Patent Publication Number: US-2023142571-A1

Title: Compressor housing

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to turbochargers and, more particularly, to turbochargers with burst containment in the event of compressor impeller failure. 
     BACKGROUND 
     Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines, employ turbochargers to deliver compressed air for combustion in the engine. A turbocharger compresses air flowing into the engine, helping to force more air into combustion chambers of the engine. The increased supply of air allows for increased fuel combustion in the combustion chambers of the engine, resulting in increased power output from the engine. 
     A typical turbocharger includes a shaft, a turbine wheel connected to one end of the shaft, a compressor impeller (sometimes referred to as a compressor wheel) connected to the other end of the shaft, and bearings to support the shaft. Separate housings connected to each other enclose the compressor impeller, the turbine wheel and the bearings. Exhaust from the engine expands over the turbine wheel and rotates the turbine wheel. The turbine wheel in turn rotates the compressor impeller via the shaft. The compressor impeller receives cool air from the ambient surroundings and forces compressed air into combustion chambers of the engine. 
     Natural inherent material limitations, wear and tear of the compressor or turbine stage components, excessive speeds, or debris in the exhaust air or the intake air may cause the turbine wheel or the compressor impeller to fail. To prevent ejection of debris or oil in the event of a turbine wheel or compressor impeller failure, turbochargers typically rely on massive housings surrounding the wheels to absorb the tremendous amount of energy released during the failure. The massive housings, however, tend to increase the volume, weight and cost of the turbocharger. 
     U.S. Publication No. 2021/0156304 that published May 27, 2021 (“the &#39;304 publication”) discloses various systems and methods for a shroud of a turbomachine. In one example, a turbomachine includes a case and a rotor rotatably coupled to the case and configured to transfer energy between the rotor and a working fluid. The case includes a shroud housing the rotor, the shroud including an inner shell, an outer shell, and a lattice structure positioned between the inner shell and the outer shell. When beneficial, a better shroud for containment of an impeller during a failure condition is desired. 
     SUMMARY OF THE DISCLOSURE 
     In one aspect of the present disclosure, a compressor housing is disclosed for a turbocharger that includes a rotatable compressor impeller having a bore therethrough. The compressor housing may comprise an outer volute, a cavity, an impeller cover, a compressor diffuser and an inner volute. The outer volute is configured to be disposed about the bore. The outer volute includes a back wall and a curved casing. The curved casing defines an airflow-passageway. The back wall extends radially inward from the curved casing. The back wall may include a receptacle and a first plurality of annular steps. The receptacle configured to receive an alignment pin that positions a compressor diffuser in the compressor housing. The cavity is at least partially defined by the back wall of the outer volute and the impeller cover. The cavity is configured to receive the compressor impeller. The impeller cover is configured to fragment during impact with the compressor impeller during a failure condition of the compressor impeller. The impeller cover is disposed between the inner volute and the cavity. The compressor diffuser is disposed between the back wall and the impeller cover. The compressor diffuser includes an annular body, a plurality of fins and the alignment pin, the fins disposed between the annular body and the impeller cover. The alignment pin is disposed in the receptacle of the back wall of the outer volute. The inner volute is disposed between the outer volute and the impeller cover. The inner volute includes a bridge and an inner ring. The bridge extends between a first end and a second end of the impeller cover. The bridge and the impeller cover define a chamber. The inner ring and the bridge and the impeller cover define a pocket-void disposed inside the chamber. 
     In another aspect of the present disclosure, a method of assembling a compressor housing is disclosed for a turbocharger that includes a rotatable compressor impeller including a bore therethrough. The method may comprise disposing the outer volute about the turbocharger shaft. The outer volute includes a back wall and a curved casing. The curved casing defines an airflow-passageway. The back wall extends radially inward from the curved casing. The back wall includes a receptacle and a first plurality of annular steps. The receptacle is configured to receive an alignment pin that positions a compressor diffuser in the compressor housing. The method may further comprise arranging the back wall of the outer volute and an impeller cover to at least partially form a cavity configured to receive the compressor impeller, wherein the impeller cover is disposed between an inner volute and the cavity, and the impeller cover is configured to fragment during impact with the compressor impeller during a failure condition of the compressor impeller. The method may further comprise disposing a compressor diffuser between the back wall and the impeller cover, the compressor diffuser including an annular body, a plurality of fins and the alignment pin, the fins disposed between the annular body and the impeller cover, the alignment pin disposed in the receptacle of the back wall of the outer volute. The method may further comprise disposing an inner volute between the outer volute and the impeller cover. The inner volute includes a bridge and an inner ring. The bridge extends between a first end and a second end of the impeller cover. The bridge and the impeller cover define a chamber. The inner ring and the bridge and the impeller cover define a pocket-void disposed inside the chamber. 
     In a further aspect of the present disclosure, a turbocharger is disclosed. The turbocharger may include a rotatable turbocharger shaft, a compressor impeller and a compressor housing. The compressor impeller is disposed in a cavity and is mounted via the stud coupled to the rotatable turbocharger shaft. The compressor impeller includes a nose end, a hub end and a plurality of blades disposed between the nose end and the hub end. Each blade has a rim. The compressor housing comprises an outer volute, a cavity, an impeller cover, a compressor diffuser and an inner volute. The outer volute is arranged about the stud. The outer volute includes a back wall and a curved casing. The curved casing defines an airflow-passageway. The back wall extends radially inward from the curved casing. The back wall is proximal to and spaced apart from the compressor impeller. The back wall includes a receptacle and a first plurality of annular steps. The receptacle is configured to receive an alignment pin that positions a compressor diffuser in the compressor housing. The cavity is at least partially defined by the back wall of the outer volute and by an impeller cover. The impeller cover is configured to fragment during impact with the compressor impeller during a failure condition of the compressor impeller. The impeller cover is disposed between the inner volute and the compressor impeller. The compressor diffuser is disposed between the back wall and the impeller cover. The compressor diffuser includes an annular body, a fin and the alignment pin. The fin extending from the annular body to the impeller cover. The alignment pin disposed in the receptacle of the back wall of the outer volute. The inner volute disposed between the outer volute and the impeller cover. The inner volute including a bridge and an inner ring. The bridge extending from a first end to a second end of the impeller cover. The bridge and the impeller cover defining a chamber. The inner ring and the bridge and the impeller cover defining a pocket-void disposed inside the chamber. 
     Additional aspects are defined by the claims of this patent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic illustration of an exemplary internal combustion engine and a turbocharger in accordance with the present disclosure; 
         FIG.  2    is perspective view of an exemplary configuration of the turbocharger of  FIG.  1   ; 
         FIG.  3    is a sectional view of an exemplary configuration of the turbocharger of  FIG.  2   ; 
         FIG.  4    is an enlarged view of a portion of  FIG.  3   ; 
         FIG.  5    is an enlarged view of a portion of  FIG.  4   ; and 
         FIG.  6    is an enlarged view of a portion of  FIG.  4   . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1   , an internal combustion engine  10  having an integrated turbocharger  12  in accordance with the present disclosure is illustrated schematically. The engine  10  may find applications in mobile machines (not shown) such as, but not limited to, vehicles, heavy mechanical equipment, large tractors, on-road vehicles, off-road vehicles, marine vessels and the like, and in stationary machines such as generator sets and pumps. The engine  10  may include a crankcase  14  that forms a plurality of compression cylinders  16 . While six compression cylinders  16  are shown in an inline arrangement for illustration purposes, fewer or more compression cylinders  16  arranged in inline or alternative configurations within the crankcase  14 , for example in a V-configuration, may be used. Each compression cylinder  16  may include a reciprocating piston (not shown) connected to a common engine output shaft  18 . In the engine  10 , the combustion of a fuel and air mixture in the compression cylinders  16  generates motive power that rotates the engine output shaft  18 , and a resultant mixture of exhaust gas is produced as is known in the art. 
     The engine  10  may include an air intake manifold  20  that is selectively in fluid communication with each compression cylinder  16  and provides compressed intake air to the compression cylinders  16 . Air may be provided to air intake manifold  20  by an air induction system  22  that draws air from the ambient atmosphere surrounding the engine  10  and the machine in which the engine  10  is implemented. The engine  10  may include a fuel tank (not shown) to store suitable fuel for combustion in the compression cylinders  16  of the engine  10 . In various embodiments, the engine  10  may be configured to combust gasoline, diesel fuel, natural gas (liquefied or compressed) or other combustible energy sources, and the fuel tank will be configured as appropriate to store the fuel and provide the fuel to the engine  10  as required and known in the art. Compressed air from the air intake manifold  20  along with the fuel from the fuel tank provided to the compression cylinders  16  forms a combustible mixture that ignites when compressed or in the presence of a spark. Combustion byproducts are evacuated from each compression cylinder  16  through exhaust valves (not shown) to an exhaust manifold  24  that collects the exhaust gas from each compression cylinder  16 , and at least a portion of the exhaust gases may be transmitted to an exhaust system  26  for after treatment prior to being released back into the atmosphere. In the engine  10 , the intake air in the air intake manifold  20  as well as the exhaust gas released to the exhaust manifold  24  are under pressure. 
     In the illustrated embodiment, the turbocharger  12  is integrated with the engine  10  to provide compressed air with greater pressure to the air intake manifold  20 . As schematically illustrated in  FIG.  1   , the turbocharger  12  may be fluidly connected to the exhaust manifold  24  and arranged to receive pressurized exhaust gas therefrom via a high pressure exhaust gas line  28 . A turbocharger housing  30  of the turbocharger  12  is configured so that the pressurized exhaust gas from the high pressure exhaust gas line  28  acts on a turbine wheel  32  mounted on a turbocharger shaft  34  within the turbocharger housing  30 . The turbocharger  12  may further include a compressor impeller  36  mounted via a stud  35  ( FIG.  3   ) that is coupled to the turbocharger shaft  34  for rotation with the turbocharger shaft  34  and the turbine wheel  32 . The pressurized exhaust gas from the high pressure exhaust gas line  28  is directed at the turbine wheel  32  to create exhaust torque on the turbocharger shaft  34 . When the exhaust gas temperature and pressure are sufficient, the exhaust torque causes the turbine wheel  32  to rotate the turbocharger shaft  34  and stud  35  and the compressor impeller  36 . The compressor stage  62  ( FIG.  3   ) of the turbocharger  12  ( FIG.  1   ) in which the compressor impeller  36  is disposed may receive air from the air induction system  22  via a low pressure air line  38 . The rotating compressor impeller  36  compresses the air from the air induction system  22  and outputs compressed air to the air intake manifold  20  via a high pressure air line  40  for addition to the air coming directly from the air induction system  22  and the fuel from the fuel tank (not shown). After powering the turbine wheel  32 , the spent exhaust gas is discharged to the exhaust system  26  via a low pressure exhaust gas return line  42 . 
     During some operating conditions of the engine  10 , it may be desirable to drive the turbine wheel  32  of the turbocharger  12  even though the temperature and pressure of the exhaust gas in the high pressure exhaust gas line  28  are insufficient to rotate the turbine wheel  32  or to rotate the turbine wheel  32  at a desired speed. For example, at low engine speeds such as when the engine  10  is idling, emissions of pollutants such as nitrous oxides (NOx) can increase and low exhaust temperatures can make exhaust after treatment systems in the exhaust system  26  ineffective. In one exemplary embodiment, to selectively provide direct drive to the turbocharger  12  by the engine  10  when the operating conditions dictate, the engine output shaft  18  may drive the turbocharger shaft  34  when the exhaust gas will not drive the turbine wheel  32 , and may be disengaged when the exhaust gas will create sufficient torque and rotate the turbine wheel  32  and the compressor impeller  36  at sufficient speeds so that direct drive by the engine  10  is unnecessary. 
     In an embodiment, a carrier shaft  52  may be operatively coupled to the turbine wheel  32  and may have a carrier drive gear  54  mounted thereon and rotatable therewith. An operative connection between the engine  10  may be provided by a turbocharger drive gear  56  connected to a gear train or transmission  58  that is driven by the engine output shaft  18 . The turbocharger drive gear  56  is operatively connected to the carrier drive gear  54  by one or more idler gears  60  so that the carrier shaft  52  will spin at a desired speed and direction relative to the engine output shaft  18 . In other embodiments that utilize the compressor housing  66  disclosed herein, other appropriate drive mechanisms and arrangements may be utilized to drive the turbine wheel  32  and compressor impeller  36 . 
       FIGS.  2 - 3    illustrate an exemplary embodiment of a turbocharger  12  that may be implemented with the engine  10  of  FIG.  1   . As shown in  FIG.  3   , turbocharger  12  may include a compressor stage  62  and a turbine stage  64  disposed in the turbocharger housing  30  ( FIGS.  2 - 3   ). The turbocharger housing  30  comprises a compressor housing  66  and a turbine housing  72 . The compressor stage  62  may embody a fixed geometry compressor impeller  36  ( FIG.  3   ) attached via the stud  35 , which is coupled to the turbocharger shaft  34 , and configured to compress air received from the air induction system  22  ( FIG.  1   ) to a predetermined pressure level before the air enters the engine  10  for combustion. Air may enter a compressor housing  66  ( FIG.  2   ) via a compressor inlet  68  and exit the compressor housing  66  via a compressor outlet  70  ( FIG.  2   ). As air moves through the compressor stage  62  ( FIG.  3   ), the compressor impeller  36  may increase the pressure of the air which may be directed into the engine  10  ( FIG.  1   ). 
     The turbine stage  64  ( FIG.  3   ) may include a turbine housing  72  and a turbine wheel  32  that may be operably connected to the turbocharger shaft  34  (which may comprise one or more shafts operably coupled). Exhaust gases exiting the engine  10  ( FIG.  1   ) may enter the turbine scroll  73  ( FIG.  3   ) via the turbine inlet  74  ( FIG.  3   ) and flow toward the turbine exhaust duct  76 . The exhaust gases exit the turbine housing  72  via the turbine exhaust duct  76 . As the hot exhaust gases move through the turbine housing  72  and expand against the blades  80  of the turbine wheel  32 , the turbine wheel  32  may rotate the compressor impeller  36  via the operable connection of the turbocharger shaft  34  and the stud  35 . The hot exhaust gases may also heat the turbine housing  72 , which in turn may heat the compressor housing  66  and other components of the turbocharger  12  attached to or located near the turbine housing  72 . 
     As best seen in  FIG.  3   , the compressor impeller  36  includes a nose end  82 , a hub end  84 , a bore  86  extending from the nose end  82  to the hub end  84 , and a plurality of blades  88  ( FIG.  4   ) disposed between the nose end  82  ( FIG.  3   ) and the hub end  84 . The bore  86  may be a centrally disposed bore that extends through the compressor impeller  36 . In an embodiment the stud  35  is disposed inside the bore  86 . Each blade  88  ( FIG.  4   ) has a rim  90 . The compressor impeller  36  may further include a balance ring  92  that projects outward from a back surface  94  of the compressor impeller  36  toward a back wall  96  of an outer volute  98  of the compressor housing  66 . The compressor impeller  36  may further include a bulge portion  100  that generally disposed between the balance ring  92  (and the annular groove  102  of the back wall  96  in which the balance ring  92  is disposed (discussed below)) and the hub end  84  ( FIG.  3   ). The bulge portion  100  ( FIG.  4   ) slopes inward from the balance ring  92 /annular groove  102  toward the hub end  84 . (The bulge portion  100  is also disposed radially inward of the annular groove  102 .) 
     The compressor housing  66  ( FIGS.  3 - 4   ) may include the outer volute  98 , a cavity  104 , an impeller cover  106 , a compressor diffuser  108 , an inner volute  110 , an insert  112  and a shaft seal  114 . 
     The outer volute  98  ( FIG.  3   ) is configured to be disposed about the stud  35 . The outer volute  98  ( FIG.  4   ) includes a back wall  96  and a curved casing  116 . The curved casing  116  includes a base end  118  ( FIG.  6   ) and a compressor outlet  70  ( FIG.  2   ). The base end  118  ( FIG.  6   ) is disposed adjacent to and radially outward of the compressor diffusor  108 . The curved casing  116  ( FIG.  4   ) defines an airflow-passageway  120  extending between the compressor diffusor  108  and the compressor outlet  70  ( FIG.  2   ). The curved casing  116  ( FIG.  4   ) of the outer volute  98  is configured to receive the (compressed) air that flows from the cavity  104  and through the compressor diffusor  108  to the airflow-passageway  120 . The outer volute  98  is configured to discharge such air via the compressor outlet  70  ( FIG.  2   ). The compressed air is generated by rotation of the compressor impeller  36  ( FIG.  4   ). As discussed earlier herein, such discharged compressed air flows from the compressor outlet  70  ( FIG.  2   ) into the high pressure air line  40  ( FIG.  1   ) and to the air intake manifold  20 . 
     The back wall  96  ( FIG.  4   ) of the outer volute  98  extends radially inward from the curved casing  116  toward the turbocharger shaft  34  ( FIG.  3   ). The back wall  96  ( FIG.  4   ) includes a front surface  122  disposed proximal to the compressor impeller  36 , and directly adjacent to the cavity  104  and the compressor diffuser  108 . The back wall  96  is generally annular in shape and the front surface  122  includes a first receptacle  124   a,  a second receptacle  124   b  ( FIG.  3   ), a first plurality of annular steps  126   a  ( FIG.  5   ), a second plurality of annular steps  126   b  and an annular groove  102 . The base end  118  ( FIG.  6   ) and the front surface  122  of the back wall  96  define a recess  128  having a sidewall  130  and a floor  132 . As shown in the embodiment of  FIG.  6   , an annular body  134  of the compressor diffuser  108  is disposed in the recess  128  to extend along the floor  132 . 
     Each of the first receptacle  124   a  ( FIG.  3   ) and the second receptacle  124   b  are configured to receive an alignment pin  136  ( FIG.  5   ) and may be disposed radially outward of the first plurality of annular steps  126   a,  the second plurality of annular steps  126   b  and the annular groove  102 . As best seen in  FIG.  3   . the second receptacle  124   b  may be disposed in the generally annular back wall  96  opposite to the first receptacle  124   a.  The first plurality of annular steps  126   a  ( FIG.  5   ) may be radially nested (e.g., a first annular step of the first plurality disposed inside of a second annular step of the first plurality so that the second annular step of the first plurality is disposed radially outward of the first annular step of the first plurality). Similarly, the second plurality of annular steps  126   b  may be radially nested (e.g., a first annular step of the second plurality disposed inside of a second annular step of the second plurality so that the second annular step of the second plurality is disposed radially outward of the first annular step of the second plurality). The first plurality of annular steps  126   a  are disposed radially outward of the second plurality of annular steps  126   b.  The first plurality of annular steps  126   a  may be disposed radially outward of the balance ring  92  and the second plurality of annular steps  126   b  may be disposed radially inward of the balance ring  92 . The annular groove  102  is disposed between the first plurality of annular steps  126   a  and the second plurality of annular steps  126   b.  The annular groove  102  is configured to receive the balance ring  92 . As the balance ring  92  rotates with the rotation of the compressor impeller  36 , the annular groove  102  is spaced apart from the balance ring  92 . In the embodiment shown in  FIG.  5   , the annular groove  102  has a reciprocal shape to the shape of the balance ring  92 . 
     The cavity  104  may be at least partially defined by the back wall  96  of the outer volute  98  ( FIG.  4   ) and the impeller cover  106 . The cavity  104  is configured to receive the compressor impeller  36 . 
     The impeller cover  106  is sacrificial in nature and is configured to fragment during impact with the compressor impeller  36  during a failure condition of the compressor impeller  36  such as burst impeller (discussed later herein). A failure condition is one in which the compressor impeller  36  or portions thereof fracture and move in an uncontrolled manner in the cavity  104 . The impeller cover  106  is disposed between the inner volute  110  ( FIG.  4   ) and the cavity  104  (and the compressor impeller  36  within the cavity  104 ). In an embodiment, the impeller cover  106  may be made of a frangible material, such as a frangible metal or the like, to facilitate fracturing or shattering on impact. The impeller cover  106  includes a convex portion  138 . The convex portion  138  is convex with respect to the cavity  104 . 
     The compressor diffuser  108  is generally annular in shape and is disposed between the back wall  96  of the outer volute  98  and the impeller cover  106 . The compressor diffuser  108  includes an annular body  134 , a plurality of fins  146  and a first alignment pin  136   a  and a second alignment pin  136   b  ( FIG.  3   ). 
     The annular body  134  ( FIG.  6   ) includes a back side  148  adjacent to the front surface  122  of the back wall  96 , a front side  150 , an inner side  152  and an outer side  154 . The outer side  154  is adjacent to the base end  118  of the curved casing  116  and is radially outward of the inner side  152 . A base gap  156  may be disposed between the base end  118  and the outer side  154 . One or more side gaps  158  may be disposed between the back side  148  of the annular body  134  and the front surface  122  of the back wall  96 . As shown in  FIG.  6   , in an embodiment, one or more side gaps  158  may be generally slit-like in shape. 
     In the embodiment shown in  FIG.  5   , there is shown a fin  146 . Each fin  146  is disposed between the annular body  134  and the impeller cover  106 . For example, in the embodiment of  FIGS.  3   , the fin  146  extends from the front side  150  of the annular body  134  to the impeller cover  106 . The first alignment pin  136   a  is disposed in disposed in the first receptacle  124   a  and the second alignment pin  136   b  ( FIG.  3   ) is disposed in the second receptacle  124   b  of the front surface  122  of the back wall  96  of the outer volute  98 . The first and second alignment pins  136  (a,b) facilitate positioning of the compressor diffuser  108  in the compressor housing  66 . The compressor diffuser  108  ( FIG.  5   ) may also include one or more cut-outs  160  in the back side  148  of the annular body  134 . Each cut-out  160  configured to receive one of the (first or second) alignment pins  136  (a,b). 
     The compressor housing  66  further includes a blade gap  162  disposed directly between the (outer) rim  90  of each blade  88  and the inner side  152  of the annular body  134 . The rim  90  is radially aligned with an inner corner  164  of the inner side  152  of the annular body  134 . The outer corner  166  of the inner side  152  is radially aligned with the first plurality of annular steps  126   a  and is free of radial alignment with the rim  90  of each blade  88 . 
     The inner volute  110  ( FIG.  4   ) is disposed between the outer volute  98  and the impeller cover  106 . The inner volute  110  is coupled to the outer volute  98  and includes a bridge  144  and an inner ring  168 . The bridge  144  extends between a first end  170  and a second end  172  of the impeller cover  106 . The bridge  144  and the impeller cover  106  define a chamber  142 . The inner ring  168  together with a portion of the bridge  144  (between the inner ring  168  and the impeller cover  106 ) may be generally C-shaped. The inner ring  168  and the bridge  144  and the impeller cover  106  define a pocket-void  174  that is disposed inside the chamber  142 . The pocket-void  174  may be hollow. The inner volute  110  is configured to resist movement of a (failed) compressor impeller  36  into the airflow-passageway  120  of the outer volute  98  in the event of a compressor impeller  36  failure such as burst impeller. 
     The insert  112  is disposed adjacent to the impeller cover  106  and is suspended in the cavity  104 . The insert  112  is disposed radially outward from the nose end  82  of the compressor impeller  36 . The insert  112  is configured to provide a radial stop to a fractured compressor impeller  36  during a burst impeller or similar failure condition. 
     The inner volute  110 , the outer volute  98 , the compressor diffuser  108  and the insert  112  may be made from resilient materials (e.g., resilient metal(s)) that are stronger and more ductile than the material of the sacrificial impeller cover  106  (e.g., frangible metal) to facilitate the containment of the compressor impeller  36  and the fragments of the shattered impeller cover  106  during a failure condition such as burst impeller. 
     The shaft seal  114  is disposed radially inward of the back wall  96 . The shaft seal  114  disposed radially outward of the hub end  84  of the compressor impeller  36 . The shaft seal  114  is configured to control oil and air flow. 
     Also disclosed is a method of assembling a compressor housing  66  for a turbocharger  12  that includes a rotatable compressor impeller  36  that includes a bore  86  therethrough. The method including disposing the outer volute  98  about the bore  86 , the outer volute  98  including a back wall  96  and a curved casing  116 . The curved casing  116  defines an airflow-passageway  120 . The back wall  96  extends radially inward from the curved casing  116 . The back wall  96  includes a first receptacle  124   a  and a first plurality of annular steps  126   a.  The first receptacle  124   a  is configured to receive a first alignment pin  136   a  (that positions a compressor diffuser  108  in the compressor housing  66 ). The method may further comprise arranging the back wall  96  of the outer volute  98  and an impeller cover  106  to at least partially form a cavity  104  that is configured to receive the compressor impeller  36 , wherein the impeller cover  106  is disposed between an inner volute  110  and the cavity  104 . The impeller cover  106  is configured to fragment during impact with the compressor impeller  36  during a failure condition of the compressor impeller  36 . The method may further comprise disposing the compressor diffuser  108  between the back wall  96  and the impeller cover  106 . The compressor diffuser  108  includes an annular body  134 , a plurality of fins  146  and the first alignment pin  136   a.  The fins  146  may be disposed between the annular body  134  and the impeller cover  106 . The first alignment pin  136   a  is disposed in the first receptacle  124   a  of the back wall  96  of the outer volute  98 . The method may further comprise disposing an inner volute  110  between the outer volute  98  and the impeller cover  106 . The inner volute  110  includes a bridge  144  and an inner ring  168 . The bridge  144  extends between a first end  170  and a second end  172  of the impeller cover  106 . The bridge  144  and the impeller cover  106  define a chamber  142 . The inner ring  168  and the bridge  144  and the impeller cover  106  define a pocket-void  174  disposed inside the chamber  142 . 
     INDUSTRIAL APPLICABILITY 
     Turbochargers  12  undergo various stresses over their life span due to aerodynamic, thermal and mechanical loads. Compressor impellors  36  may experience swings in temperature from compressor inlet variation  68  and the act of compressing the intake air. Mechanical loading from compressing the air combined with centrifugal loads during rotating can fatigue a compressor impeller  36  over time. Occasionally the compressor impeller  36  may fracture or break apart. The failure condition associated with such compressor impeller  36  failure may be referred to as a “burst impeller”. Burst impeller may occur during normal operating speeds or may occur when a turbocharger  12  is operating past nominal maximum speed and temperature. When a burst impeller occurs in the latter scenario, far more energy may need to be contained and dissipated than when the burst impeller is related to fatigue failure at normal operating speeds. The disclosed compressor housing  66  provides energy dissipation and containment of material (e.g., broken compressor impeller  36  fragments, surrounding housing pieces, or the like) and oil in the compressor housing  66  during failure conditions such as burst impeller. 
     Compressor impellers  36  typically utilize an optimized back shape to limit bore  86  stress. However, stress optimization can add mass to the impeller shape (e.g., near the bore  86  and near the hub end  84 ), which can add to the energy that is released during a failure condition. To address the heavier section of the compressor impeller  36  near the bore  86 , the shaft seal  114  remains clear of the compressor impeller  36  radially and a plurality of annular steps  126  integral to the outer volute  98  surround both the bulge portion  100  and the balance ring  92  of the compressor impeller  36 . During the burst impeller failure condition, the blades  88  of the compressor impeller  36  typically first hit the impeller cover  106  thereby forcing a rotation of the compressor impeller  36  about the nose end  82 . In the disclosed compressor housing  66 , the impeller cover  106  is configured to accept and dissipate the energy from the impact of the blades  88  by shattering or fragmenting. 
     The annular steps  126  attenuate this rotation and force the rims  90  (of the blades  88  of the compressor impeller  36 ) into contact with the front side  150  and inner corner  164  of the annular body  134  compressor diffuser  108 . The force of the impact of the rims  90  into the compressor diffuser  108  moves the compressor diffuser  108  in a radially outward direction. The alignment pins  136 , which are provided in the turbocharger  12  to locate the compressor diffuser  108  and to facilitate the base gap  156  and the side gaps  158 , provide some resistance prior to shearing off. Once the alignment pins  136  are sheared off, the compressor diffuser  108  moves radially outward toward the base end  118  of the curved casing  116 . The base gap  156  together with the side gaps  158  reduce interference from the back wall  96  of the outer volute  98 , which reduces cracking and damage from upward thrust of the annular bodyl 34 . The impeller cover  106  accepts and dissipates impeller energy from the blades  88  when it fragments or shatters apart. 
     The insert  112  attenuates movement of the nose end  82  of the compressor impeller  36  upon contact as fragments of the compressor impeller  36  progress outward. The inner volute  110  and its inner ring  168  are axially flexible to minimize longitudinal momentum and radially reinforce the structure of the compressor housing  66 . The inner volute  110  is configured to slow down outward movement of the outer sections of the compressor impeller  36  (and the fragments of the impeller cover  106 ) so that the compressor impeller  36  and impeller cover  106  (and oil) are contained inside the outer volute  98 , which acts as a final line of defense against puncture and wraps from the front of the inner volute  110  to fully around the compressor impeller  36  to attenuate the axial energy released in opposition to the force from the compressor impeller  36  striking the impeller cover  106 . The combination of (a) the impeller cover  106  dissipating the energy from the failed/burst compressor impeller  36 , and (b) the inner volute  110  and the outer volute  98  being made of a resilient material that is stronger than the frangible material of the impeller cover  106  prevents the fragments of the broken compressor impeller  36  from breaking through to outside of the turbocharger  12 . 
     While the preceding text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the scope of protection. 
     It should also be understood that, unless a term was expressly defined herein, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning.