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Two or Three Spools?

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Two or Three Spools?

Old 7th Apr 2021, 20:17
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Two or Three Spools?

A question here for those in the know after a debate on another forum. Is Rolls-Royce new UltraFan design considered a two spool or a three spool engine? On their homepage RR describes that the engine uses Advance 3 core design, but as I see it the UltraFan only have two turbine sections and only two concentric axels, with the inner axel driving the LP compressor as well as the fan section through a reduction gearbox, kind of the same way as on Pratt & Whitneys GTF design.

Any thoughts?
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Old 7th Apr 2021, 20:38
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Looking at the mobile page (so who knows how the hell it relates to the normal page) as well as the Wiki, it seems that the Advance is a 3 spool engine like the rest of the 211/Trent lineage, and the Ultrafan is based on that but goes to 2 spool/geared fan
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Old 7th Apr 2021, 21:18
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well if you took away the fan and just ran it as a pure jet, the question becomes how many stages of compressor and small dia turbines do you need to achiever an optimum pressure/fuel burn.

This sounds like a Tdtracer analysis is needed (keep the nacelle drag low and the weight low and at the same time improve the fuel burn enough to fill a niche)
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Old 7th Apr 2021, 22:10
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When PW announced the GTF concept I remember a spokesperson from Rolls being a bit sniffy saying its like having a "two and half spool engine".

Looks like PW are on to something after all... as long as they get the bowed rotor problem sorted. 😁
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Old 8th Apr 2021, 11:16
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Originally Posted by F-16GUY View Post
but as I see it the UltraFan only have two turbine sections and only two concentric axels, with the inner axel driving the LP compressor as well as the fan section through a reduction gearbox, kind of the same way as on Pratt & Whitneys GTF design.
Any thoughts?
I agree.
at time 30 secs says "we have removed the low speed turbine" and the diagram only shows 2 spools.
The IP turbine drives the fan through the new clever gearbox - but it is still marketed as having 3 shafts.

Last edited by Goldenrivett; 8th Apr 2021 at 11:22. Reason: extra info
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