A centrifugal compressor for a chiller system includes a casing having an inlet portion and an outlet portion, a recirculation structure including a recirculation path and a recirculation discharge cavity, an impeller disposed downstream of the recirculation discharge cavity, a plurality of recirculation discharge guide vanes disposed to surround the recirculation discharge cavity, and a diffuser disposed in the outlet portion downstream of the impeller. The recirculation structure is configured to impart a swirl to a flow of refrigerant into the inlet portion. The recirculation path supplies the refrigerant from the diffuser to the recirculation discharge cavity. The recirculation path includes a recirculation pipe that introduces the refrigerant toward the plurality of recirculation discharge guide vanes. An annular groove is disposed between the recirculation pipe and the plurality of recirculation discharge guide vanes. An annular plate is disposed between the annular groove and the recirculation discharge cavity.

Methods and systems for detecting and recovering from control instability caused by impeller stall in a chiller system are provided. In one embodiment, an impeller stall detection and recovery component of a chiller control unit calculates a control error signal frequency spectrum for an evaporator leaving water temperature, determines whether a high frequency signal content of the control error signal frequency spectrum exceeds acceptable limits, and adjusts a surge boundary control curve downward by a predetermined incremental value in order to resolve instability caused by impeller stall.

A refrigerant cycle device for a vehicle includes a compressor which compresses and discharges refrigerant, a discharge capacity control portion which controls a discharge capacity of the compressor. The refrigerant cycle device further includes a noise determination portion which determines whether an audible noise other than a refrigerant passing noise is in a low noise state, and/or a load determination portion which determines whether an air-conditioning thermal load is in a high load state. The discharge capacity control portion performs a gradual activation control in which the discharge capacity of the compressor is set to be lower than that determined in a normal control, when the noise determination portion determines that the audible noise is in the low noise state, and/or when the load determination portion determines that the air-conditioning thermal load is in the high load state, at an activation time of the compressor.

A centrifugal compressor for a chiller system includes a casing having an inlet portion and an outlet portion, a recirculation structure including a recirculation path and a recirculation discharge cavity, an impeller disposed downstream of the recirculation discharge cavity, a plurality of recirculation discharge guide vanes disposed to surround the recirculation discharge cavity, and a diffuser disposed in the outlet portion downstream of the impeller. The recirculation structure is configured to impart a swirl to a flow of refrigerant into the inlet portion. The recirculation path supplies the refrigerant from the diffuser to the recirculation discharge cavity. The recirculation path includes a recirculation pipe that introduces the refrigerant toward the plurality of recirculation discharge guide vanes. An annular groove is disposed between the recirculation pipe and the plurality of recirculation discharge guide vanes. An annular plate is disposed between the annular groove and the recirculation discharge cavity.

A centrifugal compressor for a chiller system includes a casing having an inlet portion and an outlet portion, a recirculation structure including a recirculation path and a recirculation discharge cavity, an impeller disposed downstream of the recirculation discharge cavity, the impeller being attached to a shaft rotatable about a shaft rotation axis, a motor arranged to rotate the shaft in order to rotate the impeller, and a diffuser disposed in the outlet portion downstream of the impeller. The recirculation structure is configured and arranged to impart a swirl to a flow of refrigerant into the inlet portion, with a velocity of a recirculation flow caused by the swirl being higher than a velocity of the flow of the refrigerant in the inlet portion.

A method for controlling torque of an air conditioner compressor is disclosed. In one example, the air conditioner compressor is a variable displacement compressor. The method may provide smooth transitions between different air conditioner compressor torques.

A centrifugal compressor for a chiller system includes a casing having an inlet portion and an outlet portion, a recirculation structure including a recirculation path and a recirculation discharge cavity, an impeller disposed downstream of the recirculation discharge cavity, the impeller being attached to a shaft rotatable about a shaft rotation axis, a motor arranged to rotate the shaft in order to rotate the impeller, and a diffuser disposed in the outlet portion downstream of the impeller. The recirculation structure is configured and arranged to impart a swirl to a flow of refrigerant into the inlet portion, with a velocity of a recirculation flow caused by the swirl being higher than a velocity of the flow of the refrigerant in the inlet portion.

A method for controlling torque of an air conditioner compressor is disclosed. In one example, the air conditioner compressor is a variable displacement compressor. The method may provide smooth transitions between different air conditioner compressor torques.

The present invention relates to an air-conditioner system for a vehicle and a method for controlling the same, and more particularly, to an air-conditioner system for a vehicle and a method for controlling the same which can change a target superheat degree depending on variation in an amount of refrigerant discharged from a compressor, namely, gradually decrease the target superheat degree by stages as the amount of refrigerant discharged from the compressor decreases, and control an electronic expansion valve based on the target superheat degree dropping by stages, thereby preventing performance degradation of an air conditioner and stabilizing the system by restraining a change in the superheat degree in an area where an amount of refrigerant discharged from a compressor varies.

A method for controlling an air conditioner compressor of a vehicle is disclosed. The method includes adjusting a displacement command in response to an error between an expected air conditioner evaporator temperature and a measured or inferred air conditioner evaporator temperature, the displacement command is further adjusted via adding a value to the displacement command based on desired air conditioner evaporator temperature, the value determined apart from the error between the expected air conditioner evaporator temperature and the measured or inferred air conditioner evaporator temperature.