LCA Tejas: News and Discussions

Gyan · Post by **Gyan** » 12 May 2015 14:20

Respected engine Gurus Maitya, Vina, Indranil and in Mongolia Mr. Yak

A lil question.

Is they new Engine proposed by GTRE (~110-115 kn) similar in size to GE F414 i.e would it ever be drop in replacement in LCA or AMCA? Similarly is the 25kn tubojet/fan proposed by HAL a drop in replacement for Adour for say Hawks?

jayasimha · Post by **jayasimha** » 12 May 2015 16:02

The First Series Production Light Combat Aircraft (LCA) Tejas has been handed over to Chief of Air Staff by Raksha Mantri on 17th January 2015.

The following are some of the reasons for delay in completion of LCA project:

• Ab-initio development of the state-of-the-art technologies.

• Non-availability of trained / skilled manpower in the country.

• Non-availability of infrastructure / test facilities in the country.

• Unanticipated technical / technological complexities faced in structural design.

• Non-availability of critical components / equipment / materials and denial of technologies by the technologically advanced countries.

• Enhanced User’s requirements or change in specifications during development.

• Increase in the scope of work.

• Inadequate production facility at HAL.

Subsequent to achieving Initial Operational Clearance (IOC) status on 20th December 2013, Tejas series production has commenced. The first Squadron of 20 IOC standard aircraft is expected to be delivered by 2017-18. Efforts are underway to enhance the production capability.

This information was given by Defence Minister Shri Manohar Parrikar in a written reply to Shri Pankaj Bora in Rajya Sabha today.

UlanBatori · Post by **UlanBatori** » 12 May 2015 19:20

"dark/fascist" side

From 400% reliable sources: He used to come to every PhD thesis defenj, and sit in the front row. With his hearing aid prominently on display. About 5 minutes into the Defenj, or at some point thereafter, he was likely to very dramatically remove the hearing aid and snooze off. Finis for the Candidate.
If that is not terror I don't know what is.
Nobody said bad things about the other names I listed there either. The ones who might have any credibility are the survivors.
JPL tradition: Each spacecraft mission has a Principal Investigator. aka Project Manager. If the mission fails for ANY REASON, the PI gets fired. Period. Same deal as Archimedes. Concentrates the mind wonderfully. Some missions may not be known to fail until 15 saal baad, so the PI might be able to escape with a halo saying:

He was the PI of the XYZ Mission onlee yaar!

For the majority of yaks, the operative philosophy filters down, presumably. U r either a Jeenius. Or an Idiot. The default presumption is the latter, not the former.
I don't support these sorts of project management philosophies, I much prefer to allow the yaks some space to poo in the wrong place etc, but without that thrill of being on the edge, no such project can succeed or progress. It is not easy or natural stuff, after all. I mean, how can joo expect someone hu

even about samajh chaste pigreji even begin to comprehend the terror, hain?

ramana · Post by **ramana** » 12 May 2015 20:18

K Mehta wrote:Those talking about lack of SPJ have forgotten this news?
http://articles.economictimes.indiatime ... do-warfare
In addition to the Radar Warner, the EW suite, tested in Bengaluru, was also equipped with a jammer, which gives to the pilot an additional capability of nullifying the effect of detected radar threat by appropriate mode of jamming.
And also from here
http://m.thehindubusinessline.com/news/ ... 75592.ece/

J Manjula, Director DARE said "LCA is the first fighter aircraft of India fitted with a radar warner and jammer equipment. It has capability for both radar warning and jamming using a Unified EW Technology. Over the coming few months, ADA and DARE will be scheduling further sorties to evaluate the system in various signal scenarios".

So where did the lack of SPJ reports first come in recently?

All after the CAG report the thread needs to recover.
Anyway two madrasa graduates are reminiscing. Sit back and enjoy the conversation./

I will decode later.

Vina, I took the family in summer 1999 to see the madrasa. It still looked idyllic despite the heat!
Who was the uncleji on the good side? Maybe email me.

UlanBatori · Post by **UlanBatori** » 12 May 2015 21:15

Just to show you that Mongolian hooch is every bit as good as desi hooch, let me chew the cud on a dreamy project.

IMO, the main breakthrough in engine technology from the F-404 days to the present, is the counter-rotating turbomachine. These things were used in rocket turbopumps, and then in helicopter turboshaft engines (very small), and were proposed for the aft-fan Propfan in the '80s, and were used on propellers such as the Bear bomber. But ppl did not dare to put them on fighter engines because of the fear of resonances (just guessing, from reasons given on rejected proposals of the past).

The advantages of counter-rotating machines are several. Every conventional axial turbomachine stage has two parts: a Rotor that adds/removes work to/from the flow while making it swirl, and a Stator that slaps the flow back to being axial, while slowing down/ speeding up the flow by expansion/contraction of the passage available for the flow.

The point is: ONLY the rotor adds/ removes work. The stator is basically a guidevane/nozzle/diffuser. IOW, the rotor is like an engineer, the stator is like a manager. Deadweight.

In the counter-rotating stage, there is no stator. There are just two rotors spinning in opposite directions. So both rotors add (compressor) or remove (turbine) work. No wasted mass. The work per stage is doubled - or the rpm can go down for the same work. The length of the engine can be reduced significantly. So there is a dramatic increase in thrust to weight ratio. OTOH, you need two counter-rotating, co-axial shafts, or planetary gears, so it is not all sweetness and light. It is incredibly complex, and the design is no picnic. IOW, hard.

But now we know that it has been done, and it works on the F-135, and would have worked on the F-136.

So what? If I were running the show in desh, I might figure out how to make 2 or 3 F-404 injuns sort-of 'disappear'. I would take careful measurements. I would whip some underlings into shape and get them to design and build counter-rotating stages of approx. the right diameter. Test the heck out of them on the bench, and maybe put them on a truck and drive them over the NH-47 for a few hundred miles while operating. Keep at it until they can survive that.

Dismantle the turbomachine of one F-404. Extract the HIGHEST-PRESSURE stages of the compressor and turbine, and all the combustors. Replace the rest with the counter-rotating stages, making sure that the last rotor matches the hp compressor and hp turbine stages. Put the whole thing back together, and slowly start testing and refining the gizmo. Why hp compressor and turbine? because that is where the temperature is highest, and thermal stresses are worst. Avoids having to deal with the thermal materials problem for now.

See if this new F-404 derivative can be made to survive flight stresses. Then put it back in the LCA and start flight-testing it. See if a good net improvement has been attained in Thrust to Weight ratio.

In addition, I suspect that traditional engines need counter-torque at least for some part. How do they do this? Swirl the exhaust? Or do they get it from airplane rolling moment? In either case there is a penalty. Swirl energy in the exhaust is momentum lost, so decreased thrust. Rolling moment means a differential lift, and any lift has an induced drag penalty.

So the counter-rotating machine also saves drag or adds thrust. More T/W!

This change will not need any fuselage mods. There may be some extra space inside the engine - use it to stash something and keep chappatis warm. Whatever. OK, time to sit back and enjoy the nah-nah-nah-nah arguments.

Singha · Post by **Singha** » 12 May 2015 21:43

what to do sire about the lack of knowledge about the processes used to make those parts? Cheen has been tearing their hair out using the CFM56 core for two decades now and still not matched the AL31 MTBF let alone the GE414 or the uber F119/F136/EJ200 level.

I think we should take bold steps and a quantum leap to solve the Tejas speed problem. we need a big engine around which to wrap a minimal plane.
history shows us the way - the redoubtable Nord Griffon (drumroll)

http://vignette4.wikia.nocookie.net/air ... 0324183450

vina · Post by **vina** » 12 May 2015 21:44

Ulanbatori wrote:IMO, the main breakthrough in engine technology from the F-404 days to the present, is the counter-rotating turbomachine. These things were used in rocket turbopumps, and then in helicopter turboshaft engines (very small), and were proposed for the aft-fan Propfan in the '80s, and were used on propellers such as the Bear bomber. But ppl did not dare to put them on fighter engines because of the fear of resonances (just guessing, from reasons given on rejected proposals of the past).

Not true!. The best hooch of course is Scotch! Dont believe me ? Look up a very successful vimaan that can take off and land vertically, fly backwards and sideways, does all tricks like a Humming bird, goes back to 1960s, won wars, is still in service today and yes, was in service in Indian colors. I am talking about the Harrier and it's Pegasus engine, which has counter rotating stages!

So what? If I were running the show in desh, I might figure out how to make 2 or 3 F-404 injuns sort-of 'disappear'. I would take careful measurements. I would whip some underlings into shape and get them to design and build counter-rotating stages of approx. the right diameter. Test the heck out of them on the bench, and maybe put them on a truck and drive them over the NH-47 for a few hundred miles while operating. Keep at it until they can survive that.

Dismantle the turbomachine of one F-404. Extract the HIGHEST-PRESSURE stages of the compressor and turbine, and all the combustors. Replace the rest with the counter-rotating stages,

You dont need to "disappear" anything. You need to strip he engines of the retired IN harriers and get the engineering design of he bearing and lube system and stuff of the Pegasus and apply them to getting a desi contra rotating spool engine.

But then, remember, how much ever you do wizardy with rotating machinery, the key bottleneck in a Gas Turbine is the TET. Unless you have the materials that are competitive (ie erect while garam at 1750 to 1800 K), you will still not a competitive engine. Even in a contra rotating spool engine, you will need a few stator stages (far fewer than otherwise I grant it) and you probably have far fewer swirl losses out of the exhaust.

Trouble is, you need both. Cutting edge turbo machinery design and the materials to go with it. Yeah, GTRE didnt do a moon shot with the Kaveri , I grant it, in terms of a contra rotating spool, but they do seem to have a decent engine working. The bottleneck is now the materials . You need to use the boot to be applied at two places. Once at the backside of GTRE and the second on the backside of DMRL for the materials. And oh, the third and fourth on the backside of the Baboons to have a vacuum test facility to be built and procure a flying test bed!

Singha · Post by **Singha** » 12 May 2015 21:47

Cheen has deftly reused the A50 returned by israel after the phalcon deal fell through as its flying engine tb.

Karan M · Post by **Karan M** » 12 May 2015 22:10

The IAF wants the best of everything and per classical theory. Good luck selling them the Nord Griffon or any such thing, and good luck getting the funding through the Indian system with a babu(n) sitting on every funding allocation.

neerajb · Post by **neerajb** » 12 May 2015 22:21

Gurulog, I think we are getting confused here. Couter-rotating spools are fine, but we don't have any counter-rotating stage engines in production?

Cheers....

ramana · Post by **ramana** » 12 May 2015 23:26

vina, Thanks for the info.

UlanBatori · Post by **UlanBatori** » 13 May 2015 00:18

vinaji:
The hooch in downtown Bataar was diluted with yak-biss today so no, there was no error in my bost onlee. The Harrier had counter-rotating SPOOLS for the LP and HP turbomachines, this is how they cancelled the torque/ gyroscopic whatever on the injun.

4 the gentle postor hu asked the difference: Counter-rotating Spools means, the low-pressure compressor is connected to the low-pressure turbine using a Leftist shaft, while the high-pressure compressor is connected to the high-pressure turbine using the outer Rightist shaft. They rotate in opposite directions. But fixed to the casing of the injun is a row of blades constituting the stator stages, for each row of rotor blades.

The counter-rotating STAGE has no stator blades at all. Just alternating rotor wheels that rotate in opposite directions.

So vinaji is right in that they used counter-rotating shafts in the Pegasus, but only the F-135 and F-136 use the counter-rotating stages as far as I know, among large fighter engines. Helicopter engines such as T-800 (?) may have counter-rotating stages, I remember wandering in some exhibition hall and wondering about that.

But Open Sesame! The Counter-Rotating Stage was invented by Ancient Indians onlee!!! To be precise, Defense R&D in India. Must be cousins of RAA. Which is why they have kept it secret all these years as a Secret Weapon for the Kaveri Engine. Promptly stolen by the unscrupulous Westerners.

A Study of Aerodynamic Performance of a Contra-Rotating Axial Compressor Stage

D.S. Pundhir, P.B. Sharma, Dept. of ME, IITD, Defence Science Journal, Vol 42, No. 3, July 1992, pp 191-19.
Misphortunately, this paper does no bragging about the vast superiority of an ENGINE that uses these stages. That's the trouble with these Mechanical Engineers: they must have thought it was for a Mark III air conditioner and the RAA wouldn't tell them otherwise.

The authors are indebted to lIT, New Delhi, for providing the facilities and also to the Aeronautics Research & Development Board, Ministry of Defence, for the provision of funds.

UlanBatori · Post by **UlanBatori** » 13 May 2015 00:26

Pls see picture 1 - all the blades are oriented the same way, so they can't be counter-rotating.

UlanBatori · Post by **UlanBatori** » 13 May 2015 01:38

Compare that to this Patent.

Diagram is too large on post inline

As it turns out, I do not believe that the pictures on the web showing "Abbroved phor Public Releej Onlee" F-135 or F-136 injin cutaways are the real things: I can't figure out how those can be counter-rotating blade angles unless they are using true djinn technology, though the general layout is approx. correct.

The mechanism shown in the Patent is basically one where the "stator cowling" itself spins in the opposite direction. Simple. But look at the branched blade roots of the other rotor! Does that mean blisks that are actually conical?? Pretty intricate.

Vinaji: Read ur point about the 'TET"again bliss. We call it Tee Eye Tee (Eye phor Inlet) but cannot write the acronym here because of sharam sharam

This is why I say, retain the last stage of the HP comp and the first stage of the HP turbine from the F404. And the combustor. Before you enter that comp stage, and after you exit that first turbine stage, the temperatures and pressures are much lower. So you avoid all metal-allergy issues.

Surely the rest of the turbomachine can be built in Bannerghatta MotorCycle Works with Kaveri metal-allergy onlee. Then they can put the machine together and spin it up, no need to wait for vacuum chamber etc. The combustor pressure is going to be as high as it was on F-404, so there is no danger of flameout - so why the vacuum chamber?

For the rest, put the injun under a wing of an Antonov and take it as high as that will go, to test performance.

It just takes initiative and persistence. Note that they have had the ability to draw the velocity diagrams and do turbine-compressor matching on counter-rotating turbomachines at least since 1992!!!!! What excuse is there for the present state of affairs, hain?

UlanBatori · Post by **UlanBatori** » 13 May 2015 04:24

And now for the P&W Patent(s): I am not sure how this is different from the GE Patent(s) but fortunately I am not in the Batent Bijnej. Look at the date!

A turbomachine comprises a flow duct with coaxially arranged radially inner and outer endwalls, first and second sets of axially spaced rotor stages arranged between the inner and outer endwalls, and a plurality of variable endwall segments arranged along the inner endwall. The first set of rotor stages rotates in a first direction, and the second set rotates in a second direction. The first and second sets alternate in axial series along the flow duct, such that axially adjacent rotor stages rotate in different directions. The variable endwall segments are radially positionable, in order to regulate loading on the first and second sets of rotor stages by changing a cross-sectional flow area between the inner and outer endwalls.

The invention claimed is:
1. A turbomachine comprising:
a flow duct comprising coaxially arranged radially inner and outer endwalls;
a first set of axially spaced rotor stages arranged between the inner and outer endwalls, each of the first set of rotor stages rotating in a first direction;
a second set of axially spaced rotor stages arranged between the inner and outer endwalls, each of the second set of rotor stages rotating in a second direction;
wherein the first and second sets of rotor stages alternate in axial series, such that axially adjacent rotor stages rotate in different directions; and
a set of variable endwall segments arranged along the inner endwall of the flow duct, wherein the variable endwall segments are radially positionable to regulate loading on the first and second sets of rotor stages by changing a flow area between the inner and outer endwalls.
2. The turbomachine of claim 1, further comprising an inner spool coupled to each of the first set of rotor stages in a radially inner region, the inner spool co-rotating with the first set of rotor stages.
3. The turbomachine of claim 2, further comprising an outer spool arranged coaxially about the inner spool and coupled to each of the second set of rotor stages in a radially outer region, the outer spool counter-rotating with the second set of rotor stages.
4. The turbomachine of claim 2, further comprising platform gear mechanisms coupling the inner spool to each of the second set of rotor stages in a radially inner platform region, such that the second set of rotor stages counter-rotate about the inner spool.
5. The turbomachine of claim 4, wherein the platform gear mechanisms are configured to counter-rotate the second set of rotor stages at different speeds about the inner spool.
6. The turbomachine of claim 1, wherein the first and second set of rotor stages form a compressor section and a turbine section in axial series along the flow duct.
7. The turbomachine of claim 6, wherein the first and second pluralities of rotor stages alternate in an axially adjacent series in each of the compressor section and the turbine section, such that axially adjacent compressor rotor stages rotate in different directions and axially adjacent turbine rotor stages alternate in different directions.
8. The turbomachine of claim 7, further comprising an inner spool coupling a compressor rotor stage in the first set of rotor stages to a turbine rotor stage in the first set of rotor stages, such that the compressor rotor stage co-rotates with the turbine rotor stage.
9. The turbomachine of claim 7, further comprising inter-row gear mechanisms coupling the first set of rotor stages to the second set of rotor stages, such that axially adjacent compressor and turbine rotor stages rotate in opposite directions.
10. The turbomachine of claim 7, further comprising inter-row gear mechanisms coupling the first set of rotor stages to the second set of rotor stages in the turbine section, such that the axially adjacent turbine rotor stages rotate in opposite directions.
11. The turbomachine of claim 1, further comprising blade tip gear mechanisms coupling the second set of rotor stages to a stationary casing, the stationary casing arranged coaxially about the first and second pluralities of turbine rotor stages.
12. The turbomachine of claim 1, wherein the variable endwall segments comprise n-shaped members having two radial legs and an axial surface, the axial surfaces of the n-shaped members being positionable in the radial direction to increase or decrease the flow area.
13. The turbomachine of claim 1, wherein the variable endwall segments comprise t-shaped members having a radial leg and an axial surface, the axial surfaces of the t-shaped members being positionable in the radial direction to increase or decrease the flow area.
14. The turbomachine of claim 1, wherein the variable endwall segments comprise arcuate elements forming a disc-shaped variable inner endwall, the variable inner endwall being positionable in the radial direction to increase or decrease the flow area.
15. The turbomachine of claim 1, further comprising radial slots formed in airfoil components of the first set of rotor stages, the variable endwall segments being positionable in the radial direction along the radial slots.
16. An engine comprising:
a flow duct comprising an inner flow boundary arranged about an axis and an outer flow boundary coaxially arranged about the inner flow boundary;
a compressor section comprising co-rotating compressor rotor stages interspersed with counter-rotating compressor rotor stages in series along the axis of the flow duct, wherein axially adjacent compressor rotor stages rotate in opposite directions about the axis;
a turbine section comprising co-rotating turbine rotor stages interspersed with counter-rotating turbine rotor stages in series along the axis of the flow duct, wherein axially adjacent turbine rotor stages rotate in opposite directions about the axis; and
a variable inner endwall comprising inner endwall segments, each of the inner endwall segments being radially positionable to regulate loading in the compressor and turbine sections by changing a flow area between the variable inner endwall and the outer flow boundary.
17. The engine of claim 16, further comprising a co-rotating spool coupling the co-rotating compressor rotor stages to the co-rotating turbine rotor stages.
18. The engine of claim 17, further comprising a counter-rotating spool coupling the counter-rotating compressor rotor stages to the counter-rotating turbine rotor stages.
19. The engine of claim 17, further comprising gear mechanisms coupling the co-rotating spool to the counter-rotating compressor and turbine rotor stages, such that the counter-rotating compressor and turbine rotor stages counter-rotate about the co-rotating spool.
20. The engine of claim 16, further comprising gear mechanisms coupling the co-rotating compressor and turbine rotor stages to the counter-rotating compressor and turbine rotor stages, such that the axially adjacent compressor and turbine rotor stages rotate in opposite directions.
21. A gas turbine engine comprising:
a flow duct;
a compressor section comprising a plurality of co-rotating compressor rotor stages interspersed with a plurality of counter-rotating compressor rotor stages, such that axially adjacent compressor rotor stages rotate in opposite directions; and
a turbine section comprising a plurality of co-rotating turbine rotor stages interspersed with a plurality of counter-rotating turbine rotor stages, such that axially adjacent turbine rotor stages rotate in opposite directions;
a variable inner endwall comprising a plurality of inner endwall segments circumferentially arranged about an inner diameter of the flow duct, wherein the inner endwall segments are positionable in a radial direction to regulate loading on the compressor and turbine sections by changing a cross-sectional area of the flow duct.
22. The gas turbine engine of claim 21, further comprising a spool coupling the co-rotating compressor rotor stages to the co-rotating turbine rotor stages.
23. The gas turbine engine of claim 22, further comprising gearing mechanisms coupling the spool to the counter-rotating compressor and turbine rotor stages, such that the counter-rotating compressor and turbine rotor stages counter-rotate about the spool.
24. The gas turbine engine of claim 21, further comprising a propulsion rotor coupled to the compressor section.
25. The gas turbine engine of claim 24, further comprising radial slots in airfoil members of the counter-rotating turbine rotor stages, wherein the inner endwall segments are positionable in the radial direction along the radial slots to control loading on the propulsion rotor.

Shreeman · Post by **Shreeman** » 13 May 2015 04:55

Eye know a thing or two about batents (Also, Mongolia too owns what three? batents). They serve 2 porpoises:

1. To soo.
2. To not be soo-ed.

Contents of batents are aj meaningless as the thought bhor the day on a toilet paper sheet. They look gud to the VeeSees though . Ah, I sea you have a sau batents, therephore you must know the takniki.
Claims are where law pattles are faught, desCription ij why claims can be made to be retrakted. In jernail, it is all of this here "rounded rektangle" is nou batented variety. Another prochure. Never aktually having wurked in that bhorm.

Also Indian batenting /= rest of the wurld batenting. And that is about the best thing there is about all of indiya.

Praktically espeaking, no batent ij going to eshtop you from making anything in indiya, for indiyan uje if yu know the takniki.

UlanBatori · Post by **UlanBatori** » 13 May 2015 05:45

Precisely true. No one in any dephenj establishment or univerjity is going to be stopped by Batents. The former because they are making stuff on a life-or-death basis, and the latter because they are supposed to learn anyway. Point I am making is that all this stuff is out there on one-click access basis. No secret about it, no ITAR, no Sanctions.

A high-school in India can use it to make a counter-rotating turbomachine model (not that it will spin 10,000 rpm, but to show that it can be built). Undergrad assignments can work out the velocity diagrams of every stage and link them up with a program, and keep playing until they have the whole performance curves. So why can't Indian 'professional establishments' develop a few experimental engines and test them?

2 years of dedicated efforts and there will be enough new stuff to go patent if they want, or to have a working testbeds to develop everything else. Build the blades with twisted flat plates or sliced pipes for Impulse Turbine stages, if they don't know anything else! But whatever it is , build something.

Shreeman · Post by **Shreeman** » 13 May 2015 06:02

^^^ Stop propojing ejjukcashun. It ij not cool. Childrens dont want to learn anymoar.Also you can buy a turbomashine model (may be not the counter rotating part) which showj all theje things and may even do a few thousand RPM. Also you can 3D print most parts if you only want a LED show.

Gyan · Post by **Gyan** » 13 May 2015 07:34

Mongolian Yak keeping talking about hard work and green pastures to departments which are hardly working & no real budgets.

Indranil · Post by **Indranil** » 13 May 2015 08:11

Moderator note: Everybody get back to English

maitya · Post by **maitya** » 13 May 2015 08:37

UlanBatori wrote: <snip>
The advantages of counter-rotating machines are several. Every conventional axial turbomachine stage has two parts: a Rotor that adds/removes work to/from the flow while making it swirl, and a Stator that slaps the flow back to being axial, while slowing down/ speeding up the flow by expansion/contraction of the passage available for the flow.

The point is: ONLY the rotor adds/ removes work. The stator is basically a guidevane/nozzle/diffuser. IOW, the rotor is like an engineer, the stator is like a manager. Deadweight.

In the counter-rotating stage, there is no stator. There are just two rotors spinning in opposite directions. So both rotors add (compressor) or remove (turbine) work. No wasted mass. The work per stage is doubled - or the rpm can go down for the same work. The length of the engine can be reduced significantly. So there is a dramatic increase in thrust to weight ratio. OTOH, you need two counter-rotating, co-axial shafts, or planetary gears, so it is not all sweetness and light. It is incredibly complex, and the design is no picnic. IOW, hard.
<snip>

Saar, we have discussed this (and it's potential impact etc) in the past as well ... here [Contra-Rotating Rotors and the Kaveri perspective]
Between I did post a few "bookish" velocity triangles there-in as well.

Ofcourse you did respond back immediately - especially on the secondary losses - here

What didn't get discussed then, just how all these will get fabricated and tested etc - given our tech base etc.
I see you are responding (as radical as you had always have been - a trademark - so shishyas like us, can draw sustenance from them) to that here:

UlanBatori wrote:Dismantle the turbomachine of one F-404. Extract the HIGHEST-PRESSURE stages of the compressor and turbine, and all the combustors. Replace the rest with the counter-rotating stages, making sure that the last rotor matches the hp compressor and hp turbine stages. Put the whole thing back together, and slowly start testing and refining the gizmo. Why hp compressor and turbine? because that is where the temperature is highest, and thermal stresses are worst. Avoids having to deal with the thermal materials problem for now.

And as always, I got confused - again.

Why touch the Turbine ... in a two stage design, just how much weight saving etc are we going to have by getting rid of a single turbine stator?

I mean, the achilees heel is with the weight of the compressor phases - and of coursse the SPR of the compressor stages. Granted the SPRs will go up, if properly designed and CALIBRATED, counter-rotating compressor stages (plus of course, no stator no dead-weight etc)
One more thing, in a counter-rotating stage setup, do we still need the compressor blade tips to "braze" the walls - IOW, will spillage (from the earlier stage) be any relevance anymore, as you are basically introducing turbulence anyway. If not, another headache (and top dollahs) saved/gone.

Just let the HPT and LPT be just the traditional way they are .... I mean with approx ~1780K TeT, the HPT and LPT discs are already a challenge to fabricate (IIRC they had to import the HPT disc) - and bringing in counter-rotating-spool et, the disc-sppol interfacing will become another challenge.
(Note: GTRE folks got shocked to find their HPT blades were accepting a few more tens of deg C of TeT than they orginally estimated - which of course they gleefully accepted, only to find their HPT disc gave up because of this temp increase - so they imported it from USA, not sure if it has got indigenously replaced now) etc

Plij to edjucate saar ...

[Added Later:] Contrary to popular belief, the turbofan metallurgical holy grail is not HPT blades (they are close second)... it's the HPT vanes, mainly due to it's large shroud, wide chord and of course complex geometry - all requiring DS casting (LPT Vanes are equiaxed, as the temp drop across HPT stage is big enough for the equiaxed vanes to survive in a LPT stage).

vina · Post by **vina** » 13 May 2015 09:30

UlanBatori wrote: counter-rotating SPOOLS for the LP and HP turbomachines, ...
The counter-rotating STAGE ..

Oh. Sorry. I didn't read your post carefully enough. I thought you were talking of the former. Now I see what you mean.

but only the F-135 and F-136 use the counter-rotating stages as far as I know, among large fighter engines.

Are you sure that they have what you are talking about and NOT something similar to the Pegasus ? I thought that it was like the latter.

'TET"again bliss. We call it Tee Eye Tee (Eye phor Inlet) but cannot write the acronym here because of sharam sharam This is why I say, retain the last stage of the HP comp and the first stage of the HP turbine from the F404. And the combustor. Before you enter that comp stage, and after you exit that first turbine stage, the temperatures and pressures are much lower. So you avoid all metal-allergy issues.

Surely the rest of the turbomachine can be built in Bannerghatta MotorCycle Works with Kaveri metal-allergy onlee. Then they can put the machine together and spin it up, no need to wait for vacuum chamber etc. The combustor pressure is going to be as high as it was on F-404, so there is no danger of flameout - so why the vacuum chamber?

Oh.. I was thinking of Turbine Yentry onree, can't put the Y there either, coz that will be sharm sharm too. But coming to the point. What you say will surely increase the t:w ratio of the engine. Nothing to sneeze at of course, if you manage to shave off some 300Kg off a 1000 kg engine, brilliant , in fact, and if you get efficiency gains too, purrfect.

But however,note that it won't change the overall thermodynamics of the engine. As long as you are Braying to Brayton Babu and Carnot Babu as ideal limits (you are talking of heat engines), your engine will still not be competitive in terms of pressure ratio and efficiency (your heat addition will be at lower avg temp) directly impacting thrust and fuel burn.

Like I said, you need everything. Not just one of the other. You need both. The best turbo machinery and the best thermodynamics. My understanding of the engine development (looking purely from YumBeeYea giri and Strat-e-jee giri) is that the efficiency gains came from continuous improvements in turbine materials (higher temp) , better high fatigue life and lower weight innovations (like blisks etc) and the really new path breaking stuff since the original P&W innovation of twin spool was the geared turbofan.

If what you are saying has happened in F135 (contra rotating stage), that would be a quantum jump indeed. I am not sure if that has happened, given the highly crusty and conservative nature of the business (has to be, you can't have engines going Paki and doing soosai with passengers on board)

member_20292 · Post by **member_20292** » 13 May 2015 10:03

vina wrote:
Trouble is, you need both. Cutting edge turbo machinery design and the materials to go with it. Yeah, GTRE didnt do a moon shot with the Kaveri , I grant it, in terms of a contra rotating spool, but they do seem to have a decent engine working. The bottleneck is now the materials . You need to use the boot to be applied at two places. Once at the backside of GTRE and the second on the backside of DMRL for the materials. And oh, the third and fourth on the backside of the Baboons to have a vacuum test facility to be built and procure a flying test bed!

1. oh Yeah. In MatSci its very easy peasy to raise the thermo-mechanical characteristics of these materials.

2. Whats the state of affairs in Indian universities a regards cutting edge matsci? It lags western universities by a lot. There is less incentive to produce the very best research, especially since the funding agencies, led by the DST are far more liberal in the disbursal of funds these days - and the rules are simply to publish reams and reams of papers, regardless of quality. Ultimately, engineering is a market led field - Newton etc. were all considered to be doctors in philosophy - until the industrial revolution came along and led to the a rise in demand of engineers who specialized in specific fields.

3. In Massa, commercialization of the research that you do, is far easier. I personally know of a professor who used to come in a Lotus Elise to take lectures - he'd gotten rich off the patents he sold to the Oil n Gas industry.

Net net, my point is that making rules easier for Profs to do whatever the hell they want and that includes making money, while being tenured in Indian universities. This will force them to produce to the tune of the market, which will allow them to do whatever is cutting edge AND makes money. This feeds into the defense programs as much as the defense programs feed into civilian science.

Market forces leading innovation beats giving DST grants to Professors and funded research - which will always be more of a MNREGA .

So yeah, Indian VCs, and Indian Gas Turbine Engine companies (are there any?) and Indian airplane manufacturers (

) should ideally drive these thrusts .

Indian rocket companies? Indian aircraft companies? Seems like the US is going to be ahead of India for a long long time, simply because of the straightforward freedoms their system allows them !

UlanBatori · Post by **UlanBatori** » 13 May 2015 17:26

Djinn *poof*

ramana · Post by **ramana** » 13 May 2015 20:02

Shreeman and others, You don't have UB's compulsions to use pingrezi.

So please desist.
Only UB and Vina may use it.
Thanks,
ramana

UB and Vina carry on.

ramana · Post by **ramana** » 13 May 2015 20:05

deejay et al.
How big is Sulur?
Is it the home base for LCAs?
Is the plan o host the conversion unit there?

deejay · Post by **deejay** » 13 May 2015 21:04

ramana wrote:deejay et al.
How big is Sulur?
Is it the home base for LCAs?
Is the plan o host the conversion unit there?

Sulur is full size AFS with adequate runway length. It used to house the 109 Helicopter Unit and the Sarang helicopter formation team. 109 has moved to accommodate the Tejas Sqn. I met the Sarang folks at AI2015 and they said no one is moving them away. One Su 30 Sqn may also move to Sulur, I've read sometime 2016.

Second Tejas sqn may come up at Tuticorin.

Sulur, I think also houses the No 5 BRD.

As far as conversion unit is concerned - it is all talk now, nothing is confirmed.

ramana · Post by **ramana** » 13 May 2015 22:28

Deejay, Thanks.

As PRC moves West, IAF needs to move South.

Cosmo_R · Post by **Cosmo_R** » 14 May 2015 03:53

Arun Menon wrote:Doesn't anyone speak English anymore? Whats with the crazy talk? I thought all that was restricted to the burkha threads.

Ssh We're going 'native' Bhonetics

. It conveys idioms, allusions and creates the nuance missing from everyday Internet English speak.

vina · Post by **vina** » 14 May 2015 05:02

UlanBatori wrote: the outside casing,They attach the 'stator' vanes to a separate rotating shroud inside the main casing, ..
BMW* ingineers ...
Weight saving will have to be carefully accounted - planetary gears etc a....... hub-mounted blade trees,

Ah.. The bicchars you bosted had two dejynes. The pehla like you said ghumata hua burkha-e-shroud-e-Turin , the second with individually ghumata ishtages with platenary giyars.

If I remember history correct, the pehla axial flow injin from Bannerghatta Moteren Werke oph James Von Pond 004,in unneees chao chalees thereabouts had the stator plades susbended phrom the casing, hajaar vibration praablem like a Paki doing raakit mard after getting kicked by a gadha and solushun was hub mounted after roping in the besht viprashun eggspurts in the whole of the theesra reich (who had pretty much founded and put the field on a modern footing)

So, given that a more paractical, less risky approach might be the doosra tareeka in your picchar. Yes. Maybe like everyone in IT/VITY says "modular" , on the likes of pick a Paki and drop in a Paki, a naya kamprejjor (start with YellPee maybe ) alone with indivijually ghumata ishtajes can be dropped in. And notice, this does not need turbines going ulta-pulta, so much less risk and tinkering and work needed in garam sections.

Also weight will be less in doosra. You don't need a mota shroud-e-turin , that is a shell structure, ghumata, bhaari and prone to vibrashun. Just a few extra gearing on the centerline shaft.

Added later.. I can see why old wizened mullahs with red hennaed beards would have screamed haraam ! rejonnce ! if you had put in a probosal for 1st tareeka.

ISRO now knows how to keep gas generators running with cryogenic to stoichiometric H2-O2, for what? 10 minutes at a time? in the jee ess ell vee. That is 3000 C, maybe 150,000 rpm, high pressure ratio? OK, the stages may be centrifugal, but I think the materials problems have been solved, based on that announcement.

Ah, but no. Raakit Yinjin pre-purner/ pindi chana generators naat run stoichiometric. They run phyul rich or praan hawa rich. Roosi ones latter, Yanqui ones phormer. ISRO's current one must be Roosi type onree (topa maar much of design). So not same-same as combustion chamber temps. But yes. You do have a point on GT turbine plades, which too are not stoichiometric my any means.

Wasalaam

UlanBatori · Post by **UlanBatori** » 14 May 2015 05:45

Djinn vijited.

UlanBatori · Post by **UlanBatori** » 14 May 2015 06:44

Shut Sesame!

vina · Post by **vina** » 14 May 2015 06:52

Done.. Djinn can disappear.

member_28108 · Post by **member_28108** » 14 May 2015 06:58

I think this pinglish vinglish thing is enough on the LCA thread.Is OK in those secluded threads.Frankly hard to read in a technical thread. Please stop it and Mods I feel that everyone should stop and there should be no exclusions.

saumitra_j · Post by **saumitra_j** » 14 May 2015 07:08

Folks,

IIRC, the current Kaveri had achieved about 3500 hours of ground run (in Feb) - target was to achieve 4000 hours before they could go to a twin engine platform for flight tests (i.e. most probably a Mig 29) and then complete another 1000 hours on that to achieve a total of 5000 hours before being put on a single engined aircraft. I do not think GTRE is going to deviate from this path - they are very close to achieving a complete ground up development of a reasonably modern aero engine and TBH, they must complete it first. From what I understand, they are still using DS blades and all talk of using TFTA Single Crystal blades is at least 5 years away. This is based on a conversation which I had with a GTRE scientist at AI 15 in Feb so TIFIW... While I love the approach the Yak herder and Vina ji are proposing, I think it should be done by a separate team with separate funding ... GTRE MUST be allowed to finish what they have started with because what they are producing (even with older technology) will still prove to be economically very useful given that we are still importing gas turbines in almost every field.

PS: As per the scientist I spoke to, the Kaveri was producing the designed thrust (both dry and in reheat) with a 3% variation which was apparently within acceptable range.

UlanBatori · Post by **UlanBatori** » 14 May 2015 07:09

Excuse me: WHY must one read stuff that one can't understand anyway, please?

UlanBatori · Post by **UlanBatori** » 14 May 2015 07:20

saumitra_j wrote:Folks,
I do not think GTRE is going to deviate from this path - they are very close to achieving a complete ground up development of a reasonably modern aero engine and TBH, they must complete it first. From what I understand, they are still using DS blades and all talk of using TFTA Single Crystal blades is at least 5 years away. This is based on a conversation which I had with a GTRE scientist at AI 15 in Feb so TIFIW... While I love the approach the Yak herder and Vina ji are proposing, I think it should be done by a separate team with separate funding ... GTRE MUST be allowed to finish what they have started with because what they are producing (even with older technology) will still prove to be economically very useful given that we are still importing gas turbines in almost every field.
PS: As per the scientist I spoke to, the Kaveri was producing the designed thrust (both dry and in reheat) with a 3% variation which was apparently within acceptable range.

Saumitraji, no argument there, we would (all) like to see the Kaveri engine succeed, but from what we read, it appears that the path ends in a brick wall per NaMo-diktat, does it not? So we have nothing against GTRE marching on ahead, but I think India needs a bit more in the engines field than what GTRE has been achieving. Including leadership.

Meanwhile the LCA is under constant attack as being underpowered, underperforming, while all the glitzy F-xx and Gri*** and Ra*** are touted as sooooo superior and attractive. And there seems to be no serious prospect of putting a Kaveri which "meets specs" into an operational LCA. Which is the reason for exploring some alternatives that might provide a breakthrough path. Can you believe that India's frontline INDIGENOUS fighter cannot operate without foreign-supplied engines? What if the Americans stick in a little code to make the F404 engine flameout if the GPS coordinates show over Pakistan or China, or POK or Aksai Chin or Arunachal? What if F-404 parts suddenly become unavailable, as happened with predecessor American systems in 1965, 1971, and 1998?

The notion of sticking c-r stages into a torn-up F-404 (as outrageous as it is) was introduced to counter the

nah-nah-nah-nah

generated when I suggested the possibility of bringing a more powerful engine into the LCA - that would have required a slight expansion of the fuselage, which was deemed to be on par with inventing a mission to explore Jupiter.

IIRC, the Kaveri has been "close to within 3% of meeting all specs" since 1977 when there was a gleaming mockup in a glass case in the lobby. Is it any closer? And to what spec? 1965-vintage? I think it was started as a War-Phooting National Urgency Project when the Egyptians backed out of the promise to develop a Non-Aligned Engine for the Non-Aligned 400% India-genious Hindustan Fighter HF-24, designed under the famous gora designer Kurt Tank. Ultra-modern, revolutionary AXIAL TURBOMACHINE, way ahead of the SOA in 1958. Karman Ogive nose. Sears-Haack minimum-wave-drag fuselage with Area Ruling. Still is. Ahead of the SOA of 1958, I mean.

The HF-24 Supersonic Fighter then went to 2 huge, slow British-supplied, License-manufactured centrifugal-turbomachine engines, apparently, instead of the one Kaveri which was supposed to power it. Which left no scope for maneuvering, and the Mach 2 fuselage was able to go up all the way to Mach 0.6 in a shallow dive. To allow it to take off, they used RATO (Rocket Assisted Take Off). Even then, on the first takeoff run, the plane refused to climb. The brave test pilot, heroically trying to save the money poured in by the starving Indian taxpayer of the 1960s (India was a famine nation then) refused to eject, but tried his best to lift it. Hit a sand dune off the end of the runway, crashed and died.

IIRC, in the 1971 war this super-supersonic fighter was used exclusively as a bomber, escorted by Gnats and MiGs for protection. Even then, several were shot down.

All the time, they were DEVELOPING the Kaveri. Close to meeting specs. Any day now.. when they return from coffee break.

Problem is, who cares any more? If time stood still or went backwards for the next 20 years, maybe... but otherwise I see a serious problem that basically means that India will be at the mercy of foreign engine-suppliers for the next 3000 IAF aircraft - of all types. LCA, MRCA, everything. Bottom line: You folks want your taxes to keep pouring out towards generously funding the entities that develop new weapons for the PAF, and Delhi real estate, well... their stocks are going up

and the Indian rupee is getting cheaper all the time. Dawood Ibrahim would be so pleased. Let's stay away from anything that requires thought and effort. Bhavitavyam Bhavet Eva!

I'll ask again: How many of those super-duper Kaveri Engineers that you know, can do a 1-D thermodynamic and gas dynamic flowpath analysis of the Kaveri Engine, let alone any other engine? With a calculator? What do they mean by "3 percent variation"? Thrust fluctuation due to compressor or combustor instability? (that would shake the plane to pieces). Polytropic efficiency? Sea level static thrust? TSFC? Mean time between failures? or 10-minutes continuous operation at max thrust with afterburner without flameout at the specified LCA ceiling, or blowing up?

UlanBatori · Post by **UlanBatori** » 14 May 2015 08:02

I ~~will tell~~ (have told) you part of what I have seen. OT.

member_28108 · Post by **member_28108** » 14 May 2015 08:14

UlanBatori wrote: Excuse me: WHY must one read stuff that one can't understand anyway, please?

Are you assuming everyone else is a dunce other than you? This is unacceptable.

UlanBatori · Post by **UlanBatori** » 14 May 2015 08:16