TURBOEXPANSION DEVICE FOR SUPERCRYOGENIC REFRIGERATING MACHINE

摘要

PURPOSE:To reduce the load acting on bearings which support a turbine shaft or free the bearings of such a load so that the operation can be stabilized even under a large expansion pressure ratio by reversing the relative directions of the thrusts acting thrustwise upon a first turbine and a second turbine. CONSTITUTION:There are provided a housing 20 comprising a bearing chamber 25 and expansion chambers 27, 77 formed at the respective ends of the bearing chamber, a turbine shaft 38 supported in the bearing chamber of the housing and held freely rotatable, a first turbine 37 held at one end of the turbine shaft and facing the expansion chamber 27, and a second turbine 87 held at the other end of the turbine shaft and facing the other expansion chamber 77. When actuating fluid is fed, the first turbine 37 and the second turbine 87 rotate with the turbine shaft 38 therebetween. Therefore, expansion of actuating fluid takes place both at the first turbine and the second turbine. Then the direction of the thrust acting thrustwise upon the first turbine is opposite to the direction of the thrust acting thrustwise upon the second turbine. Thus the thrust acting on the turbine shaft 38 at each end is reduced or offset.