Centrifugal compressor diffuser passage boundary layer control

Abstract

A centrifugal compressor diffuser ( 42 ) includes a plurality of diffuser flow passages ( 22 ) extending through an annular diffuser housing ( 20 ) and circumferentially bounded by diffuser vanes ( 23 ) and axially bounded by forward and aft walls ( 101, 100 ). A diffuser boundary layer bleed ( 96 ) for the passages may include boundary layer bleed apertures ( 106 ) or slots ( 130 ) disposed through the forward wall ( 101 ) and a downstream facing wall ( 142 ) canted at an acute cant angle to a downstream diffuser airflow direction ( 103 ) in the passages. Diffuser bleed flow ( 112 ) is bled from a diffuser boundary layer. Boundary layer bleed apertures can be located downstream of throat sections ( 28 ) of the flow passages near pressure sides of the vanes. A centrifugal compressor ( 18 ) may include the diffuser surrounding an annular centrifugal compressor impeller ( 32 ) and apparatus for flowing impeller bleed flow ( 102 ) from a radial clearance between an impeller tip ( 36 ) and a diffuser annular inlet ( 27 ) with diffuser bleed flow either mixed or separately to cool a turbine ( 16 ).

What is claimed: 
     
         1 . A gas turbine engine centrifugal compressor diffuser comprising:
 an annular diffuser housing,   diffuser vanes axially extending between a forward wall and an aft wall of he diffuser housing,   a plurality of diffuser flow passages extending through the housing and spaced about a circumference of the housing,   the diffuser flow passages bounded by the diffuser vanes and the forward and aft walls, and   a diffuser boundary layer bleed for bleeding diffuser bleed flow from a diffuser boundary layer in each of the diffuser flow passages.   
     
     
         2 . The diffuser according to  claim 1  further comprising the diffuser boundary layer bleed configured for bleeding the diffuser bleed flow from the diffuser boundary layer at a position located in a region of flow weakness in each of the diffuser flow passages. 
     
     
         3 . The diffuser according to  claim 1  further comprising the diffuser boundary layer bleed including boundary layer bleed apertures disposed through the forward wall. 
     
     
         4 . The diffuser according to  claim 3  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         5 . The diffuser according to  claim 3  further comprising the boundary layer bleed apertures positioned or located downstream of throat sections of the diffuser flow passages near pressure sides of the diffuser vanes. 
     
     
         6 . The diffuser according to  claim 5  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         7 . A gas turbine engine centrifugal compressor comprising:
 an annular centrifugal compressor impeller,   a diffuser annularly surrounding the impeller,   a plurality of diffuser flow passages extending through a housing of the diffuser and spaced about a circumference of the housing,   each of the passages including a throat section and a diffusing section downstream of the throat section,   the diffuser flow passages circumferentially bounded by diffuser vanes extending axially between forward and aft walls of the diffuser, and   a diffuser boundary layer bleed for bleeding diffuser bleed flow from a diffuser boundary layer in each of the diffuser flow passages.   
     
     
         8 . The centrifugal compressor according to  claim 7  further comprising the diffuser boundary layer bleed configured for bleeding the diffuser bleed flow from the diffuser boundary layer at a position located in a region of flow weakness in each of the diffuser flow passages. 
     
     
         9 . The diffuser according to  claim 7  further comprising the diffuser boundary layer bleed including boundary layer bleed apertures disposed through the forward wall. 
     
     
         10 . The centrifugal compressor according to  claim 9  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         11 . The centrifugal compressor according to  claim 10  further comprising the boundary layer bleed apertures positioned or located downstream of throat sections of the diffuser flow passages near pressure sides of the diffuser vanes. 
     
     
         12 . The centrifugal compressor according to  claim 11  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         13 . The centrifugal compressor according to  claim 9  further comprising:
 a radial clearance between an impeller tip of the impeller and an annular inlet of the diffuser, 
 a means for mixing impeller bleed flow from the radial clearance with the diffuser bleed flow from the boundary layer bleed apertures for providing turbine cooling air and flowing the turbine cooling air to a turbine, or 
 a means for flowing the impeller bleed flow and the diffuser bleed flow separately to the turbine. 
 
     
     
         14 . The centrifugal compressor according to  claim 13  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         15 . The centrifugal compressor according to  claim 13  further comprising the boundary layer bleed apertures positioned or located downstream of throat sections of the diffuser flow passages near pressure sides of the diffuser vanes. 
     
     
         16 . The centrifugal compressor according to  claim 15  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         17 . The centrifugal compressor according to  claim 9  further comprising:
 a radial clearance between an impeller tip of the impeller and an annular inlet of the diffuser, 
 the radial clearance in fluid communication with a radially inner manifold, 
 the boundary layer bleed apertures in flow communication with a radially outer manifold, 
 the radially inner manifold in fluid communication with the radially outer manifold such that the impeller bleed flow flows into the radially outer manifold and mixes with the diffuser bleed flow to form turbine cooling air, and 
 means for flowing turbine cooling air out of the radially outer manifold. 
 
     
     
         18 . The centrifugal compressor according to  claim 17  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         19 . The centrifugal compressor according to  claim 18  further comprising the boundary layer bleed apertures positioned or located downstream of throat sections of the diffuser flow passages near pressure sides of the diffuser vanes. 
     
     
         20 . The centrifugal compressor according to  claim 19  further comprising each of the boundary layer bleed apertures being a slat including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         21 . The centrifugal compressor according to  claim 9  further comprising:
 a radial clearance between an impeller tip of the impeller and an annular inlet of the diffuser, 
 the radial clearance in fluid communication with a radially inner annular manifold, 
 inter-manifold apertures disposed between the inner annular manifold and a plurality of radially outer annular manifolds, 
 a means for porting and flowing the impeller bleed flow from the radial clearance through a plurality of circumferentially distributed impeller bleed flow manifold ports in and through an diffuser forward casing surrounding the centrifugal compressor to the high pressure turbine for turbine cooling, 
 the diffuser boundary layer bleed in fluid flow communication with and operable for bleeding the diffuser bleed flow into an annular diffuser bleed manifold, and 
 a means for porting and flowing the diffuser bleed flow through a plurality of circumferentially distributed diffuser bleed manifold ports in and through the diffuser forward casing to the high pressure turbine for turbine cooling. 
 
     
     
         22 . The centrifugal compressor according to  claim 21  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively. 
     
     
         23 . The centrifugal compressor according to  claim 22  further comprising the boundary layer bleed apertures positioned or located downstream of throat sections of the diffuser flow passages near pressure sides of the diffuser vanes. 
     
     
         24 . The centrifugal compressor according to  claim 23  further comprising each of the boundary layer bleed apertures being a slot including a downstream facing wall angled or canted at an acute cant angle with respect to a downstream diffuser airflow direction in each of the diffuser flow passages respectively.