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 vanes formed as ring segments and disposed about the air inlet and each movable circumferentially and radially inwardly through a slot in the air inlet wall 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.
1. A turbocharger, comprising:
a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing receiving exhaust gas and supplying the exhaust gas to the turbine wheel;
a centrifugal compressor assembly comprising a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith, the compressor wheel having vanes and defining an inducer portion, the compressor housing having an air inlet wall defining an air inlet for leading air generally axially into the compressor wheel, the compressor housing further defining a volute for receiving compressed air discharged generally radially outwardly from the compressor wheel; and
a compressor inlet-adjustment mechanism disposed in the air inlet of the compressor housing and movable between an open position and a closed position, the inlet-adjustment mechanism comprising a plurality of vanes disposed about the air inlet and a unison ring that is rotatable about a rotational axis of the turbocharger, each vane comprising a segment of a full 360° ring, each of the vanes including a pair of circumferentially spaced first pins projecting from a first face of the vane toward the unison ring, the unison ring including a plurality of pairs of first guide slots, one pair of said first guide slots for each vane, wherein the first pins of each vane are engaged in a corresponding pair of said first guide slots in the unison ring, wherein each of the first guide slots follows a path that proceeds radially outward along a first circumferential direction;
wherein each vane further includes a pair of circumferentially spaced second pins projecting from a second face of the vane, the inlet-adjustment mechanism further comprising a stationary member adjacent the second face of the vanes and defining a plurality of pairs of second guide slots therein, one pair of said second guide slots for each vane, wherein the second pins of each vane are engaged in a corresponding pair of said second guide slots, wherein each of the second guide slots follows a path that proceeds radially inward along said first circumferential direction, and wherein the first and second guide slots cross one another at intersection points that lie on a circle whose radius from the rotational axis of the compressor varies with rotational position of the unison ring;
rotation of the unison ring in the first circumferential direction causing each vane to move along the second guide slots and therefore move radially inwardly as the vane moves in said first circumferential direction, and rotation of the unison ring in an opposite second circumferential direction causing each vane to move along the second guide slots and therefore move radially outwardly as the vane moves in said second circumferential direction.
2. The turbocharger of claim 1 , wherein each vane includes a radially inner edge having a circular-arc shape, the vanes being configured so that said radially inner edges collectively form the orifice as substantially circular in the closed position of the inlet-adjustment mechanism.
3. The turbocharger of claim 1 , wherein the inlet-adjustment mechanism further comprises a cartridge including first and second annular end plates that are stationary and are axially spaced apart, and the vanes are disposed between said end plates, wherein the cartridge is disposed in an annular space defined by the compressor housing, and wherein the stationary member having the second guide slots comprises the second end plate.