Abstract:
The present disclosure provides a nozzle for an aircraft turboprop engine with an unducted fan, including: an inner wall, an outer wall radially spaced apart from the inner wall and concentric with the inner wall, a junction area of the inner and outer walls including an opening contained in a plane transverse to a longitudinal axis of the nozzle. In particular, the junction area of the inner and outer walls includes two connecting plates and a member to secure the two connecting plates together, or in another form, the junction area includes a pad secured to the inner wall, and a pad secured to the outer wall, facing the pad of the inner wall of the nozzle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/FR2014/050919, filed on Apr. 15, 2014, which claims the benefit of FR 13/53391, filed on Apr. 15, 2013. The disclosures of the above applications are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to aircraft turboprop engines with unducted fans, and more particularly to a rotary nozzle for such turboprop engines. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Referring to  FIG. 1  of French Patent No. 1 152 078, a turboprop engine with an unducted fan comprises a turboprop engine  1  and an annular nacelle  3 , disposed coaxially with respect to the turboprop, around a longitudinal axis  5  of the turboprop engine. 
         [0005]    The turboprop engine  1  comprises, from the upstream (on the left on  FIG. 1 ) towards the downstream (on the right on  FIG. 1 ) in the flow direction of the air, a compressor, a combustion chamber, a turbine with two counter-rotating rotors (these elements, housed in the nacelle  3 , are not visible on this figure) and a nozzle  7  for ejecting the air flow crossing the turboprop engine. These upstream and downstream rotors each drive in rotation around the longitudinal axis  5  an upstream  9   a  and downstream  9   b  assembly of fan blades  9  located downstream of the turboprop engine  1 . 
         [0006]    The nozzle  7  for ejecting the air flow is called rotary, in that it is movable in rotation around the longitudinal axis  5  of the turboprop engine  1 , with respect to a gas ejecting cone  10  substantially concentric with the nozzle  7 . To this end, and as is visible more particularly on  FIG. 2  schematically illustrating the nozzle  7  in longitudinal section, the upstream section  11  of the nozzle  7  is connected to a set of flanges  12 ,  13  respectively secured to the downstream rotor of the turboprop engine turbine (not represented) and rotary cowls assembled around fan blades  9   b  (visible on  FIG. 1 ). 
         [0007]    As represented on  FIG. 2 , the nozzle  7 , has a substantially triangular longitudinal section. The nozzle  7  comprises an inner wall  15  and an outer wall  17 , each typically produced in Inconel. 
         [0008]    The inner  15  and outer  17  walls are connected to each other thanks to a circular welding  19  extending over the entire circumference of the nozzle and defining an annular junction area  21  between the inner and outer walls downstream of the nozzle. 
         [0009]    According to another type of nozzle, such as that illustrated on  FIG. 3  representing a non-rotary nozzle for ejecting the primary air flow of a by-pass turbojet engine, the junction area between the inner  15  and outer  17  walls of the nozzle  7  comprises an annular wedge  23  disposed at the downstream section of the nozzle, between said inner and outer walls. The annular wedge  23  is sandwiched between the inner and outer walls. The annular wedge  23  is brazed on the inner wall  15  and assembled by riveting on the outer wall  17 . 
         [0010]    The purpose of the rotary and non-rotary nozzles allows the ejection of the hot air flow emanating from the turboprop engine. 
         [0011]    However, whatever the type of nozzle retained, these nozzles generally have an annular junction area at the downstream section thereof. The hot air flow flowing along the inner wall of the nozzle diffuses heat between the inner and outer walls of the nozzle, thus leading to limiting the cooling capacities of the engine. 
         [0012]    U.S. Pat. No. 2,599,879 provides an annular junction area between the inner and outer walls of the nozzle, constituted by an annular partition having openings through which ducts pass in which cold air circulates. 
         [0013]    The advantage of this solution is to refresh the engine. However, the setting up of these ducts is particularly complex and considerably increases the mass of the nozzle. 
       SUMMARY 
       [0014]    The present disclosure provides a nozzle for an aircraft turboprop engine with an unducted fan, comprising:
       an inner wall,   an outer wall distant radially from said inner wall and concentric with said inner wall,   a junction area of said inner and outer walls comprising at least one opening contained in a plane substantially transverse to a longitudinal axis of said nozzle,       
 
         [0018]    said nozzle being characterized in that the junction area of the inner and outer walls further comprises means selected from the following group comprising:
       means for connecting the walls of the nozzle, said means comprising, on the one hand, at least two connecting plates, and other hand, means for securing said plates together, or   at least one pad secured to the inner wall and at least one pad secured to the outer wall of the nozzle and positioned facing said at least one pad of the inner wall of the nozzle.       
 
         [0021]    By providing one or several openings in the junction area of the inner and outer walls of the nozzle, ventilation between said inner and outer walls is created, thus allowing providing a good ventilation of the engine. 
         [0022]    By providing a junction area of the inner and outer walls comprising either means for connecting the walls of the nozzle, said means comprising, on the one hand, at least two connecting plates and, on the other hand, means for securing said plates together, either or at least one pad secured to the inner wall and at least one pad secured to the outer wall of the nozzle and positioned facing said pad of the inner wall of the nozzle, the nozzle comprising neither a circumferential annular junction area, nor pipes for cold air circulation. 
         [0023]    As a result, the mass of the nozzle is reduced considerably while providing improved ventilation of the engine. 
         [0024]    By thus reducing the mass of the nozzle, the fuel consumption of the propulsion assembly is also reduced. 
         [0025]    According to a first form of the present disclosure, each of the walls of the nozzle comprises at least one metallic skin made of an austenite nickel-chromium based superalloys, for example Inconel. 
         [0026]    The connecting means are distributed discretely on the circumference of the nozzle, between the inner and outer walls of the nozzle. 
         [0027]    According to a second form of the present disclosure, the inner wall of the nozzle is constituted by a metallic skin made of an austenite nickel-chromium based superalloys, for example Inconel, and the outer wall of the nozzle is constituted by a skin in titanium. 
         [0028]    This advantageously allows reducing the mass of the nozzle all the more with respect to the first form of the present disclosure. 
         [0029]    According to other features, the pads of the inner wall have an abutment thereon, for example of carbon, thus inhibiting direct contact between the pads of the inner and outer walls, thus reducing the chance of premature wear of said pads. 
         [0030]    According to a common variant to the two forms of the present disclosure, the inner wall comprises at least one annular stiffener positioned facing at least one annular stiffener of the outer wall, so as to improve the structural hold of the nozzle. 
         [0031]    In one form, the junction area of the inner and outer walls is located at a downstream section of the nozzle. 
         [0032]    According to the present disclosure, the metallic skin in Inconel of the inner and outer walls is obtained by a forging-die-stamping method, thus allowing very advantageously to do without longitudinal welding for forming each of the walls, but also the circular welding for assembling the parts constituting the walls. By producing the nozzle thanks to such a method, the mass of the nozzle is further reduced. 
         [0033]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0034]    In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
           [0035]      FIG. 1  illustrates a turboprop engine with an unducted fan known from the prior art; 
           [0036]      FIG. 2  is a schematic view in longitudinal section of the rotary nozzle according to the prior art; 
           [0037]      FIG. 3  is a schematic view in longitudinal section of a portion of a non rotary nozzle according to the prior art; 
           [0038]      FIG. 4  illustrates a portion of the nozzle according to a first form of the present disclosure; 
           [0039]      FIG. 5  is a detailed view of the junction area of the inner and outer walls of the nozzle; 
           [0040]      FIG. 6  illustrates a cross-section according to line  6 - 6  of the nozzle of  FIG. 4 ; 
           [0041]      FIG. 7  represents a portion of the nozzle according to a second form of the present disclosure; 
           [0042]      FIG. 8  illustrates a cross-section according to line  8 - 8  of the nozzle of  FIG. 7 ; 
           [0043]      FIG. 9  is a sectional view according to line  9 - 9  of  FIG. 8 ; and 
           [0044]      FIG. 10  illustrates the nozzle of the second form of the present disclosure, seen from the longitudinal axis of the nozzle. 
       
    
    
       [0045]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
       DETAILED DESCRIPTION 
       [0046]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0047]    Referring to  FIG. 4 , a nozzle produced according to a first form of the present disclosure is illustrated as reference numeral  7 . 
         [0048]    The nozzle  7  comprises an inner wall  15  and an outer wall  17 , typically produced in a material offering a good mechanical resistance at temperatures of around 600° Celsius at the inner wall, and of around 300° Celsius at the outer wall. 
         [0049]    To this end, the inner and outer walls are constituted by metallic skins in Inconel, a material having an acceptable mechanical resistance up to 800° Celsius. 
         [0050]    The upstream section  11  of the nozzle is connected to a set of flanges  12 ,  13  respectively secured to the downstream rotor of the turbine of the turboprop engine (not represented) and rotary cowls assembled around blades of a downstream fan. By way of example, the inner wall  15  is bolted on the flange  12  and the outer wall  17  is screwed on the flange  13 . 
         [0051]    According to the present disclosure, the downstream section  25  of the nozzle  7  comprises a junction area  27  of the inner and outer walls. 
         [0052]    This junction area of the inner  15  and outer  17  walls comprises means for connecting walls of the nozzle, constituted by a plurality of connecting plates  29 ,  31 . 
         [0053]    The connecting plates  29  are secured to the inner wall  15  and oriented in the direction of the inside of the nozzle  7 , and the connecting plates  31  are secured to the outer wall  17  and oriented in the direction of the inside of the nozzle  7 . 
         [0054]    The connecting means of the walls of the nozzle further comprise means for securing the plates  29 ,  31  to each other. By way of non-limiting example, these securing means comprise screws  33 , such as represented in further detail on  FIG. 5 . 
         [0055]    Referring to  FIG. 6 , illustrating a sectional view according to line  6 - 6  defined on  FIG. 4 , the nozzle  7  according to the present disclosure comprises a plurality of openings  35  contained in a plane substantially transverse to a longitudinal axis  34  (visible on  FIG. 10  of the nozzle. These openings  35  are interposed with the plates  29 ,  31  distributed discretely on the circumference of the nozzle. 
         [0056]    Referring to  FIG. 4 , the trailing edge  38  of the nozzle is open, that is to say that the ends of the inner  15  and outer  17  walls are not connected to each other, thus allowing providing good ventilation between the walls. 
         [0057]    In order to reinforce the structural hold of the nozzle, the inner  15  and outer  17  walls each comprise an annular stiffener  37 ,  39  disposed facing each other. 
         [0058]    The nozzle according to the present disclosure is advantageously produced by a method of forging-die-stamping the inner and outer skins from a material such as an austenite nickel-chromium based superalloy, for example Inconel. This method allows advantageously does not require longitudinal and circular welding on the nozzle. 
         [0059]    According to a second form of the nozzle according to the present disclosure, represented on  FIGS. 7 to 10 , the inner  15  and outer  17  walls are respectively constituted by a metallic skin made of an austenite nickel-chromium based superalloy (e.g., Inconel) and by a skin of titanium. The presence of an outer wall constituted by a skin of titanium allows reducing the mass of the nozzle with respect to the first form according to which the two walls of the nozzle are constituted by skins of Inconel. 
         [0060]    As before, the upstream section  11  of the nozzle is connected to a set of flanges  12 ,  13  respectively secured to the downstream rotor of the turbine of the turboprop engine (not represented) and rotary cowls assembled around the blades of the downstream fan. 
         [0061]    According to the present disclosure, the downstream section  25  of the nozzle  7  comprises a junction area  41  of the inner and outer walls. 
         [0062]    This junction area of the inner  15  and outer  17  walls comprises a plurality of pads  43  secured to the inner wall  15  and a plurality of pads  45  secured to the outer wall  17 . 
         [0063]    In longitudinal section, each pad  43 ,  45  has a substantially T shape. Each pad  43  is positioned facing each pad  45 . 
         [0064]    When the turboprop engine is at a standstill, the pads  45  of the outer wall  17  are facing the pads  43  of the inner wall  15 , but are not in contact with each other, as visible on  FIG. 9 . 
         [0065]    When the turboprop engine is in operation, the outer wall of the nozzle, constituted by a titanium skin, dilates more than the inner wall of the nozzle, constituted by a metallic skin of the austenite nickel-chromium based superalloy (e.g., Inconel), due to the difference between the coefficients of thermal expansion of titanium and Inconel. The outer wall is displaced towards the inner wall, thus leading to a displacement of the pads of the outer wall in the direction of the pads of the inner wall positioned facing each other, as a result creating a plurality of discrete connections (not represented) of “bearing plane” type between the pads of the outer wall and those of the inner wall. 
         [0066]    In one form, an abutment  47 , for example of carbon, is disposed between the pads  43  and  45 , so as to allow the absorption of shocks between the pads, and as a result limit the wear of the pads. The abutment  47  is for example secured on the pad  43  of the inner wall  15  by means of a set of screws  49 . 
         [0067]    By providing a set of pads positioned so as to create a plurality of bearing plane connections between the inner wall and the outer wall of the nozzle, instead of plates bolted together as was the case in the first form, one is rid of the flow issues which may occur due to the difference between the coefficients of differential expansion between Inconel and titanium. 
         [0068]    Furthermore, contrary to the previous form, no securing means between the inner and outer walls is provided. 
         [0069]    In order to reinforce the structural hold of the nozzle, the inner  15  and outer  17  walls each comprise two annular stiffeners  51   a,    51   b,    52   a,    52   b  disposed facing each other. 
         [0070]    According to the present disclosure, and by referring more particularly to  FIGS. 8 and 10 , the pads  43 ,  45  are distributed in a discrete manner on the circumference of the nozzle, thus allowing providing a plurality of openings  53  in a plane transverse to the longitudinal axis  34  of the nozzle. 
         [0071]    By way of non limiting example, six openings  53  and six sets of pads  43 ,  45  are provided on the circumference of the nozzle. 
         [0072]    The trailing edge  54  of the nozzle  7  (visible on  FIG. 7 ) is, as previously, open, thus allowing providing good ventilation between the walls. 
         [0073]    As previously, the inner wall of Inconel may be produced by a forging-die-stamping method. 
         [0074]    Thanks to the present disclosure, the presence of a circumferential annular junction area is hence no longer necessary. 
         [0075]    Thus, by ridding ourselves of such a circumferential annular junction area, need no longer remains for cold air flow circulation pipes provided in the prior art for refreshing the engine. 
         [0076]    The mass of the nozzle is thereby reduced considerably while providing good ventilation of the engine, thus allowing to substantially reduce the fuel consumption, in particular of the “Open Rotor” type turboprop engines. 
         [0077]    The present disclosure is not limited to the sole forms of this nozzle, described above by way of illustrating examples only, but on the other hand encompasses all the variants involving the technical equivalents of the means described as well as the combinations thereof if these fall within the scope of the present disclosure.