JP3772212B2 - Transonic flutter stop device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wind tunnel experiment technique used for research and development of an aircraft, and more particularly to a flutter stop device.
[0002]
[Prior art]
When performing aeroelastic tests in the transonic region, it is well known that the wind tunnel test model installed in the wind tunnel produces flutter due to micro disturbances caused by the air flow. There is a risk of splashing inside. Therefore, in order to perform high-speed flutter wind tunnel tests in the transonic region safely and reliably, with high accuracy and high efficiency without breaking the model, the above-mentioned automatic flutter stop does not occur. A device is required as an incidental facility for a wind tunnel. In a large wind tunnel facility with good airflow characteristics, it is particularly important to avoid such a destructive phenomenon when testing using a large and expensive model. Such a flutter stop device must be able to be installed without changing the basic structure and performance of the wind tunnel body. When flutter occurs in the wing, the Mach number and dynamic pressure are automatically set to the limit values. Must be lowered to:
A transonic wind tunnel measuring cart that performs aeroelasticity tests is generally made of a perforated plate with four walls on the top, bottom, left, and right. It was. Since then, a measuring cart with good airflow characteristics has been developed, which has a structure in which the upper and lower sides are made of a multi-groove wall and the left and right are fixed walls, and air is extracted from the groove of the multi-groove wall. In a recent transonic wind tunnel facility having a bleed chamber, several types of wind tunnel measuring units that are generally selected and used according to the purpose of the wind tunnel test are prepared in the wind tunnel.
[0003]
In order to perform a high-speed flutter wind tunnel test in the transonic region safely and reliably with high accuracy and high efficiency without destroying the model, an automated flutter stop device is required as ancillary equipment for the wind tunnel. Such a flutter stop device is preferably installed without changing the basic structure and performance of the wind tunnel body, and immediately when flutter occurs on the wing, the Mach number and dynamic pressure are automatically lowered below the limit values. Must. Under such circumstances, the present applicant previously filed an application for Japanese Patent No. 2099140 (Japanese Patent Publication No. 8-23517: Patent Document 1) “Transonic Flutter Stop Device in Wind Tunnel Test”. As shown in FIG. 7, this flutter stop device has a flutter stop member 2 having an air flow shielding effect in a wind tunnel having a bleed chamber 8 for a flutter test in a transonic region. The flutter stop member 2 is inserted into the measurement unit 1 by a flutter generation signal from a flutter detection device at a position not hitting 3. The flutter stop member 2 stored at an arbitrary position on the measurement unit wall surface of the transonic wind tunnel having the bleed chamber immediately activates the actuator 6 in response to the signal of the sensor 5 attached to the wing model 3 and automatically flutters. The stop member 2 is inserted into the measurement unit 1. Depending on the ratio of the cross-sectional area of the flutter stop member 2 inserted into the measuring section 1 and the cross-sectional area of the measuring section of the wind tunnel, the Mach number and the dynamic pressure are caused by the energy loss of the wind tunnel due to the resistance and the extraction action circulating in the extraction chamber 8. It instantaneously drops below the flutter limit. As a result, the flutter of the wing can be stopped safely and reliably.
[0004]
In a transonic wind tunnel with a bleed chamber, a Mach number and dynamic pressure are instantaneously reduced below the flutter limit value by providing a resistance member against the airflow in the measurement section, and the flutter of the test model is safely suppressed. However, since the structure has an opening and a perforated plate between the side wall of the wind tunnel and the flutter stop member, the air flow enters and exits from this part, and the air flow drifts and fluctuates. It was. This drift and fluctuation of the air current affect the air current, and the test model is irregularly excited by flowing at an angle of attack different from the original angle of attack for the test model. For this reason, this irregular excitation caused a decrease in test accuracy, and was regarded as a problem. This phenomenon is not a big problem in the case of a 4-wall perforated wind tunnel wall, because the porous flutter stop member originally bleeds from the wall surface. If there is a gap between the opening and the wall surface of the porous flutter stop member and the tip member, the above-mentioned problems occur due to the occurrence of drift or bleed on the fixed wall that should be flat unlike the original design. It was pointed out.
[0005]
[Patent Document 1]
Japanese Examined Patent Publication No. 8-23517 [0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a flutter stop device that does not cause drift and fluctuation of airflow in a wind tunnel system having a flutter stop function that automatically reduces the Mach number and dynamic pressure to below a limit value as soon as flutter occurs. By providing, it is to prevent the test model from being irregularly excited and to prevent a decrease in test accuracy.
[0007]
[Means for Solving the Problems]
A perforated plate-like flutter stop plate is placed at the downstream side of the model to be tested, and is installed in such a way that it can be slid from both walls of the measurement chamber. In the state where the flutter stop plates are stored on both walls of the measurement chamber, the end surface is aligned with the wind tunnel wall surface and has no unevenness. In addition, when the model under test is a half-cut model, a flutter stop plate on one side is used, and when it is an all-machine model, a flutter stop plate on both sides is used, and the amount of slide protrusion from each wall of the measurement chamber It has a function that can be changed according to the model.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
From recent tests, the decrease in Mach number and dynamic pressure on the upstream side of the flutter stop member is as designed, but in the downstream region, if the flutter stop member is a porous flutter stop plate, the decrease amount depends on the position. It has been found that, in the case of a plate without a hole, the airflow fluctuates and concomitantly decreases at the downstream position of the flutter stop plate. FIG. 6 shows the experimental results showing the relationship between the Mach number distribution in the transonic wind tunnel measurement chamber having the bleed chamber and the Mach number decrease. In this graph, the vertical axis indicates the Mach number, the horizontal axis indicates the airflow direction measurement chamber position, and the zero point is the installation position of the flutter stop member. In the wind tunnel where the air flow of Mach 0.8 flows, ● indicates the Mach number in the transonic wind tunnel measurement chamber when a perforated plate-like (opening ratio 20%) flutter stop plate is projected at an angle of 45 ° to the air flow. A distribution ▲ indicates a Mach number distribution in a transonic wind tunnel measurement chamber when a flutter stop plate without holes (opening ratio 0%) is projected at an angle of 90 ° with respect to the air flow. From this graph, the design value [ΔM = M ² × 1.1√ (Fp / Fw) for the perforated plate-like flutter stop plate and the holeless flutter stop plate on the upstream side from the installation position of the flutter stop member. Where Fp is the effective sectional area of the stop plate and Fw is the sectional area of the wind tunnel. ] As shown in the figure, the Mach 0.8 airflow is stable in a state of decreasing to about 0.62 while the Mach number rises in the case of a perforated plate-like flutter stop plate on the downstream side. In the case of a flutter stop plate without holes, a further decrease phenomenon is observed.
[0009]
4 shows the Mach number decrease amount ΔM distribution when the porous flutter stop plate is arranged in the wind tunnel measurement chamber, and FIG. 5 shows the Mach number decrease amount ΔM distribution when the holeless flutter stop plate is arranged in the wind tunnel measurement chamber. Show the distribution. Fig. 4 shows a pencil-shaped H-II rocket fairing model as shown in the lower part of the figure, and a pentagonal porous flutter stop plate (opening ratio 20%) with a home base shape on the upstream side of the model. The upper graph shows the Mach number reduction amount ΔM when protruding from the horizontal wall at an angle of 45 ° with respect to the airflow. The three circles at the bottom in the figure are schlieren windows for observation provided on the side wall of the wind tunnel. In this graph, the vertical axis indicates the Mach number decrease amount ΔM, the horizontal axis indicates the position information of the measurement chamber in the airflow direction, and the positional relationship between the lower flutter stop plate and the model is associated. A large number of pressure sensors were arranged in an array on the lower wall of the wind tunnel measurement chamber, and the Mach number reduction amount ΔM was calculated from the pressure value detected by the sensor, and plotted in the upper graph. The data in the four states Mach 0.6, 0.7, 0.8, and 0.9 are shown when the flutter stop plate is retracted. As can be seen from this graph, in the case of the porous flutter stop plate, the Mach number decrease amount ΔM gradually decreases on the downstream side, and the Mach number is recovered.
[0010]
On the other hand, in FIG. 5, a cone model as shown in the lower stage is arranged, and a pentagonal holeless flutter stop plate (aperture ratio 0%) having a home base shape on the upstream side is flown from the side wall of the wind tunnel measurement chamber. The upper graph shows the amount of decrease in Mach number ΔM when projected at an angle of 90 ° to the angle. The lower three circles in the figure are schlieren windows for observation provided on the side wall of the wind tunnel. The vertical axis of the graph indicates the Mach number decrease amount ΔM, the horizontal axis indicates the position information of the measurement chamber in the airflow direction, Corresponding to the positional relationship between the flutter stop plate and the model, a number of pressure sensors are arranged in an array on the lower wall of the wind tunnel measurement chamber, and the pressure value detected by the sensor is converted to a Mach number to reduce the Mach number Δ The point where M is calculated and plotted in the upper graph is the same as in FIG. The data in the four states Mach 0.6, 0.7, 0.8, and 0.9 are shown when the flutter stop plate is retracted. As can be seen from this graph, in the case of the holeless flutter stop plate, the Mach number decrease amount ΔM increases on the downstream side, and there is no significant change thereafter.
In view of such a phenomenon, it has been found that placing the test model downstream of the flutter stop member is not preferable in terms of safety and efficiency. In the present invention, the test model is placed upstream of the flutter stop member. I came up with the idea.
[0011]
In the measuring part for all models, which is formed by the upper and lower multi-groove walls and the left and right fixed walls, and has excellent airflow characteristics, the bleed operation is performed only on the upper and lower multi-groove walls, the fixed walls are kept flat, and the airflow characteristics inherent to the wind tunnel are maintained. In order to maintain the flutter stop member, it is desirable that the flutter stop device has no opening when the flutter stop member is accommodated and the measurement unit wall surface is not uneven. It must also be an effective method for flutter testing of all models. Accordingly, the present invention provides a flutter stop device that does not have irregularities in the openings and wall surfaces in the measuring unit for all model models for upper and lower multi-groove walls and left and right fixed walls with good airflow characteristics of a transonic wind tunnel having a bleed chamber. It was developed for a model. FIG. 1 shows an outline of a wind tunnel measuring unit to which the present invention is applied. The whole machine model 11 is attached to the model support means 12 and is installed in a measuring section surrounded by the upper and lower multi-groove walls 1 ′ and the left and right fixed walls 1. The flutter stop device adopts a slide method in which the stop plate is stored in the wall when it is not operating, and protrudes into the measuring section when it is operated, so that the cross section of the perforated flutter stop plate is reduced to minimize the gap between the stop plate and the wall. The tip surface is formed of a member that becomes a wall surface in the retracted state. In this structure, the stop plate is housed in the wall when there is no operation, and there is no opening, so there is no bleed action on the fixed wall 1. Therefore, the bleed operation is performed only on the upper and lower multi-groove walls as originally designed. In addition, when the flutter stop plate is retracted, the wall member at the tip becomes a continuous surface with the wall surface, so there is no unevenness and there is no fluctuation of the air flow in that part, so that the air flow characteristics as designed are kept good. it can. The installation position of the flutter stop device is on the downstream side of the model 11.
[0012]
When flutter is detected, the actuator 8 is activated to cause the flutter stop plate to protrude into the measuring section. The amount of displacement is preferably set according to the test conditions including the type and shape of the model to be tested. Then, an appropriate value is obtained and the drive of the actuator 8 is adjusted. In addition, since the flutter stop device occupies a considerable place in the wind tunnel facility, it is preferable to adopt a configuration in which the whole can be detached from the wind tunnel facility in an experiment that is not used. In such a case, a mekra lid of the same quality as the fixed wall 1 is attached to the opening after the flutter stop device is removed to ensure continuous smoothness of the fixed wall. This flutter stop device is a pair of left and right fixed walls, and only one is used in the case of a half-cut model, and a pair of left and right flutter stop devices is used in the case of an all-machine model. For flutter testing of all aircraft models, a flutter stop member is inserted into the measurement unit from both directions with respect to both wings, and the flutter of the wings is safely suppressed by the airflow shielding effect. In the flutter test of the half-cut model, either the left or right flutter stop device may be used. When both flutter stop devices are used, the amount of the flutter stop member put out into the measuring section can be halved. In this case, since the operation time of the flutter stop member is reduced in inverse proportion, the safety is increased.
While the flutter stop device is not activated, it is the same as the original fixed wall so that it does not affect the airflow. There is a synergistic effect that overlaps with the installation on the side.
[0013]
[Example 1]
FIG. 2 shows an embodiment of the flutter stop device. (A) is a sectional side view of the flutter stop device, (b) is a plane sectional view, (c) is a sectional view taken along the line AA in FIG. (A), and (d) is a sectional view taken along the line BB in FIG. (B) and (b) show the configuration when the stop plate protrudes into the measuring section. Reference numeral 1 denotes a fixed wall of the measurement unit. The flutter stop device housed in the casing 10 is attached to the outside of the opening of the wind tunnel measurement unit fixed wall 1 by a fixing member 7, and the stop plate is stored in the fixed wall 1 when not operating. Take the form. The flutter stop plate that protrudes into the measurement chamber during operation includes a front end surface composed of a wall surface member 3 for maintaining continuity with the fixed wall 1 during storage, a rear end surface composed of a rigid plate-like body 6, It consists of two upper and lower strength members 4 connecting between the plate-like bodies 6 and two perforated plates 2 attached to both sides across the two upper and lower strength members 4 and is necessary for transonic airflow. It has a solid structure to give strength. The flutter stop plate takes a form accommodated in the casing 10 when it is not in operation, and when the flutter is detected, the actuator 8 is operated, and the protrusion shown in the figure is shown through the slide rod 9 fixed to the plate-like body 6. Takes form. As can be seen from the A-A cross-sectional view shown in C, this slide mechanism is fitted with four guide rods 5 extending in the sliding direction two at the upper and lower positions inside the casing 10 and the guide rods 5. As can be seen from the contact of the four through holes provided in the plate-like body 6 and the cross-sectional view taken along the line BB shown in D, the contact between the end of the upper and lower opening walls 10a of the casing 10 and the strength member 4 It is slidable and constitutes a solid and stable mechanism. When not in operation, the back surface of the wall member 3 and the upper and lower opening walls 10a of the casing 10 come into contact with each other, and the wall member 3 is fitted into the opening of the fixed wall 1 without a gap to form a smooth surface continuous with the fixed wall 1. To do. The amount of displacement by which the stop plate is slid by the actuator 8 can be adjusted, and is set to an amount acquired in advance according to the type of model, experimental conditions, and the like. When the controller receives an output signal from the flutter detection sensor installed in the model, the controller outputs an operation signal to the actuator 8. Further, the potentiometer shown in the figure displays the amount of the flutter stop plate that is taken in and out.
As shown in FIG. 3, the flutter stop device of the present embodiment is arranged in a measurement unit composed of upper and lower multi-groove walls and left and right fixed walls in a wind tunnel, for example, in a form installed on the left and right fixed walls downstream of the model, Subject to flutter testing.
[0014]
【The invention's effect】
The flutter stop device of the present invention, which is arranged on the downstream side wall surface of the model under test in the transonic wind tunnel measurement section, places the model in a stable Mach number lowering region on the upstream side, and stops the flutter stably and reliably. Can be made.
In addition, it is placed on the measuring unit fixed wall of the transonic wind tunnel with the bleed chamber, and the flutter stop plate is slidably provided so that it can protrude into the measuring unit, and there is no opening when it is stored in the wall when not in operation. Since the flutter stop device of the present invention adopting the form can prevent air from being extracted from the opening, it can ensure the same airflow characteristics as the original test section. Further, the flutter stop plate according to the present invention adopts a configuration in which the front end surface of the flutter stop plate is formed of a flat wall member having the same shape as the fixed wall opening, and the front end surface is aligned with the fixed wall surface when stored in the wall during non-operation. Since the stop device forms a smooth surface that is continuous with the fixed wall, the airflow characteristics similar to those of the original test section can be secured.
[0015]
A flutter stop plate comprising a front wall plate and a rear plate, two upper and lower strength members connecting the two, and two perforated plates attached to both sides across the two upper and lower strength members. The flutter stop device according to the present invention has a contact relationship between the plate member and the casing opening wall end fitted to the guide rod and the strength member, and the flutter stop plate projects at right angles into the measurement unit. In this case, the above structure can provide the necessary strength against the transonic airflow.
In addition, in the flutter stop device of the present invention consisting of a pair installed on the left and right fixed walls of the measuring unit, the type of the test model such as a half-cut model, a full-scale model, and the appropriate protrusion amount of the flutter stop plate corresponding to the test conditions are set. If it is obtained in advance, an appropriate flutter stop operation can be executed by appropriately using which one of the flutter stop plates protrudes in the flutter test.
When the flutter stop device of the present invention is installed in a removable form on the fixed wall of the measurement unit and is provided with a cover for closing the fixed wall opening, the flutter stop device takes up space when the flutter test is not performed. By attaching the mecha lid to the wall surface of the subsequent opening, not only can a sufficient space required for the experiment be taken, but also the air flow characteristics of the original measurement part will not be impaired.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a wind tunnel measuring unit to which the present invention is applied.
FIG. 2 is a diagram showing an embodiment of a flutter stop device of the present invention.
FIG. 3 is a diagram showing a form in which the flutter stop device of the present embodiment is installed in a measurement unit including upper and lower multi-groove walls and left and right fixed walls.
FIG. 4 is a view showing a Mach number decrease amount ΔM distribution when a porous flutter stop plate is arranged in a wind tunnel measurement chamber.
FIG. 5 is a diagram showing a Mach number reduction amount ΔM distribution when a holeless flutter stop plate is arranged in a wind tunnel measurement chamber;
FIG. 6 is a diagram showing a relationship between a Mach number distribution in a transonic wind tunnel measurement chamber having a bleed chamber and a decrease in Mach number.
FIG. 7 is a diagram illustrating a conventional transonic flutter stop device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Measurement part fixed wall 8 Actuator 2 Porous plate 9 Slide rod 3 Wall member 10 Casing 4 Strength member 10a Opening wall 5 Guide rod 11 Model 6 Plate-like body 12 Model support means 7 Fixing member

Claims (6)

  A flutter stop device, which is disposed on a downstream side wall surface of a test model in a measurement part of a transonic wind tunnel. Located on the measuring unit fixed wall of the transonic wind tunnel with the bleed chamber, the flutter stop plate is slidably provided so that it can protrude into the measuring unit, and there is no opening when stored in the wall when not in operation The flutter stop device according to claim 1 . The flutter stop plate is formed of a flat wall member whose tip surface is the same shape as the fixed wall opening, and when the flutter stop plate is stored in the wall during non-operation, the tip surface is aligned with the fixed wall surface to form a continuous smooth surface. The flutter stop device according to claim 2, wherein The flutter stop plate consists of a front wall plate and a rear plate, two upper and lower strength members connecting the two, and two perforated plates attached on both sides across the two upper and lower strength members. When the flutter stop plate protrudes at right angles into the measuring part due to the contact relationship between the plate member and the casing opening wall end fitted to the guide rod and the strength member, the necessary strength against the transonic airflow is given. The flutter stop device according to claim 2 or 3, wherein In the flutter stop device consisting of a pair installed on the right and left fixed walls of the measurement unit, the appropriate projection amount of the flutter stop plate corresponding to the type of test model such as half-cut model, all-machine model, test conditions, The method of using a flutter stop device according to any one of claims 2 to 4, wherein, in the flutter test, how many of the flutter stop plates protrude is properly used. The flutter stop plate is installed in a removable form on the fixed wall of the measurement unit, and has a mech lid that closes the fixed wall opening, and is removed when the flutter test is not performed. The flutter stop device according to any one of claims 2 to 4, wherein the flutter stop device can be attached.

Images