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