Abstract:
According to the invention, a scaled articulation device is mounted on at least one of the branches of a hot-air circulation circuit in the form of a bracket so as to provide a bracket with capabilities of deforming about the articulation device.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the deicing of air inlet cowls of turbine engines, in particular for aircraft. 
     BACKGROUND OF THE INVENTION 
     It is known that, if required (to prevent ice from forming or to eliminate ice which has already formed), the leading edge of the air inlet cowl of such turbine engines is deiced by heating using pressurized hot air bled from said turbine engine and supplied to said leading edge by a hot-air circulation circuit. Such a hot-air circulation circuit comprises, in a known manner, two branches forming a right-angled structure, namely a transverse branch connected to said turbine engine and a longitudinal branch arranged laterally with respect to said turbine engine and connected to an injector in contact with said leading edge. 
     However, the hot air bled from the turbine engine is at a high temperature, for example around 500° C., and at a high pressure too, for example around 10 to 20 bar. As a result, the right-angled branches of said hot-air circulation circuit, which are embodied as steel tubes, are subjected to considerable variations in length through the temperature effect, and possibly pressure effect, of said hot air. Consequently, the rigid right-angled structure formed by said transverse and longitudinal branches tends to deform, and the means for fastening said hot-air circulation circuit to said air inlet cowl and the means for bleeding pressurized hot air from the turbine engine experience considerable stresses, possibly damaging them or destroying them. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to overcome this disadvantage. 
     To this end, according to the invention, the system for deicing the hollow leading edge of an air inlet cowl for a turbine engine, in particular for an aircraft, said deicing system comprising:
         an injector designed to inject pressurized hot air inside said hollow leading edge;   means for bleeding off pressurized hot air that are mounted on the hot-stream generator of said turbine engine;   a hot-air circulation circuit for conveying said pressurized hot air from said bleed means to said injector, said hot-air circulation circuit comprising two branches forming a right-angled structure, namely:
           a transverse branch whose end is rigidly connected to said bleed means, and   a longitudinal branch which is arranged laterally with respect to said turbine engine and whose end is connected to said injector; and   
           fastening means arranged in the region of said injector and intended to fasten said longitudinal branch to said air inlet cowl,
 
is distinguished in that a sealed articulation device is mounted on at least one of said branches of said hot-air circulation circuit to provide said right-angled structure with capabilities of deforming about said articulation device.
       

     Thus, by virtue of said sealed articulation device or devices, the right-angled structure formed by said transverse and longitudinal branches can itself deform during variations in length of said branches through the temperature effect and/or pressure effect of said hot air, said branches adapting their relative position to their actual lengths without applying excessive stresses to the means for fastening said hot-air circulation circuit. 
     The sealed articulation device or devices can be of any known type, such as the flexible sleeve type, bellows type, etc. However, each sealed articulation device is preferably of the swivel joint type. 
     To further increase the capabilities of said hot-air circulation circuit deforming about said articulation or articulations, it is advantageous for each of them to comprise two swivels spaced apart along said corresponding branch of the hot-air circuit. 
     Of course, said hot-air circulation circuit according to the present invention can be formed by a simple pipe. However, given the high temperature of the hot air which passes through it, said circuit radiates heat which can damage certain structures of said air inlet cowl that are in the vicinity of said hot-air circulation circuit. In addition, for obvious safety reasons, it is advantageous to provide a protection for said surrounding structures, in the event of leaks of pressurized hot air or in the event of a breakage in said pipe. 
     Hence, according to a key feature of the present invention whereby the latter disadvantages can be avoided, an external protective casing is provided both on the transverse branch and on the longitudinal branch of said hot-air circulation circuit. 
     Thus, in an advantageous embodiment, each articulated branch of said hot-air circulation circuit comprises an internal hot-air-ducting element, provided with said sealed articulation device, and an external protective casing element surrounding said internal element, said external element being provided with a conjoint articulation device arranged and produced in correspondence with said sealed articulation device of said internal element. 
     In this latter embodiment, it is advantageous, for reasons of checking and carrying out maintenance on the sealed articulation device of said internal element, that said external protective casing element is removable. To this end, at least one of the articulation devices of the internal element and of the external element can be of the detachable swivel joint type. For the latter purpose, the articulation device in question can comprise a swivel cooperating with a cylindrical surface. 
     Experience has shown that, to achieve the result aimed for by the present invention, it is sufficient in most cases for only said transverse branch of said hot-air circulation circuit to be articulated. 
     In a first preferred embodiment of the deicing system according to the present invention:
         said longitudinal branch of the hot-air circulation circuit is constituted by an internal hot-air-ducting element and by an external protective casing element surrounding said internal element;   one of the two internal and external constituent elements of said longitudinal branch is longitudinally rigid, whereas the other of said constituent elements comprises at least two parts which are nested one inside the other and which are capable of sliding with respect to one another in a sealed manner;   the two constituent elements of said longitudinal branch are secured to one another at their two ends;   in the region of said injector, the two constituent elements are rigidly connected in common to said fastening means; and   in the region of said transverse branch, on the one hand, said internal hot-air-ducting elements of said longitudinal and transverse branches are secured to one another and, on the other hand, said external protective casing elements of said longitudinal and transverse branches are likewise secured to one another.       

     By virtue of such an arrangement, that one of said elements of said longitudinal branch which is rigid serves as a tie bar for the other one of these elements that is constituted by said nested and sliding parts, such that the elongation of said longitudinal branch through the pressure effect of the hot air is in practice limited to the elongation of said rigid element through the temperature effect of said hot air. It is thus possible to limit the deformation of the right-angled structure formed by said transverse and longitudinal branches, and hence the degree of rotation of said articulation devices of the internal element and of the external element of said transverse branch. 
     In a second preferred embodiment of the deicing system according to the present invention, employing such an elongation-limiting feature:
         said longitudinal branch of the hot-air circulation circuit comprises at least two sections mounted one at the end of the other;   each of said sections is constituted by an internal hot-air-ducting element and by an external protective casing element surrounding said internal element;   one of the constituent elements of each of said sections is longitudinally rigid, whereas the other of said constituent elements comprises at least two parts which are nested one inside the other and which are capable of sliding with respect to one another in a sealed manner;   the two constituent elements of each of said sections are secured to one another at their two ends;   the two sections of said longitudinal branch are joined together so as to connect their constituent elements, respectively;   in the region of said injector, the two constituent elements of one of the two sections are rigidly connected in common to said fastening means; and   in the region of said transverse branch, on the one hand, said internal hot-air-ducting elements of the other of said sections and of the transverse branch are secured to one another and, on the other hand, said external protective casing elements of said other section and of said transverse branch are likewise secured to one another.       

     Moreover, it is advantageous that, in the region of said injector, said fastening means comprise a partition which closes off said hollow leading edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures of the appended drawing will give a clear understanding of how the invention can be implemented. In these figures, identical references denote like elements. 
         FIG. 1  is an exploded schematic view of a turbine engine, on which are represented the air inlet cowl and its deicing system. 
         FIG. 2  is an enlarged view in part section of said air inlet cowl taken on line II-II of  FIG. 1 . 
         FIG. 3  schematically shows a first exemplary embodiment of said deicing system. 
         FIG. 4  schematically illustrates the deformation of the deicing system of  FIG. 3  when said system is traversed by pressurized hot air. 
         FIG. 5  schematically shows in section an exemplary embodiment of the articulation of the deicing system of  FIG. 3 . 
         FIGS. 6 and 7  schematically show a second and third exemplary embodiment of said deicing system, respectively. 
         FIGS. 8 and 9  schematically show in section two exemplary embodiments of the articulation for the deicing systems of  FIGS. 6 and 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The bypass engine  1  represented schematically in  FIG. 1  has a longitudinal axis L-L and comprises, in a known manner, a central hot-air generator  2 , a fan  3  and compressor stages  4 . The engine  1  is assigned, and has fastened to it, a nozzle assembly  5 , two lateral cowls  6  and  7  and an air inlet cowl  8 . 
     As is illustrated schematically by  FIGS. 1 and 2 , the air inlet cowl  8  comprises an internal lateral longitudinal duct  9  provided, at its rear end directed toward the engine  1 , with a coupling element  10  and, at its front end housed in the hollow leading edge  11  of said air inlet cowl, with an injector  12 . Furthermore, a compressor stage  4  of the engine  1  has a pressurized hot-air intake  13  arranged on it which is connected to an internal transverse duct  14 , itself connected by an elbow  15  and by cooperating coupling elements  16 ,  17  to a longitudinal duct  18 , housed between the fan  3  and the lateral cowl  6 . At the opposite end to the coupling element  17 , the longitudinal duct  18  is provided, facing the coupling element  10  of the longitudinal duct  9 , with a complementary coupling element  19 . 
     Thus, when the complementary coupling elements  16  and  17 , on the one hand, and  10  and  19 , on the other hand, are connected to one another, the ducts  9 ,  14  and  18  constitute a hot-air circulation circuit forming a right-angled structure comprising a transverse branch  14  and a longitudinal branch  9 ,  18 , and the circuit is traversed by hot air (for example at a temperature of 500° C.) bled at  13  from the engine  1  and conveyed to the injector  12 . Said injector can thus blow this pressurized hot air (dotted arrows  20 ) inside the leading edge  11  in order to deice it. At least one orifice  21  is provided in the external surface of the cowl  8  in order to discharge to the free air (arrows  22 ) the hot air having circulated inside the leading edge  11  (then, for example, at a temperature of 200° C.). 
     As is shown in detail and on a larger scale in  FIG. 2 , the hollow leading edge  11  is closed on the rear side by an internal annular partition  23 , such that an annular peripheral chamber  24  is formed inside said leading edge  11 . The injector  12  and the corresponding end of the longitudinal duct  9  are fastened to the internal partition  23 , and said injector, arranged in said annular chamber  24 , injects pressurized hot air  20  therein. The orifice  21  places said annular chamber  24  in communication with the outside. 
     On the opposite side to the leading edge  11 , the air inlet cowl  8  is closed off by an internal annular partition  25 , through which the end of the longitudinal duct  9  which bears the coupling element  10  passes freely by sliding. 
     As is illustrated schematically by  FIG. 3 , the right-angled hot-air circulation circuit  9 ,  14 ,  18  is thus fastened to the engine  1 , at its ends, by way of the pressurized air intake  13  and the partition  23  and supported in a sliding manner by the partition  25  and, if appropriate, other intermediate means  26 , for example articulated connecting rods which are not otherwise shown. 
     According to the present invention, an articulation device  27  is mounted on the transverse branch  14  and this device comprises two spaced-apart swivels  28 ,  29  respectively mounted at the ends of a duct section  30  interposed in the duct  14 . The swivels  28 ,  29  respectively cooperate with spherical seats  31 ,  32  secured to the duct  14 . 
       FIG. 5  illustrates a practical exemplary embodiment of the articulation device  27 . In this example, sealing bellows  33 ,  34 , respectively between the swivel  28  and the seat  31  and between the swivel  29  and the seat  32 , have been provided. 
     It will be readily understood that, in an equivalent manner to what has been described above, the swivels  28 ,  29  could be secured to the duct  14 , while the spherical seats  31 ,  32  would be secured to the duct section  30 . 
     As is illustrated schematically in  FIG. 4 , when the hot-air circulation circuit is traversed by the hot air, the transverse branch  14  experiences a transverse elongation with respect to the turbine engine  1 , depicted by the arrow  35 , while the longitudinal branch  9 ,  18  experiences a longitudinal elongation depicted by the arrow  36 . Owing to the presence of the articulation device  27 , the right-angled structure formed by said branches  14  and  9 ,  18  then deforms, thereby avoiding excessive stresses being applied to the pressure intake  13  and to the partition  23 . 
     In the deicing system shown schematically by  FIG. 6 , the elements  4 ,  9 ,  10 ,  12  to  20 ,  23  and  25  to  27  described in relation to  FIG. 3  appear once again. However, in the system of  FIG. 6 :
         the longitudinal duct  9  is composed of two elements  9   a ,  9   b  which are nested telescopically and in a sealed manner one inside the other, the element  9   a  being secured to the partition  23  and to the injector  12 , whereas the element  9   b  is connected to the coupling element  10 ;   the longitudinal duct  18  is composed of two elements  18   a ,  18   b  which are nested telescopically and in a sealed manner one inside the other, the elements  18   a  and  18   b  being respectively connected to the coupling elements  19  and  17 ;   the longitudinal duct  9   a ,  9   b  is surrounded by a longitudinally rigid external protective casing  37  secured, on one side, to the partition  23  and, on the other side, to the coupling element  10 ;   the external protective casing  37  passes freely through the partition  25  by sliding;   the longitudinal duct  18   a ,  18   b  is surrounded by a longitudinally rigid external protective casing  38  secured, on the one side, to the coupling element  19 , and, on the other side, to the coupling element  17 ;   the external protective casing  38  is free to slide with respect to the intermediate support means  26 ; and   the transverse duct  14  is surrounded by a longitudinally rigid external protective casing  39  secured, on the one side, to the coupling element  16  and, on the other side, to the pressurized hot-air intake  13 , said external protective casing  39  being provided with a conjoint articulation device  40  arranged and produced in correspondence with the articulation device  27 .       

     In the variant embodiment shown in  FIG. 7 , the external protective casing  39  and the articulation device  40  appear once again. The differences over the system shown in  FIG. 6  are as follows:
         the coupling elements  10  and  19  have been dispensed with;   the external protective casings  37  and  38  have been replaced by a single longitudinally rigid external protective casing  41  secured, on the one side, to the partition  23  and, on the other side, to the coupling element  17 ; and   the internal elements  9   a ,  9   b  and  18   a ,  18   b  of the longitudinal ducts  9  and  18  have been replaced by a single internal hot-air-ducting element comprising two parts  42   a ,  42   b  which are nested one inside the other and which are capable of sliding with respect to one another in a sealed manner, the part  42   a  being connected to the injector  12  and the part  42   b  being connected to the coupling element  17 .       

       FIG. 8  shows an example of a combined articulation system  43 , comprising conjoint articulation devices  27  and  40  for the deicing systems shown in  FIGS. 6 and 7 . 
     In the combined articulation system  43 , the articulation device  27  is identical to that described in relation to  FIG. 5 . As for the articulation device  40 , it comprises two spaced-apart swivels  44 ,  45  respectively mounted at the ends of a protective casing section  46  which is interposed in the protective casing  39  and which encases the duct section  30 . The swivels  44 ,  45  respectively cooperate with cylindrically open seats  47 ,  48  secured to said protective casing  39 . 
     It will be readily understood that, by providing coupling means  49  (for example of the type designated by the reference  53  in  FIG. 9 ) on the internal protective casing  39 , upstream and/or downstream of the articulation devices  27  and  40 , it is possible to detach the assembly  44 ,  45 ,  46  from the cylindrical seats  47 ,  48  and hence gain access to the articulation device  27 , for example for a maintenance operation. 
       FIG. 9  shows a variant  50  of the conjoint articulation system  43  shown in  FIG. 8 . In this variant  50 , an articulation device  51 , similar to the articulation device  40 , is interposed in the duct  14 , while an articulation device  52 , similar to the articulation device  27 , is interposed in the protective casing  39  by way of at least one quick coupling  53 . 
     In the variant  50  of the articulation system, the articulation device  51  is both easily accessible and removable.