How to build a Jumbo Jet Engine Anyone?

[John Farley]

suninmyeyes

Re cost - according to the programme we are talking about here R-R said they didn't 'sell' engines in the normal sense of the word but charged airlines a by the hour cost (power by the hour is a term often used in this context). For this R-R guarantee to keep a serviceable donk on the wing for x hours.

[Jo90]

Great programme.

Can someone explain how it is possible to run a blade above the melting point of the alloy it's made from. Is it something to do with the cooling air preventing the accumulation of latent heat?

[lomapaseo]

Can someone explain how it is possible to run a blade above the melting point of the alloy it's made from. Is it something to do with the cooling air preventing the accumulation of latent heat?

That's about it

The blades actually run in air above their melting point. The design challenge is to keep the bulk temperature of the blade from getting up to air temperature.

The inside of the blade is cooled while the outside has a barrier coating that can survive the temperature.

There is a constant development program upgrade to :

improve cooling by distribution or extract more air from the compression cycle)

Barriers, longer lasting coatings (they ablate away with times

Higher temperature bulk blade materials (directional or single crystals, etc.).

Somewhere along the development cycle of an engine you have to freeze the design in order to start ordering parts. Thus an engine entering service may not represent the latest technolgy in technical print or TV shows.

[lomapaseo]

The RR Trent 895 that hangs on the BA 777 apparently has a 'basic engine weight' of 13100 lbs. Couldn't find anything on the RR website about the weight of the engine

It's the add-ons in the installation package designed by the customer that significantly vary the weight. Of course just like a car engine the engine by itself is not very useful sitting on a loading dock.

[P.Pilcher]

I always used to like the quote from DB Davies' "Flying the Big Jets" about the original RB211 and its American equivalents:
"On takeoff the power developed by each engine on the Jumbo's wing is developing eighteen times the amount of power of the most powerful reciprocating engine ever developed."
What that figure for the latest Trent is I hate to think!

P.P.

[gas path]

It's all down to the cooling. HP compressor air being used as the cooling medium flows through the centre of the blade and out of the cooling holes predominately around the leading edge creating a 'cool'! laminar film.
This was part of the concern regarding the recent volcanic ash chaos. Blockage of the cooling holes would lead eventually to a burn though and an unscheduled engine change. JFI it would not result in a catastrophic failure, more like a slight reduction in performance for example increasing fuel flow and consequently EGT as the engine EEC attempted to keep the selected EPR/N1 on target
Trent 800 basic weight 15700lbs 7136 kgs

[gas path]

What that figure for the latest Trent is I hate to think!

Most powerful Trent to date is the 895. 95k lbs of thrust.
The GE90-115. 115k lbs of thrust. The development -115 was run to 127500lbs.....just the once! With everything on the redline!

[Old and Horrified]

Biggles78

You will probably have to use a proxy server to watch BBC iPlayer when outside of the UK. Search PPrune for lots of posts explaining how. Don't forget that programmes only stay on iPlayer for one week.

I too enjoyed the programme hugely. Do fan blades still rattle? I remember on the DC-10 that a slowly windmilling engine on the ground used to rattle quite alarmingly.

[gas path]

[QUOTE Do fan blades still rattle?][/QUOTE]
No 'part span shrouds' on these latest engines, unlike the earlier CF6/Jt9d or RB211 engines.

[barit1]

The development -115 was run to 127500lbs.....just the once! With everything on the redline!

Every new design must pass this "Triple redline" test - rotor speeds AND EGT simultaneously redlined for 5 min. to insure the parameter combination can be tolerated, if briefly.

Generally it can only be accomplished with a unique combination of hardware and ambient conditions, and often with a "jimmied" fuel control.

[BarbiesBoyfriend]

Watched the programme. Personally, I was extremely impressed.

Actually, it made me feel a bit choked up, watching these guys do their stuff. I felt proud.

Way to go Rolls Royce!

[Swedish Steve]

growing single crystal turbine blades which run 300 degrees above their melting temperature,

I believe that the single crystal blade was the most significant change that made the big fans reliable.
In 1978 the RB211 had cast HP Turbine blades. On the Tristar we had a fixed life of 1200 cycles before removal and scrapping of these blades, and HPT blade failures before this were very common!
Then along came the single crystal blade, and engines lived longer, a step change that doubled engine life on the wing.
In 1978, with a fleet of 12 Tristars, we were changing at least one engine a week.
Now the RB211 Trent produces more than twice the power (the -22B had 42000 lbs) and seemingly lives for ever.

[BarbiesBoyfriend]

Swedish.

How good is that?

I thought that RR went bust, back in 1971, due to trying to make the RB -211 fan out of carbon fibre?

True, or not?

Apart from the 'short editing' a brilliant film!

[gas path]

I thought that RR went bust, back in 1971, due to trying to make the RB -211 fan out of carbon fibre?

It was indeed the carbon fibre fan that nearly destroyed RR. The technology of the day just wasn't up to it. The bit of archive film shown of the first RB211 had the CF Fan.
GE had similar problems with the Fan on the GE90. The machines that were made to build up the fan were just not up to the job so the blades are layed up by hand. IIRC in two halves before entering the autoclave. Even so the blades have a Titanium leading edge and trailing edge. They have proved to be very robust in service suffering only from some erosion of the plastic protective film. The 3d aero blades on the -115 however can suffer from delamination following a bird strike and are then subject to an NDT test.

[barit1]

While a modern CF/Ti fan blade may be worthy of an art museum, it's the HP turbine blade that's a real marvel. Considering the dovetail stress load, the airfoil design, and the cooling passages both visible and in-, it's a wonderful example of form following function.

[Starter Crew]

Cost of these engines - high.

Suninmyeyes

On one of my trips through the propulsion shop here at Boeing, it was explained that the engines typically can approach 30 percent of the total cost of the delivered aircraft (of course the exact price paid is negotiated and usually secret). However, they are the biggest single external cost we add.

A quick Google job turned up a "list price" for the Trent as $17 million, so if anything near accurate, that bears out the PSD guys' assertion.

They are so expensive that at Boeing we accept delivery of the engines for attachment at the very last possible moment. And yes, they are things of beauty!

[lomapaseo]

Now days the cost to build often outweighs the selling cost on paper. It's the cost of servicing and parts under contract where the profit is made.

Of course the cost to build is borne by the manufacturer and if not sold just-in-time can near bankrupt a company. Thus the timing of the transfer of ownership can mean everthing to a Chief Financial Officer of a company.

Many financial numbers get juggled and as time changes the profit end of the business floats back and forth between costs of doing business.

I remember one time looking at the cost of insurring for product liability among various aviation business models and was surprised to see that the inusurrance cost percentage vs product costs varried by at least 10 to 1 between business models. (the various manufacturers are private). I'm sure that there are many other aviation related business models that can demsonstrate similar variations

[Pugilistic Animus]

and it all started with the metallurgy problems presented by steam turbines then through turbochargers finally up to the wonderful engines of today...the method for casting the turbine blades,... is the ancient method of 'Cire Perdue' or lost wax

the story of jet engines is beautiful...


JT..I'm gonna need new glasses because of this place

[Landroger]

Lompaseo and Starter Crew.

Now days the cost to build often outweighs the selling cost on paper. It's the cost of servicing and parts under contract where the profit is made.

Although our CT and MRI scanners are very high tech', they are not engineered to anything like the standard required by an aero engine, but your point has been a truism for many years Lompaseo. Very little profit is taken on the manufacturing, mostly because the competition is so fierce, but the ten or so years our kit is usually in service is where the money is made. I should add rather hastily that our kit can and will remain effective and reliable long outside the nominal ten year life the NHS and private hospitals usually account for.

A quick Google job turned up a "list price" for the Trent as $17 million, so if anything near accurate, that bears out the PSD guys' assertion.

They are so expensive that at Boeing we accept delivery of the engines for attachment at the very last possible moment. And yes, they are things of beauty!

Thus making about £10 million a pop, which is pretty much what I guessed and entirely understandable why Boeing fit them JIT - like Sainsbury's!! This, however, begs the question as to who exactly buys the engine? Is it Boeing/Airbus who then sells it (them) on to the purchaser of the aeroplane? Or are they sold directly to the customer, to be delivered on the wings of their new aeroplane, so to speak?

I have been delighted at the response to my original post, both here and on my 'usual' forum (not aircraft/airline oriented) and also my work colleagues. Almost everyone who has a technical, scientific or engineering 'bent', has responded much as all the above. To wit, moved in some way by what they saw in the programme and highly appreciative of what RR are doing at Derby.

What I haven't yet been able to divine, is how non scientific/engineering people viewed the programme. I have quite strong views on how people's minds work and how different the mind of an engineer is to, say, a lawyer. If my theory is correct, then a lawyer or maybe a policeman, would merely view the engine and its components as just another - very expensive - widget. Any views?

Roger.

[fhegner]

To those of you - and me - who are not living in UK,
the alternative.......A torrent:

How To Build A Jumbo Jet Engine WS PDTV XviD-FTP torrent - Torrentzap torrent downloads

choose the green download 'button'