Discussion
Quite common on older engines.
They’re called fixed inlet guide vanes or stators. They present the air at the correct angle to the first stage compressor.
The Rolls Royce Conway has them too (any many more engines from that era I imagine)
Don’t seem to get them anymore, you get variable inlet guide vanes (VIGVs) but they’re mounted further inside/along the compressor for core air only.
They’re called fixed inlet guide vanes or stators. They present the air at the correct angle to the first stage compressor.
The Rolls Royce Conway has them too (any many more engines from that era I imagine)
Don’t seem to get them anymore, you get variable inlet guide vanes (VIGVs) but they’re mounted further inside/along the compressor for core air only.
Edited by EddyBee on Sunday 17th February 16:23
EddyBee said:
Quite common on older engines.
They’re called fixed inlet guide vanes or stators. They present the air at the correct angle to the first stage compressor.
The Rolls Royce Conway has them too (any many more engines from that era I imagine)
Don’t seem to get them anymore, you get variable inlet guide vanes (VIGVs) but they’re mounted further inside/along the compressor for core air only.
Thank you for replies, I thought they were an odd thing to have at the front of the engine. They’re called fixed inlet guide vanes or stators. They present the air at the correct angle to the first stage compressor.
The Rolls Royce Conway has them too (any many more engines from that era I imagine)
Don’t seem to get them anymore, you get variable inlet guide vanes (VIGVs) but they’re mounted further inside/along the compressor for core air only.
Edited by EddyBee on Sunday 17th February 16:23
They can be seen quite clearly a few times in this film:
https://youtu.be/7fwLnq9IsU4
I wasn’t sure if modern low bypass engines had them, i’ve only worked old stuff with low bypass.
I’ve just remembered that at the end of September in 2001 I was in America with my mum and we were flying on some rear engined American Airlines aircraft (MD80?)
My mum was all panicky because of 9/11, we were seated near the back. I thought one of the engines had been shut down as I couldn’t see the fan blades spinning.
I kept quiet as I didn’t want to scare my mum. Turns out it was the IGVs I could see haha. I was only 12 mind.
I’ve just remembered that at the end of September in 2001 I was in America with my mum and we were flying on some rear engined American Airlines aircraft (MD80?)
My mum was all panicky because of 9/11, we were seated near the back. I thought one of the engines had been shut down as I couldn’t see the fan blades spinning.
I kept quiet as I didn’t want to scare my mum. Turns out it was the IGVs I could see haha. I was only 12 mind.
Mabbs9 said:
I remember seeing a C5 close up. The outer portion of the engine has a set of stators at the front with a conventional compressor section in the centre.
The C5 engines have a pretty unusual arrangement - the conventional looking centre section is in front of the main fan, and driven by the same shaft. I'm not aware of any other engine like it, although there are many where the engine is "T" staged by having an extra core-only compressor on the back of the fan.Eric Mc said:
Turbofans have the rotating fan at the front of the engine. There may be stator blades further downstream of the turbofan.
One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
GE basically took a J79 (as used in the B-58 and the F-4 Phantom) and stuck a completely self-contained fan unit on the back, which had quite a clever design with combined turbine/fan blades - the inner part of the blade was the turbine, the outer part the fan. It meant that the core J79 unit could be used virtually unchanged and avoided the complication and expense of the two-spool turbofan system. One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
In reference to the OP, it also meant that the front of the engine had both a visible rotating fan in the middle (for the compressor part of the original jet unit) and fixed vanes on the outside ducting air to the rear fan. It made it look like something out of Thunderbirds:
EddyBee said:
Cheers for the above. Never knew that i love strange engine designs like that.
The Ulta hi bypass designs were interesting too
They look like something out of science fiction.
The Ulta hi bypass designs were interesting too
They look like something out of science fiction.
Eric Mc said:
Saw that aeroplane fly at the 1988 Farnborough Air Show. Boy was it noisy.
One of the Dorling-Kindersely books of planes I had when I was a kid had the MD-94X with the UDF engines on the last double-page spread as an example of 'The Future of Aviation', confident that by the year 2000 (so far off...so futuristic!) they'd be standard on short/medium-haul airliners. I've just done some reading-up on the GE36 UDF and it used exactly the same principle as the Convair 990's CJ605s - the unducted blades aren't geared, simply being directly attached to a free turbine mounted behind the main gas-generator part of the engine which, just as the CJ605 was a J79 with a turbine bolted on the back, was an existing F404 as used in the F/A-18 and the Stealth Fighter. The UDF's turbine blades were alternately angled so they contra-rotated. Interesting how a design borne of expediency in the 1950s still had uses in a very different application 40 years later. Which is why firms like GE never throw anything away!
2xChevrons said:
Eric Mc said:
Turbofans have the rotating fan at the front of the engine. There may be stator blades further downstream of the turbofan.
One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
GE basically took a J79 (as used in the B-58 and the F-4 Phantom) and stuck a completely self-contained fan unit on the back, which had quite a clever design with combined turbine/fan blades - the inner part of the blade was the turbine, the outer part the fan. It meant that the core J79 unit could be used virtually unchanged and avoided the complication and expense of the two-spool turbofan system. One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
In reference to the OP, it also meant that the front of the engine had both a visible rotating fan in the middle (for the compressor part of the original jet unit) and fixed vanes on the outside ducting air to the rear fan. It made it look like something out of Thunderbirds:
2xChevrons said:
Eric Mc said:
Turbofans have the rotating fan at the front of the engine. There may be stator blades further downstream of the turbofan.
One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
GE basically took a J79 (as used in the B-58 and the F-4 Phantom) and stuck a completely self-contained fan unit on the back, which had quite a clever design with combined turbine/fan blades - the inner part of the blade was the turbine, the outer part the fan. It meant that the core J79 unit could be used virtually unchanged and avoided the complication and expense of the two-spool turbofan system. One odd exception was the General Electric CJ605 (used to power the Convair 990) which had the fan assembly at the rear.
In reference to the OP, it also meant that the front of the engine had both a visible rotating fan in the middle (for the compressor part of the original jet unit) and fixed vanes on the outside ducting air to the rear fan. It made it look like something out of Thunderbirds:
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