Kaveri & Aero-Engine: News & Discussion

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ramana
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Re: Kaveri & aero-engine discussion

Post by ramana »

Ok. What should be discussed? lets make sure we don't get sidetracked. Thanks, r
Indranil
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Re: Kaveri & aero-engine discussion

Post by Indranil »

We can start with the dry thrust, SFC, TWR, max obtainable pressure ratio of Kaveri with the original M88 core. Is it ideal? If not, how has the core to resized (obviously up), but by how much?
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Re: Kaveri & aero-engine discussion

Post by Eric Leiderman »

https://www.reuters.com/article/us-ge-d ... SKCN1G100D

This could be like the TATA Jag deal if a PVT company wanted to step in
ramana
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Re: Kaveri & aero-engine discussion

Post by ramana »

Eric Leiderman wrote:https://www.reuters.com/article/us-ge-d ... SKCN1G100D

This could be like the TATA Jag deal if a PVT company wanted to step in

It's industrial gas turbines for onsite power generation. Maybe Ambani can buy them up.
maitya
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Re: Kaveri & aero-engine discussion

Post by maitya »

ramana wrote:Maitya, Maybe I should have addressed you?
IR if you know any Kaveri design guy ask him how a M88 core(designed for BPR 0.3) will work in a Kaveri (Designed for BPR 0.16) shroud?

I don't think it will unless its de-rated.
And they say its dia is smaller than the Kaveri shroud.
Ramanaji, apologies, b/w issues galore :( and thus I'm not fast-enough to churn enough posts wrt such queries etc ... by the time I've got enough to write, the discussion moves on so much that there's no point in posting whatever I would have gathered/analysed etc. :((

Anyway, have no clue or contacts in Kaveri team etc - so don't know/can't answer your above question.


However, I did play around with their respective published figures 8) , combining them for this hypothetical M88core-but-rest-kaveri-with-high-BPR and there are some interesting figures that it threw up.

Will post that soon, once I've figured out how (and where) to upload an image and then how to link it from here etc ...

Some snippets though ...
As expected, the M88 core with higher TeT and matching-high-OPR (pls refer to Kaveri sticky for the relationship between them) but with much lesser core-mass-flow, produces almost as much (slightly less) dry thrust as Kabini ...

So, by almost as a corollary, when mated with Kaveri, due to much larger mass-flow available at the overall engine face, and irrespective of the higher BPR in M88, this core-mas-flow goes up by as much as 20% (compared to what the current M88 in a Rafale type setup handles).
This will have to increase the dry thrust (from the core only) quite a bit - as per my simplistic calc, by as much as 16%.

But because of high BPR, the thrust obtained from the bypass air-stream would approximately double, taking the overall dry-thrust go up by as much as 25-30%.

However, that in itself is a fallacy ... as I suspect M88 HPCs will simply melt (again pls refer to the Kaveri sticky thread for the relationship between mass-flow and the compressor RPM and the resultant ambient temp increase etc) if such a large core mass-flow is "imposed" upon it.

But then again 15%-20% increase in core mass-flow is not very uncommon in various known "evolutions" (for example F404 to F414 etc) in various leading injin design-houses worldwide ...

More later ... (once I've figured out how to upload an image and link it back from here etc).
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Re: Kaveri & aero-engine discussion

Post by Indranil »

Use imgur for pictures. Message me if you have difficulties.
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Re: Kaveri & aero-engine discussion

Post by Haridas »

Maitya ji,
Good one, thank you.
The other way is to keep the M88 core intact w.r.t OPR and TeT and core flow. That would increase the BPR (assuming no change in intake design) and dry thrust, but with changed thrust performance at various speed and altitudes; in particular resulting in lower maximum velocity specification on dry-power for the aircraft (due to higher BPR).
IMHO the engine would perform very well in trans-sonic regime (current achilles heel)
JMT.
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Re: Kaveri & aero-engine discussion

Post by NRao »

I wonder if it is possible to build the Kaveri core with the materials that the M88 core uses. Will need knowhow of manufacturing parts with the materials, which is probably the risk. I very much doubt the French will divulge that. Even supply of material could be too much to ask for.
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Re: Kaveri & aero-engine discussion

Post by Avtar Singh »

I am sorry but I can only discuss from a user point of view.
I really would not like to get my hands dirty with the engineering side of things, :D
also my brain is not big enough for technical engineering side.... YAWN :-?
my understanding is only "need to know"

I prefer the excitement of monkey see, monkey do.

Can this by pass ratio discussion be taken to a technical thread.
I come here with baited breath to hear the news; "Indian jet engine flies"

For gods sake put whatever one has to hand into an airframe and run it,
keep running it incrementally until it flies. Use jugaad to just get on with it.
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Re: Kaveri & aero-engine discussion

Post by Indranil »

We will move the important parts to a sticky technical thread. But Sir, your request is quite bizzare. You are asking the mods to reduce discussion on this thread to fluff!!!

You have the option of not reading technical posts!
ramana
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Re: Kaveri & aero-engine discussion

Post by ramana »

Avatar


For gods sake put whatever one has to hand into an airframe and run it,
keep running it incrementally until it flies. Use jugaad to just get on with it.
Unfortunately this wont happen as Tejas, is an unstable design and this one conks out in flight it will fall like a stone. No glide.

So Kaveri technical discussion is very much needed.
The whole weakness to my eyes is the low BPR thing.

I will tell you my gut feeling:

GTRE had a turbojet engine that works in prototype.
So they wrapped a small fan around it and claimed its a turbofan.
A BPR of 0.16:1 is almost like nothing. Its practically a turbojet.

Might as well put a Rallis fan (my old hostel fan) in front of the turbojet and pull some air through the duct work.

And no one was the wiser till it did not perform.
And now the SAFRAN guys, who were consultants all along and part of the fiasco, are now stepping in and offering M-88 core which is smaller in size so has to be resized and has higher BPR on this Kaveri.
A lot more work.

So SAFRAN is getting paid twice once as Kaveri consultant and now as Rafale offset consultants.
After this is spent they will wash their hands and walk away having swallowed the Rafale offset money.

In dehati terms they are making ulloo of us. GTRE and SAFRAN.

We know the fan, the rest of it works.
Make a new core to match the system. Call it kabini-2 or what ever.
By now they could have designed the new core.
And you don't need SAFRAN or Turmeric.

And my hunch is even with the M88 core it wont solve the problem.

The offset money should be used to get real benefits then making a bullock cart into a Tata Nano.
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Re: Kaveri & aero-engine discussion

Post by maitya »

ramana wrote:<snip>
I will tell you my gut feeling:

GTRE had a turbojet engine that works in prototype.
So they wrapped a small fan around it and claimed its a turbofan.
A BPR of 0.16:1 is almost like nothing. Its practically a turbojet.

Might as well put a Rallis fan (my old hostel fan) in front of the turbojet and pull some air through the duct work.

And no one was the wiser till it did not perform.
<snip>
Sorry Ramanaji, you being too simplistic here, I'm afraid!!

Let me complicate this thought process of yours, by adding this following data:

The predecessor to GTX-35VS turbofan (which they almost* re-christened as Kaveri/Kabini) was the "14" series turbofan called GTX-37 14UB which had ~0.22 BPR - almost 26% more than the much-denigrated 0.16 BPR wala current version, hain jee?
(*"almost" - as they did add FADEC and attempted a flat-rating concept on it before calling it Kaveri etc)

And, moreover, almost same BPR as that of the uber F414, right?
(admiralji, you now get my drift, when I said "... not right ..." etc, in my reply, isn't it?).


Anyway, pls refer to the following chart:
Image

Now why on earth the GTRE folks would reduce BPR when they already had a working turbofan with higher BPR and, that too with higher wet thrust (thus must be with a higher dry thrust as well).

Pls think thru.

I'll revisit this strawmanish question once I've completed this M88-core-in-Kaveri conundrum anal-ysis.
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Re: Kaveri & aero-engine discussion

Post by ramana »

Maitya, Thanks for correcting me.
I didn't know about the GTX-37UB turbofan.
I am wrong.

So what happened here?

I not that the HPC section is coming down from 7 to 5 and rises to 6.
Is this the reason for underperformance?

Was the intake an issue for the Tejas?
Smaller diameter leading to lower BPR? And the reduced number of stages from 7 to 5 to now 6.
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Re: Kaveri & aero-engine discussion

Post by Neela »

Was looking at maitya Sir#s excel and also M88 core numbers
M88 TET is 2870F (1576C) . The last time I read about TET some 5 years back, I recall state of the art being 1400 C :(
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Re: Kaveri & aero-engine discussion

Post by ramana »

OK. GTX-37UB did not fit the intake geometry of the Tejas.
Too big a diameter.

I don't know the diameter of the 404 and 414 vs. Kaveri diameter.

So what all this means is the Kaveri out shell, the intake etc. match the Tejas.
What's needed is a new core that provides the needed thrust with extra stage 7 vs 6.

We know the 404 and 414 have intake diameter that fits the Tejas. 35"x154" length
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Re: Kaveri & aero-engine discussion

Post by Philip »

Get the Supreme Court into action.We might then see a solution to this most excruciatingly long "pregnancy" of Kaveri"!
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Re: Kaveri & aero-engine discussion

Post by Neela »

Saurav Jha ( read from bottom to top )

@SJha1618
In any case, the foreign partner was more interested in a much larger project that would have seen the creation of a new core for the Kaveri design for 90 KN plus wet thrust. That project however is also not seeing light of day because GTRE is probably seen as a failure lab.
@SJha1618
The money required to make that happen, if at all, is not likely to be sanctioned & the foreign partner who was being roped in for this has basically lost interest according to sources.

@SJha1618
As far as the status of domestic low-bypass turbofan engine development is concerned, there is no good news I am afraid. It seems that the likelihood of existing Kaveri SoP prototypes ever reaching flight worthiness is diminishing rapidly.
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Re: Kaveri & aero-engine discussion

Post by sum »

If a optmist like Saurav Jha is so gloomy and dark, guess the curtains are finally coming to a close on this saga
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Re: Kaveri & aero-engine discussion

Post by JayS »

Ramana saar, why are you so hung up on BPR, exactly..?? I really do not understand why there is a discussion on BPR going on here. There is no one ideal number for mil jet for BPR. It boils down from basic system level propulsion requirements. Isn't it obvious enough that Kaveri's low BPR was a result of imposed flat-rating requirement...?? F404/RM12 even today are not flat-rated. I never seen any reference so far saying F414 is flat-rated. If Kaveri achieves all its design goals by any means, it would have bettered F404 already (given F404 is 35-40yr old engine thats not unexpected now, but OTOH setting up with those goals in 1980s was too brave and foolish design perhaps).

Similarly F119 has a BPR of 0.2, which is a result of imposed requirement of supercruise. Would you call it, not a turbofan..?? At what BPR exactly Turbojet starts becoming Turbofan..??
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Re: Kaveri & aero-engine discussion

Post by Zynda »

Sad to read that snippet from SJha about current status of jet dev in the country. So what GTRE is a failure lab? Few people I respect the most are aware of the fact that they have to "unlearn & relearn" many things constantly. Unlearning at a senior age can lead to an impression of being "wrong" & relearning can be interpreted as a sign of failure in Indian culture...

I dunno perhaps it is time to spin off GTRE in to a private entity (the best option would be to a collab wtih Scnema & Indian partner or partners) on the existing land/infra facility in BLR. They can retain many of the staff to start with but slowly restructure as needed. Of course the bulk of R&D money still would be expected to foot by the GoI until a workable product is ready...the further improvements for which will likely be funded by private entity. My onlee hope from the above is the ability to do good project management, bring in the right people at good compensation (something which is very hard to do in the current set up), retaining existing talent and importantly addition of needed infra resources. Even with all of the above, a state of the art product would be challenging. I am sure many of the above is already being done by the Chinese & they are struggling to get a reliable power plant.

Anyways, I think India is thinking along the lines of Israeli defence industry i.e. have good avionics, armament industry & many of the sub-systems be Indian in a customized phoren product.
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Re: Kaveri & aero-engine discussion

Post by maitya »

Ok, so here it is ... a simplistic (yes, I must admit almost embarrassingly simplistic) side-by-side comparison of this so-called Kaver-with-M88-core, original Kaveri and “paper-injin” called “Improved Kaveri”.
(and no I can’t use Ganga, as it is copyrighted by Vinaji).

Image

Anyway, here are some interesting finds:

1) What would happen, if by some magic like Djinn-power or Modi-bear-hug-of-Philippe, Snecma/Safran decides to transfer the 3rd Gen SCBs for the Turbine blades (so higher TeT) or blisks for the HPC, and we are able to absorb it and employ it to Kabini?
Pls refer to the light-blue (calc for present Kaveri) and purple (calc for improved Kaveri) columns and compare them – you will notice, except for changing the OPR and the TeT (same as that M88 core) every other parameters, including BPR, has been kept same - and the calc comes out to be exactly similar/same for both.

Why?

Astonishingly, and there’s some amount of coincidence in this, the dry (73KN) and wet thrust (103KN) rating comes exactly same – so it proves, irrespective of the difference in BPR, if you are aiming for thrust augmentation, the material and manufacturing (and of course the CFD interplay) technology is what the Achilles heel is.
Pls further note, for a military engine thrust is the be-all-end-all type parameter (another is weight, but more on that later) – while for a civilian application SFC is critical, while thrust etc are secondary.
So BPR is not the aspect that drives improvement that we should be seeking for.

But let me contradict myself now …

Is BPR of no importance … actually it is.
Pls look closely to rows 25 – 28 towards the bottom of the table.

You will notice, the M88 with higher BPR, is a more efficient engine as in propulsive efficiency (interestingly Thermal efficiency remains same, but that’s another topic for another day), resulting in low SFC.
No surprises there as this is exactly what a civilian injin strives to achieve.

So even though BPR in itself doesn’t really change the Thrust rating etc, it’s an indicator of the maturity of the injin technology and of a better efficient turbofan injin.


2) Now let’s look at the M88-core-within-Kaveri calc (Red column) more closely and compare with current Kaveri (light blue column).
There are some drastic improvements almost all across – but the primary consideration is the thrust where you will notice some obscene increments like 30% in dry thrust (row 24).

But if you look closely, the bulk of that dry thrust increment % is coming because of an improved core (TeT and OPR – row 22) – that increment is 16%.
This the real value add and no, BPR, doesn’t really have any role to play in this.

However, the high BPR does have a say in the share of dry thrust from Fan alone – this is also significant on its own as it is more than double (row 23). But the point is the share of Core for a Kaveri-with-M88-core is till high at 77% (while that of Kaveri is 86%).


3) But this is a huge fallacy as well – if you look closely, the there’s 85% increase in the amount of work available (row 15) for their respective Fan (which results in accelerating the bypass air and creating thrust).

This kind of jump will not happen in the real-life world – as there’re mechanical limit upto which the existing Kaveri Fan would be able to withstand.
So end result would be de-rating of the energy available to the Fan to create the component of the dry thrust (~say around 30% increment etc) – this would take the total dry thrust available to be marginally more to say around 66KN etc

That is, compared to 61KN of the current Kaveri, about 17-18% increment in overall dry thrust.
Pls note, even this increment is nothing to scoff at – but still is not as significant as it appears here.

The real advantage obviously would be the Propulsive efficiency (row 26) and thus the SFC values (row 27) – which again shows dramatic increment of 31% etc.


Finally, a quick point on the SFC increment etc – something that I have always maintained applicable mostly to Civilian side.

Pls analyse super-cruise SFC requirements … people make the most common mistake of ignoring the high SFC requirement of super-cruise (yes SFC is not as high as that of Wet Thrust levels, but are still higher than a vanilla dry-thrust cut-off of 0.8M etc).
So basically, if you want a highly optimized turbofan and have super-cruise etc in immediate technology road-map etc, then these gen of engines are – but, if you struggling with your 1st ever turbofan attempt type scenarios, Kaveri is way forward of that league.

There are multiple other aspects that one can compare (in the calc excel above), but I'll stop here.
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Re: Kaveri & aero-engine discussion

Post by JayS »

^^ Hmm. The m88 core will not entertain any more flow than what it is designed to handle today. Highly unlikely. So core flow cannot change from 50kg/s.
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Re: Kaveri & aero-engine discussion

Post by Neela »

Zynda wrote:Sad to read that snippet from SJha about current status of jet dev in the country. So what GTRE is a failure lab? Few people I respect the most are aware of the fact that they have to "unlearn & relearn" many things constantly. Unlearning at a senior age can lead to an impression of being "wrong" & relearning can be interpreted as a sign of failure in Indian culture...

I dunno perhaps it is time to spin off GTRE in to a private entity (the best option would be to a collab wtih Scnema & Indian partner or partners) on the existing land/infra facility in BLR. They can retain many of the staff to start with but slowly restructure as needed. Of course the bulk of R&D money still would be expected to foot by the GoI until a workable product is ready...the further improvements for which will likely be funded by private entity. My onlee hope from the above is the ability to do good project management, bring in the right people at good compensation (something which is very hard to do in the current set up), retaining existing talent and importantly addition of needed infra resources. Even with all of the above, a state of the art product would be challenging. I am sure many of the above is already being done by the Chinese & they are struggling to get a reliable power plant.

Anyways, I think India is thinking along the lines of Israeli defence industry i.e. have good avionics, armament industry & many of the sub-systems be Indian in a customized phoren product.
My guess. Its too early to say the vote of thanks.
Three things which I believe this govt understands
- Defence indigenization
- TCO
- Long term perspective

Evidence is there for each of the above. I doubt if a critical component like jet engines would be left out.

In a recent Swarajya Mag articel, Baba kalyani said he is targetting a 1000 kg thrust Turboshaft engine for helis. Now a man like him understands investment, R&D and most importantly RoI. He wouldnt put his money unless he believes there is a market downstream & GoI is enabling a market for his products. I expect something revamped to happen for the military jet programme along with a 100+ seater civilian transport aircraft.


Im cautiously optimistic Ms.Sitharaman will deliver here too with a plan. Surely , surely the financials of engines ,price,service cost are already known to them. The reworked Rafale deal ( See AbhijitIyer Mitra's article ) show this govt is extracting every last bit. They know the importance and how it bleeds us. I hope.
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Re: Kaveri & aero-engine discussion

Post by NRao »

Neela wrote:Saurav Jha ( read from bottom to top )
$1 billion a year, for about 5 years. Do not see an alternative to that.

All engine Labs are a failure until they produce a certified engine.
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Re: Kaveri & aero-engine discussion

Post by VKumar »

In such critical areas we should have 2 teams working independently to produce solutions. There would be duplication of work as well as innovation. I know of instances where this approach was followed in software development for mission critical systems.
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Re: Kaveri & aero-engine discussion

Post by Indranil »

Two teams require two times the money. Here we are paying peanuts to one!
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Re: Kaveri & aero-engine discussion

Post by ramana »

JayS, Maitya said it better than I can
So even though BPR in itself doesn’t really change the Thrust rating etc, it’s an indicator of the maturity of the injin technology and of a better efficient turbofan injin.


Maitya, Thanks for the effort as you have done this for me!!!

Row 13 Compressor Exit Temp of 687 K vs 718K starts the story.

This leads to row 20 Engine Exit Velocity of 970 m/sec vs 1192 m/sec. IOW about Mach 0.67 shortage.

Row 23 Dry Thrust, Fan is consequence of BPR?

Row 22 Dry Thrust, Core is 49Kn which is slightly better than the M-88 core.

So if the fan can get slightly better Dry thrust say same as M-88 core about 14Kn, then dry thrust will be 63 KN.

By increasing BPR from 0.16 to higher xx ?
But wont this reduce already feeble core thrust as more will be used to drive the fan?


Why do they have Compressor 6 stages vs. 7 stages for the M-88 core and the dimensions are about same as the 404?

Or if they can add back the 7th stage for the HPC and bring the dry thrust, core to 56KN and keep the fan same they will get 56+8= 64KN.

Also tell me more about the Kaveri flat rated engine concept?

Flat rated to constant exhaust gas temperature like Pratt and Whitney?


here is vina's orginal Ganga post in this thread:

LINK

and N^3 immediately below that. The sad thing is these were made in 2009. Its almost 9 years after that and Kaveri is still a distant dream.

They wanted a new core.

So maitya what's the way forward?

Tejas needs an engine with the 414 level performance and dimensions.

Can the Kaveri-2 get there with a new core from scratch.

And will it fit in the Tejas or has to be re-sized?

Just like the ATAGS was better than Dhanush, similarly Kaveri -2 can be licked.
It needs a new HPC stage to bring up the thrust values.
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Re: Kaveri & aero-engine discussion

Post by ramana »

NRao, Just throwing money without understanding the real problem won't fix it.

GTRE did quite a good job for the 1st Turbofan designed and made in India.

Had they stuck to the extra HP stage and Tejas was not so heavy things would have been different.

BTW I never realized that Kaveri is really two iterations: -37 14UB and now-35 VS

GTRE should have had N^3 and Vina as program consultants.
And they would have achieved it by now.
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Re: Kaveri & aero-engine discussion

Post by Avtar Singh »

Indranil wrote:We will move the important parts to a sticky technical thread. But Sir, your request is quite bizzare. You are asking the mods to reduce discussion on this thread to fluff!!!

You have the option of not reading technical posts!
what I meant about by pass ratio is that it is just a parameter
it has no bearing on being able to make a jet engine

if you can make a jet engine ie the core, fan etc...
you can then go on to make a jet engine with whatever by pass ratio one requires.

The inability to make a jet engine revolves around other issues;
project management, materials science, etc. etc. blah blah bah.

will power, persistence, testing, no fear of failure
and even if failure occurs just doing it all again and again until it works.
of course throwing some money at the problem, in India, not handing it to foreigners helps

I imagine in India the paragraph above is where the problems lie.

I think in aviation producing FBW FCS and the jet engine have to be the 2 big challenges. The first was done ages ago under sanctions and being ejected from the usa.... With no crashes to date

The jet engine should not be beyond Indian scientists and engineers.

Failure failure failure, oh never mind lets just start over...
rinse and repeat the required number of times, ie until it works
the graveyard should be littered with hundreds of failed attempts if that is what it takes
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Re: Kaveri & aero-engine discussion

Post by ramana »

Avtar, I say there are two ways of looking at problems: strategic and tactical.
Strategic is also called global and looks at many factors that could be used to tackle the problem.
Tactical or military looks at the immediate root cause and tries to fix that.

And the big lapse is to mistake one for the other and use the wrong solution.

Kaveri despite all the global/strategic factors is really a tactical problem.

It does not develop the required dry thrust.
You fix that and you have a winner.
We have narrowed it down to the core.
Now what exactly in the core is being explored.
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Re: Kaveri & aero-engine discussion

Post by Rakesh »

Avtar, I agree with Ramana-ji. BRF's engine gurus are on to something. Let them work it out.

Let GTRE fix the tactical problem, so you and me can celebrate the strategic solution :)
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Re: Kaveri & aero-engine discussion

Post by Katare »

After a lot of matha-pachchi and head banging on jet engine technology over many years, which is mostly beyond comprehension of my brain anyhow, I have learned one thing that it's all about TET. If we can add another ~75C to Kaveri TET, we would get the thrust we need. Rest of the parameters can be tweaked and optimized iteratively but TET needs you to have Uber massa grade technology upfront - Single crystal blades/blisks, parts with intricate cooling vanes, thermal barrier coatings and exotic high temperature materials.
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Re: Kaveri & aero-engine discussion

Post by Katare »

Here is a graph showing linear relationship between inlet temperature and core power -

TET and core power
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Re: Kaveri & aero-engine discussion

Post by Haridas »

ramana wrote:GTRE should have had N^3 and Vina as program consultants.
And they would have achieved it by now.
I heard that Mangolia does not allow their Yaak herders alternative profession ;)
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Re: Kaveri & aero-engine discussion

Post by Avarachan »

Over the years, I have learned not to under-estimate India's national-security establishment. I wonder what is going on behind the scenes.

What is curious about the Kaveri project is that certain projects have received the necessary funding for the enabling infrastructure to be built (IGMDP, Arihant program). But the Kaveri project has not. All this talk of success and failure has to be seen in that context. I don't think any of us know what's really going on.
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Re: Kaveri & aero-engine discussion

Post by kittigadu »

The BPR sets the propulsion efficiency and the OPR the thermodynamic efficiency of the engine. Based on the characteristics posted, Kaveri does not compare well with M88 in both aspects. It’s SFC is likely to be worse.
The BPR is likely lower because the core is likely producing less specific thrust because of the low TUrbine inlet temperature, and is hence oversized. The turbine inlet temperature sets the specific thrust. I am assuming the 1850 k posted for turbine inlet temperature is at the inlet to the high pressure turbine nozzle. 1850 k translates to about 2870 F. Even this number is low compared to even modern commercial jet engines. At Steady state high power, for new engines, this number is around 3000 F, and goes up as the engine deteriorates. For military engines, the number will be higher.

There is no getting around this. Help is more readily available for the cold section/compressor, whether from Snecma or Rolls or GE or Pratt, hence the OPR can be fixed with help. However to increase the Turbine inlet temperature, single crystal nickel based alloys need to be developed. Nobody is going to give this technology. It has to be developed from scratch . Better cooling designs for combustor, nozzles, blades, and shrouds has to be developed. Nobody is going to give these either.

It is going to be a long haul.
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Re: Kaveri & aero-engine discussion

Post by jaysimha »

https://www.drdo.gov.in/drdo/drdojsp/do ... &p=RFI.pdf

GTRE was to Set up Twin Test Cell for developmental aero gas turbine engines upto 130kN thrust class

Dont know what is the status now??
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Re: Kaveri & aero-engine discussion

Post by JayS »

ramana wrote:JayS, Maitya said it better than I can
So even though BPR in itself doesn’t really change the Thrust rating etc, it’s an indicator of the maturity of the injin technology and of a better efficient turbofan injin.
It does and it does not. This is gross simplification. If your system requirement for propulsion unit dictates low BPR, you go for it, irrespective of what others might think of your technical capability. There is no universal truth saying high BPR = high efficiency across the whole spectrum of possible fighter jet propulsion. Its only valid in a certain conditions. Nor high efficiency is always a primary concern. In that sense, having low BPR or high BPR does not *always* indicate level of technical capability. The currently being worked on SST in US will need a low BPR turbofan for it, quite low compared to BPR of 15 that the next PW1000G engine will have. If GE makes an engine for SST with lower BPR, does that make GE in inferior OEM suddenly..??

Kaveri's BPR is out of flat rating requirement, not a forced result out of any technical capability gap. Similarly F119 has lower BPR than its other contemporaries, still it used to be epitome of technical capabilities in its hay days. Olympus engines from Concorde are perhaps the most efficient jet engines ever despite having BPR of 0. They can rival even the modern engines in terms of efficiency. BPR is not an issue with Kaveri. It would have achieved all its design goals had the other issues taken care of, especially with the A/B.

You can increase Kaveri's BPR, but then you will have to forgo flat rating, unless you increase its TET capability to today's state-of-the-art (well beyond the practical limits possible in 80s when Kaveri was conceived) and run it at reduced TET to maintain flat rating.
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Re: Kaveri & aero-engine discussion

Post by Neela »

Are we going in circles here ?
There is a new discussion.
Maitya brings in the excel sheet and explains the problem using numbers. This time ion BPR. 3 pages later it boils down to

- TET
- OPR

And Im reminded of that 1 Pinglish post from N^3.
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Re: Kaveri & aero-engine discussion

Post by JayS »

Neela wrote:Are we going in circles here ?
There is a new discussion.
Maitya brings in the excel sheet and explains the problem using numbers. This time ion BPR. 3 pages later it boils down to

- TET
- OPR

And Im reminded of that 1 Pinglish post from N^3.
When we are trying to invent non-existent problems, we are bound to go in circles, especially with no real information to cross check any of the hypotheses. That's why I do not want to speculate anymore. Everything that could be said, is already said multiple times.

Even with this M88 core for kaveri, is nothing new. If you open discussion from 2009 and 2012, I am pretty sure you will see exact same things discussed there.
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