A compressor includes a bore, a rotor disposed within the bore, a compressor inlet, and a compressor outlet. The compressor further includes a compression chamber defined between the bore and the rotor, wherein a volume of the compression chamber gradually reduces from the compressor inlet to the compressor outlet. The compressor includes an economizer. The economizer is fluidically connected to the compression chamber. The economizer is configured to inject a working fluid into the compression chamber at an injection position. The injection position is changeable according to a working condition of the compressor.

An embodiment of a system with a minute measure of pulsatility in a flow of a fluid is described that comprises a first pump configured to flow the fluid to a junction at a first flow rate that comprises a measure of pulsatility; and a second pump configured to flow a portion of the fluid from the junction at a second flow rate that is less than the first flow rate to produce a flow of the fluid at a third flow rate from the junction with a minute measure of pulsatility.

A compression mechanism, and a scroll compressor, for the scroll compressor are provided, wherein the compression mechanism includes a movable scroll having a movable scroll end plate and a fixed scroll having a fixed scroll end plate. A movable scroll blade and a fixed scroll blade are engaged with each other to form a series of compression cavities between the movable scroll and the fixed scroll. A series of compression cavities include a central compression cavity and fluid compression cavities located on the radial lateral side of the central compression cavity. The compression mechanism is provided with a drainage channel and a drainage control mechanism, which enables the drainage channel to selectively provide fluid communication between a first fluid compression cavity in the fluid compression cavities and the outside of the compression mechanism.