RU2384465C1 - Method for boundary layer control at aircraft surface and device for its implementation - Google Patents

Abstract

FIELD: air transport.

SUBSTANCE: method includes impulse action on boundary layer, registration of flow conditions, regulation of frequency and amplitude impact on boundary layer in real time. Action on boundary layer and registration of flow conditions is made by elements performed as nano- or microtubes at aircraft surface. Action on boundary layer is made in pulse-periodic thermal mode. The device contains elements located at aircraft surface that act on boundary layer and register flow conditions and parametre management system acting on boundary layer in real time. Action elements and registration of flow conditions are made as mass of nano- and microtubes oriented at the base surface under angle to flux within range of 0≤β≤180°, where β is an angle between main flow and tubes. Tubes are located at the base surface by pairs in rows at current lines. One of the tube in a pair is a generator with pulse periodic thermal impact, the other is a registering sensor of boundary layer parameters.

EFFECT: increase in range of frequency acting on flow.

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Description

The invention relates to aircraft and can be used to solve problems of controlling the boundary layer of aircraft.

Various methods are known for actively controlling the boundary flow, such as the mechanical effect of a streamlined surface on the boundary layer, as well as thermal, acoustic, and electromagnetic effects.

For example, in US patent No. 4516747 (publ. 05/14/1985) a method for actively controlling the flow using a system of a vibrating element - a sensitive element mounted on the surface of a streamlined body. Alternating vibrational and sensitive elements are connected to a control system that analyzes signals from the sensitive elements and corrects the signals for vibrational elements.

The disadvantages of this system include a limited frequency range, determined by the characteristics of both the vibration element and the sensor.

In US patent No. 5791275 (publ. 11.08.1998) a method for actively controlling the flow using arrays of control elements, each of which consists of a pair of electrodes and a pair of magnetic poles mounted on the surface of the aircraft in such a way that the generated electric and magnetic fields are directed perpendicular to each other. Each control element contains a turbulence sensor.

The disadvantages of this flow control scheme include the fact that such a system is designed to control the conductive fluid flow.

In the international patent WO 2006/040532 A1 (publ. 04/20/2006) a method for actively controlling the boundary flow using an electroactive polymer membrane having electrodes and located on a substrate is proposed.

The disadvantages of this invention include the lack of a sensor and a feedback system with an active control element, as well as the limitation of the frequency range of the impact on the stream.

In the patent of the Russian Federation No. 2243919 (published on June 20, 2004), a method is proposed for actively influencing the boundary flow by coating the entire surface of the aircraft with a piezoceramic layer and electrically acting on it. In some places on the surface of the apparatus, the piezoelectric coating is removed and sensors for parameters of turbulent gas motion are installed there.

The disadvantages of the proposed method include a limited frequency range of impact on the stream.

Closest to the claimed invention is a method of actively acting on the boundary layer near the surface of an aircraft, implemented by the device presented in RF patent No. 2002669 (publ. 15.11.1990). It proposes, after determining the position of the transition region of the boundary layer, to introduce a disturbance signal in the laminar region of the boundary layer, measure disturbances and flow characteristics at the beginning of the transition region, then adjust the amplitude of the disturbance signal, measure disturbances and flow characteristics from the beginning of the transition region to the trailing edge of the streamlined surface and according to these measurements, adjust the frequency of the disturbance signals. Perturbations are introduced into the boundary layer by pulses.

The disadvantages of this method include the limited frequency range of the impact on the stream.

The proposed inventions solve the problem of increasing the efficiency of boundary layer control and increasing the frequency range of the impact on the stream.

To obtain such a technical result in the proposed method for controlling the boundary layer on the surface of an aircraft, including pulsed action on the boundary layer, recording flow characteristics, adjusting the frequency and amplitude of the effect on the boundary layer in real time, acting on the boundary layer and recording the flow characteristics made in the form of highly sensitive nano- or micro-tubes located on the surface of the aircraft. In this case, the effect on the boundary layer is carried out in a pulse-periodic thermal regime.

Distinctive features of the proposed method are the impact on the boundary layer and registration of flow characteristics by means of highly sensitive nano- or micro-tubes located on the surface of the aircraft, and the impact on the boundary layer is carried out in a pulse-periodic thermal mode. This allows you to expand the frequency range of effects on the boundary layer and increase the efficiency of layer control.

To achieve the above technical result, a device is proposed that contains elements of the impact on the boundary layer and registration of flow characteristics located on the surface of the aircraft, as well as a control system for the parameters of the impact on the boundary layer in real time. In contrast to the known in the proposed device, the elements of influence and registration of the flow characteristics are made in the form of an array of highly sensitive nano- or micro-tubes located on the substrate at an angle to the flow in the range 0≤β≤180 °, where β is the angle between the incident flow and the tubes ; moreover, the tubes on the substrate are arranged in pairs in rows one after another on the streamline, while one of the tubes of the pair is a generator of pulse-periodic heat exposure, and the other is a sensor for recording parameters of the boundary layer.

The main advantage of the invention is the use of nano- or micro-tubes as generators and sensors. The tubes have a nanometer thickness of the conductive wall. As a result, the mass of the tube is negligible and many times less than any heating element of the same overall dimensions. And since the heat removal from the heated tube occurs only along the line of contact of the tube with the substrate and along the current paths of nanometer thickness, it can be neglected, which cannot be done in the case of a film heating element. All of the above makes it possible to introduce high-frequency thermal disturbances into the stream that cannot be introduced into the stream in any other way.

In addition, the tubes can be interchangeable and act as a generator or sensor, which allows you to change the area of the disturbance introduction, for example, to introduce disturbances at once by several rows of micro-tubes.

These features are not identified in other technical solutions when studying the level of this technical field and, therefore, the solution is new and has an inventive step.

The invention is illustrated by the illustrated drawings, which depict:

figure 1 - diagram of a device for implementing the proposed method; figure 2 - the location of the tubes on the substrate and the orientation of the tubes to the flow at β = 90 ° (top view); figure 3 - the location of the tubes on the substrate and the orientation of the tubes to the flow at β = 45 ° (135 °) (top view); figure 4 - the location of the tubes on the substrate and the orientation of the tubes to the flow at β = 0 ° (180 °) (top view).

Figure 1 schematically, as an example, shows the elements, effects and registration of flow characteristics made in the form of an array of highly sensitive nano or micro tubes located on the substrate at an angle to the flow β = 90 °, where β is the angle between the incident flow and pipes; moreover, the tubes on the substrate are arranged in pairs in rows one after another. The dimensions of the tubes (diameter and length), their location relative to each other and relative to the incoming flow are determined by the problem being solved. The diameter of the tubes can be from 1 to 50 micrometers, the length is from 0.1 to 5 millimeters, and the wall thickness is from several tens of nanometers to hundreds of nanometers. If the wall thickness does not exceed 100 nm, then the micro-tube falls under the definition of a nano-object and can be called a nanotube. A pair of tubes consists of a generator tube 1 and a sensor tube 2. The tubes are mounted on low-resistance conductive paths 3 (not shown in FIGS. 2, 3 and 4) on the substrate 4. The location of the tubes on the aircraft surface is determined by the geometry of the streamlined surface and the problem to be solved. Figure 2, 3, 4 shows the options for the location of the tubes on the substrate relative to the incoming flow. The main condition for the location of the tubes to the flow is that the generator tube 1 and the sensor tube 2 must be located on the current lines that determine the direction of the particles in the stream. It is by this arrangement that the maximum accuracy of determining the flow parameters when exposed to it by a tube-generator is achieved. Low resistance conductive tracks 3 (Fig. 1) are brought from each tube 1 and 2 to the lateral edges of the substrate 4, which is necessary for communication with a control system for controlling the effects on the boundary layer in real time (not shown). The nano- and micro-tubes used are complex tubular elements (see FIG. 1), consisting of a compressed layer 6, an extended layer 7 and a conductive layer 8. Layers 6, 7 and 8 can be made of various combinations of amorphous, polycrystalline or single crystal metals dielectrics or semiconductors. Variants are possible when the tube is formed only from layers 6 and 7, which are simultaneously conducting electric current. The substrate material 4 may also be an amorphous, polycrystalline or single crystal metal, dielectric or semiconductor. In the case of the conductive substrate 4, it is necessary to provide electrical insulation using a dielectric as layer 5 or layer 6.

The proposed method is implemented by the device as follows.

The operation of the device for controlling the boundary flow can be considered using the example of a control unit cell and a control system for the parameters of influence on the boundary layer. An elementary control cell can be considered a pair of tubes located one after another. The tube-sensor 2 using the control system in a continuous mode determines the perturbations existing in the stream. Then, from a control system, a signal of a certain frequency and intensity is supplied to the tube-generator 1 to introduce a thermal pulse-periodic disturbance into the flow. The frequency and intensity of the introduced disturbances is selected in such a way as to minimize the disturbances recorded by the sensor tube 2. Since the mass of the micro tubes is negligible, they can be heated by a current pulse and cooled by the incident flow with a high frequency of about 500 kHz and higher. This circumstance makes it possible to use the proposed system not only at subsonic speeds, but also at supersonic and hypersonic flow velocities, where high-speed processes affecting the transition from the laminar flow regime to turbulent occur at frequencies of the order of hundreds of kilohertz.

The control unit cells are combined into tube arrays on the substrate 4. The combined control unit cells are rows of tubes. In this case, a number of tubes 1 acts as generators of a pulse-periodic thermal effect, and the other row 2 serves as sensors for recording flow parameters. Moreover, as generators of thermal disturbances, not only one row of tubes can act, but also several. Thus, the size of the perturbation introduction region can be operated on. Each tube can work both in the mode of generator 1 of thermal disturbances and in the mode of sensor 2 of flow parameters, and the change of the operating mode can be carried out in real time by the control system of the parameters of influence on the boundary layer. This allows one to operate on the location of the introduction of disturbances. Since each tube can operate both in generator 1 mode and in sensor 2 mode, this allows thermal disturbances to be introduced not only along the line of a number of tubes, but also disturbances of complex spatial shapes. The number of tubes and the distance between the ends of the tubes can be arbitrary. In the case of the smallest technologically possible distance between the ends of the tubes, we can talk about the line of the tubes. The distance between the rows of tubes can also be arbitrary. The minimum distance between the rows of tubes is determined by the width of the current-carrying tracks 3 and their number.

Thus, the use of the proposed invention provides active control of the boundary layer and an increase in the frequency range of the impact on the stream.

Claims (3)

1. A method of controlling the boundary layer on the surface of an aircraft, including a pulse action on the boundary layer, recording the flow characteristics, adjusting the frequency and amplitude of the impact on the boundary layer in real time, characterized in that the impact on the boundary layer and recording the flow characteristics is carried out by elements, made in the form of highly sensitive nano- or microtubes located on the surface of the aircraft, while the impact on the boundary layer leads t in a pulse-periodic thermal regime. 2. The control device of the boundary layer on the surface of the aircraft, containing the elements of the impact on the boundary layer and registration of flow characteristics located on the surface of the aircraft, as well as a control system for the parameters of the impact on the boundary layer in real time, characterized in that the elements of the impact and registration flow characteristics are made in the form of an array of highly sensitive nano- or microtubes located on a substrate at an angle to the flow within 0≤β≤180 °, where β - the angle between the flow and the tubes; moreover, the tubes on the substrate are arranged in pairs in rows one after another on the streamlines, while one of the tubes of the pair is a generator of pulse-periodic heat exposure, and the other is a sensor for recording parameters of the boundary layer. 3. The device according to claim 2, characterized in that the nano- or microtubes that perform the function of a generator or sensor can be used interchangeably.

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