Performance evaluation test method for resistance-to-ground parachute

Abstract

A ground-effect drag parachute performance evaluation test method comprises the steps that load measurement three-component data is obtained, and the drag coefficient and the comprehensive swing angle of a drag parachute are obtained by combining atmospheric density and wind speed calculation; calculating a resistance coefficient and a comprehensive swing angle mean value; carrying out statistics on comprehensive swing angle frequency distribution; calculating a horizontal swing angle and a vertical swing angle; calculating a vertical direction swing angle mean value / a horizontal swing angle mean value; the rotation performance of the drag parachute is obtained through images. The method can be used for evaluating the ground effect influence of the near-ground horizontal drag parachute, and can quantitatively evaluate the influence of the ground effect on the resistance performance and the swing angle of the drag parachute.

Description

TECHNICAL FIELD

[0001] The application can be used for evaluating the influence of ground effect on the horizontal working resistance parachute system performance, and can also be used for evaluating other parachute performances. It relates to the technical field of aerodynamic test. BACKGROUND

[0002] The resistance parachute is a flexible deployable aerodynamic deceleration device, which has light weight, small packing volume, simple and convenient opening and throwing operation. After the aircraft lands, the resistance parachute can be quickly unfolded and generate a large resistance surface, which can generate a large deceleration force, shorten the landing sliding distance and improve the service life of the brake device. Since the resistance of the resistance parachute increases rapidly with the increase of the sliding speed, the deceleration effect of the resistance parachute under the condition of medium and high speed is more significant. Another advantage of the resistance parachute is that its deceleration effect is independent of the runway condition, and it can work under the condition of wet and icy runway, and can also be used in special situations such as aborting take-off, brake device failure, no flap, and overspeed landing. The resistance parachute can be used repeatedly, has good economy, convenient maintenance and installation, and low cost, and is widely used in horizontal landing deceleration.

[0003] Unlike the working environment of the air parachute, the influence of the ground effect on the horizontal near-ground working resistance parachute needs to be evaluated. The influence of the ground effect on the resistance parachute has not yet been maturely theorized, and the simulation calculation results also need to be verified by ground tests. The existing ground effect evaluation method cannot realize multi-parameter coupling measurement.

[0004] For the test means of parachute performance evaluation, wind tunnel test, air-drop test and rocket sled test are usually used. The air-drop test is expensive and has a long test cycle, and is not suitable for evaluating the performance of the ground effect resistance parachute. Compared with the air-drop test, the wind tunnel test is the most commonly used test means for evaluating the resistance performance and stability of the parachute. The wind tunnel test is affected by the cross-sectional size and blockage ratio of the wind tunnel, and the test product needs to be scaled down. In some tasks, the full-size parachute cannot be tested, and the wind tunnel test is in a closed environment and has blockage effect, so it cannot be used to evaluate the influence of the ground effect on the resistance parachute. The traditional wind tunnel test cannot truly simulate the ground effect. The speed control accuracy of the rocket sled test is insufficient, and the test cost is high, so it cannot be carried out in low-cost projects. SUMMARY

[0005] The technical problem solved by the application is that the application proposes a low-cost test method for evaluating the influence of the ground effect on the resistance parachute, proposes a parachute test scheme based on an electromagnetic sled test platform and a test data processing method, and can obtain the resistance characteristics and stability of the resistance parachute under the influence of the ground effect.

[0006] The technical solution of the application is:

[0007] A ground effect drag performance evaluation test method, comprising:

[0008] 1) install the test drag parachute on the electromagnetic pry test platform through the test tool;

[0009] 2) control the electromagnetic pry test platform to drive the test drag parachute to move at a set speed v;

[0010] 3) obtain multiple steady-state segment sampling point data of the load measurement three-component data (F x , F y , F z ) at the test drag parachute suspension point;

[0011] 4) according to the load measurement three-component data (F x , F y , F z ) obtained in step 3), obtain the drag parachute drag coefficient C D and the comprehensive swing angle θ corresponding to each sampling point;

[0012] 5) repeat step 4) to obtain the drag parachute drag coefficient C D and the comprehensive swing angle θ of each sampling point;

[0013] 6) for test drag parachutes of different types, repeat steps 1)-5) to obtain the drag parachute drag coefficient C D and the comprehensive swing angle θ of the test drag parachutes of different types, and then take the average to obtain the average drag coefficient C Dmean and the average swing angle θ mean in the stable stage;

[0014] 6) according to the drag parachute drag coefficient C D and the comprehensive swing angle θ, statistically obtain the swing angle frequency distribution corresponding to different types of parachutes, and draw a swing angle frequency distribution histogram;

[0015] 7) according to the load measurement three-component data (F x , F y , F z ) obtained in step 3), the horizontal swing angle α and the vertical swing angle β, and the horizontal swing angle average α mean , the vertical swing angle average β mean , and then obtain the longitudinal swing angle proportion;

[0016] 8) according to the obtained comprehensive swing angle average θ mean , the average drag coefficient C Dmean in the stable stage, the swing angle frequency distribution angle in the swing angle frequency distribution histogram, and the longitudinal swing angle proportion, complete the performance evaluation test.

[0017] Preferably, the speed v in step 2) is set to be equal to the working speed of the real drag parachute.

[0018] Preferably, the hanging height of the test drag parachute suspension point to the electromagnetic pry test platform in step 1) is H, and the determination method is as follows:

[0019]

[0020] Wherein, H0 is the distance from the suspension point to the ground when the real drag parachute works horizontally, S0 is the nominal area of the real drag parachute under working, and S is the nominal area of the test drag parachute.

[0021] Preferably, the drag coefficient C of the drag parachute in step 4) is determined by the method of comprehensive swing angle θ, and the specific method is as follows: D

[0022]

[0023] Wherein, F x , F y , F z are three-component load measurement data in the platform coordinate system; ρ is the atmospheric density, w is the wind speed and wind direction vector.

[0024] The z-axis of the platform coordinate system is along the central axis direction of the parachute, and the positive direction is consistent with the traction direction of the parachute; the y-axis is perpendicular to the z-axis and points to the sky as the positive direction, and the origin of the platform coordinate system is located at the suspension point of the test drag parachute.

[0025] Preferably, the determination method of the horizontal swing angle α in step 7) is as follows:

[0026]

[0027] Preferably, the determination method of the vertical swing angle β in step 7) is as follows:

[0028]

[0029] Preferably, the longitudinal swing angle ratio in step 7) is as follows:

[0030] Compared with the prior art, the advantages of the present application mainly lie in the following aspects:

[0031] The present application can realize continuous and accurate adjustment of the whole speed, and has the advantages of short preparation time, low test cost, high test speed control precision, small vibration overload interference, short preparation time and the like compared with the rocket pry test.

[0032] ​Compared with the traditional wind tunnel test, the electromagnetic test is not affected by the blockage ratio, is an open fluid domain test, is not limited by the space of the site, can realize the implementation of a large-size test piece, and can realize the dynamic ground effect simulation under the real motion state. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A schematic diagram of the test scheme platform of the application is shown in the figure.

[0034] Figure 2 A flow chart of the method of the application is shown in the figure.

[0035] Figure 3 A schematic diagram of the folding of the canopy before the test is shown in the figure.

[0036] Fig. 4(a), Fig. 4(b) and Fig. 4(c) are distribution diagrams of the oscillation angular frequency of different umbrella types in an embodiment of the application. DETAILED DESCRIPTION

[0037] The test method for evaluating the influence of ground effect on the drag umbrella at low cost according to the application has the following specific implementation steps:

[0038] 1) Let the test stable running speed condition v be equal to the working speed of the real drag umbrella;

[0039] 2) According to the distance H0 of the suspension point of the real drag umbrella from the ground when the real drag umbrella works horizontally, the nominal area S0 of the real drag umbrella when working, and the nominal area S of the test drag umbrella, the distance between the suspension point of the test drag umbrella 4 and the test platform is determined, as shown in the figure. Figure 1

[0040]

[0041] According to the working speed of the real drag umbrella, the working load F of the drag umbrella is estimated; the working load F of the drag umbrella is used for subsequent tool strength design.

[0042]

[0043] Wherein, C D ′ is the estimated value of the drag coefficient of the real drag umbrella, which is a known quantity estimated by engineering.

[0044] 3) Design a dynamic coupling test protocol, including a multi-stage test procedure of an acceleration section, a steady state section and a deceleration section. According to the anti-overload capacity of the tested object, the acceleration a required for the acceleration of the electromagnetic test platform 5 is determined, and the acceleration does not exceed 30g. According to the distance L that the electromagnetic test platform 5 can run, the maximum test stable measurement time t max is calculated, t should be less than t max , and at the same time, in order to obtain stable measurement data for later data processing and analysis, t should be not less than 3s;

[0045] ​

[0046] 4) Tooling design: The design of the tooling needs to consider four aspects: the strength meets the load requirements of the drag parachute, the design load is F (i.e. the working load F of the drag parachute obtained in step 2) and should have a certain safety margin; meets the interface installation with the drag parachute or load sensor, meets the interface requirements with the electromagnetic pry test platform 5; the top of the tooling reserves the interface position for the installation of the motion camera; has the height adjustment function.

[0047] 5) Clear measurement scheme: A multi-parameter coupled measurement system is designed to determine the load measurement and image measurement scheme. If the stability of the drag parachute needs to be considered, a three-component load measurement device is required for load measurement, and the image measurement installation position should be located at the top center axis of the tooling. The environmental measurement requirements are clear, including atmospheric density p, wind speed and wind direction w.

[0048] 6) Test preparation: Install the load measurement device and image measurement device; install the test drag parachute on the electromagnetic pry test platform 5; fully protect the electromagnetic pry test platform 5, and the electromagnetic pry test platform 5 cannot have protrusions and any gaps that may hook the drag parachute; set the key test parameters such as speed, acceleration, and running time.

[0049] 7) The test tooling 1 is fixedly installed on one side of the electromagnetic pry test platform 5 in the running direction, and is installed in the middle of the track. The test tooling 1 is connected with the test drag parachute 4 through a three-component tension sensor 3, and a motion camera 2 is installed at the top of the test tooling 1. The position and angle of the motion camera 2 are adjusted so that the test drag parachute 4 can be completely captured in the working state. During the test, the test platform moves at the set speed and drives the test drag parachute 4 to move. The distance between the test platform position and the test drag parachute 4 suspension point position is H. By adjusting the value of H, the influence of ground effect on the drag performance can be studied. The test implementation process of the present application is shown in Figure 2 Before the test platform runs, the test drag parachute 4 should be folded and placed as shown in Figure 3 The test process includes two key steps: the platform needs to be surface protected before the test is implemented, so that the platform has no protrusions; the canopy needs to be folded and placed on the test platform.

[0050] 8) Take H as the suspension height of the drag parachute, and carry out the test according to the set key test parameters such as speed, acceleration, and running time to obtain the three-component load measurement data (F x , F y , F z); each time before the test is implemented, the test resistance umbrella 4 needs to be folded and arranged; assuming that the number of umbrella cloth pieces (the number of umbrella ropes) of the test resistance umbrella 4 is N, the first piece to the N / 2th piece of the umbrella cloth pieces are sequentially folded and arranged, the N / 2+1th piece to the Nth piece of the umbrella cloth pieces are sequentially folded and arranged, and the combing of the umbrella ropes is without twisting and crossing.

[0051] 9) Test data processing: according to the load measurement three-component data F x , F y , F z , the atmospheric density and the wind speed are combined to obtain the resistance umbrella resistance coefficient C D and the comprehensive swing angle θ corresponding to each sampling point.

[0052]

[0053]

[0054] wherein F x , F y , F z are the load measurement three-component data in the platform coordinate system; the z-axis of the platform coordinate system is along the central axis direction of the parachute, and the positive direction is consistent with the traction direction of the parachute; the y-axis is perpendicular to the z-axis, and the positive direction is upward; the origin of the platform coordinate system is located at the suspension point of the test resistance umbrella 4.

[0055] 10) Steps 2) to 9) are repeated for different umbrella types, and the C D and θ corresponding to different umbrella types are obtained, and the stable stage resistance coefficient mean C Dmean and the comprehensive swing angle mean θ mean corresponding to different umbrella types are calculated.

[0056] 11) The swing angle frequency distribution corresponding to different umbrella types is obtained according to the resistance umbrella resistance coefficient C D and the comprehensive swing angle θ, and the frequency distribution histogram is drawn, as shown in FIGS. 4(a), 4(b) and 4(c) in an embodiment of the present application.

[0057] 12) The horizontal swing angle α and the vertical swing angle β and the horizontal swing angle mean α mean and the vertical swing angle mean β mean are calculated, and the longitudinal swing angle proportion is obtained.

[0058] Horizontal swing angle:

[0059] Vertical swing angle:

[0060] Longitudinal swing angle proportion:

[0061] 13) Get the resistance parachute rotation performance rmp by image acquisition.

[0062] 14) The above data can be obtained by synthesizing the influence of ground effect on resistance parachute performance and the performance difference of different configurations of resistance parachute under the influence of ground effect.

[0063] For the same height and speed conditions, the smaller the average swing angle θ mean The smaller the average swing angle θ Dmean The smaller the average swing angle θ The smaller the average swing angle θ

[0064] The electromagnetic pry test site is open, which is consistent with the real use scene of the horizontal aircraft resistance parachute, and is the best test platform for ground effect research of the resistance parachute. The present application proposes a low-cost method for evaluating the ground effect resistance performance, which can be used to solve the problem of ground effect influence evaluation of the near-ground horizontal resistance parachute, and can quantitatively evaluate the influence of ground effect on the resistance performance and swing angle of the resistance parachute.

[0065] Although the present application has been disclosed as above with reference to the preferred embodiments, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications to the technical solutions of the present application by using the disclosed methods and technical contents without departing from the spirit and scope of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not deviate from the technical solutions of the present application, belongs to the protection scope of the present application. In the case of no conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0066] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A test method for evaluating the performance of a ground effect parachute, characterized in that: include: 1) Installing the test drag parachute (4) on the electromagnetic pry test platform (5) through the test fixture (1); 2) controlling the electromagnetic pry test platform (5) to drive the test drag parachute (4) to move at a set speed v; 3) Obtain the three-component load measurement data (F x 、F y 、F z ) of multiple steady-state sampling point data; 4) According to the load measurement three-component data (F x 、F y 、F z ), obtain the drag coefficient C of the drag parachute corresponding to each sampling point D and the integrated swing angle θ; 5) Repeat step 4) to traverse the data of each sampling point and obtain the drag coefficient C of each sampling point D and the integrated swing angle θ; 6) Repeat steps 1) to 5) for the test drag parachutes (4) of different parachute types to obtain the drag coefficients C of the test drag parachutes (4) of different parachute types. D and the comprehensive swing angle θ, and then take the average value to obtain the mean resistance coefficient C in the stable stage Dmean and the comprehensive swing angle mean θ mean ; 6) According to the drag coefficient C of the drag parachute D The frequency distribution of the swing angles corresponding to different umbrella types is obtained by summarizing the swing angle θ, and the swing angle frequency distribution histogram is plotted; 7) According to the load measurement three-component data (F x 、F y 、F z ), horizontal swing angle α and vertical swing angle β and their horizontal swing angle mean α mean , vertical swing angle mean β mean , and then the longitudinal swing angle ratio is obtained; 8) According to the obtained comprehensive swing angle mean θ mean , the average resistance coefficient C in the stable stage Dmean , the swing angle frequency distribution angle in the swing angle frequency distribution histogram, and the proportion of longitudinal swing angle to complete the performance evaluation test.

2. A ground effect parachute performance evaluation test method according to claim 1, characterized in that: In step 2), the speed v is set equal to the working speed of the real drag parachute.

3. A ground effect parachute performance evaluation test method according to claim 2, characterized in that: In step 1), the hanging height from the hanging point of the test drag parachute (4) to the electromagnetic pry test platform (5) is H, which is determined by: Among them, H0 is the distance between the hanging point and the ground when the real drag parachute is working horizontally, S0 is the nominal area of ​​the real drag parachute when working, and S is the nominal area of ​​the test drag parachute.

4. A ground effect parachute performance evaluation test method according to claim 3, characterized in that: Step 4) Parachute drag coefficient C D And the method of comprehensive swing angle θ is as follows: Among them, F x 、F y 、F z is the three-component load measurement data in the platform coordinate system; ρ is the atmospheric density, w is the wind speed and direction vector; The z-axis of the platform coordinate system is along the central axis of the parachute, and its positive direction is consistent with the direction in which the parachute is pulled; the y-axis is perpendicular to the z-axis, and its positive direction is pointing to the sky. The origin of the platform coordinate system is located at the hanging point of the test drag parachute (4).

5. A ground effect parachute performance evaluation test method according to any one of claims 1 to 4, characterized in that: The method for determining the horizontal swing angle α in step 7) is specifically as follows:

6. A ground effect parachute performance evaluation test method according to claim 5, characterized in that: The method for determining the vertical swing angle β in step 7) is specifically as follows:

7. A ground effect parachute performance evaluation test method according to claim 6, characterized in that: The longitudinal swing angle ratio in step 7) is:

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