Kaveri Engine

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
It is a varable cyle engine with full FADEC has low bpr and is flat rated.
Variable cycle? That is a joke. The american is struggling to get their variable cycle engine (the real one) ready for their future 6th generation fighter, Indian had decided to equip their LCA with such an advanced engine 30 years ago?

How many chinese turbofans are VCEs?
Only one. But the difference is: the super kaveri is still sitting on the ground while Chinese VCE is already flying.
 

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
Variable cycle? That is a joke. The american is struggling to get their variable cycle engine (the real one) ready for their future 6th generation fighter, Indian had decided to equip their LCA with such an advanced engine 30 years ago?
VCEs as a concept has existed long since the 70s.

Kaveri engine has been specifically designed for Indian environment. The engine is a variable cycle-flat-rated engine in which the thrust drop due to high ambient, forward speed is well compensated by the increased turbine entry temperature at the spool Kabini altitude test speed. This concept has been already demonstrated with high temperature and pressure condition in DRDO's High Mach Facility.

https://www.drdo.gov.in/drdo/pub/techfocus/aug2000/Kaveri.htm

Only one. But the difference is: the super kaveri is still sitting on the ground while Chinese VCE is already flying.
Funnily enough, you think US can't do it but China can.
Pray tell which chinese engine is that.
 
Last edited:

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
VCEs as a concept has existed long since the 70s.

Kaveri engine has been specifically designed for Indian environment. The engine is a variable cycle-flat-rated engine in which the thrust drop due to high ambient, forward speed is well compensated by the increased turbine entry temperature at the spool Kabini altitude test speed. This concept has been already demonstrated with high temperature and pressure condition in DRDO's High Mach Facility.

https://www.drdo.gov.in/drdo/pub/techfocus/aug2000/Kaveri.htm
https://www.drdo.gov.in/drdo/pub/techfocus/aug2000/Kaveri.htm


That is why I called the "variable cycle" concept in Kaveri is a big joke because it is a unique India claim - "changing the volume of air flow" (every turbofan engine seems to be capable of that but only DRDO calls it "variable cycle". When other countries talking about "variable cycle", they are talking about how to switch engine working model between "turbojet" and "turbofan".


Funnily enough, you think US can't do it but China can.
Pray tell which chinese engine is that.
We are talking about Kaveri and Chinese engine here. Last time I check, Kaveri is made by India not USA.
 

joy_tilak

Regular Member
Joined
Jul 22, 2010
Messages
22
Likes
25
Country flag
That is why I called the "variable cycle" concept in Kaveri is a big joke because it is a unique India claim - "changing the volume of air flow" (every turbofan engine seems to be capable of that but only DRDO calls it "variable cycle". When other countries talking about "variable cycle", they are talking about how to switch engine working model between "turbojet" and "turbofan".
Exactly ! Kaveri is not a VCE according to western standards.
 

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
That is why I called the "variable cycle" concept in Kaveri is a big joke because it is a unique India claim - "changing the volume of air flow" (every turbofan engine seems to be capable of that but only DRDO calls it "variable cycle". When other countries talking about "variable cycle", they are talking about how to switch engine working model between "turbojet" and "turbofan".
Oh boy, here comes the comedy.

Where in the article I posted does it state "changing the volume of air flow"?
Why don't you lie through your teeth more, it'll save some of that superiority complex from shattering.

Technically there's some manipulation of the airflow to get the desired results but that's not what variable cycle engines are.

What you are referring to switching between turbofan and turbojet is just VCEs functioning in varying air speeds sub, trans and supersonic with efficiency.
The earliest example of a VCE would be the YF120 where the airflow entry through the core at high temperatures would engage the desired turbojet cycle of the YF120.
Which is what the drdo article said and which you chose to misinterpret;
"which the thrust drop due to high ambient, forward speed is well compensated by the increased turbine entry temperature at the spool Kabini altitude test speed".

Taking off or initial climb is where Kaveri's turbojet cycle would come in.

Just so you know the GTX-37-14U which was tested years ago was the turbojet variant of the current GTX-35 Kaveri.

We are talking about Kaveri and Chinese engine here. Last time I check, Kaveri is made by India not USA.

What bloody chinese turbofan is a VCE, please enlighten us?
 

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
Oh boy, here comes the comedy.

Where in the article I posted does it state "changing the volume of air flow"?
Why don't you lie through your teeth more, it'll save some of that superiority complex from shattering.

Technically there's some manipulation of the airflow to get the desired results but that's not what variable cycle engines are.

What you are referring to switching between turbofan and turbojet is just VCEs functioning in varying air speeds sub, trans and supersonic with efficiency.
The earliest example of a VCE would be the YF120 where the airflow entry through the core at high temperatures would engage the desired turbojet cycle of the YF120.
Which is what the drdo article said and which you chose to misinterpret;
"which the thrust drop due to high ambient, forward speed is well compensated by the increased turbine entry temperature at the spool Kabini altitude test speed".

Taking off or initial climb is where Kaveri's turbojet cycle would come in.

Just so you know the GTX-37-14U which was tested years ago was the turbojet variant of the current GTX-35 Kaveri.
Who tells you that is veriable cycle? that is typical flat-rate function which by the way is nothing new.
The increased the turbine entry temperature is to increase the energy to the turbine so it can turn the compressor faster. The temperature is increased by increased fuel rate.

The YF120 is by changing the physical structure inside the engine to change bypass ratio, completely different.

What bloody chinese turbofan is a VCE, please enlighten us?
Sorry, my fault. Get confused by VCE with TVC engine. But my point is: no matter how "good" Kaveri design is, it is still sitting on the ground so far. In the mean time, you may believe that Chinese engine is "outdated", but they are flying in the sky.
 

joy_tilak

Regular Member
Joined
Jul 22, 2010
Messages
22
Likes
25
Country flag
Absolutely correct. No matter how 'good' the kaveri design is, its of no good as long as it is not serving its purpose i.e flying the LCA. The day Trump puts sanctions on India, our LCAs will be bricks sitting in hangars. On the other hand, that aint happening with China.
 
  • Like
Reactions: G10

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
Who tells you that is veriable cycle? that is typical flat-rate function which by the way is nothing new.
The increased the turbine entry temperature is to increase the energy to the turbine so it can turn the compressor faster. The temperature is increased by increased fuel rate.

The YF120 is by changing the physical structure inside the engine to change bypass ratio, completely different.
You are wrong xxxx about the 'volume of air flow' bit, and now this xxxxx post kind of suggests you are arguing just for the sake of arguing.
Anyways, let's get into the crux of the issue.

Firstly, the point is to get the engine to perform with optimum efficiency and respective thrust at varying altitudes at the subsonic, transonic and supersonic flight conditions. How you do that, DOES NOT MATTER.

Now, your myopic idea of a VCE probably just comes from the ACE----ADVENT which is a double bypass VCE and other such similar concepts, but there are other types of VCEs, like the bpr modulation by triple spool VCE, variable stream control VCE, selective bleed VCE, among others.

And Kaveri in all probability is a variable stream control engine(VSCE).
As per this late 70s AGARD report, a VSCE is a twin spool turbofan, with convergent-divergent nozzles, allows for high turbine inlet temperature and has variable geometry in the compressor and fans.
vce.PNG



Kaveri.

Twin spool
IMG_20181109_075130.png

Variable geometry in the compressor and fans
IMG_20181109_075130.png

IMG_20181113_190530.png


Convergent-divergent nozzles
IMG_20181109_075130.png

804775a5-b61a-49c0-a64f-4a503f26eb2d.jpg


High turbine inlet temperature
IMG_20181109_075130.png

IMG_20181113_170402.png



Granted, Kaveri is not as advanced as the upcoming ADVENT engine but it is still more advanced than quite a lot of turbofans out there, and regardless of your ignorance, yes it is indeed a variable cycle engine.

Secondly, xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxx flat rating concept has nothing to do with increasing the temperature in the core, like the article I initially posted states and like you erroneously thought it meant VCE.

In fact it(flat rating) is quite the opposite.
Flat rating allows for the thrust to be restricted so that the engine could perform efficiently in various ambient air conditions.
This is done by the FCU of the engine which limits the OPR, turbine entry temperature(that's right, limits the inlet temperature) and the mechanical RPM as and when necessary.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Your folly was that you presumed Indian career engineers, i.e. Indian aerospace engineers and others with advanced degrees in metallurgy, etc, wouldn't know what an old concept like a VCE is, while some random troll on the internet would.

Sorry, my fault. Get confused by VCE with TVC engine. But my point is: no matter how "good" Kaveri design is, it is still sitting on the ground so far. In the mean time, you may believe that Chinese engine is "outdated", but they are flying in the sky.
That's what I thought.
Also, it's too late to pretend you don't know the difference between "V" & "T" when you yourself replied to my initial comment with the complete acronym 'VCE' and not 'TVC'.
You probably just presumed China has a VCE, after all, how can high IQ people not have something that Indians do, and finally when you could not find after googling or baidu or whatever, you came up with this xxxxxxxxx.

Your point, intention whatever you call it was to sling mud and hope something stuck.

Kaveri's design is indeed ambitious and complex and unlike chinese development cycles we don't develop something based on just raw numbers that we'd like to see match that of west or of Russia.
DRDO R&Ds products based on QRs of the various forces, if the said QR can be satisfied with some low gen tech, then DRDO would develop just that and that's the end of it, but if something requires out of the box thinking that is a generation ahead, then DRDO is duty bound to successfully develop it.
And most would agree that this does not always give timely results, but DRDO does eventually get the job done, always
 
Last edited by a moderator:

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
xxxxxxxxxxx xxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxx All these 4 "special" characters of Kaveri are not special at all. And they are already used in current turbofan jet engines currently.


Twin spool

The majority of modern jet engines are twin spool.


Variable geometry in the compressor and fans

This is the component to control the pressure ratio, which was designed for improving the performance in supersonic cruise, nothing new.


Convergent-divergent nozzles.

The engines capable of supersonic flying are all including the design of C-D nozzles which is used to control the airflow volume and velocity.


High turbine inlet temperature

Again, nothing special about this, higher turbine inlet temperature is every jet target.


So, having these 4 doesn't make kaveri a variable cycle engine. The key idea of VCSE is to create a second independent air stream (bypass), by adjusting the airflow volume and temperature in bypass stream, the engine can adjust its bypass ratio, therefore switching between turbofan and turbojet model. Please read the study report of NASA about VCSE, you can understand better:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770011068.pdf


So far, we haven’t seen any report indicating that Kaveri can change its bypass ratio. And if Kaveri is indeed a VCE, I am not how can French provide auditing report on it since they don’t much experience on this either.
Mod: Post edited. Let me repeat. Do not engage others personally. Put only your facts and arguments on the table.Nothing else.
 
Last edited by a moderator:

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
xxxxxxxxxxx xxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxx All these 4 "special" characters of Kaveri are not special at all. And they are already used in current turbofan jet engines currently.
All these variable geometries I mentioned do make the Kaveri a variable cycle engine, according to your own link that is, but we’ll get to that.


The majority of modern jet engines are twin spool.
A Variable Stream Control Engine too possesses a twin spool.





This is the component to control the pressure ratio, which was designed for improving the performance in supersonic cruise, nothing new.





The engines capable of supersonic flying are all including the design of C-D nozzles which is used to control the airflow volume and velocity.





Again, nothing special about this, higher turbine inlet temperature is every jet target.
This whole bit is a compositional fallacy.

If you segregate the characteristics and look at them separately to construct a rhetoric, then of course there are features in VCE engines that are also present in non-VCE engines. That’s just common sense.

Also, you defining something proves nothing.



So, having these 4 doesn't make kaveri a variable cycle engine. The key idea of VCSE is to create a second independent air stream (bypass), by adjusting the airflow volume and temperature in bypass stream, the engine can adjust its bypass ratio, therefore switching between turbofan and turbojet model. Please read the study report of NASA about VCSE, you can understand better:

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770011068.pdf
LOL.

There is NO such “creation” in a VSCE, that sort of phenomenon(i.e. creation of a separate independent airstream) happens only when the designers actively chose to create a separate bypass duct like in the ACE and its subsequent VCE concepts, thereby creating a 3rd air stream which is technically the second bypass airstream(hence the term double bypass VCE). This however, is not a feature of a VSCE.

Kaveri, by virtue of it being a bypass turbofan engine, like most bypass turbofans(VCE or non-VCE) has two streams flowing through it, the primary which flows through and the secondary that bypasses the compressors, turbine and combustor unit. VSCE mostly functions in specific ambient air conditions like a conventional bypass turbofan, the concept of processing two streams of air IS NOT exclusive to VSCEs. Watch this vid for a better understanding of how air is divided and then utilised in turbofans.


What you are probably getting confused by is the far more advertised engine concept ADVENT, based on the double-bypass VCE which as I explained above, has a 3rd air stream for the purpose most probably to provide ancillary mass flow to the engine for more thrust and/or for other cooling needs and/or for better thrust efficiency and SFC; we technically don’t know what else as it’s all classified.

I suggest you carefully read the very link you posted.

The more important stuff you didn’t highlight.

REQUIREMENTS OF A VSCE from your own link.

vce k.PNG
vce k.PNG


They nigh on fit the Kaveri, just like in the AGARD report I posted.



So far, we haven’t seen any report indicating that Kaveri can change its bypass ratio.

A VSCE does not depend on varying its BPR extensively like for example in a double bypass engine.

Kaveri for example can do with just high temperature variation in the turbine.

Two basic categories of VCEs.

IMG_20181113_140824.png





And if Kaveri is indeed a VCE, I am not how can French provide auditing report on it since they don’t much experience on this either.
Mod: Post edited. Let me repeat. Do not engage others personally. Put only your facts and arguments on the table.Nothing else.
Strawman argument.

Now you are implying that both SAE and DRDO don’t know what they are doing, that’s rather disingenuous.

Kaveri is more than just the variable cycle geometries it employs, what the French are helping us with probably has nothing to do with VCEs, as the variable cycle concept has already been successfully demonstrated in DRDO’s High Mach facility.

I don’t see the need to even argue when the process has already been demonstrated.

Kaveri has already been tested in the conditions of fall in thrust due to high ambient, forward speed and which was already compensated for just with high inlet turbine temperature

All the incorrect claims you have made until now:

That DRDO does not know about VCEs, that Kaveri VCE concept is just air flow volume modulation and absolutely erroneous definitions of Flat Rating and now this fallacy filled riposte.
 
Last edited:

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
All these variable geometries...

All the incorrect claims you have made until now:


That DRDO does not know about VCEs, that Kaveri VCE concept is just air flow volume modulation and absolutely erroneous definitions of Flat Rating and now this fallacy filled riposte.

Firstly, there are lots of modern engines possess these 4 components simultaneously, but that doesn’t make them a variable cycle engine;


Secondly, current generation engine does have 2nd bypass stream, but that the air of this stream only pass through the fan and goes around the engine without going through the core and burner. As the fuel consumed by the fan is very small, with same amount of fuel by core, a turbofan generates more thrust. However, this model only work good in the sub-sonic speed. In order to enable the plane fly in supersonic, you have to add the afterburner into turbofan engine, which is quite fuel consuming and low efficient. That is why modern plane can’t fly long in supersonic speed if they are equipped with turbofan engine. On the other hand, turbojet engine is quite efficient for supersonic speed. That is why people comes up with variable cycle engine which can switch to turbojet engine in supersonic speed. Different engines have different way to achieve that, but the principle is: get part of the bypass stream flow to get heat and join the primary stream to flow through nozzle, by which changes the bypass ratio of the whole engine.


If you read the report carefully, you will see that the function of the bypass stream of VCSE is different: each stream has independent burner and nozzle systems. When the VCSE working in supersonic condition, the duct burner will start to work and heat the bypass stream, increase the primary area, so as the result, it actually reduce the bypass ratio. Thereafter, the engine gets into the turbojet model.


Variation of temperature in the turbine alone is not a variable cycle engine because:

1. You can’t increase the temperature indefinitely due to the limitation of the material;

2. Increasing the temperature will increase the thrust rather than the fuel efficiency. That is not purpose of variable cycle engine.


In other words, increasing the turbine temperature won’t solve the problem: how to achieve the best fuel efficiency in mixed flight speed.


The reason I mention about French auditing here is because they have no experience about VCE, at least they haven’t demonstrated that they achieve any meaningful progress in this yet. If Kaveri is a variable cycle engine, how can they know if it is a right design. Each part of engine is working closely as a whole, you can’t verify some aspects without considering the others.
 

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
Firstly, there are lots of modern engines possess these 4 components simultaneously, but that doesn’t make them a variable cycle engine;
That is just circular logic.

What makes Kaveri a VCE is that GTRE a DRDO lab tested it and says that Kaveri is a VCE with the said geometries.
I’m sorry, but I don’t see any complaints from any legitimate 3rd party, so it’s your word against DRDO’s.
If you have a research paper that specifically counters DRDO’s claims, I’d like to see it.

Secondly, current generation engine does have 2nd bypass stream,
Nope.
Not unless it's a double bypass VCE there aren't any conventional non VCE engines that have an independent 3rd stream or a 2nd bypass stream, as that automatically makes it a double bypass engine.
But, since you are so convinced, I'd like to see some examples.

but that the air of this stream only pass through the fan and goes around the engine without going through the core and burner.
That is just the bypass stream.
I don’t why you are defining something I already explained eons ago.

As the fuel consumed by the fan is very small, with same amount of fuel by core, a turbofan generates more thrust. However, this model only work good in the sub-sonic speed.
Nope.
The fan of the turbofan does not “consume” any fuel. All the “consuming” is done in the combustor.
Again, I suggest you first watch the video I posted that’ll help you understand the basics better.

In order to enable the plane fly in supersonic, you have to add the afterburner into turbofan engine, which is quite fuel consuming and low efficient. That is why modern plane can’t fly long in supersonic speed if they are equipped with turbofan engine. On the other hand, turbojet engine is quite efficient for supersonic speed.

That is not quite correct.
Turbojets as compared to turbofans have in general both low propulsive efficiency and high specific fuel consumption. What VCEs are trying to achieve, but not limited to, is high specific thrusts, at high speeds and low SFC.
How overall efficient an afterburning turbofan is or isn’t against a turbojet remains to be seen, maybe a scientific paper on a turbojet engine and a turbofan borne out or built around the turbojet can enlighten us.


If you read the report carefully, you will see that the function of the bypass stream of VCSE is different: each stream has independent burner and nozzle systems. When the VCSE working in supersonic condition, the duct burner will start to work and heat the bypass stream, increase the primary area, so as the result, it actually reduce the bypass ratio. Thereafter, the engine gets into the turbojet model.
I can’t in all honesty say what extra burner system Kaveri has as there’s no public information even about even the primary burner unit itself present in the Kaveri.
All I can say is that the Kaveri which evolved from the GTX37-14U has demonstrated the variable cycle tech like in the current Kaveri. PERIOD.
A GTRE paper from the 80s.
vce gtre.PNG


Variation of temperature in the turbine alone is not a variable cycle engine because:

1. You can’t increase the temperature indefinitely due to the limitation of the material;

2. Increasing the temperature will increase the thrust rather than the fuel efficiency. That is not purpose of variable cycle engine.


In other words, increasing the turbine temperature won’t solve the problem: how to achieve the best fuel efficiency in mixed flight speed.
When did I say or even imply that you have to increase the temperature indefinitely at the core?
And yes, varying temperature in the turbine does make some very specific engines like the Kaveri a VCE, as the paper I had quoted showed aptly.

Please don’t give your own understanding of why temperature variation isn’t enough to make a VCE a VCE. I suggest you show some proof like I did in the form of a research paper.

Again your version of 'what a VCE is' is very myopic, what you are defining above is some super next gen s#it being pursued in the ACE, the more common VCEs will not be able to provide superbly low SFC, but will function like a conventional turbofan and give a low SFC like such.

Again, read your own paper, it's all there.

The reason I mention about French auditing here is because they have no experience about VCE, at least they haven’t demonstrated that they achieve any meaningful progress in this yet. If Kaveri is a variable cycle engine, how can they know if it is a right design. Each part of engine is working closely as a whole, you can’t verify some aspects without considering the others.
As for "experience".
Technically speaking, no country has a proper mass produced VCE, be it USA or France.
And yes, France has like India attempted VCE concepts.

You have it in your mind that a variable cycle engine is some form of godly firmamental tech that cannot be achieved in this space or time.

When the fact is that there are various levels of VCEs and you are only concentrating on the top most one while simultaneously denying the validity of others which are more realistic.
 
Last edited:

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
That is just circular logic.


What makes Kaveri a VCE is that GTRE a DRDO lab tested it and says that Kaveri is a VCE with the said geometries.

I’m sorry, but I don’t see any complaints from any legitimate 3rd party, so it’s your word against DRDO’s.

If you have a research paper that specifically counters DRDO’s claims, I’d like to see it.

Why there should be any legitimate 3rd party complaint? The Kaveri is not in the market, not even operational now, “what it is” or “how it is” is not any legitimate 3rd party’s concern.



Nope.

Not unless it's a double bypass VCE there aren't any conventional non VCE engines that have an independent 3rd stream or a 2nd bypass stream, as that automatically makes it a double bypass engine.

But, since you are so convinced, I'd like to see some examples.

Obviously, you didn’t even understand what I said. I said: even though non-VCE engines have by-pass stream, but this stream doesn’t work with independent burner.




That is just the bypass stream.

I don’t why you are defining something I already explained eons ago.

Yes, but you don’t understand what is difference between the bypass stream of turbofan engine and the bypass stream of VCE. That is why I have to explain to you from ABC.




Nope.

The fan of the turbofan does not “consume” any fuel. All the “consuming” is done in the combustor.

Again, I suggest you first watch the video I posted that’ll help you understand the basics better.

No, fan (the front fan) does consume fuel, but not as much as the combustor does. The by-pass stream is propelled by fan and provide thrust in addition to the exhausted hot stream.


Check this paper from NASA: https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html


Quote:” Because the fuel flow rate for the core is changed only a small amount by the addition of the fan, a turbofan generates more thrust for nearly the same amount of fuel used by the core.”



That is not quite correct.

Turbojets as compared to turbofans have in general both low propulsive efficiency and high specific fuel consumption. What VCEs are trying to achieve, but not limited to, is high specific thrusts, at high speeds and low SFC.

How overall efficient an afterburning turbofan is or isn’t against a turbojet remains to be seen, maybe a scientific paper on a turbojet engine and a turbofan borne out or built around the turbojet can enlighten us.

Please stop twisting the subject. No one is talking about the overall efficiency. Instead, I clearly pointed out: turbojet perform better efficiency than turbofan engine in SUPERSOINIC speed because the fan will generate more drag in supersonic speed which decreases the efficiency significantly. So, the VCE’s concep is working as turbofan in subsonic speed and transfer to turbojet model in supersonic speed. That is the whole idea.




I can’t in all honesty say what extra burner system Kaveri has as there’s no public information even about even the primary burner unit itself present in the Kaveri.

All I can say is that the Kaveri which evolved from the GTX37-14U has demonstrated the variable cycle tech like in the current Kaveri. PERIOD.

A GTRE paper from the 80s.

View attachment 29693 .

Honey, have you read the tile of your paper? – “Flat rating concept in GTX engine” on the top.


When did I say or even imply that you have to increase the temperature indefinitely at the core?
And yes, varying temperature in the turbine does make some very specific engines like the Kaveri a VCE, as the paper I had quoted showed aptly.

Ok, based on this paper, I agree that varying turbine entry temperature is kind of VCE. However, as this paper points out: this kind of VCE only achieve 3.6% of improvement in its SFC. And the whole study is about sub-sonic stage. And to me this kind of temperature varying function is already available in modern turbofan engine with FADCE.


The VCE everybody is working on at the moment is more focus on the supersonic speed.

Please don’t give your own understanding of why temperature variation isn’t enough to make a VCE a VCE. I suggest you show some proof like I did in the form of a research paper.

Well, I don’t need to, because your research paper only tell how “flat rate” is achieved, didn’t explain how to change the “MAXIMUM” temperature in the flight.


As my understanding, the “maximum” temperature is more related to the limit of material.


Again your version of 'what a VCE is' is very myopic, what you are defining above is some super next gen s#it being pursued in the ACE, the more common VCEs will not be able to provide superbly low SFC, but will function like a conventional turbofan and give a low SFC like such.


Again, read your own paper, it's all there.

Ok, so there is nothing special about this Kaveri’s variable cycle function.


You have it in your mind that a variable cycle engine is some form of godly firmamental tech that cannot be achieved in this space or time.

When and where did I claim that, please point it out. I simply question the claim that Kaveri is a variable cycle engine. And now I agree Kaveri is a variable cycle engine even though it is kind of wired.


And base this definition, there are quite a lot of engines which are operational now can be called variable cycle engine.
 

republic_roi97

Senior Member
Joined
Sep 12, 2016
Messages
1,960
Likes
2,700
Country flag
Guys what's up with Kaveri Engine, I heard somewhere that it was going to be flight tested on a Sukhoi/Tejas ??
 

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
Guys what's up with Kaveri Engine, I heard somewhere that it was going to be flight tested on a Sukhoi/Tejas ??
This August, India just asked high altitude test facilities to send their proposal for Kaveri. Based on this, Kaveri is still couple years away from flight testing on any fighter jet even if everything goes smoothly.
 

cyclops

Senior Member
Joined
Apr 24, 2016
Messages
1,318
Likes
5,767
Country flag
Why there should be any legitimate 3rd party complaint? The Kaveri is not in the market, not even operational now, “what it is” or “how it is” is not any legitimate 3rd party’s concern.
Engineers by the way of scientific papers, question and analyse systems they have no access to and even those, that aren't even prototyped yet, info on Kaveri on the other hand is widely available and papers on it also present.

Anyone with the requisite engineering experience willing to prove Kaveri is not a VCE could easily do it, it has nothing to do with Kaveri being or not being in the market.

Obviously, you didn’t even understand what I said. I said: even though non-VCE engines have by-pass stream, but this stream doesn’t work with independent burner.
And you’re doing it again.

Don’t make an empirical claim about anything without having facts to back it up.


Quite a few conventional turbofans have independent secondary burners.

Info on a US patent for a secondary bypass augmentation burners used in the bypass air passages of turbofans to provide extra thrust, from 1974.

http://www.patents.com/us-3999378.html

For info’s sake you should also look up duct burning turbofans, interstage turbine burners.

Yes, but you don’t understand what is difference between the bypass stream of turbofan engine and the bypass stream of VCE. That is why I have to explain to you from ABC.
I don’t think so, you were/are having trouble understanding how a normal turbofan works, VCE is still far off.

Your comments below only prove it further so.

No, fan (the front fan) does consume fuel, but not as much as the combustor does. The by-pass stream is propelled by fan and provide thrust in addition to the exhausted hot stream.



Check this paper from NASA: https://www.grc.nasa.gov/www/k-12/airplane/aturbf.html



Quote:” Because the fuel flow rate for the core is changed only a small amount by the addition of the fan, a turbofan generates more thrust for nearly the same amount of fuel used by the core.”
It’s not a scientific paper really, literally the first line says it’s a kids page meant for students.

Either way, WTH?

Now I definitely know that your understanding of even the basics of a turbofan is incomplete.

Your own link says nothing about the fan consuming any fuel.

Basic english comprehension skills. The fuel flow rate is changed by the “addition of the fan”, NOT “addition to the fan”. So change in the fuel flow rate does not automatically mean direct consumption of fuel by the fan. LOL

What the article you posted basically states is that the fuel flow rate changes(most likely decreases as compared to a turbojet) with the inclusion of a fan in a turbofan engine(hence the name). The fan doesn’t need to burn the fuel to augment the thrust, as your own link states, “ The air that goes through the fan has a velocity that is slightly increased from free stream. So a turbofan gets some of its thrust from the core and some of its thrust from the fan.”

You keep posting links but you barely read them.

This could have all been avoided if you had just seen the vid like I told you to. The LPT runs the fan so no, no fuel is consumed by the fan.



Please stop twisting the subject. No one is talking about the overall efficiency. Instead, I clearly pointed out: turbojet perform better efficiency than turbofan engine in SUPERSOINIC speed because the fan will generate more drag in supersonic speed which decreases the efficiency significantly. So, the VCE’s concep is working as turbofan in subsonic speed and transfer to turbojet model in supersonic speed. That is the whole idea.
See this is why I say you don’t know what you’re talking about.

You ABSOLUTEY HAVE to talk about the overall efficiency or else you are just missing the point of a VCE. Your problem is when you talk about a VCE you only talk about one aspect of it, and not about fuel efficiency or the MFR or everything else in between, which is the whole point of a VCE and NOT JUST THE THRUST or the other more advertised features.

SO no, the idea is not just speed and thrust, it is to provide high consistent thrusts in most if not all flight conditions and give superb fuel consumption which allows the fighter to fly fast and fly longer and farther.

vcdefgdzfb.PNG


Honey, have you read the tile of your paper? – “Flat rating concept in GTX engine” on the top.
And?

You clearly saw the variable cycle bit in the paper but still you spew a strawman argument about a completely irrelevant point to reinforce that confirmation bias. Refute what’s written in the paper or just stop.

Don’t judge a book by its cover and don’t judge a scientific paper by its heading.



Ok, based on this paper, I agree that varying turbine entry temperature is kind of VCE. However, as this paper points out: this kind of VCE only achieve 3.6% of improvement in its SFC. And the whole study is about sub-sonic stage. And to me this kind of temperature varying function is already available in modern turbofan engine with FADCE.
Stop with the strawman arguments. What part of the VCE the paper is specifically explaining is besides the point. The crux of the matter is whether if VCE can be achieved by increasing the temperature, and it can be.

It really doesn’t matter what any of these things mean TO YOU, you are just one person without the sufficient qualification, experience or scientific literature to make any claim of the sort or even question the experts in this particular field and unless you can prove that increasing the temperature in Kaveri doesn’t make it a VCE, anything else you say beyond this is just moot.

The VCE everybody is working on at the moment is more focus on the supersonic speed.
Your myopic view on VCE is just killing me with this oppressive sense of ennui.

As I have told you for the umpteenth time, speed and thrust is nigh half the purpose of a VCE.

As per GE.

https://www.geaviation.com/military/engines/ge-adaptive-cycle-engine

Developed under the U.S. Department of Defense’s Adaptive Versatile Engine Technology (ADVENT) and Adaptive Engine Technology Development (AETD) programs, the GE Adaptive Cycle Engine is the only engine that combines outstanding fuel burn with increased, fighter-level thrust, enabling next-generation military combat aircraft to go greater distances and engage more targets.

Unlike traditional engines with fixed airflow, the GE ACE is a variable cycle engine that will automatically alternate between a high-thrust mode for maximum power and a high-efficiency mode for optimum fuel savings. And that means a whole new book of operational possibilities for the U.S. Air Force.


Well, I don’t need to, because your research paper only tell how “flat rate” is achieved, didn’t explain how to change the “MAXIMUM” temperature in the flight.

As my understanding, the “maximum” temperature is more related to the limit of material.
Yes you need to.

Now you are nit-picking about the temperature while completely ignoring the fact that Kaveri in all its paper has the term VCE plastered on it.

We weren’t debating how much temperature Kaveri can withstand but whether if it’s a VCE or no.

Again, your own understanding of ‘what a VCE means’, means squat. If you have written a peer reviewed paper on the subject then do show it.

The variable cycle function is being brought on by increasing the temperature yes, but that doesn’t mean you definitely have to keep on increasing the temperature indefinitely to achieve the VCE function. As THIS ALREADY HAS BEEN PROVEN in DRDO’s High Mach facility. Kaveri is a VCE with the stated TET and the variable geometries. PERIOD.

As for how to increase the temperature.

That’s a silly question, you even answered it. You increase it by getting better materials.

The paper is from the 80s, and is about the GTX 37-14U we have since then moved from DS blades to second and third generation SCBs and are currently on the K9, K10 variants of the far more advanced GTX-35VS.

Ok, so there is nothing special about this Kaveri’s variable cycle function
.

As I had already explained many comments ago, compared to ACE-ADVENT, no, Kaveri doesn’t even come close, as don’t most turbofans, VCE or no.

But compared to any other conventional turbofan, yes, it is relatively advanced, it’s a VCE.

When and where did I claim that, please point it out. I simply question the claim that Kaveri is a variable cycle engine. And now I agree Kaveri is a variable cycle engine even though it is kind of wired.
You can definitely ask a question, there’s nothing wrong with that, but what you can’t do without appearing disingenuous is make a definite empirical statement claiming DRDO is wrong when they say Kaveri is a VCE, and say that without a single iota of proof from any legitimate scientific author agreeing to your pov.

But now that we agree that Kaveri is a VCE there’s no use for this debate, as it rightly never was.

And base this definition, there are quite a lot of engines which are operational now can be called variable cycle engine.
Again, don’t just make arbitrary claims borne out of your own opinions.

If a turbofan developer is achieving the set parameters with their particular design however it may be and calling it a VCE, then it’s a VCE.

And if you have any doubts, bring out the relevant scientific literature from an organisation both having access and adept at auditing the machine, thereby validating your doubts. Maybe then we can talk.

Until then, opinions aren’t facts.
 
Last edited:

HariPrasad-1

Senior Member
Joined
Jan 7, 2016
Messages
9,611
Likes
21,081
Country flag
As my understanding, the “maximum” temperature is more related to the limit of material.
Very true. It depends on metallurgy. Earlier Kaveri blades were good for some 1450* c now it is increased to 1600*+. So you can now operate engine for higher temperature. Actually the efficiency of Gas turbine depends on design as well as metallurgy (i.e max temperature at which it can be operated). Next challenge is to reduce the weight. Now a days composite fans have made its way in turbine used for passenger planes.
 

no smoking

Senior Member
Joined
Aug 14, 2009
Messages
5,014
Likes
2,309
Country flag
But now that we agree that Kaveri is a VCE there’s no use for this debate, as it rightly never was.
Oh, yes, I absolutely agree with you because based on this, every modern turbofan is VCE, because they all can increase their thrust by adjusting the temperature. Now I can even call WS-10B and WS-13 the VCE engine because with FADEC they certainly can do that.
 

HariPrasad-1

Senior Member
Joined
Jan 7, 2016
Messages
9,611
Likes
21,081
Country flag
I think what went wrong with Kaveri is that it was too ambitious design. or low bypass turbofan design, you need a highly efficient core because if your core is not efficient, you can not get that bypass flow. Initial kaveri design was too ambitious with 5 stage compression. GE 414 operates on 30:1 compression ratio. This is too difficult to achieve. I think kaveri has not reached even 25:1. This makes core less efficient and in totality, it is too difficult to achieve that bypass ratio ratio. Core must generate sufficient power to rotate fan and achieve high bypass ratio.
My 2 cent guys. Please correct me guys if I am wrong.
 

Global Defence

New threads

Articles

Top