Kaveri & Aero-Engine: News & Discussion

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SaiK
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Re: Kaveri & aero-engine discussion

Postby SaiK » 15 Feb 2018 20:15

The tougher aspect to achive are in the precision domain.

- blades and TET
- compression spools and dry thrust
- BPR (although not difficult to design) & flat rating

Reg: BPR. We have more air volumes to heat up.. the larger to heat up, larger is the inefficiency. Lesser is the BPR, higher is the thrust and burn (ignoring other params). But heck.. the requirement is a mil jet.. hence it must focus more achieving thrust than efficiency (if a trade off is the argument)

The optimal BPR is trade secret worth GTRE itself.

So far.

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Re: Kaveri & aero-engine discussion

Postby Rakesh » 15 Feb 2018 23:58

https://twitter.com/SJha1618/status/964074994564255744 --> TASL is saying that they are in talks with GE to see if they can manufacture up to 75% of the components of the F-404 family that powers Tejas variants. However, GE will not transfer tech for the core.

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Re: Kaveri & aero-engine discussion

Postby Cybaru » 16 Feb 2018 01:09

Even that is great! TASL can provide components to Kaveri88 when it goes into production.

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Re: Kaveri & aero-engine discussion

Postby ramana » 16 Feb 2018 01:30

I guess in same manner HAL is in talk with SAFRAN for Kaveri-M88.

There is no short cut to this low BPR core handicap.

Need to spend money to get there.

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Re: Kaveri & aero-engine discussion

Postby ramana » 16 Feb 2018 01:31

Or tell GE to setup 100% F404 mfg facility in Bengluru.None of this screwdrivegiri.

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Re: Kaveri & aero-engine discussion

Postby SaiK » 16 Feb 2018 03:45

Well, screwdrivergiri in turbine-precision space is something we need to excel. IMHO, we should not even discuss about #ToT in BRF. Please considering to ban the tot word. It ain't logical nor sane to beg.

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Re: Kaveri & aero-engine discussion

Postby Haridas » 16 Feb 2018 08:23

Rakesh wrote:
Haridas wrote:No one asked
1. What is the typical maximum BPR for modern combat jet designs?
2. How BPR impacts vehicle's max speed at low, medium and high altitude?
3. What is the max BPR Tejas can take for Mk1, 1A and 2?

Will lead into interesting intake design discussion, if only yak herder stops collecting dung in such cold arctic weather :wink:

Haridas-ji: Might I humbly suggest that you take the lead in aero engine discussion? We all on BRF can learn so much!

To start off, can you please advise on the questions you posed above?

Rakesh ji, Have to apologize as I am on BR Forums for timepass only. I don't have time nor energy to lead anything, not that I have much competence in even few subject matters. Please tolerate me.

The questions that I asked however are hint/guidance for seekers on worthwhile pursuit for better understanding.

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Re: Kaveri & aero-engine discussion

Postby Avtar Singh » 17 Feb 2018 01:50

Bypass Ratio...

see here

https://en.wikipedia.org/wiki/Bypass_ratio

The engines on airliners (turbofans) have a high bypass ratio, most if not all of the thrust is derived from the bypass air produced by the fan blades. Very economical over long hours of operation at subsonic speed. The main job for the hot core is to drive the big fan.

At lower speeds/altitudes is the turbo propeller (turboprop) where a small jet drives a big 4 bladed propeller.... Eg c130 which cruises at 300kts

As more airspeed (mach .78/.80/.85) and range (000s nm, which needs higher altitudes to reduce fuel burn) is required. A large propeller becomes very in-efficient. So the large propeller morphs into the large fan and the hot core gets bigger than on a turbojet to drive said fan.

The bypass air is not as much as on a turboprop (must be 90%) but the multi blade fan allows high altitude (30,000 ft+) and subsonic speeds which a 4 bladed propeller could not achieve.... Ask an aerodynamist to explain.

So when one is sitting there at 35000ft, say M0.85 the main fan will have rotor speed of 85% N1 (N1 representing the speed of the big fan)

and N2 represents the speed of the core on a separate gauge. RR engines also have N3 since they have triple shafts. The only manufacturer to do so.


So if one was to close the thrust levers to idle which would give an N1 of around 40%. And then suddenly demand max power by pushing the throttles fully forward......

The fuel has to pumped into the core, this has to come up to speed and start producing thrust which hits the turbine in the back of the core. This turbine then has to spool up and being connected to the fan at the front via a shaft the big fan at the front starts to spool up ie N1 increases and finally you will get the thrust you demanded 10 minutes ago (sarcasm).

High altitude and lower air density does not help the whole spool up process.

Not suitable for fighter operations one may say... But very economical over long ranges at subsonic speed. These big fans produce huge amounts of thrust for very low (relatively) fuel burns. 100,000 lbs now.

So as faster response is required and thrust in a smaller package the bypass ratio decreases and the fan at the front gets smaller and smaller until you end with a turbojet and no big fan at the front.

All the thrust now comes from the hot section (exhaust gases) and there is no bypass air... reheat can be added.

The ultimate expression would be a rocket motor... no bypass air, no air full stop. No turbines.. Pump fuel in = instant thrust, masses of thrust but also masses of fuel burn but one would not get very far before running out of juice.

As with everything it is a compromise for the required purpose.

Hope this helps.

https://en.wikipedia.org/wiki/Airbreathing_jet_engine

https://aviation.stackexchange.com/ques ... -n1-and-n2

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Re: Kaveri & aero-engine discussion

Postby ramana » 17 Feb 2018 02:42

Avatar using all that knowledge please comment on Kaveri design.
Specifically look at why it is not achieving the afterburner thrust.

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Re: Kaveri & aero-engine discussion

Postby Indranil » 17 Feb 2018 03:20

Ramana sir, afterburner is not related to any of the above discussion!

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Re: Kaveri & aero-engine discussion

Postby ramana » 17 Feb 2018 03:21

Ok. What should be discussed? lets make sure we don't get sidetracked. Thanks, r

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Re: Kaveri & aero-engine discussion

Postby Indranil » 17 Feb 2018 03:58

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

Postby Eric Leiderman » 17 Feb 2018 09:35

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

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Re: Kaveri & aero-engine discussion

Postby ramana » 17 Feb 2018 10:27

Eric Leiderman wrote:https://www.reuters.com/article/us-ge-divestiture-exclusive/exclusive-ge-exploring-industrial-gas-engine-business-sale-sources-idUSKCN1G100D

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.

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Re: Kaveri & aero-engine discussion

Postby maitya » 19 Feb 2018 10:37

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

Postby Indranil » 19 Feb 2018 11:28

Use imgur for pictures. Message me if you have difficulties.

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Re: Kaveri & aero-engine discussion

Postby Haridas » 19 Feb 2018 12:33

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

Postby NRao » 19 Feb 2018 14:53

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

Postby Avtar Singh » 19 Feb 2018 22:02

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

Postby Indranil » 19 Feb 2018 22:25

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!

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Re: Kaveri & aero-engine discussion

Postby ramana » 19 Feb 2018 22:38

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

Postby maitya » 20 Feb 2018 00:29

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

Postby ramana » 20 Feb 2018 01:33

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

Postby Neela » 20 Feb 2018 01:35

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

Postby ramana » 20 Feb 2018 04:26

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

Postby Philip » 20 Feb 2018 05:11

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

Postby Neela » 20 Feb 2018 15:12

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

Postby sum » 20 Feb 2018 15:57

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

Postby JayS » 20 Feb 2018 17:07

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

Postby Zynda » 20 Feb 2018 17:26

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

Postby maitya » 20 Feb 2018 17:27

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

Postby JayS » 20 Feb 2018 18:11

^^ 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

Postby Neela » 20 Feb 2018 18:53

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

Postby NRao » 20 Feb 2018 18:58

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

Postby VKumar » 20 Feb 2018 22:50

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

Postby Indranil » 20 Feb 2018 23:20

Two teams require two times the money. Here we are paying peanuts to one!

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Re: Kaveri & aero-engine discussion

Postby ramana » 21 Feb 2018 00:42

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

Postby ramana » 21 Feb 2018 00:46

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

Postby Avtar Singh » 21 Feb 2018 02:39

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

Postby ramana » 21 Feb 2018 02:56

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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