Engineering Aero and Industrial Gas Turbine Technologies

Nilgiri

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Nilgiri

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The look into the engine starts around the 10 minute mark, the fuel injector RnD is covered especially nicely for the layman and is part of what I have been involved with in PW's case:

 

Nilgiri

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Resurrecting this thread for some potential updates and discussion later in neutral broader format.

New and returning members can also have read of earlier posts and reference material....and I will try my best to answer any specific questions with time.

A bit later I will try contribute relevantly to all 3 countries gas turbine propulsion threads as well: 🇹🇷 🇰🇷 🇮🇳


=========================================

For now here is quite interesting archive footage and explanation:

With stunning archive images, explore in great details the complex manufacturing processes developed to build a turbofan jet engine. We take you back in time, in 1983 at Snecma’s (now Safran Aircraft Engines) facility near Paris. From there, you will witness the incredible complexity behind the manufacture of a turbofan jet engine.

From the preliminary studies, assisted with computers and magnetic memory systems, to the Gennevilliers’s drop hammer’s delivering the 80,000 kg/meter of energy needed to forge the rotor’s disks, this video precisely recounts how compressor rotors and jet engines were manufactured at Safran’s factories almost 40 years ago. We hope you enjoy the show!


 

Rodeo

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You have, previously, written many times about turbine engines, saying that the real problem of enlarging engines or raising the turbine inlet temperature is the apparent issue of turbine blade creep. Since the materials used are essentially metals, even if they're cast in single crystals, they still suffer from creep and that is the determining factor of engine's service life, MTBO, efficiency etc.

Now in light of these new materials, namely CMCs,

- Will the industry start exploring designing bigger and more powerful engines for the airliners, or will they just increase the inlet temperature of the turbine?

- Do these ceramics need active cooling?

- Are they thicker or thinner than SCBs?

- How many years of research have GE put into this technology before applying(for demonstration) it for the first time?

- How much of a potential is there in terms of TIT difference and overall engine efficiency between SCBs and CMCs?

- How big of a moat does GE have with this technology?

---

Thanks for the twitter thread. It was informative.
 
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Nilgiri

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I ended up making my reply longer than I first intended, well might as well see how it goes.

@TR_123456 @Yasar @Saithan (iirc who Ive chatted with before on topics like this), et al.

@Saiyan0321 (to provide a read for you this time, reverse of the usual lately :p )

You have, previously, written many times about turbine engines, saying that the real problem of enlarging engines or raising the turbine inlet temperature is the apparent issue of turbine blade creep. Since the materials used are essentially metals, even if they're cast in single crystals, they still suffer from creep and that is the determining factor of engine's service life, MTBO, efficiency etc.

Yes that was within the envelope of that material (metals broadly speaking, of which Nickel super alloys are the apex we have found for this environment).

However this material envelope is also bounded by the melting point as well (which in many ways influences creep and its failure mechanisms leading up to it).

So essentially by pushing the melting point bound to much higher amount (i.e essentially drastically increasing the turbine blade melting point and raw thermodynamic apex), we gain much more envelope to work with within which new considerations for creep etc again have to be studied and analysed to mitigate.

Of larger concern right now compared to creep though (given the physics of CMC's especially the ceramic matrix) are specific corrosion failures particular to them that need EBC (Environmental barrier coating) research, testing and application (and consequent redevelopment/improvement of EBCs and solutions for serious issues still plaguing them)

These essentially kick in at earlier stages of operation compared to metal super alloy...and are main scope of research to solve first for CMC for more reliable operation to harness in sustained way their higher temperature performance in the way they theoretically promise.

There are promising results so far, but the feedback loop in RnD and real world application will take time.

Now in light of these new materials, namely CMCs,

- Will the industry start exploring designing bigger and more powerful engines for the airliners, or will they just increase the inlet temperature of the turbine?

- Do these ceramics need active cooling?

- Are they thicker or thinner than SCBs?

- How many years of research have GE put into this technology before applying(for demonstration) it for the first time?

- How much of a potential is there in terms of TIT difference and overall engine efficiency between SCBs and CMCs?

- How big of a moat does GE have with this technology?

1) Will the industry start exploring designing bigger and more powerful engines for the airliners, or will they just increase the inlet temperature of the turbine?

Well the ability to increase TiT (Turbine inlet Temperature) essentially means bigger and more powerful engines become possible (holding every other iterative or frontier tech involved the same).

i.e it makes sense to add more turbine stages (and related compressor stages) for each given diameter in higher temperature environment of the hot section that is impossible to have today (they would simply melt etc, so this restricts how many turbine sections make raw thermodynamic sense with the TiT scope we have today).

The fan diameter of say a turbofan is essentially linked in the end to the TiT due to the maximum thermodynamic potential of the engine core due to this.

So you improve the TiT and hot section thermodynamic scope (holding all else the same), you can make more powerful/larger cores and thus make larger fans to gear air around to achieve the even larger total thrust now on offer compared to before.

Conversely making more efficient cores at each given size become possible as you extract more energy out of each given air flow rate with this TiT now in operation.

Carnot efficiency stuff in the end regarding temperature (1 - T cold / T hot)



2) Do these ceramics need active cooling?

Active cooling will help them just like with any other material. i.e same amount of active cooling will give that much more operating condition past what would otherwise be available.

Conversely can also reduce the active cooling needs (for say smaller simpler engine design) for every given temperature (that makes sense) and have more performance envelope retained compared to previous materials.



3) Are they thicker or thinner than SCBs?

Same thing here, holding all else the same, for same thickness of material you will get more thermodynamic resistance and environment performance.

Or conversely you can reduce thickness to retain same environment performance. In the end its the thermal resistance "intensity" of the material if you will.



4) How many years of research have GE put into this technology before applying(for demonstration) it for the first time?

Gosh thats hard to put a real finger on since the fundamental research of note was started by others in the 1970s (and one can find even earlier research in the 50s and 60s and maybe possibly earlier, though this was still exploratory at the time).

There was a heavy injection of research funding by Oak Ridge labs (US DOE) around the 80s and I guess you can say once more results matured from those, GE picked this up in broader way around the early 90s.

More info:

So you can say GE particular IP legacy in the area is maybe 20 - 30 years now.

Rolls Royce has since also shown great interest (to advance to rotatable in the end)

PW is so far reluctant (CMC is mostly being kept for static parts or cold section only going forward) and conservative in picking Nickel superalloy to persevere with in hot section.... and iterate and improve further (and going "all in" for geared turbofan engine design for their unique frontier push... among other things like adaptive cycle research like the others are doing too).



5) How much of a potential is there in terms of TIT difference and overall engine efficiency between SCBs and CMCs?

It is hard to say right now, it depends on how the feedback comes from how the EBC stuff goes (application wise in real world) to sort out that reliability tier first (for say GE).

If they manage it well with no new issues popping up from that, and specific creep research matures for CMC nicely, then there is a huge scope for substantial thermodynamic improvement of the jet engine in both raw output way and efficiency way.

You can try use Carnot I gave before just now to get a rough idea, plugging in numbers :) ...and remembering that a 1% efficiency improvement is a huge deal.

1-s2.0-S0955221920308700-gr1.jpg

From: https://www.sciencedirect.com/science/article/pii/S0955221920308700

The creep mechanisms are extremely different, complicated (even if you are familiar with them regarding Ni superalloy) and long subject to get into for CMC given they are essentially composite bi-material (and hence single crystal is not option for manufacturing) with two basic creep rates at play.


6) How big of a moat does GE have with this technology?

I would say its fairly large moat, but how big it is and relevant it is will only be seen with time. Maybe this decade provides more answers or the next one.

Say what they are able to mature versus say RR (who started later but are just as interested in this avenue) and PW who are going a different conservative fork in the road in the end but watching as well and who knows might play catch up later again if this all bears out in certain advantageous way for the other two (and fork out IP/JV acquisition spending for it from those two, its not uncommon).


Anyway be sure to tag any folks you think might be interested in the subject and I will try progress the discussion slowly over time to our collective interest and time etc.

There is also the deeper question of why? CMCs have this superiority over metals intrinsically....and how to summarise that in a few lines.

Maybe I'll do that next time....because it explores material science/chemistry fundamentals in a more generic way that could provide answers for lot of engineering advancement this century using one or two specific elements. CMCs are just a small current fruit of this tree we have now, when we can hopefully grow an orchard in future.

Some extra things to read in interim as to your free time and interest:


EDIT: I inserted the questions in directly like a FAQ format.
 
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Rodeo

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Will CMCs be the last major leap in turbine engine technology before electric airliners take over in 20+ years(assuming battery densities come to the figures that will make electric passenger planes possible and feasible)?
 

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Will CMCs be the last major leap in turbine engine technology before electric airliners take over in 20+ years(assuming battery densities come to the figures that will make electric passenger planes possible and feasible)?
That is a good question about electric planes. But call me old fashioned or a pessimist. But in today’s world, I don’t trust all electric cars and I still won’t trust all electric planes when/if they become available. If The core energy supply is not onboard I am reluctant to invest in that propulsion system. That is why I will not buy an all electric car. Hybrids are OK. Electrodiesel type transmission-less engines are OK. But rechargeable all electric is still a no no for me.
RR is working on small nuclear power reactors. That is a good way to go especially if the reactors can be miniaturised in a cost effective way.
Hydrogen power cells should have a good future as well. In fact logically hydrogen, if can be produced with safety considerations and in an environmentally friendly way, is the way forward. It is the most abundantly present fuel supply.
In short, my logic says ; If the core energy supply (petrol, hydrogen, nuclear) is on board the platform it is to power, then it is good. A “tangible” energy supply should be on board the platform.
Electricity stored in large and heavy batteries does not instil confidence. When batteries are light enough to carry on board or purchased as replaceable fuel cells then I will change my stance.
 

Rodeo

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If The core energy supply is not onboard I am reluctant to invest in that propulsion system. That is why I will not buy an all electric car.

Don't you think the definition of "core energy" is a bit arbitrary? If we followed up the chain, we'd say the solar energy is the core. Or if we go one more step up, it would be nuclear fusion.

Hydrogen power cells should have a good future as well. In fact logically hydrogen, if can be produced with safety considerations and in an environmentally friendly way, is the way forward. It is the most abundantly present fuel supply.
In short, my logic says ; If the core energy supply (petrol, hydrogen, nuclear) is on board the platform it is to power, then it is good. A “tangible” energy supply should be on board the platform.

Green Hydrogen makes up only 0.04% of the total hydrogen production. It's still made from oil, natural gas and coal. Besides, hydrogen is very troublesome to work with. Despite our current technology, it's very hazardous to store and transport hydrogen.


I agree with the small nuclear reactor part. I'm actually very excited for this technology. Small or micro nuclear reactors will be the answer in the long term for both utility electricity production and onboard electricity production in vehicles, not renewables, imho.

On Mars, after 10 years of operation, Curiosity rover is still kicking. It uses some kind of nuclear-powered battery. It has no solar panels. It would be amazing not having to fuel(or charge) your car for months. Wouldn't it? :cool::D
 

Nilgiri

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Forgot to tag @Cabatli_TR @Test7 and @Mis_TR_Like @Gessler @Sanchez @Anmdt et al. to this discussion if they would like to read/participate etc.

Will CMCs be the last major leap in turbine engine technology before electric airliners take over in 20+ years(assuming battery densities come to the figures that will make electric passenger planes possible and feasible)?

No I think there will be lot more advancements in the thermodynamic tech route (jet engines being the arguable frontier of it) that will provide good active and legacy (inertial) competition to any breakthroughs in say energy density for batteries in the electrodynamic propulsion route (that does away with the thermal/combustion component as major advantage but is limited by that energy density and raw transmission ability in both physical and practical ways)

It has to do with what I said earlier:

There is also the deeper question of why? CMCs have this superiority over metals intrinsically

material science/chemistry fundamentals in a more generic way that could provide answers for lot of engineering advancement this century using one or two specific elements. CMCs are just a small current fruit of this tree we have now, when we can hopefully grow an orchard in future.

The deepest DNA of this "tree" so to speak is our current understanding of atomic physics and chemistry.

Specifically a "sweet spot" that occurs in this realm in 4 bordering elements of the periodic table:

periodictablezoom.jpg



i.e B (Boron), Al (Aluminium), C (Carbon) and Si (Silicon).

A certain physical "magic" happens in precisely these 4 as they relate to precise ratios stemming from the electron structure at this particular size of the atom (every atom nucleus itself essentially being a multiple of Hydrogen in the end).

i.e the sweet spot of these four being the only ones having the combination of certain potentials from their unfilled electron (p) orbitals, the p orbital distance to nucleus and importantly not having d orbitals (yet) to interfere.

Carbon is especially special of these 4....in many ways the most "magical" element of all given this phenomenon applies to it in such a way uniquely (helped by mathematics of 4 being a factor of 8 and 12 ....4 in this case being the electrons carbon has in its 2nd electron shell, precisely halved between s and p orbitals as well).

This is why Carbon is the element more than any other that has its own dedicated huge field of (organic) chemistry and its known as the element of "life" for the same reason.

This is also why Silicon plays its role in semiconductors and various intrinsic crystal properties as well.

This is why they both (along with the other 2) have intrinsic properties that the mainstream metals (which have d orbitals and larger orbital distances introduced) simply do not have when it comes to certain engineering properties governing strength, thermal resistance and so on.

That is large reason why (Carbon) Steel was found as a big improvement over pure Iron for example....at a time we could not really explain why it did (or even knew what Carbon was).

They are big enough but not too big for the optimal building block size you can say for many things....but they needed advancement in research and understanding to utilise them (especially specific ways) compared to what is on offer with trial and error with more readily producible/accessible metals and other legacy engineering materials in history.

This is the underlying reason CMCs (that go out of their way to stay only within these 4 "bricks" along with oxygen which is like a mortar) harness and express this phenomenon in a way that is impossible for a transition metal superalloy to do so.

Thus when we break the nano engineering barrier to intense enough degree, carbon will see the dominant application in that realm as well (in whichever ground up + controlled growth way we can design and implement)....compared to say melt infused CMCs and other processes we are limited to now.

They will play a large role in advancing the electrodynamic side (especially the energy density side) for similar reasons (to provide the high structural resolutions for electron packing and fine structural strength needed in advanced batteries that are just in conceptual stage), you can count on that.

Or at the risk of sounding a bit too whacko like some do when they read up some (original) Nikola Tesla conceptual theory/research.....consider wireless energy transfer systems (think induction resonance expanded to great ranges, so you dont even need to carry a battery, just a resonant receiver, taking advantage of nanoscience resolution amplifying this for any given size/volume).

i.e what is the actual maximum we can reach here when we are no longer largely stuck to operating on conventional macromaterial scale like we are now?

Lot of folks dont quite understand now the scope of things to unlock in the nano scale (when we get breakthroughs to really expand application there) given its very hard to visualise just how much of that fits in dimensional scales we more readily see.



That is a good question about electric planes. But call me old fashioned or a pessimist. But in today’s world, I don’t trust all electric cars and I still won’t trust all electric planes when/if they become available. If The core energy supply is not onboard I am reluctant to invest in that propulsion system. That is why I will not buy an all electric car. Hybrids are OK. Electrodiesel type transmission-less engines are OK. But rechargeable all electric is still a no no for me.
RR is working on small nuclear power reactors. That is a good way to go especially if the reactors can be miniaturised in a cost effective way.
Hydrogen power cells should have a good future as well. In fact logically hydrogen, if can be produced with safety considerations and in an environmentally friendly way, is the way forward. It is the most abundantly present fuel supply.
In short, my logic says ; If the core energy supply (petrol, hydrogen, nuclear) is on board the platform it is to power, then it is good. A “tangible” energy supply should be on board the platform.
Electricity stored in large and heavy batteries does not instil confidence. When batteries are light enough to carry on board or purchased as replaceable fuel cells then I will change my stance.

Conventional thermodynamic propulsion (be it chemical, nuclear or renewable sourced.... mechanical, electromechanical or electric transferred....or even other nonconventional sources and transmissions and hybrids of all of these that become feasible and practical) will definitely play a very large role in human endeavour/transport going forward.

They will compete with non-thermodynamic propulsion systems that are in relative infancy now still.

They will not become obsolete for a long time, maybe even never....as they will also be carried along on the path of nanoscience (and further unlocking of these 4 elements at those scales, especially C and Si) once that path (and other frontier paths) become increasingly unlocked.

The precise mix of pros and cons of optimal systems developed in future from this is really anyone's guess....but in all likelihood there will be a varied mix depending on their relative pros/cons in each relative breakthrough era of development/progress here.
 

Yasar_TR

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Don't you think the definition of "core energy" is a bit arbitrary? If we followed up the chain, we'd say the solar energy is the core. Or if we go one more step up, it would be nuclear fusion.
I think you and most people would know in general, what I mean by “core energy” supply. For a combustion engine or a jet engine it is the petroleum based fuels. For battery powered cars it is the continuous supply of electrical energy generators or spare, light but high capacity, easy to change batteries when they become available. For nuclear it is the uranium rods. For hydrogen based propulsion it is the hydrogen fuel cells.
When nuclear fusion based energy becomes available it will definitely be the salvation of world’s energy predicament. As well as being self sustaining, It will also provide means for clean and comparatively cheap and safe supply of electricity and cheap and green production of Hydrogen fuel through electrolysis.
In spite of its troublesome and somewhat dangerous features, hydrogen is the fuel for future. Siemens of Germany has dedicated huge resources to the production of green hydrogen.
Hydrogen fuel cells may outlast the vehicle they are fitted in. A fuel cell fitted to a car can last as long as 200 thousand miles with fuel replenishments every 300-400 miles with current level of technology.
Miniaturised Nuclear reactors have a lot of potential too. But when fusion based energy becomes available it will dominate the energy sector.

EDIT

Now going back to turbine powered jet engines, a turbine engine powered by electricity will provide high degrees of cold air thrust out of it’s nozzle. Almost all commercial airline engines have high bypass engines whereby around 85-90% of the thrust is provided by the bypassed cold air around the engine core. So an electric powered turbine would be a more silent and green solution when it is a civilian airline it is powering.
But when it is the case of high altitude flight of military planes and as the air is rarified in higher altitudes and the thrust provided by fans alone is not enough, we will need jet thrust propulsion. A combined cycle engine that transforms from a turbojet to ramjet or even a scramjet, may be the solution for this.
Food for thought!!

1686306962312.jpeg


 
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