Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/30—Fixing blades to rotors; Blade roots ; Blade spacers
  • F01D5/3007—Fixing blades to rotors; Blade roots ; Blade spacers of axial insertion type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
  • F01D21/02—Shutting-down responsive to overspeed
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D21/00—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for
  • F01D21/04—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position
  • F01D21/045—Shutting-down of machines or engines, e.g. in emergency; Regulating, controlling, or safety means not otherwise provided for responsive to undesired position of rotor relative to stator or to breaking-off of a part of the rotor, e.g. indicating such position special arrangements in stators or in rotors dealing with breaking-off of part of rotor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/12—Blades
  • F01D5/14—Form or construction
  • F01D5/147—Construction, i.e. structural features, e.g. of weight-saving hollow blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2220/00—Application
  • F05D2220/30—Application in turbines
  • F05D2220/32—Application in turbines in gas turbines
  • F05D2220/321—Application in turbines in gas turbines for a special turbine stage
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/20—Three-dimensional
  • F05D2250/29—Three-dimensional machined; miscellaneous
  • F05D2250/294—Three-dimensional machined; miscellaneous grooved
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/70—Shape
  • F05D2250/71—Shape curved
  • F05D2250/712—Shape curved concave
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2260/00—Function
  • F05D2260/94—Functionality given by mechanical stress related aspects such as low cycle fatigue [LCF] of high cycle fatigue [HCF]
  • F05D2260/941—Functionality given by mechanical stress related aspects such as low cycle fatigue [LCF] of high cycle fatigue [HCF] particularly aimed at mechanical or thermal stress reduction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2270/00—Control
  • F05D2270/01—Purpose of the control system
  • F05D2270/02—Purpose of the control system to control rotational speed (n)
  • F05D2270/021—Purpose of the control system to control rotational speed (n) to prevent overspeed

Definitions

• the present invention relates to the turbine blades of a turbomachine and, in particular, to a stilt arrangement of a turbine blade.
• the vane stilt is a supporting portion of the vane blade that extends radially between a lower attachment portion of the vane called a "fir tree" and a vane platform.
• the invention relates to the turbine blades of a free-turbine turbomachine.
• the invention also relates to a turbomachine comprising such blades.
• a free-turbine turbomachine comprises a gas generator 1, comprising at least one compressor which comprises one or more compression stages 2, a combustion chamber 3, and a turbine in which the Hot gases under pressure from the combustion chamber expand and in which the kinetic and thermal energy of the gases is transformed into mechanical energy to drive in rotation a shaft which connects the turbine to the compressor, in order also to drive the compressor.
• a turbine 4 called a free turbine, which comprises one or more turbine stages, is arranged downstream of the turbine of the gas generator 1, and mechanically decoupled from the latter. The free turbine 4 is driven in rotation by the gases from the gas generator 1.
• the free turbine In free turbine engines, used for example, but not exclusively, in helicopter propulsion units, the free turbine is mechanically independent of the helicopter rotor, a reduction gear being interposed between the shaft line and the rotor main .
• the turbine may be in a overspeed situation due to the disappearance of the resistive torque applied to the turbine blades.
• the stilt 4 of the blade which extends between the base of the fir tree 6 and a platform which forms the base of a profile aerodynamic 5 or blade of the vane, has a concave leading edge 7 making it possible to form in the stilt a frangible zone of minimum section capable of allowing the vane to detach from the disc from a threshold speed protection.
• FIG. 4 shows the radial stress which is applied in the stanchion of the blade under the effect of thermomechanical forces.
• the creation of a concave leading edge 7 locally reducing the cross section of the stilt generates the appearance of a zone Z of maximum stress on the leading edge, in the corners of the reduced cross section. .
• This increase in maximum stress is accompanied by the appearance of an additional moment due to the off-center of the airfoil from the minimum section of the neck of the stilt.
• the invention aims to provide a turbine blade provided with a frangible section making it possible to adjust the breaking speed value of the blade without increasing the maximum stress in the blade.
• the object of the invention is therefore a turbine blade comprising a blade and a root, the root comprising a stilt having lateral flanks with a curvilinear profile, said stilt comprising a frangible zone adapted to undergo a rupture of the stilt if radial forces greater than a threshold are exerted on the blade, in particular centrifugal forces during a state of overspeed of the turbine.
• the frangible zone comprises at least one oblong frangibility cavity formed on at least one of the lateral flanks of the stilt, said oblong cavity extending in an axial direction of the stilt along a longitudinal axis parallel to or included in a plane of minimum section in which there is a minimum cross section of the stilt.
• This cavity thus makes it possible to weaken the frangible section of the stilt by increasing the average stress exerted in the neck of the stilt, without significantly increasing the maximum stress generated locally under the action of thermomechanical forces. It therefore makes it possible to optimize the setting of the limiting speed from which the blades break.
• the blade is mounted on a disc, the longitudinal axis of the or each oblong cavity being included in a frangibility plane located at a distance from an axis of rotation of the disc between h + 0.06h and h- 0.06h, preferably between h + 0.04h and h-0.04h, h denoting the distance between the axis of rotation and the plane of minimum section, the plane of frangibility and the plane of minimum section being parallel between them and the axis of rotation.
• the frangible zone of the stilt is formed by a concave zone of the stilt made on a front face and on at least one of the lateral flanks of the stilt, the most deep of the oblong cavity being intersected by the minimum section plane of the stilt.
• the maximum depth of the oblong cavity is between 9% and 35% of the width of P stilt, preferably between 10% and 25% of the width of P stilt, considered at the deepest point of the cavity.
• the maximum depth of the oblong cavity is between 10% and 25% of its length, preferably between 14% and 20% of the length of the cavity.
• the stilt comprises an oblong frangibility cavity, the distance between the barycenter of the cavities and the projection of the center of gravity of the vane on the plane of minimum section is between 0 and 20% of the axial length of the stilt, of preferably between 0 and 15% of said width of P stilts.
• the oblong cavity has a curvilinear cross section.
• the oblong cavity has a cross section in an arc of a circle.
• the object of the invention is also a turbomachine turbine, comprising a rotor comprising at least one disk and a set of turbine blades mounted on the disc, each blade being a blade as defined above.
• the longitudinal axis of the or each oblong cavity of each blade is included in a frangibility plane located at a distance from an axis of rotation of the disc between h + 0.06h and h-0.06h, preferably between h + 0.04h and h-0.04h, h denoting the distance between the axis of rotation of the disc and the minimum section plane, the frangibility plane and the minimum section plane being parallel to each other and to l 'rotation axis.
• FIG 1 illustrates the general structure of a free turbine gas turbine according to the state of the art
• FIG 3 are respectively front and perspective views of a blade according to the state of the art
• FIG 4 shows the stress field exerted on the dawn stilt in Figures 2 and 3;
• FIG 6 are respectively front and perspective views of a blade according to the invention.
• FIG 7 is a detail view on a larger scale of the blade of Figure 6;
• FIG 8 is a cross sectional view of the vane stilt of Figures 5 and 6 at the deepest point of the cavities;
• FIG 9 shows the blade of Figures 5 and 6 mounted on a rotor disc
• FIG 10 is a perspective view of Fig 8.
• FIG 1 1 shows the stress field exerted on the blade stilt of Figures 5 and 6.
• This blade 10 comprises a blade 11, a fir tree root 12 intended for fixing the blade to a rotor disc, by engagement of the root 12 in a housing also called a "cell" of corresponding shape made in the disc, a stilt 13 extending the base of the tree 12 and a platform 14.
• the fir tree base extends along a longitudinal axis, which in a manner known per se can form an angle with the axis of rotation AA 'of the turbine disk, in order to increase the contact length between the fir tree base and the disc.
• the axis of the tree base once the dawn has risen on the disc extends in the direction of the corresponding cell in the disc.
• the cells of a free turbine disk can each be provided more or less obliquely in a plane tangential to the disk, relative to the axial direction of the disk. In other words, an angle in a plane tangential to the disc is formed between the direction of a cell and the axis of the disc.
• the stilt 13 has a curvilinear shape.
• the blade 10 furthermore comprises oblong cavities 17, that is to say having a longitudinal dimension greater than their lateral dimension, which are formed in the lateral sides of the stilt 13.
• Each cavity 17 extends along an axis longitudinal X-X 'parallel or substantially parallel to the longitudinal axis of the fir tree base.
• the X-X ’axis of each cavity can therefore, like the axis of the tree base, form an angle with the axis of rotation A-A’ of the turbine disk, shown in Figure 9.
• Each cavity constitutes a pocket locally reducing the cross section of the neck of the stilt in order to weaken the frangible zone of the stilt and to adjust the overspeed limit speed from which the blade detaches from the disc.
• each lateral flank of the stilt has at least one cavity.
• Each lateral flank here comprises a cavity, L the stilt comprising a pair of cavities formed symmetrically.
• each cavity has a concave cross section, considered perpendicular to the longitudinal axis of the cavity, preferably a round cross section, without ridge.
• the radius R of the cavity is preferably between 10 and 25% of the length of the cavity, advantageously between 14% and 20% of the length of the cavity.
• Its depth, which may for example correspond to the radius of the cavity, is advantageously between 9% and 35% of the minimum width Imin of the stilt, considered at the level of the deepest point of the cavity (FIG. 8).
• the depth of the cavity is preferably between 10% and 25% of the width Imin of the stilt.
• each cavity is made in the concave surface of a lateral flank of the stilt and extends parallel to a longitudinal plane P which coincides with the minimum width of the stilt neck.
• the axis X-X' of each cavity is included in a plane, hereinafter referred to as the frangibility plane, which either coincides with the plane P, or is parallel to the plane P and is located slightly above or above the plane P. More precisely, the plane of frangibility is located at a distance from the axis of rotation A-A 'of the disc between h-0.06h and h + 0.06h, preferably between h-0.04h and h + 0.04h. Moreover, if the stilt includes a pair of cavities formed symmetrically, the frangibility plane includes the two respective X-X ’axes of the two cavities.
• the distance d between the barycenter B of all the cavities and the radial projection of the center of gravity G of the blade on the cutting plane is comprised between 0 and 20% of the axial length L of the stilt at the location of its minimum section, preferably between 0 and 15% of this length L
• the axial length L is measured in a direction parallel to the axis of the fir tree base, which can advantageously form an angle with the axis of rotation A-A ′ of the disk of the turbine. This angle is for example between 5 ° and 20 °.
• the length of the cavities is for example about 40% of the total length of the base of the fir tree at the location of the minimum section and their depth is about 20% of the width of the neck.
• Each lateral flank of the stilt may include any number of cavities in order to locally reduce the cross section of the stilt and thereby adjust the limit speed of rotation of the blades.
• the cavities are devoid of sharp angles so as not to induce a concentration of stresses greater than those already induced by the concave shape made in the anterior face, on the leading edge side.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=68138342

Family Applications (1)

Country Status (7)

Families Citing this family (1)

Family Cites Families (7)

• 2019
  • 2019-05-27 FR FR1905588A patent/FR3096727B1/fr active Active
• 2020
  • 2020-05-18 EP EP20726420.1A patent/EP3976931B1/de active Active
  • 2020-05-18 CN CN202080040046.XA patent/CN113891983B/zh active Active
  • 2020-05-18 PL PL20726420.1T patent/PL3976931T3/pl unknown
  • 2020-05-18 CA CA3139054A patent/CA3139054A1/fr active Pending
  • 2020-05-18 US US17/614,039 patent/US11846206B2/en active Active
  • 2020-05-18 WO PCT/EP2020/063781 patent/WO2020239490A1/fr unknown

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