A method for operating start-up of a compressor train is disclosed. The train includes a driver machine and at least a centrifugal compressor drivingly coupled to the driver machine. The centrifugal compressor in turn includes a plurality of compressor stages and at least a first set of variable inlet guide vanes at an inlet of one of the compressor stages. The method includes at least partly closing the first set of variable inlet guide vanes; when the first set of variable inlet guide vanes is at least partly closed, starting rotation of the centrifugal compressor and accelerating the centrifugal compressor up to a minimum operating speed; opening the at least one set of variable inlet guide vanes to increase the gas flow through the centrifugal compressor once the minimum operating speed has been achieved.

An apparatus for diagnosing and controlling the aerodynamic stability of a compressor and method there of are provided. The apparatus includes a measurement device (100), a signal processing device (200) and a control and execution device (300), wherein the measurement device (100) is configured to measure the pressure or velocity fluctuations of air flows in different positions inside a compressor in real time, and to transmit real-time measurement signals obtained from different positions to the signal processing device (200); the signal processing device (200) is configured to determine, according to the real-time measurement signals, a type and spatial distribution of instability precursor in the compressor, and to output corresponding control strategy signals to the control and execution device (300); and the control and execution device (300) executes, according to the received control strategy signals, corresponding control actions to regulate the stability of the compressor (S3).

A control method for a centrifugal compressor and an air conditioning system. The control method for the centrifugal compressor includes: S100, when an inlet opening of the centrifugal compressor is below a first preset value, shutting down a drive motor of the centrifugal compressor; or S200, when the inlet opening of the centrifugal compressor is not below the first preset value, performing the following operations in a preset order: decreasing the inlet opening of the centrifugal compressor, and increasing a rotate speed of the centrifugal compressor.

A heating, ventilation, and/or air conditioning (HVAC) system includes a compressor having an impeller configured to rotate and drive a working fluid through a working fluid circuit of the HVAC system in an active operating mode. The HVAC system further includes a controller configured to, in response to receiving an input indicative of a transition to operate in an inactive operating mode, suspend the active operating mode by interrupting a supply of power to the compressor, adjust pre-rotation vanes of the compressor, a variable geometry diffuser of the compressor to a first position, or both to enable a backflow of the working fluid through the compressor for a first interval of time, and, after the first interval of time has elapsed, adjust the pre-rotation vanes, the variable geometry diffuser, or both to a second position to block the backflow of the working fluid through the compressor.

A centrifugal compressor includes: an impeller provided in a housing; a throttling portion provided in front of the impeller in the housing; an actuator rod connected to an actuator and including a plate portion including a plane at its end; and a connecting portion connected to the throttling portion and including a pair of projections facing each other across the plate portion in an axial direction of the actuator rod.

A centrifugal compressor includes: a scroll housing including a scroll flow path; a shroud piece attached to the scroll housing at a position radially inside the scroll flow path and including a shroud portion that faces a compressor impeller in a radial direction; and a throttling portion arranged in a gap formed between the scroll housing and the shroud piece.

An illustrative example embodiment of a compressor includes an inlet defining an intake passage, a plurality of inlet guide vanes, an impeller, and a plurality of swirl nozzles. Fluid flow through the plurality of inlet guide vanes into the intake passage is selectively adjustable to control fluid flow through at least the portion of the intake passage downstream of the swirl nozzles. The impeller includes a plurality of blades and directs fluid from the intake passage toward an outlet. The swirl nozzles have outlets positioned downstream of the plurality of inlet guide vanes and upstream of the impeller. The swirl nozzles are configured to introduce fluid into the intake passage to cause swirl of fluid in the intake passage between the plurality of inlet guide vanes and the impeller.

A method of operating a heat exchanger system in which a compressor, which is drivable by a motor, is fluidly interposed between an evaporator and a condenser following receipt of a shutdown command is provided. The method includes positioning inlet guide vanes (IGVs) of the compressor in a first position in the event of at least one of a first precondition being in effect and the first and a second precondition both not being in effect. The method further includes positioning the IGVs in a second position in an event the first precondition is not in effect but the second precondition is in effect, ramping a speed of the compressor down until a third precondition takes effect, removing power from the motor and positioning the IGVs in the first position once power is removed from the motor.

A centrifugal compressor and a method of operating a centrifugal compressor. The centrifugal compressor includes: an impeller configured to suction a gas to be compressed; a diffuser disposed downstream of the impeller to pressurize the gas, the diffuser comprising a movable ring, a main passage in which the gas flows past the ring, and an openable branch passage; and a circulation loop comprising an inlet and an outlet, the outlet being in communication with an inlet of the impeller; the branch passage is disposed to be in communication with the main passage and the circulation loop when the ring moves into the main passage so that a portion of the gas in the main passage passes through the circulation loop and returns to the impeller so as to be suctioned, and to be closed when the ring is withdrawn from the main passage.

A casing treatment for a compressor includes one or more cavities in a casing disposed radially outwardly of tips of the compressor rotor blades. A liner is moveable relative to the casing between a first position and a second position. The liner is shaped to add a volume to the tip clearance gap when moving from the second position toward the first position. The liner is displaceable between the first and second positions in coordination with at least the rotation of inlet guide vanes (IGVs) between IGV positions.