4 ms·
I have a theory that we'll be able to reduce the RPM and increase the torque of these engines, versus conventional gas turbines and piston engines, thereby redu
by inamberclad 6y ago
I have a theory that we'll be able to reduce the RPM and increase the torque of these engines, versus conventional gas turbines and piston engines, thereby reducing the tip speed of the blades
- sokoloff 6y agoMaybe. The PT6A already has a gearbox, so the engineers are presumably able to choose a reduction ratio and prop RPM quite independently of the gas and power generator rotational speeds. (There are still torque limits in the gearbox output, though it seems the same constraints would face an electric motor.)
- dpe82 6y agoIn most planes, pilots are already able to chose their propeller RPM somewhat independently of torque by varying the pitch of the propeller. However, pilots typically optimize for rate of climb and not noise in order to get out of the low altitude / low airspeed danger zone as quickly as possible.
- sokoloff 6y agoYes. What GP is talking about though is changing the range of speeds available for pilot selection by changing the prop length, airfoil, maybe number of blades, and other design parameters. IOW, the design elements, not so much the operational element. Similar to how the C421 cruises at 1800-1900 prop RPM to give a(n eerily) quieter cabin.
- kohtatsu 6y ago"i.e." is functionally the same as your use of "IOW"; IMHO, FWIW. https://dictionary.cambridge.org/dictionary/english/ie https://dictionary.cambridge.org/dictionary/english/ie IOW made me think "I often wonder", but it didn't fit so I had to look it up: "in other words". I think i.e. is cuter. /digression/nit-pick
- sokoloff 6y agoWelcome digression/nit-pick/valued feedback. Thanks!
- esaym 6y agoeh, as torque and prop size goes up... tip speed also goes up.
- inamberclad 6y agoOr you can add more blades. Of course, you eventually hit a limit no matter what.