Abstract:
The invention is a turbofan provided with a pre-cooler. In order to evacuate the heated cool air stream, at least one discharge pipe is arranged in a chamber and connects the pre-cooler to at least one discharge orifice provided in the inner fairing, in output of an exhaust nozzle and at least more or less opposite the wing.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to a bypass turbine engine provided with a pre-cooler. 
     BACKGROUND OF THE INVENTION 
     It is known that, on board an aircraft, it is necessary to have hot air available to perform certain functions, such as air conditioning in the cockpit and the passenger cabin or for deicing certain parts of the aircraft. 
     It is also known that this hot air is taken from the turbojet engines of the aircraft and has to be cooled significantly before it can be used. To do this, a heat exchanger is provided, this generally being known as a pre-cooler, in which the hot air bled from the central generator of the turbojet engine is cooled by cold air from the fan duct. 
     Of course, during this heat exchange process, not only is the hot air bled from the central generator cooled by the cold air of the fan duct, but also this cold air is heated up by said hot air. It is therefore necessary to discharge this heated cold air to the outside. 
     In general, this heated cold air is discharged to the outside at the upper part of the engine suspension pylon, in front of the leading edge of the wind structure, and this leads to turbulence and aerodynamic disturbances that increase the drag of the aircraft. 
     To avoid this disadvantage, American document U.S. Pat. No. 5,729,969 proposes discharging the heated cold air into the annular cross section chamber formed between the central hot stream generator and the inner fairing of the fan duct, which chamber is then equipped with at least one ejection orifice directed toward said cold stream. However, an arrangement such as this carries the risk of disturbing the thermal regulation of the hot stream generator and therefore of accelerating turbine engine wear. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to remedy the disadvantages of the prior art. 
     To these ends, according to the invention, the bypass turbine engine for an aircraft comprising:
         a hollow nacelle of longitudinal axis provided with an air inlet at the front and with a jet pipe at the rear;   a central hot-stream generator, positioned axially in said nacelle;   a fan positioned in said nacelle forward of said central generator and able to generate the cold stream for said turbine engine;   an outer fairing borne internally by said nacelle and an inner fairing surrounding said central generator, said outer and inner fairings between them forming a fan duct of annular cross section for said cold stream, said inner fairing delimiting with said central generator a chamber of annular cross section surrounding said central generator; and   a pre-cooler receiving a current of hot air bled from said central generator and a current of cold air bled from said cold stream so as to generate a current of cooled hot air intended for performing functions on board the aircraft, such as air conditioning or deicing, said pre-cooler at the same time generating a current of heated cold air,
 
is notable in that, in order to discharge said current of heated cold air it comprises at least one discharge pipe positioned in said chamber and connecting said pre-cooler to at least one discharge orifice made in said inner fairing where said jet pipe leaves the nacelle, and facing upward at least approximately toward said wing.
       

     Thus, by virtue of the present invention, said heated cold air is discharged into said cold stream at the exit from said turbine engine—and therefore without causing turbulence and aerodynamic disturbances and without disturbing said cold stream inside the fan duct—while at the same time being isolated from the atmosphere in said chamber by said discharge pipe—and therefore without disrupting the thermal regulation of said central hot stream generator. 
     Furthermore, it will be noted that said discharge orifice thus lies in the upper region of the turbine engine which is intentionally devoid of any equipment so as to prevent any fire in the turbine engine from spreading to the wing of the aircraft through said suspension pylon. It is therefore advantageous for said discharge pipe to be housed at least in part in the upper part of said chamber. It will also be noted that positioning said heated cold air discharge pipe in the upper region of said turbine engine does nothing to exacerbate the situation should the turbine engine catch fire. In any event, this discharge pipe may advantageously be made of a refractory material able to withstand high temperatures, for example a ceramic of said turbine engine. 
     In the usual way, said pre-cooler may also be positioned in the upper part of said turbine engine. However, by virtue of said discharge pipe, it may be housed in numerous other different locations of said turbine engine. 
     For example, in the known way, said pre-cooler may be positioned in the fan duct. It may then be immersed in the cold stream from the fan and experience the direct action of this stream. As an alternative, a scoop may be provided carrying some of said cold stream to said pre-cooler. This alternative form is particularly advantageous because it allows a regulating valve to be positioned between said scoop and said pre-cooler, so that the temperature of the current of cooled hot air can be regulated, at least in part, by adjusting the intake of cold air into the pre-cooler. 
     In another embodiment, said pre-cooler may be positioned in said chamber surrounding the central generator. In this case, in order to carry the current of cold air to said pre-cooler, at least one bleed pipe is provided, this being positioned at least partially in said chamber and connecting said pre-cooler to at least one bleed orifice made in said inner fairing. It is then advantageous for said bleed orifice to be equipped with a scoop for bleeding cold air from said cold stream. 
     An embodiment such as this has the advantage that a regulating valve can be mounted on said bleed pipe to allow, at least partial, regulation of the temperature of the current of hot air cooled by the intake of cold air into said pre-cooler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures of the attached drawing will make it easy to understand how the invention may be embodied. In these figures, identical references denote elements that are similar. 
         FIG. 1  illustrates, in schematic axial section, a first embodiment of the bypass turbine engine according to the present invention. 
         FIG. 2  schematically and in perspective shows an exemplary embodiment of a pre-cooler for the turbine engine of  FIG. 1 . 
         FIGS. 3 and 4  illustrate, in views similar to  FIG. 1 , two alternative forms of embodiment of the turbine engine according to the present invention. 
         FIG. 5  schematically and in perspective shows one exemplary embodiment of the pre-cooler for the turbine engines of  FIGS. 3 and 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The bypass turbine engine shown by each of  FIGS. 1 ,  3  and  4  comprises a hollow nacelle  1  of longitudinal axis L-L provided with an air intake  2  at the front and with a jet pipe  3  at the rear. Said hollow nacelle  1  internally bears a fairing  4 , preferably at least partially coated with acoustic attenuation coatings  5  intended to reduce the internal noise of said turbine engine. 
     Positioned inside the hollow nacelle  1  are:
         a central hot stream generator  6  comprising, in the known way, low-pressure and high-pressure compressors, a combustion chamber and low-pressure and high-pressure turbines, and which generate the axial hot stream  7  of said turbine engine;   a fan  8  positioned in front of said central generator  6  and generating the annular cold stream  9  for said turbine engine; and   an inner fairing  10  surrounding said central generator  6  and forming, between itself and the casing  11  of this generator, a chamber  12  of annular cross section surrounding said generator.       

     The inner fairing  10  and the fairing  4 , external to it, between them form a fan duct  13  of annular cross section surrounding the central generator  6  and through which the cold stream  9  flows. 
     Formed between the inner fairing  10  and the central generator  6  are, at the front, an annular air intake slot  14  and, at the rear, an annular air discharge slot  15 . Thus, the chamber  12  can be swept by a current of cold air f, bled from the cold stream  9  at the front slot  14  and discharged into the hot stream  7  at the rear slot  15 , this current of cold air f providing temperature regulation for the central generator  6 . 
     Furthermore, in the usual way, the nacelle  1  is supported by a wing  16  of the aircraft (this wing is depicted in part) via a suspension pylon  17 . 
     In the embodiment of the invention that is illustrated by  FIG. 1 , a pre-cooler  18  is provided, this being positioned in the upper part  13 S of the fan duct  13 . This pre-cooler  18  is supplied with hot air  19 , from the central generator  6 , by a pipe  20  on which there is a hot-air-regulating valve  21 . The cooled hot air  22  generated by the pre-cooler  18  is sent to the user equipment (not depicted) through a pipe  23  which passes through the suspension pylon  17  and may be provided with a regulating valve  23 V. For its part, the heated cold air  24  generated by the pre-cooler  18  is discharged into the cold stream  9 , at the outlet of the jet pipe  3 , by a discharge pipe  25  positioned in the annular cross section chamber  12  and connecting the pre-cooler  18  to a discharge orifice  26  made in the inner fairing  10  behind said jet pipe  3 , and facing upward at least approximately toward the wing  16  and the pylon  17 , that is to say at the upper part of said inner fairing  10 . 
     The pipe  25  is made of a refractory material able to withstand high temperatures, for example of ceramic, and is preferably completely positioned in the upper part  12 S of the chamber  12 . 
     The pre-cooler  18  may have the known structure depicted in  FIG. 2 . In the exemplary embodiment of this  FIG. 2 , the pre-cooler  18  comprises a collection  27  of exchanger tubes which are supplied in common with hot air  19  by the pipe  20  and which are cooled by the cold stream  9  passing through said collection  27 . Said exchanger tubes are connected in common to the pipe  23  through which the current of cooled hot air  22  flows. 
     The collection of exchanger tubes  27  has, for example, the shape of the stem of a boat and is closed off at the rear by a partition wall  28  so as to form a cavity  29  entered by that part of the cold stream  9  that has passed through said collection  27  and been heated up by the exchanger tubes thereof to form the current of heated cold air  24 . The pipe  25  for discharging the current  24  communicates with the cavity  29  via an opening  30  thereof, so that it can carry said current  24  as far as the orifice  26 , through the upper part  12 S of the chamber  12 . 
     In the embodiment of the invention illustrated by  FIG. 3 , we again see all the elements that bear the references  1  to  12 ,  12 S,  13 S,  13  to  17 ,  19  to  26  and  23 V and which have been described hereinabove with reference to  FIG. 1 . However, by comparison with the embodiment of the latter figure, the pre-cooler  18  has been replaced by a pre-cooler  31 , an exemplary embodiment of which is illustrated by  FIG. 5 . In addition, on the fan  8  side, there is a scoop  32  able to bleed some of the cold stream  9  and carry it to the pre-cooler  31  along a pipe  33  provided with a regulating valve  34 . 
     In the example of  FIG. 5 , the pre-cooler  31  comprises a collection of exchanger tubes  35  which are supplied in common with hot air  19  by the pipe  20  and which are cooled by that part of the cold stream  9  that is picked up by the scoop  32  and carried by the pipe  33 . Said exchanger tubes of the collection  35  are connected in common to the pipe  23  through which the current of cooled hot air  22  flows. 
     The collection of exchanger tubes  35  forms one wall of an enclosure  36  entered by said part of the cold stream  9 , picked up by the scoop  32 , that has passed through said collection  35  and forms said current of heated cold air  24 . The pipe  25  for discharging the current  24  communicates with the enclosure  36  via an opening  37  thereof, so that it can carry said current  24  as far as the orifice  26  through the upper part  12 S of the chamber  12 . 
     In the embodiment of the invention illustrated by  FIG. 4 , we again find all the elements bearing the references  1  to  12 ,  12 S,  13 S,  13  to  17 ,  19 ,  20  and  22  to  26  and which were described with reference to  FIG. 1 . In this embodiment, the valves  21  and  23 V have been omitted, although they could be present. In addition, by comparison with the embodiment of this  FIG. 1 , the pre-cooler  18  housed in the upper part  13 S of the fan duct  13  has been replaced by a pre-cooler  38  housed in the upper part  12 S of the chamber  12 . This pre-cooler may be of a similar type to the pre-cooler  31  of  FIG. 5 . 
     A bleed pipe  39 , positioned at the upper part  12 S of the chamber  12 , connects the pre-cooler  38  to a bleed orifice  40  made in the forward part of the inner fairing  10 . Said bleed orifice  40  is provided with a scoop  41 . Thus, part of the cold stream  9 , picked up by the orifice  40  and the scoop  41 , is carried to the pre-cooler  38  to cool the current of hot air  19  and generate the current of cooled hot air  22  and the current of heated cold air  24 . The latter is discharged from the pre-cooler  38  via the pipe  25  which carries it to the orifice  26 . 
     A regulating valve  42  is mounted on the bleed pipe  39  to control the intake of cold air and therefore the temperature of the current of cooled hot air  22 .