Centrifugal compressor for Daikin McQuay Chiller (WSC/WDC/WCC, DSC/DDC/DCC)
CE087M serials.
Pls contact to: inform@aplushealth.com.cn to get leadtime.
Lower Vibration
A gear-driven compressor runs at higher impeller rotational speeds but tends to have less vibration than the larger, much heavier, direct drive units. All McQuay compressors must pass a stringent vibration test while running on the production test stands. Spring isolators are normally not required for most applications.
Unique Lubrication System
With the higher rotational speeds and much lighter running components compared to direct drive units, efficient hydrodynamic bearings can be used. The shafts are supported on a film of lubricant, rather than running with metal-to-metal contact, typical of rolling element bearings.
Under normal circumstances, the McQuay bearings have a theoretical infinite life while rolling element bearings do not.
Selectable Impeller Speeds
Another gear drive advantage, over the older design direct drive units, is the ability to select gear ratios that will provide the optimum impeller tip speed for a given application. Impeller speeds can be selected to provide sufficient pressure lift ability without the excessive tip speeds that lead to inefficient compressor operation.
Moveable Diffuser
McQuay has pioneered the use of moveable discharge geometry to lower the surge point of centrifugal compressors. The point at which the compressor enters a stall or surge condition generally limits compressor unloading. At low loads, low gas velocity through a fixed discharge area results in low gas velocities and the gas can stall or surge in the impeller. When in a stall condition, the refrigerant gas is unable to enter the volute due to its low velocity and remains stalled in the impeller. In a surge condition the gas rapidly reverses direction in the impeller causing excessive vibration and heat. McQuay compressors reduce the discharge area as load decreases to maintain gas velocity and greatly reduce the tendency to stall or surge.
Liquid Injection
A small amount of liquid refrigerant is taken from the condenser and injected into the compressor discharge area. The liquid droplets absorb sound energy and reduce the compressor’s overall sound level. The droplets evaporate and reduce discharge superheat.
Power Loss Damage Protection
Unfortunately, loss of electric power without allowing chillers to proceed through their normal
shutdown sequence is becoming common in many areas. When this occurs, most compressors must coast to a stop without benefit of their lubricant pump running. Poor lubrication at this point can damage the bearings and reduce compressor life. McQuay compressors are equipped with a lubricant reservoir and a piston with a compressed spring that provides pressurized lubricant to the bearings during the coast-down period. Also, the compressors decelerate quickly due to the low inertia.
