Abstract:
A turbocharger ( 5 ) comprising a housing ( 10 ) including a compressor shroud ( 14 ) and a turbine shroud ( 12 ). A compressor wheel ( 18 ) is disposed in the compressor shroud ( 14 ) and includes a plurality of compressor blades ( 45, 46 ). Each compressor blade ( 45, 46 ) includes a leading edge ( 50, 51 ) and a compressor shroud contour edge ( 54, 55 ), wherein each compressor shroud contour edge ( 54, 55 ) is in close confronting relation to the compressor shroud ( 14 ). A turbine wheel ( 16 ) is disposed in the turbine shroud ( 12 ) and includes a plurality of turbine blades ( 26 ). Each turbine blade ( 26 ) includes a leading edge ( 30 ) and a turbine shroud contour edge ( 34 ), wherein each turbine shroud contour edge ( 34 ) is in close confronting relation to the turbine shroud ( 12 ). At least one of the compressor shroud ( 14 ) and turbine shroud ( 12 ) includes a plurality of grooves ( 70, 72 ) extending cross-wise with respect to the corresponding compressor or turbine shroud contour edges ( 34, 54, 55 ).

Description:
BACKGROUND 
       [0001]    Today&#39;s internal combustion engines must meet ever-stricter emissions and efficiency standards demanded by consumers and government regulatory agencies. Accordingly, automotive manufacturers and suppliers expend great effort and capital in researching and developing technology to improve the operation of the internal combustion engine. Turbochargers are one area of engine development that is of particular interest. 
         [0002]    A turbocharger uses exhaust gas energy, which would normally be wasted, to drive a turbine. The turbine is mounted to a shaft that in turn drives a compressor. The turbine converts the heat and kinetic energy of the exhaust into rotational power that drives the compressor. The objective of a turbocharger is to improve the engine&#39;s volumetric efficiency by increasing the density of the air entering the engine. The compressor draws in ambient air and compresses it into the intake manifold and ultimately the cylinders. Thus, a greater mass of air enters the cylinders on each intake stroke. 
         [0003]    The more efficiently the turbine can convert the exhaust heat energy into rotational power and the more efficiently the compressor can push air into the engine, the more efficient the overall performance of the engine. Accordingly, it is desirable to design the turbine and compressor wheels to be as efficient as possible. However, various losses are inherent in traditional turbine and compressor designs due to turbulence and leakage. 
         [0004]    While traditional turbocharger compressor and turbine designs have been developed with the goal of maximizing efficiency, there is still a need for further advances in compressor and turbine efficiency. 
       SUMMARY 
       [0005]    Provided herein is a turbocharger comprising a housing including a compressor shroud. A compressor wheel is disposed in the compressor shroud and includes a plurality of compressor blades. Each compressor blade includes a leading edge and a shroud contour edge, wherein each shroud contour edge is in close confronting relation to the compressor shroud. The compressor shroud includes a plurality of grooves extending cross-wise with respect to the shroud contour edges of the compressor blades. 
         [0006]    In certain aspects of the technology described herein, the grooves are equally spaced. The compressor shroud includes an inlet region and discharge region, and the grooves extend from the inlet region to the discharge region. In an embodiment, the grooves extend arcuately from the inlet region to the discharge region. The grooves may have a rectangular cross-section, for example. 
         [0007]    Also provided herein is a turbocharger comprising a housing including a turbine shroud. A turbine wheel is disposed in the turbine shroud and includes a plurality of turbine blades. Each turbine blade includes a leading edge and a shroud contour edge, wherein each shroud contour edge is in close confronting relation to the turbine shroud. The turbine shroud includes a plurality of grooves extending cross-wise with respect to the shroud contour edges of the turbine blades. 
         [0008]    Also contemplated is a turbocharger comprising a housing including a compressor shroud and a turbine shroud. A compressor wheel is disposed in the compressor shroud and includes a plurality of compressor blades. Each compressor blade includes a leading edge and a compressor shroud contour edge, wherein each compressor shroud contour edge is in close confronting relation to the compressor shroud. A turbine wheel is disposed in the turbine shroud and includes a plurality of turbine blades. Each turbine blade includes a leading edge and a turbine shroud contour edge, wherein each turbine shroud contour edge is in close confronting relation to the turbine shroud. At least one of the compressor shroud and turbine shroud includes a plurality of grooves extending cross-wise with respect to the corresponding compressor or turbine shroud contour edges. 
         [0009]    These and other aspects of the turbocharger shroud with cross-wise grooves and turbocharger incorporating the same will be apparent after consideration of the Detailed Description and Figures herein. It is to be understood, however, that the scope of the invention shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the background or includes any features or aspects recited in this summary. 
     
    
     
       DRAWINGS 
         [0010]    Non-limiting and non-exhaustive embodiments of the turbocharger shroud with cross-wise grooves and turbocharger incorporating the same, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
           [0011]      FIG. 1  is a side view in a cross-section of a turbocharger according to an exemplary embodiment; 
           [0012]      FIG. 2  is a perspective view of a turbine wheel according to a first exemplary embodiment; 
           [0013]      FIG. 3  is an enlarged partial perspective view of the turbine wheel shown in  FIG. 2 ; 
           [0014]      FIG. 4  is a perspective view of a compressor wheel according to a first exemplary embodiment; 
           [0015]      FIG. 5  is an enlarged partial perspective view of the compressor wheel shown in  FIG. 4 ; 
           [0016]      FIG. 6  is a side view diagram representing one of the turbine blades shown in  FIG. 3 ; 
           [0017]      FIGS. 7A-7D  are partial cross-sections of the turbine blade taken about line  7 - 7  in  FIG. 6  showing different edge relief configurations; 
           [0018]      FIG. 8  is a perspective view representing the interface of a turbine wheel and the inner surface of a turbine shroud according to an exemplary embodiment; 
           [0019]      FIG. 9  is a perspective view representing the interface between a compressor wheel and the inner surface of a compressor shroud according to an exemplary embodiment; 
           [0020]      FIG. 10  is a perspective view illustrating a turbine wheel, according to a second exemplary embodiment, incorporating hub surface discontinuities; 
           [0021]      FIG. 11  is a side view in cross-section of the turbine wheel taken about lines  11 - 11  in  FIG. 10 ; 
           [0022]      FIG. 12  is a perspective view of a turbine wheel, according to a third exemplary embodiment, illustrating an alternative surface discontinuity configuration; 
           [0023]      FIG. 13  is a perspective view of a turbine wheel, according to a fourth exemplary embodiment, illustrating another alternative surface discontinuity configuration; and 
           [0024]      FIG. 14  is a perspective view of a turbine wheel, according to a fifth exemplary embodiment, illustrating yet another alternative surface discontinuity configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense. 
         [0026]    As shown in  FIG. 1 , turbocharger  5  includes a bearing housing  10  with a turbine shroud  12  and a compressor shroud  14  attached thereto. Turbine wheel  16  rotates within the turbine shroud  12  in close proximity to the turbine shroud inner surface  20 . Similarly, the compressor wheel  18  rotates within the compressor shroud  14  in close proximity to the compressor shroud inner surface  22 . The construction of turbocharger  5  is that of a typical turbocharger as is well known in the art. However, turbocharger  5  includes various improvements to efficiency which are explained more fully herein. 
         [0027]    As shown in  FIG. 2 , turbine wheel  16  includes a hub  24  from which a plurality of blades  26  extend. Each blade  26  includes a leading edge  30  and a trailing edge  32  between which extends a shroud contour edge  34 . The shroud contour edge is sometime referred to herein as the tip of the blade. In traditional turbine wheel configurations, a significant loss of turbine efficiency is due to leakages across the tip of the turbine blades. The physics of the flow between the turbine blades results in one surface of the blade (the pressure side  36 ) being exposed to a high pressure, while the other side (the suction side  38 ) is exposed to a low pressure (see  FIG. 3 ). This difference in pressure results in a force on the blade that causes the turbine wheel to rotate. With reference again to  FIG. 1 , it can be seen that shroud contour edge  34  is in close proximity to turbine shroud inner surface  20 , thereby forming a gap between them. These high and low pressure regions cause secondary flow to travel from the pressure side  36  of the turbine blade to the suction side  38  through the gap between the turbine blade tip  34  and the inner surface  20  of the turbine shroud. This secondary flow is a loss to the overall system and is a debit to turbine efficiency. Ideally, there would not be a gap between the tip and shroud, but a gap is necessary to prevent the tip from rubbing on the shroud and to account for thermal expansion and centrifugal loading on the turbine blades which causes the blades to grow radially. 
         [0028]    In this embodiment, however, turbine blades  26  include an edge relief  40  formed along the tip or shroud contour edge  34 . In this case, when flow travels through the gap, the edge relief  40  creates a high pressure region in the edge relief (relative to the pressure side  36 ) which causes the flow to stagnate. In addition, the high pressure region causes the flow across the gap to become choked, thereby limiting the flow rate. Therefore, the secondary flow is reduced which increases the efficiency of the turbine. As can be appreciated from  FIG. 3 , in this case the edge relief  40  extends along a majority of the shroud contour edge  34  without extending past the ends of the edge of the blade. This creates a pocket or a scoop that further acts to create relative pressure in the edge relief. 
         [0029]    With further reference to  FIG. 6 , edge relief  40  is shown schematically along shroud contour edge  34 . The cross-section of blade  26  shown in  FIG. 7A  illustrates the profile configuration of the edge relief  40 . In this case, the edge relief is shown as a cove having an inner radius. Although shown here in the form of a cove, the edge relief could be formed as a chamfer, a radius, or a rabbet as shown in  FIGS. 7B-7D , respectively. As indicated in  FIGS. 7A-7D , edge relief  40  is formed into the pressure side  36  of blade  26 . The remaining edge material of the shroud contour edge is represented as thickness t in  FIGS. 7A-7D . It has been found that minimizing the thickness t of the remaining tip causes the flow to choke more quickly. The thickness t may be expressed as a percentage of the blade thickness. For example, thickness t should be less than 75% of the blade thickness and preferably less than 50% of the blade thickness. However, the minimum thickness is ultimately determined by the technology used to create the edge relief. The relief may be machined or cast into the edge of the blade. Accordingly, the edge relief is a cost effective solution to improve efficiency of the turbine and compressor wheels. 
         [0030]    With reference to  FIGS. 4 and 5 , it can be appreciated that the blades  45  and  46  of compressor wheel  18  may also be formed with edge reliefs  61  and  60 , respectively. In this case, compressor wheel  18  includes a hub  44  from which radially extend a plurality of blades  46  with a plurality of smaller blades  45  interposed therebetween. With reference to  FIG. 5 , each blade  46  includes a leading edge  50 , a trailing edge  52 , and a compressor shroud contour edge  54  extending therebetween. In similar fashion, the smaller blades  45  include a leading edge  51 , a trailing edge  53 , and a shroud contour edge  55  extending therebetween. Edge reliefs  61  and  60  extend along a majority of their respective shroud contour edges. As with the turbine wheel blades, the edge reliefs are formed along the pressure side of the blade. Thus, in the case of the compressor blades, the edge reliefs  60  and  61  are formed on the pressure side  56 , as shown in  FIG. 5 . Similar to the turbine blade edge reliefs, the compressor blade edge reliefs reduce flow from the pressure side  56  to the suction side  58 , thereby increasing the efficiency of the compressor wheel. 
         [0031]    Another way to disrupt the flow from the pressure side to the suction side of turbocharger turbine and compressor blades is shown in  FIGS. 8 and 9 . As shown in  FIG. 8 , the turbine shroud inner surface  20  includes a plurality of grooves  70  that extend crosswise with respect to the shroud contour edges  34  of the turbine blades  26 . Therefore, the grooves extend at an angle G with respect to the axis A of turbine wheel  16 . The angle G is related to the number of blades on the compressor or turbine wheel. In one embodiment, for example, the angle G is adjusted such that the grooves cross no more than two adjacent blades. In this case, the grooves are rectangular in cross-section and have a width w and a depth d. As an example, the width may range from approximately 0.5 to 2 mm and the depth may range from approximately 0.5 to 3 mm. The grooves extend arcuately from the inlet region  74  to the discharge region  76  of the shroud surface  20 . As can be appreciated, the grooves are circumferentially spaced equally about the shroud surface at a distance S. However, in other embodiments, the spacing may vary from groove to groove. Distance S has a limitation similar to the angle G, in that the spacing is limited by the number of blades. As an example, S may be limited by having no more than  15  grooves crossing a single blade. 
         [0032]    With reference to  FIG. 9 , the compressor shroud surface  22  also includes a plurality of grooves  72  formed in the inner surface  22  of the compressor shroud  14 . Grooves  72  extend crosswise with respect to the shroud contour edges  54  and  55  of blades  46  and  45 , respectively. In this case, the grooves extend arcuately from the inlet region  73  to the discharge region  77  of the shroud surface  22 . While the grooves  70  and  72  are shown here to have rectangular cross-sections, other cross-sections may work as well, such as round or V-shaped cross-sections. As the shroud contour edge of each blade passes the crosswise-oriented grooves, the flow across the tip or shroud contour edge is disrupted (stagnated) by turbulence created in the grooves. 
         [0033]    As yet another way to increase the efficiency of the turbine and compressor wheels, the wheels may include a surface discontinuity around the hub. As shown in  FIGS. 10-14 , the turbine wheel may include a surface discontinuity formed around the hub of the turbine wheel to impart energy into the boundary layer of a fluid flow associated with the hub. For example,  FIG. 10  illustrates an exemplary embodiment of a turbine wheel  116  having a hub  124  with a pair of circumferentially-extending ribs  135  that are operative to energize a boundary layer of a fluid flow F associated with hub  124 . The blades  126  are circumferentially spaced around the turbine hub  124  with a hub surface  125  extending between adjacent blades. Each surface  125  includes at least one surface discontinuity, in this case, in the form of ribs  135 . As shown in  FIG. 11 , the cross-section of the hub indicates a concave outer surface  125  extending between each blade with the surface discontinuity or ribs  135  protruding therefrom. In this case, the ribs act to accelerate the flow F over each rib, thereby energizing the boundary layer of fluid flow associated with the hub in order to disrupt the formation of vortices that impact turbine efficiency.  FIG. 12  illustrates a turbine wheel  216  according to another exemplary embodiment. In this case, turbine wheel  216  includes a hub  224  with a plurality of blades  226  extending radially therefrom. A hub surface  225  extends between each adjacent turbine blade  226 . In this case, the surface discontinuities are in the form of a plurality of protuberances  235 . These protuberances could be in the form of bumps, disks, ribs, triangles, etc. As shown in  FIGS. 13 and 14 , the turbine wheels include surface discontinuities in the form of dimples or grooves. For example,  FIG. 13  illustrates hub surface  325  extending between adjacent turbine blades  326  and includes a plurality of surface discontinuities in the form of dimples  335 . Dimples  335  may be similar to those found on a golf ball. In  FIG. 14 , turbine wheel  416  includes a hub  424  with hub surfaces  425  extending between adjacent blades  426 . In this case, the surface discontinuities are in the form of grooves  435  extending circumferentially around hub  424 . 
         [0034]    Accordingly, the turbocharger shrouds with cross-wise grooves have been described with some degree of particularity directed to the exemplary embodiments. It should be appreciated; however, that the present invention is defined by the following claims construed in light of the prior art so that modifications or changes may be made to the exemplary embodiments without departing from the inventive concepts contained herein.