BE1024951B1 - DEFROSTING DEVICE FOR DARK AND AXIAL TURBOMACHINE - Google Patents

Abstract

The invention relates to a defrosting device (28) for a turbine engine blade (26), in particular for a turbojet low-pressure compressor. The device (28) comprises a blade which is fixed to a support and which has a first fundamental frequency according to a first eigenmode of deformation when the blade (26) is frost free, and a second fundamental frequency according to the first eigenmode deformation when the dawn (26) is covered with frost. A vibrating excitation system (36) biases the blade (26) in a vibration spectrum comprising the second fundamental frequency of the first natural deformation mode. From then on the frosted dawn (26) comes into resonance and is defrosted thanks to the amplitude of its natural oscillations. A blade defrosting method (26) is also provided.

Description

(30) Priority data:

(73) Holder (s):

SAFRAN AERO BOOSTERS S.A.

4041, HERSTAL (MILMORT)

Belgium (72) Inventor (s):

DE VRIENDT Olivier 4690 BASSENGE Belgium (54) DEFROSTING DEVICE FOR BLADE AND AXIAL TURBOMACHINE, -28 (57) The invention relates to a deicing device HQ, 3 (28) for blade (26) of a turbomachine, in particular for low pressure compressor turbojet engine.

The device (28) comprises a blade which is fixed to a support and which has a first fundamental frequency according to a first natural mode of deformation when the blade (26) is free of frost, and a second fundamental frequency according to the first natural mode deformation when the blade (26) is covered with frost. A vibration excitation system (36) biases the blade (26) according to a vibration spectrum comprising the second fundamental frequency of the first natural mode of deformation. Consequently the frosted dawn (26) enters into resonance and is defrosted thanks to the amplitude of its natural oscillations. A blade defrosting method (26) is also proposed.

BELGIAN INVENTION PATENT

FPS Economy, SMEs, Middle Classes & Energy

Publication number: 1024951 Deposit number: BE2017 / 5045

Intellectual Property Office International Classification: F01D 25/00 F01D 25/02 Date of issue: 08/30/2018

The Minister of the Economy,

Having regard to the Paris Convention of March 20, 1883 for the Protection of Industrial Property;

Considering the law of March 28, 1984 on patents for invention, article 22, for patent applications introduced before September 22, 2014;

Given Title 1 “Patents for invention” of Book XI of the Code of Economic Law, article XI.24, for patent applications introduced from September 22, 2014;

Having regard to the Royal Decree of 2 December 1986 relating to the request, the issue and the maintenance in force of invention patents, article 28;

Given the patent application received by the Intellectual Property Office on 25/01/2017.

Whereas for patent applications falling within the scope of Title 1, Book XI of the Code of Economic Law (hereinafter CDE), in accordance with article XI. 19, §4, paragraph 2, of the CDE, if the patent application has been the subject of a search report mentioning a lack of unity of invention within the meaning of the §ler of article XI.19 cited above and in the event that the applicant does not limit or file a divisional application in accordance with the results of the search report, the granted patent will be limited to the claims for which the search report has been drawn up.

Stopped :

First article. - It is issued to

SAFRAN AERO BOOSTERS S.A., Route de Liers 121, 4041 HERSTAL (MILMORT) Belgium;

represented by

LECOMTE Didier, PO. Box 1623, 1016, LUXEMBOURG;

a Belgian invention patent with a duration of 20 years, subject to the payment of the annual fees referred to in article XI.48, §1 of the Code of Economic Law, for: DEFROST DEVICE FOR VANE AND AXIAL TURBOMACHINE.

INVENTOR (S):

DE VRIENDT Olivier, Rue du Brouck 21, 4690, BASSENGE;

PRIORITY (S):

DIVISION:

divided from the basic application: filing date of the basic application:

Article 2. - This patent is granted without prior examination of the patentability of the invention, without guarantee of the merit of the invention or of the accuracy of the description thereof and at the risk and peril of the applicant (s) ( s).

Brussels, 08/30/2018, By special delegation:

BE2017 / 5045

Description

DEFROST DEVICE FOR BLADE AND AXIAL TURBOMACHINE

Technical area

The invention relates to the field of defrosting a turbomachine blade. More specifically, the invention relates to a device for defrosting a blade by vibration excitation. The invention also relates to an axial turbomachine, in particular an aircraft turbojet or an aircraft turboprop. The invention also provides a method of defrosting a blade.

Prior art

The presence of frost in a turbojet engine degrades its efficiency since the resulting extra thickness disturbs the flow. At the inlet of the compressor, the passage section narrows and limits the maximum possible flow. When ice lines a dawn, the aerodynamic profiles are changed and can no longer guide or deflect the flow as they should.

Document US2016 / 0138419 A1 discloses a turbojet engine comprising a low pressure compressor provided with an inlet structure in the separation nozzle. The inlet structure includes an annular wall with piezoelectric actuators and vanes fitted with other piezoelectric actuators. The piezoelectric actuators are adapted to vibrate the structure according to its natural frequency in order to release it from the frost. However in practice, this defrosting mode remains ineffective.

Summary of the invention

Technical problem

The object of the invention is to solve at least one of the problems posed by the prior art. More specifically, the invention aims to improve the efficiency of a blade de-icing device. The invention also aims to provide a simple, resistant, light, economical, reliable solution,

BE2017 / 5045 easy to produce, convenient to maintain, easy to inspect, and improve performance.

Technical solution

The subject of the invention is a deicing device for a turbomachine blade, in particular for a turbomachine compressor, the device comprising: a support, at least one blade fixed to the support and having a first fundamental frequency according to a first natural mode of deformation when the the blade is free of frost, and a second fundamental frequency according to the first natural mode of deformation when the blade is covered with frost; remarkable in that the blade further comprises a second fundamental frequency according to the first natural mode of deformation when the blade is covered with frost, and in that the device further comprises a system of excitation in vibration of the blade according to a vibration spectrum comprising the second fundamental frequency of the first natural mode of deformation in order to defrost the dawn.

According to advantageous modes of the invention, the device can include one or more of the following characteristics, taken in isolation or according to all possible technical combinations:

The second fundamental frequency is less than the first fundamental frequency.

The second fundamental frequency is greater than the first fundamental frequency.

The second fundamental frequency differs in frequency by at least: 2%, or 5%, or 30% compared to the first fundamental frequency.

The vibration spectrum comprises a first harmonic of the second fundamental frequency, and possibly a second harmonic of the second fundamental frequency.

The spectrum is a frequency range, the first fundamental frequency being outside said range.

The system is suitable for calculating the second fundamental frequency of the dawn, in particular using optical means and / or by vibration excitation.

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BE2017 / 5045 3

The device / that it comprises a module for measuring the vibrations of the blade, said module possibly being integrated into the excitation system in vibration.

The excitation system comprises at least one or more actuators, possibly piezoelectric, arranged in the vane and / or in the support, the said actuator or actuators being adapted to excite the vane in vibration according to the second fundamental frequency.

The support includes an outer ferrule and an inner ferrule to which the blade is attached.

îo - The first natural mode of blade deformation is a bending deformation or a torsion, in particular an axial bending or a torsion along a radial axis respectively.

The second natural frequency is greater than or equal to: 1 kHz, or

10kHz.

- The blade further comprises at least a second natural mode according to which it has a third fundamental frequency when the blade is free of frost and a fourth fundamental frequency when the blade is covered with frost; the vibration spectrum further comprising the fourth fundamental frequency of the second natural mode of deformation in order to defrost the vane.

The blade is a first blade, the device comprising an annular row of identical blades to which the first blade belongs.

The first eigenmode includes one or more deformation nodes.

- The first proper mode comprises the modification of the camber of the aerodynamic profiles and / or the pivoting of aerodynamic profiles with respect to each other.

The or each blade is embedded in the support.

The first fundamental frequency is theoretical and / or measured in the turbomachine; for example at room temperature on the ground. The ambient temperature can be measured at 20 ° C or 25 ° C.

BE2017 / 5045

The second fundamental frequency can be theoretical and / or calculated and / or measured, in particular at an operating temperature. Said operating temperature is at most: 0 ° C, or -20 ° C, or -50 ° C.

In at least one specific mode of deformation, the support, in particular the internal ferrule oscillates, possibly in rotation around the axis of rotation of the turbomachine.

The system is configured to measure the second fundamental frequency of the first natural mode as a function of the thickness and / or the mass of frost covering the blade.

The vibration spectrum is centered on the second fundamental frequency.

The device comprises a module for determining the first eigen mode and or more eigen modes, and possibly their respective fundamental frequencies.

The quotient first frequency / second frequency is different from N or 1 / N; N being an integer.

The invention also relates to a turbomachine, in particular an aircraft turbojet engine, comprising a defrosting device for a blade, remarkable in that the device is in accordance with the invention, the vibration excitation system being possibly configured to excite dawn in phases.

According to an advantageous embodiment of the invention, the turbomachine comprises a low pressure compressor with several annular rows of blades, including an upstream annular row and downstream annular rows, the device equipping the upstream annular row and / or one or more rows downstream annulars.

The subject of the invention is also a method of de-icing a turbomachine blade with a de-icing device, said blade being linked to a support and having a first fundamental frequency according to a first natural mode of deformation when the blade is free of frost and a second fundamental frequency according to the first natural mode of deformation when the blade is covered with frost; the method comprising a step (a) operation of the turbomachine, remarkable in that it further comprises

BE2017 / 5045 a step (c) resonance of the dawn thanks to an excitation system in vibration according to its second fundamental frequency and / or a harmonic in order to defrost it, the device possibly being in accordance with the invention.

According to advantageous modes of the invention, the process can include one or more of the following characteristics, taken in isolation or according to all possible technical combinations:

During step (c) resonance, the blade includes a static mechanical prestress, adding to the variable stresses exerted by the excitation system.

The prestressing includes a mechanical stress in bending, possibly oriented according to the first proper mode of deformation.

The method further comprises a step (b) detection of frost by excitation of the blade according to its second natural frequency and by measurement of its vibrational response to said excitation, the detection of frost possibly triggering step (c) resonance.

The layer of frost covers at least: 5%, or 10% or 50% or 90% of the surface of the blade; and / or one or two sides of the dawn.

The layer of frost has a thickness of at least: 0.10mm, or 0.50mm, or 1mm, or 5mm, or 15mm, and / or a thickness greater than the average thickness of the blade.

In general, the advantageous modes of each object of the invention are also applicable to the other objects of the invention. Each object of the invention can be combined with the other objects, and the objects of the invention can also be combined with the embodiments of the description, which in addition can be combined with one another, according to all possible technical combinations.

Benefits

The invention adapts the vibrations imposed at dawn so as to take into account the presence of frost, and to the overload that it adds. The evolution of the general elasticity of the dawn is also taken into account.

Exciting dawn according to one or more harmonics which are superimposed on the second fundamental frequency modifies the accelerations that follow the surface

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BE2017 / 5045 at dawn. In this way, the ejection force that the frost undergoes increases, the defrost becomes faster. Using harmonic and / or knots improves the treated surface.

The invention also makes it possible to adapt to two scenarios: when the layer of ice forms a thin film with negligible mass and added stiffness; and when the layer of ice becomes massive and changes the stiffness of the dawn. In the first case, the second fundamental frequency should be reduced compared to the first fundamental frequency, and the reverse should be done in the second case.

îo Brief description of the drawings

FIG. 1 represents an axial turbomachine according to the invention.

FIG. 2 is a diagram of a turbomachine compressor according to the invention.

FIG. 3 illustrates the deicing device according to the invention.

FIG. 4 shows the de-icing device at the level of a blade aerodynamic profile according to the invention.

FIG. 5 is a diagram of the defrosting process according to the invention.

Description of the embodiments

In the following description, the terms "internal" and "external" refer to a positioning relative to the axis of rotation of an axial turbomachine.

The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation.

Upstream and downstream are in reference to the main flow direction of the flow in the turbomachine.

Figure 1 shows in a simplified manner an axial turbomachine. In this specific case, it is a double-flow turbojet engine. The turbojet engine 2 comprises a first level of compression, called a low-pressure compressor 4, a second level of compression, called a high-pressure compressor 6, a combustion chamber 8 and one or more levels of turbines 10. In operation, the mechanical power from the turbine 10 transmitted via the central shaft to the rotor 12 sets in motion the two compressors 4 and 6. The latter comprise several rows of rotor blades associated with

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BE2017 / 5045 7 rows of stator vanes. The rotation of the rotor around its axis of rotation 14 thus makes it possible to generate an air flow and to compress it progressively until the inlet of the combustion chamber 8.

An inlet fan commonly designated as a fan or blower 16 is coupled to the rotor 12 and generates an air flow which is divided into a primary flow 18 passing through the various above-mentioned levels of the turbomachine, and into a secondary flow 20 passing through a duct annular (partially shown) along the machine to then join the primary flow at the turbine outlet. The secondary flow can be accelerated so as to generate a useful thrust reaction when flying an aircraft.

Figure 2 is a sectional view of a compressor of an axial turbomachine such as that of Figure 1. The compressor can be a low pressure compressor 4. One can observe a part of the fan 16 and the separation nozzle 22 primary flow 18 and secondary flow 20. The rotor 12 comprises several rows of rotor blades 24, in this case three. It can be a padded monobloc drum, or include dovetail-fixing vanes.

The low pressure compressor 4 comprises several rectifiers, in this case four, which each contain a row of stator vanes 26.

The row of upstream stator vanes 26 is associated with the fan 16. Rows of downstream stator vanes 26 are associated with the rows of rotor vanes 24 to straighten the air flow, so as to convert the speed of the flow into pressure.

The blades of the same row can be identical, optionally each row is formed of identical blades.

The stator vanes 26 extend essentially radially from an outer casing. The casing may be formed from an external ferrule (s) 30, and / or from half-shells. It can be an organic matrix composite. In addition, an internal ferrule 32 can be suspended from the internal ends of the stator vanes 26 of the same row, or from each stator row.

In order to defrost its blades, the turbomachine comprises a vibrating deicing device 28. The device 28 can equip the upstream row, and / or the downstream rows with vanes to defrost them.

Figure 3 sketches the deicing device 28 for blade. The dawn that is here

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BE2017 / 5045 shown is a stator vane 26. However, the device could adapt to a rotor vane, to a fan vane, to a vane at the fan outlet.

The blade 26 is shown from the front, the inner shroud 32 and the outer casing acting as an outer shroud 30 are partially visible around the axis of rotation 14. The blade 26 is partially covered with frost 34 on its underside and on its upper surface. It could become totally so.

When it is bare, that is to say without frost, the blade 26 has at least one specific mode of vibrational deformation, in particular a first specific mode of deformation. Dawn 26 is shown with a continuous line in a rest position, that is to say when it is not stressed in vibration. A dotted line and a mixed line represent two extreme positions of the amplitudes of vibration of the dawn according to the proper mode.

The or each eigenmode has a first fundamental frequency and harmonics which are multiples thereof. The proper mode can be with one or more nodes of deformation. Each first fundamental frequency can be theoretical and adjusted during the design of the blade, in particular by taking into account its mode of embedding in the shell (s) (30; 32).

When the blade 26 is covered with frost 34, its mass changes. The frost 34 may have a localized imbalance, or which completely lines the faces. Therefore, the vibrational response of dawn changes due to the increasing inertia.

When the frost 34 remains thin, it does not really modify the stiffness of the blade according to the proper mode, however the fundamental frequency changes. It can decrease, so that a second fundamental frequency exists; with a frequency lower than that of the first frequency. This second frequency can be theoretical, for example as a function of known cases. It can be measured.

If the frost 34 develops more, it can also increase the stiffness of the blade 26 according to the clean mode. In this case the new fundamental frequency becomes higher than the first frequency.

For example, the second fundamental frequency is greater than or equal to: 15 kHz, or 30 kHz, or 50 kHz, or 100 kHz. It can represent a variation

BE2017 / 5045 with a frequency of at least: 5%, or 50% or 100% compared to the first fundamental frequency.

An excitation system 36 enables the blade 26 to be vibrated so that it returns to resonance. In particular, the excitation system 36 urges the blade 26 according to a spectrum of vibrations, possibly complex. This spectrum comprises at least the second fundamental frequency of the eigen mode, and possibly one or more harmonics which follow. In the present case, the oscillations at the second frequency allow the blade 26 to oscillate laterally; so towards its neighboring blades. Since the radially inner end of the vane vibrates along the circumference, the inner ferrule 32 can oscillate by turning on itself. Its inertia influences the fundamental frequencies and the eigen modes. However, the presence of the internal ferrule is optional.

The purpose of this solicitation is to allow a resonance of the blade 26. This synchronized solicitation makes it possible to maximize the amplitude of the vibrations of the blade 26 as a function of the energy supplied to it. Consequently, the beats of the blade 26 generate accelerations communicated to the frost 34 which tends to peel off because its cohesive force with the blade 26 becomes less than the accelerations undergone.

The defrosting device 28 may comprise a module 38 for measuring the vibrations in the vane. The module 38 makes it possible in particular to calculate the second fundamental frequency. This can be achieved by exciting the blade 38 by gradually varying the excitation frequency, for example from the first fundamental frequency. Thanks to optical means 40 and / or vibration sensors in the dawn, it can be established that a second fundamental frequency has been reached when the dawn enters into resonance.

As a variant or in addition, a specific mode may be taken into account where each radial end of the blade is fixed, for example by urging all the blades of the row according to the second fundamental frequency, but by providing for alternating blades in phase opposition. In the present view, each leading and / or trailing edge describes a sine wave, or a superposition of sine waves.

FIG. 4 represents an aerodynamic profile 42 of the blade. Dawn 26 is

BE2017 / 5045 shown with a solid line in a rest position. Two extreme positions of deformation are represented using a dotted line and a mixed line. The blade 26 is deformed by twisting around a curve grouping the centers of gravity 44 of the profiles 42. The direction of flow is indicated by the primary flow 18 along the axis 14.

Under the action of the excitation system 36 of the defrosting device 28, the blade 26 is deformed according to another clean mode of deformation, in particular a second clean mode. Here, the blade 26 has a third fundamental frequency when the blade 26 is free of frost and a fourth fundamental frequency when the blade 26 is lined with frost 34. The spectrum of vibrations imposed by the excitation system 36 includes the fourth fundamental frequency to release the blade 26 from its frost 34 which disturbs the primary flow 18 around the aerodynamic profile 42. The pulses communicated at the blade 26 tend to detach the frost 34.

In addition, the dawn may have a third natural mode of vibrational deformation, with a fifth fundamental frequency in the absence of frost, and a sixth fundamental frequency in the presence of frost on the dawn. This third mode can include deformations of the profiles 42, the camber of which increases and decreases alternately with respect to an equilibrium position. The excitation system 36 excites dawn in the third mode at the sixth frequency to defrost it.

In the spectrum of deformation imposed on the blade, the first, the second and possibly the third eigen modes can be combined. Advantageously, the spectrum comprises the addition of a vibration according to the second, the fourth and possibly the sixth fundamental frequency according to their respective modes.

Each deformation movement, each component of the vibration spectrum, can be produced by actuators 46 possibly arranged in the blade 26, for example in the middle of its thickness EA. These actuators 46 can be of the piezoelectric type. These can also be used as vibration sensors if necessary. Magnetic actuators (not shown) can be used. Some actuators can be integrated into one of the ferrules forming a support.

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BE2017 / 5045

By analogy, the percentages and frequencies indicated for the first mode can be applied to the subject of the third to the sixth fundamental frequencies of the second and third eigen modes respectively.

FIG. 5 represents a diagram of the blade defrosting process. The dawn may correspond to that described in relation to Figures 2 to 4.

The process can include the following steps carried out in the following order:

(a) operation 100 of the turbomachine; then (b) detection 102 of frost by excitation of the blade according to a broad vibration spectrum îo comprising the second natural frequency and by measurement of its vibratory response to said excitation;

(c) resonance 104 of the dawn thanks to an excitation system in vibration according to the second fundamental frequency and / or a harmonic in order to defrost it.

During steps (a) operation 100 and (b) detection 102, the blade includes a static prestress. This prestress can be exerted by the primary flow when it flows against the dawn. Its dynamic pressure can significantly distort the dawn. Mechanical bending preload can generate bending of the blade along an axis parallel to the axis of rotation of the blade. The direction of the deformation can coincide with that of the first proper mode of deformation. During step (c) resonance 104, the prestress accumulates with the stresses and variable deformations produced by the excitation system.

BE2017 / 5045

Claims (20)

Claims 1. Defrosting device (28) for a blade (26) of a turbomachine (2), in particular for a compressor (4) of a turbomachine, the device (28) comprising: - a support, - At least one blade (26) fixed to the support and having a first fundamental frequency according to a first natural mode of deformation when the blade (26) is free of frost (34), and a second fundamental frequency according to the first natural mode of deformation when the blade (26) is covered with frost (34); characterized in that the blade (26) further comprises a second fundamental frequency according to the first natural mode of deformation when the blade (26) is covered with frost (34), and in that the device (28) comprises in besides a vibration excitation system (36) of the blade according to a vibration spectrum comprising the second fundamental frequency of the first natural mode of deformation in order to defrost the blade (26). 2. Device (28) according to claim 1, characterized in that the second fundamental frequency is lower than the first fundamental frequency. 3. Device (28) according to claim 1, characterized in that the second fundamental frequency is greater than the first fundamental frequency. 4. Device (28) according to one of claims 1 to 3, characterized in that the second fundamental frequency differs in frequency by at least: 2%, or 5%, or 30%, relative to the first fundamental frequency . 5. Device (28) according to one of claims 1 to 4, characterized in that the vibration spectrum comprises a first harmonic of the second fundamental frequency, and possibly a second harmonic of the second fundamental frequency. 2017/5045 BE2017 / 5045 13 6. Device (28) according to one of claims 1 to 5, characterized in that the spectrum is a frequency range, the first fundamental frequency being outside said range. 7. Device (28) according to one of claims 1 to 6, characterized in that the 5 system (36) is suitable for calculating the second fundamental frequency of the blade (26), in particular using optical means and / or by vibration excitation. 8. Device (28) according to one of claims 1 to 7, characterized in that it comprises a measurement module (38) of the vibrations of the blade (26), said measurement module (38) possibly being integrated in the excitation system (36). 9. Device (28) according to one of claims 1 to 8, characterized in that the excitation system (36) comprises at least one or more actuators (46), possibly piezoelectric, arranged in the blade (26) and / or in 15 the support, said actuator (s) (46) being adapted to excite the blade in vibration according to the second fundamental frequency. 10. Device (28) according to one of claims 1 to 9, characterized in that the support comprises an outer shroud (30) and an inner shroud (32) to which the blade (26) is fixed. 20 11. Device (28) according to one of claims 1 to 10, characterized in that the first proper mode of deformation of the blade (26) is a deformation in bending or a torsion, in particular an axial bending or a torsion according to a radial axis respectively. 12. Device (28) according to one of claims 1 to 11, characterized in that 25 the second natural frequency is greater than or equal to: 1 kHz, or 10 kHz. 13. Device (28) according to one of claims 1 to 12, characterized in that the blade (26) further comprises at least a second natural mode in which it has a third fundamental frequency when the blade BE2017 / 5045 is free of frost (34) and a fourth fundamental frequency when the dawn is covered with frost (34); the vibration spectrum further comprising the fourth fundamental frequency of the second natural mode of deformation in order to defrost the vane. 14. Device (28) according to one of claims 1 to 13, characterized in that the blade (26) is a first blade, the device (28) comprising an annular row of identical blades to which the first blade belongs . 15. Turbomachine (2), in particular an aircraft turbojet engine, comprising a device (28) for defrosting a blade, characterized in that the device conforms to one of claims 1 to 14, the excitation system in vibration (36) possibly being configured to excite dawn in phases. 16. Turbomachine (2) according to claim 15, characterized in that it comprises a low pressure compressor (4) with several annular rows of blades (26), including an upstream annular row and downstream annular rows, the device (28) fitted to the upstream annular row and / or one or more downstream annular rows. 17. Method for defrosting a blade (26) of a turbomachine (2) with a deicing device (28), said blade being linked to a support and having a first fundamental frequency according to a first natural mode of deformation when the blade is free of frost (34) and a second fundamental frequency according to the first natural mode of deformation when the blade is covered with frost; the method comprising a step (a) operation (100) of the turbomachine, characterized in that it further comprises a step (c) resonance (104) of the blade (26) by means of a vibration excitation system (36) according to its second fundamental frequency and / or a harmonic in order to defrost it, the device possibly being in accordance with one of claims 1 to 14. 18. Method according to claim 17, characterized in that during step (c) resonance (104), the blade (26) comprises a mechanical prestress 2017/5045 BE2017 / 5045 15 static adding to the variable stresses exerted by the excitation system (36). 19. The method of claim 18, characterized in that the prestressing comprises a mechanical stress in bending, possibly oriented 5 according to the first proper mode of deformation. 20. Method according to one of claims 17 to 19, characterized in that it further comprises a step (b) detection (102) of frost (34) by excitation of the blade (26) according to its second natural frequency and by measuring its vibrational response to said excitation, the detection of frost possibly triggering step (c) resonance (104). BE2017 / 5045 BE2017 / 5045 BE2017 / 5045 BE2017 / 5045 104 2017/5045 BE2017 / 5045 Abridged DEFROSTING SYSTEM FOR BLADE AND AXIAL TURBOMACHINE The invention relates to a deicing device (28) for a blade (26) of a turbomachine, in particular for a low pressure compressor of a turbojet engine. 5 The device (28) comprises a blade which is fixed to a support and which has a first fundamental frequency according to a first natural mode of deformation when the blade (26) is free of frost, and a second fundamental frequency according to the first mode clean of deformation when the blade (26) is covered with frost. A vibration excitation system (36) urges the vane îo (26) according to a vibration spectrum comprising the second fundamental frequency of the first natural mode of deformation. Consequently the frosted dawn (26) enters into resonance and is defrosted thanks to the amplitude of its natural oscillations. A blade defrosting method (26) is also proposed.