US Patent 10465706 Adjustable-trim centrifugal compressor for a turbocharger

A centrifugal compressor for a turbocharger includes an inlet-adjustment mechanism in an air inlet for the compressor, operable to move between an open position and a closed position in the air inlet. The inlet-adjustment mechanism includes a plurality of blades disposed about the air inlet and each pivotable about one end of the blade, the blades extending through a slot in the air inlet wall when the blades are in the closed position so as to form an orifice of reduced diameter relative to a nominal diameter of the inlet. Movement of the inlet-adjustment mechanism from the open position to the closed position is effective to shift the compressor's surge line to lower flow rates.