See Through Jet Engine

[Brian JohnParticipant @brianjohn93961]

Forgive me if this video has already been posted but I thought that it might be of some interest to model engineers on this site.

(887) See Thru Jet Engine – YouTube

It is not really a question but I did not know where to put it !

[Brian JohnParticipant @brianjohn93961]

[Thor 🇳🇴Participant @thor]

I have never seen the inside of a jet running before. Very neat demonstration.

Thor

[David George 1Participant @davidgeorge1]

Really good. When you have made parts for a full sized engine it gives you more insight to whst the bits do.

David

[Michael GilliganParticipant @michaelgilligan61133]

Excellent video, Brian … thanks for sharing it.

Good to see you posting here again

MichaelG.

[J HancockParticipant @jhancock95746]

Absolutely fascinating video.

The vital importance of balance and yet in full size , I do believe the roots of the blades of some stages are

floating.

How does that work ?

[JAParticipant @ja]

Yes.

We used to look into combustion chambers operating at atmospheric pressure. One stood beside the exit with a hand beside your face on the chamber side. Then you very carefully looked into the chamber until your hand started getting hot. No one was ever burnt but for other reasons the practice was stopped. One was testing at atmospheric pressure did not mean very much.

We also photographed inside chambers at high pressure through windows (made of sapphire I think). Once one broke and incinerated a Hasselblad camera (it was a very old one).

Running engines were looked into using high energy X-Rays in real time. You stayed well away from the test bed when that was done.

JA

Edited By JA on 30/06/2022 11:43:34

[noel shelleyParticipant @noelshelley55608]

AWSOME ! Noel.

[Brian GParticipant @briang]

A better view by far than the Gunson's "Colourtune", the only window into the combustion chamber accessible to the man in the street (normally at night).

Brian G

[Brian JohnParticipant @brianjohn93961]

Watching this makes me want to build one just for the sound alone !

[Gordon TarlingParticipant @gordontarling37126]

Posted by J Hancock on 30/06/2022 10:58:23:

Absolutely fascinating video.

The vital importance of balance and yet in full size , I do believe the roots of the blades of some stages are

floating.

How does that work ?

The compressor blades usually have dovetail roots and the turbine blades, firtree roots to attach them to the disc that rotates with the shaft.

[John Doe 2Participant @johndoe2]

Brilliant, but not at all sure about standing next to it, or even near it while it was running !

I don't know what the transparent tube is made of – sounded like glass – but if it shattered owing to the internal pressure and heat, the guy would have lost his eyesight. Hopefully the camera was locked-off and he was well out of the way.

Awesome demonstration though.

Regarding floating blades on the real thing; I am sure DG 1 or JA will correct me but, some, e.g. the big front fan blades, are a loose fit but they lock into place with centripetal force as the engine is started. They make a right old clanky noise when the wind blows them round on stand, and passengers boarding must think they are knackered !

[John PParticipant @johnp77052]

Posted by Brian John 30/06/2022 13:07:03

Watching this makes me want to build one just for the sound alone !

—————————————————————

Some useful download plans can be seen here from Gerald Rutten (zip files)
http://www.gerald-rutten.nl/turbines.htm

Photo here of some Wren MW 54 parts and some KJ 66 parts.
On the left wren MW 54 ,in the centre KJ 66 milled from the solid
compressor wheel and blank behind .

New compressor wheels can be found on Aliexpress for less than £20
like these here in the 2nd photo.

Standard 608 bearings can be used and are good to about 120,000 rpm
but have a short life . A cheap alternative is to re-ball a standard bearing
with Si3N4 ceramic balls ,the inner race needs to be reground to be able to
fit with a phenolic cage or fill the whole bearing to make a full compliment
bearing.

John

[Clive FosterParticipant @clivefoster55965]

Posted by John Doe 2 on 30/06/2022 16:18:50:

Brilliant, but not at all sure about standing next to it, or even near it while it was running !

I don't know what the transparent tube is made of – sounded like glass – but if it shattered owing to the internal pressure and heat, the guy would have lost his eyesight. Hopefully the camera was locked-off and he was well out of the way.

Awesome demonstration though.

Regarding floating blades on the real thing; I am sure DG 1 or JA will correct me but, some, e.g. the big front fan blades, are a loose fit but they lock into place with centripetal force as the engine is started. They make a right old clanky noise when the wind blows them round on stand, and passengers boarding must think they are knackered !

Reading down the comments it seems that he has developed his own transparent material that is much safer than a standard glass and additive mix in this sort of potentially dangerous shatter situation. He says he hasn't patented the mix because then he'd have to disclose it. Claims he knows what he is doing and fully understands how to create safe materials but ill advised copies could be very dangerous even though the mix is right. I guess its not just the mix but heat treatment and, possibly, pre-stressing involved.

Clive

[JAParticipant @ja]

Fan and compressor blades use dovetails these day (I think there is some clearance). These are complex and very carefully thought out. Turbine blades have almost always used fir tree fixings. Compressor blades on engines designed prior to about 1970 were often held by pins. The floating blades made the heavy clanking noise when the engine slowly rotated.

It is very unwise to be beside a running jet engine including a model jet engine. They are very safe but very very occasionally something happens (and makes the news). The energy levels are very high. In the case of the model in the video the pressure would be no more than two atmospheres across the transparent casing. If the transparent casing failed there would be some of slightly hot debris. The chamber might break up. Its metal temperature would be somewhere up to around 800C. The escaping gas would be between slightly warm and hot, hot being up to 1200C. The event would be over very rapidly with the engine running down immediately. You may receive some burns. A fire extinguisher would be very useful.

When our trainees/apprentices ran a model engine at work they had to use a full size testbed. I am sure this was dictated by H&S but would have given them an experience of test environments.

JA

Edited By JA on 30/06/2022 17:51:35

Edited By JA on 30/06/2022 17:52:49

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