Patent Publication Number: US-2007107509-A1

Title: System for transmitting pressures between a detachable part and a fixed part of a scale model placed in aerodynamic tunnel

Description:
FIELD OF THE INVENTION  
      This invention belongs to the technical field of systems intended for tapping and transmitting pressures between pieces of test models in a wind tunnel, for the tapping, measurement and analysis of those pressures and aerodynamic properties of elements of aircraft, cars, trains, etc. In particular, the invention applies to the sector of systems for the tapping and transmission of pressures between a fixed part and a detachable part, mobile or otherwise, of test models in a wind tunnel in the aeronautical sector.  
     PRIOR ART OF THE INVENTION  
      In wind tunnel tests conducted in the aeronautical sector, it is very often necessary to tap pressures in the different pieces making up the models used.  
      To do this, in the prior art many of these pieces are designed to have pressure taps, which consist of small holes connected by means of pipes to a module where the different pressures that are gathered are measured. No kind of flow passes through these pipes; all that is present is the pressure to measure.  
      In the prior art, when there existed a detachable part with pressure taps forming part of a model, the way of connecting and/or disconnecting the pressures was by means of the use of connectors, such as for example pipes made of various materials, such as metal, plastic, etc.  
      These connection system present major drawbacks. One of them is the time needed for fitting and removing any piece of a model provided with pressure taps. Given that wind tunnels tests are very expensive to conduct, any saving in time during the assembly and dismantling of the different arrangements of the model necessary for the tests implies a reduction in costs and therefore a saving in money.  
      Moreover, models for testing in wind tunnels are usually small size, which very often makes it complicated or impossible to install the desired number of pressure taps, and the pipes needed for its transmission.  
      The system forming the object of the patent application arises out of the need to install a large number of small pressure taps, without the need to use complex connectors or pipes, and to reduce the time needed for the fitting and removing of the different pieces and the assembly and dismantling of the arrangements of the model for different wind tunnel tests.  
     DESCRIPTION OF THE INVENTION  
      The present invention has the aim of overcoming the drawbacks of the pressure connection systems of the prior art described above by means of a system for transmitting pressure without using pipes, between a detachable part and a fixed part of a model used in wind tunnel tests.  
      In the present invention, the detachable part of the model comprises a set of pressure tapping holes and a set of pressure outlets complementary to those pressure tapping holes, along with an array of internal conduits which link the pressure tapping holes with their respective pressure outlets.  
      The fixed part of the model in turn comprises an array of pressure inlets made in a distributor block provided in said fixed part, which are extended in pressure transmission ducts that can be connected to a pressure measuring module via an array of pressure transmission conduits.  
      The invention furthermore comprises means of coupling for coupling of the detachable part to the fixed part.  
      The pressure outlets of the detachable part terminate in a first contact surface provided in said detachable part, which faces a second contact surface provided in the distributor block of the fixed part, where the pressure inlets made in that distributor in turn terminate.  
      The coupling between the fixed part and the detachable part of the model is made via said first and second contact surfaces such that the pressure outlets of the detachable part face the pressure inlets of the distributor block of the fixed part.  
      A sealing joint is provided between the first contact surface and the second contact surface. This sealing joint comprises a first face confronting the first contact surface and a second face confronting the second contact surface.  
      So that the pressure connection can exist between the pressure outlets of the detachable part and the pressure inlets of the fixed part, the sealing joint includes a set of passage holes aligned with those pressure outlets and inlets, via which the pressure tapped in the detachable part is transmitted to the fixed part. Thanks to the sealing joint, pressure losses between the surfaces of the fixed part and the detachable part are prevented, and measurement errors that these pressure losses would originate are thus avoided.  
      In this way, with the present invention the system of connection by pipes is done away with, thus reducing the time needed for fitting and removing the parts of the model provided with the pressure taps and outlets. Another additional advantage of the invention is the possibility of being able to install a large number of pressure taps in a small space, something which was not possible with the traditional systems used in the state of the art, since these systems require large spaces for the taps and the connection pipe, which is not compatible with the small dimensions of test models in wind tunnels.  
      In one of the embodiments of the invention, in order to facilitate the join and contact between the contact surfaces of the fixed and detachable parts of the model, the first contact surface of the detachable part is located in a first depression made in that detachable part, and the second contact surface of the fixed part is located in a second ridge emerging from the outer wall of the distributor block of said fixed part. In this embodiment, the sealing joint fits into the first depression of the detachable part via its periphery.  
      In an alternative embodiment of the invention, in order to facilitate contact between both contact surfaces, the first contact surface of the detachable part is located in a first ridge in that detachable part, and the second contact surface of the fixed part is located in a second depression made in the outer wall of the distributor block of said fixed part. In this embodiment, the sealing joint fits into the second depression of the distributor block of the fixed part via its periphery.  
      In an embodiment of the sealing joint, said sealing joint includes at least one centred opening through which passes at least one second centred projection which emerges from the second contact surface of the fixed part. In a preferred form of carrying out this embodiment, the second centred projection traverses the centred opening of the sealing joint and penetrates into a first recess provided in the first contact surface of the detachable part.  
      In an alternative embodiment of the sealing joint, said sealing joint includes at least one centred opening through which passes at least one first centred projection which emerges from the first contact surface of the detachable part. In a preferred form of carrying out this embodiment, the first centred projection traverses the centred opening of the sealing joint and penetrates into a second recess provided in the second contact surface of the fixed part.  
      The advantage of these embodiments of the sealing joint is the greater securing of that sealing joint between the contact surfaces of the detachable part and the fixed part, and a complete immobilisation of the latter, thereby preventing possible displacements which would give rise to the pressure tapping holes or the pressure outlets becoming covered.  
      In another additional embodiment of the sealing joint, it is the sealing joint itself which presents at least a third centred projection, located either in the first face confronting the first contact surface of the detachable part or the second face confronting the second contact surface of the fixed part, and even, in both faces, said third projection penetrating either into a first recess in the first contact surface of the detachable part or into a second recess in the second contact surface of the fixed part, or into both the first recesses and second recesses of the two pieces.  
      The advantage of these additional embodiments of the sealing joint is the greater ease of manufacture of the fixed and removable parts of the model, having to make recesses in them instead of projections as in previous embodiments, with the projections being made more simply in the sealing joint, said element having less importance in the tests than the actual fixed and moving pieces of the models.  
      The pressure connection system without pipes of the present invention permits pressure tappings and connections to be made in very small size pieces, in such a way that the parts that are connected can have a surface area of the order of several square millimetres. The holes can therefore be of the order of several tenths of a millimetre. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  is a diagrammatic view in upper plan of a fixed part and a detachable part belonging to a model to which the system of the present invention is being applied;  
       FIG. 2  is an enlarged diagrammatic view corresponding to zone A marked in  FIG. 1 ;  
       FIG. 3  is a diagrammatic view in transverse cross-section along the line B-B′ shown in  FIG. 1 ;  
       FIG. 4  is an enlarged diagrammatic view of the interior corresponding to zone C marked in  FIG. 3 ;  
       FIG. 5  is a diagrammatic view in transverse cross-section along the line D-D′ shown in  FIG. 3 ;  
       FIG. 6  is a diagrammatic view in front elevation of a first embodiment of the sealing ring shown in  FIG. 3 ;  
       FIG. 7  is a diagrammatic view in transverse cross-section along the line E-E′ shown in  FIG. 3 ;  
       FIG. 8  is a diagrammatic view in front elevation of a second embodiment of the sealing ring;  
       FIG. 9  is a diagrammatic view in front elevation of a first embodiment of the contact surface of the detachable part;  
       FIG. 10  is a diagrammatic view in front elevation of a first embodiment of the contact surface of the distributor block;  
       FIG. 11  is a diagrammatic view in transverse cross-section along the line F-F′ shown in  FIG. 9 ;  
       FIG. 12  is a diagrammatic view in transverse cross-section along the line G-G′ shown in  FIG. 10 ;  
       FIG. 13  is a diagrammatic view in front elevation of a second embodiment of the contact surface of the detachable part;  
       FIG. 14  is a diagrammatic view in front elevation of a second embodiment of the contact surface of the distributor block;  
       FIG. 15  is a diagrammatic view in transverse cross-section along the line H-H′ shown in  FIG. 13 ;  
       FIG. 16  is a diagrammatic view in transverse cross-section along the line I-I′ shown in  FIG. 14 ;  
       FIG. 17  is a transverse diagrammatic view of an embodiment of the sealing joint with four third centred projections. 
    
    
      Appearing in these figures are numerical references denoting the following elements: 
           1  fixed part      2   a , 2   b  detachable part      3   a - 3   h  pressure tapping holes      4   a - 4   h  internal conduits      5   a - 5   h  pressure outlets      5   i  first contact surface      5   j  first depression      5   k  first ridge      5   l  first centred projection      5   m  first recess      6  coupling means      7  distributor block      7   a - 7   h  pressure inlets      7   i  second contact surface      7   j  second depression      7   k  second ridge      7   l  second centred projection      7   m  second recess      8   a - 8   h  pressure transmission ducts      9   a - 9   h  pressure transmission conduits      10  sealing joint      10   a - 10   h  passage holes      10   i  centred opening      10   j  third centred projection      11  first face of the sealing joint      12  second face of the sealing joint        

     MODES OF EMBODIMENT OF THE INVENTION  
       FIG. 1  shows a diagrammatic view of a fixed part  1  and two detachable parts  2   a , 2   b  belonging to a model subjected to tests in a wind tunnel, to which the system for transmitting pressures of the present invention is being applied.  
      The detachable part  2   a , 2   b  of the system for transmitting pressures of the present invention comprises an array of pressure tapping holes  3   a - 3   h .  FIGS. 2 and 3  show those pressure tapping holes  3 a- 3 h in detail in the detachable part  2   a , 2   b.    
      As can be seen in  FIG. 3 , the detachable part  2   a , 2   b  also comprises an array of internal conduits  4   a - 4   h  via which the pressure tapping holes  3   a - 3   h  connect with respective pressure outlets  5   a - 5   h  also provided in said detachable part  2   a , 2   b.    
      Said system for transmitting pressure furthermore comprises an array of pressure inlets  7   a - 7   h  made in a distributor block  7  provided in the fixed part  1 . These pressure inlets are extended in pressure transmission ducts  8   a - 8   h , which can be connected to a pressure measuring module via the pressure transmission conduits  9   a - 9   h.    
      The system also includes coupling means  6 , such as screws for example, in order to couple the detachable part  2   a , 2   b  to the fixed part  1 , as can be seen in  FIG. 3 .  
      In the system for transmitting pressure forming the object of the present invention, when the detachable part  2   a , 2   b  is fitted to the fixed part  1 , the pressure outlets  5   a - 5   h  of the detachable part  2   a , 2   b  terminate in a first contact surface  5   i  provided in said detachable part  2   a , 2   b  and facing the fixed part  1 , and the pressure inlets  7   a - 7   h  made in the distributor block  7  provided in the fixed part terminate in a second contact surface  7   i  provided in said distributor  7 , facing the first contact surface  5   i  of the detachable part  2   a , 2   b.    
      As can be seen in  FIGS. 3 and 4 , the first contact surface  5   i  and the second contact surface  7   i  are facing in such a way that the pressure outlets  5   a - 5   h  of the detachable part  2   a , 2   b  are facing the pressure inlets  7   a - 7   h  of the fixed part  1 . In this way, the pressure tapped in the detachable part  2   a , 2   b  via the pressure tapping holes  3   a - 3   h  are transmitted to the fixed part  1 , and can be measured with a pressure measuring module connected to said fixed part  1 , via the pressure transmission conduits  9   a - 9   h.    
      In this way, transmission is achieved of the pressures tapped in the detachable part  2   a , 2   b  to the fixed part  1 , from where they are sent to the pressure measuring module connected to the latter, without any need for the pipes or additional connections that were necessary in pressure connection systems in wind tunnel models used in the state of the art.  
      So, with the fixed part  1  and the detachable part  2   a , 2   b  directly facing each other, and by causing some holes made in the pieces to directly connect the pressure from one side to the other, a series of advantages is obtained with respect to the systems used in the state of the art. The first of them is that the space necessary for passing the information from the pressure tappings is reduced since the pipes used so far for transmitting the pressures are not needed. Another advantage is the reduction in time for assembling and dismantling the model for wind tunnel tests, since the connection and disconnection of pressures is achieved at the same time as the detachable part  2   a , 2   b  is fitted to or removed from the fixed part by conventional means, such as screws or nuts for example.  
       FIGS. 3 and 4  show that between the first contact surface  5   i  and the second contact surface  7   i  is a sealing joint  10  which comprises a first face of the sealing joint  11  facing said first contact surface  5   i  and a second face of the sealing joint  12  facing said second contact surface  7   i . Said sealing joint contains an array of passage holes  10   a - 10   h  aligned with at least one of the pressure outlets  5   a - 5   h  of the detachable part  2   a , 2   b , and with at least one of the pressure inlets  7   a - 7   h , in such a way that pressure tapped in the pressure holes  3   a - 3   h  passes from the detachable part  2   a , 2   b  to the fixed part  1  via said passage holes  10   a - 10   h.    
      This sealing joint is made of a flexible material such as rubber or similar, thereby achieving a perfect join between the detachable part  2   a , 2   b  and the fixed part  1 .  FIG. 6  shows an embodiment of the sealing joint  10 .  
      The advantage of using this sealing joint  10  is to achieve a perfect join between the first contact surface  5   i  and the second contact surface  7   i  
          owing to the flexibility of the material used in that sealing joint  10 , and also to prevent loss of the pressure transmitted between said first contact surface  5   i  and the second contact surface  7   i  owing to the tightness provided by that material.        

      In an embodiment of the invention, the first contact surface  5   i  is located on a first depression  5   j  in the detachable part  2   a , 2   b  and the second contact surface  7   i  is located on a second ridge  7   k  which emerges from the outer wall of the distributor block  7  of the fixed part  1 . The sealing joint  10  fits under pressure into this first depression via its periphery.  
      The advantage of this embodiment is a better contact between the first contact surface  5   i  and the second contact surface  7   i , along with a simple and effective form of securing the sealing joint between those surfaces  5   i ,  7   i.    
      In an alternative embodiment of the invention equivalent to the above, the first contact surface  5   i  is located on a first ridge  5   k  in the detachable part  2   a , 2   b  and the second contact surface  7   i  is located on a second depression  7   j  in the outer wall of the distributor block of the fixed part  1 . The sealing joint  10  fits under pressure into this second depression  7   j  via its periphery.  
      As this embodiment is equivalent to the above, it offers the same advantages of proper contact and securing of the sealing joint  10 .  
      In an alternative embodiment of the sealing joint  10 , it consists of at least one centred opening  10   i  which favours its securing between the first contact surface  5   i  and the second contact surface  7   i.    
      In this way, in an embodiment of the invention, emerging from the second contact surface  7   i  is at least one second centred projection  7   l  which is introduced into at least one of the centred openings  10   i  fixing the sealing joint to the said second contact surface  7   i.    
      In another embodiment equivalent to the above, it is from the first contact surface  5   i  where there emerges at least one first centred projection  5   l  which is introduced into at least one of the centred openings  10   i  fixing the sealing joint to the said first contact surface  5   i.    
      The advantage of these embodiments with the centred openings  10   i  in the sealing joint and either the first centred projections  5   l  of the first contact surface  5   i  that are introduced in them, or the second centred projections  7   l  of the second contact surface  7   i  that are introduced in them, is a more secure fixing of said sealing joint  10  between the two contact surfaces  5   i , 7   i , in addition to greater ease of fitting and removal.  
      In a preferred form of these last two embodiments, the sealing joint  10  presents four centred openings  10   i  and therefore either the first contact surface  5   i  presents four first centred projections  5   l  or the second contact surface  7   i  presents four second centred projections  7   l  for introducing into said centred openings  10   i . In this way, complete stability is achieved in the fixing with the fewest number of elements.  
      In another embodiment of the invention, as shown in  FIGS. 13-16 , the second contact surface  7   i  presents a second centred projection  7   l  which traverses the centred opening  10   i  of the sealing joint  10  and penetrates into a complementary first recess  5   m  in the first contact surface  5   i.    
      In another embodiment equivalent and symmetric to the above, as shown in  FIGS. 9-12 , the first contact surface  5   i  presents a first centred projection  5   l  which traverses the centred opening  10   i  of the sealing joint  10  and penetrates into a complementary second recess  7   m  in the second contact surface  7   i.    
      The main advantage of these embodiments is an even greater security in the sealing joint  10  since it remains fixed both to the first contact surface  5   i  and to the second contact surface  7   i , and the three elements remain joined in a common block, this join preferably being carried out with four centred openings  10   i  or four second centred projections  7   l  and four complementary first recesses  5   m  or four first centred projections  5   l  and four complementary second recesses  7   m.    
      There exists a different form of embodying the invention, in which it is the first face of the sealing joint  11  which comprises at least one third centred projection  10   j , which penetrates into at least one complementary first recess  5   m  in the first contact surface  5   i.    
      In another embodiment equivalent and symmetric to the above, it is the second face of the sealing joint  12  which comprises at least one third centred projection  10   j , which penetrates into at least one complementary second recess  7   m  in the second contact surface  7   i.    
      In a more complex version of these embodiments, both the first face of the sealing joint  11  and the second face of the sealing joint  12  comprise at least a third centred projection  10   j  each, which penetrate into at least one complementary first recess  5   m  in the first contact surface  5   i  and into at least one complementary second recess  7   m  in the second contact surface  7   i , thereby achieving complete fixing of the sealing joint  10  to both contact surfaces,  5   i , 7   i.    
      As can be seen in  FIG. 17 , in a preferred form of these last two versions, the number of third centred projections  10   j  in each of the faces of the sealing joint  11 , 12  is four, as with the number of complementary first recesses  5   m  in the first contact surface  5   i  and the number of complementary second recesses  7   m  in the second contact surface  7   i.    
      The pressure connection system without pipes of the present invention permits pressure tappings and connections to be made in very small size pieces, in such a way that the parts that are connected can have a surface area of the order of several square millimetres. The holes can therefore be of the order of several tenths of a millimetre.