A dynamically balanced cylindrical rotor with a hollow hub and a series of curved blades is rotated freely in the eccentric casing. The sufficient sealing water / liquid forms a solid ring on the periphery of the casing, due to the centrifugal force, the rotor is rotated in the eccentric casing, the rotating blade creates working spaces whose volume increases as the rotor rotates from lower to upper vertex and decreases as the rotor rotates from upper vertex to lower vertex. The uniform distribution of working spaces on rotor periphery results in continuous suction and exhaust of gases.