RU2215669C1 - Combined method of reduction of notability of flying vehicle power plant in radar, infra-red and acoustic ranges of waves at change of thrust vector - Google Patents

Abstract

FIELD: protection of flying vehicles against destruction. SUBSTANCE: screening unit made in form of anti-radar and anti-infrared grids reducing acoustic notability is placed in flow of gas. Anti-infrared grid is placed closer to engine as compared with anti-radar grid which is placed after anti-infra-red grid in direction opposite to flight. EFFECT: enhanced protection of flying vehicle due to reduced notability of power plant in all aspect of screening. 17 cl, 17 dwg, 1 tbl

Description

 The invention relates to a means of reducing the visibility of an aircraft (LA), in particular its power plant (SU).

Недостатками известного способа уменьшения заметности силовой установки летательного аппарата являются:
- не обеспечивает защиту от волн длин инфракрасного и акустического диапазона, так как сквозь щели между стержнями просматриваются нагретые элементы сопла;
- не обеспечивает уменьшения заметности со всех ракурсов, в частности, перпендикулярных и близких перпендикулярным образующей конуса;
- не позволяет избежать потери тяги и увеличения проходного сечения сопла из-за того, что стержни расположены на незначительном расстоянии друг от друга

- не обеспечивает защиту от радиолокационных волн малой длины, т.к. с уменьшением длины волны уменьшаются расстояния между стержнями;
- не обеспечивает защиту летательных аппаратов звукового и сверхзвукового диапазона скоростей полета;
- не обеспечивает возможности регулировать вектор тяги.A known method of reducing visibility in the radar (RL) wavelength range (US patent 4149689 from 04.17.1079) [1], which is the placement of many closely spaced metal rods in front of the air intake and behind the nozzle exit of the power plant in the form of a grill, the rods being located on insignificant distance from each other - L, depending on the wavelength of the irradiating radar station λ, and

The disadvantages of the known method of reducing the visibility of the power plant of the aircraft are:
- does not provide protection against wavelengths of infrared and acoustic ranges, since heated nozzle elements are visible through the cracks between the rods;
- does not reduce the visibility from all angles, in particular, perpendicular and close to the perpendicular generatrix of the cone;
- does not allow to avoid loss of thrust and increase the nozzle orifice due to the fact that the rods are located at a small distance from each other

- does not provide protection against short-range radar waves, because with decreasing wavelength, the distance between the rods decreases;
- does not provide protection for aircraft sound and supersonic range of flight speeds;
- does not provide the ability to adjust the thrust vector.

 The technical result of the invention is the possibility of reducing the visibility of the power plant of the aircraft in the radar, infrared, acoustic wavelength ranges, ensuring the reduction of its visibility in all aspects of the shielding of the power plant, ensuring the reduction of traction loss and control of the thrust vector of the power plant.

 The specified result is achieved by the fact that in the method a shielding device is installed in the gas stream, which is made in the form of anti-radar and anti-infrared gratings that reduce acoustic signature. In this case, the anti-infrared grating is placed closer to the engine of the power plant than the anti-radar grating.

 The anti-radar grid is located behind the anti-infrared grid in the direction against the flight of the aircraft. The gratings are interconnected by a detachable connection or integrally, placing parts of the ribs of the anti-infrared grating between the ribs of the anti-radar grating.

 The ribs of the anti-infrared grating are inclined or profiled to smoothly change the direction of gas flow. The input and output sections of each channel of the grating do not overlap each other in projection onto a vertical plane. The edges of the anti-infrared grating are radial.

 Lattices are located in the subsonic or sound part of the nozzle.

 To eliminate thrust loss during flight without providing low visibility, at least one of the grilles is removed in the aircraft body. In one embodiment, the device is rotatable in any plane to any given angle α to change the thrust vector of the power plant.

 In another embodiment, the ribs of the anti-infrared grating are rotatable to change the thrust vector.

With a supersonic nozzle, the device does not protrude beyond the critical section of the nozzle. The angle between the surface of the supersonic part of the nozzle and the outer surface of the device exceeds 90 ^o .

 In the subsonic or sonic parts of the nozzle, slots are made for the movement of the device in them when cleaning it and / or when adjusting the characteristics of the nozzle.

 For a supersonic adjustable nozzle, the device is configured to eliminate the complete overlap of the nozzle.

The device can be made of two wings with the formation between them in the closed state of an angle of 100-110 ^o .

 The essence of the method is illustrated by drawings.

 In FIG. 1 shows a diagram of an aircraft engine with a subsonic nozzle and the proposed universal device.

 Figure 2 shows a diagram of an adjustable supersonic nozzle with the proposed variant of a universal device.

 Figure 3 - diagram of the anti-radar grid.

 Figure 4 - diagram of the options anti-infrared grating.

 Figure 5 shows the effectiveness of the proposed nozzle device.

 In FIG. 6 shows the indicatrix of infrared radiation without devices to reduce visibility.

 Figure 7 shows the indicatrix of infrared radiation using devices to reduce visibility.

 In FIG. Figure 8 shows a graph of the change in the combustion temperature of thermal false targets over time.

 In Fig.9 is a variant of a universal device for a supersonic nozzle.

 Figure 10 - diagram of the various lattices for the subsonic and sonic nozzles and the influence of their type on the loss of traction SU.

 Figure 11 - SU with a change in the thrust vector with the help of rotary wings.

 On Fig shows a diagram of SU with the proposed variant of the device to reduce the visibility and rotation of the thrust vector.

 On Fig shows a part of the anti-infrared grating.

 On Fig - flat nozzle with the proposed universal device.

 On Fig - lattice with radial ribs.

 On Fig - installation of the grill in front of the SU.

 On Fig is a graph of the decrease in the time of hearing the volume in time.

 The implementation of the method is illustrated by the example of the device.

 In the radar wavelength range.

 When an aircraft is irradiated from the rear hemisphere (RPS) of an adversary’s radar station (radar), electromagnetic waves do not enter SS 1 due to the presence of an anti-radar array 2 of the proposed universal device (device) 3.

где λ - длина облучающей РЛС, при этом глубина W ячейки определяется из соотношения
P = P_o•e^-2β•W,
где W - глубина канала,
β - коэффициент (определяется по графику на стр. 56 [2]);
Р - энергия, прошедшая через решетку;
Р₀ - падающая энергия.Missing electromagnetic energy in the nozzle 4 SU 1 is achieved by the fact that the sizes of the cells 5 of the lattice are selected accordingly. So, with a square cell, its size A (Fig. 3) should be no more

where λ is the length of the irradiating radar, while the depth W of the cell is determined from the relation
P = P _o • e ^{-2β • W} ,
where W is the depth of the channel,
β is the coefficient (determined by the schedule on page 56 [2]);
P is the energy passed through the lattice;
P ₀ is the incident energy.

 P is equal to zero or any small value depending on the requirements for reducing visibility, and with the known β is W. The thickness D is selected according to the strength conditions of the device.

 In this case, the energy does not fall into the SU of the aircraft (P = 0) and its visibility in the radar range — the effective scattering surface σ — decreases by almost two orders of magnitude (Fig. 5).

 In the infrared wavelength range.

 Figure 1 shows a diagram of a SU LA.

 On various parts of the SS are marked with numbers from 1 to 12 points.

 The temperature of these points is shown in the table for one of the operating modes of the control system.

The table shows that the lowest temperature at the nozzle exit (point 6). Therefore, if you shield hot spots and make sure that the missile’s thermal homing head (TGS) “sees” only the nozzle section, then the probability of its hovering in the control aircraft is equal to one, since the TGS responds to a temperature of 430-650 ^o .

The function of the screen is performed by the anti-infrared lattice 6 of the proposed device 3. Its channels 7 (Fig. 4) are made in such a way that the SU hot spots are completely invisible from any viewing angle. To do this, they are made inclined or profiled (to gradually turn the flow in order to reduce traction loss) in such a way that from any angle (± 90 ^o in azimuth, and ± 90 ^o in elevation) the rear (against flight) end face of rib 8 is higher front end of the superior rib.

Φ = ε•к•T⁴•S,
где Ф - мощность теплового излучения,
ε - коэффициент излучения,
к - постоянная, равная 5,6,7•10^-12 Вт/см² град⁴,
S - величина излучающей поверхности,
ν - пространственный угол.The effectiveness of this method allows more than an order to reduce the radiation intensity of the control system (Fig. 6, 7), calculated according to the Stefan-Boltzmann law:

Φ = ε • k • T ⁴ • S,
where f is the power of thermal radiation,
ε is the emissivity,
K is a constant equal to 5.6.7 • 10 ^-12 W / cm ² deg ⁴ ,
S is the magnitude of the radiating surface,
ν is the spatial angle.

 Since the radiation intensity J depends on the temperature of the heated body and if the temperature conditions of the control system are higher than those given (for example, in the afterburner modes of supersonic nozzles - Fig. 2), the efficiency of this method remains high even when using false thermal targets (LTC), since a much smaller number of them will be required than in the absence of a device (the time dependence of the LTC burning temperature is shown in Fig. 8). It can be seen that the lower the temperature, after which it is necessary to shoot the next LTC, the longer the time between shoots, i.e. the amount of spent LTC decreases by about 2–3 times.

All of the above applies to subsonic, sonic and supersonic nozzles. In this case, for supersonic nozzles (figure 2), the surface of the device 3 should be an obtuse angle β with the surface of the supersonic part 9 of the nozzle to avoid corner reflectors. The angle should be at least 100-110 ^o . If this cannot be ensured, then the surface of the subsonic part 10 (Fig. 9) of the nozzle between the device 3 and the critical section of the nozzle 10 should be coated with a radar absorbing material 11.

 When considering the influence of the device on traction loss (FIGS. 5, 10), it can be seen that the device causes a traction loss of ~ 3%, while the share of the anti-radar array is ~ 1%, and the share of anti-infrared is ~ 2%.

 To avoid these losses, the device 3 can be moved out of the stream when the stealth mode is not required. To do this, in the subsonic or in the sound part of the nozzle, slots 12 are made, through which the gratings are removed into the aircraft body 13 using, for example, cylinder 14 (Fig. 2).

 These slots 12 can serve to move the movable flaps 15 and 16 of the nozzle while adjusting its thrust (figure 2).

 Thus, the proposed device can reduce the visibility of SU with ZPS approximately two orders of magnitude in the radar range and more than an order of magnitude in the infrared wavelength range.

 In FIG. 10 are given including schemes of a universal device in 2 versions: with separately made anti-radar and anti-infrared gratings (option 5a) and a universal device made as a single unit of two gratings (option 5b).

 In this case, the anti-radar grating is installed between the ribs of the anti-infrared grating, which reduces the mass of the universal grating.

 The thrust vector control is as follows.

 The device comprises a shielding device installed in the gas stream and consisting of anti-radar and anti-infrared gratings. In this case, the device is made rotatable to change the vector in any given direction while maintaining the properties of the means of reducing visibility in the radar, infrared, and acoustic ranges.

 The device may be located in the subsonic or sound part of the nozzle.

 The device operates as follows.

 1. In terms of reducing the visibility of SU.

 In the radar range: there is no difference from the above.

 In the infrared range, the difference lies in the fact that the ribs 8 of the anti-infrared grating 6 have, for the same length, a larger bend or length greater than in the previous version, so that when turning the universal device 3 through the angle α, the nozzle hot spots are not visible (see Fig.13).

 2. In terms of changes in the thrust vector.

 The device comprises (Fig. 12) a universal grill 3 pivotally mounted on the housing 17 of the control system 1 with the help of cylinders 18, which ensure the rotation of the grill 3 in any direction to a predetermined maximum deflection angle α (Fig. 13).

 The installation of a universal lattice in a flat nozzle allows to expand its functionality (Fig. 5): if without a universal device the thrust vector changes only in pitch, then the universal device rotates in any direction, which, as in the case of a round nozzle, is provided with 18, allows change the thrust vector in any direction (Fig.14). A change in the thrust vector can also be obtained by rotating the ribs of the lattice 6 using, for example, a cylinder 19. The ribs are mounted on the axles 20 and combined by a thrust 21 (Fig. 11).

 Thus, the universal device not only reduces the visibility of the control system with ZPS, but also allows you to change the thrust vector in any direction. At the same time, the mass of the control system is reduced, the design is simplified, and the functions of the control system are expanded.

 The channels 7 of the lattice 6 of the universal device 3 can be of arbitrary shape, including those that can be formed by radial curved partitions (Fig. 15). At the same time, the partitions are curved along the length so that through the channels formed by them, the elements of the power plant (SU) are not visible from any angle.

 Such a lattice can be installed in front of the control system (Fig. 16) to reduce visibility both in the radar wavelength range (especially when covering the partitions with special material) and in the acoustic one.

 The operation of a universal device in the acoustic wavelength range.

 The main elements that create noise are: engine jet and fan. The noise from the fan rotating at high speed is suppressed by the grill facing the control system. The lattice behind the SU reduces the noise intensity by ~ 5-6 dB, i.e. more than 3 times; this reduces the hearing range of the aircraft by 30% (Fig.17).

где V - скорость потока,
d - характерный размер отверстия истечения,
k - частота колебаний частиц в потоке.Noise reduction using gratings is explained by the following. The noise of a gas engine jet (the main source of noise on an airplane) is explained by its turbulence and is characterized by the Strouhal number:

where V is the flow rate,
d is the characteristic size of the outflow opening,
k is the frequency of oscillation of particles in the stream.

 At the same flow rate, a decrease in the flow cross section causes an increase in frequency, and a higher frequency decays faster in air - see Fig. 17, which reduces the range with which the aircraft is heard.

Sources of information
1. US patent 4149689 from 04.17.1979.

 2. Eisenberg G.Z. VHF antennas. - M .: Communication, 1977, p. 50-56.

Claims (17)

 1. A method of reducing the visibility of the power plant of the aircraft in the radar, infrared and acoustic wavelength ranges, by which a shielding device is installed in the gas stream, characterized in that the shielding device is made in the form of anti-radar and anti-infrared gratings that reduce acoustic signature, while the anti-infrared grating positioned closer to the engine of the power plant than the anti-radar grid.  2. The method according to p. 1, characterized in that the anti-radar grid is located behind the anti-infrared grid in the direction against the flight of the aircraft.  3. The method according to p. 1 or 2, characterized in that the lattice is interconnected by a detachable connection.  4. The method according to p. 1 or 2, characterized in that the anti-radar and anti-infrared gratings are performed as a single unit.  5. The method according to p. 4, characterized in that the parts of the ribs of the anti-infrared grating are installed between the ribs of the anti-radar grating.  6. The method according to any one of paragraphs. 1-5, characterized in that the ribs of the anti-infrared grating are inclined or profiled to smoothly change the direction of gas flow.  7. The method according to p. 6, characterized in that the input and output sections of each of the channels of the lattice do not overlap each other in projection on a vertical plane.  8. The method according to any one of paragraphs. 1-7, characterized in that the edges of the infrared array perform radial.  9. The method according to any one of paragraphs. 1-8, characterized in that the lattice is located in the subsonic or sound part of the nozzle.  10. The method according to any one of paragraphs. 1-9, characterized in that to eliminate thrust loss during flight without providing low visibility, at least one of the grilles is removed into the aircraft body.  11. The method according to any one of paragraphs. 1-10, characterized in that the shielding device is rotatable to change the thrust vector of the power plant.  12. The method according to any one of paragraphs. 1-10, characterized in that the ribs of the anti-infrared grating perform rotary to measure the thrust vector.  13. The method according to any one of paragraphs. 9-12, characterized in that with a supersonic nozzle the shielding device does not protrude beyond the critical section of the nozzle. 14. The method according to any one of paragraphs. 9-13, characterized in that the angle between the surface of the supersonic part of the nozzle and the outer surface of the shielding device exceeds 90 ^o .  15. The method according to any one of paragraphs. 9-14, characterized in that in the subsonic or sound part of the nozzle, slots are made to move the shielding device in them when it is removed and / or when adjusting the characteristics of the nozzle.  16. The method according to any one of paragraphs. 9-15, characterized in that for a supersonic adjustable nozzle a shielding device is configured to exclude complete overlap of the nozzle. 17. The method according to any one of paragraphs. 1-16, characterized in that the shielding device is made of two wings with the formation between them in the closed state of an angle equal to 100-110 ^o .

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