| 摘要 |
PROBLEM TO BE SOLVED: To prevent degradation in lubricating performance in an expander that uses a working fluid in a supercritical state.SOLUTION: In a movable scroll, a rotation angle &thetas;4 obtained by adding a fixed rotation angle to a rotation angle &thetas;3 where a working fluid reaches a critical pressure PC, is set as a switching position between a non-contact state and a contact state between a movable spiral wall and a fixed spiral wall. The pressure in the working fluid at the rotation angle &thetas;4 as the switching position is in a reduced state to a sub-critical pressure P2. The switching position represents a branching point whether the movable spiral wall is turned into a contact state or non-contact state with the fixed spiral wall at a plurality of contact points that segment an expansion chamber. In a region from a rotation angle 0 to the rotation angle &thetas;4, the movable spiral wall is configured to segment the expansion chamber in a non-contact state with the fixed spiral wall. On the other hand, in a region from the rotation angle &thetas;4 to a rotation angle &thetas;6, the movable spiral wall is configured to segment the expansion chamber in a contact state with the fixed spiral wall. Thus, degradation in lubrication performance of the expander can be prevented. |
