WO2016034795A1

WO2016034795A1 - Jet nozzle of a turbine engine

Info

Publication number: WO2016034795A1
Application number: PCT/FR2015/052277
Authority: WO
Inventors: Yves-Marie LE BAYON; Guy CRABE
Original assignee: Turbomeca
Priority date: 2014-09-03
Filing date: 2015-08-27
Publication date: 2016-03-10
Also published as: FR3025255A1; FR3025255B1

Abstract

The invention relates to a jet nozzle of a turbine engine, comprising an outer wall and an inner wall defining, between each other, a flow channel for the exhaust gas; the inner wall forming a central frustoconical body oriented in a longitudinal direction. The nozzle is characterised in that the central body (32) comprises means (44) for guiding the exhaust gas in the longitudinal direction over at least part of the length of the central body (32) in the direction of flow of the gas.

Description

EXHAUST TUBE OF TURBOMOTING GAS

1. Technical field of the invention

The invention relates to a gas turbine engine exhaust nozzle. In particular, the invention relates to a gas exhaust nozzle of a turbine engine of an aircraft.

2. Technological background

One of the objectives of the gas exhausts of a turbine engine of an aircraft is the evacuation of the flue gases having passed through one or more turbines, and the ventilation of the engine bay for the thermal resistance of the equipment.

The aerodynamic performance of the exhausts at the outlet of the free turbine are closely related to the performance of the engine installed. The performance of an escapement is characterized by its ability to transform the dynamic pressure at the exit of the free turbine into a static pressure, this transformation being commonly called diffusion. The greater this diffusion in the exhaust and the higher the expansion rate of the turbine stage, contributing to increase the power delivered by the turbine engine. The nozzle (exhaust element at the outlet of the turbine and upstream of the ejector) is responsible for more than three quarters of the diffusion in the exhaust. Thus, the optimization of the aerodynamic performance of the nozzle directly impacts the specific consumption of the turbine engine.

The aerodynamic magnitude related to the performance of the exhaust that is to be improved is the static pressure recovery coefficient which is defined by:

with

the static pressure at the inlet of the exhaust,

the static pressure at the outlet of the exhaust

the dynamic pressure at the inlet of the exhaust and

the total inlet pressure of the exhaust, equal to the sum of

The exhaust inlet corresponds to the output of the free turbine. The geometric adaptation of the nozzle is essential for optimizing the performance of the nozzle. At certain speeds, an aerodynamic detachment (non-attachment of the flow to the wall) appears, which contributes to reducing the flowable aerodynamic section and the diffusion. This results in a decrease in the coefficient of recovery of the static pressure by an increase in the dynamic pressure and a decrease in the static pressure at the inlet of the exhaust, and therefore a decrease in performance.

Existing solutions offer geometric modifications that have a significant impact on the total mass of the nozzle. In particular, the integration of exotic geometries on the outer wall of the nozzle (of the "petal nozzle" type) is accompanied by an increase in the mass of the system.

3. Objectives of the invention

The invention aims to overcome at least some of the disadvantages of known gas exhaust nozzles.

In particular, the invention aims to provide, in at least one embodiment of the invention, an exhaust nozzle which makes it possible to prevent the appearance of aerodynamic detachments of the exhaust gases.

The invention also aims to provide, in at least one embodiment, an exhaust nozzle that reduces the dynamic pressure and increase the static pressure at the free turbine outlet to improve the static pressure recovery coefficient.

The invention also aims to provide, in at least one embodiment of the invention, a nozzle that improves the exhaust performance without increasing the total mass of the nozzle.

The invention also aims to provide, in at least one embodiment of the invention, a nozzle which improves the exhaust performance while reducing the total mass of the exhaust nozzle.

The invention also aims to provide, in at least one embodiment, a nozzle which contributes to reducing the fuel consumption of the engine to which it is connected.

The invention also aims to provide, in at least one embodiment, a nozzle which has a reduced cost of manufacture compared to nozzles of the prior art.

The invention also aims to provide, in at least one embodiment, a nozzle that fits most turbine engines.

The invention also aims to provide a turbine engine equipped with a nozzle according to the invention.

4. Presentation of the invention

To do this, the invention relates to a gas turbine engine exhaust nozzle, comprising an outer wall and an inner wall delimiting between them an exhaust flow stream, the inner wall forming a frustoconical central body s' extending along a direction, referred to as the longitudinal direction,

The nozzle according to the invention is characterized in that the central body comprises exhaust gas guiding means along said longitudinal direction extending at least partially along said central body.

A gas exhaust nozzle according to the invention therefore makes it possible to reduce the aerodynamic detachment by guiding the exhaust gases in the direction of its flow vein of the exhaust ga2, from the exit of the free turbine to the outside of the turbine engine. The guiding of the gases along the longitudinal direction is obtained by the arrangement of guide means on the frustoconical central body of the nozzle. The guidance of the exhaust gases along the longitudinal direction also makes it possible to reduce the dynamic pressure generated by a tangential component of the gas velocity at the outlet of the free turbine, this tangential component, orthogonal to the longitudinal direction, being due to the rotation of the free turbine, The reduction of this dynamic pressure causes an increase in the static pressure due to the preservation of the total pressure, and therefore an increase in the pressure recovery coefficient. The turbine engine is thus more efficient, which also leads to a decrease in consumption.

Advantageously and according to the invention, said exhaust gas guiding means are distributed over at least a part of the periphery of said central body.

Advantageously and according to the invention, the guide means are distributed uniformly around the perimeter of the central body.

According to this aspect of the invention, the reduction of the aerodynamic detachment and the dynamic pressure is uniform over the entire contour of the central body.

Advantageously and according to the invention, said guide means are formed on a dista! E portion of said central body in the direction of flow of gas, over a distance of between half and one third of the total length of the central body.

Advantageously and according to the invention, said exhaust gas guiding means are formed of longitudinal grooves,

According to this aspect of the invention, the grooves make it possible to form the guide means without adding new elements, therefore without addition of material and without addition of mass. The grooves are for example directly formed by the inner wall of the nozzle.

Advantageously and according to the invention, the grooves have a depth that varies between a minimum value, called the starting depth, in a proximal portion of the central body according to the direction of flow of the gases, and a maximum value, called the exit depth, in a distal portion of the central body in the direction of gas flow.

According to this aspect of the invention, the guiding of the gases by grooves having a depth gradually varying from a proximal portion of the central body - in particular a proximal end - to a distal portion of the central body - in particular a distal end - does not allow create abrupt surface change. The gradual variation of the depth between a proximal portion and a distal portion of the central body, furthermore makes it possible to obtain at the outlet guide means, gases directed in large part in the direction of flow and in the longitudinal direction.

Advantageously and according to the invention, the starting depth is between 0.5mm and 1.2mm.

Advantageously and according to the invention, the output depth is between 6mm and 15mm.

Advantageously and according to the invention, the grooves have a cross section rounded to a radius of curvature that varies between a minimum value, called the starting radius, in a proximal portion of the central body according to the gas flow direction, and a maximum value, said output radius, in a distal portion of the central body in the direction of gas flow.

According to this aspect of the invention, the reduction of the radius of curvature of each groove dug in the central body allows a progressive guidance of the exhaust gas without creating an abrupt change of radius that can cause disturbances. The reduced exit radius with respect to the starting radius makes it possible to guide the gas substantially in the direction of flow and in the longitudinal direction.

Advantageously and according to the invention, said flutes have an output radius of 6 mm.

Advantageously and according to the invention, the central body comprises between sixteen and twenty flutes guiding the exhaust gas distributed around the perimeter of the central body.

The invention also relates to a turbine engine characterized in that it comprises a gas exhaust nozzle according to the invention.

The invention also relates to a nozzle and a turbine engine characterized in combination by all or some of the characteristics mentioned above or below.

5. List of figures

Other objects, features and advantages of the invention will become apparent on reading the following description given solely by way of non-limiting example and which refers to the appended figures in which:

FIG. 1 is a schematic representation of a turbine engine exhaust comprising a nozzle according to the state of the art,

FIG. 2 is a schematic representation of an exhaust nozzle according to the state of the art,

FIG. 3 is a partial schematic representation of a central body of a nozzle according to a first embodiment of the invention,

FIG. 4 is a partial schematic representation of a central body of a nozzle according to the first embodiment of the invention,

FIG. 5 is a schematic representation of a central body of a nozzle according to a second embodiment of the invention, FIG. 6 is a set of curves representing the variations of the static pressure recovery coefficient and the specific consumption of the nozzles according to the second embodiment,

FIG. 7 is a schematic representation of a central body of a nozzle according to a third embodiment of the invention,

FIG. 5 is a set of curves representing the variations of the static pressure recovery coefficient and the specific consumption of the nozzles according to the third embodiment,

6. Detailed description of an embodiment of the invention

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments may also be combined to provide other embodiments.

FIG. 1 schematically represents a turbine engine exhaust 10 of an aircraft according to the state of the art. The exhaust 10 is designed to improve the performance of the turbine engine mainly by diffusion of exhaust gases from the gas combustion necessary for the operation of the turbine engine. The gases burned by this combustion make it possible to drive a turbine 12 free in rotation, which is generally connected to a shaft to transmit the energy of this rotation and thus allow the propulsion of the aircraft in which the turbine engine is located, for example through a propeller. At the outlet of this turbine 12, the flue gases must be discharged through the exhaust 10, which comprises in particular a nozzle 14 and an ejector 16. The gas is discharged in the direction indicated by the arrows 18. The flow of gases is in a flow channel 20 delimited externally by an outer wall 22 of the nozzle 14 and then by the ejector 16. At the junction between the nozzle 14 and the ejector 16, one or more inlets 24, 26 allow the fresh air supply, represented by the arrows 27 from a scoop 28 formed in a cover 30 surrounding and protecting the turbine engine,

At the outlet of the free turbine 12, the flow vein 20 is delimited on the outside by the outer wall 22, and on the inside by a central body 32, generally frustoconical in shape, whose axis is oriented in the direction of flow of gas, said longitudinal direction. The central body 32 is held in position by structural arms 34 fixed to the outer wall 22 of the nozzle 14.

FIG. 2 is a close-up view of an exhaust nozzle 14 according to the state of the art, as described with reference to FIG. 1. The arrows referenced 36 represent the gas flow stream 20 delimited by the wall 22. outer and central body frustoconical 32. The central body 32 has a proximal portion 38, also designated by the terms "upstream portion", located on the side of the free turbine 12, and a distal portion 40, also designated by the terms "downstream part" located on the other side. side. In the downstream portion 40 of the central body 32 occurs a peeling phenomenon in a zone 42 of detachment, due to a detachment of the gas flow from the surface of the central body 32, resulting in a reduction of the diffusion and the section aerodynamic exhaust in which the exhaust vein circulates.

The invention aims to solve this problem. For this, Figure 3 shows schematically and partially a central body 32 of a nozzle 14 according to a first embodiment of the invention. The central body 32 includes guide means 44 along the longitudinal direction over at least a portion of the length of the central body 32 in the direction of gas flow. The guide means 44 are distributed over at least a portion of the contour of the central body 32, here over the entire contour of the central body 32. Only the upper part of the central body 32 is shown, the lower part being similar because the central body 32 is frustoconical and the guide means 44 are here uniformly distributed over the entire periphery of the central body 32.

The flow of gases is from the upstream portion 38 to the portion 40 of the central body 32. Since the free turbine 12 is in rotation, the flue gas at the outlet of this turbine 12 arriving at the upstream portion 38 does not propagate only in the longitudinal direction but also has a tangential component in the direction of rotation of the turbine 12 FIG. 3 shows the exhaust velocity vectors 46, 50 in the upstream portion 38, said upstream speed vector 46, and in the downstream portion 40, said downstream velocity vector 50 of the central body 32. The vectors 46, 50 each have two components, a longitudinal component in the longitudinal direction, i.e. in the direction of gas flow, and a tangential component in a direction perpendicular to the longitudinal direction, due to the rotation of the turbine 12 free. The upstream velocity vector 46 decomposes into a longitudinal upstream velocity vector 47 and a tangential upstream velocity vector 48, and the downstream velocity vector 50 decomposes into a downstream longitudinal velocity vector 51 and a tangential downstream velocity vector 52.

The guide means 44 allow the reduction of the tangential component of these vectors 46, 50 speed. The downstream velocity vector 50 has indeed a reduced tangential component with respect to the upstream velocity vector 46. The reduction of this tangential component allows the reduction of the aerodynamic detachment by orienting the flow of the gases on the surface of the central body 32 in the longitudinal direction, in which the exhaust gases farther away from the central body 32 flow.

Reducing the tangential component of the velocity vector also has the effect of reducing the exhaust velocity vector standard, i.e., reducing the velocity of the exhaust gas. This reduction in speed causes a reduction in the dynamic pressure, and therefore an increase in the static pressure, as a principle of conservation of the total pressure equal to the sum of the dynamic pressure and the static pressure. Increasing the static pressure and decreasing the dynamic pressure then make it possible to increase the coefficient of static pressure recovery, stated in the preamble, which makes it possible to increase the performance of the escapement 10 and therefore of the turbine engine.

The means 44 for guiding exhaust gases are formed in this embodiment of grooves 54 dug in the central body 32 in the direction of gas flow. The splines 54 are formed on the central body 32 either by boilermaking on a conventional central body or by twist molding of the manufacture of the central body 32. The formation of the splines 54 does not add or very little mass to the central body 32, which makes it possible not to reduce the general performance of the aircraft in which the turbine engine is installed. According to the embodiments of the invention, the mass increase of the central body 32 does not exceed 3%, this mass increase of the internal vein of the primary nozzle can be easily compensated by a reduction in the length of the ejector.

The flutes 54 have certain geometric characteristics which are visible and referenced in FIG. 4, which represents a central body 32 according to the same embodiment as FIG.

The characteristics of the splines 54 are as follows:

the number of splines 54 and their distribution on the contour of the central body 32;

the length L of the splines 54. The splines extending here to the end downstream of the central body 32, this length is also associated with a starting abscissa 0 of the splines 54;

the depth of the grooves, which corresponds to the distance between the part of the grooves 54 furthest from the axis of the central body, that is to say at the level of the spaces between two grooves 54, and the nearest part the axis of the central body 32, that is to say in the groove of the grooves 54. More specifically, the grooves 54 may have a fixed depth over the entire length or a variable depth, between a minimum depth Pmin of side of the upstream portion 38 of the central body 32, at the starting abscissa 0, and a maximum depth Pmax in the downstream portion 40 of the central body 32, at the end thereof;

- The radius of the grooves 54, these being rounded in their hollow. Like the depth, the radius may be fixed or variable along the length of the grooves, a starting radius Rd upstream of the central body 32 at the starting abscissa 0, and an output radius Rs in the downstream part of the central body 32, at the end thereof.

Figures 5 and 7 show two other embodiments of the invention, in which the characteristics of the splines 54 previously stated differ in their values.

FIG. 5 represents a second embodiment where the splines 56 have the following characteristics:

sixteen splines 56 distributed uniformly over the entire contour of the body 32 centrai;

starting depth of 0.5mm, output depth of 15mm; output radius of 6mm;

starting abscissa at half of the central body, a length of grooves 56 equal to half the length of the central body 32.

FIG. 6 represents four curves 60, 61, 62, 63 representing the variations of the static pressure recovery coefficient and of the specific consumption of the nozzle according to the second embodiment, at the outlet of the nozzle and at the exit of the ejector of the exhaust comprising the nozzle.

The curves 60 and 61 represent the static pressure recovery coefficient variations as a function of the power delivered by the turbine engine, respectively at the outlet of the nozzle and at the outlet of the ejector. The static recovery coefficient is thus increased for all the powers delivered.

The curves 62 and 63 represent the variations in the specific fuel consumption as a function of the power delivered by the turbine engine, respectively at the outlet of its nozzle and at the outlet of the ejector. Thus, increasing the coefficient of static pressure recovery leads to a decrease in fuel consumption, especially in high power.

FIG. 7 represents a third embodiment where the grooves 58 have the following characteristics:

twenty splines distributed uniformly over the entire contour of the central body 32;

1.2mm starting depth, 6mm exit depth; output radius of 6mm;

starting abscissa two-thirds of the central body 32 from the end of the upstream portion 38, a length of grooves 58 equal to one third of the length of the central body 32. The measured performances are nevertheless optimal for any starting abscissa between one-half and two-thirds of the central body 32 in this embodiment.

FIG. 8 represents two curves 64, 65, 66, 67 representing the variations of the static pressure recovery coefficient and the specific consumption of the nozzles according to the third embodiment, and at the level of the ejector of the exhaust comprising the nozzle. The curves 64 and 65 represent the variations of static pressure recovery coefficients as a function of the power delivered by the turbine engine, respectively at the outlet of the nozzle and at the outlet of the ejector. The static recovery coefficient is thus increased for all the powers delivered.

The curves 66 and 67 represent the variations in the specific fuel consumption as a function of the power delivered by the turbine engine, respectively at the nozzle and at the level of the ejector. Thus, increasing the static pressure recovery coefficient results in a decrease in fuel consumption. Comparing with FIG. 6, however, it will be noted that the third embodiment is more effective over a large part of the operation of the turbine engine, but less efficient at high power.

The second and third embodiments shown in FIGS. 5 and 7 have the additional advantage of providing an increase in performance without the grooves 56, 58 being present over an excessive length of the central body 32. Indeed, the absence of grooves in the upstream portion 38 of the central body 32, especially in its first half, makes it easy to implant the structural arms 34 holding the central body 32 in a fixed position, as shown in FIG. effect changes thereof and while maintaining optimum performance generated by the splines 56, 58.

The invention is not limited to the embodiments described. In particular, other embodiments of the gas exhaust nozzle are possible, for example by varying in particular the number of grooves, the distribution of these grooves on all or part of the contour of the central body, the starting position of the splines, the starting depth of the splines at this starting position, the splitting output depth, the starting radius and the output radius of the splines.

Claims

Turbomotor gas exhaust nozzle, comprising an outer wall (22) and an inner wall delimiting between them an exhaust gas flow line (20), the inner wall forming a frustoconical central body (32). extending along a direction, said longitudinal direction, characterized in that said central body (32) comprises means (44, 54, 56, 58) for guiding exhaust gases along said longitudinal direction s extending at least partially along said central body.

2. Exhaust nozzle according to claim 1, characterized in that said means for guiding the exhaust gas are distributed over at least a portion of the periphery of said body (32) central.

3. Exhaust nozzle according to claim 2, characterized in that said exhaust gas guiding means are uniformly distributed around the perimeter of said central body,

4. Exhaust nozzle according to one of claims 1 to 3, characterized in that said means (44, 54, 56, 58) for guiding are formed on a distal portion of said body (32) central in the sense of flow of gases, for a distance of between one half and one third of the total length of the central body (32).

5. Exhaust nozzle according to one of claims 1 to 4, characterized in that said means (44, 54, 56, 58) for guiding the exhaust gas are formed of longitudinal grooves (54, 56, 58). .

6. Exhaust nozzle according to claim 5, characterized in that the grooves have a depth which varies between a minimum value, said depth (Pmin) of departure, in a proximal portion of the body (32) central in the direction of gas flow, and a maximum value, said output depth (Pmax), in a distal portion of the body (32) central in the direction of gas flow.

7. exhaust nozzle according to claim 6, characterized in that the depth (Pmin) of departure is between 0.5mm and 1.2mm.

8. Exhaust nozzle according to one of claims 6 or 7, characterized in that the output depth (Pmax) is between 6mm and 15mm.

9. Exhaust nozzle according to one of claims 6 to 8, characterized in that the grooves (54, 56, 58) have a cross section rounded to a radius of curvature which varies between a minimum value, called radius ( Rd), in a proximal portion of the central body (32) in the direction of gas flow, and a maximum value, said output radius (Rs), in a distal portion of the central body (32) according to the direction flow of gases.

10. Exhaust nozzle according to claim 9, characterized in that said grooves (54, 56, 58) have a radius (Rs) output of 6mm,

11. Exhaust nozzle according to one of claims 5 to 10, characterized in that the body (32) comprises central sixteen and twenty splines (44, 54, 56, 58) for guiding the exhaust gas distributed over the circumference of the central body (32).

12. Turbomotor, characterized in that it comprises a gas exhaust nozzle according to one of claims 1 to 11.