Abstract:
A piece of electronic equipment of a turbomachine, including a wall of which the inner surface defines at least one channel for the passage of a ventilating air stream of which the outlet opens on an outer surface of the wall with a view to discharging the ventilating air stream towards the outside of the equipment, wherein, at the outlet, a mechanism for diverting and/or guiding at least a portion of the discharged air stream, over at least a part of the outer surface of the wall.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a piece of electronic equipment of a turbine engine, this equipment being an on-board computer of the electronic engine control type EEC (Electronic Engine Control acronym), for example. 
       PRIOR ART 
       [0002]    An aircraft turbine engine comprises at least one EEC-type on-board computer which in particular allows actuators of the engine to be monitored in order to optimize the turbine-engine performance (FR-B1-2 960 912). This computer is generally mounted together with other equipment (accessory gearbox AGB, exchangers, etc.) in the internal annular space in the nacelle of the turbine engine, the temperature of the air flow in this space being possibly relatively significant during operation. 
         [0003]    The nacelle comprises a scoop for drawing off air during flight in order to supply air to the annular space in the nacelle, this air then being discharged through an air outlet grating of the nacelle. However, on the ground, this aeration is virtually non-existent and the natural convection in the annular space in the nacelle may prove to be insufficient to ensure the ventilation of the equipment thereof. 
         [0004]    The EEC computer comprises a housing, inside which electronic boards are installed. These electronic boards have low temperature stability, which makes it necessary to ventilate the housing using a dedicated system comprising means for drawing off air flowing on the outside of the nacelle of the turbine engine. 
         [0005]    In the current art, the housing of the computer is covered by a wall which defines ducts through which a ventilation air flow passes, the inlets of which are connected by a collector to the above-mentioned means for drawing off air and the outlets lead onto the outer surface of the wall. Some of the heat dissipated by the electronic boards during operation is absorbed by the ventilation air flow which circulates in the ducts, this air flow then leaving the ducts in order to be discharged into the annular space in the nacelle. 
         [0006]    It has been noted that the amount of heat absorbed by the ventilation air flow is greater (approximately double) than the heat dissipated by the electronic boards. This is due to the fact that the ventilation air flow does not only absorb heat dissipated by the electronic boards, but also heat from the ambient air prevailing in the annular space in the nacelle. In fact, the ventilations ducts are separated from this ambient air by the wall of the computer, this ambient air transferring heat to the wall by convection, which is then absorbed by the ventilation air flow circulating in the ventilation ducts. The ventilation system of a computer of the above-mentioned type therefore currently has to be oversized, for example while significantly increasing the ventilation air flow rate, in order to be sure that the computer is ventilated in an optimum manner. Moreover, even with such a system, the thermal margins on the computer may remain reduced, having a significant impact on the reliability of the electronic boards. 
         [0007]    In addition, the other equipment of the nacelle does not necessarily comprise dedicated ventilation systems, and therefore is subjected to the thermal environment of the nacelle. In turbine engines of which the equipment is arranged in a particular manner, it has been noted that active ventilation of the EEC computer brings about a tangential vortex in the annular space in the nacelle, which provides heat originating from the AGB and other heat sources to equipment that is sensitive to heat, and this is problematic. 
         [0008]    The present invention in particular provides a simple, effective and economical solution to at least some of these problems. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention proposes a piece of electronic equipment for a turbine engine, comprising a wall of which the inner surface defines at least one duct through which a ventilation air flow passes, the outlet of which leads onto an outer surface of the wall in order to discharge the ventilation air flow towards the outside of the equipment, characterised in that it comprises, in the region of this outlet, means for diverting and/or guiding at least some of the discharged air flow over at least part of said outer surface of the wall. 
         [0010]    According to the invention, the ventilation air flow which leaves the equipment is diverted and/or guided in order to sweep the equipment and thus improve the ventilation thereof. This air flow circulates on the wall of the equipment comprising or defining the outlet of the duct, and thus limits the heating of this wall by the ambient air flow around the equipment. This also makes it possible to reduce the temperature of the outlet of the duct. It is therefore conceivable either to increase the thermal margins on the computer by around ten degrees or to reduce the ventilation flow rate while retaining the previous margins. In the present application, thermal margin means the difference between the specification by the manufacturer defining the maximum permissible thermal resistance and a measurement made on an actual engine or in a laboratory. 
         [0011]    The equipment according to the invention is, for example, an on-board computer of the EEC type and comprises a housing comprising electronic boards, said wall covering the housing. 
         [0012]    The diverting and/or guiding means may comprise at least one member that is attached and fastened to the wall and/or the equipment, for example by bonding, brazing, welding, etc. This member or some members may be made of metal, plastics material or composite materials. 
         [0013]    According to an embodiment of the invention, the outlet of the duct is formed by a slot, the diverting and/or guiding means comprising at least one metal sheet which extends along the slot and covers said slot at least in part. The slot may be formed in the wall of the equipment or may be defined, in a mounting position of the wall, between a peripheral edge of this wall and an edge opposite the housing of the equipment. 
         [0014]    The metal sheet is inclined at least in part relative to the plane of the wall by an angle of between 30° and 60°, for example. This range of values makes it possible to limit the head losses of the ventilation air flow. The metal sheet may comprise a portion that is parallel to the plane of the wall. The metal sheet may extend at least in part within the duct. The metal sheet may be bent or swaged. 
         [0015]    The equipment according to the invention may comprise a second wall, opposite the first wall, the inner surface of this second wall also defining at least one duct through which a ventilation air flow passes, the outlet of which leads onto an outer surface of this second wall. Advantageously, this outlet does not comprise guiding and/or diverting means of the above-mentioned type, such that the direction of the air flow discharged by this outlet is substantially opposite that of the air flow discharged by the outlet in the first wall. 
         [0016]    The present invention also relates to a turbine engine, characterised in that it comprises at least one piece of equipment as described above. The turbine engine may comprise two pieces of equipment of this type, such as two EEC computers. 
         [0017]    The invention also relates to a kit for modifying a piece of electronic equipment for a turbine engine, with a view to improving the ventilation thereof, characterised in that it comprises means for diverting and/or guiding an air flow, such as at least one metal sheet, which are intended to be attached and fastened to the equipment, in the region of the outlet of a duct through which an air flow for ventilating the equipment passes, such that a ventilation air flow circulates on an outer surface of the equipment. This kit makes it possible to modify an existing piece of electronic equipment in a simple and rapid manner with a view to improving the ventilation thereof, which is more cost-effective than replacing the entire piece of equipment with another piece of equipment. 
         [0018]    The invention also relates to a method for modifying a piece of electronic equipment for a turbine engine, with a view to improving the ventilation thereof, characterised in that it comprises the steps consisting in attaching and fastening means for diverting and/or guiding an air flow, such as at least one metal sheet, to the equipment, in the region of the outlet of a duct through which an air flow for ventilating the equipment passes, such that a ventilation air flow circulates on an outer surface of the equipment. 
         [0019]    The invention lastly relates to a method for ventilating a nacelle of a turbine engine, this nacelle defining an annular space in which equipment is mounted, including at least one such piece of equipment as described above (of the type comprising a first and a second wall), characterised in that it consists in ventilating a circumferential portion of the annular space using the air flow discharged through the outlet in the first wall and ventilating the remaining circumferential portion of the annular space using the air flow discharged through the outlet in the second wall. 
         [0020]    This makes it possible to prevent a vortex from forming in the annular space in the nacelle, this annular space comprising two circumferential zones which are ventilated independently of one another and which may therefore have different temperatures. The EEC computer and other equipment that is sensitive to heat may thus be housed in a relatively cold zone that is different from the hotter zone in which the AGB gearbox is located. The invention thus makes it possible to predict in advance the ventilation air flows that will occur in the nacelle, and these air flows will therefore no longer be negatively affected, as they are in the prior art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0021]    The invention will be better understood and other details, features and advantages of the invention will emerge upon reading the following description given by way of non-limiting example and with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  is a partial schematic view of an aircraft turbine engine, this turbine engine being provided with a system for ventilating an on-board computer of the EEC type, 
           [0023]      FIG. 2  is a schematic perspective view of the on-board computer of the turbine engine in  FIG. 1 , 
           [0024]      FIG. 3  is a schematic sectional view of the on-board computer in  FIG. 2 , and shows the prior art for the invention, 
           [0025]      FIG. 4  is a schematic perspective sectional view along line IV-IV in  FIG. 3 , 
           [0026]      FIG. 5  is a schematic sectional view of an on-board computer according to the invention, 
           [0027]      FIG. 6  is a partial schematic sectional view of an on-board computer according to the invention, and shows a first embodiment of the invention, 
           [0028]      FIG. 7  is a larger-scale view of a part of  FIG. 6 , 
           [0029]      FIGS. 8 and 9  are views corresponding to  FIG. 7  and showing variants of the invention, 
           [0030]      FIG. 10  is a highly schematic cross-sectional view of a nacelle of a turbine engine according to the prior art, and 
           [0031]      FIG. 11  is a schematic cross-sectional view of a turbine-engine nacelle according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Reference is first made to  FIGS. 1 to 4 , which show the prior art for the invention,  FIG. 1  showing an aircraft turbine engine  10 , such as a bypass turbojet engine. This turbine engine typically comprises a nacelle  12  surrounding an engine (not shown) which comprises, from upstream to downstream (from right to left in  FIG. 1 ), in the direction of flow of the gases in the turbine engine, a fan, compression stages, a combustion chamber, turbine stages and an exhaust nozzle. 
         [0033]    The nacelle  12  comprises, at its upstream end, an air intake duct  14  and defines an annular space between an inner surface formed by an inner casing  16  and an outer surface formed by cowls  17 . Equipment and electronic modules, such as a computer  18  of the EEC type (electronic engine control), are mounted in this annular space. 
         [0034]    The air flow contained in the annular space in the nacelle  12  is relatively hot. The computer  18 , which comprises electronic boards having low thermal stability, therefore has to be ventilated by a system  20  that draws off colder air flowing along the nacelle. The drawn-off air has a temperature of between approximately 0 and 55 ° C. when the turbine engine is on the ground. 
         [0035]    The system  20  comprises a duct  22  for supplying the drawn-off air to the housing  24  of the computer, which comprises ducts  26 ,  26 ′ through which a ventilation air flow passes. 
         [0036]    The housing  24  of the computer comprises one or more digital inputs and one or more digital outputs. It has a general parallelepiped shape and comprises an upper wall  28  and a bottom or lower wall  29  ( FIG. 4 ) which each cover and define a plurality of ducts  26 ,  26 ′. In the example shown in  FIG. 4 , the ducts  26 ,  26 ′ are rectilinear and parallel, and are separated from one another by rectilinear fins  33 . 
         [0037]    The inlets  30  of the ducts  26 ,  26 ′ are connected to the air-supply duct  22  by a collector  31 . The outlets  32  of the ducts  26  lead onto the outer (upper) surface  34  of the wall  28 , and the outlets of the ducts  26 ′ lead onto the outer (lower) surface of the bottom wall  29 , in order to discharge the ventilation air flows towards the outside of the housing, into the annular space in the nacelle  12 . 
         [0038]    The ducts  26  may have a shared air outlet which is in the form of an elongate slot, as shown in  FIGS. 2 and 4 . The air flow leaving the ducts  26  has a temperature which is not generally greater than 90 ° C., while the air flow contained in the annular space may have a temperature of greater than 100 ° C. 
         [0039]    As can be seen in  FIG. 3 , the air flow which leaves the housing (arrow  35 ) mixes with the air  36  in the annular space. Moreover, the air  36  from the annular space transfers heat to the wall  28  by convection (arrow  38 ), which wall tends to heat the ventilation air flow flowing in the ducts  26 . 
         [0040]    The invention, of which the general principle is shown in  FIG. 5 , proposes diverting and/or guiding at least some of the air flow leaving the housing (arrow  35 ′) so that an air flow circulates on the outer surface  34  of the wall  28  (arrow  40 ). This air flow  40  is thus reused to ventilate the computer  18  from the outside, by allowing the heat exchanges by convection (arrow  38 ′) with the wall  28 . The air flow  40  thus protects the wall  28  from the air flow  36  by a “screen effect”. 
         [0041]    This is made possible by means for diverting and/or guiding at least some of the air flow leaving the ducts  26 , these means comprising one or more members that are attached and fastened to the wall  28  and/or the housing  24 , in the embodiments of the invention described in the following. 
         [0042]    In the embodiment shown in  FIGS. 5 to 7 , the outlet  32  of the ducts  26  is also in the form of a rectilinear elongate slot. Here, a diverting and guiding metal sheet  50  is attached and fastened to the wall  28 , for example by bonding, brazing or welding. 
         [0043]    The metal sheet  50  has a general elongate shape and extends along the outlet  32 . It has a length that is at least equal to that of the outlet  32 . In addition, it has a width or a transverse dimension that is greater than that of the outlet and covers said outlet completely, while allowing the ventilation air flow to be discharged between the metal sheet and the wall. 
         [0044]    The metal sheet  50  has a curved shape in section and comprises two adjacent longitudinal portions  52 ,  54  that are inclined relative to one another. A first longitudinal portion  52  has a longitudinal edge  56  that is connected to a longitudinal edge of the outlet  32 , and extends towards the outside of the housing  24  so as to be inclined relative to the plane P of the wall. As can be seen in  FIG. 7 , the portion  52  of the metal sheet is inclined by an angle α of between 30° and 60°, and for example 45°, relative to the plane P. This first portion  52  covers some of the width or transverse dimension of the outlet  32 . 
         [0045]    The longitudinal edge  58  opposite the first portion  52  is connected to one of the longitudinal edges of the second portion  54  of the metal sheet, which extends in parallel with the plane P and has a width l or transverse dimension such that the free longitudinal portion thereof covers, at a distance h, the wall  28  and defines an outlet for a ventilation air flow therewith which is oriented in parallel with the plane P (arrow  40 ). The height or distance h is preferably substantially equal to that h′ of the ducts  26 . For metal sheet  50  covers this outlet  32 , it is necessary in this case for the width l of the portion  54  to be such that: l+h/tangent (α)&gt;S, S being the width of the outlet. 
         [0046]    The variant in  FIG. 8  differs from the embodiment described above essentially in that the metal sheet  50 ′ comprises only one portion  52 , and therefore not the portion  54 . Owing to the absence of the portion  54 , the air flow leaving the ducts  26  (arrow  40 ′) has an orientation which depends on the angle α of inclination of the portion  52  relative to the plane P, this angle being approximately 45° here. 
         [0047]    In the variant of the invention shown in  FIG. 9 , two members  60 ,  62  are attached and fastened in the outlet of the ducts  26 . 
         [0048]    The first member is a metal sheet  60  which has a rectilinear elongate shape and of which one longitudinal edge  64  is connected to a longitudinal edge of the outlet  32 , this metal sheet  60  being inclined relative to the plane P of the wall  28  and extending towards the interior of the outlet  32  of the ducts  26 . The metal sheet  60  has a length that is less than or equal to that of the outlet  32  and has a width or transverse dimension that is less than that of the outlet. The metal sheet  60  has, for example, a width of between ¼ and ⅓ of that of the outlet. Moreover, the height h″ of the metal sheet  60  is between ⅓ and ½ of that of the ducts  26 . As can be seen in the figure, owing to the fact that the metal sheet  60  extends towards the interior of the outlet, it slightly reduces the outlet cross section of the ducts  26  and therefore makes it possible to accelerate the air flow at the outlet of said ducts. The metal sheet  60  is inclined by an angle α of between 30° and 60°, and for example of 45°, relative to the plane P. The outer surface of the metal sheet  60  defines a surface for guiding the air flow leaving the ducts  26 . 
         [0049]    The second member is an elongate bar  62  having a triangular cross section. This bar  62  is fastened by one  66  of its sides to the wall  28  or to the housing, along the outlet  32 , such that another  68  of the sides of the bar forms a surface for guiding the air flow leaving the ducts  26 , which is substantially parallel to the metal sheet  60 . The bar  62  has a length that is less than or equal to that of the outlet  32 , a width or transverse dimension that is between ¼ and ⅓ of that of the outlet  32  and a height H of between ½ and ⅔ of that of the ducts  26 . 
         [0050]    As in the embodiment in  FIG. 8 , the air flow leaving the ducts  26  (arrow  40 ″) has an orientation which depends on the angle α of inclination of the guide surfaces of the metal sheet  60  and of the bar  62  relative to the plane P, this angle being approximately 45° here. 
         [0051]    Each of  FIGS. 10 and 11  are schematic cross-sectional views of a turbine-engine nacelle. As explained above, this nacelle defines an internal annular space in which a plurality of pieces of equipment are mounted. The reference numerals  70 ,  72 ,  74  and  76  respectively denote exchangers, an AGB gearbox, a pressure sensor housing (PSS) and fans connected to two EEC computers  18 , these fans being intended to suck in air flowing on the outside of the nacelle in the above-mentioned duct  22 . The reference numeral  78  denotes the strut of the turbine engine and, lastly, the reference numeral  80  denotes a grating for discharging air from the inner space in the nacelle. 
         [0052]      FIG. 10  shows the prior art for the present invention. It is noted that the air flows  82  leaving the ventilation ducts defined by the wall  28  and the bottom wall  29  of each computer  18  are oriented substantially in the same tangential direction, and this generates a vortex  84  in the annular space, which provides heat originating from the AGB gearbox  72  and from the exchangers  70  to the fans  76  and to the PSS housing  74 . 
         [0053]    As shown in  FIG. 11 , the invention makes it possible to overcome this problem due to the fact that the air flows  82 ′,  82 ″ leaving the ventilation ducts defined by the wall  28  and the bottom wall  29  of each computer  18  are now oriented in substantially opposite tangential directions. This is made possible by the fact that means for diverting and/or guiding an air flow such as those described above are mounted at the outlet of the ducts through which a ventilation air flow passes on only one of the faces of each computer  18 . In the example shown, the outlet of the ducts defined by the bottom wall (radially inner wall) of each computer is not modified, the air flow leaving the ducts defined by the wall of each computer being diverted and/or guided, as described above. The air flows  82 ′ leaving the ducts defined by the bottom wall of each computer  18  circulate in a circumferential portion of the nacelle in order to ventilate the PSS housing  74 , and then are discharged through the grating  80 . The air flows  82 ″ leaving the ducts defined by the wall of each computer  18  circulate in the remainder of the nacelle in order to first ventilate the fan  76  and then to pass around the exchangers  70  and the gearbox  72  before being discharged through the grating  80 . The annular space in the nacelle therefore comprises two zones: one relatively cold zone in which the EEC computers  18  are located, and one relatively hot zone in which the gearbox  72  is located.