RU2784237C2 - Gas turbine engine with coaxial screws - Google Patents

Abstract

FIELD: engine building.

SUBSTANCE: present invention relates to a gas turbine engine with coaxial screws, such as overturn or non-overturn screws. The gas turbine engine with a longitudinal axis contains two coaxial outer screws, respectively input and output. At the same time, at least some of blades of the input screw contain at least one inner air duct for air circulation, communicating, from one side, with air intake holes for air selection in boundary layers of blades and communicating, from the other side, on its radially outer end, with air outlets. In this case, air intake holes are open at a level of inlets on blade backs. At the same time, inlets of air intake holes are located radially only in zone (H1), which is from 10% to 45% of radial size (H2) of blades, measured above and starting from a radial height of blades, on which a tangent of a front edge is orthogonal to the longitudinal axis. In this case, inlets of air intake holes are located only in zone (L1), which is from 0% to 30% of local chord (L2) of blades, measured at a height of the mentioned inlets and starting from front edges of blades.

EFFECT: invention provides reduction in noise with interaction of swirl generated by an input screw with an output screw.

12 cl, 9 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to a gas turbine engine with coaxial propellers, such as shrouded or non-shrouded propellers (in English "open rotor" or "unducted fan").

BACKGROUND OF THE INVENTION

The prior art is represented in particular by EP-A1-2090765, FR-A2-2866931 and US-A-2156133.

Currently, in the field of engines for civil aviation, there is an increasing tendency to reduce specific consumption (CS), to reduce noise and NOx emissions. One of the technical solutions adopted by the engine designers is to increase the bypass ratio between the primary flow and the secondary flow. Various architectures are provided for this, such as “UHBR” motors in English (Ultra High Bypass Ratio) and twin propeller motors (“CROR” from Counter Rotating Open-Rotor in English or “USF” from Unducted Single Fan in English ), as a possible replacement for modern gas turbine engines for medium-range flights.

In the case of an open rotor gas turbine engine, the nacelle that directs the secondary flow to produce the main thrust on a classic gas turbine engine is removed. In this case, the propulsion system includes an inlet screw that entrains the flow, and an outlet screw that is stationary for the USF motor and rotates for the CROR motor, while the outlet screw allows the flow to be straightened. The traction efficiency of the engine is increased by energy recovery during rotation. The diameter of the engine propellers is also significantly increased in order to ensure the suction of a large amount of air and increase traction efficiency. However, in the absence of a nacelle, the main disadvantage of this open rotor architecture is the noise impact and, in particular, the noise generated by the propellers during the various interactions between the propellers and components associated with the installation of the engine on the aircraft.

The main source of noise is associated with the interaction of the turbulence produced by the input screw with the output screw. The apex swirl occurs when the swirl at the end of the blade merges with the swirl of the leading edge, which develops starting from the central convexity of the back of the inlet blade.

The solution to eliminate this noise, called "clipping", is to reduce the outer diameter of the outlet screw so that the turbulence generated by the input screw passes outside the outlet screw, in particular, outside the cylinder formed by the outlet screw during rotation, and does not interact with the latter. However, this solution is not entirely satisfactory, as it leads to a decrease in the thrust produced by the output screw and, consequently, to a deterioration in the performance of the gas turbine engine. It would be possible to increase the load on the output screw to compensate for the reduction in its diameter, but this screw would then become more mechanically difficult and produce more noise of its own.

The invention aims to offer a simple, effective and economical solution to this problem.

DISCLOSURE OF THE INVENTION

The object of the invention is a gas turbine engine with a longitudinal axis, containing two coaxial external screws, respectively, the input and output.

In the claimed gas turbine engine, at least some of the inlet propeller blades contain at least one internal air duct for air circulation, which communicates, on the one hand, with air sampling openings for air sampling in the boundary layers of the blades and, on the other hand, communicates on its radially outer at the end with air outlets extending at the level of the openings of the holes on the backs of the blades, while the air intake holes are located radially in a zone constituting from 10% to 45% of the radial size of the blades and measured above and starting from the radial height of the blades, at which the tangent of the leading edge is orthogonal to the longitudinal axis, while the inlets of the air sampling holes are in the zone of from 0% to 30%, preferably from 10% to 30% of the local chord of the blades and measured at the height of said inlets and starting from the leading edges of the blades.

Thus, the particular arrangement of the inlets of the air intakes makes it possible to reduce the source of intense swirl that develops at the level of the inlet propeller by deflecting it before it joins the swirl at the tip of the blades.

The air intake openings are located radially below the air outlet openings and are connected to the latter through essentially radial air ducts made inside the blades. The ducts may have other arrangements, for example they may zigzag through the blades. The air intakes are thus at radii or radial distances from the motor axis smaller than the radial distances of the outlets, so that a sufficient pressure difference is created between the inlet and outlet of the internal air ducts of the blades. During operation, centrifugal forces and pressure differences between the bleed areas and the air outlet are sufficient to direct the bleed air through the vane ducts to the outlets. The air escaping from these holes is expelled outside the inlet propeller blades and allows the fusion of the low intensity vortices created by the inlet propeller to be broken.

Thus, the invention does not require downsizing of the input and output screws, which may have substantially the same outside diameter.

Air is taken off at the backs of the blades, where the turbulences in the boundary layers are greatest. In a variant, the air intake openings can extend onto the troughs of the blades and even simultaneously onto the troughs and backs of the blades. The air pressure on the troughs of the blades is higher than on their backs. However, as a rule, the boundary layers on the troughs are more harmless. Therefore, air sampling at the troughs of the blades is not always necessary.

Preferably, the inlets of the air sampling holes are located only in said areas H1 and L1 of the inlet propeller blades.

Said at least one internal air circulation duct may be substantially radial.

Air intake openings can have an elongated or elongated section.

The air outlets may extend outside the blades at the level of the outlets of the holes, while said outlets of the holes are in the zone constituting from 0% to 60% (preferably from 0% to 15%) of the local chord of the blades and measured at the height of the said outlets and starting from the front edges of the blades, that is, in the area where the pressure is lower than in the inlet. Air outlets may extend outside the blades at the level of the outlets of the holes, while said outlets are located radially in the zone H3, which is from 85% to 100% of the radial size of the blades and measured from the legs of the blades.

Preferably, said outlets are located only in said region H3 of the radial dimension of the blades.

Preferably, the air outlets are open on the backs of the blades.

The outlet air holes can be oriented towards the top of the blades so that in the axial section the angle between the radial axis of the blades and the direction of the air outlet is from 0° to 90°.

The outlet air holes can be oriented towards the back of the blades so that in the radial section the angle between the radial axis of the blades and the direction of the air outlet is from 0° to 90°.

The input and output screws may have substantially the same outside diameter.

The input and output propellers may be non-hooded and may be counter-rotating propellers.

The input and output propellers may or may not be hooded propellers.

DESCRIPTION OF FIGURES

The invention and its other details, features and advantages will be better understood from the following description, presented by way of non-limiting example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic axial sectional view of a gas turbine engine with unhooded propellers.

Fig. 2 is a partial schematic perspective view of the input propeller of a prior art gas turbine engine with unhooded propellers.

Fig. 3 is a schematic view of a conventional gas turbine engine with unhooded propellers.

Fig. 4 is a schematic axial sectional view of the inlet propeller blade of the claimed gas turbine engine with unhooded propellers.

Fig. 5 is a sectional view along line A-A of FIG. four.

Fig. 6 is a schematic view of a turbine inlet propeller blade from the leading edge without a contour and with an air bleed circuit in accordance with the invention.

Fig. 7 is a schematic view of a turbine inlet propeller blade from the back without a circuit and with an air bleed circuit in accordance with the invention.

Fig. 8 is a schematic axial view of a blade provided for understanding the invention.

Fig. 9 is a graph showing the amount of deflection along the radial axis of the blade.

DETAILED DESCRIPTION

In FIG. 1 shows a gas turbine engine 10 with unhooded propellers (in English “open rotor” or “unducted fan”), which contains, from inlet to outlet in the direction of gas flow inside the gas turbine engine, a compressor 12, an annular combustion chamber 14, an inlet high-pressure turbine 16 and two low-pressure outlet turbines 18, 20 which are counter-rotating turbines, that is, they rotate in opposite directions about the longitudinal axis X of the gas turbine engine.

Each of the output turbines 18, 20 is connected in rotation with an external screw 22, 24, which is located radially outside the nacelle 26 of the gas turbine engine, and this nacelle 26 is essentially cylindrical and is located along the axis X around the compressor 12, the combustion chamber 14 and the turbines 16, 18 and 20.

The air stream 29 entering the compressor 12 is compressed, then mixed with fuel and burned in the combustion chamber 14, after which the combustion gases pass into the turbines, driving the propellers 22, 24, which provide the bulk of the thrust generated by the gas turbine engine. Combustion gases (arrows 31) exit the turbines and are then expelled through nozzle 30, increasing this thrust.

The screws 22, 24 are arranged coaxially one after the other. As is known, each of these propellers 22, 24 comprises a plurality of blades uniformly distributed about the X-axis of the gas turbine engine, each blade being substantially radially disposed and comprising an upstream leading edge, an downstream trailing edge, a radially inner end forming the blade root, and a radially outer end forming the top of the blade.

The inlet screw 22 is substantially the same diameter as the outlet screw 24 so that the two screws produce the same thrust during operation and all air flow between the inlet rotor blades also passes between the outlet rotor blades.

In FIG. 2 is a partial schematic perspective view of the inlet screw 22 of a known gas turbine engine, and also shows the change in flow lines on the blades of this screw. Flow lines 32, 34, 36 run between the propeller blades and more or less follow the profile of these blades, starting from the leading edges 38 to the trailing edges 40 of these blades.

The flow lines 32 passing through the radially inner end portions of the blades are substantially parallel to each other. On the other hand, the flow lines 34, 36 passing through the radially outer end portions tend to approach each other, this phenomenon becoming more intense as they approach the tops 42 of the blades. The flow lines 36, which run at the level of the tops of the blades, twist on each other and form vortices 44 which fall on the blades of the output screw 24 (FIG. 3), resulting in a very high noise impact.

The object of the invention is to reduce the intensity of the swirl at the source, which is formed at the level of the flow lines 34 of the inlet propeller blades 22, by sucking this swirl before it joins the apical swirl formed by the flow lines 36. The objective of the invention is also to reduce the intensity of the vertex whirl.

In the framework of the invention, it is proposed to perform suction or air intake holes in the blades of the input screw 22 for air sampling in the boundary layers of the blades in the central zones of the backs close to the leading edges 38, while the bleed air is then removed outside the input screw 22, destroying the structure of turbulences 42 of lesser intensity, which are formed at the tops of the blades.

As shown in FIG. 4 and 5, the inlet propeller blades 122 comprise at least one internal duct 150 for circulating air, which communicates, on the one hand, with air intake openings 152 passing through the side walls of the blades and exiting onto the backs 156 of these blades, and, on the other hand , with bleed air outlets 158 that are open near the tops 142 of the blades. The air intake holes 152 allow swirl to be sucked in as soon as it begins to form, in particular from 50% to 60% of the radial size (span) H2 of the blades. Thus, the swirl generated by the inlet propeller blades 122 will have less energy and a smaller diameter, and hence the cross section of the swirl acting on the outlet propeller blade will be reduced. This can significantly reduce interaction noise.

In order for all intake openings 152 to be active, that is, to absorb swirl well, a positive pressure differential must be present between the inlet of openings 152 and where they open. To do this, each air intake hole 152 is made in the form of a channel connected to an internal air duct 150, which passes inside the blade and exits near its top 142, for example, near the leading edge, and on the back 156, where the pressure is lower than at the level of the inlets 152a of the holes 152 .

The solution for the implementation of systems "air intake holes 152 - duct 150" is the use of so-called consumable fibers. They are 3D woven fibers, typically carbon fibers, bonded together with resin, which are then chemically dissolved to make said kits. It is also possible to provide for the vanes 148 to be made by weaving around small diameter tubes of a material similar to that of the consumable fibers in order to dissolve them in the same chemical manner. The diameter D of these elements is calculated depending on the suction force required to reduce the swirl intensity at the leading edge.

The internal ducts 150, for example, one per blade, are radially elongated and extend substantially parallel to the radial shape of the blades 148.

The inlets 152a of the intake openings 152 are radially located in a zone H1 that is 10% to 40% of the blade height H2, i.e. 0.1 H2 to 0.45 H2 (FIGS. 7 and 9) and measured above zero bend. Zero bend is defined as the radial height of the blade at which the leading edge tangent is radial, i.e. parallel to the longitudinal axis X of the gas turbine engine. The outlets of the air outlets 158 are preferably located in the zone H3, which is between 85% and 100% of the blade height and measured from the blade root.

In order to increase the suction efficiency, the optimum differential pressure must be maintained. To this end, the inlets 152a of the air sampling openings 152 are preferably located axially in a zone L1 comprising from 0% to 30% and in particular from 10% to 30% of the local chord L2, and measured from the leading edge 138. Local chord should be understood the chord measured at the radial height of the inlet 152a in question. Thus, for a given hole inlet height 152a, the chord L2 is the shortest path/straight that connects the leading edge 138 to the trailing edge 140. Similarly, the exits of the air outlets 158 are preferably axially in the region of 0% to 60% (preferably 0% to 15%) local chord and measured from the leading edge. The 0% zone corresponds to the outlets of the air outlets 158 located on the leading edge.

Preferably, the air intake holes 152a are located only in the region H1 and L1 of the blade 148, and the air outlet holes 158 are only in the region H3, in order to effectively reduce the vortices of the leading edge of the inlet vane before they are connected with the vortex in the tip of the outlet vane.

The leading edge swirl is formed at the level of the leading edge 138, as its name indicates, and tends to move away from it as it moves along the height of the blade. The goal is to absorb/reduce the energy of this vortex and move the flow towards the top of the blade in a direction that follows the curve of the blade.

The removal of the flow should also help to reduce the intensity of the swirl at the tip of the blade and the radial removal of its position against the direction of its flow. As shown in FIG. 6 and 7, in configuration 1 (no bleed) and configuration 2 (with bleed), tip vortex 144 has less energy in configuration 2 than vortex 44 in configuration 1, and hence creates less loss, which improves the efficiency of the gas turbine engine. In addition, the intensity of the swirl 144 is less in configuration 2, and the swirl 144 is radially spaced in configuration 2, which avoids the effect of the swirl 144 on the exit blade. This eliminates the need to increase the radius of the output blade and gain performance gains or reduce the interaction noise between the input propeller and the output propeller.

The air removal angle α ₁ , α ₂ at the tip of the blade is preferably oriented towards the trailing edge 140 of the blade 148 and also directed upwards of the blade 148. The direction of air removal is indicated by arrows 160 (FIGS. 6 and 7).

Thus, this bleed angle α ₁ , α ₂ with respect to the longitudinal axis X of the gas turbine engine, or equivalently with respect to the radial axis Y, is between 0° and 90°. As shown in FIG. 7, the offset angle α ₂ is about 50° with respect to the longitudinal axis X. As shown in FIG. 6, the venting preferably takes place on the side of the back 156. The angle α ₁ between the radial axis Y of the blade and the direction of venting can be between 0° and 90°. In FIG. 6 it is approximately 40°.

Thus, the invention provides a number of advantages:

- noise reduction of the leading edge vortex interaction: acoustic gain,

- noise reduction of the interaction of the swirl of the end of the blade: acoustic gain,

- reduction of losses from the swirl of the end of the blade: a gain in the performance of a gas turbine engine.

The claimed system reduces the boundary layer, which is formed at half the span on the back of the inlet blade, by making suction holes in the area from 10% to 40% of the blade height above zero bend and near the leading edge from 10% to 30% of the chord. This makes it possible to reduce the swirl at its source at the level of the central convexity of the blade. Air outlets are preferably open on the back of the inlet blades near the leading edges and tips of the blades, which makes it possible to reduce the intensity of the tip swirl as close as possible to the place where it is formed.

The invention provides the following advantages:

- reducing the energy of the vertex vortex, thanks to the holes that are open as close as possible to the place where the vertex vortices are formed, at the level of the leading edge of the inlet blade,

- reduction of flow separation on the back of the inlet blade, thanks to the suction holes made in the blade,

- reduction of interaction noise at low speed points by reducing the turbulence that is formed at the level of the central convexity of the blade, due to the suction of the boundary layer on the back at this blade span. The intensity of the tip swirl also decreases due to airflow at the tip of the blade.

In the present description, the inlet and outlet propellers of a gas turbine engine are non-hooded and counter-rotating in a gas turbine engine. However, the invention is not limited to this configuration and also applies to gas turbine engines containing both counter-rotating and non-contra-rotating capped input and output propellers.

Claims (12)

1. A gas turbine engine with a longitudinal axis (X), containing two coaxial external screws (122), respectively, input (122) and output (24), characterized in that at least some of the blades (148) of the input screw (122) contain at least one internal air duct (150) for air circulation, communicating on one side with air intake holes (152) for air sampling in the boundary layers of the blades (148) and communicating on the other side at its radially outer end with air outlet holes (158) , while the air sampling holes (152) are open at the level of the inlets (152a) of the holes on the backs (156) of the blades (148), while the inlets (152a) of the air sampling holes are located radially only in the zone (H1), which is from 10% to 45% radial size (H2) of the blades (148) and measured above and starting from the radial height of the blades, on which the tangent of the leading edge (138) is orthogonal to the longitudinal axis (X), while the inlets (152a) of the air intake the holes are located only in the zone (L1), which is from 0% to 30% of the local chord (L2) of the blades (148) and measured at the height of the said inlets (152a) and starting from the leading edges (138) of the blades (148). 2. Gas turbine engine according to claim 1, characterized in that said at least one internal air circulation duct (150) is essentially radial. 3. Gas turbine engine according to claim. 1 or 2, characterized in that the air intake holes (152) have an elongated or elongated section. 4. Gas turbine engine according to one of paragraphs. 1-3, characterized in that the outlet air holes (158) are open outside the blades (148) at the level of the outlets of the holes, while the said outlets of the holes are in the zone constituting from 0% to 60% of the local chord of the blades and measured at the height of the said outlets and starting from the leading edges (138) of the blades (148). 5. Gas turbine engine according to one of paragraphs. 1-4, characterized in that the outlet air holes (158) are open outside the blades (148) at the level of the outlets of the holes, while said outlets are radially located in the zone (H3) comprising from 85% to 100% of the radial size (H2) of the blades (148) and measured from the feet of the blades. 6. Gas turbine engine according to claim 5, characterized in that said outlet air holes (158) are located only in said zone (H3) of the radial size of the blades (148). 7. Gas turbine engine according to one of paragraphs. 1-6, characterized in that the air outlets (158) are open on the backs (152) of the blades (148). 8. Gas turbine engine according to claim 7, characterized in that the outlet air holes (158) are oriented towards the tip of the blades (148) so that in the axial section, the angle (α ₂ ) between the radial axis (Y) of the blades and the air outlet direction ranged from 0° to 90°. 9. Gas turbine engine according to claim 7 or 8, characterized in that the air outlets (158) are oriented towards the back (156) of the blades (148) so that in a radial section, the angle (α ₁ ) between the radial axis (Y) blades (148) and the direction of air outlet ranged from 0° to 90°. 10. Gas turbine engine according to one of paragraphs. 1-9, characterized in that the input and output screws (122) have essentially the same outer diameter. 11. Gas turbine engine according to one of paragraphs. 1-10, characterized in that the input and output screws (122) are non-hooded and are counter-rotating screws. 12. Gas turbine engine according to one of paragraphs. 1-11, characterized in that the input and output screws (122) are capped and are or are not counter-rotating screws.

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