In a water-supply line for performing water-supply to the rotors and the mechanical seal of a compressor, or in a condensed-water collection line for collecting condensed water of a dryer into the inlet port of the compressor, a water reservoir is provided at a position higher than the water-supply unit of the compressor. Moreover, there are provided a start-time water-supply line and a solenoid valve set up therein. Here, the start-time water-supply line establishes the connection between the lower portion of the water reservoir, and the inlet port of the compressor and the water-supply unit of the mechanical seal.

A water lubrication air compression system disposes an lubricant heat dissipation system at a bearing chamber close to the high pressure end of the compressor for cooling and circulating lubricant due to the rise of temperature during operation of the compressor, hence enhancing the ability and stability of the compressor. On the other hand, a negative pressure system is connected to the air chambers between the oil lubrication and the water lubrication of the compressor in order to provide a negative pressure. If any leak of water vapor at the compressor chamber or oil vapor at the bearing chamber, the negative pressure system is able to produce a negative pressured condition toward the sealing structure so that the oil lubrication can be effectively isolated from the water lubrication and inter-contamination between the lubricant and water can be avoided.

A water lubrication air compression system disposes an lubricant heat dissipation system at a bearing chamber close to the high pressure end of the compressor for cooling and circulating lubricant due to the rise of temperature during operation of the compressor, hence enhancing the ability and stability of the compressor. On the other hand, a negative pressure system is connected to the air chambers between the oil lubrication and the water lubrication of the compressor in order to provide a negative pressure. If any leak of water vapor at the compressor chamber or oil vapor at the bearing chamber, the negative pressure system is able to produce a negative pressured condition toward the sealing structure so that the oil lubrication can be effectively isolated from the water lubrication and inter-contamination between the lubricant and water can be avoided.