Turbomachine

Abstract

A turbomachine such as a turbocharger comprises a housing 3 defining a bearing cavity and a turbine wheel 4 mounted to a shaft 8 for rotation about an axis. A housing wall 3 a is disposed between the bearing cavity and the turbine wheel 4 , the shaft 8 extending into the bearing cavity through a shaft passage 20 provided in the housing wall 3 a . The housing wall 3 a comprises a first portion defining an air gap with the turbine wheel 4 and a second annular portion 3 b defining the opening to the shaft passage 20 and which is axially spaced from said turbine wheel 4 by a minimum distance D. The housing wall 3 a further comprises at least one third portion 32 , such as an annular rib, radially spaced from the first portion 3 a . The third portion is configured to bear load from a turbine wheel rotating off axis in a failure condition.

1 . A turbomachine comprising:
 a housing defining a bearing cavity;   a turbine wheel mounted to a shaft for rotation about an axis;   a housing wall disposed between the bearing cavity and the turbine wheel;   the shaft extending into the bearing cavity through a shaft passage provided in said housing wall; the housing wall including:   a first portion defining an air gap between the housing wall and the turbine wheel;   a second portion which is annular and protrudes from the first portion into said air gap to define the opening to said passage; and   at least one third portion which is radially distanced from second portion and which protrudes from said first portion into said air gap;   wherein the third portion is configured to support the turbine wheel in a failure condition in which the wheel rotates off-axis to thereby at least reduce the radial load which would otherwise be applied to the annular second portion by the shaft.   
   
   
       2 . A turbomachine according to  claim 1 , wherein the second portion is defined by a generally domed portion of the housing wall. 
   
   
       3 . A turbomachine according to  claim 2 , wherein the or each third portion is defined by a feature of the housing wall which extends to the domed portion to directly reinforce the domed portion against any radial load applied thereto by the shaft. 
   
   
       4 . A turbomachine according to  claim 1 , wherein the or each third portion is positioned at a radius less than or equal to the radius of the turbine wheel. 
   
   
       5 . A turbomachine according to  claim 1 , wherein the second portion is spaced from the turbine wheel by a minimum distance D and the or each third portion is spaced from the turbine wheel by minimum distance d, wherein d is less than or equal to D. 
   
   
       6 . A turbomachine according to  claim 1 , wherein the or each third portion is at least substantially annular and at least substantially surrounds the second portion. 
   
   
       7 . A turbomachine according to  claim 1 ,
 wherein the or each third   portion of the housing wall comprises a rib or other protrusion which has a height extending from the housing wall towards the turbine wheel.   
   
   
       8 . A turbomachine according to  claim 1 , wherein the or each third portion of the housing wall comprises a rib or other protrusion which has a height extending from the housing wall towards the turbine wheel, and the or each third portion has a length extending in a linear or curved direction away from the second portion. 
   
   
       9 . A turbomachine according to  claim 8 , wherein at least one third portion extends in a generally radial or tangential direction away from said second portion. 
   
   
       10 . A turbomachine according to  claim 1 , comprising a plurality of said third portions. 
   
   
       11 . A turbomachine according to  claim 1 , wherein the turbine wheel comprises a central body which supports turbine blades, and wherein said central body defines a back face, the minimum distance d being defined between the or each third portion of the bearing housing and the turbine wheel back face. 
   
   
       12 . A turbomachine according to  claim 1 , wherein the or each third portion of the housing wall defines a turbine wheel contact surface which lies in a plane substantially normal to the axis or which lies on a conical surface defined about the axis. 
   
   
       13 . A turbomachine according to  claim 1 , wherein said housing wall defines a portion of the bearing cavity and wherein said shaft is sealed with respect to said passage to prevent or obstruct leakage of oil through said passage to said turbine wheel. 
   
   
       14 . A turbomachine according to  claim 1 , wherein said housing wall is defined by, or connected to, a housing comprising a further wall portion which extends in a direction having a significant component parallel to said axis. 
   
   
       15 . A turbomachine according to  claim 14 , wherein said further wall portion meets said housing wall at a radial location corresponding to the radial location of the or each third portion of the housing wall such that an axial force applied to the or each third portion of the housing wall is reacted by said further housing wall portion. 
   
   
       16 . A turbomachine according to  claim 1 , wherein the turbomachine is a turbocharger or a power turbine. 
   
   
       17 . A turbomachine according to  claim 2 , wherein the or each third portion is positioned at a radius less than or equal to the radius of the turbine wheel. 
   
   
       18 . A turbomachine according to  claim 3 , wherein the or each third portion is positioned at a radius less than or equal to the radius of the turbine wheel. 
   
   
       19 . A turbomachine according to  claim 2 , wherein the second portion is spaced from the turbine wheel by a minimum distance D and the or each third portion is spaced from the turbine wheel by minimum distance d, wherein d is less than or equal to D. 
   
   
       20 . A turbomachine according to  claim 1 , wherein the second portion is spaced from the turbine wheel by a minimum distance D and the or each third portion is spaced from the turbine wheel by minimum distance d, wherein d is less than or equal to D.