A screw compressor according to an embodiment includes a rotor casing, a pair of screw rotors disposed in the rotor casing and engaging with each other, and a movable portion disposed so as to be movable in a rotor shaft direction of the pair of screw rotors. The movable portion includes liquefied liquid supply ports capable of supplying a liquefied liquid of a compressed gas toward tooth groove spaces formed by the pair of screw rotors.

Gas expansion device for expanding a gas or a gas-liquid mixture, where the gas expansion device includes a gas expansion element with an inlet port for the gas to be expanded and an inlet pipe for the gas to be expanded. The inlet pipe is connected to the inlet port where the gas expansion device includes a first liquid injection point for the injection of liquid, where the first liquid injection point is at a position level with the inlet port or upstream from the inlet port.

Liquid-injected compressor element or expander element with a housing that comprises a rotor chamber in which at least on rotor is rotatably affixed, whereby the element is further provided with a connection for an injection circuit for the injection of liquid into the element, whereby the connection to the injection circuit is realised by means of an injection point in the housing that opens into the first compression chamber or expansion chamber. The connection to the injection circuit is additionally realised by means of an additional injection point in the housing that opens into a second or subsequent compression chamber or expansion chamber.

Gas expansion device for expanding a gas or a gas-liquid mixture, where the gas expansion device includes a gas expansion element with an inlet port for the gas to be expanded and an inlet pipe for the gas to be expanded. The inlet pipe is connected to the inlet port where the gas expansion device includes a first liquid injection point for the injection of liquid, where the first liquid injection point is at a position level with the inlet port or upstream from the inlet port.

A controller unit for controlling the speed of a motor for driving an oil injected compressor, the controller unit including: a data connection; and a first module to receive data through the data connection. The controller unit includes a processing unit for determining a minimum working speed of the motor on the basis of the measured working pressure, the ambient temperature and a dew point temperature; and a comparator unit to compare the determined minimum working speed with the retrieved working speed of the motor. The processing unit includes a signal generating unit to send a signal to the motor for increasing the working speed of the motor to at least the determined minimum working speed, if the retrieved working speed is lower than the determined minimum working speed.

An oil circuit for lubrication and cooling of an oil-free compressor with an oil reservoir and a rotary oil pump to drive oil to the compressor element and/or the motor via an oil pipe. The rotary oil pump has a rotor mounted on a rotation shaft, and is driven by the motor of the compressor. The oil circuit is provided with a bypass pipe and a pressure-actuated bypass valve which guide a portion of the oil back to the oil reservoir without this portion of the oil passing through the compressor element and/or the motor during its way back to the oil reservoir. The oil circuit is further provided with an oil cooler in the bypass pipe. The bypass valve is in the oil pipe.

A compressor system is provided that includes a contact cooled compressor and a coolant separator. The coolant separator is used to remove coolant fluid from a compressed flow stream produced by the contact cooled compressor during its operation. The coolant separator routes the removed coolant fluid back to the contact cooled compressor for further use. In some forms the coolant fluid is cooled prior to delivery back to the compressor. A stop valve can be provided in the coolant fluid return line to halt the flow of the fluid. A pressure sensitive member can be disposed to sense pressure of the coolant fluid that has been routed past the stop valve. Operation of the compressor can be changed as a result of the sensed pressure from the pressure sensitive member. Information from a temperature sensitive member can also be used to change operation of the compressor.

The present invention provides an oil feed type air compressor that can reduce a power consumption of a compressor body during an unload operation. The oil feed type air compressor includes: a compressor body (1) compressing air while feeding an oil into a compression chamber; a separator (4) disposed on a discharge side of the compressor body; a compressed air-feeding system (5) feeding the compressed air separated by the separator to a use destination of the compressed air; an oil-feeding system (6) feeding the oil separated by the separator to the compression chamber of the compressor body; an oil cooler (11) and a temperature sensor (12) disposed in the oil-feeding system; and a controller enabling execution of a temperature control. The temperature control by the controller is performed by variably controlling a rotation speed of a cooling fan (13) such that, during the load operation, a temperature detected by the temperature sensor is a target value T1, and during the unload operation, the temperature detected by the temperature sensor is a target value T2 (with the proviso of T1>T2).

A compressor system can include a lubricant injection system useful to supply lubricant to an airend. The compressor system can include a variable lubricant flow valve which can be regulated by a controller on the basis of operating conditions of the compressor system. In one form the compressor system also includes an oil separator and/or an oil cooler with or without a thermal control valve. The controller can have one or more modes of operation, including a mode in which the controller regulates the flow of lubricant to the airend to increase an internal flow area of the valve when the airend is operated at an unloaded or loaded condition. In some forms the controller can regulate the lubricant flow valve and/or the thermal control valve and/or the lubricant cooler.

A Method for controlling the liquid injection of a compressor device or expander device. This compressor device includes at least one compressor element or expander element, whereby the element comprises a housing that comprises a rotor chamber in which at least one rotor is rotatably affixed by means of bearings, whereby liquid is injected into the element. The method comprises the step of providing two independent separated liquid supplies to the element, whereby one liquid supply is injected into the rotor chamber and the other liquid supply is injected at the location of the bearings. The separated liquid supplies are realised by means of a modular channelling piece of an injection module.