How do you make a GE90 fan blade

[JammedStab]

Like this....

And they do twist a full 90 degrees from base to tip.

https://www.youtube.com/watch?v=g8zt...ature=youtu.be

[Piltdown Man]

Thanks for that. I never appreciated that there were so many steps and so much machining involved in manufacturing carbon blades.

[riff_raff]

Very interesting video. Did not realize that so much of the composite work was performed manually. The finished fan blade is absolutely beautiful.

[Pugilistic Animus]

Very cool video, no wonder those engines cost a fortune.

[riff_raff]

The price of modern commercial turbofan engines seems high until you consider the value they provide to the customer. Those composite fan blades are designed to last the full service life of the engine. Jet fuel is expensive, and the lower weight and increased performance provided by these composite fan blades pays off quickly in reduced fuel consumption.

[msbbarratt]

Good video, that.

I read once an article explaining why RR hadn't pursued CF fan blades again (they tried a long time ago, back in the 1970s) until relatively recently. It turns out that with a CF blade you actually need a fair bit of material near the root; not surprising really, it's got to take the entire load on the blade (radial and thrust). That translates into the root actually being quite chunky, which compromises the airflow into the engine core.

Thus RR's position was that whilst CF might be lighter, the core performance is worse. By sticking with hollow Ti blades, RR could make them thin along their entire length, improving core air flow, and gaining performance back that way. Labour costs during manufacture were a secondary issue.

Of course, there's no way of knowing whether the differences add up to a net advantage or not. Both RR and GE's engines are phenomenally good, though on some aircraft (e.g. A380) the RR engine has the weight advantage (can't remember if the GE/PW engine uses CF blades or not).

What is interesting about RR's up-coming Ti-CF fan blades is that now, with different fibres and lay-up techniques, they think that they can make thin blades, all the way to the root. Apparently they've also been concentrating on automated layup. With that being so, RR can now do a light weight blade with good aerodynamics at the root and decent weight savings.

Another aspect common to all CF blades is that it's easy to get any shape blade you like (within reason). If we ignore root area, you can make a blade an ideal aerodynamic shape. With a hollow Ti blade it's phenomenally difficult to shape (RR have become very good at it of course), so there's some compromises to be made between the shape the aerodynamicist wants and the shape the manufacturing guys say they can produce...

It will certainly be interesting to see how RR's blades perform. Thin, any-shape, light-weight fab blades should translate into exceptional fan efficiency.

RR are relatively public about all this, and seemingly have three major technical advances on the way (TiCF fan, GTF, and they're even talking about variable pitch fan blades). Any two of those taken together are really going to advance the state of the art. All three together would be really quite something.

GE are much quieter, but unless they want to be wiped out from the large turbofan engine market they've got to be engaging in a ton of R&D themselves. I'm sure they are.

It's all going to be very interesting to see what emerges from these companies over the coming years.

I've had an opportunity to look at some of the blades RR experimented with back in the 1970s. They were really quite something, considering. Very light. Looking at them it's clear that the lay up techniques employed then were much simpler than GE / RR / everyone else uses today. I've no idea exactly what these ones were, and I'm not even sure that they were usable (look at the resin at the fir tree). These may have been really early prototypes, just to see if they could make something that shape.

[hoss183]

I once (back in the 70s) visited the Rolls Royce production line at Filton and was fascinated by the lost wax casting of the titanium turbine blades. An altogether older technology, but the precision and hand crafting of the wax forms was very impressive.

[Concours77]

Having a background in composites going back a very long time, I am still awestruck by GE's amazing ability to work what is basically mud and straw into such sophisticated products.

Now, here comes Ceramics.

fossil.....

[Zaphod Beblebrox]

And here is how you manufacture a "blisk", that's a combination "blade" and "disk" assembly. I think the cooling issues on the newer engines may be attributable to the problems of cooling and heating "blisks" in a uniform manner. A big chunk of metal with thin blades machined integrally to that chunk is not likely going to cool or heat evenly.

https://www.youtube.com/watch?v=FCfZQMPQa7g

[EEngr]

Interesting. But a bit scary at one point. The high speed video had a guy pushing a rack of blades into the autoclave. And then it appeared that the door closed behind him.

[Volume]

But he clearly is still alive when they open the door agin
No humans were harmed in the production of this vedeo...

[tdracer]

Back around 2005, I was at the GE Customer Training Center in Evandale (outside Cincinnati) for a meeting. They'd moved the GE history of turbine engine 'museum' there (it had been in the basement of one of the office buildings).
Anyway, there was a display of the GE90-94B, including a claim that there had never been a GE90 composite fan blade that had to be scrapped due to operational damage (bird strike, FOD, etc.). Pretty darned impressive, although I don't know how much longer it lasted (or if it extended to the much different design of the GE90-115B fan blade).
The GEnx-1B (787) and -2B (747-8) fan blades are similarly impressive, although I'm pretty sure the GEnx-2B can't make a similar claim regarding not needed to scrap any blades. There was an incident a few years back on a 747-8 where the outboard engine ingested a snow bank () and suffered quite a bit of fan damage.

[Turbine D]

A GE90 fan blade is in the Smithsonian in Washington, DC I think as an example of both art form and technology.



The technology has expanded beyond fan blades, the GEnex and new LEAP engines have composite outer fan casings that eliminate the need for the Kevlar wrap to prevent uncontained failures.

[Concours77]

Turbine D

Hi.

In my travels I have run across some interesting composites.

Keeping in mind there are composites that shrink when heated, would that conceivably play a part in engine technology? I am thinking of the fan rim's leakage at the cowl?

I met Turbine "A" many years ago, a vocal critic of the 787. Composite thread?

The first aircraft to fly made of composites? The Wright Flyer, utilizing the original two phase materials, lumber and linen.

[lomapaseo]

Keeping in mind there are composites that shrink when heated, would that conceivably play a part in engine technology? I am thinking of the fan rim's leakage at the cowl?

Simple just use the flexible properties in the material to stretch and untwist to close down the leakage path.

There is always a balance between too much and not enough, hence the abradeable material of the gas path

[Concours77]

Thanks

My thought as well. However, reliance on the structure itself to abrade shortens the life of the blade. A coating on the inner cowl needs replacement periodically, and the performance degrades over time (albeit in predictable, though expensive fashion).

I would add "accretable" tip structures to the blades made of metallic infused ceramic. The resultant crystalline oxides would add dimension to the fan diameter over time conceivably with no limit life. As friction due sealing creates oxides, the material serves as a "growing" gasket.

patent pending.

[lomapaseo]

That accretable material is a natural result of rubbing on metal to metals etc. It then exists in an extremely high velocity field at tip speeds. The result is that it becomes a birthing field for flow eddys and blade tip stall.

You don't want accretion and you don't want blade tip wear, so you go for either open clearances of the early jet engine years or an abradeable case that lends itself to overhaul repair.

[Volume]

The first aircraft to fly made of composites? The Wright Flyer

Or the Lilienthal Normalsegelapparat. Primary structure made from cellulose fibre reinforced lignin a.k.a. wood.
It is funny to see how the glider industry directly moved from wood to composits applying exactly the same construction principles, while large aircraft industry went via all metal, and forgot about all the basic design methods of (natural) composites, now basically building aircraft from black aluminum, laying up sheet composites, cutting out parts and riveting them together...

Did not realize that so much of the composite work was performed manually.

If you want to use the full potential of the material, this is the way to go. If you just need to compete with conventional metal design, need to keep repairability of the product and labour cost is the driver, then you do a fully automated production of a very simple design.
If you severely damage your fan blade, you anyway replace it. No matter whether metal or composites. So no need to design for easy (riveted...) repair.

Keeping in mind there are composites that shrink when heated, would that conceivably play a part in engine technology?

Only carbon fibre shrinks, and only along its axis. All other fibres and resins do expand. Carbon expands perpendicular to the fibres. You can taylor your thermal deformation according to your need when defining the layup sequence, just like you can taylor strength, stiffness and the mode of deformation. You can make a blade twist when exposed to centrifugal forces, making your fan a constant speed propeller. You can make flaps or control surfaces soft in bending and stiff in twisting, reducing secondary loads and loads on the hinges. This is the major difference to isotropic metal, which has the same stiffnes and thermal expansion in all directions.

[tdracer]

now basically building aircraft from black aluminum, laying up sheet composites, cutting out parts and riveting them together...

Volume, you need to brush up on how the 787 is made - large, complex one piece composite pieces that are autoclaved then bolted together for final assembly. What you're describing is closer to how the A350 is built - with the advantage of easier reparability but higher weight.


Concours, the designers are quite good at maintaining the desired tip clearances as the turbine heats up - most blade rubs are the result of thermal shocks or flow disruptions (most of the heavy fan rub strip wear we see during flight testing is after very high angle of attack testing where the inlet sometimes separates. Unless there are materials out there that don't change at all with varying temperature, there's not much of a carrot there.

[megan]

the designers are quite good at maintaining the desired tip clearances as the turbine heats up

The J-58 of the SR-71 would grow some inches in diameter during cruise. Should the power during descent not be managed correctly the pilot on more than one occasion found himself flying a glider due rotor lock, the casing having cooled quicker than the internals.