FR2887520A1 - Jet aircraft engine nacelle has air intake de-icing and anti-icing system created by resistive heating elements embedded in electrical insulating material - Google Patents

Abstract

The air intake (2) lip (3) and tube (4) de-icing and anti-icing system (6a, 6b, 6c, 6d) consists of at least one set of resistive heating elements embedded in an electrical insulating material in the form of a mat within the air intake. The mat can be in two sections inside the air intake lip and in the joining zone (7c) between the lip and the first acoustic attenuation panel (5) of the engine nacelle tube.

Description

DEGIVING SYSTEM WITH NETWORKS OF RESISTIVE ELEMENTS SEGREGUES

  The present invention relates to a de-icing system with segregated resistive element networks particularly applicable to the deicing of aircraft engine nacelles.

  It is known to make aircraft nacelles, whose inner duct surrounds a fan, comprising a tubular air inlet provided with a lip and a fan casing provided with a first internal tubular acoustic attenuation piece, for which a tubular transition portion connects the air inlet to the fan casing.

  Defrosting of the air inlet and the lip is traditionally done by supplying, at the air inlet, hot air leaving the reactor through tubings or passages arranged in the thickness of the nacelle.

  A technical problem stems from the fact that the hot air supplied is, under certain flight conditions, at very high temperature (up to 600 ° C.) and because the tubular sound attenuation part or parts made with composite materials are not compatible with such temperatures.

  De-icing is particularly necessary when descending the aircraft and especially during long finals during which the engines are idling over a long period. In such cases the temperature of the air in the hot air supply ducts is low and a large airflow is required.

  This dimensioning implies that, conversely, in the case where the external temperature is high and the engine in the thrust phase, if the defrost air flow control valve is open the air reaches the above-mentioned high temperatures. This is particularly the case when the valve is locked in the open position to allow a flight in a case of failure of the control system of the valve.

  Reducing the air temperature in the phases where excessive heat is to be avoided is very complex because, in the prior art, the hot air defrosting systems must be sized to allow defrosting of the engine in the phases where it rotates in idling and making a device to cool the air in special circumstances would require a complex apparatus (heat exchanger, valve, regulator and other elements) voluminous and heavy.

  Also, in the prior art, it has been preferred to move the heat-sensitive acoustic attenuation portion away from the de-iced portion and thereby the transition tubular portion includes a junction zone between the air intake and the fan casing devoid of defrosting means so as to move the tubular portion provided with acoustic attenuation means of the heated portion.

  This construction raises in particular two problems, the first is that an annular section of the air intake is devoid of acoustic attenuation material which decreases the efficiency of these noise reduction means, the second is that this The same annular section is devoid of deicing means and therefore remains potentially sensitive to ice accumulation.

  The purpose of the deicing system of the present invention is to allow a close-up and even overlap between the acoustic attenuation zones and the de-iced zones, and furthermore provides a reduction in engine head losses, given that for a civil aircraft engine usual power the hot air anti-icing system of the prior art takes a power of the order of 60 to 80kW on the motor power without real means of regulation or limitation.

  In addition, the pneumatic system of the prior art makes it possible to anti-ice but not defrost in a simple and easily implemented manner while the system of the present invention makes it possible to de-ice particular zones by temporarily sending a power necessary to this defrosting, the power consumed being adapted according to the anti-icing and defrosting modes chosen.

  In this context, the deicing means are electrical means and the system is redundant to allow to keep sufficient defrost in case of failure of one or more elements of the system.

  Also, the invention provides a de-icing system characterized in that it comprises de-icing means constituted by at least one network of heating resistive elements embedded in an insulating material, at least two series of resistive elements being segregated so as to to realize two segregated networks integrated in the thickness of a panel to defrost.

  The deicing means are advantageously constituted by a belt 10 incorporating heating resistors.

  More particularly, each resistive element is spaced apart from adjacent elements by a distance sufficient to provide electrical insulation between the elements and, advantageously, at least some of the resistive elements of a segregated network are connected in parallel.

  The invention further relates to segmenting the structure into a succession of de-icing sectors, controlling a succession of resistive networks arranged in the de-icing sectors by at least one control circuit adapted to supply said networks separately.

  In addition to the increased operating flexibility afforded by the system according to the invention, such a system is particularly suitable for enabling de-icing of air inlet zones of aircraft nacelles provided with acoustic insulation means made of composite materials. because such a system does not subject its environment to high temperatures even in the case of degraded mode operation.

  Other characteristics and advantages of the invention will be better understood on reading the following description of a nonlimiting exemplary embodiment of the invention with reference to the drawings which show: in FIG. 1: an overall view an aircraft engine nacelle in partial section; in FIG. 2: a diagrammatic sectional view of a front part of a nacelle according to the prior art; in Figure 3: a schematic sectional view of a nacelle front portion according to a first embodiment of the invention; in Figure 4: a schematic sectional view of a nacelle front portion according to a first embodiment of the invention; in Figure 5: a schematic sectional view of a nacelle front part according to a second embodiment of the invention; in Figure 6: a schematic sectional view of a nacelle front portion according to a third embodiment of the invention; in FIG. 7A: a sectional view of a resistive network according to one aspect of the invention; in FIG. 7b: a detail of a network of FIG. 7A, in FIGS. 8A, 8B and 8C: schematic views of air intake sectors provided with a deicing system according to the invention; in FIGS. 9A and 9B: a schematic representation of two modes of operation of a deicing system according to the invention; in FIGS. 10: two exemplary embodiments of deicing systems according to the invention; in FIGS. 11A and 11B: two examples of operating cycles of a deicing system according to the invention.

  The invention mainly relates to the deicing and anti-icing of aircraft parts and in particular engine nacelles of these aircraft.

  An aircraft engine nacelle 1 is schematically represented generally in FIG. 1.

  Such nacelle 1 has an air inlet 2 provided with a lip 3 followed by a tubular part 4 of air inlet.

  The front part of such a nacelle according to the prior art is shown in FIG. 2 where it can be seen that the tubular portion 4 comprising an acoustic attenuation panel is moved back relative to the air intake lip 3 to leave a buffer zone A between the defrosted portion situated in front of an internal partition 14 and the portion provided with the acoustic attenuation panel 5 so as to protect this panel from the high temperatures of the hot air defrosting device 30 symbolized by a leads 15.

  According to the exemplary embodiments of the invention in FIGS. 3, 4 and 5, the nacelle always comprises a tubular piece provided with a first acoustic attenuation panel 5 made of composite materials and, according to the invention, the lip is provided with defrosting means 6, 6a, 6b, 6c, 6d forming part of the wall of the lip and replacing the means for defrosting hot air.

  The deicing means according to the invention cover a portion 3b of the lip, internal to the air inlet, and extend, firstly on a portion 3a of the outer lip to the air inlet and on the other hand, on a junction zone 7a, 7b, 7c between the lip and the tubular air intake piece.

  More particularly, and particularly according to the embodiment of FIG. 3, the junction zone 7a comprises an advance 8 of the tubular air intake piece secured to an inner edge of an extension of the lip 3, the means defrosting device 6c covering said advance 8.

  The tubular piece 4 made of composite materials comprises an outer skin 4a and an inner skin 4b enclosing an acoustic attenuation material to form said first acoustic attenuation panel 5 and the projection 8 consists of a pinched edge of the outer skin and internal 4a, 4b, these pinched edges being secured by gluing or hot polymerization of resin impregnating the skins 4a, 4b as known in the processes for producing composite acoustic panels for example described in EP 0 897 174 Al.

  According to the example of Figure 4, the lip 3 consists of an upper cover 10 forming the extrado 12 of the air inlet and extending beyond the leading edge 11 of the lip, the tubular part 4 of air intake provided with the first sound attenuation panel extending to form a portion of the intrado 13 of the lip 3. According to this example, the deicing means forming part of the wall of the lip comprise a first 6a carpet deposited on the inner wall of the upper cover 10 and a second carpet deposited on the outer face of the acoustic attenuation panel 5 of the extended air inlet part, the junction zone 7b is approximately at the edge etching 11 of the lip 3.

  Such a construction has the advantage of producing a continuous acoustic attenuation zone from inside the engine to the level of the leading edge of the lip which is particularly favorable in the fight against noise.

  According to the example of FIG. 5, the lip 3 consists entirely of an extension of the tubular air intake piece which forms the intrado 13, the leading edge 11 and the extrado 12 of the lip 3.

  According to the example of FIG. 6, according to which the original structure of the air intake of FIG. 2 is preserved, the deicing means 6d extend beyond the junction zone to cover at least one part of the tubular air inlet part.

  The de-icing means 6a cover the outer zone 3a of the lip, the means 6b the inner zone 3b of the lip here provided with a first acoustic zone 9, the means 6c cover a junction zone 7c between the lip and the inlet of air and means 6c part of a second acoustic zone 5.

  The deicing means 6, 6a, 6b, 6c, 6d shown are electrical means and are in particular constituted by a belt incorporating heating resistors.

  To protect this mat, it is preferable to arrange it on the inner surface of the lip at least in the portion of the tip or exposed leading edge of the lip. When the de-icing means must cover an acoustic panel, the mat may instead be placed on the outer surface of the panel and be pierced with holes to allow the operation of the acoustic attenuation panel by leaving a rate of open surfaces compatible with the desired acoustic attenuation.

  The invention is particularly applicable to aircraft nacelles comprising parts of composite materials and in particular for which the tubular air intake piece 4 and acoustic attenuation panels 5, 9 are made of composite materials.

  As part of the production of electrical de-icing means, the device is adapted to operate as an anti-icing device preventing the formation of frost on the surfaces to be protected or de-icing device so as to eliminate a deposit of frost which has accumulated on the surface.

  Such a device and system as well as their operation are described in FIGS. 7 to 11B.

  As explained above, and particularly in the case of turbofan type engines, a prior art technique used for de-icing systems is to take a pneumatic power from the engine to deliver hot air through piping to the zones to be heated. defrost.

  Such a technique is based on the presence of sufficient pneumatic power and subtractable from the thrust of the engine, the presence of control valve devices and electrical control systems of these valves and the presence of sufficient space to pass the pipes in the nacelles.

  With respect to this complex prior art, the system comprises electric heating elements embedded in the thickness of the panels forming the air intake lip 3 and the tubular air intake piece, to produce a de-icing system. of an aircraft engine nacelle 1 having an air inlet 2 provided with a lip 3.

  As represented in FIG. 7A, the electric heating elements constituting the deicing means 6, 6a, 6b, 6c, 6d consist of at least one network of heating resistive elements 102 embedded in an insulating material 101, the deicing means being under in the form of a belt 103a, 103b incorporating the resistive elements 102 in the thickness of the air inlet lip between the panels 104, 105 forming it.

  The networks of resistive elements 102 comprise electric heating resistors dissipating electric power by Joule effect embedded in the insulating material 101.

  The deicing means are either metallic resistive elements, for example made of copper, or composite resistive elements, for example carbon elements.

  The electrical insulation covering the resistive elements is a flexible material including silicone or neoprene type.

  As represented in FIG. 7b, the resistive elements 102 are connected in parallel, which limits the risk of loss of efficiency of the system in the event of breakage of an element, for example following an impact of an object against the air intake. .

  Each resistive element 102 is spaced apart from adjacent elements by a distance sufficient to provide suitable electrical insulation (typically of the order of 2 mm for usual supply voltages from 0 to 400 V DC or AC).

  In addition, as shown in FIG. 7A, the resistive element heater network 102 is duplicated so as to produce two segregated networks 103a, 103b integrated in the thickness of the lip.

  This duplication of networks is performed so that in case of failure of one network the function of protection against frost is provided in degraded mode by the other networks.

  To control these networks, the system shown comprises control circuits 106, 106a, 106b of the networks, comprising two independent channels independently ensuring the control of the power supply of the two resistive networks 103a, 103b. A schematic representation of these control circuits is given in FIG. 10 while an example of routing of the power cables 108a, 108b, 108c, 108d, avoiding having cables in the lower zone of the air intake. more exposed, is given in Figures 8B and 8C in the context of a segmentation of the air intake into four sectors constituting sub-sub-networks 201, 202, 203, 204.

  Indeed, always in the interest of safety, and also to optimize the power consumption of the system, it is envisaged according to the invention to segment the air inlet into a succession of defrost sectors, 121 according to Figure 8A constituting a succession of sub-networks 201, ..., 212 driven separately by at least one control circuit 106, 106a, 106b adapted to perform either a sequential heating of the sectors or a simultaneous supply of certain sectors.

  The cables 108a, 108b, 108c, 108d group the current arrivals and departures of the sectors they distribute.

  In FIG. 8A four sections are shown, the section 301 corresponds to the connection with the cockpit, the section 302 is the section in the pylon of the engine grouping the control casings 107a and 107b of the sequencing or cycling of the system, the section 303 comprises the cable routing between the pylon and the air inlet and the section 304 corresponds to the air inlet.

  The power that must be dissipated to achieve proper anti-icing operation depends on the position of the heating element in the air inlet, the most critical area of the profile being the inner part of the air intake from the leading edge of the lip.

  To perform an anti-icing function of such a zone, the power to be dissipated is a power of the order of 1.5 W / cm 2 applied continuously.

  For less critical areas, operating in defrost mode, based on a periodic heating cycle of the surfaces, although dissipating a greater instantaneous power of the order of 2 to 3 W / cm2, will limit the consumption of the system .

  In such operation in defrost mode, the control circuit or circuits are arranged to supply and cut the networks 103a, 103b or subarrays 201,..., 212 according to defined time cycles 109 represented in FIGS. 11A and 11B. The time cycle represented in FIG. 11A comprises a passage of the current in the resistive element during a duration T0 to T3 resulting in a phase P1 of temperature rise, a phase P2 at 0 C of ice melt, a phase P3 of rise in over temperature. The circuit is then cut which corresponds to a cooling phase P4.

  FIG. 11B represents the cycles for all the sectors, the electrical conduction phases for heating the resistive elements being carried out successively.

  Operation in this de-icing mode may allow for the air intake zones to overcome a deficiency of one of the circuits while maintaining a sufficient defrosting capacity.

  The control circuit of the system shown in FIG. 10 in the context of two separate circuits 106a, 106b comprises a series of cable bundles 108 supplying all of the resistive subarrays.

  These beams constitute independent channels connected to the housings 107a, 107b separated or connected to a single control box itself connected by a bus 115 to a box 113 for monitoring and communicating with the dashboard 114 for displaying the parameters of operation and control of the system.

  As seen above, the supply of the heating networks of a nacelle is carried out with two networks of cables 108, 108a, 108b, 108c of independent power supply and sets of dedicated electrical connectors.

  The cables of each network are installed so as to be completely separated from those of the other network, so as to minimize the risk of common failure of the circuits.

  The described system optimizes the power consumption because the control circuits are arranged to power and cut the heaters according to defined time cycles according to the flight phase or the conditions of use of the system.

  The housing (s) 107a, 107b monitor the network of cables and heaters resistive networks, ensure that the voltages and electrical currents delivered are suitable and monitor the system by measuring the absence of short circuit or open circuits untimely.

  Similarly, the power supply circuits of the boxes, for example through supply bars connected to direct voltage sources 116a, 116b and alternating voltage sources 117a, 117b, are independent. In addition, to increase redundancy, each box is powered by two independent power bars.

  At a given moment, each channel or box uses the same power supply bar so that if there is a problem of electrical insulation between the two heater networks, only one of the power bars is affected.

  In particular, in the event of the loss of one of the power bars on one of the boxes or channels, the two boxes or channels will use the other power bar.

  To control the system according to the invention, the air inlet is segmented into a succession of defrosting sectors, a succession of resistive networks 201,..., 212 arranged in the de-icing sectors is controlled by at least one circuit control 106, 106a, 106b adapted to supply simultaneously or sequentially said sectors.

  Depending on the location of the sub-networks, de-icing or anti-icing operation may be preferred.

  An anti-icing phase 110 is carried out by continuously controlling at least one deicing sector while a defrosting phase 111 is carried out by means of a periodic heating cycle of at least one sector.

  FIG. 9A represents a mode of operation for which the outer part of the nacelle is controlled in defrosting with a sequential supply of the sectors and for which the tip of the air intake lip and the tubular part of the air inlet are controlled in anti-icing by a continuous supply of resistive networks arranged in this part.

  FIG. 9B represents a mode of operation for which the external part of the nacelle and the tubular part of the air inlet are supplied with defrosting sequences, only the tip of the air inlet lip being fed in the operating mode. anti-icing.

  The segregated networks may be laterally separated to cover consecutive areas as in Fig. 7B, spaced apart areas or arranged stacked or combinations thereof.

  The invention is not limited to the examples shown and in particular according to the redundancy constraints, the number of segregated networks may be greater than two.

Claims (1)

12 CLAIMS   1 - defrosting system characterized in that it comprises defrosting means (6, 6a, 6b, 6c, 6d) constituted by at least one network of resistive elements (102) heated embedded in an insulating material (101), at least two series of resistive elements being segregated so as to produce two segregated networks (103a, 103b) integrated in the thickness of a panel to defrost.   2 - defrosting system according to claim 1 characterized in that each resistive element (102) is spaced adjacent elements by a distance sufficient to provide electrical insulation between the elements.   3 - defrost system according to claim 1 or 2 characterized in that at least some of the resistive elements (102) of a segregated network are connected in parallel.   4 - defrosting system according to claim 3 characterized in that it comprises control circuits (106, 106a, 106b) networks, comprising two independent channels providing control of the power supply of the two resistive networks (103a, 103b). ).   - Defrosting system according to claim 4 characterized in that the independent channels are grouped in a single control box.   6 - Defrosting system according to one of the preceding claims characterized in that it is realized in a nacelle (1) of an aircraft engine, having an air inlet (2) provided with a lip (3) followed of a tubular piece (4) of air inlet, the air inlet is segmented into a succession of defrost sectors constituting a succession of sub-networks (201, ..., 212) driven by at least a control circuit (106, 106a, 106b) adapted to perform either a sequential heating of the sectors or a simultaneous supply of certain sectors.   7 - defrosting system according to claim 6 characterized in that the control circuits are arranged to supply and cut the networks (103a, 103b) or sub-networks (201, ..., 212) independently.   8 - Defrosting system according to one of claims 4 to 7 characterized in that the control circuit or circuits comprise control boxes (107a, 107b) arranged to monitor the resistive networks and cables (108) the supplying means, comprise means for measuring the voltages and electrical intensities delivered and for measuring the absence of a short circuit or unwanted open circuits.   9 - Control method of a de-icing system of an aircraft structure, characterized in that the structure is segmented into a succession of de-icing sectors, a succession of resistive networks (201,. ) disposed in the defrost sectors by at least one control circuit (106, 106a, 106b) adapted to supply separately said networks.