RU2807307C1 - Output device of a turbojet engine - Google Patents

Abstract

FIELD: turbojet engines of aircraft.

SUBSTANCE: invention relates to turbojet engines of aircraft. The output device of the turbojet engine (turbojet engine) (14) of the aircraft contains a shell (1) docked to the aft part (15) of the fairing (16) of the turbojet engine, made with the possibility of axial movement, and an inner nozzle (2). The inner nozzle (2) contains an inlet section (3) rigidly fixed to the body Turbojet engine (14) at the outlet (17) of the jet stream (18), the outlet section (4) and the housing (5) of the inner nozzle located between them. The body of the inner nozzle (5) is made of segments (6), closed to each other by side surfaces (7). All or part of the segments (6) are made with the possibility of moving up to the formation of cracks (8) between adjacent side surfaces (7).

EFFECT: it is possible to reduce the acoustic noise level created by the engine with the appropriate requirement for its operation mode.

6 cl, 5 dwg

Description

The invention relates to aviation, in particular to output devices of aircraft turbojet engines, designed to reduce the level of generated acoustic noise.

The cruising flight of supersonic passenger aircraft (SPA) is possible using turbojet engines with a low bypass ratio (m<2), which leads to a high jet exhaust speed and, as a consequence, a high level of acoustic radiation during takeoff and landing modes. However, the regulatory framework regulating the noise level in the area for ATP is in the process of development and is currently missing.

One of the main requirements for SPS engines is a low level of noise on the ground during takeoff and landing. To implement this requirement, it is necessary to design an engine that has a low exhaust speed of the jet stream of its output device (but at the same time sufficient to provide the necessary thrust in this mode).

Reducing the exhaust velocity can be achieved, for example, by designing an outlet device from a turbojet engine.

An exhaust nozzle of an air-jet engine is known, which contains a housing consisting of a subsonic part, tapering in the cross-section of the nozzle cavity and having a rectangular shape in the outlet section, and a supersonic part with an increasing area of the rectangular cross-section of the nozzle cavity along the gas flow, docked with the subsonic part in its outlet section and having upper, lower and vertical walls and rotary flaps, hinged on the upper and lower walls of the housing with hinge axes located in the planes of these walls, to change the direction of gas flow and the flow area of the cavity of the supersonic part of the nozzle, different in that the upper and lower walls of the supersonic part are installed at an angle to the axis of the nozzle and are equipped with cutouts, each of which houses each of the rotary flaps, each rotary flap is equipped with two vertical partitions located on the side edges of the flaps on the side opposite to the nozzle cavity, and associated with the side edges of the jumpers between the cutouts in the walls, and the cutouts in the upper and lower walls are made in a checkerboard pattern and are equal in width to the width of the jumpers between them (Utility model patent RU No. 156534 U1, IPC F02K 1/12; publ. 10.11.2015).

During takeoff and landing mode, adjacent flaps of the upper row, synchronously with the flaps of the lower row, are deflected in a checkerboard pattern (in opposite directions). The deflectable flaps of the upper and lower rows are made with lateral longitudinal partitions, which prevents the lateral flow of outside air under the flap into the vacuum region, which impairs the mixing of the high-pressure jet with the outside air and, as a consequence, the effectiveness of noise attenuation. In cruising flight mode, all doors of the upper and lower rows are deflected at the same angles, creating an optimal degree of jet expansion. The upper and lower walls of the outlet part are installed at an angle to the axis of the nozzle and are equipped with cutouts, in each of which one of the rotary flaps is placed, each rotary flap is equipped with two vertical partitions located on the side edges of the flaps on the side opposite to the nozzle cavity, and coupled with the side the edges of the jumpers between the cutouts in the walls, and the cutouts in the upper and lower walls are made in a checkerboard pattern and are equal in width to the width of the jumpers between them. This design of the exhaust nozzle makes it possible to reduce the thermal stress of the nozzle parts, in particular the vertical walls dividing the nozzle exit section into separate sections, since all nozzle parts in all operating modes are effectively cooled by the oncoming air flow.

The disadvantages of this solution are the side partitions protruding into the outer area of the nozzle, leading to an increase in aerodynamic drag, as well as the lack of shielding of the high-pressure jet mixing zone, which is the main source of noise during takeoff/landing modes.

A noise-attenuating nozzle of an air-jet engine is known, containing subsonic and supersonic parts with a rectangular critical section of the nozzle, upper and lower rows of flaps located in the supersonic part, deflected by a noise-attenuating control signal, characterized in that the supersonic part of the nozzle is extended downstream by means of the lower and side walls with an increase in cross-sectional area along the flow, and also additionally contains an ejector for supplying external air to the supersonic part of the nozzle through the outlet openings under the lower row of flaps (Patent for invention RU No. 2732360; IPC: F02K 1/00, F02K 1/06, F02K 1/ 12, F02K 1/36, F02K 1/46; published 09.15.2020).

In the known nozzle, the flaps are controlled automatically by a control system, which, in modes requiring noise attenuation (takeoff and landing), supplies a noise attenuation control signal, according to which the flaps are installed in the required position, while the difference in the deflection angles of adjacent flaps of the upper row is 5 ...20°, and the deflection occurs synchronously with the lower row doors located underneath them.

The disadvantage of the nozzle is that it is a one-way expansion nozzle, which will lead to the creation of a torque in the longitudinal direction and will inevitably complicate the control of the aircraft, in addition, since the lower and side walls of the nozzle also exist in supersonic flight mode, this will create additional drag.

The prototype of the invention is an output device used to reduce the noise of a jet engine, containing a shell docked to the aft part of the turbojet engine fairing, made with the possibility of axial movement, and an internal nozzle containing an inlet section, rigidly attached to the turbojet engine body at the point where the jet flow exits, the outlet section, located relative to the inlet along the flow and the body of the internal nozzle located between them (Patent document US 2002092948 (A1); IPC B64D 33/02, F02K 1/46, B64D 29/00; publ. 07/18/2002).

If it is necessary to reduce the noise level created by the turbojet engine, the shell moves in the axial direction, forming a gap between it and the fairing, while the external air ejected through it mixes with the flow of the gas-air mixture emanating from the outer cut of the internal nozzle, reducing the flow speed and, therefore, thereby reducing the level of generated acoustic noise.

The disadvantage of the prototype is that in modes of movement around the airfield, takeoff or landing, due to the low speed of the aircraft, the amount of ejected air will not be large, which will not allow reducing the speed of the gas-air mixture from the outer cut of the internal nozzle and the damping of the level of generated acoustic noise will be insufficient .

The technical problem solved when creating the invention was the creation of a jet flow output device from a turbojet engine, providing the ability to reduce the level of acoustic noise created by the engine with appropriate requirements for its operating mode.

The solution to the problem is a technical solution that represents the essence of the invention: an output device for a turbojet engine (TRE), containing a shell, docked to the rear part of the turbojet fairing, made with the possibility of axial movement, and an internal nozzle containing an inlet section, rigidly attached to the body of the turbojet engine in place the outlet of the jet stream, the outlet section located relative to the inlet along the flow direction, and the body of the internal nozzle located between them, wherein the body of the internal nozzle is made of segments connected to each other by side surfaces, with the possibility of moving all or part of these segments to form cracks between adjacent side surfaces, respectively.

The technical result achieved by implementing the invention is the ability to reduce the level of acoustic noise created by the engine with appropriate requirements for its operating mode.

In special cases of execution:

- to optimize the kinematic scheme during the formation of cracks, the internal nozzle can be made with the possibility of radial movement of the ends of the movable segments located at the outlet cut relative to the axis of the internal nozzle;

- to increase the rigidity of the structure, if it is possible to move a part from the body segments, the ends of the non-movable segments of the internal nozzle body, located at the outlet, can be rigidly connected to each other;

- to accelerate the flow velocity from the nozzle outlet, during the cruising mode of operation of the turbojet engine, the area of the inlet section of the internal nozzle can be greater than the area of the outlet section, while, to optimize the manufacturability of the design, the body of the internal nozzle can be made in the form of a truncated cone;

- to form the direction of the vector of the mixed reactive flow when the shell moves to its extreme position, the outlet section of the shell can be located further downstream of the jet flow than the outlet section of the internal nozzle.

When disclosing the essence of the invention, the following graphic materials are used:

Fig. 1 - Fragment of a turbojet engine with an installed output device during cruising flight mode, isometric image (a special case of an internal nozzle in the form of a truncated cone);

Fig. 2 - Fragment of a turbojet engine with an installed output device when the turbojet engine is operating in the mode of reducing the level of generated acoustic noise, isometric image (a special case of the design of the internal nozzle in the form of a truncated cone and the ability to move all segments);

Fig. 3 - Fragment of a turbojet engine with an installed output device when the turbojet engine is operating in the mode of reducing the level of generated acoustic noise, isometric image (a special case of an internal nozzle in the form of a truncated cone and the ability to move part of the segments);

Fig. 4 - Axial section Fig. 1 - diagram of the formation of a jet stream of a turbojet engine when the output device is operating in normal cruising flight mode;

Fig. 5 - Axial section Fig. 2 or Fig. 3 - diagram of the formation of a jet jet of a turbojet engine when the output device operates in the mode of reducing the level of generated acoustic noise.

The invention relates to all types of turbojet engines (TRD), in which during operation a jet stream is created, which is the propulsion device of the vehicle, including double-circuit engines, etc.

The output device of the turbojet engine contains a shell 1 and an internal nozzle 2 (Fig. 1-3).

The shell 1 is docked to the aft part 15 of the fairing 16, for example a nacelle, of the turbojet engine 14 along the jet stream 18 from the turbojet engine (Fig. 1).

The docking is carried out with the possibility of axial rectilinear movement of the shell 1, along the axis of the jet stream flow 18, relative to the fairing 16 with the formation of a gap 19 between the end of the shell and the rear part 15 of the fairing, respectively.

The shell can be moved using a controlled mechanism 20 with an electric, pneumatic or hydraulic drive, mounted on the housings of the fairing 16 and the shell 1.

The internal nozzle 2 contains an input slice 3 and an output slice 4. The slices represent the contours of the nozzle body along its holes, through which the jet stream (jet stream) from the turbojet engine enters the internal nozzle and, transformed, exits it in the form of a jet stream during operation Turbojet engine in normal cruising flight mode.

During installation, the input section 3 is rigidly fixed to the body of the turbojet engine 14, for example, with bolted connections, at the point of exit 17 of the jet stream 18 from the turbojet engine, and the output section 4 is located along the flow direction relative to the input one.

Between the inlet section 3 and the outlet section 4 there is a body 5 of the internal nozzle.

The body of the internal nozzle 5 is made of segments 6. The segments are closed to each other by side surfaces 7. This makes it possible to move all or part of these segments to form gaps 8 between adjacent side surfaces 7, respectively. The movement of the movable segments can be carried out by means of their articulated connection with the turbojet engine using controlled mechanisms 21 with an electric, pneumatic or hydraulic drive, mounted on the outer surfaces of these segments 16 and the turbojet engine body.

To optimize the kinematic diagram during the formation of cracks, the internal nozzle can be made with the possibility of radial movement of the ends 11 of the movable segments 6 located at the outlet cut 4 relative to the axis 10 of the internal nozzle.

To increase the rigidity of the structure, if it is possible to move parts of the segments 6 of the body 5, the ends 12 of the non-movable segments 6 of the body 5 of the internal nozzle 2, located at the outlet 4, can be rigidly connected to each other 12, for example, by a rim rigidly fixed to them 13 (Fig. 3).

The output device works as follows.

During the normal - cruising mode of operation of the turbojet engine, the shell 1 is docked to the aft part 15 of the fairing 16 of the turbojet engine, forming with it an integral (without gaps) outer surface, segments 6 of the internal nozzle 2 are closed to each other by adjacent side surfaces 7, forming an integral (without gaps) surface of the side housing 5.

The jet stream 18 enters from the turbojet engine into the inlet section 3 of the internal nozzle, passes inside the cavity 23 limited by closed segments 6, leaving the outlet section 4, when it flows around the section of the internal nozzle, it expands in the area 24, in areas adjacent to its contour and mixes with air 25 from the ejector circuit 9 formed by the outer surface of the turbojet engine and the adjacent surface of the fairing. When the flows mix, a “liquid wall” is formed and a self-similar nozzle flow regime occurs. (Fig. 4). As a result, a free jet is formed, which is attached to the shell. Due to viscosity, a turbulent mixing layer 26 develops at the boundary of the free jet, into which a certain amount of ejector air from the recirculation zone 27 is drawn in. In this zone and on most of the surface of the free jet, the same pressure is established everywhere. Only in the area where the flow attaches to the shell is a local increase in static pressure caused by gas compression in the shock wave. To reduce losses associated with the turbulent mixing layer 26 and the shock wave, the supply of ejector air 25 is increased and the optimal length of the shell is selected so that the point where the flow joins the shell is as close as possible to its outlet section 22, and also to reduce the intensity of the shock, so as otherwise there will be increased losses due to the growth of the boundary layer and losses in additional shock waves. After the shell is cut, the mixed flow flows out in the form of a jet stream 28.

To accelerate the speed of the jet flow from the output section 4 of the internal nozzle, during the cruising mode of operation of the turbojet engine, the area of the input section 3 of the internal 2 nozzle can be greater than the area of the output section 4.

Also, taking into account the optimization of the manufacturability of the design of the body of the internal nozzle 2, it can be made in the form of a truncated cone (with closed segments 6, respectively (Fig. 1).

If it is necessary to reduce the level of acoustic noise created by the turbojet engine, the shell 1 moves relative to the aft part 15 of the fairing 16 of the jet engine, to the extreme position, forming a gap 19 between the end of the shell and the aft part 15 of the fairing (Fig. 2, 3).

Segments 6 of the internal nozzle 2, moving, open, resulting in the formation of gaps 8 between adjacent side surfaces 7, respectively.

The presence of a discontinuity in the contour leads to the emergence of three different flow regimes in the ejectron nozzles, determined by the degree of pressure reduction in the nozzle π _C. At the beginning, a separation regime is formed when the boundaries of the jet stream flowing from the internal contour are sufficiently far from the inner surface of the shell. In this mode, the relative pressure in the ejector contour of the nozzle and the thrust loss change quite slightly with a change in π _C. In this mode, the ejector circuit communicates with the environment (atmosphere). The end of the separation mode and the beginning of the transition mode is accompanied by the beginning of a sharp decrease in pressure in the ejector circuit and an increase in thrust losses. In this case, the maximum pressure drop and the peak of thrust losses correspond to the moment the mixing layer of the jet stream touches the edge of the shell. This moment characterizes the end of the transition and the beginning of the self-similar regime and is called the nozzle launch moment. Depending on the geometry, the transition regime can occur in a very narrow range of changes in π _C. With a further increase in π _C , a self-similar flow regime occurs when the pressure in the ejector circuit ceases to depend on the ambient pressure. In this case, the thrust losses change in the same way as the losses of conventional supersonic nozzles with a rigid contour, that is, they correspond to the overexpansion, design and underexpansion modes.

The jet flow 18 enters from the engine into the inlet section 3 of the internal nozzle, the main flow is separated due to open slits, and air is sucked in from the external atmosphere 29 due to the retracted shell. Due to the splitting of the main flow and mixing it with external air in the area 30 between the inlet section of the nozzle 3 and the ends of the segments, the speed of the jet stream decreases (Fig. 5).

Numerous jets of the main gas flow from the engine draw the flow of ejected air under the shell and intensively mix with it, leveling the forward momentum, after which the mixed flow of the jet stream 31 flows out through the cut of the shell at a reduced speed.

To form the direction of the mixed flow vector when moving the shell 1 to its extreme position, the outlet section 22 of the shell 1 can be located further downstream of the jet flow than the outlet section 4 of the internal nozzle (taking into account that during any movements of the segments, their ends do not go beyond the contour, limited by the exit cut in the closed position).

At different temperatures of the secondary (ejected) 29 and primary (main) 18 flows, the ratio of the reduced air flow rates must be equal, which is estimated by the formula

Where:

index “2” - ejected air circuit;

index “1” - main thread;

- ejection coefficient;

- reduced ejection coefficient;

- relative total pressure in the secondary flow.

The acoustic power of the jet W, in accordance with the Lighthill theory, is produced according to the gas-dynamic and geometric parameters of the jet in the outlet section of the jet nozzle.

The best agreement between the calculated data and the experimental data for cold and hot jets is observed when calculating W using formula 1:

Where - proportionality coefficient, which is equal to:

- speed and density of the jet at the nozzle exit section;

- flight speed;

- area of the nozzle exit section;

- speed of sound in the environment.

As can be seen from the formula for the acoustic power of the jet, with a decrease in the speed of exhaust from the nozzle, this power decreases.

The maximum noise level created by aircraft engines in static conditions or during its take-off run is determined by the relationship:

Where - acoustic power emitted by one engine, W;

- distance from the listening point to the aircraft in the direction of maximum radiation;

- coefficient taking into account the surface of noise propagation;

- directional factor;

- coefficient that takes into account the additional attenuation of noise at the total level as it propagates along the earth's surface;

- coefficient taking into account the number and relative position of engines on the aircraft.

It was said earlier that with a decrease in the flow rate from the nozzle, the acoustic power decreases. As can be seen from the formula above, with a decrease in acoustic power, the maximum noise level created when the output device operates in the mode of reducing the level of acoustic noise created by the turbojet engine decreases.

Thus, the achievement of a technical result is ensured - the ability to reduce the level of acoustic noise created by the engine with the corresponding requirements for its operating mode, for example, when moving along an airfield, takeoff or landing.

Claims (6)

1. The output device of a turbojet engine (TRE) contains a shell, docked to the rear part of the turbojet fairing, made with the possibility of axial movement, and an internal nozzle containing an inlet section, rigidly attached to the turbojet engine body at the point of exit of the jet flow, an outlet section and the body of the internal nozzle , located between them, characterized in that the body of the internal nozzle is made of segments, closed to each other by side surfaces, with the possibility of moving all or part of these segments to form gaps between adjacent side surfaces, respectively. 2. The output device of the turbojet engine according to claim 1, which provides the possibility of radial movement relative to the axis of the internal nozzle of the ends of the movable segments of the internal nozzle body located at the outlet. 3. The exhaust device of the turbojet engine according to claim 1 or 2, in which, if it is possible to move a part from the body segments, the ends of the non-movable segments of the internal nozzle body, located at the outlet, are rigidly connected to each other. 4. The output device of a turbojet engine according to claim 1, in which the area of the inlet section of the internal nozzle is greater than the area of the outlet section. 5. The output device of the turbojet engine according to claim 4, in which the body of the internal nozzle is made in the form of a truncated cone. 6. The output device of a turbojet engine according to claim 1, in which when the shell moves to its extreme position, the outlet section of the shell is located further downstream of the jet flow than the outlet section of the internal nozzle.