Kaveri & aero-engine discussion

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Re: Kaveri & aero-engine discussion

Postby madhu » 30 Mar 2018 23:02

chetak wrote:We need to look inward and honestly introspect.


Sir each technology have its own complexity but jet engine is more complex than nuclear technology. Imagine u need to maintain a candle flame while you are driving at 500kmph. Thatz what happens inside GT. The air is at 0.3~0.5 Mach and u need to sustain combustion. Temperature that turbine guide vane sees is 1900C where as the melting point of inco/Ti is around 1300~1500C yet u need to make it work without melting.

Topping all these we can buy jet engine off the shelf but we cant do the same for nuclear weapons. So politicians are reluctant to fund engine programs.

Please note we do not have IC engine still. Coz thats not priority so is jet engine for government.

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Re: Kaveri & aero-engine discussion

Postby Neshant » 30 Mar 2018 23:34

Modelling the vortices in jet engines

Supersonic jet physics is hellishly complicated, but Chinese researchers are making gains in understanding it. Andrew Masterson reports.

https://cosmosmagazine.com/physics/mode ... et-engines

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Re: Kaveri & aero-engine discussion

Postby chetak » 30 Mar 2018 23:54

madhu wrote:
chetak wrote:We need to look inward and honestly introspect.


Sir each technology have its own complexity but jet engine is more complex than nuclear technology. Imagine u need to maintain a candle flame while you are driving at 500kmph. Thatz what happens inside GT. The air is at 0.3~0.5 Mach and u need to sustain combustion. Temperature that turbine guide vane sees is 1900C where as the melting point of inco/Ti is around 1300~1500C yet u need to make it work without melting.

Topping all these we can buy jet engine off the shelf but we cant do the same for nuclear weapons. So politicians are reluctant to fund engine programs.

Please note we do not have IC engine still. Coz thats not priority so is jet engine for government.


madhu ji,

And we have also built nuclear subs, the most complex of all complex weapon systems, bar none.

why do some organizations succeed while some others do not, is still the key question, no??

BTW, thanks for the lesson on aero engines.

Over the long years, I have handled more aero engines/marine GTs, both military and civil and from varied sources, than you could probably shake a stick at. :)

I really hope that something worthwhile emerges from the Kaveri project. I understand that folks are really pulling out all the stops.

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Re: Kaveri & aero-engine discussion

Postby Indranil » 31 Mar 2018 00:13


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Re: Kaveri & aero-engine discussion

Postby Haridas » 31 Mar 2018 12:28

madhu wrote:
chetak wrote:We need to look inward and honestly introspect.


Sir each technology have its own complexity but jet engine is more complex than nuclear technology. Imagine u need to maintain a candle flame while you are driving at 500kmph. Thatz what happens inside GT. The air is at 0.3~0.5 Mach and u need to sustain combustion. Temperature that turbine guide vane sees is 1900C where as the melting point of inco/Ti is around 1300~1500C yet u need to make it work without melting.

Topping all these we can buy jet engine off the shelf but we cant do the same for nuclear weapons. So politicians are reluctant to fund engine programs.

Please note we do not have IC engine still. Coz thats not priority so is jet engine for government.

Speed may be 0.5 mach, but the temperature & pressure is also very high, so combustion rate is easy and good. So it's a metaphor.

Otoh Thermonuclear fusion is a more realistic comparision to lighting wet wood in typhoon with one dry matchstick.

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Re: Kaveri & aero-engine discussion

Postby hanumadu » 31 Mar 2018 13:41

chetak wrote:
hanumadu wrote:Using the Kaveri experience, how long will it take to develop a new engine with Kaveri specifications but without flat rating?



For the Kaveri, flat rating is the least of the problems.

If other performance and weight and life criteria are met, the customer would probably accept it.

Flat rating can come later.


From the discussion before, flat rating seems to be problem. The design decisions made for flat rating are making it difficult to achieve the required performance.

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Re: Kaveri & aero-engine discussion

Postby Neshant » 01 Apr 2018 04:15

Haridas wrote:Otoh Thermonuclear fusion is a more realistic comparision to lighting wet wood in typhoon with one dry matchstick.


Not to side tack the thread but basic fission nukes are 1940s technology. Fusion nukes are early 50s.

I would think it's a lot easier to build a fusion nuke than a high performance fighter jet engine.

It's also the reason passenger airliners have engines from just 3 global manufacturers - GE, Pratt & Whitney, Rolls Royce.

Although China will muscle in on that cartel soon enough.

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Re: Kaveri & aero-engine discussion

Postby pravula » 01 Apr 2018 07:12

Neshant wrote:
Haridas wrote:Otoh Thermonuclear fusion is a more realistic comparision to lighting wet wood in typhoon with one dry matchstick.


Not to side tack the thread but basic fission nukes are 1940s technology. Fusion nukes are early 50s.


And jet technology is which decade? 1920s?

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Re: Kaveri & aero-engine discussion

Postby Neshant » 01 Apr 2018 07:58

pravula wrote:And jet technology is which decade? 1920s?


Modern jet technology is way more advanced than when first invented.
It's well beyond producing a big bang.
A 70s nuke would provide just as much deterrence as a present day nuke.
It's mostly advances in the delivery system that has changed, not the nuke itself.

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Re: Kaveri & aero-engine discussion

Postby saumitra_j » 01 Apr 2018 07:59

hanumadu wrote:
chetak wrote:

For the Kaveri, flat rating is the least of the problems.

If other performance and weight and life criteria are met, the customer would probably accept it.

Flat rating can come later.


From the discussion before, flat rating seems to be problem. The design decisions made for flat rating are making it difficult to achieve the required performance.

Not sure about that - from what I understand, the biggest problems for Kaveri are timelines (it is already TOO late) and being overweight. Nobody among the powers that be are convinced that giving additional time to the program will result in something useful in meaningful time. Unfortunately, that is the perception and regardless of how much we talk about lack of testing facilities, lack of budget et al, this perception problem is difficult to solve IMHO. To give some perspective, as of AI 15, Kaveri had done just about 3K or 4k (don't recall the exact no) hours of ground run. It needed to do much more before it could move for a double engined aircraft for testing and a 1000 or so hours more before it was allowed on a single engine aircraft. The second problem is simply about materials - Kaveri is overweight - so even if the previous problem is solved, the materials problem will always result in less than required TWR. Given the operational requirements and need to develop technology, the GoI is doing its best through the Kaveri Snecma route - hopefully the Rafale deal will help address some of the infrastructure issues around GT development and the Kaveri Snecma venture will provide the right kind of experience and confidence to our institutions to develop a GT that will power our aircrafts!

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Re: Kaveri & aero-engine discussion

Postby pravula » 01 Apr 2018 08:10

Neshant wrote:
pravula wrote:And jet technology is which decade? 1920s?


Modern jet technology is way more advanced than when first invented.
It's well beyond producing a big bang.
A 70s nuke would provide just as much deterrence as a present day nuke.
It's mostly advances in the delivery system that has changed, not the nuke itself.


and a 70's engine will produce just as much thrust today I would think. so why need a "modern" jet engine?

OK, will stop being a smart-ass. Just as jet engines are increasingly more compact and reliable, the same applies to nukes, rocket engines etc. My issue was your classification that the concept was from a particular decade and therefore easy, done and dusted....thats not true. Look at regular IC engines in cars and trucks.

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Re: Kaveri & aero-engine discussion

Postby suryag » 01 Apr 2018 08:23

Folks - Please stay on topic, further non sequitur posts will be poofed

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Re: Kaveri & aero-engine discussion

Postby vina » 02 Apr 2018 12:06

JayS wrote:You actually limit TET from going to max on ground and lower altitudes to keep thrust artificially lower than what is possible. (that means lower fuel consumption to some extent but then you are forced to use lower BPR so some disadvantage there. Its complicated enough that we cannot make generic statement. One would need parametric analysis of the engine to see overall impact). What flat rating means is that you design the engine to give 54kN thrust at say 10000ft rather than designing it for 54kN on ground. (getting same thrust on ground is easier than at altitude, so in that sense its harder to design or overdesigned). So you are overdesigning the engine so it can still give same thrust at altitude that it gives at ground. Had Kaveri been designed without flat rating it would give 54kN thrust on ground and may be say 45kN at 10000ft altitude. Now it is designed to give 54kN at 10000ft and suppressed to keep it at 54kN on ground by limiting TET, when it could perhaps give 65kN on ground by removing limiter on the TET.

There are quite a bit of benefits of flat rating which make it a very attractive preposition - your fighter has much better thrust available at altitude. You can perhaps even supercruise. You have somewhat better life for HPT components since they run at lower than max temp on ground. You could perhaps even trade off some of the saving in life to hike max TET at altitude to extract slightly higher thrust. You can definitely do stuff and it gives a significant edge to your fighter. But then it also makes you work hard.

Do read the paper linked by Jaysimha above - it explains Flat rating concept used in Kaveri.


Yes. Yes. That paper posted really helped clear some of the misconceptions I had as well, the way GTRE has gone about it is different from how flat rating is usually done.

But that said, all this is Chai Biskoot . Bottomline. Do you have a solution ?

Believe me, there is a solution that will "liberate" the full performance of the Kaveri at SLS (Sea level Static) conditions (the Kaveri is a LARGE engine 78kg/s mass flow rate vs the others like GE 404 and M88 etc) where it has been throttled.

I actually emailed the DefExpo 2018 folks the following early last week.

Is there some way to include a topic in addition to the ones listed in the “Open Challenge Competition - Solution to Problem” DefExpo 2018 ?

The Kaveri Turbojet engine program for the Tejas fighter aircraft has not resulted in a useable product despite the best efforts over nearly 30 years and nearly Rs 2200 crores being spent on it. Though the Kaveri engine (from the DRDO published information) has been successfully flight tested in Russia, it is still not generate sufficient thrust to meet the requirements of the Tejas Fighter with the result being that Tejas flies with an imported
GE-F404-IN-20 series engine. The later versions of the Tejas ie (Mark 1A and Mark 2) too seem destined to have foreign engines.

You will agree that having our own domestic engine that can successfully meet all the current and growth requirements of the Tejas Fighter and future follow on programs that are proposed like the AMCA , will have a huge bearing on national security, and is strategically vital to insulating our national capabilities from any possible coercive sanction and denial regimes that they have been historically subject to.

I have a very easily implementable and well proven solution that will allow the existing Kaveri engine to fully satisfy the current and future growth requirements of the Tejas program and can with modifications and enhancement address the powering requirements of follow on programs such as the AMCA as well.

I would be much obliged if you could include an additional topic namely “ Enhancing The Thrust of an existing Flat Rated Turbojet Engine” in the “Open Challenge Competition” in the DefExpo 2018. Doing so would allow me to submit a possible solution to be considered for a strategically and economically vital national program which while nearly there in terms of a functioning engine, has not been able to cross the finish line in terms of thrust required.


Obviously, knowing how things work, I DONT expect to hear back from the DefExpo folks. But thats okay. I will send it across to a couple of folks who will possibly able to pass it on the right folks to look into it.

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 13:03

vina wrote:
But that said, all this is Chai Biskoot . Bottomline. Do you have a solution ?



I never really gave a thought this to be frank. But What kind of solution you are expecting..? One with which a small tinkering would unleash full potential of Kaveri on SL...? I don't believe there is one such quick fix which exists with a bit of thinking now. If you have one in mind, please share, if you feel like.

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 13:40

we badly need the kaveri flying, preferably in a IL76 pod or atleast in a su30
china has been flying the WS10 for 15 years now gathering data and improving things stepwise and still unable to match the GE404/CFM56 level of MTBF (early 1980s western tech) looking at their J20 woes.

we have not even scratched surface of new data and insights to be gathered by actually flying it regularly in all heights, speeds and weathers. if we had got it flying, that would give us better handle on whats to come next rather than blindly hope snecma will act in our best interests.

it remains a science project attached to a NAL wind tunnel at present, not a product remotely.

maybe there is something less bulky than IL76 and cheaper to operate that too will be fine....like a airbus a320 maybe...it can fly comfortably on one engine. or hang the kaveri in a separate pod inboard of the engine with a ballast weight inboard of the other.

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 13:45

Image

Image

from smallest to biggest , GE uses this for its work

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 13:47

P&W testing a engine for mitsubishi small jet using another approach

Image

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 13:48

we could easily get a 747 , 767 or A310 used off some boneyard in mojave or spain and start work.

even one of the older AI 747 would suffice.

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 13:52

sncema silvercrest business jet engine program

http://www.aero-news.net/index.cfm?do=m ... 1cfc2ba06a

The modified Gulfstream II flight test airplane arrived at Kelly and December 2, 2015. The 1970’s-era Gulfstream II was extensively modified for the SAFRAN/SNECMA Silvercrest test program, with custom-designed engine mounts and other hardware manufactured by SWAT’s sister company, Sierra Industries of Uvalde, Texas. In addition to engine mounting and structural modifications, the aircraft includes newly engineered electronic engine controls and a completely separate electrical and hydraulic system for the new engine. The project also included the design and installation of extensive in-flight monitoring and test equipment.

Image

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 15:01

Singha wrote:we badly need the kaveri flying, preferably in a IL76 pod or atleast in a su30
china has been flying the WS10 for 15 years now gathering data and improving things stepwise and still unable to match the GE404/CFM56 level of MTBF (early 1980s western tech) looking at their J20 woes.

we have not even scratched surface of new data and insights to be gathered by actually flying it regularly in all heights, speeds and weathers. if we had got it flying, that would give us better handle on whats to come next rather than blindly hope snecma will act in our best interests.

it remains a science project attached to a NAL wind tunnel at present, not a product remotely.

maybe there is something less bulky than IL76 and cheaper to operate that too will be fine....like a airbus a320 maybe...it can fly comfortably on one engine. or hang the kaveri in a separate pod inboard of the engine with a ballast weight inboard of the other.


The proposal to acquire flight test bed is biting dust in MoD for 3-4 years now at least.

Despite all efforts MiG-29 is not being made available for flight testing of Kaveri for past many years.

We could have got flying test bed based on B747 from Boeing under offset contracts from billions of $$ worth contracts we gave them. But we did not.

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Re: Kaveri & aero-engine discussion

Postby Singha » 02 Apr 2018 15:04

i suppose NAL/GTRE/ADA had some inputs into the offsets as it included a wind tunnel. wonder why we missed that trick.

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 15:09

Singha wrote:i suppose NAL/GTRE/ADA had some inputs into the offsets as it included a wind tunnel. wonder why we missed that trick.

We got a rusted junk in the name of WT. It feels almost as if someone do not want us to have flying testbed and they find easy co-conspirators within the power that be in India.

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Re: Kaveri & aero-engine discussion

Postby vina » 02 Apr 2018 18:29

JayS wrote:
vina wrote:
But that said, all this is Chai Biskoot . Bottomline. Do you have a solution ?



I never really gave a thought this to be frank. But What kind of solution you are expecting..? One with which a small tinkering would unleash full potential of Kaveri on SL...? I don't believe there is one such quick fix which exists with a bit of thinking now. If you have one in mind, please share, if you feel like.

It is a fix , "quick" or not is a matter of perception, but definitely far "quicker" and more "in your control" than waiting for new materials , which is like watching paint on the wall dry.. I will post about it later after I have written it up as a formal note and send it across to multiple folks out of which hopefully one will be bothered enough to do something about it.

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Re: Kaveri & aero-engine discussion

Postby madhu » 02 Apr 2018 18:43

JayS wrote:PS: Do remember that model used by Madhu is still not completely realistic. For example it does not account for Cooling air off take from HPC which can be as high as 30% of HPC output.

JayS, I see that the cooling are tapping is just 2%-3% max of 5% at design point.

https://www.easa.europa.eu/sites/default/files/dfu/EASA-TCDS-E.060_Rolls--Royce_plc_RB211_Trent_500_series_engines-01-26102007.pdf
this is for trent 500 engine and you can see

Maximum HP1 bleed (in percent of gas generator compressor flow)
This bleed decreases linearly between the values listed below for the switchover point and 1700 K TET
Normal Abnormal
At switchover 4.0% 4.6%
Up to 1700K TET 1.0% 2.0%
At Take-off 1.0% 2.0%

Maximum LP bleed (in percent of fan flow)
This bleed decreases linearly between the values listed below for 1130K TET and 1650K TET points.
a) Normal & Abnormal (one engine inoperative) operation
i) At low idle and up to 1130K TET 0.53%
ii) Above 1650K TET 0.25%
10.6 Maximum HP3 bleed (in percent of HPC inlet flow)
This bleed decreases liearly between the values listed below for the 1000K TET and 1600K TET points.
i) At low idle and up to 1000K TET 1.75%
ii) At 1600K TET and up to Take-off 1.50%


only issue is with customer bleed air as it is lost in the cycle and it could be high. but I am not sure we tap any for military aero-engines. because for Trent 1000 there is no customer bleed air even though it is designed for civil aircraft engine.

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Re: Kaveri & aero-engine discussion

Postby chetak » 02 Apr 2018 19:19

madhu wrote:
JayS wrote:PS: Do remember that model used by Madhu is still not completely realistic. For example it does not account for Cooling air off take from HPC which can be as high as 30% of HPC output.

JayS, I see that the cooling are tapping is just 2%-3% max of 5% at design point.

https://www.easa.europa.eu/sites/default/files/dfu/EASA-TCDS-E.060_Rolls--Royce_plc_RB211_Trent_500_series_engines-01-26102007.pdf
this is for trent 500 engine and you can see

Maximum HP1 bleed (in percent of gas generator compressor flow)
This bleed decreases linearly between the values listed below for the switchover point and 1700 K TET
Normal Abnormal
At switchover 4.0% 4.6%
Up to 1700K TET 1.0% 2.0%
At Take-off 1.0% 2.0%

Maximum LP bleed (in percent of fan flow)
This bleed decreases linearly between the values listed below for 1130K TET and 1650K TET points.
a) Normal & Abnormal (one engine inoperative) operation
i) At low idle and up to 1130K TET 0.53%
ii) Above 1650K TET 0.25%
10.6 Maximum HP3 bleed (in percent of HPC inlet flow)
This bleed decreases liearly between the values listed below for the 1000K TET and 1600K TET points.
i) At low idle and up to 1000K TET 1.75%
ii) At 1600K TET and up to Take-off 1.50%


only issue is with customer bleed air as it is lost in the cycle and it could be high. but I am not sure we tap any for military aero-engines. because for Trent 1000 there is no customer bleed air even though it is designed for civil aircraft engine.


In some military engines, isn't some bleed tapped for air conditioning??

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 19:55

madhu wrote:
JayS wrote:PS: Do remember that model used by Madhu is still not completely realistic. For example it does not account for Cooling air off take from HPC which can be as high as 30% of HPC output.

JayS, I see that the cooling are tapping is just 2%-3% max of 5% at design point.

https://www.easa.europa.eu/sites/default/files/dfu/EASA-TCDS-E.060_Rolls--Royce_plc_RB211_Trent_500_series_engines-01-26102007.pdf
this is for trent 500 engine and you can see

Maximum HP1 bleed (in percent of gas generator compressor flow)
This bleed decreases linearly between the values listed below for the switchover point and 1700 K TET
Normal Abnormal
At switchover 4.0% 4.6%
Up to 1700K TET 1.0% 2.0%
At Take-off 1.0% 2.0%

Maximum LP bleed (in percent of fan flow)
This bleed decreases linearly between the values listed below for 1130K TET and 1650K TET points.
a) Normal & Abnormal (one engine inoperative) operation
i) At low idle and up to 1130K TET 0.53%
ii) Above 1650K TET 0.25%
10.6 Maximum HP3 bleed (in percent of HPC inlet flow)
This bleed decreases liearly between the values listed below for the 1000K TET and 1600K TET points.
i) At low idle and up to 1000K TET 1.75%
ii) At 1600K TET and up to Take-off 1.50%


only issue is with customer bleed air as it is lost in the cycle and it could be high. but I am not sure we tap any for military aero-engines. because for Trent 1000 there is no customer bleed air even though it is designed for civil aircraft engine.


Madhu, this is customer bleed air, used for cabin A/C, pressurization et al. You will have to see engine test data to know about cooling air for HPT/LPT. The HPT blades operate at good 300-400K over its melting point. And the cooling air itself is at 750-900K. That's why quite a bit of air is needed for HPT cooling.

To get cooling air required, one would need simplified cooling model. This one is little tricky. That's NAL paper I gave you has some model in it for cooling. Did you try that one...?

I am writing the equations for the engine on my own from scratch. Once I am done with all of them, I will insert the cooling model. If I find a good model before you I'll let you know.

PS: Quick ref: http://citeseerx.ist.psu.edu/viewdoc/do ... 1&type=pdf
See table 1 in this, typical numbers for HPT cooling req shown.

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Re: Kaveri & aero-engine discussion

Postby kit » 02 Apr 2018 20:04

JayS wrote:
Singha wrote:i suppose NAL/GTRE/ADA had some inputs into the offsets as it included a wind tunnel. wonder why we missed that trick.

We got a rusted junk in the name of WT. It feels almost as if someone do not want us to have flying testbed and they find easy co-conspirators within the power that be in India.


more likely is that it was cheap and the babu s pushed it. The people who use the testbed would need to go to higher up in the food chain to educate / revisit the bids

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 20:07

vina wrote:
JayS wrote:
I never really gave a thought this to be frank. But What kind of solution you are expecting..? One with which a small tinkering would unleash full potential of Kaveri on SL...? I don't believe there is one such quick fix which exists with a bit of thinking now. If you have one in mind, please share, if you feel like.

It is a fix , "quick" or not is a matter of perception, but definitely far "quicker" and more "in your control" than waiting for new materials , which is like watching paint on the wall dry.. I will post about it later after I have written it up as a formal note and send it across to multiple folks out of which hopefully one will be bothered enough to do something about it.


I hope its something which would not need redesign of compressors (like removing FADEC limiter on TET at SL/lower altitudes).

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Re: Kaveri & aero-engine discussion

Postby Rishi_Tri » 02 Apr 2018 20:09

vina wrote:
JayS wrote:
I never really gave a thought this to be frank. But What kind of solution you are expecting..? One with which a small tinkering would unleash full potential of Kaveri on SL...? I don't believe there is one such quick fix which exists with a bit of thinking now. If you have one in mind, please share, if you feel like.

It is a fix , "quick" or not is a matter of perception, but definitely far "quicker" and more "in your control" than waiting for new materials , which is like watching paint on the wall dry.. I will post about it later after I have written it up as a formal note and send it across to multiple folks out of which hopefully one will be bothered enough to do something about it.


I am sure you know this, but do send it across directly to Nirmala Sitharaman, other important GOI / MOD Twitter handles. These ppl take time but they do read what is sent across and implement. Saying out of personal experience. Tks.

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 20:10

chetak wrote:
In some military engines, isn't some bleed tapped for air conditioning??


Little bit of air must be used for cockpit pressurization/air conditioning. But it would be very less, like <1%.

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 21:25

Vina, You got me curious.

So how is flat rating normally done?
What has GTRE done that is different?



I too wondered what's happening to the large mass flow but then I am not a jet engines guy.

All do we have example of flat rated military jet engines in the world?

Singha turn on your search radar!

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 21:42

JayS wrote:Folks, first of all, we do not know whether flat rating was imposed condition by ASQR or whether it was self-imposed goal by GTRE. Lets keep that in mind while commenting. I am personally only interested in knowing the rationale behind it as of now, not debating it.



I read the GTRE paper published in 1985. Most likely written in 1984. To me it looks like GTRE self imposed the Flat rating as a virtue on the new engine and sold the concept from a paper study.

If it was so easy how come all the new jet engines since 1985 don't have it?

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 21:48

Vina,
In Kaveri, is that 14 kg/sec extra mass flow being used to cool the turbine blades to maintain the temperature? Wont that add to the thrust?

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 21:52

On flat rating.
From wiki:

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

When an engine is Flat rated it means that an engine of high Horsepower rating is constrained to a lower horsepower rating. The engine output in this case will always remain the same, but when atmospheric conditions such as high temperatures and high altitude (Hot and High) reduce the power output of the engine it has more headroom before it falls below the limited maximum output. In some cases the total power output of an engine needs to be constrained because the airframe can only handle a certain force. This is the case with Gas Turbine engines. Flat rating allows airplanes to operate under more demanding conditions, without the need for extra structural strengthening due to higher peak power output of the engine.

For example, the Garrett AiResearch TPE-331-5 engine originally fitted on the Dornier 228 produces 715 horsepower (533 kW). If the outside air temperature is above 20 degrees Celsius, the airplane's maximum speed is reduced by approximately 10 knots (19 km/h), because hotter air is less dense and thus produces less pressure inside the turbine. The Dornier 228 can also be fitted with the Garrett AiResearch TPE-331-10 conversion of the -5 engine which produces 1,000 horsepower (750 kW) but is limited (Flat rated) to only 715. In this case the airplane will be able to maintain its top speed at temperatures above 30 degrees Celsius without the risk of exceeding the airplane's structural limits.

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Re: Kaveri & aero-engine discussion

Postby Zynda » 02 Apr 2018 22:18

It seems like Manik Engine is ready and DRDO is looking for Private Sector to undertake manufacturing activities. Huge development...

Wasn't Manik scheduled to go on Nirbhay as well to replace existing Russian engines? Also any recent news of Manik successful testing?

https://www.drdo.gov.in/drdo/whatsnew/gtre-engine.pdf
Gas Turbine Research Establishment, Bengaluru had undertaken the project to design and develop a 450 kgf thrust class Small Turbo Fan Engine
‘Manik’ for Unmanned Aerial Vehicle application.

GTRE intends to invite Expression of Interest (EOI) for Transfer of Technology (ToT) of ‘Manik’ Small Turbo Fan engine. Interested industries may
respond to the EOI.

EOI will be published shortly in the National dailies/DRDO Portal & DI2TM portal of DRDO website.

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 22:20

Yes. Manik is Nirbhay power plant.

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Re: Kaveri & aero-engine discussion

Postby ragupta » 02 Apr 2018 22:29

ramana wrote:On flat rating.
From wiki:

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

When an engine is Flat rated it means that an engine of high Horsepower rating is constrained to a lower horsepower rating. The engine output in this case will always remain the same, but when atmospheric conditions such as high temperatures and high altitude (Hot and High) reduce the power output of the engine it has more headroom before it falls below the limited maximum output. In some cases the total power output of an engine needs to be constrained because the airframe can only handle a certain force. This is the case with Gas Turbine engines. Flat rating allows airplanes to operate under more demanding conditions, without the need for extra structural strengthening due to higher peak power output of the engine.

For example, the Garrett AiResearch TPE-331-5 engine originally fitted on the Dornier 228 produces 715 horsepower (533 kW). If the outside air temperature is above 20 degrees Celsius, the airplane's maximum speed is reduced by approximately 10 knots (19 km/h), because hotter air is less dense and thus produces less pressure inside the turbine. The Dornier 228 can also be fitted with the Garrett AiResearch TPE-331-10 conversion of the -5 engine which produces 1,000 horsepower (750 kW) but is limited (Flat rated) to only 715. In this case the airplane will be able to maintain its top speed at temperatures above 30 degrees Celsius without the risk of exceeding the airplane's structural limits.


How is it done? can it be done by just controlling airflow/fuel or there is more to it?

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 23:17

ramana wrote:
JayS wrote:Folks, first of all, we do not know whether flat rating was imposed condition by ASQR or whether it was self-imposed goal by GTRE. Lets keep that in mind while commenting. I am personally only interested in knowing the rationale behind it as of now, not debating it.



I read the GTRE paper published in 1985. Most likely written in 1984. To me it looks like GTRE self imposed the Flat rating as a virtue on the new engine and sold the concept from a paper study.

If it was so easy how come all the new jet engines since 1985 don't have it?


FYI, most, if not all, civil jet engines are flat rated.

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Re: Kaveri & aero-engine discussion

Postby JayS » 02 Apr 2018 23:18

Zynda wrote:It seems like Manik Engine is ready and DRDO is looking for Private Sector to undertake manufacturing activities. Huge development...

Wasn't Manik scheduled to go on Nirbhay as well to replace existing Russian engines? Also any recent news of Manik successful testing?

https://www.drdo.gov.in/drdo/whatsnew/gtre-engine.pdf
Gas Turbine Research Establishment, Bengaluru had undertaken the project to design and develop a 450 kgf thrust class Small Turbo Fan Engine
‘Manik’ for Unmanned Aerial Vehicle application.

GTRE intends to invite Expression of Interest (EOI) for Transfer of Technology (ToT) of ‘Manik’ Small Turbo Fan engine. Interested industries may
respond to the EOI.

EOI will be published shortly in the National dailies/DRDO Portal & DI2TM portal of DRDO website.


Good news. However such thing was published for HTFE-25 like 3yrs ago. Nothing had been heard of it since. They need to show orders else no one would come forth.

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Re: Kaveri & aero-engine discussion

Postby ramana » 02 Apr 2018 23:35

JayS, If civil airlines jet engines are flat rated, then what's the problem with the Kaveri?
Is flat rating another red herring?


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