I was just looking at an old picture of how a jet engine works…multiple stage compressors and turbines. Basically the setup is shafts within shafts. Often three or more nestled within each other.
Question is…how do they lubricate the shafts? I mean, are these shafts permanently sealed, lubed for life? Or is there some kind of oil pump which reaches the bearings and seals on the inner-most shaft?
All bearings on current-technology turbine engines are oil-lubricated (and oil-cooled, not incidentally). If you look closely at a detailed engine cross-section, you’ll see the bearings are inside sumps, with oil supplied into and scavenged from the sumps through tubes run through the engine frames (generally through struts). Rotating seals of various designs, combined with aerodynamic designs that keep air pressure higher outside the sumps than inside, keep the oil inside the system. Oil supply and scavenge pumps, sometimes inside the same housing and sometimes not, are mounted on the external gearboxes and create the flow.