Abstract:
An air induction system consisting of a cylindrical main flow tube, a helical vane disposed within the main flow tube, and, preferably, a noise absorbing perforated tube disposed within the main flow tube in concentric relation to the helical vane. The twist direction of the helical vane provides air flow rotation in the same direction of rotation as the turbine wheel. The helical vane causes noise reflection and enhancement of noise attenuation by the perorated tube and its adjoining one or more acoustic cavities.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to air induction systems for turbochargers, and more particularly to an air induction system which imparts air flow rotation upstream of, and rotationally in the same direction as, the turbocharger turbine wheel, and which, further, attenuates turbocharger noise. 
       BACKGROUND OF THE INVENTION 
       [0002]    Turbochargers for internal combustion engines utilize a rotating turbine wheel to draw air from an upstream air induction housing and deliver the air, now under compression, to a downstream engine intake manifold. Problematically, the turbocharger requires power to operate, inclusive not only of the power needed to rotate the turbine wheel but also to overcome pressure losses in the air induction housing. Problematically further, the turbocharger produces noise during its operation which can undesirably exit at the air entry port of the air induction housing. 
         [0003]    When an air induction system for a turbocharger is designed, taken into account, for example, are air flow mechanics, vehicle dynamics, material science, and manufacturing processes, as well as other factors as may pertain to the system application. Minimization of pressure loss at the air intake housing and lowering of turbocharger noise exiting therefrom are a challenge, particularly in view of increasing demands for improved engine performance, turbocharger drivability, fuel economy, and emissions reduction. Accordingly, turbocharger air induction systems have become highly engineered products, integrating sensors, vibration decoupling, noise tuners and emission control devices, among others. As a result of these integrated components, air induction systems are prone to being ever more air flow restrictive. 
         [0004]    Accordingly, what remains in the art of turbocharger air induction housings is to somehow engineer an air induction housing which minimizes pressure losses, assists the functionality of the turbine wheel, and minimizes escape of turbocharger noise. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is an improved air induction system for a turbocharger which minimizes pressure losses, assists the functionality of the turbine wheel, and minimizes escape of turbocharger noise. 
         [0006]    The improved air induction system according to the present invention consists of a cylindrical main flow tube, a helical vane disposed within the main flow tube, and, preferably, a noise absorbing perforated tube disposed within the main flow tube in concentric relation to the helical vane such that the helical vane and the perforated tube are concentrically positioned in the air flow path of the main flow tube. 
         [0007]    The helical vane has a spiraling body which twists axially along the main flow tube so as to guide air flow axially along the main flow tube and thereby cause the flowing air to acquire a rotation. The twist direction of the spiraling body of the helical vane is coordinated with the known rotation direction of the turbine wheel of the turbocharger so that the acquired rotation of the flowing air is in the same direction of rotation as that of the turbine wheel. 
         [0008]    The noise absorbing perforated tube is separated from the main flow tube so as to form an acoustic cavity between the sidewall of the main flow tube and the sidewall of the perforated tube. The perforated tube dissipates acoustic energy via the perforations and the acoustic cavity when sound waves propagate through the air flow of the air induction housing. 
         [0009]    The length of the perforated tube, the size of the acoustic cavity, the perforation distribution, and the helical twist angle of the helical vane are among the parameters which may be varied to achieve the desired performance levels of air flow rotation and noise attenuation for a particular application. 
         [0010]    The acquired air flow rotation provided by the air induction system according to the present invention has a number of advantages. Because the acquired air flow rotation is in the same rotational direction as the turbine wheel rotation, the dynamic pressure load on the compressor blades is reduced. This pressure load reduction increases turbocharger efficiency and more than compensates for the pressure loss of the air intake housing. As a consequence, the turbine wheel generates less heat, vibration and noise, with the added benefit of improved durability. An additional advantage involves the synergism of the helical vane with respect to the perforated tube, in that the acquired rotation of the air flow encourages sound waves to deflect their propagation direction so as to pass radially through the perforations and into the acoustic cavity, thereby reducing noise from the turbocharger exiting the air entry port of the air induction housing. In addition, the spiral vane reflects acoustic energy back into the turbocharger due to a change in acoustic impedance. Therefore, the combination of the helical vane and the perforated tube serves to rotate the air flow, deflect sound waves into the perforations and reflect sound waves (i.e., acoustic energy) back to turbocharger. 
         [0011]    Accordingly, it is an object of the present invention to provide a turbocharger air induction housing which minimizes pressure losses, assists the functionality of the turbine wheel, and minimizes escape of turbocharger noise. 
         [0012]    This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective elevational view of an improved air induction system according to the present invention. 
           [0014]      FIG. 2  is a perspective elevational view of the improved air induction system as in  FIG. 1 , shown operatively connected to a turbocharger. 
           [0015]      FIG. 3  is a partly sectional view, seen along line  3 - 3  of  FIG. 1 . 
           [0016]      FIG. 4  is a side view of a helical vane according to the present invention. 
           [0017]      FIG. 5  is a side perspective view of a perforated cylinder according to the present invention. 
           [0018]      FIG. 6  is a side view of the perforated cylinder of  FIG. 5 , showing in phantom the concentrically disposed helical vane of  FIG. 4 . 
           [0019]      FIG. 7  is an end view, seen along line  7 - 7  of  FIG. 6 . 
           [0020]      FIG. 8  is a perspective sectional view of the improved air induction system according to the present invention, shown operatively with respect to turbocharger induced air flow therewithin. 
           [0021]      FIG. 9  is a sectional view of the improved air induction housing as in  FIG. 8 , now schematically further showing noise deflection and reflection aspects during the air flow. 
           [0022]      FIG. 10  is a perspective elevational view of an improved air induction system main flow tube in the form of an elbow, wherein disposed therewithin is a spiral vane according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    Referring now to the Drawings,  FIGS. 1 through 10  depict examples of an improved air induction system for a turbocharger which minimizes pressure losses, assists the functionality of the turbine wheel, and minimizes escape of turbocharger noise. 
         [0024]      FIGS. 1 through 3  depict an example of an improved air induction system  100 , showing an exemplar air induction housing  102  thereof, which may have other configurations (see for example the discussion hereinbelow of  FIG. 10 ). The air induction housing  102  is connected to a turbocharger  104 . Internal to the turbocharger  104  is a turbine wheel  106  having blades  106 ′ which rotate in a predetermined direction of rotation  124  so as to draw air from the upstream disposed air induction housing  102  and deliver the air, now under compression, to a downstream engine intake manifold (not shown). 
         [0025]    The air induction housing  102  includes a cylindrical main flow tube  108 . Disposed within the main flow tube  108  is a helical vane  110 , and, preferably, disposed between the helical vane  110  and the main flow tube  108  is a noise absorbing perforated tube  112 . The helical vane  110  and the perforated tube  112  are mutually disposed within the main flow tube  108  such that the helical vane and the perforated tube are concentrically positioned in the air flow  114  (see  FIG. 8 ) of the main flow tube. The helical vane  110  imparts to the air flow  114  an acquired air flow rotation  122  which rotation is in the same direction of rotation as that of the turbine wheel  106 . 
         [0026]    As best shown at  FIG. 4 , the helical vane  110  has a spiraling body  116  which twists axially (see axis  118 ). This twist  120  of the spiraling body  116  is also axially along the main flow tube  108 , and consequently acts to guide the air flow  114  axially along the main flow tube and thereby cause the air flow to acquire the air flow rotation  122 . The direction of the twist  120  of the spiraling body  116  of the helical vane  110  is coordinated with the predetermined direction of rotation  124  of the turbine wheel  106  of the turbocharger  104  so that the acquired air flow rotation  122  of the air flow  114  is in the same direction of rotation as the rotation direction of the turbine wheel. The twist  120  provided by a helical twist angle  128  is preselected based upon, among various aspects, the anticipated rate of the air flow  114 , as well as the length and diameter of the helical vane  110  so as to provide a desired acquired air flow rotation  122  is in best agreement with the operational characteristics of the turbine wheel  106 . Merely by way of example,  FIG. 4  shows the helical vane  110  having a 1.5 twist over a length of 120 mm; however, the twist per unit length can be any value suitable for a particular application. 
         [0027]    Turning attention now to  FIG. 5 , the noise absorbing perforated tube  112  is spaced in relation to the main flow tube  108  so as to form at least one acoustic cavity  130  (six acoustic cavities being provided at  FIGS. 8 and 9 ) disposed between the main flow tube sidewall  108 ′ of the main flow tube and the perforated tube sidewall  112 ′ of the perforated tube. The separation spacing  132  is defined by a radially disposed embossment  134 , which includes first and second boss seals  136 ,  138  at each end of the perforated tube  112 . The perforated tube  112  has a multiplicity of perforations  140  formed in the perforated tube sidewall  112 ′. The perforated tube  112  serves to dissipate acoustic energy via the perforations  140  in conjunction with the acoustic cavity or cavities  130  when sound waves propagate through the air flow  114  of the air induction housing  102 . 
         [0028]    As shown generally at  FIGS. 3 ,  8  and  9 , the outer periphery  142  of the helical vane  110  is connected (stationarily and sealingly) to the perforated tube sidewall  112 ′. In addition, the embossment  134  of the perforated tube  112  is connected (stationarily and sealingly) to the main flow tube sidewall  108 ′, whereby the helical vane  110  is connected (stationarily and sealingly) to the main flow tube  108 . 
         [0029]    Turning attention now to  FIGS. 8 and 9 , operational aspects of the improved air induction system  100  will be detailed. 
         [0030]    As shown at  FIG. 8 , air flow  114  induced by the aforementioned turbine wheel passes through the air induction housing  102 , encountering the main flow tube  108 . The helical vane  110  imparts to the air flow  114  an acquired air flow rotation  122  as the air flow passes guidingly along the surfaces of the spiraling body  116 , wherein the direction of rotation of the air flow rotation  122  is the same as the direction of rotation  124  of the turbine wheel  106  (see  FIG. 2 ). 
         [0031]    As shown at  FIG. 9 , noise (i.e., sound waves or acoustic energy)  150  emanating from the turbine wheel (see  FIG. 2 ) travels into the air induction housing  102  upstream of the flow direction of the air flow  114 . Upon reaching the main flow tube  108 , the noise  150  encounters the helical vane  110 . An abrupt change in acoustic impedance occurs, which causes a portion of the noise  150  to be reflected and thereupon become reverse directed noise  152  traveling back toward the turbocharger (see  FIG. 2 ). In addition, as the remaining noise  150 ′ travels through the perforated tube  112 , and some of the remaining noise  150 ″ is pass into the perorations  140 , where it is deadened by the acoustic cavity or cavities  130 , wherein the air flow rotation  122  tends to deflect the remaining noise into the perforations  140 , whereby acoustic deadening of the remaining noise is enhanced. The result of the reflection, deflection and deadening of the noise is such that the exiting noise  150 ′″ is much attenuated as compared to the original noise  150 . 
         [0032]    The length of the perforated tube  112 , the size of the acoustic cavity or cavities  130 , the distribution and size of perforations  140 , the helical twist angle  128  of the helical vane  110  are among the parameters which may be varied to achieve the desired performance levels of acquired air flow rotation  116  and noise attenuation for a particular application. 
         [0033]    The acquired air flow rotation  122  provided by the improved air induction system  100  of the present invention has a number of advantages: reduction of the dynamic pressure load on the blades of the turbine wheel; increased turbocharger efficiency; generation of less heat, vibration and noise; and improved turbocharger durability. 
         [0034]    With regard to noise attenuation, the synergism of the helical vane with respect to the perforated tube enhances noise attenuation of the acoustic cavity. In addition, the spiral vane reflects acoustic energy back in to turbocharger due to a change in acoustic impedance. 
         [0035]    The combination of the helical vane and the perforated tube serves to rotate the air flow, deflect turbocharger noise into the perforations of the perforated tube where they are attenuated by the acoustic cavity, and reflect noise back to turbocharger. 
         [0036]      FIG. 10  depicts an example of an intake housing system  100 ′ of the present invention, wherein the main flow tube  1108  is curved, as for example at an elbow, wherein disposed therewithin is a helical vane  1110  having a periphery  1110 ′ which is (stationarily and sealingly) connected to the main flow tube. 
         [0037]    To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.