub, fuselage, and landing gear, which interferes with the tail structure. The main problems caused include changes in the fuselage angle of attack, tail load redistribution, load chaos, and vibration of the entire aircraft / tail structure. Near-ground type: including the main rotor, tail rotor, and fuselage under the influence of turbulent vortex and boundary effects on the ground, causing load changes, power demand changes, and noise increase; Other types: including mutual interference between helicopters and other aircraft and obstacles.

6. The method for analyzing the effect of helicopter fairing on vibration according to claim 5, characterized in that: The step 4 is specifically as follows: The problem of helicopter vibration or screening caused by the fairing can be solved from the source, path or other three aspects; Solve the problem from the source: optimize the design of the fairing at the corresponding position to improve its streamline in various possible flow directions. Try to use curved surfaces instead of flat surfaces to prevent serious shedding vortices. Solution from the perspective of path: By optimizing the relative position of the fairing and the tail structure, the shedding vortex generated under the possible flight attitude, speed and downwash combination of the helicopter can be prevented from exciting the tail structure; Others: When the fairing itself and its relative position cannot be changed, it is possible to add turbulence in the path to change the direction of the airflow to prevent the shedding vortex from exciting the tail structure.

7. The method for analyzing the effect of helicopter fairing on vibration according to claim 6, characterized in that: The step 5 specifically includes: solving the vibration from the source - optimizing the fairing design; Changes in the helicopter's attitude and the direction of the incoming flow cause some streamlined shapes to become blunt bodies, and even form drag surfaces. Based on the combination of attitude and incoming flow direction, the blunt surfaces at the corresponding positions are optimized to streamlined shapes to avoid the generation of strong wake vortices downstream.

8. The method for analyzing the effect of helicopter fairing on vibration according to claim 7, characterized in that: The method for determining the streamline is as follows: Use the Reynolds number to measure the streamline of an object: ； Where U is the incoming flow velocity, D is the width perpendicular to the flow velocity, and ν is the kinematic viscosity; When the Reynolds number is greater than 50, a regular vortex appears behind the object, and the tail vortex has a pulsating characteristic. The flow characteristics of the incoming flow and the tail vortex are the direct cause of the exciting force acting on the object.

9. An electronic device, characterized in that: include: A processor and a memory storing a computer program, wherein when the processor runs the computer program, the analysis method according to any one of claims 1 to 8 is implemented.

10. A computer storage medium, characterized in that A computer program is stored, and when the computer program is executed by a processor, the analysis method according to any one of claims 1 to 8 is implemented.

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