| 摘要 |
<p>A compound shaft for a three journal bearing turbomachine is disclosed which includes a first stiff shaft supported by two journal bearings, a second stiff shaft supported by one journal bearing and by one bi-directional thrust bearing, and a flexible disk shaft that operably connects the first and second stiff shafts. The flexible disk shaft utilizes a flexible disk to function as a low hysterisis joint in parallel with a non-linear trunion clock spring such that the flexible disk shaft transfers overturning support from the first stiff shaft to the second stiff shaft and transfers thrust bearing support from the second stiff shaft to the first stiff shaft The flexible disk shaft allows the compound shaft to tolerate extremely large misalignments of the three journal bearings from a strait line axis. The dynamic characteristics of the compound shaft (especially the axial location of the flexible disk of the flexible disk shaft) are utilized to tune the frequencies of the turbomachine's rigid body and flexural criticals. All rigid body critical frequencies can be set below twenty percent of the machine's maximum operating speed and all flexural critical frequencies can be set more than thirty five percent above the turbomachine's maximum operating speed. When the compound shaft is supported by compliant foil hydrodynamic fluid film bearings (both journal and thrust), all negotiated rotor criticals can be extremely well damped (dimensionless damping coefficient Q of less than 2.5) and all criticals (both negotiated rigid body criticals and unnegotiated flexural criticals) need not be balanced. <IMAGE></p> |
