Orpheus Conversion/Lip Thickening

KW Mitchell
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Re: Orpheus Conversion/Lip Thickening

Post by KW Mitchell »

Russ wrote: Interestingly, I did once see a film of a Harrier with an annular ring of ducts just behind the intake snapping open and shut very rapidly to cope with the pressure changes, presumably the aircraft was changing speed by a large amount during the filming. Although the Harrier was not supposed to be supersonic, it was capable of Mach 0.9+, so the air intakes had to cope with full range of controlled flight speeds from 0 to max, unlike everything else, which copes from take-off speed to max. The Harrier intake lip is more like that of commercial sub-sonic aircraft, though the ducts I mentioned above seem unique to it. Any further info on these is welcome.
Spring-loaded flaps were not unique to the Harrier and were very common on jets designed in the 50's-60's era. A good example - though sadly never developed - was the TSR2. See:

http://www.spyflight.co.uk/TSR2.htm

where several of the pic's show the flaps open. The reason for these flaps was to increase the mass-flow of air into the engine at low airspeed to increase thrust. They automatically closed at higher airspeeds as the ram effect into the intake increased pressure.

Interestingly, Bb's Orpheus would have benefited from their inclusion. They would certainly have increased thrust at low speeds which would have been useful to get Bb up and planing.

Russ
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Re: Orpheus Conversion/Lip Thickening

Post by Russ »

Keith,

Thanks for the info on the intakes. I'd assumed when I saw the Harrier film that the extra intakes were opening to dump excess pressure, but I can see now that they were actually there to suck extra air into the engine. That makes sense of them working by spring loading - when pressure is too low in the intake, the springs can open the flaps; when pressure is high enough in the intake it holds the flaps shut.

I might pop over to Cosford at the weekend to have another look at TSR2 now that I understand more about what I'm looking at. Thanks for sharing that info.

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rob565uk
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Re: Orpheus Conversion/Lip Thickening

Post by rob565uk »

Mike Bull wrote:I hope we do a bloody good job on the intake rivets! :shock:
I have just been reading "The World Water Speed Record" by Leo Villa and Kevin Desmond.

I was quite surprised to learn the following: (page 165/6):

"During an engine test on Wednesday 31 October 1957 the axial compressor was damaged due to something entering the air intake. When the engine was removed, it was found that several rivets and bits of the intake had come adrift and damaged the blades in the compressor chamber"

The book does not state whether a foreign object had been sucked into the intake and caused the damage, or whether the intake collapsed in an early imitation of the Orpheus-engined collapse in 1966. Nor does the book say if any remedial modifications were made. But the implication is that the intakes failed under load and were simply repaired afterwards.

Picking up on Mike's comment above, I know the current re-build is to the 1967 specifications and should therefore include all intake modifications, but for me the 1957 incident seems to further underline the need to pay special attention to the intake construction - even though the current Orpheus will not be operated at full thrust.

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Renegadenemo
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Re: Orpheus Conversion/Lip Thickening

Post by Renegadenemo »

We're onto it... Norris Bros. made a fatal error in the original design and the problem wasn't remedied until the inlets failed for the second time in 1966. That's why we conducted an extensive and in-depth post mortem on the inlets a while back - to find out what had been going on.
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quicksilver-wsr
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Re: Orpheus Conversion/Lip Thickening

Post by quicksilver-wsr »

Russ wrote: I might pop over to Cosford at the weekend to have another look at TSR2 now that I understand more about what I'm looking at.
Being new to this forum I missed all the earlier posts on this thread - including the one above from "russ" - but it's an interesting topic.

Intakes are a big deal, whether it's on an aircraft or a WWSR boat, and designing them right isn't easy - and they have to be built right too, otherwise they trash not only themselves, but the engine too, as occurred with K7.

The TSR2 ... What a plane! I never saw one when we were living in Preston, 1962-67, but my Dad was lucky enough to see one flying at nearby Warton. I was looking at the sole survivor "in the flesh" as recently as this Monday, and although I've seen it loads of times over the years, both at Cosford and at Cranfield where it lived a more private life before, in the College of Aeronautics collection, I never tire of it.

While you were at Cosford looking at the TSR2's intakes, "russ", I hope you took time to look at the examples of opposite extremes in the same hangar - the Hunting 126 and the Sepecat Jaguar. The intake on the Hunting 126 is your classic low-speed one - with a thick lip. This weird and wonderful contraption was the epitome of the low-speed aircraft, as - even though it was a jet - it could fly at speeds as slow as 32mph! The Jaguar, at the opposite end of the scale, exhibits the sharp intake lip associated with the high end of the speed range.

We spent a lot of time on research into WWSR intake design on Quicksilver, particularly when Ken Norris was leading the design effort. In fact, we built a big (1/5th-scale) model just to test the front half of the boat, with the intake, in the days when the design configurations we were looking at had the cockpit canopy directly in front of the intake.
Mike Bull wrote:I was re-watching the old ITN prog about ThrustSSC the other day, the one that shows pretty much everything the two-part BBC docu didn't - the car being built, first ever runs of the engines, car's first run under power when it burst a tyre, Jordan 1, etc. - and on SSC the engines were struggling at first because they weren't getting enough air in - they redesigned the intakes to incorporate a bell mouth to get them running sweetly.
True, Mike - they did - but what the documentary didn't show was that there was a particularly difficult problem arising during static engine tests on SSC, due to the close proximity to the ground. A vicious vortex would develop at ground level, rising up vertically, and get sucked straight into the engine and the poor old Spey couldn't breathe. So a clever solution was found. A "grid" of steel mesh was affixed to the ground immediately below the intake lip and this prevented a vortex being generated.

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Renegadenemo
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Re: Orpheus Conversion/Lip Thickening

Post by Renegadenemo »

There's lots of talk of poorly performing inlets and how crucial they are and I was even mildly told off once for sticking my head in a Eurofighter inlet because it was top secret - just looked like a bloody great hole to me. But there are plenty examples of inlets that were less than ideal yet worked anyway. When the Victor went from Sapphires to Conways the inlet didn't work as before but it still flew until they ironed out the bugs. Then there was a Victor prototype built to explore landing and takeoff at the high angles of attack assumed by deltas that had a pair of inlets almost identical to those on K7 smack in the middle of its back. They were known to be inefficient and fed a Derwent, which wasn't exactly spectacular to begin with, but the point is that they worked and the plane flew. K7's inlets weren't great but they weren't a showstopper either.
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quicksilver-wsr
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Re: Orpheus Conversion/Lip Thickening

Post by quicksilver-wsr »

You're right, Bill - they worked.

But there's no merit, that I can see, in designing an intake - or anything else, for that matter - that's inefficient, or nearly-good, or just OK. For a piece of industrial machinery, maybe. A machine that can sit and operate in optimum conditions all its working life.

But for a machine with a speed range of zero to 300 mph (K7), zero to 400 mph (Quicksilver) or zero to 600 mph (most jet aircraft) - with that very wide range of speeds, and therefore operating conditions, to have to operate in - it doesn't make sense to go for the easy option and just design a curvy hole in the bodywork, when the alternative is to do it properly. An inefficient intake can create problems - either by stalling, or "choking" - and in the worst cases it can stop a machine from doing its job.

All of that said, it's amazing what can be done. The Avro 707, a Derwent-engined research plane built for the Vulcan development programme, had two alternative and very different intake positions: a pair in the wing roots; and a single one atop the fuselage, just in front of the tail-fin.

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Renegadenemo
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Re: Orpheus Conversion/Lip Thickening

Post by Renegadenemo »

All of that said, it's amazing what can be done. The Avro 707, a Derwent-engined research plane built for the Vulcan development programme, had two alternative and very different intake positions: a pair in the wing roots; and a single one atop the fuselage, just in front of the tail-fin.
You make that sound like one plane with a choice of intakes... The 707B had a hole in the middle of its back while the 707A had the wing root intakes. Never got why they gave them letters in the wrong order though as the 707B was built first. All I was suggesting though is that although K7's intakes weren't fantastic their performance (or lack of) could be a red herring in terms of what happened to her later.
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Re: Orpheus Conversion/Lip Thickening

Post by quicksilver-wsr »

Yes, I was being lazy ... I didn't want to get into the A, B and C thing. But you've done it for me.

The point I was making is: one airframe design, two different - very different - intake solutions - one useful aeroplane (well, three actually).

I presume they designated them out of sequence because they weren't necessarily built in the order in which they were designed.

And your point about K7 is well-made, Bill - and, in fact, I have pretty much said the same thing over various posts on this forum, and that is that whilst K7's design wasn't perfect (and we can all, and do, pick holes in it) it worked. And how.

Iffy intake and all.
Last edited by quicksilver-wsr on Sat Apr 24, 2010 1:04 pm, edited 1 time in total.

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Renegadenemo
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Re: Orpheus Conversion/Lip Thickening

Post by Renegadenemo »

The point I was making is: one airframe design, two different - very different - intake solutions - one useful aeroplane (well, three actually).
There was a 707C too, pretty much the first aircraft to try fly-by-wire. How far ahead of its time?
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