Abstract:
Disclosed is an air intake for a turbocharger for an internal combustion engine, said air intake including a series of variable position guide vanes for directing the air such that it is swirling in a rotational sense on reaching the impeller of the compressor of the turbocharger. The variable position guide vanes are made comprised of sound absorbent material such as to achieve a substantial reduction in turbocharger noise at the air intake.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage of International Application No. PCT/EP2006/062610, filed May 24, 2006 and claims the benefit thereof. The International Application claims the benefits of British application No. 0510994.7 GB filed May 28, 2005, both of the applications are incorporated by reference herein in their entirety. 
     FIELD OF INVENTION 
     The present invention relates to an air intake for a turbocharger for an internal combustion engine, e.g. a diesel engine. 
     BACKGROUND OF INVENTION 
     Air intakes perform the following functions: they filter the air; they guide the air prior to it reaching the impeller of the compressor of the turbocharger; and they attenuate the noise produced by the turbocharger as emitted by the air inlet to the air intake. 
     The noise attenuation is achieved through the use of baffle structures and acoustically absorbent lining in the air intake. 
     A problem arises that the geometrical form of the baffle structures is not ideal across the full operating range of the turbocharger/engine. The directing of the air by the baffle structures is such that the air approaches the impeller in a certain direction. This certain direction is not ideal at the extremes of the operating range of the turbocharger/engine. This results in a reduction in turbocharger/engine efficiency as well as increased noise at these extremes. 
     It is known to add a variable guide vane arrangement to the air intake to direct the air dependent on operation of the turbocharger/engine so that the air approaches the impeller in a direction best suited to turbocharger/engine operation. However, the addition to the air intake of a further component, together with its associated aerodynamic loss, has the undesirable effect of increasing overall aerodynamic loss in the air intake. Further, existing variable guide vane arrangements are complex and expensive. 
     SUMMARY OF INVENTION 
     According to the present invention there is provided an air intake for a turbocharger for an internal combustion engine, the air intake including a series of variable position guide vanes for directing the air such that it is swirling in a rotational sense on reaching the impeller of the compressor of the turbocharger, wherein the variable position guide vanes are made comprised of sound absorbent material such as to achieve a substantial reduction in turbocharger noise at the air intake. 
     Preferably, each variable position guide vane comprises more than one vane part, the vane parts being movable relative to one another, the relative movement of the vane parts of the variable position guide vanes effecting variation in the amount and/or rotational sense of the swirl applied by the variable position guide vanes. 
     The vane parts comprising each variable position guide vane may include a fixed vane part. 
     Preferably, each variable position guide vane comprises two vane parts. 
     In the air intake described below by way of example, each variable position guide vane comprises a fixed vane part and a movable vane part, movement of the movable vane parts of the variable position guide vanes effecting variation in the amount and/or rotational sense of the swirl applied by the variable position guide vanes. 
     Further, in the air intake described below, the series of variable position guide vanes are arranged in a circle, and the fixed vane parts of the guide vanes are disposed radially outward of the movable vane parts of the guide vanes. 
     Further, in the air intake described below, in each variable position guide vane the fixed vane part and the movable vane part are secured end to end, and the movable vane part is rotatable about an axis perpendicular to the plane of the circle, which axis is located at the securing end to end of the fixed and movable vane parts. 
     In each variable position guide vane the fixed and movable vane parts are suitably secured end to end in the form of a hinge, the axis of the hinge constituting the axis perpendicular to the plane of the circle. 
     In each variable position guide vane both the fixed and movable vane parts suitably comprise a perforated metal sheet envelope containing sound absorbent material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is an exploded perspective view of a portion of an air intake according to the present invention, which portion includes a series of variable position guide vanes; 
         FIG. 2  is a section through the air intake according to the present invention, which section omits an air filter of the air intake; 
         FIG. 3  is a section taken on the line III-III in  FIG. 2 ; 
         FIG. 4  is a view on the arrow IV in  FIG. 3  with an end cover of the air intake removed; 
         FIG. 5  is a perspective view of a single variable position guide vane of the series of such guide vanes; and 
         FIGS. 6 and 7  are half sections corresponding to  FIG. 2 , and illustrate the series of variable position guide vanes in operation. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to  FIGS. 1 to 4 , the air intake  1  comprises: a series of variable position guide vanes  3  arranged in a circle about an axis A; an end cover  5  and an outlet flange  7  between which guide vanes  3  are secured; a foam air filter  9  that extends circumferentially around the circle of guide vanes  3 ; a location ring  11 ; and an actuator  13 . 
     Each variable position guide vane  3  comprises a fixed vane part  15  and a movable vane part  17 . Each fixed vane part  15  includes at its radially outer end a first post  19 . Further, each vane part  15  includes at its radially inner end a second post  21 . First and second posts  19 ,  21  secure vane parts  15  in position between end cover  5  and outlet flange  7 . Each movable vane part  17  at its radially outer end shares the second post  21  of its associated fixed vane part  15 . Each movable vane part  17  is able to rotate about its respective second post  21 . Each vane part  17  includes at its radially inner end a third post  23 , which post  23  includes a spigot  25 . 
     The spigots  25  of the third posts  23  locate into respective slots  27  in location ring  11 . Location ring  11  includes a projection  29 , which projection extends through an aperture in end cover  5 . Actuator  13  is connected to projection  29 . Actuator  13  is able to rotate location ring  11  in a clockwise or anticlockwise sense about axis A. This in turn moves spigots  25  and third posts  23  circumferentially around axis A, thereby rotating each movable vane part  17  by the same amount and in the same clockwise/anticlockwise sense about its respective second post  21 . 
     Referring also to  FIG. 5 , the fixed vane part  15  of each variable position guide vane  3  comprises a curved perforated steel sheet envelope  31  that extends between the first and second posts  19 ,  21 , and contained within the envelope a sound absorbent foam mass  33 . Similarly, the movable vane part  17  of each variable position guide vane  3  comprises a curved perforated steel sheet envelope  35  that extends between the second and third posts  21 ,  23 , and contained within the envelope a further sound absorbent foam mass  37 . The fixed and movable vane parts  15 ,  17  share second post  21  by forming a hinge thereat. 
     In operation of the air intake, rotation of the impeller of the compressor of the turbocharger (this impeller would be located to the right in  FIG. 3  and would rotate about axis A) causes air to be drawn radially inwardly in the direction of arrows  39  in  FIGS. 2 and 3 . The air travels through foam air filter  9  and guide vanes  3 , and between end cover  5  and outlet flange  7 . Guide vanes  3  direct the air so as to cause it swirl in a clockwise or anticlockwise sense about axis A, or not at all, as the air is drawn towards the impeller. The amount and sense of the swirl is determined by the setting of the movable vane parts  17  of guide vanes  3 . Arrows  41  in  FIG. 2  indicate that the setting of movable vane parts  17  in  FIG. 2  is such that no swirl is applied by guide vanes  3 . Arrows  43  in  FIG. 3  indicate the drawing of the air towards the impeller. A conical protrusion  45  in end cover  5  assists in the aerodynamics of the air intake. 
     In  FIG. 2  movable vane parts  17  occupy their mid-position. In this position guide vanes  3  apply no swirl.  FIGS. 6 and 7  show the settings of movable vane parts  17  such that guide vanes  3  apply clockwise and anticlockwise swirl respectively, as indicated by arrows  47 ,  49 . Thus, to achieve clockwise swirl, movable vane parts  17  are rotated about second posts  21  in an anticlockwise sense. Similarly, to achieve anticlockwise swirl, vane parts  17  are rotated about posts  21  in a clockwise sense. The amount of clockwise/anticlockwise swirl applied of course depends on the degree of rotation of vane parts  17 . 
     The setting of movable vane parts  17  is determined according to the operating state of the turbocharger/engine. This setting is of course adjusted by operation of actuator  13 . The setting is chosen so that the swirl applied by guide vanes  3  is such that the air approaches the impeller in a direction as desired for the particular state of operation. It is to be noted that by having the capability of applying both clockwise and anticlockwise swirl, variable position guide vanes  3  are able to apply swirl that is in the same sense or the opposite sense to that in which the impeller rotates. Thus, guide vanes  3  are able to apply so called positive (same sense) or negative (opposite sense) swirl of varying amounts prior to the impeller, as required according to operation of the turbocharger/engine. 
     In accordance with the present invention, guide vanes  3 , in addition to being able to apply varying amounts of clockwise/anticlockwise swirl, also operate to attenuate turbocharger noise that would otherwise be emitted by the air inlet to the air intake. Guide vanes  3  have this property by virtue of their construction comprised of sound absorbent material. 
     It is to be appreciated that the air intake described above incorporates into one and the same component (i.e. the series of variable position guide vanes  3 ) both the operation of applying varying amounts of clockwise/anticlockwise swirl and the operation of absorbing sound. Thus, the overall aerodynamic loss of the air intake is reduced as compared to an air intake in which these two operations are carried out by separate dedicated components. 
     In the air intake described above, each variable position guide vane  3  comprises two vane parts  15 ,  17 , one movable, the other not, and both made comprised of sound absorbent material. It is to be realised that each variable position guide vane could comprise only one vane part, which vane part is both movable and made comprised of sound absorbent material, thereby to have the dual property of being able to apply varying amounts of clockwise/anticlockwise swirl and absorb sound. 
     In the air intake described above, each variable position guide vane  3  comprises two vane parts  15 ,  17 , one movable, the other not. It is to be realised that these two vane parts could both be movable, moving in synchronised relation in order to apply the required amount of clockwise/anticlockwise swirl. 
     In the air intake described above, each variable position guide vane  3  comprises two vane parts  15 ,  17 . It is to be realised that each variable position guide vane could comprise three or more vane parts. 
     In the air intake described above, in each variable position guide vane  3 , fixed and movable vane parts  15 ,  17  are hinged together. It is to be realised that this hinge may be omitted, and vane parts  15 ,  17  disposed separately but closely adjacent. Thus, fixed vane part  15  would extend as before from first post  19  to second post  21 , but movable vane part  17  would not share second post  21 . Movable vane part  17  would rotate about a further post positioned closely adjacent second post  21 . 
     In the air intake described above, in each variable position guide vane  3 , fixed and movable vane parts  15 ,  17  are of the same construction. It is to be realised that their construction may be different provided the resulting series of variable position guide vanes achieves the required turbocharger noise reduction. For example, and provided the required noise reduction can be achieved, movable vane part  17  might be made of a non-sound absorbent material. 
     In the air intake described above, each variable position guide vane  3  comprises a fixed vane part  15  and a movable vane part  17 , both parts sound absorbent, and variation in the amount/direction of the swirl applied is achieved by rotating the movable vane part  17 . It is to be realised that this two-part guide vane  3  could be replaced by a one-part guide vane comprising a single vane of laminar form, made of sound absorbent material, and having the property that it is able to flex or bow thereby to achieve the required variation in the amount/direction of the swirl applied. The flexing or bowing could suitably be realised by substantially circumferential movement about the axis A of one or both of the radially inner/outer ends of the single vane.