RU2575503C2 - Gas exhaust nozzle and multiflow turbojet engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: aircraft nozzle comprises rear side composed by stripes distributed along the nozzle edges and extra gas jets injectors. Every stripe extends backward between the front and rear transverse wings and has free edges oriented in the directions converging backward to define the streamlined rib. Said stripes produce the turbulent swirls at the nozzle jet boundaries. Extra jets are injected ahead of the free ends of the stripes into the jet injected by the nozzle through the bores arranged ahead of the front wing to exit ahead of the stripe front plane to initiate the turbulent swirling ahead of the stripe free ends. Another invention of proposed set covers gas turbine engine with above described nozzle.

EFFECT: reduced noise of turbojet stripe nozzle noise.

6 cl, 3 dwg

Description

The present invention relates to the field of ensuring the movement of aircraft and is directed to a device that allows to reduce the noise that is emitted by a jet of traction engines, in particular the turbojet engines with which they are equipped.

Description of the prior art

Sound pollution is currently a serious research subject for minders and aircraft designers, one of the priority tasks of which is to reduce the negative sound effects of traction engines, in particular turbojet engines.

A turbojet engine, as a rule, is a multi-circuit with a primary gas stream - hot and central, emitted part of the engine forming the gas generator, and at least one cold stream, concentric with respect to the first, and called the secondary stream. The gas generator is formed by a gas turbine engine driving a fan, by means of which air is simply compressed and sent to a channel called secondary, concentric with respect to the primary flow channel. The streams can be mixed immediately after the gas generator before being discharged into the atmosphere through a single nozzle, or they can be discharged separately through concentric nozzles.

Even if noise sources are intense and plentiful, jet noise remains dominant during the take-off phase of the aircraft when the engine is operating at maximum power. This noise is caused by strong turbulent flows and shear layers created in the mixing zones of the streams having different physical properties, such as between the primary stream and the secondary stream or between the secondary stream and the surrounding atmosphere. We are talking about broadband noise, the intensity of which increases, in particular, with the speed of the jet. Jet noise has been greatly reduced in modern engines as a result of, for example, an increase in the bypass ratio, which is the ratio between cold flow and hot flow. However, there is still something to reduce.

To weaken it, one of the currently used tools is the use of devices called chevrons, which are installed on the nozzle of the primary engine flow in an engine with separate flows. This solution, although it has a negative effect on the engine’s performance during take-off and during the cruise flight, is used because of its effectiveness in reducing jet noise.

An object of the invention is the implementation of a tool that improves the efficiency of a noise attenuating agent formed by chevrons, without compromising engine performance.

However, another means of attenuation of noise generated by a stream of gases at a high speed is known, through which its mixing with the environment is accelerated. It consists in creating additional jets that are separated from the main jet and distributed along its periphery. They are fed back in a direction located at an angle relative to the longitudinal axis of the central jet with a possible tangential component. A description of this principle is given in patent FR 1195859 or also, in the case of a variant of a vented nozzle, in patent FR 1542668 on behalf of SNECMA.

EP 1,580,418 describes a noise attenuation device for a nozzle of a gas turbine engine equipped with chevrons at the rear edge, comprising a manifold to which a plurality of pipes having an azimuthal arrangement are connected. Pipes are connected with chevrons and extend beyond their flow edges. When they are fed by the manifold, air or other gas is injected directly into the turbulent flow that forms behind each chevron. This air makes it possible to delay attenuation by stimulating the central part of turbulent flows. Paragraph 21 indicated that a small stream of compressed air is injected into and interacts with turbulent flows to improve mixing between the core of the turbulent stream and the secondary stream, on the one hand, and the secondary stream and the surrounding air, on the other hand. Thus, the attenuation of the turbulent flow is slowed down and the turbulent flow cohesion over a large length behind the nozzle ridge rib, which reduces the jet noise. Additional fluid injection devices are also described in FR2929336, US2008 / 078159 and FR2929334.

SUMMARY OF THE INVENTION

The present invention is directed to improving the reduction of jet noise in a gas ejection nozzle equipped with chevrons along the periphery of its trailing edge; moreover, the concepts of "rear" and "front" are considered relative to the direction of the gas stream.

The invention relates, therefore, to a gas ejection nozzle, in particular for ensuring the movement of an aircraft, comprising at least a rear part with a streamline around the type of so-called chevrons, formed by chevrons distributed along the periphery of the nozzle. Each of the chevrons extends backward between the front transverse plane and the rear transverse plane, along the free edges oriented in two directions, converging backwards and defining the aforementioned streamline edge; moreover, chevrons provide the formation of turbulent swirls at the boundary of the jet emitted by the nozzle. According to the invention, the nozzle is characterized in that it comprises means for injecting additional gas jets located in front of said free edges of said chevrons and emerging in front of said front plane of chevrons; moreover, the means are arranged to inject additional gas jets capable of initiating the aforementioned turbulent swirls in front of the free edges.

Thus, unlike patent EP 1550418, the impact occurs before the formation of turbulent flows. Air is injected in front of the chevron in order to cause turbulent swirling in front of the ejection plane. Thus, mixing in the shear layer is improved. This solution is of double interest: it allows you to better organize mixing and reduce low frequencies, while taking advantage of additional jets or microjets, which form fewer problems with high frequencies than chevrons only.

In addition, in comparison with the patent EP 1550418, it seems possible to place the air supply pipe for the formation of additional jets in the thickness of the nozzle; they do not continue at the level of chevrons, the overall dimensions of chevrons do not increase, and the source of aerodynamic losses.

Means of injecting additional jets extending in front of said front chevron plane make it possible to initiate more efficient turbulent swirling. In particular, chevrons containing a plane of axial symmetry, means for injecting additional jets are arranged so as to inject additional jets from one and the other side of the said plane of symmetry.

To ensure the optimal effect of additional jets, they may have one or the other of the following features:

The additional jets are directed in the direction of the axis of the nozzle at an angle between 10 ° and 50 ° to the axis.

The orientation of the additional jets contains a tangential component.

All additional jets distributed along the periphery of the nozzle have the same direction or have different directions. In particular, the additional jets associated with each chevron have different directions.

Chevrons are essentially triangular or trapezoidal in shape.

The invention is directed, in particular, to a multi-circuit turbojet engine containing at least one flow ejection nozzle having at least one of the above features. This may be a nozzle of the primary stream, a nozzle of the secondary stream, or both. The invention also applies to a flow mixing chamber in the case of a mixed flow turbojet engine.

Brief Description of the Drawings

Other features and advantages of the invention will appear after studying the following description with reference to the accompanying drawings, in which:

- figure 1 is a view in axial section of a dual-circuit turbojet engine to which the invention is applied;

- figure 2 is a view, made in three quarters of the rear, jet nozzles of a turbojet engine mounted under the wing and containing the device according to the invention;

- figure 3 depicts a detail of the chevron, which is associated with the means of ejection of additional jets according to the invention.

Description of the implementation option

The turbojet engine 1 shown in FIG. 1 relates to a dual-circuit and twin-shaft type having rotation symmetry about an axis X-X ', with the release of separate flows. It is known that this turbojet engine 1 contains inside the nacelle 2, which serves as a casing for its various mechanisms, an air intake 3 through which the incoming air flow F can penetrate in order to then pass through the inlet fan 4. This air flow F is divided into two streams, respectively, primary FP and secondary FS, through the intermediate housing 5, the edge of which forms a separating spout.

In the following description, the terms “front” and “rear” refer to axial positions along the longitudinal axis X-X ′ in the direction of air flow in the turbojet engine 1.

The secondary stream FS passes through the stage of the straightening apparatus in order to then be ejected behind the turbojet engine through the nozzle 20 of the cold or secondary stream. The primary stream FP sequentially passes through stage 6 of the low pressure compressor, stage 7 of the high pressure compressor, combustion chamber 8, stage 9 of the high pressure turbine and stage 10 of the low pressure turbine in order to then be ejected outside the turbojet through the nozzle 30 of the primary stream.

The nacelle 2 of this turbojet is ring-shaped and is located coaxially around the longitudinal axis X-X '. It allows you to direct the gas flows generated by a turbojet engine, determining the internal and external lines of aerodynamic flow for gas flows.

The air intake 3, the axis of which coincides with the axis X-X 'of rotation of the turbomachine I, contains an air intake channel 11, as well as an air intake cone 12. The latter allows the aerodynamic direction and distribution of the total flow F around the axis X-X '.

The primary flow nozzle 30 defines, together with the exhaust cone 31, an annular space through which the primary flow FP is discharged.

The secondary flow nozzle 20 defines, together with the primary flow fairing, an annular space through which the secondary flow FS is discharged.

According to the example shown in figure 2, through the annular space passes the pylon P, on which the engine is suspended.

As is known, the noise of the jet is reduced due to the arrangement of elements in the form of triangular or trapezoidal shields behind the edges of one or two nozzles, in this case, two nozzles according to the embodiment shown in FIG. 2. These elements 40, called chevrons, are fastened by their widest side to the nozzle and extend between the front plane against the ejection area from the nozzle and the rear plane; preferably, they form a nonzero angle with the axis XX of the engine. In this case, they all have the same shape and dimensions, but they can also be different along the periphery of the nozzles. The free edges of the chevrons are oriented in convergent directions between the front plane and the rear plane. They are rectilinear or also have curved parts. The overall shape of the flow rib is thus the saw teeth along the periphery of the nozzle. This arrangement contributes to the formation of turbulent flows in the shear layer between the primary and secondary flows and between the secondary stream and the surrounding air.

The effectiveness of chevrons is improved, according to the invention, by initiating the swirling of turbulent flows in front of the relatively free edges 41 and 42 of the chevrons.

This result is achieved by injecting additional gas jets into the main primary or secondary stream by means of injecting additional gas jets in the device 50 in front of the free edges 41 and 42, in particular in front of the chevron front plane 43. Figure 3 shows the chevron 40. In this embodiment, it has a triangular shape and is rigidly connected to the secondary nozzle 20 with its edge located in the front plane 43. The inner side of the nozzle 20, shown from the axis XX, is drilled with two holes 51 and 52, in which pipes 53 and 54, which are supplied with air or exhaust gas from the collector 55, exit. A part of the pipes elongated along the secondary flow fairing is shown in FIG. The power from the collector 55 is controlled by a valve 56. Two holes 51 and 52 are located in front of the front plane 43 and provide additional jets A1 during operation of the noise attenuator. According to this embodiment, each jet is oriented along the axis of the main jet in the direction of the edge. Preferably, they are tilted in the direction of the axis of the engine at an angle possibly equal to the angle of inclination of the chevron with which they are associated. According to another embodiment, they may have different orientations, for example, they may diverge. Their deviation, as well as their diameter, are parameters to consider. This also applies to the thermodynamic parameters of additional jets, such as pressure, temperature and flow.

Figure 3 shows two holes for the formation of two additional jets for the chevron, but in the framework of the invention also assumes a different number of additional jets and an arrangement different from that shown.

During the take-off of the aircraft, they want to activate the jet noise attenuator, control the valve 56, setting the collector in communication with the air source at the level of the gas generator, in particular. Additional jets flowing out of the holes 51 and 52 will lead to the formation of turbulent flows, which due to their position will be strengthened by the passage of the free edges 41 and 42 of the chevron. Turbulent flows of the opposite rotation, thus created behind the chevron, are more energetic and allow for better mixing of the flows, reducing low-frequency radiation.

Claims (6)

1. A gas ejection nozzle for supporting the movement of an aircraft, comprising a rear part with a chevron flow stream formed by chevrons (40) distributed along the periphery of the nozzle; moreover, each of the chevrons passes back between the front transverse plane (43) and the rear transverse plane and has free edges oriented in two directions, converging backwards and defining the aforementioned streamline edge; moreover, chevrons provide the formation of turbulent swirls at the boundary of the jet emitted by the nozzle, characterized in that it contains means (50) for injecting additional gas jets (A1); moreover, said additional jets are injected in front of said free edges (41, 42) of chevrons into the jet ejected by the nozzle through openings (51, 52) located in front of said front plane so as to go out in front of said front plane (43) of chevrons to initiate said turbulent twisting in front of the free edges of the chevrons. 2. A nozzle according to claim 1, the chevrons (40) of which contain an axial plane of symmetry, and the means for injecting additional gas jets are arranged so as to inject additional jets from one and the other side of the said plane of symmetry. 3. The nozzle according to claim 1, the means for injecting additional gas jets of which are arranged so as to inject additional jets towards the axis of the nozzle at an angle between 10 ° and 50 ° to the axis. 4. The nozzle according to claim 1, containing means for injecting additional gas jets arranged in such a way as to inject additional jets containing a tangential component relative to the axis of the nozzle. 5. The nozzle according to claim 1, the chevrons of which are essentially triangular or trapezoidal in shape. 6. A turbojet multi-circuit engine containing at least one gas discharge nozzle according to any one of the preceding paragraphs.

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