Abstract:
A hub of an intermediate casing for an aircraft turbojet engine, including an inner shell intended to define a primary flow space of a primary gas stream into a turbojet engine, and at least one intermediate space, the inner shell being provided with at least one primary port and at least one movable door forming a primary air passage conduit, the door being capable of collecting, from the primary port, air flowing in the primary gas space and of sending the air collected in this way, via the intermediate space, towards a secondary air passage conduit. The primary conduit has an inner surface including, from upstream to downstream, a converging upstream part, then a nonconverging downstream part, in which the downstream part includes two portions of downstream side surface, and in which the upstream portion further includes two portions of upstream side surface.

Description:
GENERAL FIELD 
       [0001]    The present invention relates to a hub of an intermediate casing for aircraft turbojet engine, in particular of the type comprising at least two mechanically independent bodies. 
         [0002]    In a double-body turbojet engine intermediate casing usually designates a casing the hub of which is arranged between a casing of a low-pressure compressor and a casing of a high-pressure compressor. 
         [0003]    The present invention relates more particularly to a hub of an intermediate casing of the type comprising bleed valves, sometimes designated by their acronym VBV (Variable Bleed Valves). 
         [0004]    Valves of this type are intended to regulate the inlet flow rate of the high-pressure compressor especially to limit pumping risks of the low-pressure compressor and enable evacuation of some of the air from the annular flow space of the primary flow. 
         [0005]    Also, in case of accidental penetration of water into this flow space especially in the form of rain or hail, or even various debris likely to harm operation of the turbojet engine, these valves retrieve this water or this debris which are centrifuged in the above flow space and ejected to the outside of the latter. 
         [0006]    In the case of bypass turbojet engines, these valves are configured to allow passage of fragments or debris from the flow space of the primary flow to a secondary annular flow space of a secondary flow. 
       PRIOR ART 
       [0007]    As illustrated in  FIGS. 1 and 2 , which are partial viewed in axial section of a bypass and double-body aircraft turbojet engine of known type, the hubs of the intermediate casings of the above type usually comprise two annular coaxial ferrules, respectively internal  4  and external  6 , mutually connected by an upstream transversal endshield  52  and by a downstream transversal endshield  54 . 
         [0008]    The upstream endshield  52  is arranged downstream of a low-pressure compressor  46  of the turbojet engine whereas the downstream endshield  54  is arranged upstream of a high-pressure compressor  48  of this turbojet engine. 
         [0009]    The high-pressure compressor  48  generally comprises a succession of variable-timing rotors and stators, for controlling the flow rate of air passing through it. 
         [0010]    Arranged between the internal  4  and external  6  ferrules, and between the upstream  52  and downstream  54  transversal endshields, are intermediate spaces  5  distributed around the axis M of the hub. 
         [0011]    The internal ferrule  4  delimits a primary annular flow space  40  of a primary flow of the turbojet engine, and is in general attached to structural arms  42  passing through this space. Also, the internal ferrule  4  comprises air passage orifices  44 , called primary orifices hereinbelow, each of which is blocked by the pivoting valve  102  of a corresponding bleed valve intended for regulation of the flow rate of the high-pressure compressor  48  and, if needed, evacuation of air or debris as explained hereinabove. 
         [0012]    Such a bleed valve can take the form of a door  100  which comprises the valve  102  at its radially internal end and which is pivotably mounted around an axis Y such that when the primary orifices  44  are in a closing position, the valve prolongs the internal ferrule  4  of the casing  2  substantially continuously to best reduce the risks of aerodynamic perturbations of the primary flow via this valve  102 , and that when said primary orifices are in an opening position the valve projects radially towards the inside relative to the above internal ferrule  4  and forms a scoop sampling of some of the primary flow in the space  40 . The door  100  comprises a conduit  101  via which scooped air transits, the conduit  101  terminating downstream on an outlet orifice  130  terminating in a corresponding intermediate space  5 . 
         [0013]    The external ferrule  6  delimits a secondary annular flow space  60  of a secondary flow of the turbojet engine, and is attached to structural arms  62  passing through this space. Also, the external ferrule  6  comprises air passage orifices  64 , called secondary orifices hereinbelow, and arranged downstream of the downstream transversal endshield  54 . 
         [0014]    When the variable-timing stators of the high-pressure compressor  48  are in a position reducing the airflow rate entering this compressor, an excess of air in the secondary flow space can be evacuated via these secondary orifices, avoiding pumping phenomena which can result in deterioration or even complete destruction of the low-pressure compressor  46 . 
         [0015]    Secondary conduits  200  extend each between a respective inlet orifice  220  terminating in the intermediate space  5  and a corresponding secondary orifice  64 . The inlet orifice  220  is generally arranged near the surface of the downstream transversal endshield opening onto the intermediate space  5 . 
         [0016]    The outlet orifice  130  of the primary conduit  101  and the inlet orifice  220  of the secondary conduit  200  are arranged opposite in each intermediate space  5 . 
         [0017]    Each door  100 , the intermediate space  5  and the corresponding downstream secondary conduit together form an air and debris evacuation system from the primary flow space  40  towards the secondary flow space  60 . The hub therefore comprises a plurality of such systems distributed around its axis. 
         [0018]    When a door  100  is in the open position, airflow scooped by the latter passes through the primary conduit and terminates in the intermediate space  5  by its outlet orifice  130 , penetrates the corresponding secondary conduit  200  until it reaches the secondary flow space  60 . 
         [0019]    Each door  100  has an internal surface  101  including two planar lateral portions and mutually convergent in an azimuthal plane parallel to the plane of  FIG. 3 , from the primary orifice  44  towards the outlet orifice  130 . This azimuthal convergence is done for two reasons: both to boost the airflow rate scooped from the primary annular space and also due to equipment housed in between the intermediate spaces distributed around the axis M of the hub, limiting the dimensions of the outlet orifices in the corresponding azimuthal plane. 
         [0020]    However, an airflow scooped by means of such evacuation systems undergoes loss of load when this flow passes through the intermediate space. The consequence of these load losses is reducing the air sampling flow rate from the primary flow space  40  towards the secondary flow space  60 . 
         [0021]    Now, this flow rate must respect a certain specification for sampling air necessary for operability of the motor during all its flight phases. Also a substantial flow rate gap between the inlet of the low-pressure compressor  46  and the inlet of the high-pressure compressor  48  can lead to deterioration of the low-pressure compressor  46 , above during deceleration phases. 
         [0022]    A solution for avoiding these load losses could in theory be to directly attach the primary  101  and secondary  200  conduits. Such attachment however is very difficult to do due to the moveable character of the door  100 , and would consume too much space in this intermediate space in which other equipment is housed. 
         [0023]    Another solution consisting of deflectors extending in the intermediate space  5  has already been proposed in patent application FR 2 936 561. These deflectors present an open internal surface in the form of a tongue and extending from a radially internal edge of the inlet orifice of each secondary conduit relative to the axis of the hub, and are provided to guide air and debris in the intermediate space  5  coming from the primary conduit towards the secondary conduit. 
         [0024]    However, these deflectors presenting an open surface prove insufficient for resolving the above loss of load problems, especially in the azimuthal plane. 
       SUMMARY OF THE INVENTION 
       [0025]    An aim of the invention is especially to contribute a simple, economical and efficacious solution to these losses of load problems. 
         [0026]    For this reason a hub of an intermediate casing for an aircraft turbojet engine is proposed, comprising an internal ferrule intended to delimit both a primary flow space of a primary gas flow in a turbojet engine, and also at least one intermediate space, the internal ferrule being provided with at least one primary orifice and at least one moveable door forming a primary conduit for passage of air, said door being capable of sampling, from the primary orifice, air circulating in the primary gas space and sending back to the intermediate space the sampled air in the direction of a secondary conduit for passage of air, said hub being characterized in that the primary conduit has an internal surface comprising from upstream to downstream a convergent upstream part, then a non-convergent downstream part, in which the downstream part comprises two portions of downstream lateral surfaces, and in which the upstream part further comprises two portions of upstream lateral surfaces, each portion of upstream lateral surface defining with a respective downstream lateral surface a lateral part of the internal surface, each portion of downstream lateral surface having a length according to an upstream-downstream direction representing between 30% and 50% of the curvilinear length from upstream to downstream of the corresponding lateral part. 
         [0027]    It is clear that the upstream and downstream directions are defined in relation to the flow of the primary gas flow when the hub of the intermediate casing according to the invention is used in a turbojet engine. 
         [0028]    Such a primary conduit having a non-convergent downstream part counteracts the effect of convergence naturally caused by the upstream part, and ensures that an airflow terminating in the intermediate space via the outlet orifice reaches a majority of the inlet orifice of the opposite secondary conduit. 
         [0029]    Given that a greater portion of the internal volume of the secondary conduit is occupied by the airflow, such a primary conduit improves the flow rate sampling in the secondary conduit, and consequently the overall airflow rate sampled from the primary flow space. 
         [0030]    Also, the fact that the portions of downstream lateral surfaces cover more than 30% of the portions of lateral surfaces ensures that the airflow will have time, between the instant when this flow passes from the upstream part to the downstream part, and the instant when the flow reaches the outlet orifice, to be recovered so as to no longer converge. 
         [0031]    The fact that the portions of downstream lateral surfaces cover less than 50% of the portions of lateral surfaces also avoids imposing an excessive angle for transition between upstream lateral part and downstream lateral part, the width of the inlet orifice in effect being restricted by adjacent equipment. Such an excessive angle in effect would cause unwanted flow detachment. 
         [0032]    The range of 30% to 50% therefore offers a good compromise between limitation of detachment phenomena and convergence attenuation of the flow in the downstream part. 
         [0033]    The invention can be completed by the following characteristics, taken singly or in any of their technically possible combinations. 
         [0034]    Since the door is movably mounted on the internal ferrule between a closing position and a maximum opening position of the primary orifice, the downstream part can be contoured to direct airflow towards the entirety of the inlet orifice of the opposite secondary conduit when the door is in its maximum opening position. Therefore, the flow rate sampling in the secondary conduit is maximized during critical phases in which the door is wide open and in which the risks of deterioration of the compressor caused by pumping are the highest. 
         [0035]    The non-convergent downstream part can tangentially prolong the corresponding upstream part to minimize perturbations undergone by airflow at the junction between the upstream and downstream parts of the primary conduit. 
         [0036]    The downstream part can be defined by two portions of downstream lateral surfaces and two radially internal and external surface portions relative to the axis M of the hub, said radially internal and external portions being mutually non-convergent. 
         [0037]    Each portion of downstream lateral surface can be planar and form a flaring angle from upstream to downstream of less than 5° with an average flow axis of the corresponding door. This limits the divergence of an airflow terminating in the intermediate space by the outlet orifice in an azimuthal plane of the primary conduit. 
         [0038]    The upstream part can comprise two portions of upstream lateral surfaces each defining with a respective downstream lateral surface a lateral part of the internal surface, and each portion of downstream lateral surface can have a length according to an upstream-downstream direction representing 40% of the curvilinear length from upstream to downstream of the corresponding lateral part. 
         [0039]    This minimum length effectively corrects the convergent character of an airflow having passed through the upstream part, before this flow terminates in the intermediate space via the outlet orifice of the primary conduit of the door. 
         [0040]    Each side wall can also have an S-shaped profile. This arrangement minimizes or even prevents bursting of the jet in the intermediate space on exiting the door and favours its capture by the secondary conduit, and limits circulation in the intermediate space. 
         [0041]    The downstream part can be cylindrical. This alignment ensures that an airflow terminating in the intermediate space has divergence close to zero. 
         [0042]    The secondary conduit can be extended from its inlet orifice by a deflector extending upstream in the corresponding intermediate space, each deflector forming an air guide conduit having an internal surface extending from said inlet orifice as far as a guide orifice arranged downstream of the outlet orifice of the corresponding door, and in which the downstream part is contoured to confine an airflow towards the inside of the circumference of the guide orifice when the door is in its maximum opening position. Such a deflector prevents recirculation phenomena in the intermediate space. 
         [0043]    An intermediate casing for an aircraft turbojet engine is also proposed, characterized in that it comprises a hub such as described previously. 
         [0044]    An aircraft turbojet engine is also proposed, characterized in that it comprises the preceding intermediate casing. 
     
    
     
       DESCRIPTION OF FIGURES 
         [0045]    Other characteristics, aims and advantages of the invention will emerge from the following description which is purely illustrative and non-limiting and which must be considered with respect to the appended drawings, in which: 
           [0046]      FIG. 1 , already discussed, is a view in axial section of a hub for an intermediate casing  2  known from the prior art. 
           [0047]      FIG. 2 , already discussed, is a view in perspective and in axial section of the hub of  FIG. 1 . 
           [0048]      FIG. 3 , already discussed, is a sectional view of an evacuation system of debris known from the prior art in a plane perpendicular to the plane of  FIG. 1 , so-called azimuthal plane. 
           [0049]      FIG. 4 , is a schematic view in perspective of the internal surface of a door  100  according to an embodiment. 
           [0050]      FIG. 5  is a schematic side view of the door  100  already illustrated in  FIG. 4 . 
           [0051]      FIG. 6  is a partial schematic view in axial section of an evacuation system comprising the door  100  illustrated in  FIGS. 4 and 5 . 
           [0052]      FIG. 7  is a schematic partial plan view in an azimuthal plane of the system illustrated in  FIG. 6 . 
           [0053]      FIGS. 8 a  and 8 b    are schematic views in side perspective of a deflector according to a first embodiment. 
           [0054]      FIG. 9  is a side view of the deflector illustrated in  FIG. 8   a.    
           [0055]      FIG. 10 , is a plan view parallel to an azimuthal plane of the deflector illustrated in  FIG. 8   a.    
           [0056]      FIG. 11  is a schematic view in side perspective of a deflector according to a second embodiment. 
           [0057]      FIG. 12  is a schematic frontal view of the deflector illustrated in  FIG. 11 . In all figures similar elements have identical reference numerals. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0058]    The hub parts for intermediate casing of the prior art already described are also present in the following embodiments, with the exception of deflectors forming tabs. 
         [0059]    First Aspect: Geometry of Scooping Doors 
         [0060]    The structure of the doors  100  will be described with respect to  FIGS. 4 to 7 . 
         [0061]    In reference to  FIG. 4 , each door  100  has a closed internal surface  102 . Each internal surface  102  includes from the upstream to downstream, an upstream part  110  then a downstream part  120  terminating on the corresponding outlet orifice  130 . 
         [0062]    Each door  100  has an average gas flow axis X 1  at its outlet orifice  130 . 
         [0063]    The upstream part  110  is convergent from upstream to downstream, from the inlet orifice of the door  100  to an intermediate section of the conduit. The term “convergent” here means that the field of vectors associated with a gas flow flowing from upstream to downstream in the upstream part  110  of the primary conduit  101  has negative divergence. 
         [0064]    The downstream part  120  is non-convergent from upstream to downstream. In other words, the field of vectors associated with a gas flow flowing from upstream to downstream in the downstream part  120  has zero or positive divergence. 
         [0065]    The upstream part  110  comprises a portion of radially external surface  112  relative to the axis M of the hub, a portion of radially internal surface  114  relative to the axis M of the hub, and two portions of lateral surfaces  116   a  and  116   b.    
         [0066]    The downstream part  120  similarly comprises a portion of radially external surface  122  relative to the axis M of the hub, a portion of radially internal surface  124  relative to the axis M of the hub, and two portions of lateral surfaces  126   a  and  126   b.    
         [0067]    The outlet orifice  130  of the door conduit  100  also has a circumference comprising a radially external edge  132 , a radially internal edge  134  and two lateral edges  136   a  and  136   b,  in which respectively terminate the portion of radially external surface  122 , the portion of radially internal surface  124  and the portions of downstream lateral surfaces  126   a,    126   b.    
         [0068]    Also, the radially external  122  and internal  14  surface portions tangentially extend the external  112  and internal  114  surface portions respectively. 
         [0069]    The portions of downstream surface  122 ,  124  can be portions of cylinder of generatrices parallel to the average gas flow axis X 1  in the downstream part  120  of the door  100 . This parallelism limits the burst phenomena of flow in the intermediate space in a meridian plane, and improves the guiding of air towards the opposite secondary orifice in the intermediate space  5 . 
         [0070]    The portions of downstream external surfaces  124 ,  122  can have concavity turned radially towards the external relative to the axis M of the hub so as to embrace the contour of the internal annular ferrule  4 . For example, the portions  122 ,  124  can be portions of a cylinder whereof the generatrices are parallel to the flow axis X 1 . 
         [0071]    As a variant not illustrated, the downstream portions  122 ,  124  of the door  100  can be planar, and the edges  132  and  134  be rectilinear. 
         [0072]    In an azimuthal plane parallel to the plane of  FIG. 5 , the width of the outlet orifice  130  is less than the width of the primary orifice  44 ; the conduit has a convergent azimuthal profile from upstream to downstream. 
         [0073]    Each upstream lateral part  116   a,    116   b  is connected to a respective downstream lateral part  126   a,    126   b.  The two upstream lateral parts  116   a,    116   b  are mutually convergent, that is, they approach each other progressively when the conduit is travelled from upstream to downstream. Each upstream lateral part  116   a,    116   b  can be planar, curved, or a combination of both. The upstream lateral parts  116   a,    116   b  converge a primary gas flow from upstream to downstream in the azimuthal plane. 
         [0074]    Each downstream lateral part  126   a,    126   b  tangentially extends a corresponding upstream lateral part  116   a,    116   b  and terminates in a lateral edge of the orifice  136   a,    136   b.  For example, each lateral part in its entirety is a portion of cylinder of generatrices perpendicular to the average flow axis X 1  in the conduit of the door  100 . In this portion of cylinder, the lateral part downstream is planar. 
         [0075]    The two downstream lateral parts are substantially parallel, that is, an angle of less than 5° is formed between each plane of a downstream lateral part and the average flow axis X 1 . 
         [0076]    The downstream lateral parts correct the convergence effect in the azimuthal plane previously caused by the upstream lateral parts, and limit the divergence of the flow sent to the intermediate space  5 . In other words, the field of vectors represented by airflow at the outlet orifice  130  will have limited divergence between a negative value dependent on the upstream lateral parts, and zero. 
         [0077]    An average flow axis X 2  is defined in a plane P 2  defined by the inlet orifice  220  of the secondary conduit  200  (illustrated especially in  FIG. 6 ). 
         [0078]    All the tangents of the downstream part  120  at the circumference of the outlet orifice  130  delimit a closed surface. This closed surface intersects the plane P 2  of the inlet orifice  220  of the opposite secondary conduit  200  in a closed line which encompasses or coincides with the circumference of said inlet orifice  220 . 
         [0079]    This particular alignment of the tangents of the downstream part  120  enables spreading of the gas flow over the entire extent of the inlet orifice of the secondary conduit, and improves the feed of the secondary conduit in the meridian and azimuthal plane. 
         [0080]    In the embodiment illustrated in  FIG. 6 , the door  100  is illustrated in its maximum open position. The closed surface formed by all the tangents at the outlet orifice  130  intersects the plane of the orifice in the circumference of the secondary orifice  220 . So the recirculation phenomena in the intermediate space  5  are avoided when the door is in the full open position. 
         [0081]    Each portion of downstream lateral surface  126   a,    126   b  has a length referenced L 2 , according to the upstream-downstream direction defined by the axis X 1 . Each upstream lateral portion  116   a,    116   b  has a curvilinear length from upstream to downstream referenced L 1 . Each lateral part of the conduit defined by a portion of upstream lateral surface and a portion of downstream lateral surface therefore has a total curvilinear length from upstream to downstream equal to the sum of the lengths L 1  and L 2 . Each portion of downstream lateral surface  126   a,    126   b  preferably has a length L 1  of between 30% and 50%, preferably 40% of the total curvilinear length L 1 +L 2  of a corresponding lateral part. This minimum length of 30% corrects the convergence of a flow imposed by the upstream part  110 , and has it tend towards zero the divergence of the gas flow at the outlet orifice  130 . 
         [0082]    In reference to  FIG. 7 , each portion of lateral surface can present an S-shaped profile from the inlet orifice to the outlet orifice. In other words, the profile of each portion of lateral surface has a single point of inflection. 
         [0083]    This arrangement does not perturb the flow of the flow in the space  40  and minimize or even prevent bursting of this flow in the intermediate space  5  at output of the door, and favours its capture by the secondary conduit  20  and limits recirculation in the intermediate space  5 . 
         [0084]    Second Aspect: Deflectors of Secondary Conduit 
         [0085]    Deflectors according to a second aspect will now be described, with respect to  FIGS. 8 a    to  12 . 
         [0086]    Each secondary conduit  200  has a closed internal surface  202 . 
         [0087]    A deflector  300  forming an air guide conduit  310  extends from the inlet orifice  220  of the secondary conduit  200  to upstream of the downstream transversal endshield  54 , in the intermediate space  5 . The air guide conduit  301  is also a closed surface extending from downstream to upstream from the circumference of the inlet orifice  220  as far as a guide orifice  330 . 
         [0088]    The air guide conduit  301  forms an upstream extension of the secondary conduit  200 , which can for example be fixed by fastening means (not illustrated) against the surface of the downstream transversal endshield opening into the intermediate space  5 . In this way, the deflector can be mounted or dismounted in the intermediate space during upkeep to the turbojet engine without the downstream transversal endshield  54  or the secondary conduit  200  having to be dismounted. 
         [0089]    The guide conduit  301  has an internal surface called guide surface  302  constituted by at least two parts of surfaces each extending between the inlet orifice  220  and the guide orifice  330 : at least one part known as flared  310  and at least one part known as tangent  320 . 
         [0090]    The tangent part  320  extends a first part of the internal surface  202  of the secondary conduit  200  tangentially over its whole length between the inlet orifice  220  of the conduit and the guide orifice  330 . The tangent portion  320  is for example a portion of cylinder of generatrices parallel to the average flow axis X 2 . 
         [0091]    The tangent portion  320  is joined to the flared part  310  by two end generatrices  324   a  and  324   b,  these end generatrices being parallel to the axis X 2  and extending between the inlet orifice  220  and the guide orifice  330 . 
         [0092]    Also, any plane tangent at any point of the flared part  310  forms with the average flow axis X 2  an angle less than 90°. 
         [0093]    In reference to  FIG. 9 , all the tangents of the internal guide surface  302  in the circumference of the guide orifice  330  of the deflector  300  delimit a closed surface. This closed surface intersects the plane P 1  of the outlet orifice of the opposite door  100  in a closed line which encompasses or coincides with the circumference of the outlet orifice  130  of the door  100 . 
         [0094]    This particular alignment of tangents of the downstream part improves the collecting function of the deflector  300 . In effect, a gas flow entering the intermediate space  5  via the outlet orifice  130  of the door  100  undergoes natural three-dimensional bursting likely to create the refluxes described in the preamble, which this alignment confines. 
         [0095]    In the embodiments illustrated in  FIGS. 8 a    to  12 , the secondary conduit  200  has a secondary internal surface comprising a portion of radially internal surface  214  relative to the axis M of the hub, a portion of radially external surface relative to the axis M of the hub  212 , and two portions of lateral surfaces  216   a,    216   b.    
         [0096]    The inlet orifice  220  further has a circumference comprising a radially internal edge  224 , a radially external edge  222  and two lateral edges  226   a  and  226   b  respectively connected to the radially internal portion  214 , the radially external portion  212  and the lateral portions  216   a,    216   b  of the internal surface  202 . 
         [0097]    Also, the internal guide surface comprises a radially internal portion  312 , a radially external portion  322 , and two lateral portions  314   a,    314   b  respectively connected to the radially internal edge  224 , the radially external edge  222  and the two lateral edges  226   a  and  226   b  of the inlet orifice  220 . 
         [0098]    Similarly, the guide orifice  330  has a circumference comprising a radially internal edge, a radially external edge and two lateral edges, in which terminate respectively the radially internal, external and lateral portions of the internal guide surface. 
         [0099]    The flared part  310  comprises the radially internal portion  312  and the lateral portions  314   a,    314   b  of the guide surface, whereas the tangent portion  320  is the radially external portion  320 . 
         [0100]    The radially internal portion is planar and forms a meridian flaring angle a constant relative to the radially internal portion  224  of the secondary conduit  200  which it prolongs. This meridian flaring angle a is strictly greater than 0° and preferably less than 90°, for example 45°. 
         [0101]    Each lateral portion  314   a,    314   b  of the guide conduit  301 , extending from a respective lateral edge of the orifice, has an azimuthal flaring angle B at most equal to 45°, preferably between 20 and 35°, relative to the lateral portion  216   a,    216   b  of the respective secondary conduit  200  which it prolongs. 
         [0102]    Each lateral portion  314   a,    314   b  is a regulated surface delimited at least by an end generatrix of the tangent part  320 , and a respective lateral edge  226   a,    226   b  of the inlet orifice  220 . 
         [0103]    The internal surface  302  is a regulated surface of generatrices extending between the inlet orifice  220  of the secondary conduit  200  and the guide orifice  330 . 
         [0104]    The lateral portion of the guide conduit  301 , extending from a respective lateral edge of the orifice, presents an azimuthal flaring angle at most equal to 45° relative to the lateral portion of the secondary conduit  200  which it prolongs. 
         [0105]    The average length of the radially internal portion  312  between the orifices  220  and  330  can be identical or different to the average length of the radially external portion  322 . 
         [0106]    For example, the average length of the radially internal portion  312  between the orifices  220  and  330  can be greater than the average length of the radially external portion  222 . This improves the collecting function of the deflector in the radially internal part of the intermediate space, and limits its bulk in an upstream part of the intermediate space, which is generally intended to be occupied by other equipment of the turbojet engine. 
         [0107]    In the embodiment of a deflector illustrated in  FIGS. 8 a    and  8   b,  the inlet orifice  200  has a rectangular circumference. The guide orifice  330  has a trapezoid form. 
         [0108]    The radially external portion  322  is planar, coplanar with the portion of the secondary conduit  200  which it prolongs. 
         [0109]    The tangent and flared parts are joined by end generatrices  324   a,    324   b  forming ridges in the internal guide surface. 
         [0110]    In the deflector embodiment illustrated in  FIGS. 11 and 12 , the inlet orifice  220  of the conduit has a rectangular circumference with rounded corners. The guide orifice  330  is trapezoid in form. 
         [0111]    The tangent portion  320  is a portion of cylinder comprising a planar central sub-portion and two curved sub-portions connected on either side of the central sub-portion and terminating by the end generatrices  324   a,    324   b.    
         [0112]    The flared part  310  comprises the radially internal portion  312 , the two lateral portions  314   a,    314   b,  and two intermediate portions  316   a,    316   b.  Each intermediate portion  316   a,    316   b  forms a junction between the radially internal portion  312  and a respective lateral portion  314   a,    314   b.    
         [0113]    Each intermediate sub-portion  316   a,    316   b  is connected to a respective lateral portion in an intermediate generatrix  318   a,    318   b.  In this embodiment the flaring azimuthal angle is maximum in each intermediate generatrix. 
         [0114]    Of course, the deflector is not limited to the embodiments illustrated in  FIGS. 8 a    to  12 . 
         [0115]    Each deflector can be generalized to a conduit comprising an internal guide surface creating transition between the respective circumferences of the orifices  220  and  330 , these two circumferences being any closed lines, for example ovoid or polygonal. 
         [0116]    The portions of the internal guide surface can have concavity turned towards the inside or towards the outside of the guide conduit  301 . The radially internal  312  and external  322  portions can present concavity turned towards the axis M of the hub, or moving away from this axis. 
         [0117]    The internal guide surface  302  of the deflector  300  can have more than one flared part. As a variant, the flared part can be extended to the whole internal guide surface. 
         [0118]    Combination of First and Second Aspects 
         [0119]    The door  100  according to the first aspect and the deflector  300  according to the second aspect can be combined in a same hub for intermediate casing. 
         [0120]    In reference to  FIG. 9 , all the tangents of the downstream part  120  of each door  100  in the circumference of the outlet orifice  130  can delimit a closed surface which intersects both the plane P 2  of the inlet orifice  220  of the opposite secondary conduit  200  in a closed line which encompasses or coincides with the circumference of said the inlet orifice  330 , as described previously, and also intersects a plane P 3  defined by the guide orifice  330  in a closed line which is included in the circumference of said guide orifice  330 . 
         [0121]    Such alignment lets the deflector collect the entirety of a gas flow emanating from the door  100  and having passed through the intermediate space  5 , and this flow passes through the inlet orifice  220  according to its whole area. Such alignment therefore prevents recirculation of flow in the intermediate space at the same time, and ensures a maximum sampling flow rate in the secondary conduit.