RU2792505C2 - Gas turbine engine blade made according to the rule of deflection of the blade profile with a large flutter margin - Google Patents

Abstract

FIELD: gas turbine engines.

SUBSTANCE: invention relates to a rotor blade of a gas turbine engine, containing a plurality of sections of the blade stacked on top of each other along the Z axis between the root part of the blade and the end part of the blade, defining between themselves the height of the blade, while each section of the blade contains a leading edge (21), a trailing edge ( 22), pressure side (19) and back side (18), a chord (25) determined by the length of the chord line, which is the section connecting the leading edge (1) and the trailing edge (2), and the maximum profile deflection (28), determined by the maximum the length of the section perpendicular to the chord line and connecting the point of the chord line and the point of the bend line formed by all points located at an equal distance from the back side (18) and the pressure side (19) in the section, while according to the invention, the ratio between the maximum deflection of the profile and the chord at half the height of the blade is from 25% to 40% of the ratio between the maximum deflection of the profile and the chord at the root of the blade, and the ratio between the maximum profile bend and chord at the end of the blade is from 25% to 40% of the ratio between the maximum deflection of the profile and the chord at the root of the blade.

EFFECT: invention is aimed at increasing the flutter margin without increasing the weight of the blade.

11 cl, 6 dwg

Description

The field of technology to which the invention relates

The invention relates to the field of gas turbine engine blades and, in particular, to the field of gas turbine engine rotor blades.

In particular, the invention is intended for use in fans located inside a turbojet or gas turbine engine.

State of the art

The gas turbine engine includes at least one bladed wheel, such as a fan, which has a plurality of blades arranged radially around a central axis, such as a disk.

Such a paddle wheel forms either a rotor, if we are talking about a movable paddle wheel or a disk made in one piece with the blades, or a stator.

The blades can be considered as protrusions relative to the solid ring. Two adjacent vanes and an annulus form an airflow passage.

The proximal end of each scapula relative to the central axis is usually referred to as the root of the scapula. In particular, the root part of the blade in this case is the part of the blade located above the ring.

The distal end is commonly referred to as the tip of the scapula. The distance between the root and tip of the blade is known as the height of the blade.

Between the root and tip of the blade, the blade can be theoretically represented as a set of sections or airfoils perpendicular to the radial Z axis.

The blade is a complex part to manufacture, as it is associated with the aerodynamic, mechanical and acoustical aspects of the blade wheel and the gas turbine engine at the same time.

When designing a blade and a blade wheel, it is necessary to take into account simultaneously aerodynamic characteristics, mechanical strength and reduction in weight, noise and cost.

The design must guarantee a minimum service life of the blade and the disc on which the blades are attached.

The design must guarantee a minimum vibration resistance of the impeller, i.e. sufficient vibration resistance, or an acceptable level of vibration to ensure mechanical strength.

The paddle wheel must have foreign body ingress strength or blade loss strength, that is, the resistance of the paddle wheel in situations where the blade is partially or completely separated from the disk.

When designing the blade and blade wheel, the flutter phenomenon should be taken into account.

Flutter is an aeromechanical phenomenon associated with the relative movement of air in relation to the design of the blades and the blade wheel. Flutter is a self-oscillation process whereby a change in the motion of a solid structure results in a change in fluid flow, and a change in fluid flow creates forces acting on the solid structure. Flutter can quickly build up and lead to fan blade failure and even engine damage.

Flutter is closely related to the design profile, so it is difficult to eliminate and even limit the flutter phenomenon once it has been detected during fan operation.

It remains possible to exclude some operating areas to limit the risks associated with flutter, but this inevitably entails a reduction in the flight conditions in which the fan can operate.

US 2018/0100399 A1 presents a method for shaping a turbine rotor blade with flutter.

Thus, there is a need for a blade and paddle wheel in which the flutter-prone working area is as far away from the nominal working area as possible, that is, a need for a blade and paddle wheel that has as much flutter margin as possible.

Disclosure of the essence of the invention

The general object of the invention is to overcome the disadvantages inherent in known blades and fans.

In particular, the invention aims to provide a solution that improves the flutter margin.

The invention also aims to provide a solution that increases the flutter margin without increasing the weight of the blade.

In the framework of the present invention, the problem is solved, thanks to the rotor blade of a gas turbine engine, containing a leading edge, a trailing edge, a trough and a back, in which:

- the ratio between the maximum profile deflection and the chord at half the blade height is from 25% to 45% of the ratio between the maximum profile deflection and the chord at the root of the blade,

- the ratio between the maximum profile deflection and the chord at the end of the blade is from 25% to 40% of the ratio between the maximum profile deflection and the chord at the root of the blade.

Such a device is preferably supplemented with the various following features alone or in combination:

- the ratio between the maximum profile deflection and the chord at half of the blade is from 30% to 35% and preferably equals about one third of the ratio between the maximum profile deflection and the chord at the root of the blade;

- the ratio between the maximum profile deflection and the chord at the end of the blade is from 30% to 35% and is preferably equal to about a third of the ratio between the maximum deflection of the profile and the chord at the root of the blade;

- the ratio between the maximum deflection of the profile and the chord at the root of the blade is from 10% to 20% and preferably from 14% to 17%,

- the ratio between the maximum deflection of the profile and the chord at half the height of the blade is from 4% to 7%, preferably from 4.7% to 5.7%,

- the change in height of the ratio between the maximum deflection of the profile and the chord of each section of the blade is between:

- the first function defined

- the first section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 14%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and

- the second section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 4.7%, and

- the second function defined

- the third section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 17%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and

- the fourth section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 5.7%.

- the change in height of the ratio between the maximum profile deflection and the chord is a function determined by two sections of a straight line, on the one hand, between the root part and half the height of the blade, on the other hand, between half the height and the end part of the blade,

- the ratio between the maximum profile deflection and the chord of the blade section decreases when the section height increases from the root of the blade to half the height of the blade, then maintains an almost constant value of the ratio between the maximum deflection of the profile and the chord between half the height of the blade and the tip of the blade.

The subject of the invention is also a gas turbine engine fan comprising a plurality of rotor blades as described above.

The subject of the invention is also a gas turbine engine which contains such a fan.

Brief description of the drawings

Other features and advantages of the invention will become more apparent from the following description, given by way of illustrative and non-limiting example only, with reference to the accompanying drawings, in which:

in fig. 1 schematically shows a gas turbine engine, a longitudinal sectional view;

in fig. 2 is a schematic perspective view of a fan rotor of a gas turbine engine;

in fig. 3 schematically shows a part of the rotor shown in FIG. 2, perspective view;

in fig. 4 schematically shows a section of a blade;

in fig. 5 is a graph showing the change, between the blade root and the blade tip, in the ratio of maximum airfoil deflection to blade chord in accordance with the invention;

in fig. 6 schematically shows the operating lines of a fan according to an embodiment of the invention and a known fan.

Implementation of the invention

Gas turbine engine - General

In FIG. 1 schematically shows a gas turbine engine, in particular a bypass axial turbojet 1. The shown turbojet 1 comprises a fan 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6 and a low pressure turbine 7.

The fan 2 and the low pressure compressor 3 are connected to the low pressure turbine 7 via the first transmission shaft 9, while the high pressure compressor 4 and the high pressure turbine 6 are connected via the second transmission shaft 10.

During operation, the air flow compressed by the low and high pressure compressors 3 and 4 supports combustion in the combustion chamber 5, while the expansion of the combustion gases drives the high and low pressure turbines 6, 7. Through the shafts 9 and 10, the turbines 6, 7 drive the fan 2 and the compressors 3, 4. The air blown by the fan 2 and the gaseous products of combustion leaving the turbojet 1 through a jet nozzle (not shown) at the outlet of the turbines 6, 7, creating a jet thrust acting on the turbojet 1 and through it on a vehicle or aircraft such as an aircraft (not shown).

Each compressor 3, 4 and each turbine 6, 7 of the turbojet 1 comprises a plurality of stages, each stage being formed by a stationary paddle wheel or stator and a rotating paddle wheel or rotor.

In FIG. 2 schematically shows a rotor 11 of a fan of a gas turbine engine. This rotor 11 comprises a plurality of blades 12 disposed radially about the axis of rotation A of the rotor 11, which is substantially parallel to the general direction of flow of the working fluid through the turbojet 1.

The blades 12 may be separate parts from the rest of the rotor and may be connected to it by known means of fastening, such as pin or herringbone fasteners.

In FIG. 3 is a schematic, detailed perspective view of the rotor shown in FIG. 2. Each blade 12 has a spatial coordinate system with three orthogonal axes X, Y and Z.

The X axis runs parallel to the rotation axis A of the rotor 11, the Y axis is tangent to the direction of rotation R of the blade 12 about the rotation axis A, and the Z axis is a radial axis in the direction passing through the rotation axis A.

Each blade 12 comprises a blade root 13 and a blade end 14 separated by a blade height h in the direction of the radial axis Z.

Between the root part 13 of the blade and the end part 14 of the blade, the blade 12 can be theoretically represented as a set of sections or airfoils 15 in planes perpendicular to the radial axis Z.

A turbine engine rotor blade can be described as having a plurality of blade sections stacked on top of each other along the Z axis between the blade root and the blade tip defining the blade height h between them. Such a plane P is shown in Fig. 3 and 4.

The blade 12 includes a leading edge 16 in the inlet direction, a trailing edge 17 in the outlet direction, a back 18 and a trough 19.

Each blade section can be described as containing a leading edge and a trailing edge.

In a compressor or fan rotor, the direction of rotation R during normal operation is such that each blade 12 moves in the direction of its trough 19.

In FIG. 4 schematically shows a section 15 of a blade with a chord line 25 and a bend line 27.

The chord line 25 is a section, that is, a straight line segment, connecting the leading edge 16 and the trailing edge 17 in this section 15.

In the present text, the term "chord" used separately is used to denote the length of the section corresponding to the line of the chord, that is, the distance between these two most distant points.

The fold line 27 is a curved line corresponding to the midline between the curved line of the back 18 and the curved line of the trough 19 in said section 15. In particular, the fold line is formed by all points equidistant from the back 18 and from the trough 19. Distance from a particular point to the back (or to the trough) in this case is defined as the minimum distance between a particular point and the point of the back (or trough).

In this FIG. 4 double arrows also show:

- the maximum thickness 26 of the section (the maximum distance between the back 18 and the trough 19) in the direction perpendicular to the chord line,

- the maximum distance or maximum deflection of the profile 28 between the chord 25 and the bend line 27; the maximum deflection of the profile corresponds to the maximum length of the section perpendicular to the chord line and connecting the point of the chord line and the point of the bend line;

- center of gravity CG of the blade section, which is the barycenter of mass of the blade section. The position of the center of gravity is determined in the plane of the section relative to the Z axis, that is, the coordinates along the X and Y axes in the specified section.

Profile maximum deflection rule

The values of the maximum deflection of the profile of the blades vary depending on the height of the section, which corresponds to them at the height of the blade.

The inventors have found that special rules for maximum profile deflection provide a much better flutter margin.

In particular, this applies to the case when the following relations are satisfied:

- the ratio between the maximum profile deflection and the chord at half the blade height is from 25% to 40% of the ratio between the maximum profile deflection and the chord at the root of the blade,

- the ratio between the maximum profile deflection and the chord at the end of the blade is from 25% to 40% of the ratio between the maximum profile deflection and the chord at the root of the blade.

The best margin is also achieved if the ratio between the maximum profile deflection and the chord at half the height of the blade is between 30% and 35% and preferably equal to about one third of the ratio between the maximum profile deflection and the chord at the root of the blade. "Equal to about one third" in this case means "equal to one third plus or minus one percent."

The ratio between maximum airfoil deflection and blade tip chord can also be between 30% and 35%, and is preferably about one third of the ratio between maximum airfoil deflection and blade root chord.

In particular, the maximum profile deflection rule allows you to check other characteristics that also contribute to increasing the flutter margin, for example:

The ratio between the maximum profile deflection and the chord at the root of the blade is 10% to 20% and preferably 14% to 17%.

The ratio between the maximum profile deflection and the chord at half the blade height is 4% to 7%, preferably 4.7% to 5.7%.

The ratio between the maximum profile deflection and the chord at the end of the blade is 4% to 7%, preferably 4.7% to 5.7%.

These characteristics make it possible, in particular, to obtain such a change in the ratio between the maximum profile deflection and the chord, at which there is a strong decrease in the ratio between the maximum profile deflection and the chord from the root of the blade to half the height of the blade, then an almost constant value of the ratio between the maximum profile deflection and chord between half the height of the scapula and the tip of the scapula.

In a variant, the blade may also comply with the proposed rule for the maximum deflection of the profile in the form of two-sided estimates of the value:

The relationship between the maximum profile deflection and the chord at 0% of the blade height is between the values of r and s.

The relationship between the maximum profile deflection and the chord at 50% of the blade height is between the values of t and u.

The relationship between the maximum profile deflection and the chord at 100% of the blade height is between the values of v and w.

In this sense, the maximum profile deflection rule is represented in the graph in FIG. 5, where the value of the ratio between the maximum profile deflection and the chord is given on the abscissa, while the height of the blade section is shown on the y-axis, with 0% corresponding to the point at the root of the blade, and 100% corresponding to the tip of the blade. The value of 50% of the blade height is in the zone of half of the blade height. In the present text, the half-height zone of the scapula corresponds to the height interval between 45% of the height and 55% of the height of the scapula.

In FIG. 5, the maximum profile deflection rule is represented as a solid curve 30 in this graph. Curve 30 is a graphical representation of the change in height of the relationship between the maximum deflection of the profile and the chord as a function of height.

In FIG. 5, the six limits r, s, t, u, v, and w of the relationship between the maximum profile deflection and the chord are shown on the x-axis, and according to these relationships, the various height percentages associated with them are shown on the y-axis.

r may be from 17% to 20% and preferably from 17% to 18%;

s may be from 10% to 14% and preferably from 13% to 14%;

t may be from 5.7% to 7% and preferably from 5.7% to 6%;

u can be from 4% to 4.7% and preferably from 4.5% to 4.7%;

v may be from 5.7% to 7% and preferably from 5.7% to 6%;

w may be from 4% to 4.7% and preferably from 4.5% to 4.7%.

Curve 30 in the form of a solid line is enclosed between two limit curves 31 and 32, which are two piecewise affine curves (curves formed by line segments or segments of straight lines).

Curve 31 (dash-dotted line) in this case is formed by two halves of a straight line:

- one of them passes between a point corresponding to a chord value of r for a height of 0% and a point with a chord value of t for a height of 50%,

- the other passes between the specified point with a chord value of t for a height of 50% and a point corresponding to a chord value of v for a height of 100%.

Curve 32 (dashed) is formed

- half a straight line between a point with a chord value of s for a height of 0% and a point corresponding to a chord value of u for a height of 50%,

- half of the straight line between the specified point corresponding to the chord value of u for a height of 50% and the point with a chord value of w for a height of 100%.

The gap between the two curves 31, 32 forms a corridor in which there is a graph corresponding to the rule of maximum deflection of the profile.

The proposed rules for the maximum deflection of the profile correspond to the blade, the shape of which in its upper part approaches the shape of a flat plate. This feature allows you to increase the flutter margin.

More generally, the maximum profile deflection rule allows you to check other characteristics that also contribute to increasing the flutter margin. For example, the rule of maximum blade profile deflection depending on its height may correspond to the change in height of the ratio between the maximum profile deflection and the chord of each section of the blade and may be between

- the first function defined

- the first section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 14%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and

- the second section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 4.7%, and

- the second function defined

- the third section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 17%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and

- the fourth section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 5.7%.

Curve 30, which is a graphical representation of the change in height of the relationship between the maximum deflection of the profile and the chord, is enclosed between the two graphical representations of the functions defined above.

In particular, the graph corresponding to the rule of maximum profile deflection can vary along two sections of a straight line, on the one hand, between the root part and half the height of the blade, on the other hand, between half the height and the end part of the blade.

Accordingly, the change in height of the ratio between the maximum profile deflection and the chord can be a function determined by two sections of a straight line, on the one hand, between the root part and half the height of the blade, on the other hand, between half the height and the end part of the blade.

The graph may also correspond to the relationship between the maximum profile deflection and the chord of the blade section, which decreases as the section height increases.

In particular, the graph may correspond to a relationship between the maximum airfoil deflection and the chord of the blade section, which decreases sharply as the sectional height increases from the root of the blade to half the height of the blade, then remains almost constant between half the height of the blade and the tip of the blade.

Working lines of a fan of a gas turbine engine

Shown in FIG. The 6 fan lines show schematically the compression ratio as a function of the flow rate.

Curves A1, A2, A3, A4 and A5 correspond to five engine modes, that is, five engine speeds, for blades and a fan from a known technical solution. In this mode, the flight conditions determine the position on the curve or the operating point of the engine, that is, a pair of flow rates and compression ratios. Ideally, the operating point of the engine is close to curve C, which is the rated work curve.

Curve A10 is the boundary of the flutter zone in the same known solution. Engine operating points located on curves A1, A2, A3, A4 or A5 and to the left of curve A10 correspond to a strong flutter phenomenon.

The flutter margin can be defined as the distance A11 between curve C and curve A10.

Curve B10 shows the boundary of the flutter zone of the corresponding engine. Flutter margin can be defined as the distance B11 between curve B10 and curve C, which is the nominal work curve.

Since the distance B11 exceeds the distance A11, this indicates an increase in the flutter margin compared to the known solution.

The proposed rules for the maximum deflection of the blade profile correspond to the blade, the shape of which approaches the shape of a flat plate in its upper part.

A flat plate corresponds to movements containing a strong bending component and a weak torsion component.

The advantage of the invention is an increase in flutter margin without compromising the mechanical behavior of the blade or the aerodynamic characteristics of the blade. In particular, the flex-torsion bond can be reduced without the need to increase the weight of the blade.

Claims (19)

1. A rotor blade of a gas turbine engine, containing a plurality of sections of the blade stacked on top of each other along the Z axis between the root part of the blade and the end part of the blade, defining between themselves the height of the blade, while each section of the blade contains a leading edge (21), a trailing edge (22 ), trough (19) and back (18), chord (25) determined by the length of the chord line, which is the section connecting the leading edge (1) and the trailing edge (2), and the maximum profile deflection (28), determined by the maximum length a section perpendicular to the chord line and connecting the point of the chord line and the point of the bend line, formed by all points located at an equal distance from the back (18) and trough (19) in section, characterized in that: - the ratio between the maximum profile deflection and the chord at half the blade height is from 25% to 40% of the ratio between the maximum profile deflection and the chord at the root of the blade, - the ratio between the maximum profile deflection and the chord at the end of the blade is from 25% to 40% of the ratio between the maximum profile deflection and the chord at the root of the blade. 2. A gas turbine rotor blade according to claim 1, wherein the ratio between the maximum airfoil deflection and the chord at half of the blade is between 30% and 35%, and is preferably about one third of the ratio between the maximum airfoil deflection and the chord at the root of the blade. 3. The gas turbine rotor blade according to claim 1 or 2, in which the ratio between the maximum profile deflection and the chord at the end of the blade is from 30% to 35% and is preferably equal to about a third of the ratio between the maximum profile deflection and the chord at the root of the blade. 4. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-3, in which the ratio between the maximum profile deflection and the chord at the root of the blade is from 10% to 20% and preferably from 14% to 17%. 5. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-4, in which the ratio between the maximum profile deflection and the chord at half the height of the blade is from 4% to 7%, preferably from 4.7% to 5.7%. 6. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-5, in which the ratio between the maximum deflection of the profile and the chord at the end of the blade is from 4% to 7%, preferably from 4.7% to 5.7%. 7. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-6, in which the change in height of the ratio between the maximum deflection of the profile and the chord of each section of the blade is between: - the first piecewise affine function defined by - the first section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 14%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and - the second section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 4.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 4.7%, - the second piecewise affine function defined by - the third section of the straight line, determined by the ratio between the maximum profile deflection and the chord at the root of the blade, equal to 17%, and the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and - the fourth section of the straight line, determined by the ratio between the maximum profile deflection and the chord at half the height of the blade, equal to 5.7%, and the ratio between the maximum profile deflection and the chord at the end of the blade, equal to 5.7%. 8. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-7, in which the change in height of the ratio between the maximum profile deflection and the chord is a piecewise affine function determined by two sections of a straight line: between the root part and half the height of the blade, on the one hand, and between half the height and the end part of the blade, on the other sides. 9. The rotor blade of a gas turbine engine according to any one of paragraphs. 1-8, in which the ratio between the maximum profile deflection and the chord of the blade section decreases as the section height increases from the root of the blade to half the height of the blade, then maintains a nearly constant value of the ratio between the maximum profile deflection and the chord between half the height of the blade and the tip of the blade . 10. The fan of a gas turbine engine containing a plurality of rotor blades according to any one of paragraphs. 1-9. 11. Gas turbine engine, characterized in that it contains a fan according to claim 10.

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