Method for supplying electric power to an ultrasonic nacelle de-icing and anti-icing

Abstract

A method for de-icing or anti-icing an aircraft portion having at least one piezoelectric element fastened on the inner face of the aircraft portion includes, during a design phase of the aircraft portion, placing the piezoelectric element on an area of the aircraft portion to determine frequencies of resonance and increased dynamic coupling, and during the de-icing or anti-icing of the aircraft portion, the same piezoelectric element is excited according to the natural frequencies of the area.

Claims

1. A method for de-icing or anti-icing an aircraft portion by at least one of a first piezoelectric element fastened on an inner face of the aircraft portion and a second piezoelectric element located in a vicinity of the first piezoelectric element, the method comprising: during a design phase of the aircraft portion, placing the first piezoelectric element on an area of the aircraft portion to determine frequencies of resonance and dynamic coupling; during the de-icing or anti-icing of the aircraft portion, exciting the first piezoelectric element according to natural frequencies of the area of the aircraft portion; determining that the de-icing is operational when an electrical level detected by the second piezoelectric element is within a defined range of an excitation level of the first piezoelectric element; and exciting the second piezoelectric element in addition to the first piezoelectric element in response to the electrical level of the second piezoelectric being outside the defined range of the excitation level of the first piezoelectric element.

2. The method according to claim 1, wherein the operation of the first piezoelectric element is checked by measuring impedance of the first piezoelectric element and comparing it with a nominal impedance of the first piezoelectric element, by analyzing an impedance drift, or a combination thereof.

3. The method according to claim 1 further comprising: identifying presence of frost based on successive measurements of dynamic damping of the first piezoelectric element by a spectrum analyzer that scans the frequency and the quality of the electro-mechanical coupling of the first piezoelectric element with the aircraft portion.

4. The method according to claim 1 further comprising exciting the first piezoelectric element in several frequency ranges, including at least one frequency range between 10 kHz and 200 kHz, simultaneously or successively, depending on the result of the step of determining frequencies of the resonance and dynamic coupling during the design phase.

5. The method according to claim 1, wherein the first piezoelectric element is excited intermittently, either with a timing or from a measurement of the variation in impedance of the first piezoelectric element.

6. The method according to claim 1, wherein: the first piezoelectric element and the second piezoelectric element comprise a first set of piezoelectric elements; at least another set of piezoelectric elements is provided at the aircraft portion; and the excitation of the first set of piezoelectric elements is switched to the other set piezoelectric elements depending on a frost thickness to inhibit de-icing areas where the frost thickness is less than a thickness threshold.

7. A system for de-icing or anti-icing an aircraft portion, the system comprising: at least one piezoelectric element, the at least one piezoelectric element includes a first piezoelectric element configured to be fastened inside an area of the aircraft portion and a second piezoelectric element located in the vicinity of the first piezoelectric element; an excitation circuit comprising a signal generator, an amplifier, an analyzer to analyze electrical spectrum produced by the first piezoelectric element, a natural frequency detector, a memory comparator and a frequency setpoint generator; and a control box electrical coupled to the excitation circuit and configured to: excite the first piezoelectric element according to natural frequencies of the area of the aircraft portion during the de-icing or anti-icing of the aircraft portion; determine that the de-icing is operational when an electrical level detected by the second piezoelectric element is within a defined range of an excitation level of the first piezoelectric element; and excite the second piezoelectric element in addition to the first piezoelectric element in response to the electrical level of the second piezoelectric being outside the defined range of the excitation level of the first piezoelectric element.

8. The system according to claim 7, wherein the excitation circuit comprises a battery or a super capacitor.

9. The system according to claim 7, wherein the excitation circuit comprises means for matching impedance with the impedance of the first piezoelectric element.

10. The system according to claim 7 comprising the first piezoelectric element and the second piezoelectric element, and the excitation circuit is configured to multiplex power and monitor the first piezoelectric element and the second piezoelectric element.

Description

DRAWINGS

(1) In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

(2) FIG. 1 is a schematic view of an air inlet lip portion of an aircraft turbojet engine nacelle, equipped with a piezoelectric element connected to a control box according to the teachings of the present disclosure;

(3) FIG. 2 is a diagram of the architecture of control of the piezoelectric element of FIG. 1; and

(4) FIG. 3 is a view similar to that of FIG. 1, of a variant of the present disclosure comprising a passive piezoelectric element disposed next to an active piezoelectric element.

(5) The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

(6) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

(7) By referring to FIG. 1, an air inlet lip 1 (also referred to herein as a carrier structure) of an aircraft turbojet engine nacelle is schematically represented, on the inner face 3 thereof a piezoelectric element 5, connected by an electrical wiring 7 to a control box 9, is glued.

(8) This control box can receive orders 11 from the pilot of the aircraft, send 13 information to this pilot, and be electrically powered 15 by a circuit installed on board the plane.

(9) More specifically, the architecture of control of the piezoelectric element 5 can be visualized in FIG. 2.

(10) This architecture comprises a frequency setpoint generator 16, an electrical frequency generator 17, an amplifier 19 of these signals, a variable inductance 21 allowing matching the impedance of the electrical excitation with that of the piezoelectric element 5.

(11) The members 16, 17, 19, 21 allow generating a sinusoidal electrical excitation of the piezoelectric element 5 through the excitation circuit 7.

(12) A frequency spectrum analyzer 23 allows measuring, through a feedback circuit 24, the effective vibration frequencies of the piezoelectric element 5.

(13) An electronic unit 25 (also referred to herein as a natural frequency detector) allows detecting the vibration amplitude peaks of the piezoelectric element 5, thus indicating that the wall of the air inlet 1 is vibrating according to any of these natural frequencies.

(14) A memory comparator 27 is interposed between the natural frequency detector 25 and the setpoint generator 16.

(15) The principle of operation of the present disclosure is as follows.

(16) During the design of the air inlet 1, a plurality of piezoelectric elements such as the piezoelectric element 5 are placed on the inner face 3 of this air inlet 1, at places allowing carrying out an electrotechnical coupling (also referred to herein as a dynamic coupling), that is to say at places allowing increasing the vibration amplitude of the inner face 3 under the effect of the vibration of the piezoelectric elements 5 for a given excitation current.

(17) Subsequently, in operation, at the start of a de-icing or anti-icing sequence, one starts by checking the integrity of the piezoelectric elements by measuring their impedance, and by comparing it to a nominal value or to a previously recorded value: any significant deviation relative to nominal/previously recorded value (e.g., impedance drift) may reveal an issue with the gluing or integrity of the concerned piezoelectric element.

(18) Electrical pulses are sent to each piezoelectric element 5 by means of the signal generator 17, and the damping of these signals is examined by means of the spectrum analyzer 23. In this manner, frost may be identified by successive measurements of the dynamic damping of a piezoelectric element 5 by the spectrum analyzer 23 by scanning the frequency and quality of the electro-mechanical coupling of the piezoelectric element 5 and a portion of the aircraft.

(19) A gray or polyfrequency noise can advantageously be used to cover a frequency band containing natural frequencies of the carrier structure 1.

(20) When a significant damping is detected, it means that frost is forming on the outer face 29 of the air inlet 1.

(21) An excitation current of each piezoelectric element 5 is then sent, by means of the signal generator 17 and the associated amplifier 19 thereof, according to frequencies set by the setpoint generator 16.

(22) Preferably, these excitation frequencies comprise, on the one hand, a range of low frequencies, typically around 40 kHz, and on the other hand, a range of high frequencies, typically around 200 kHz. In a variation, the range of low frequencies may be around 10 kHz.

(23) Depending on the signals collected by the spectrum analyzer 23, these excitation frequencies are varied until obtaining a resonance phenomenon of the piezoelectric element 5, detected by the natural frequency detection member 25.

(24) This resonance of each piezoelectric element 5 allows obtaining a maximum vibration amplitude of the concerned area of the air inlet lip 1, and thus a fractionation, then a peel off of the frost layer formed on the outer face 29 of this air inlet lip.

(25) It should be noted that the low frequency range allows carrying out the operation of fracturing the ice, and that the high frequency range allows carrying out the operation of peeling off this ice layer.

(26) It should be noted that the excitation currents in the two aforementioned frequency ranges can be sent simultaneously or alternately to the piezoelectric elements.

(27) In one form, it is possible to provide a fixed time delay or a function of the measurement of the variation in impedance of the piezoelectric elements, allowing them to be excited only when the frost layer reaches a sufficient thickness (i.e., thickness threshold), typically between 0.5 and 0.6 mm: indeed, it has been noted empirically that de-icing only reached its full effectiveness when such a thickness was reached. In this manner, the measurement of the variation may be taken intermittently.

(28) A significant improvement can be made by providing that the electronic circuit for exciting the piezoelectric elements 5 comprises means for matching the impedance with that of the piezoelectric elements thereof.

(29) Indeed, these piezoelectric elements have a behavior similar to that of capacitors in the electrical excitation circuit: this induces a significant reactive power and a bad cos φ, leading to a loss of energy.

(30) The impedance matching means can comprise a fixed inductance (coil) or else, in a more sophisticated manner, an inductance which is variable depending on the excitation frequency: the latter solution could be suitable in particular for resorbing the very thick frost layers strongly disturbing the resonance frequencies of the wall to be de-iced.

(31) As can be understood in the light of the above, the present disclosure allows improving the amplitude of the vibrations of the area to be de-iced, for a given electrical excitation: this allows expelling the frost with a lower consumption of electrical energy, by a purely dynamic process.

(32) In practice, it is observed that there is practically no passage of the frost in the liquid state, such that there is practically no electrical energy dissipated in heat: the disappearance of the frost is caused almost exclusively by setting the wall on which it was formed into vibratory movement.

(33) According to a variant represented in FIG. 3, it is provided that next to each active piezoelectric element 5, that is to say biased by electrical excitations in accordance with the above, there is a passive piezoelectric element 5′, these two piezoelectric elements being respectively connected by electric cables 7 and 7′ to a comparator 30, itself connected respectively by electric excitation cable 31 and return cable 33 to a control box 35.

(34) In this particular configuration, the passive piezoelectric element 5′ measures the effective vibrations caused by the active piezoelectric element 5, and detects a possible malfunction. That is, when an electrical level detected by the passive piezoelectric element is within a defined range (i.e., close to) of an excitation level of the active piezoelectric element, the de-icing process is determined to be operational. On the other hand, in response to the electrical level of the passive piezoelectric being outside the defined range of the excitation level of the first piezoelectric element, the passive piezoelectric element is excited to become an active piezoelectric element 5′ in addition to the other piezoelectric element 5.

(35) In the case of such a malfunction, an electrical excitation current can then be sent into the piezoelectric element 5′, so as to transform it into an active element, and to add its vibratory contribution to that of the piezoelectric element 5.

(36) In a more economical configuration, it can be considered that there are not, on the one hand, active piezoelectric elements and on the other hand passive piezoelectric elements, but that all piezoelectric elements are matched (that is to say operate in pairs) each piezoelectric element of a pair can operate alternately as an active or a passive element.

(37) According to a power saving logic, it should be noted that it is possible to consider a multiplexing by areas of the piezoelectric elements, allowing exciting only the piezoelectric elements located in an area where the frost layer has reached a sufficient thickness (see above: typically between 0.5 and 0.6 mm) in order to increase the electrical energy consumption.

(38) This strategy allows carrying out an actual power saving by increasing the ratio of frost reforming time to de-icing time.

(39) Still according to an electric power saving logic, it is also possible to consider an electrical circuit comprising a battery or a super capacitor, recharged during the time of reconstitution of the frost layer, and discharged during the implementation of the defrost electrical excitation, thus allowing increasing the peak voltage and therefore increasing the deflections of the piezoelectric elements.

(40) Of course, the present disclosure is in no way limited to the forms which are described and represented.

(41) Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

(42) As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

(43) The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.