• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to an anti-lightning device (10) for an aircraft (50), comprising on the one hand an anti-corona element (20) having a rounded shape and an electrically conductive surface, intended to envelop a zone the structure of the aircraft (50) capable of hanging a lightning bolt, and secondly one or more dissipators (30) of electrical charges attached to said anti-corona element (20). In particular embodiments, the anti-lightning device (10) further comprises a dielectric shell (40) that includes the anti-corona element (20) and the dissipator (s) (30) charge.
    公开号:FR3073334A1
    申请号:FR1760532
    申请日:2017-11-09
    公开日:2019-05-10
    发明作者:Ivan REVEL；Gilles Peres
    申请人:Airbus SAS；
    IPC主号:
    专利说明:

    The present invention belongs to the field of lightning protection systems suitable for the aeronautical field. In particular, the invention relates to a device intended to reduce the risk of lightning strikes for a small aircraft.
    STATE OF THE ART
    The electrical discharge associated with lightning generally occurs between a cloud and the ground, between two clouds, or within the same cloud. Figure 1 schematically shows the formation of a lightning discharge between a cloud 90 and the ground. In the cloud 90, positive electric charges 72 develop and generally accumulate at the top of the cloud, while negative electric charges 71 are distributed at the bottom of the cloud 90. The development and distribution of the electric charges 71, 72 in the Cloud 90 has the effect of considerably increasing the electric field between the base of Cloud 90 and the ground. An electrically charged zone with a polarity opposite to that of the electric charges 71 present at the base of the cloud 90 then forms on the surface of the earth under the cloud 90, and more particularly at the level of high and pointed objects (trees, poles, buildings, etc.). This is particularly the case for building 60 represented in FIG. 1. The creation of an ionized channel in the air constitutes the first phase of the development of the electric discharge linked to lightning. This first phase is illustrated by part a) of FIG. 1. An ionized channel, also called “descending tracer” 81 or “precursor”, can progress from the base of the cloud 90 towards the ground by successive leaps of a few tens of meters. before dissociating into several ramifications when approaching the ground. When the distance between a descending tracer 81 and the ground decreases, the electric field on the ground increases until reaching a critical value (corresponding to the dielectric rigidity of the air which is of the order of 30kV / cm), then initiating at the top of certain asperities, for example at the top of building 60, corona discharges, caused by ionization of the air. By an avalanche process, if the electric field is strong enough, the ionization can increase and give rise to an “ascending tracer” 82. When, as represented on part b) of figure 1, a tracer descending 81 comes into contact with an ascending tracer 82, which generally occurs a few tens of meters from the ground, the completed ionized channel 80 between the cloud 90 and the ground causes a lightning current to flow.
    Lightning discharges occurring between two clouds, or even within the same cloud present phenomena similar to those described above with reference to Figure 1 for a lightning discharge between a cloud and the ground.
    Sometimes an aircraft is struck by lightning, either because the aircraft "intercepts" a lightning strike, the birth of which is independent of the presence of the aircraft, or because the aircraft plays a role in the creation of the ionized channel, in particular by generating an ascending tracer 82.
    The passage of a lightning current on an aircraft can cause more or less severe damage. "Direct" effects of lightning current are for example linked to the fact that it generates very strong mechanical and thermal stresses on the structure of the aircraft. These stresses are due to a very significant rise in temperature and to the formation of a shock wave at the point of contact which can damage the structure of the aircraft. "Indirect" effects are sometimes also observable: the lightning current can indeed cause electromagnetic disturbances which can lead to the malfunction of electronic equipment on board the aircraft, such as navigation equipment or communication equipment.
    For these reasons, the protection of aircraft against the effects of lightning remains a major concern for aircraft manufacturers. In fact, the vulnerability of aircraft to the effects of lightning tends to increase with the increasing use of composite materials for the structure of aircraft, and with the increased sensitivity of electronic equipment to interference generated by a lightning current. When the structure of an aircraft is mainly metallic, it behaves like a Faraday cage when struck by lightning, and it therefore confers maximum immunity on board electronic equipment. On the contrary, the composite materials which are more and more used in aeronautical construction are generally less good electrical conductors, and they do not have the same magnetic shielding characteristics as metallic materials.
    So far, aircraft manufacturers have not sought to reduce or eliminate the risk to an aircraft of being struck by lightning, as this risk cannot be completely eliminated. In practice, they are rather concerned with improving the behavior of the aircraft in the event of a lightning strike. For example, a wire mesh can be affixed to a surface of a piece of composite material in order to increase the electrical conductivity and promote the dissipation of lightning current during an impact. This type of protection is however not suitable for small aircraft for which the ratio of the area to be treated of the aircraft, and therefore of the mass of the treatment, to the volume of the aircraft is unfavorable.
    To limit the risk of lightning strikes by small aircraft, such as private planes, a take-off ban is generally imposed when a thunderstorm threat is present. This precautionary measure is however ill suited to small aircraft currently designed in the context of urban mobility to play the role of flying personal vehicle.
    To protect against lightning from buildings on the ground or boats, there are different solutions. Some are aimed at promoting a lightning strike at a determined point in order to protect a particular area, such as lightning conductors. Others, on the contrary, aim to avoid a lightning strike, this is the case, for example, of electrostatic charge dissipators which seek to make an object invisible to descending tracers from a cloud 90. Such a device aims to dissipate the charge electric accumulated at one end of the object on which it is fixed. It generally has a large number of fine metallic spikes on the surface of which multiple micro corona discharges take place, thus leading to the dissipation of the electric charge. Such devices are for example installed at the top of certain buildings, or at the top of the mast of certain boats. However, they have several drawbacks: on the one hand their shape does not allow them to be installed on an aircraft because it causes an increase in aerodynamic drag, on the other hand their effectiveness is limited and, to manage the cases where they fail to prevent the formation of an ascending tracer, it is preferable to associate them with a lightning conductor and its down conductors which allow a lightning current to be evacuated.
    In the aeronautical field, potential lossers are often positioned on the trailing edges of the wing or the tail of an aircraft in order to dissipate the electric charge accumulated by triboelectric effect during the friction of the structure of the aircraft with particles encountered during particular weather events (rain, snow, hail, dust, etc.). They generally take the form of a thin rod made of an electrically conductive material. These devices seek to limit the accumulation of electrostatic charges, the discharges of which into the air produce radioelectric emissions which are sources of interference on the electronic systems of the aircraft. They are, however, ineffective in reducing the risk to aircraft of being struck by lightning during a thunderstorm.
    Thus, while it is considered in the context of urban mobility the massive use of small aircraft playing the role of flying personal vehicles, there is no effective system to significantly reduce the risk for such an aircraft of being affected by lightning.
    Reducing the risk of a lightning strike would, however, reduce the maintenance and repair costs of aircraft linked to damage caused by lightning, and would simplify the means of protection implemented to limit the effects of a lightning strike. lightning.
    STATEMENT OF THE INVENTION
    The present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above, by proposing a device which aims to significantly reduce the risk for an aircraft of undergoing a lightning strike.
    The invention finds a particularly advantageous, although in no way limiting, application for small aircraft currently designed in the context of urban mobility to play the role of flying personal vehicle. Indeed, this type of aircraft is particularly vulnerable to the risk of lightning strike because on the one hand it is intended to fly at low altitude in any weather for the journeys of daily life, and on the other hand, for reasons of lightness , its structure generally does not have sufficient metal shielding to drain a high lightning current and limit the damage caused by the attachment of a lightning arc.
    To this end, and according to a first aspect, the invention relates to a lightning protection system, called "lightning protection device", comprising an anti-corona element having a rounded shape and an electrically conductive surface, intended to envelop an area of the structure of an aircraft capable of initiating the departure of a lightning precursor, as well as one or more electric charge dissipators attached to said anticorona element.
    Such provisions make it possible to reduce the risk of a lightning strike at the level of the area to be protected by avoiding the formation, at the level of said area, of a corona discharge which can generate an ascending tracer which could initiate a lightning discharge.
    In particular embodiments, the lightning protection device may further include one or more of the following characteristics, taken in isolation or in any technically possible combination.
    In particular embodiments, the lightning protection device further comprises a dielectric shell including the anti-corona element and the charge sink (s), each charge sink at least partially passing through said dielectric shell. Beyond its protective interest (for example against impact or against corrosion), this dielectric shell makes it possible to improve the aerodynamics of the aircraft by limiting the influence of the lightning protection device on the drag of the aircraft.
    In particular embodiments, part of the conductive surface of the anti-corona element is flush with an external surface of the dielectric shell to form a preferential attachment zone for a lightning arc. Such provisions make it possible to protect the lightning protection device in the event that, despite the means used, a lightning strike should still take place, by promoting an impact at the level of the anticorona element rather than on the dielectric shell. or at the level of the load sinks.
    In particular embodiments, a load sink comprises an electrically conductive rod, one end of which is fixed to the anti-corona element and the other end of which serves as a point of attachment to a set of conductive strands of electricity of which only one end of each distal strand of the rod protrudes from the dielectric shell. Each strand thus crosses the dielectric shell and only a small part of the strand protrudes outside the shell. The dielectric shell then locally strengthens the electric field at the end of each strand which protrudes from the shell, and thus promotes the dissipation of electrical charges.
    In particular embodiments, the lightning protection device comprises two charge dissipators, the anti-corona element is substantially a sphere, the dielectric shell has substantially the shape of an ellipsoid whose center coincides substantially with the center of the anti-corona element, and each charge dissipator extends radially from the anti-corona element at two diametrically opposite points along the longest axis of the ellipsoid formed by the dielectric shell.
    In particular embodiments, the set of strands of each charge sink follows the shape of a vertex of the ellipsoid formed by the dielectric shell.
    In particular embodiments, the end of a distal strand of the rod of a load sink protrudes from the dielectric shell by a length at least equal to 10% of the thickness of the dielectric shell traversed by said brown.
    In particular embodiments, each strand has a diameter of between 50 and 500 μm and is made of a conductive material whose electrical resistivity is at least 100 times that of a rod.
    The use of thin and resistive strands promotes the dissipation of electrical charges while limiting the intensity of the corona micro-discharges by which this dissipation takes place.
    In particular embodiments, the anti-corona element is made of aluminum alloy.
    According to a second aspect, the present invention relates to an aircraft comprising a lightning protection device according to any one of the preceding embodiments.
    In particular embodiments, the lightning protection device is integrated on the aircraft so that the major axis of the ellipsoid formed by the dielectric shell substantially coincides with the main direction of movement of the aircraft. Such arrangements make it possible in particular to optimize the aerodynamic drag, and to generate a space charge zone enveloping the lightning protection device and further limiting the risk of a lightning strike.
    PRESENTATION OF THE FIGURES
    The invention will be better understood on reading the following description, given by way of nonlimiting example, and made with reference to FIGS. 1 to 9 which represent:
    - Figure 1: a schematic representation of the formation of a lightning discharge between a cloud and a building on the ground (figure already mentioned in the prior art),
    - Figure 2: a schematic representation of the formation of a lightning discharge involving an aircraft,
    - Figure 3: a schematic representation of the operation of a lightning protection device according to the invention,
    - Figure 4: a schematic representation of a particular embodiment of a lightning protection device according to the invention,
    - Figure 5: a schematic representation of the operation of an anti-corona element,
    - Figure 6: a schematic representation of a charge sink of the lightning protection device,
    - Figure 7: a detailed schematic representation of part of the load sink shown in Figure 6,
    - Figure 8: a schematic representation of the installation of a lightning protection device according to the invention on one end of the structure of an aircraft,
    - Figure 9: a schematic representation of the installation of a lightning protection device according to the invention on a small aircraft;
    In these figures, identical references from one figure to another denote identical or analogous elements. For reasons of clarity, the elements represented are not necessarily on the same scale, unless otherwise stated.
    DETAILED DESCRIPTION OF EMBODIMENTS
    The present invention relates to a lightning protection device intended to significantly reduce the risk of a lightning strike on an aircraft.
    In the following description, and for the reasons mentioned above, we take as an example and without limitation in the case of a small aircraft 50 envisaged in a context of urban mobility to be used as a flying personal vehicle . It should however be noted that the present invention is also applicable to other types of aircraft which are, by their structure, vulnerable to a lightning strike, and whose speed is low enough for the aerodynamic impact of a An anti-lightning device according to the invention remains acceptable, such as, for example, drones, helicopters, or light airplanes of the passenger plane or ULM (“motorized ultralight”) type. Even more generally, the present invention can also be intended for other vehicles, such as for example boats, or even for fixed elements such as buildings.
    Figure 2 shows the formation of a lightning discharge involving an aircraft 50. In the example shown in Figure 2, negative electrical charges 71 accumulate at the bottom of a cloud 90, while positive electrical charges 72 accumulate at the top of the cloud 90. The aircraft 50 which passes near the cloud 90 then undergoes an electric field which causes a distribution of the electric charges 71, 72 present on the structure of the aircraft 50 towards its ends, as by example the tip of the wings or the tip of the plane surfaces of the tail. Depending on the orientation of the electric field in which the aircraft 50 bathes, the electric charges 71, 72 accumulated at the ends of the aircraft 50 are sometimes positive (for the ends situated on the side of the base of the cloud 90), sometimes negative ( for the ends located opposite the base of the cloud 90).
    As illustrated by part a) of FIG. 2, a descending tracer 81 can be born at the base of the cloud 90 and progress gradually by successive leaps of a few tens of meters. This descending tracer 81 corresponds to the initiation of an ionized channel in the air which transports an electric charge and advances towards an opposite charge zone. When the distance between the descending tracer 81 and the aircraft 50 decreases, the electric field existing at the level of certain parts of the structure of the aircraft 50 may increase until reaching a critical value corresponding to the dielectric strength of the air. , then initiating upward tracers 82, 83 by corona discharges. These ascending tracers 82, 83 are sometimes positive ascending tracers 82, sometimes negative ascending tracers 83, according to the sign of the electric charges 71,72 which induce them.
    When, as shown in part b) of FIG. 2, a negative descending tracer 81 comes into contact with a positive ascending tracer 82, the completed ionized channel 80 between the cloud 90 and the aircraft 50 then causes the flow of a lightning current which can cause more or less significant damage to the structure of the aircraft 50 or to its electronic equipment. It should be noted that the formation of such a completed ionized channel 80 between the cloud 90 and the aircraft 50 naturally supposes a junction with another accumulation of electric charges (in the example considered it is an accumulation positive electrical charges), for example on the ground or in another cloud. This other accumulation of electrical charges forming the final end of the completed ionized channel 80 is not shown in FIG. 2 for the sake of simplification.
    It should be noted that in the example described with reference to FIG. 2, the descending tracer 81 is a negative descending tracer, coming from the base of the cloud 90 which is negatively charged, and leading to what is commonly called a negative love at first sight. According to another example, the descending tracer may be positive if it originates in the upper part of the cloud 90 and leads to a positive lightning strike if it joins a negative ascending tracer 83.
    It should also be noted that according to yet another example, an ascending tracer 82 can be initiated autonomously from one end of the aircraft 50 and go towards the cloud 90, then triggering a descending tracer 81 at the base of the cloud 90 then a lightning discharge when the upward tracer 82 and the downward tracer 81 meet.
    FIG. 3 represents a situation analogous to that represented in FIG. 2, namely an aircraft 50 passing near the negatively charged base of a cloud 90. Unlike the aircraft 50 represented in FIG. 2, the aircraft 50 represented in FIG. 3 comprises several lightning protection devices 10 according to the invention in order to considerably reduce the risk of lightning impact. In the nonlimiting example shown in FIG. 3, the aircraft 50 comprises such a lightning protection device 10 at the end of each of its two wings, as well as on the vertical part of its tail.
    In part a) of FIG. 3, a descending tracer 81 originates at the base of the cloud 90 and approaches the aircraft 50 and the ground where a building 60 is located in particular. The objective of the anti- Lightning 10 according to the invention is to make the aircraft 50 "invisible" when approaching the descending tracer 81 by avoiding or delaying the appearance of ascending tracers 82, 83 at the structure of the aircraft 50. The means implemented by the lightning protection device 10 to achieve this objective are multiple and they will be detailed in the following description.
    On the one hand, this involves dissipating the electrical charges 71, 72 accumulated on the ends of the aircraft 50 by corona micro-discharges, the magnitude of which is small enough not to initiate an ascending tracer 82. This dissipation of electric charges 71, 72 leads to a decrease in the electric field at the ends of the structure of the aircraft 50. An electric field 70 observed locally at one end, despite the peak effect which tends to increase its intensity , is then no longer sufficient to trigger a corona discharge which can lead to the appearance of an ascending tracer 82. In other words, the dissipation of electric charges 71, 72 contributes to maintaining the amplitude of the electric field 70 existing in the vicinity of ends of the structure of the aircraft 50 to a value below the initiation threshold of a precursor. In addition, the space charge 74 generated by the accumulation in the air of the electric charges 71, 72 dissipated reinforces the limitation of the electric field 70 at the surface of the aircraft 50. This space charge 74 generates indeed an electric field, called "electric field of charge of space", which is opposed to the electric field 70 present on the point which gave birth to it.
    It is also a question of adapting the geometry of the structure of the aircraft 50 in order to limit the gradient of electric potential at its ends in order to prevent the triggering of a corona discharge which could be at the origin of an ascending tracer 82.
    On the contrary, an ascending tracer 82 can arise at ground level, for example at the level of an upper end of a building 60. Part b) of FIG. 3 represents the completed ionized channel 80 generated by the meeting of the descending tracer 81 with the ascending tracer 82 emanating from the building 60. A lightning current can then flow through this channel. By preventing the formation of an ascending tracer 82 at the level of the aircraft 50, the lightning protection device 10 made it possible to avoid a lightning strike on the aircraft 50.
    It should be noted that the objective of the lightning protection device 10 is not only to make the aircraft 50 invisible to a possible descending tracer 81 originating from the cloud 90, but also to avoid the autonomous formation of an ascending tracer 82 ( independently of the existence of a descending tracer 81).
    FIG. 4 represents a particular embodiment of a lightning protection device 10 according to the invention. On the one hand, it comprises an anti-corona element 20 which has a rounded shape and an electrically conductive surface, for example a metallic sphere. This element 20 is qualified as “anticorona” because it has the objective of preventing the triggering of a corona discharge which could be at the origin of an ascending tracer 82. This anticorona element 20 will be described in more detail later with reference to Figure 5.
    The lightning protection device 10 also comprises two charge dissipators 30 which extend radially from the anti-corona element 20 at two diametrically opposite points. Each load sink 30 includes a rod 31, one end of which is fixed to the anti-corona element 20 and the other end of which serves as a point of attachment to a set 32 of electrically conductive strands 33. The function of the dissipators 30 is to dissipate (in other words to evacuate into the surrounding air) the electric charges 71, 72 accumulated on the ends of the aircraft 50 by corona micro-discharges the magnitude of which is sufficiently small to not not initiate upward tracer 82. Such a load dissipator 30 will be described in more detail later with reference to FIGS. 6 and 7.
    It should be noted that the number of charge dissipators 30 that the lightning protection device 10 comprises may vary, and this choice is only an alternative embodiment of the invention.
    The lightning protection device 10 is intended to be fixed in areas of the aircraft 50 corresponding to areas of attachment of a lightning arc, in particular at the end of a projecting part of the structure of the aircraft 50, for example at the end of a wing 51 or at the end of the tail 52. Advantageously, to limit the aerodynamic impact of the lightning protection device, the anti-corona element 20 and the two load dissipators 30 are integrated into a dielectric shell 40, made for example of fiberglass, whose shape minimizes its aerodynamic drag. For example, the shell 40 has an ellipsoid shape, the center of which coincides with the center of the sphere of the anti-corona element 20 and the largest axis of which is oriented along the rods 31 of the load dissipators 30. The strands 33 of the heat sinks are arranged so that only part of their length protrudes from the dielectric shell 40 near each end of the ellipsoid along its longest axis. In addition to aerodynamic performance, the dielectric shell 40 can also have a role of mechanical protection (for example against shocks) and / or chemical (for example against attacks of the corrosion type), and may also incidentally be of aesthetic interest. It will also be explained later how the dielectric shell 40 contributes to increasing the efficiency of the load dissipators 30.
    It should be noted that the invention can obviously be achieved by choosing another shape for the dielectric shell 40. For example, each end of the dielectric shell 40 may be in the form of an ogive, possibly truncated by a sphere, or else the dielectric shell 40 may be in the shape of an ovoid or in the form of a drop of water. The shape can obviously be optimized, in a conventional manner, by wind tunnel tests in order to optimize its aerodynamics. In the example considered, the dielectric shell 40 is a hollow shell whose wall has a thickness adapted to the resistance to the aerodynamic forces undergone in use taking into account the material used.
    In one embodiment, the empty part of the shell 40 is filled with a cellular material, for example a polyurethane foam, which makes it possible to bring rigidity to said shell with a minimal mass penalty.
    In particular embodiments, the lightning protection device 10 does not include a dielectric shell 40. This is for example the case when aerodynamics, protection from the environment, even aesthetics, have little or no importance for the object protected by the lightning protection device 10.
    FIG. 5 schematically illustrates the advantage of the anti-corona element 20 forming part of the lightning protection device 10 according to the embodiment described with reference to FIG. 4.
    Part a) of FIG. 5 represents a concentration of positive electrical charges 72 accumulated at the end of a wing 51 of an aircraft 50. This excess of positive electrical charges 72 at the end of a wing 51 of an aircraft 50 can in particular be observed when the aircraft 50 is subjected to an electric field induced by the presence of a cloud 90 negatively charged. The electric charges 71, 72 present on the structure of the aircraft 50 separate and move according to the electric field. This results in an electrostatic imbalance on the structure of the aircraft 50 and accumulations of electric charges 71,72 at the ends. The accumulations of electric charges 71, 72 can be positive (as in the example illustrated in FIG. 4) or negative, depending on the orientation of the electric field with respect to the structure of the aircraft 50 and according to the orientation of the 'end considered.
    As shown in part a) of FIG. 5, an electric field 70 then intensifies at the level of the accumulation of electric charges 72 due to the peak effect. If its amplitude exceeds a critical value corresponding to the dielectric strength of the air, then corona discharges can occur. Such a corona discharge can be the cause of an ascending tracer 82 which, if it comes into contact with a descending tracer 81 coming from a cloud 90, can lead to a lightning strike at the end of wing 51.
    It should be noted that other phenomena can participate in the electrostatic charge of an aircraft. In particular, precipitation particles (water droplets, ice, snow crystals, dust, etc.) exchange electrical charges with the aircraft by triboelectric effect. Also, physical mechanisms inside the combustion chamber of aircraft engines can result in an expulsion of positive electrical charges, leaving negative charges on the structure of the aircraft. A lightning protection device 10 also participates in the electrostatic protection of an aircraft 50, or even it can completely replace the static heaters traditionally used to protect it.
    Part b) of FIG. 5 schematically represents the end of a wing 51 of an aircraft 50 to which a lightning protection device 10 has been fixed.
    In the example considered, the anti-corona element 20 is an aluminum alloy sphere of around thirty centimeters in diameter which completely envelops the end of the wing 51. Given the peak effect, the electric field 70 observed at the level of a conductive element is generally all the greater when the element in question is sharp, angular or sharp. The anti-corona element 20 provides a rounded shape at the end of the wing 51. This shape has the effect of reducing the amplitude of the electric field 70 observed at the end of the wing 51 by eliminating, at least in part, the peak effect. The electrical potential gradient at the end of the wing 51 is then lower because the positive electrical charges 72 are distributed over the entire surface of the metallic sphere. It is thus possible, for appropriate dimensions of the anti-corona element 20 relative to the dimensions of the wing 51, to maintain the electric field 70 existing in the vicinity of the end of the wing 51 at a value of amplitude below the threshold for triggering a corona discharge strong enough to trigger an ascending tracer 82. The risk of being struck by lightning is then considerably reduced.
    In known manner, high voltage tests can be carried out in the laboratory to optimize the characteristics of the anticorona element 20, in particular its shape, its dimensions, and the material used. These tests can be carried out by computer-assisted digital modeling as a function of the characteristics of the structure of the aircraft 50.
    It should be noted that in the particular embodiment described with reference to FIG. 4, and in the example represented in part b) of FIG. 5, the anti-corona element 20 takes the form of a metallic sphere. linked to the wing 51 of the aircraft 50 so that it envelops the end of said wing 51. For obvious reasons of mass, this sphere is advantageously hollow, only its external surface being significant in the desired effects. According to other examples, the anti-corona element 20 could have another shape with rounded contours, such as for example a torus or a ring, or else be made from a composite material which would be metallized on the surface.
    In particular embodiments, the anti-corona element 20 is an integral part of the wing 51 and thus corresponds to a particular shape of the end of the wing 51. It is then integrated into the structure of the aircraft 50 during the assembly phase of the structure considered.
    FIG. 6 schematically represents one of the two charge dissipators 30 forming part of the lightning protection device 10 according to the embodiment described with reference to FIG. 4. It comprises a rod 31 of which one end serves as an attachment point for an assembly 32 of strands 33. The rod 31 and the strands 33 are electrically conductive. The fixing means used to attach the strands 33 to the end of the rod 31 is such that it allows an electrical connection between the rod 31 and each strand 33. Preferably, the strands 33 are not twisted.
    In the example considered, the rod 31 is made of steel and the strands 33 are made of carbon fiber. The electrical resistivity of a strand 33 is thus largely (at least 100 times) greater than that of the rod 31. The rod 31 is approximately 20 cm in length and 1 cm in diameter, the length of each strand 33 is around 5 to 10 cm. The thickness of a strand 33 is about 100 µm. The assembly 32 is composed of several tens of strands 33.
    The operating principle of such a load dissipator 30 is based on the peak effect, that is to say that the amplitude of the electric field in the vicinity of a conductor brought to a certain electric potential is all the more larger than the conductor is thin. On the other hand, a corona discharge caused by the ionization of the ambient air surrounding the conductor appears only if the amplitude of the electric field in the vicinity of the conductor is greater than a critical value corresponding to the dielectric strength of the air. The power dissipated by a corona discharge is lower the thinner the conductor and the higher its electrical resistivity. Thus, by using strands 33 of fine and resistive carbon fiber, the generation of small corona discharges with very low energy (we speak of "corona micro-discharges") is favored. These corona micro-discharges are of sufficiently small magnitude not to generate an ascending tracer 82. By grouping a set 32 of strands 33, a multitude of corona micro-discharges is obtained which are decorrelated from one another and which are suitable for efficiently discharge a part of the structure of an aircraft 50 without presenting the risk of generating an ascending tracer 82 which could lead to a lightning discharge.
    Thus, the shape and size of the strands 33 make it possible to create a field reinforcement in an extremely reduced volume in the vicinity of each strand 33, resulting in conditions favorable for the dissipation of charges by corona effect, but unfavorable for a transformation of these corona discharges as precursors for lightning.
    FIG. 7 illustrates how the rod 31 and the strands 33 of the load dissipator 30 are integrated into the dielectric shell 40 which, in the example considered, is a hollow shell, the wall 43 of glass fiber having a thickness of a few centimeters . The thickness of the wall is chosen according to the material used so as to have a mechanical resistance adapted to the aerodynamic forces undergone in use. The wall 43 of the dielectric shell 40 has an internal surface 41 and an external surface 42.
    To make the figure clearer, only ten strands 33 have been shown. The length and the arrangement of the strands 33 are adapted to the ellipsoidal shape of the dielectric shell 40, such arrangements having in particular the objective of improving the aerodynamics of the lightning protection device 10. It appears in particular in FIG. 7 that only a small end 34 of each strand 33 protrudes from the dielectric shell 40, for example between 1% and 10% of the length of the strand 33 protrudes from the shell 40. It is by this end 34 that micro-discharges will take place corona in the air. The characteristics of the rod 31 and of the strands 33 such as the material used, their thickness, their length, their arrangement, their number, etc., can for example be defined in the laboratory, in conventional manner, using tests under high tension. The length of the portion of the strand 33 which protrudes from the dielectric shell (40) must be large enough to allow the dissipation of electrical charges and small enough to limit their brittleness. This length should be optimized by testing. For example, one end 34 of each strand 33 protrudes from the dielectric shell 40 by a length at least equal to 10% of the thickness of the shell 40 traversed by said brown 33.
    In addition to improving the aerodynamics of the lightning protection device 10, the dielectric shell 40 has an additional advantage induced by a distortion and a strengthening of the local electric field existing at the ends 34 of the strands 33 of the load sink 30 because of the permittivity of the dielectric. Thus, without having an overall impact on the risk of generating a corona discharge strong enough to initiate an ascending tracer 82, this phenomenon locally promotes the generation of corona micro-discharges at the ends 34 of the strands 33 of the charge dissipator 30, which consequently allows 'improving the dissipation of the electric charges 71,72 accumulated on the part of the structure of the aircraft 50 to which the lightning protection device 10 is fixed.
    FIG. 8 schematically represents a lightning protection device 10 according to the embodiment described with reference to FIG. 4 and fixed to the end of a projecting part of the structure of the aircraft 50. In the example illustrated in FIG. 8, the lightning protection device 10 is fixed to the end of a wing 51 so that the anti-corona element 20 envelops an end rib of the wing 51. Thus, the angular parts at the 'end of the wing 51, capable of inducing peak effects on the electric field, are eliminated. In the example considered, an accumulation of positive electric charges 72 has formed at the end of the wing 51, for example under the effect of an electric field induced by the presence of a cloud 90.
    Advantageously, the axis formed by the rods 31 of the two load dissipators 30 (which in the example considered coincides with the largest axis of the ellipsoid formed by the dielectric shell 40) is oriented in the main direction 53 of the aircraft 50. Such arrangements have at least two advantages. A first advantage is to limit the impact of the lightning protection device 10 on the drag of the aircraft 50. Indeed, the vertices of the ellipsoid formed by the dielectric shell 40 are positioned so that the flow air on the lightning protection device 10 is optimal when the aircraft 50 is moving. A second advantage lies in the fact that all of the electrical charges 72 dissipated by the two charge dissipators 30 will form a zone of space charge 74 which will envelop the end of the wing 51 and which will thus limit the electric field 70 observed at the end of the wing 51. The positioning of the load dissipators 30 in the main direction 53 of movement of the aircraft 50 is in fact such that the electric charges 72 dissipated in the air by the dissipator 30 located towards the front of the aircraft 50 will substantially skirt the surface of the hull 40 along its longest axis before being evacuated. This flow of electric charges 72 in the air near and along the surface of the dielectric shell 40 generated by the movement of the aircraft 50 thus makes it possible to wrap the end of the wing 51 in a charging zone. of space 74.
    In particular embodiments, the dielectric shell 40 has an opening so that part of the anti-corona element 20 is flush with the external surface 42 of the shell 40. In this way, if a lightning strike were to take place despite all the means implemented by the lightning protection device 10, the lightning strike point would preferably occur at this level portion of the anti-corona element 20, thus limiting the risk of perforation of the shell 40 and a deterioration of the lightning protection device 10. The flush area of the anti-corona element 20 can be painted to avoid corrosion phenomena and / or for an aesthetic appearance.
    FIG. 9 illustrates an example of installation of a lightning protection device 10 according to the invention on a small aircraft 50 playing the role of a flying personal vehicle. In the example shown in Figure 9, the lightning protection device 10 follows the particular embodiment described with reference to Figure 4, and it is fixed to the upper end of the vertical part of the tail 52 of the aircraft 50.
    It should be noted that this is a non-limiting example, and that in other variants, the lightning protection device 10 could also be placed at the lower end of the vertical part of the tail 52 , or, depending on the shape of the structure of the aircraft 50, at the end of the wings 51 or else at the end of other projecting parts where corona discharges tend to develop naturally. Advantageously, several lightning protection devices 10 can be placed at different locations on the structure of the aircraft 50 corresponding to areas capable of catching a lightning arc.
    The means for fixing a lightning protection device 10 to the structure of the aircraft 50 are not detailed since they are outside the scope of the invention. They can be implemented by conventional methods of assembling parts of an aircraft (welding, gluing, riveting, screwing, etc.). However, it is necessary to ensure electrical continuity between the anti-corona element 20 and the area of the structure of the aircraft 50 protected by the lightning protection device 10, so that electrical charges 71, 72 accumulated on said area can be distributed over the surface of the anti-corona element 20.
    The above description clearly illustrates that, by its various characteristics and their advantages, the present invention achieves the objectives set. In particular, the lightning protection device 10 considerably reduces the risk of lightning strikes from an aircraft 50 while limiting its impact on its aerodynamic drag. The weight and the manufacturing cost of such a device also remain particularly advantageous.
    The invention advantageously combines two elements whose intrinsic functions are opposite, but whose combination fulfills the desired objectives. Indeed, the invention involves on the one hand an anticorona element 20 whose function is to prevent the formation of a corona discharge which could lead to an ascending tracer 82 which can initiate a lightning discharge, and on the other hand to minus a charge dissipator 30 whose function is to generate corona discharges of small magnitude to dissipate an accumulation of electrical charges.
    There is a cooperation of the various elements of the lightning protection device 10 to reduce the peak effect of one end of the structure of an aircraft 50:
    - the anti-corona element 20 decreases the potential gradient at the end to be protected,
    - the charge dissipators 30 reduce the electrical potential of the end to be protected,
    - the position of the load dissipators 30 makes it possible to wrap the end to be protected in a space charging area 74, so that it no longer appears as an electrical tip,
    - the dielectric shell 40, if there is one, improves the efficiency of the load dissipators 30.
    It is indeed the combination of several of these effects that gives lightning protection device 10 according to the invention a significant effectiveness.
    In general, it should be noted that the embodiments considered above have been described by way of nonlimiting examples, and that other variants are therefore possible.
    In particular, the number of charge dissipators 30 that the lightning protection device 10 includes is not limited to two. A lightning protection device 10 according to the invention may indeed comprise only a single dissipator 30 of charges or else a number of dissipators 30 of charges greater than two. Also, the characteristics of such a load sink 30 may vary. In the example considered, the rod 31 is made of steel and the strands 33 are made of carbon fiber. Other electrically conductive materials can however be envisaged for the production of a charge dissipator 30. Preferably, the rod 31 is made of metal, and the strands 33 are made of a conductive material of higher electrical resistivity (for example at least 100 times greater than that of the rod 31) and they have a particularly fine diameter (for example between 50 pm and 500 pm) to limit the intensity of the corona micro-discharges.
    In the example considered, the anti-corona element 20 is a hollow metallic sphere made of an aluminum alloy. However, nothing precludes considering other rounded shapes for the anti-corona element 20, such as for example an ovoid, a torus, a ring, etc. Also, another material can be chosen if it has good electrical conductivity at the surface and relative lightness.
    In the example considered, the dielectric shell 40 has the shape of an ellipsoid and is made of fiberglass for its resistance to mechanical stresses and its electrical insulation properties. However, nothing precludes considering other forms and other materials for the production of the dielectric shell 40, or even not using a dielectric shell 40, for example if the aerodynamics and the protection against environment have little or no importance for the object protected by the lightning protection device 10.
    The dimensions of the various elements of the lightning protection device 10 are chosen as a function of the dimensions of the parts of the structure of the aircraft 50 which should be protected against catching of a lightning arc. Also, the dimensions indicated in the embodiments described have been given by way of non-limiting example.
    The invention has been described by way of nonlimiting example by considering the case of a small aircraft 50 developed to play the role of flying personal vehicle. Indeed, such an aircraft 50 is intended to fly at low altitude in all weathers for the journeys of daily life, and its particularly light structure to promote low energy consumption generally only provides it with limited protection against damage caused by lightning (because its structure does not contain metal shielding to drain a lightning current and limit the damage caused by the attachment of a lightning arc). However, nothing excludes, according to other examples, from considering other types of vehicles, whether air, sea or land, or even using a lightning protection device 10 to protect fixed objects such as for example parts of a building.
    权利要求:
    Claims (12)
    [1" id="c-fr-0001]
    1. Lightning protection device (10) for an aircraft (50), comprising on the one hand an anti-corona element (20) having a rounded shape and an electrically conductive surface, intended to envelop an area of the structure of the aircraft (50) capable of catching a lightning arc, and on the other hand at least one dissipator (30) of electrical charges fixed to said anticorona element (20).
    [2" id="c-fr-0002]
    2. Lightning protection device (10) according to claim 1, in which a charge dissipator (30) comprises an electrically conductive rod (31), one end of which is fixed to the anti-corona element (20) and of which the other end serves as a point of attachment to a set (32) of strands (33) conducting electricity.
    [3" id="c-fr-0003]
    3. Lightning protection device (10) according to one of claims 1 to 2 further comprising a dielectric shell (40) including the anti-corona element (20) and the charge dissipator (s) (30), each dissipator (30) of charges at least partially passing through said dielectric shell (40).
    [4" id="c-fr-0004]
    4. Lightning protection device (10) according to claim 3 wherein a portion of the conductive surface of the anti-corona element (20) is flush with an external surface (42) of the dielectric shell (40) to form a zone preferential attachment of a lightning arc.
    [5" id="c-fr-0005]
    5. Anti-lightning device (10) according to one of claims 3 to 4 in which a charge dissipator (30) comprises an electrically conductive rod (31), one end of which is fixed to the anti-corona element (20) and the other end of which serves as a point of attachment to a set (32) of strands (33) electrically conductive of which only one end (34) of each distal strand of the rod (31) exceeds the dielectric shell (40).
    [6" id="c-fr-0006]
    6. Lightning protection device (10) according to claim 5 comprising two charge dissipators (30), in which the anti-corona element (20) is substantially a sphere, the dielectric shell (40) has substantially the form of an ellipsoid whose center substantially coincides with the center of the anti-corona element (20), and each load dissipator (30) extends radially from the anti-corona element (20) at two diametrically opposite points along the largest axis of the ellipsoid formed by the dielectric shell (40).
    [7" id="c-fr-0007]
    7. Lightning protection device (10) according to claim 6 in which the set (32) of strands (33) of each dissipator (30) matches the shape of an apex of the ellipsoid formed by the shell ( 40) dielectric.
    [8" id="c-fr-0008]
    8. Lightning protection device (10) according to one of claims 5 to 7 in which for each dissipator (30) the end (34) of a strand (33) distal of the rod (31) protrudes from the shell (40) dielectric with a length at least equal to 10% of a thickness of said dielectric shell (40) traversed by said strand (33).
    [9" id="c-fr-0009]
    9. Lightning protection device (10) according to claim 2 or one of claims 5 to 8 wherein each strand (33) has a diameter between 50 and 500 pm and is made of a conductive material whose electrical resistivity is at least 100 times greater than that of a rod (31).
    [10" id="c-fr-0010]
    10. Lightning protection device (10) according to one of claims 1 to 9 wherein the anti-corona element (20) is formed from an aluminum alloy.
    [11" id="c-fr-0011]
    11. Aircraft (50) characterized in that it comprises a lightning protection device (10) according to one of claims 1 to 10.
    [12" id="c-fr-0012]
    12. Aircraft (50) characterized in that its structure includes an anti-lightning device (10) according to one of claims 6 to 7 so that the major axis of the ellipsoid formed by the dielectric shell (40) substantially coincides with the main direction of movement of the aircraft (50).
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    同族专利:
    公开号 | 公开日
    US20190135449A1|2019-05-09|
    FR3073334B1|2020-11-06|
    US11027857B2|2021-06-08|
    EP3483070A1|2019-05-15|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US2515182A|1947-02-28|1950-07-18|Willard H Bennett|Apparatus for discharging static electricity from aircraft|
    US3617805A|1970-03-02|1971-11-02|Dayton Aircraft Prod Inc|Low-noise static discharger device|
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    US6307149B1|1999-09-10|2001-10-23|Fcc/Enforcement Bureau|Non-contaminating lightning protection system|
    CN204750581U|2015-03-13|2015-11-11|空客工程技术中心有限公司|Static discharger and including this static discharger's aircraft|US10457413B2|2017-07-25|2019-10-29|The Boeing Company|Methods and systems for aircraft lightning strike protection|
    US10549865B2|2017-10-19|2020-02-04|Honeywell International Inc.|Lightning protected gas turbine engine|
    JP6677703B2|2017-12-21|2020-04-08|株式会社Ｓｕｂａｒｕ|Lightning current control device, lightning current control method, and aircraft|
    法律状态:
    2019-05-10| PLSC| Publication of the preliminary search report|Effective date: 20190510 |
    2019-11-20| PLFP| Fee payment|Year of fee payment: 3 |
    2020-11-20| PLFP| Fee payment|Year of fee payment: 4 |
    2021-11-22| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1760532A|FR3073334B1|2017-11-09|2017-11-09|ANTI-LIGHTNING DEVICE FOR AIRCRAFT, AIRCRAFT CONTAINING SUCH AN ANTI-LIGHTNING DEVICE|
    FR1760532|2017-11-09|FR1760532A| FR3073334B1|2017-11-09|2017-11-09|ANTI-LIGHTNING DEVICE FOR AIRCRAFT, AIRCRAFT CONTAINING SUCH AN ANTI-LIGHTNING DEVICE|
    US16/181,513| US11027857B2|2017-11-09|2018-11-06|Lightning protection device for an aircraft, aircraft comprising such a lightning protection device|
    EP18204827.2A| EP3483070A1|2017-11-09|2018-11-07|Lightning arrestor device for aircraft, aircraft comprising such a lightning arrestor device|
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