CN109916589B - Method for testing pressure change characteristics in airdrop cabin of large-size object of transport airplane - Google Patents
Method for testing pressure change characteristics in airdrop cabin of large-size object of transport airplane Download PDFInfo
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Abstract
The invention discloses a method for testing the pressure change characteristic in an air-drop cabin for transporting large-size objects of an airplane, which comprises an airplane model and an air-drop object model, wherein air-drop object model fixing columns are arranged on the lower wall near the front wall of the inner cabin of the airplane model, a plurality of fixing columns are arranged on the lower wall near the front wall of the inner cabin of the airplane model, a lead is connected and arranged in front of the air-drop object model, the air-drop object model is connected and fixed through constantan wires between the lead and the fixing columns, and a rear large cabin door is arranged behind the airplane model. The invention determines the similarity criterion for the pressure change test in the airdrop cabin of the large object of the transport airplane, provides a formula for converting the pressure in the cabin and the corresponding change time into the pressure change in the cabin and the corresponding change time in the airdrop under the flight condition during the test, provides a parameter calculation and model design method of an airdrop model and a traction parachute model, and establishes a method and a step for the pressure change wind tunnel test research in the airdrop cabin of the large object of the transport airplane.
Description
Technical Field
The invention relates to the technical field of ground tests and experimental aerodynamics of aircrafts such as airplanes and the like, in particular to a method for testing pressure change characteristics in an airdrop cabin of a large-size object of a transport airplane.
Background
The wind tunnel experiment is the most important and widely applied technical method for researching and verifying the aerodynamic characteristics of the aircraft in the development process of the aircraft; the theoretical basis of the wind tunnel experiment is a similarity principle, and the key of whether an accurate result can be obtained by a wind tunnel experiment method is the selection of a similarity criterion.
When the transporter airdrops a large-size object, the object has larger size compared with the cross section of the cargo hold, so that larger blockage degree is formed, when the object moves to a large cabin door behind the cabin under the action of the pulling force of the traction umbrella, the pressure of the front cabin can be rapidly changed, the operators in the front cabin are influenced, and even the auditory system of the operators is damaged; the research on the characteristic is extremely important for safe implementation of air drop; the following patents relating to the aerial delivery of a conveyor are obtained through a search of documents and patents.
Three dummy patent designs suitable for air drop and air drop experiments are disclosed in the Chinese patent offices CN104596784A, CN104596784B and CN204389793U of the China people's liberation force air force aviation medical research institute, a device capable of being used for heavy object air drop is disclosed in the patent CN1663883A of the China patent offices, and a method for pre-evaluating an air drop and air drop landing point is disclosed in the patent CN105320807A of the China patent offices.
The Nanjing university of aerospace has already studied on this, and patent CN104504174A in the Chinese patent office discloses a control method of an adaptive grid suitable for fluid-solid coupling numerical simulation in an air-drop process.
However, the above-mentioned patents are related to the airdrop of the transporter, but do not relate to the study of the pressure variation characteristics in the cabin during the airdrop of the large object of the transporter, and do not provide the corresponding wind tunnel test method or numerical simulation method.
Disclosure of Invention
The invention aims to provide a method for testing the pressure change characteristic in an airdrop cabin of a large-size object of a transport aircraft, which aims to solve the problems that the published or granted patents in the background art are related to airdrop and airborne landing of the transport aircraft, but do not relate to the research on the pressure change characteristic in the cabin in the process of airdrop of the large object of the transport aircraft, and a corresponding wind tunnel test method or a numerical simulation method is not provided.
In order to achieve the purpose, the invention provides the following technical scheme: a test method for pressure change characteristics in an airdrop cabin of a large-size object of a transport airplane comprises an airplane model and an airdrop object model, a slide rail is laid on the lower wall in the inner cabin of the airplane model, an airdrop model fixing column is arranged on the lower wall near the front wall of the inner cabin of the airplane model, a plurality of fixing columns are arranged on the lower wall near the front wall of the inner cabin of the airplane model, a lead is connected and arranged in front of the air-drop object model, the air-drop model is connected and fixed with the constantan wire between the fixed columns through the lead wire, a rear big cabin door is arranged at the rear part of the airplane model, the lower end of the rear big cabin door is provided with a cargo bridge model on the airplane model, the lower end of the rear part of the air-drop object model is provided with a model fixing column connected with a traction umbrella, an umbrella rope model is connected to the rear of the airdrop model, a traction umbrella model is fixedly connected to the rear of the umbrella rope model, and recovery nets are arranged below and behind the airplane model; and a high-speed camera is arranged in the wind tunnel on the same horizontal plane on the left side of the outlet of the big cabin door behind the airplane model and is used for shooting and calculating the cabin exit speed and the attitude of the air-dropped object model. The aircraft model cabin pressure monitoring system is characterized in that a plurality of dynamic pressure sensors are arranged on the front wall and the right wall in the aircraft model cabin and are powered by a voltage-stabilized power supply, a sensor acquisition signal line is communicated with a data acquisition system, and the pressure change in the aircraft model cabin in the moving and throwing-out process of a thrown object model in the cabin can be analyzed through the acquisition result of the acquisition system.
Before the formal test of the pressure change of the large-size object aerial drop front cabin, firstly, a standard aerial drop object aerial drop simulation test is carried out, the cabin outlet condition is recorded through a high-speed camera, the cabin outlet speed is calculated and compared with the value converted into the test state from the cabin outlet speed during actual flying aerial drop, the umbrella surface state of the traction umbrella model is adjusted, the condition that the tension coefficient is the same as the actual flying aerial drop condition is met, and the traction umbrella model is used for subsequent tests.
According to the large-size air-drop cabin internal pressure change characteristic test, under the condition that the shape of an air-drop object model is similar to the shape of an internal cabin, the influence of a test Mach number Ma and a Reynolds number Re can be ignored, firstly, the Froude number Fr of the model is ensured to be the same as the real object, meanwhile, the weight and aerodynamic force (torque) meet the power similarity criterion, and the initial speed and the initial angular speed meet the corresponding relation, so that the movement speed and the cabin internal pressure coefficient change of the space-time object-throwing model in the model test can be ensured to be basically similar to the real object; similar criteria to be met include;
(1) geometric similarity
The airplane model, the air-drop model, the traction parachute model and the parachute rope model all meet geometric similarity conditions; the requirements of the traction umbrella model and the umbrella rope model can be properly relaxed, the canopy thickness of the traction umbrella model can not be simulated, and the umbrella rope model can only consider enough strength.
(2) Froude number Fr
(3) Similar power, including large-size air-drop gravity and drag parachute tension
(4) Coefficient of pressure in cabin
In the present invention, the model and the real Froude number Fr are equal in formula (1), and gm＝gfThe velocity of the wind tunnel at the time of the test can be obtained as
According to the formula (2) of the power similarity condition, the air-drop object model bears the gravity GmGravity G borne by the material objectfThe ratio of which is equal to the ratio of the corresponding aerodynamic forces, and the coefficient of aerodynamic force cRm＝cRfAre equal to each other
Gm＝kρkl 3Gf(5)
According to the formula (2) of the power similarity condition, the traction force of the traction parachute model can be obtained to meet the requirement
Fm＝kρkl 3Ff(6)
Formulas (5) and (6) are used for calculating the weight of the aerial delivery model and the pulling force of the traction parachute model, and the aerial delivery model and the traction parachute model can be designed by combining the requirements of geometric similarity and used for wind tunnel tests; the air-drop model and the traction parachute model are designed and processed according to the same geometric proportion as the airplane model.
Preferably, the test method provides an original test criterion, namely the pressure coefficient in the cabin
Preferably, the recovery nets are arranged below and behind the airplane model; the fixing column is a conductor, and a conducting wire is arranged on the outer side of the fixing column; and the lead is connected with the fixed column through a constantan wire.
Preferably, the test method includes the following test criteria: geometric similarity, froude number Fr, dynamic similarity (including large-size air-drop weight and drag parachute tension), and cabin pressure coefficient.
Preferably, the method for calculating parameters and designing models of the aerial delivery object model and the traction parachute model.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention provides a wind tunnel test method for researching pressure change characteristics in an airdrop cabin of a large object of a transport airplane; determining a similar criterion for a pressure change test in an airdrop cabin of a large object of a transport aircraft, providing a formula for converting the pressure in the cabin and corresponding change time into the pressure change in the cabin and corresponding change time of airdrop under flight conditions during the test, providing a parameter calculation and model design method of an airdrop model and a traction parachute model, and establishing a specific method and a specific step of the pressure test in the airdrop cabin of the transport aircraft; the test method can be used for researching the pressure change of the airdrop cabin of the large object of the transport airplane, judging whether the pressure change causes damage to personnel in the cabin during airdrop implementation and providing a basis for the implementation of actual airdrop of the large object of a corresponding flight test;
2. the invention provides an in-cabin pressure coefficient definition suitable for the study on the pressure change in an airdrop cabin of a transport aircraft, which is a key similarity criterion for the pressure change test in the airdrop cabin of a large object of the transport aircraft and is a basis for converting pressure data in the cabin measured by the test into data under a flight condition;
3. the invention provides a formula for converting the pressure in the cabin and the corresponding change time into the pressure change in the cabin and the corresponding change time under the air drop condition during the test, and lays a theoretical foundation for developing the test;
4. the invention provides a method for designing an aerial delivery model and a traction parachute model and throwing and recovering the aerial delivery model;
5. according to the method, research aiming at the pressure change in the large-object airdrop cabin of the transport airplane can be developed, whether the pressure change hurts personnel in the cabin during airdrop implementation is judged, and a basis is provided for implementation of actual large-object airdrop of a corresponding flight test.
Drawings
FIG. 1 is a schematic structural diagram of a method for testing pressure variation characteristics in an airdrop cabin of a large-size object of a transport aircraft according to the present invention;
FIG. 2 is a schematic diagram of a slide rail structure in the test method for the pressure change characteristics in the airdrop cabin of a large-size object of a transport aircraft according to the present invention;
FIG. 3 is a schematic diagram illustrating the distribution of dynamic pressure sensors in the method for testing the pressure variation characteristics in the airdrop cabin of a large-sized object of a transport aircraft according to the present invention;
FIG. 4 is a schematic diagram A-A in the method for testing the pressure change characteristics in the air drop cabin of the large-size object of the transport aircraft.
In the figure: 1. an airplane model; 2. an aerial delivery model; 3. an umbrella rope model; 4. a traction umbrella model; 5. a slide rail; 6. a lead wire; 7. fixing a column; 8. a wire; 9. constantan wire; 10. a front hatch door; 11. a cargo bridge model; 12. a rear large cabin door; 13. an aerial delivery object model fixing column; 14. a traction umbrella model fixing column; 15. a dynamic pressure sensor.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-4, the present invention provides a technical solution: a test method for pressure change characteristics in an airdrop cabin of a large-size object of a transport airplane;
the required equipment and materials are: the system comprises a wind tunnel, an airplane model 1, an air-drop object model 2, a model wingtip supporting system, a recovery net, a high-speed camera, a constantan wire 9, a lead 6, a voltage-stabilized power supply, a dynamic pressure sensor 15, a sensor acquisition signal wire, a VXI data acquisition system and a computer system for processing data;
the pressure change characteristic test of the air drop cabin of the large-size object of the transport plane is carried out in a low-speed wind tunnel ternary test section; the airplane wind tunnel test model is supported in a ternary test section in a wingtip supporting mode, and the wingtip of the model is connected with a bracket of a wind tunnel wingtip supporting system through a flanged crank arm; the wing tip supporting system can realize the change of the attack angle and the sideslip angle within a certain range of the airplane model 1; laying a slide rail 5 on the lower wall in a cabin of an airplane model 1, mounting 4 pulleys or 2 pulleys and 2 sliding sheets at the bottom of an air-drop object model 2 similar to a large-size object, wherein the pulleys of the air-drop object model 2 are provided with inner check rings, placing the pulleys on the slide rail 5, and mounting the sliding sheets in a slide groove of a track to ensure that the air-drop object model 2 can freely slide on the slide rail 5; for the airdrop model 2 which is not thrown out at this time, the airdrop model 2 is connected to an airdrop model fixing column 13 on the lower wall near the front wall of the inner cabin of the airplane model 1 through a lead 6, and the model can be fixed to a position required in the front and back by adjusting the length of the lead 6; for an airdrop model 2 to be thrown in the test train number, a lead 6 is connected to 2 fixing columns 7 on the lower wall near the front wall of the inner cabin of the airplane model 1 through constantan wires 9, and the fixing columns 7 are conductors and are connected with a power supply through leads 8; the traction umbrella model 4 is connected to a traction umbrella model fixing column 14 on the back of the center line of the bottom of the aerial delivery model 2 through the proportionally shortened umbrella rope model 3;
recovery nets are arranged below and at the rear part of the airplane model 1; a high-speed camera is arranged in a wind tunnel on the same horizontal plane on the left side of the outlet of the big cabin door 12 at the back of the airplane model 1 and is used for shooting and calculating the cabin exit speed and the attitude of the air-dropped object model 2.
8 dynamic pressure sensors 15 are installed on the front wall and the right wall in the cabin of the airplane model 1 and are powered by a voltage-stabilized power supply, and a sensor acquisition signal line is communicated with a VXI data acquisition system.
Before the formal test of the pressure change of the large-size object air-drop front cabin, firstly, a standard air-drop object air-drop simulation test is carried out, the cabin outlet condition is recorded through a high-speed camera, the cabin outlet speed is calculated and compared with the value converted into the test state from the cabin outlet speed during actual flying air-drop, the umbrella surface state of the traction umbrella model 4 is adjusted, the condition that the tension coefficient is the same as the actual flying air-drop condition is met, and the traction umbrella is used for the subsequent test.
According to the large-size air-drop cabin internal pressure change characteristic test, under the condition that the shape of an air-drop object model 2 is similar to the shape of an airplane and the shape of an internal cabin, the influence of real Mach number Ma and Reynolds number Re can be ignored, firstly, the Froude number Fr of the model is ensured to be the same as the real object, meanwhile, the weight and aerodynamic force (moment) meet the power similarity criterion, and the change of the movement speed and the cabin internal pressure coefficient of the air-drop object model 2 in the model test can be ensured to be basically similar to the real object when the initial speed and the initial angular speed meet the corresponding relation; similar criteria to be met include;
(1) geometric similarity
The airplane model 1, the air-drop model 2, the traction parachute model 4 and the parachute rope model 3 all meet geometric similarity conditions; the requirements of the traction umbrella model 4 and the umbrella rope model 3 can be properly relaxed, the canopy thickness of the traction umbrella model 4 can not be simulated, and the umbrella rope model 3 can only consider enough strength.
(2) Froude number Fr
(3) Similar power, including large-size air-drop gravity and drag parachute tension
(4) Coefficient of pressure in cabin
In the present invention, the model and the real Froude number Fr are equal in formula (1), and gm＝gfThe velocity of the wind tunnel at the time of the test can be obtained as
According to the formula (2) of the power similarity condition, the air-drop object model bears the gravity GmGravity G borne by the material objectfThe ratio of which is equal to the ratio of the corresponding aerodynamic forces, and the coefficient of aerodynamic force cRm＝cRfAre equal to each other
Gm＝kρkl 3Gf(5)
According to the formula (2) of the power similarity condition, the traction force of the traction parachute model can be obtained to meet the requirement
Fm＝kρkl 3Ff(6)
Formulas (5) and (6) are used for calculating the weight of the aerial delivery model and the pulling force of the traction parachute model, and the aerial delivery model and the traction parachute model can be designed by combining the requirements of geometric similarity and used for wind tunnel tests;
according to the design of the aircraft model, kl＝1/15，
gm＝gf(ii) a The test wind tunnel is positioned at the altitude h of 550m and the rho of 1.16165kg/m3The simulated flying height h is 1000m and rho is 1.1117kg/m in the wind tunnel3Air density ratio k in flight airdrop state testρ＝ρm/ρfThe simulated flying height h is 11000m and rho is 0.36481kg/m at 1.044933Air density ratio k in flight airdrop state testρ＝ρm/ρf3.18426; the simulation was carried out with h 1000m and p 1.1117kg/m3In the condition test, G can be calculated according to the formula (5) and the formula (6) respectivelym＝3.0961×10-4GfAnd Fm＝3.0961×10-4Ff(ii) a The simulation was carried out for h 11000m and for p 0.36481kg/m3In the condition test, G can be calculated according to the formula (5) and the formula (6) respectivelym＝9.4348×10-4GfAnd Fm＝9.4348×10-4Ff；
Designing and processing an airdrop model 2 and a traction parachute model 4 according to the same geometric proportion of 1:15 as the airplane model 1 and the calculation result;
according to the fact that the cabin pressure coefficient of the wind tunnel test is equal to the cabin pressure coefficient of the flight airdrop, the following formula for converting the cabin pressure change characteristic in the wind tunnel test into the cabin pressure change in the flight airdrop and a corresponding pressure time change rate formula can be obtained by using the formula (3);
the working principle is as follows: during the test, the airplane model 1 is adjusted to a corresponding attitude, such as an attack angle, a yaw angle, a roll angle and various control surface angles, which are the same as those of an actual airplane, the air-drop object model 2 is placed on a slide rail 5, the air-drop object model 2 is fixed to a front and back proper position through a lead 6, and the lead 6 of the air-drop object model 2 is fixed to 2 fixing columns 7 on the lower wall near the front wall of the inner cabin of the airplane model 1 through constantan wires 9 in the test; the parachute line model 3 is used for connecting the traction parachute model 4 to a traction parachute model fixing column 14 of the central line at the rear part of the bottom of the aerial delivery object model 2; the wind tunnel is driven, and the parachute model 4 is pulled to tighten the airdrop model 2 and is positioned at a front proper position and a rear proper position; when the required wind speed is reached, the constantan wire 9 is electrified and fused to release the aerial delivery object model 2, meanwhile, the VXI acquisition system starts to acquire, the high-speed camera is started to shoot and record, the cabin exit speed and the posture of the aerial delivery object model 2 can be obtained through interpretation of the shooting result of the high-speed camera, and the pressure change of the aerial delivery object model 2 in the cabin moving and throwing process can be analyzed through the acquisition result of the VXI acquisition system.
Labeling: v represents the wind speed of the model test or the movement speed of the aircraft, m/s; g represents the acceleration of gravity, m/s2(ii) a l represents the characteristic length of the model or aircraft, m; f represents the pulling force of the aerial delivery object traction parachute or the traction parachute model, N; ρ represents the fluid density, kg/m3(ii) a S represents the characteristic area, m, of the model or aircraft2；cRRepresenting a model or an aircraft aerodynamic coefficient;
representing the coefficient of the air pulsation pressure in the cabin;
represents the value of the air pulsation pressure (absolute pressure), Pa; p is a radical ofaRepresenting model or aircraft static airflow pressure, Pa; the subscript m represents parameters corresponding to the wind tunnel test; the subscript f represents the parameters corresponding to the air drop for flight conditions; the subscript i represents the time series of the pulsating pressure in the cabin;
dynamic pressure for indicating air pulsation pressure in cabinThe measured value of the sensor, the absolute pressure, Pa; p is a radical ofhRepresents the atmospheric pressure at the flying height, Pa;
to represent
Time rate of change of (d), Pa/s; t represents the time, s, representing the change in model test or flight airdrop; k represents the proportion of the model test to the flight airdrop physical quantity; it is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A test method for pressure change characteristics in an airdrop cabin of a large-size object of a transport airplane comprises an airplane model (1) and an airdrop object model (2), and is characterized in that: the airplane model (1) is fixed in a wind tunnel in a certain supporting mode, a sliding rail (5) is laid on the lower wall of the inner cabin of the airplane model (1), an air-drop object model fixing column (13) is arranged on the lower wall near the inner cabin front wall of the airplane model (1), a plurality of fixing columns (7) are arranged on the lower wall near the inner cabin front wall of the airplane model (1), a lead (6) is connected to the front of the air-drop object model (2), the air-drop object model (2) is connected and fixed with a constantan wire (9) between the lead (6) and the fixing columns (7), a rear big cabin door (12) is arranged at the rear of the airplane model (1), a cargo bridge model (11) is arranged on the airplane model (1) at the lower end of the rear big cabin door (12), a traction umbrella rope model fixing column (14) is arranged at the lower end of the rear of the air-drop object model (2), and an, a traction umbrella model (4) is fixedly connected to the rear of the umbrella rope model (3), and recovery nets are arranged below and at the rear of the airplane model (1); the aircraft model is characterized in that a high-speed camera is mounted in a wind tunnel on the same horizontal plane on the left side of an outlet of a big cabin door (12) behind an aircraft model (1) and used for shooting and calculating the cabin-out speed and posture of an air-dropped object model (2), a plurality of dynamic pressure sensors (15) are mounted on the front wall and the right wall in the cabin of the aircraft model (1) and powered by a voltage-stabilized power supply, a signal acquisition line of each sensor is communicated with a data acquisition system, and the pressure change in the cabin of the aircraft model (1) in the process of moving and throwing out the air-dropped object model (2) in the cabin can be analyzed through the acquisition result of.
2. The method for testing the pressure change characteristic in the airdrop cabin of the large-size object of the transport airplane as claimed in claim 1, wherein: under the condition that the shape of the air-drop object model (2) is similar to the shape of the airplane and the shape of the inner cabin, the influence of the Mach number Ma and the Reynolds number Re of the test can be ignored, firstly, the Froude number Fr of the model is ensured to be the same as the real object, meanwhile, the weight and the aerodynamic force (moment) are ensured to meet the power similarity criterion, and the change of the movement speed and the pressure coefficient in the cabin of the space-time object-drop model (2) in the model test can be ensured to be basically similar to the real object when the initial speed and the initial angular speed meet the corresponding.
3. The method for testing the pressure change characteristic in the airdrop cabin of the large-size object of the transport airplane as claimed in claim 2, wherein: parameter calculation and model design methods of an aerial delivery object model and a traction parachute model are provided.
4. The method for testing the pressure variation characteristic in the airdrop cabin of a large-size object of a transport aircraft according to any one of claims 1, 2 and 3, wherein: the test method provides an original test criterion, namely the cabin pressure coefficient, the criterion is equal under the conditions of test and flight airdrop,
wherein:
representing the coefficient of the air pulsation pressure in the cabin;
representing the value of the air pulsation pressure (absolute pressure) in the test or flight condition cabin; p is a radical ofaRepresenting a model or aircraft air flow static pressure; the subscript m represents parameters corresponding to the wind tunnel test; the subscript f represents the parameters corresponding to the air drop for flight conditions; the index i indicates the time series of the pulsating pressure in the cabin.
5. The method for testing the pressure change characteristic in the airdrop cabin of the large-size object of the transport airplane as claimed in claim 1, wherein: recovery nets are arranged below and at the rear part of the airplane model (1); the fixing column (7) is a conductor, and a lead (8) is arranged on the outer side of the fixing column (7); the lead (6) is connected with the fixed column (7) through a constantan wire (9).
6. The method for testing the pressure change characteristic in the airdrop cabin of the large-size object of the transport airplane as claimed in claim 2, wherein: the test method needs to meet equal test criteria and comprises the following steps:
(1) geometric similarity
The airplane model (1), the airdrop model (2), the traction umbrella model (4) and the umbrella rope model (3) all meet geometric similarity conditions; the requirements of the traction umbrella model (4) and the umbrella rope model (3) can be properly relaxed, the canopy thickness of the traction umbrella model (4) can not be simulated, and the umbrella rope model (3) only needs to consider enough strength;
(2) froude number Fr
(3) Similar power, including large-size air-drop gravity and drag parachute tension
(4) Coefficient of pressure in cabin
Wherein: v represents the wind speed of the model test or the movement speed of the aircraft; g represents the gravitational acceleration; l represents a characteristic length of the model or aircraft; f represents the pulling force of the aerial delivery article traction parachute or the traction parachute model; ρ represents the fluid density; s represents the characteristic area of the model or the aircraft; c. CRRepresenting a model or an aircraft aerodynamic coefficient;
representing the coefficient of the air pulsation pressure in the cabin;
representing the value of the air pulsation pressure (absolute pressure) in the test or flight condition cabin; p is a radical ofaRepresenting a model or aircraft air flow static pressure; the subscript m represents parameters corresponding to the wind tunnel test; the subscript f represents the parameters corresponding to the air drop for flight conditions; the index i indicates the time series of the pulsating pressure in the cabin.
7. The method for testing the pressure variation characteristic in the airdrop cabin of the large-size object of the transport airplane as claimed in claim 6, wherein: parameter calculation and model design methods of an air-drop object model and a traction parachute model are provided; the parameter calculation and model design method of the airdrop model and the traction parachute model comprises the following steps:
according to equation (1) where the model and the physical Froude number Fr are equal, and gm＝gfThe velocity of the wind tunnel at the time of the test can be obtained as
According to the formula (2) of the power similarity condition, the air-drop object model bears the gravity GmGravity G borne by the material objectfThe ratio of which is equal to the ratio of the corresponding aerodynamic forces, and the coefficient of aerodynamic force cRm＝cRfAre equal to each other
Gm＝kρkl 3Gf(5)
According to the formula (2) of the power similarity condition, the traction force of the traction parachute model can be obtained to meet the requirement
Fm＝kρkl 3Ff(6)
Wherein k islRepresenting the proportion of model test and flight airdrop physical quantity; k is a radical ofρRepresents the air density ratio; formulas (5) and (6) are used for calculating the weight of the aerial delivery model and the pulling force of the traction parachute model, and the aerial delivery model and the traction parachute model can be designed by combining the requirements of geometric similarity and used for wind tunnel tests; the airdrop model (2) and the traction umbrella model (4) are designed and processed according to the same geometric proportion as the airplane model (1).
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| CN110702366B (en) * | 2019-11-01 | 2021-01-08 | 中国空气动力研究与发展中心超高速空气动力研究所 | Embedded optical pressure measurement method for shielding position of hypersonic wind tunnel model |
| CN110889171B (en) * | 2019-12-02 | 2023-08-18 | 中国空气动力研究与发展中心 | Design method of tail rotor test model of vertical wind tunnel aircraft |
| CN111137454B (en) * | 2019-12-31 | 2021-08-20 | 航天时代飞鸿技术有限公司 | Automatic air-drop system of unmanned conveyer |
| CN111785115A (en) * | 2020-07-01 | 2020-10-16 | 中国人民解放军95944部队 | Simple simulation aircraft platform for airdrop training |
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| JPH102831A (en) * | 1996-06-18 | 1998-01-06 | Mitsubishi Heavy Ind Ltd | Airdrop object testing wind tunnel |
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| CN202041365U (en) * | 2011-05-05 | 2011-11-16 | 西北工业大学 | Support frame for wind tunnel test model |
| CN109100111B (en) * | 2018-07-06 | 2020-05-12 | 江西洪都航空工业集团有限责任公司 | Device is put in test of freely flying of perpendicular wind tunnel model |
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