Compressor recirculation into annular volume
To solve the problems of compressor wheel blade flow separation causing surge type noises when a compressor return or recirculation valve is opened or closed, recirculation airflow from a compressor recirculation valve is fed into an annular volume, defined between inner and outer walls or shaped as a radially expanded, axially flattened cylindrical space in the compressor inlet, so that the generally unidirectional radial flow from the compressor recirculation valve is re-directed and organized as it is turned from generally radial to generally axial, merging with the general inlet flow and presenting the compressor wheel with airflow of“circumferentially uniform” flow velocity.
1. A compressor for compressing gas, said compressor comprising:
a compressor housing including a compressor inlet ( 14 ) and a compressor discharge ( 15 ), said compressor inlet ( 14 ) being defined by a channel wall ( 22 ) having a first circumference and having a center,
a compressor wheel ( 20 ) mounted for rotation within said compressor housing between said compressor inlet ( 14 ) and compressor discharge ( 15 ),
a compressor recirculation duct ( 16 ) providing fluid communication between the compressor discharge ( 15 ) and the compressor inlet ( 14 ),
a compressor recirculation valve ( 80 ) for control of air flow in said compressor return recirculation duct,
an annular transition cavity formed by a radially expanded cross-sectional area of the channel wall ( 22 ) arranged about the entire circumference of the compressor inlet ( 14 ) for introducing air from the compressor recirculation duct ( 16 ) into the compressor inlet ( 14 ) about the entire circumference of the compressor inlet ( 14 ),
wherein rotation of said compressor wheel causes air to be taken in at the compressor inlet ( 14 ) at a first pressure and discharged at the compressor discharge ( 15 ) at a pressure higher than said first pressure,
wherein opening the compressor recirculation valve ( 80 ) allows air from the compressor discharge to pass through the compressor recirculation duct ( 16 ), and
wherein said annular transition cavity formed by said radially expanded cross-sectional area of the channel wall ( 22 ) causes said air introduced from the compressor recirculation duct ( 16 ) into the compressor inlet ( 14 ) to be distributed about the circumference of the compressor inlet.
2. The compressor as in claim 1 , wherein said radially expanded cross-sectional area of the channel wall ( 22 ) is co-axial with said compressor inlet ( 14 ) channel wall ( 22 ) having said first circumference.
3. The compressor as in claim 1 , wherein said annular transition cavity formed by a radially expanded cross-sectional area of the channel wall ( 22 ) is formed by a radially expanded channel wall ( 22 ) having a center that is not co-axial with said compressor inlet ( 14 ).