Kaveri & Aero-Engine: News & Discussion

[pravula]

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.

[suryag]

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

[vina]

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.

[JayS]

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.

[Singha]

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.

[Singha]

from smallest to biggest , GE uses this for its work

[Singha]

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

[Singha]

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.

[Singha]

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.

[JayS]

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.

[Singha]

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

[JayS]

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.

[vina]

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.

[madhu]

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/defaul ... 102007.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.

[chetak]

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/defaul ... 102007.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??

[JayS]

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/defaul ... 102007.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.

[kit]

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

[JayS]

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).

[Rishi_Tri]

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.

[JayS]

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%.

[ramana]

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!

[ramana]

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?

[ramana]

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?

[ramana]

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.

[Zynda]

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.

[ramana]

Yes. Manik is Nirbhay power plant.

[ragupta]

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?

[JayS]

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.

[JayS]

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.

[ramana]

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

[Avarachan]

Live and learn.

True.

Would you never have found that anywhere else!

True again. I wouldn't have found this out if not for BRF. I'm very grateful for the education BRF has given me over the years.

[Avarachan]

I wish someone would make a list of the testing infrastructure India needs to reach the next level of economic-industrial development. That way, voters could be educated regarding this issue. Perhaps that information is too sensitive, though.

[madhu]

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.

JayS, i am not a CFD/thermal guy so i am struggling to embedding the 1D thermal coling equation. however i have found a shortcut which i believe is a good approximation. the chart is from Gas Turbine Performance By Philip P. Walsh, Paul Fletcher, gives cooling requirement vs TET. as per my calcualtion TET is 1500K so cooling required is just 5% as per the chart assuming high technology or 8% assuming low technology.

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

we can neglect it as of now i believe. more over now a days i think tapping from engine is not done. check the report of trent 1000

The Trent 1000 does not supply compressor air for airframe ventilation (Cabin Bleed), but does supply compressor air for the purpose of preventing ice build-up on the engine nacelle (Cowl Thermal Anti-Ice (CTAI)). The nacelle thermal anti-icing flow demand is modulated via a regulating valve

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

are you sure about it? i think the design point is at cruse condition rather than Static sea level, thats it. check out latest trent 1000 which is 345kN at takeoff vs 319kN Maximum Continuous. where as GE90 engine is 375kN at takeoff vs 69.200kN at cruise. this huge drop is due to the fact that it bleeds huge amount of air. (my understanding).

[madhu]

if you are using 1D cooling model let me know to what level you are cooling your blades to? i mean what is the metal temperature that you are setting to.
FYI in industrial GT i have seen blearing as high as 18~20% for cooling. not sure of aero.

[chetak]

On flat rating.
From wiki:

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

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

Just asking onlee.........


Is there some confusion between flat rating and de rating.

Wasn't the canberra engine derated very simply by mechanically restricting it's throttle movement to a preset value, well below the max possible setting??

Even the Artouste, as well as the Garrett are set up produce less power than they are actually capable of.

[chetak]

I wish someone would make a list of the testing infrastructure India needs to reach the next level of economic-industrial development. That way, voters could be educated regarding this issue. Perhaps that information is too sensitive, though.

OEM built engine test beds are plenty available in India with the IN, IAF as well as the PSUs.

Not very sure, but the marine version of the kaveri has probably run on one such test facility, after some minor tinkering and adaptation.

Various engines, from diverse design bureaux, are available for study, scrutiny and detailed strip examination at these places, just for the mere asking. Different design approaches and design solutions may be seen as well as appreciated.

Sometimes, Indians can be pigheaded about not exploiting fully, the resources available at home.

I know for sure that not enough conversation takes place between the Forces for the optimal exploitation of available resources as well as pooling of technical expertise because of office politics.

[vina]

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

Just asking onlee.........


Is there some confusion between flat rating and de rating.

Wasn't the canberra engine derated very simply by mechanically restricting it's throttle movement to a preset value, well below the max possible setting??

Even the Artouste, as well as the Garrett are set up produce less power than they are actually capable of.

De Rating vs flat rating in normal course, I suppose is a question of semantics, you can possibly override a derate , flat rating you cannot (it is done and dusted).

The Kaveri "flat rating" is a bit different. What they have done is put the design point for max TET at altitude performance (to compensate for the thrust lapse with altitude and for thrust lapse high stagnation temp at off design points at low altitude). It is accurately described as a TET Throttled engine. The trouble is while it has a high SPECIFIC thrust, it has low total thrust .This simply means that it doesn't have the Sea Level Static (SLS) Oomph to throw the plane down the runway and get it airborne and climb to altitude quickly. This part requires raw thrust and there is no substitute. This is where conventional engines designed at ISA conditions with higher bypass do great. They have great SLS Oomph and thrust drops with altitude and high stagnation conditions in more than even say 0.6 mach at low altitudes . But that is great for brochure publishing as well. It sounds great when you put out 90KN or 100KN on your brochure . Perfect in Europe or in Russia where temp is BELOW ISA for much of the year, but rubbish in our conditions. That is besides the point though.

Various engines, from diverse design bureaux, are available for study, scrutiny and detailed strip examination at these places, just for the mere asking. Different design approaches and design solutions may be seen as well as appreciated.

Sometimes, Indians can be pigheaded about not exploiting fully, the resources available at home.

I know for sure that not enough conversation takes place between the Forces for the optimal exploitation of available resources as well as pooling of technical expertise because of office politics

EXACTLY . When I post the possible "fix" for Kaveri, you will kick yourself , all your former colleagues , and all the Indian establishment and ask WTF didn't they think of this!

[JayS]

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.

JayS, i am not a CFD/thermal guy so i am struggling to embedding the 1D thermal coling equation. however i have found a shortcut which i believe is a good approximation. the chart is from Gas Turbine Performance By Philip P. Walsh, Paul Fletcher, gives cooling requirement vs TET. as per my calcualtion TET is 1500K so cooling required is just 5% as per the chart assuming high technology or 8% assuming low technology.

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

we can neglect it as of now i believe. more over now a days i think tapping from engine is not done. check the report of trent 1000

The Trent 1000 does not supply compressor air for airframe ventilation (Cabin Bleed), but does supply compressor air for the purpose of preventing ice build-up on the engine nacelle (Cowl Thermal Anti-Ice (CTAI)). The nacelle thermal anti-icing flow demand is modulated via a regulating valve

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

are you sure about it? i think the design point is at cruse condition rather than Static sea level, thats it. check out latest trent 1000 which is 345kN at takeoff vs 319kN Maximum Continuous. where as GE90 engine is 375kN at takeoff vs 69.200kN at cruise. this huge drop is due to the fact that it bleeds huge amount of air. (my understanding).

As per that plot you would need 7.5%+8.5% = 16% cooling air for HPT (rotor + stator). That's in the same ballpark as I told previously. For 1700k its well above 20%. Current engines easily reach 1900K. So you can see level of cooling air required by extrapolating. Technology level is a little vague word. You can have better cooling technology which would need more air for cooling. You could have better material technology which would need less air for cooling (but not by much perhaps, for example, going from DS to SCB blades only give you about 50K margin). You can use this chart to start with. Kaveri can be assumed to be on lower side of technology level.

The bleedless engine is from the "all electric" concept. But currently the industry is not reached to that level (its not really the technology that is stopping the change, its conservative mindset too and high costs of qualifying new technology sometimes). What we have in A350 XWB and B787 is "more electric". But there are really only a couple of engines out of tens which are going bleed-less. And they are going to use separate APU which is powered by the engine through electricity rather than compressed air. Fighters can't really afford to have so many components and don't really care about 1-2% gain in efficiency. Plus the requirement is tiny in fighters as compared to Airliner. Not worth having separate APU just for that. Anyhow mainstream engines like F404/F414/M88 are old designs by any standard. I don't know how its done in F35.


Flat rating in civil is not per se from altitude perspective its more for hot and hot/high ground performance (maintaining thrust levels across all the airports). But thermodynamically both are same. And do not expect that Mil jet would give same thrust as on ground at the cruising altitude. The flat rated altitude would be something like 6000-10000ft. I tried to ask this spec for Kaveri in AL-2017. They wouldn't tell me.

The huge drop in thrust is natural characteristic of Jet engine. Thrust drops with Altitude. At some altitude its goes so low that Aircraft cannot even sustain flight.

[chetak]

Just asking onlee.........


Is there some confusion between flat rating and de rating.

Wasn't the canberra engine derated very simply by mechanically restricting it's throttle movement to a preset value, well below the max possible setting??

Even the Artouste, as well as the Garrett are set up produce less power than they are actually capable of.

De Rating vs flat rating in normal course, I suppose is a question of semantics, you can possibly override a derate , flat rating you cannot (it is done and dusted).

The Kaveri "flat rating" is a bit different. What they have done is put the design point for max TET at altitude performance (to compensate for the thrust drop with altitude and for high stagnation temp at off design points at low altitude). It is accurately described as a TET Throttled engine. The trouble is while it has a high SPECIFIC thrust, it has low total thrust .This simply means that it doesn't have the Sea Level Static (SLS) Oomph to throw the plane down the runway and get it airborne and climb to altitude quickly. This part requires raw thrust and there is no substitute. This is where conventional engines designed at ISA conditions with higher bypass do great. They have great SLS Oomph and thrust drops with altitude and high stagnation conditions in more than even say 0.6 mach at low altitudes . But that is great for brochure publishing as well. It sounds great when you put out 90KN or 100KN on your brochure . Perfect in Europe or in Russia where temp is BELOW ISA for much of the year, but rubbish in our conditions. That is besides the point though.

Various engines, from diverse design bureaux, are available for study, scrutiny and detailed strip examination at these places, just for the mere asking. Different design approaches and design solutions may be seen as well as appreciated.

Sometimes, Indians can be pigheaded about not exploiting fully, the resources available at home.

I know for sure that not enough conversation takes place between the Forces for the optimal exploitation of available resources as well as pooling of technical expertise because of office politics

EXACTLY . When I post the possible "fix" for Kaveri, you will kick yourself , all your former colleagues , and all the Indian establishment and ask WTF didn't they think of this!

vina,

"kick yourself", "all your former colleagues", "all the Indian establishment"

You have this very peculiar and unhappy knack of sinking your own arguments. Besh!!

The "Indian establishment" is an amorphous entity, not given to dialogue, either within with itself (introspection) or with others. They are all masters of the turf war and winners/survivors are invariably put out to pasture, leaving the field barren and scorched.

Everyone within this entity ecosystem thinks that they are living at one end of the alimentary canal when actually, all of them are only capable of inhabiting the other end.

Sometimes, you make really very good points but dude, give a thought to the presentation, OK??

[JayS]

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

One sentence answer - The problem with Kaveri is that we are doing nothing to fix it.

The civil engines of today's edge are definitely more advanced than Kaveri from all perspectives. And Flat rating does help them in maintaining high life for hot components. So its win-win for them. Flat rating makes task difficult, yes. But not unachievable. For Kaveri, they almost achieved designed dry thrust. As I have been saying here all the while and Madhu confirmed from his conversation with GTRE ex-Chief, the shortfall is due to minor issues here and there. Look at the efficiency numbers for example for Kaveri modules - all at 85%. Whereas other engines like M88 or F404 have efficiencies touching 90%. State of the art engines such as F135 would have even higher efficiencies. For each % efficiency gain you get about ~1% gain in overall engine efficiency i.e. better sfc and better thrust. If GTRE can manage to improve a bit on all compressors and turbines' efifciencies by 1-2% they will be very close to the design dry thrust value. The loss in combustor is ~5%. Its ~3% for better engines. Combustion efficiency is 99.5%. It could be 99.99%. I don't know if they have things like Active tip gap control system to reduce secondary losses. GTRE's HPT cooling tech is bit lagging. And they do not have SCBs in HPT. Things like infusion of 3D aerodynamics would help. But they do not have 3D aero technology. (They couldn't have made everything under the Sun in 2000Cr funding, now, could they..? You don't get these things available in commercial CFD codes. These things are proprietary and take considerable time, efforts, test data and money to build). I had listed once some low hanging fruits for Kaveri improvements, IMO. Every small bit counts.

Since GTRE does not have funding and test facilities to actually try and fail and learn a lot of tricks of the trade, they need consultancy. We would rather throw goras dollah than giving the same amount to our own brown brothers. For last 4-5yrs nothing really is happening. GOI is pinning hopes on French for last 2yrs while nothing has come from that side yet. While they are not releasing money for K-10 and Flight test bed. They are not giving MiG29 to GTRE, they are not giving LCA airframe requested by GTRE for HSTT. They are literally doing nothing. Just expecting Snecma to come and fix everything one fine day. Even that deal is not signed in almost 2yrs now. Last year they were saying Kaveri will be flying in LCA in AI-19. One year is gone and nothing has happened. Nothing will happen in next one year as well.

After it was delinked from LCA project in like 2008 or so, they should have just focused on making Kaveri fly. Goal should have been to have a flying reliable engine whatever may be the T:W ratio or max thrust. If it was 100kg overweight, so be it. If it gives 10% less thrust so be it. Even now our aim should be only that. Side by side a parallel efforts could be made to improve performance, by leveraging academia/industry and other resources. But how will you make Kaveri flight worthy, if you do not have a damn aircraft to put the engine in..?

PS: Ramana Sir, check this table from the link. It shows technology levels for Jet engine. Compare the numbers with those from Madhu's excel sheet. You will get a rough idea where Kaveri stands overall. Flat rating add more challenge and demands better tech level than otherwise needed to achieve same thrust/SFC goals, and thus puts Kaveri at further disadvantage. As of now Kaveri is between level 2 and 3 from the table.
https://books.google.se/books?id=2Wy5rp ... &q&f=false