Kaveri & Aero-Engine: News & Discussion

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SaiK
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Re: Kaveri & aero-engine discussion

Post by SaiK »

https://www.theatlantic.com/technology/ ... re/552959/

The Jet Engine is a Futuristic Technology Stuck in the Past
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Re: Kaveri & aero-engine discussion

Post by Rishi_Tri »

You may add HAL HTSE 1200 to list of engine efforts. As to High BPR engines, today's commercial engines are exactly that. High on fuel efficiency. They are also fatter to look at. Easy comparison shall be engines that power old Air India /Alliance Air 737s and those that power the modern day 737-800s operated by Jet or Spice.

As Kaveri with M88 is progressing, hope we learn, whatever we can, and make Kabini what it needs to be.
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Re: Kaveri & aero-engine discussion

Post by Haridas »

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

Will lead into interesting intake design discussion, if only yak herder stops collecting dung in such cold arctic weather :wink:
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Re: Kaveri & aero-engine discussion

Post by Rakesh »

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

Will lead into interesting intake design discussion, if only yak herder stops collecting dung in such cold arctic weather :wink:
Haridas-ji: Might I humbly suggest that you take the lead in aero engine discussion? We all on BRF can learn so much!

To start off, can you please advise on the questions you posed above?
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Re: Kaveri & aero-engine discussion

Post by ramana »

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

Will lead into interesting intake design discussion, if only yak herder stops collecting dung in such cold arctic weather :wink:
the wiki post by Rakesh gives examples of modern combat jet engines By Pass Ratio (BPR).
Most are ranging from 0.3 :1 to 0.2:1.

Kaveri goal is 0.16:1

And understanding the definitions given below its quite modest requirement as the ducted fan has to produce 0.16 lb of air to every pound of thrust from the hot section.
The other jets are producing double that.

So M-88 (with 0.3:1 BPR) in the Kaveri BPR 0.16:1)would be putting a racehorse heart in a jutka horse.

And here are some answers:

Advantages of low BPR in

Link: https://aviation.stackexchange.com/ques ... pass-ratio
Because the priorities for military aircraft (engines) are different. While it is true that the high bypass turbofans have better fuel economy (in cruise) and are less noisy, the low bypass engines offer significant advantages when we take into account their intended use in combat aircraft, such as:

The response of the low bypass turbofans to throttle adjustments is faster compared to the high bypass turbofans; the inertia is less and less air mass is involved (for increasing the velocity)- This is important during combat, when thrust requirements change rapidly.


They have less frontal area, reducing the drag produced. For aircraft expected to fly at supersonic speeds, however briefly, this is important.


•Better thrust to weight ratio- 6:1 in Trent 1000 Vs 9:1 F119 (used in F-22 Raptor)- Even if the actual thrust produced by the low bypass turbofans is lesser, they produce more thrust per kg of engine, which means that the engine can be more compact in size.


The low bypass turbofans are more efficient at higher speeds compared to the high bypass turbofans.


The lesser size of the low-bypass turbofans mean that the aircraft can be made stealthier by 'burying' the engines in the fuselage, which is all but impossible in case of high bypass turbofans
And general education about turbofans:

https://en.wikipedia.org/wiki/Turbofan
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion,[1] and the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine (through the combustion chamber), in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the thrust. The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together; engines that use more jet thrust relative to fan thrust are known as low-bypass turbofans, conversely those that have considerably more fan thrust than jet thrust are known as high-bypass. Most commercial aviation jet engines in use today are of the high-bypass type,[2][3] and most modern military fighter engines are low-bypass.[4][5] Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines.

Here is wiki on By Pass Ratio that has a nice graphic and also a table of modern turbo fans.

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

Am not posting to prevent clutter the thread and folks on smart phones.


My comments:

If you look at the picture of the low BPR turbofan it has large fan and then the compressor stages.
That's where the vibrations are coming from.


https://upload.wikimedia.org/wikipedia/ ... on.svg.png


Now if you put a hot M-88 core in that engine will those fan blades handle the increased airflow?

Already they are screeching with Kabini core.

I think its best option to sink a few 1000 crores and make a new Kaveri-2 core tailored to the Tejas Mk2

give the job to HAL and GTRE can go back to research which is where their heart is .
But cut their budget by half to get rid of the deadwood.*


The dry thrust is good enough but the BPR is too low and more like a turbojet level.

Nice try to pass of the old Turbojet as a turbofan.


I think the Safran guys are fooling us around and GTRE wants foreign collaboration as they don't want to admit failure.

* Many are most likely my classmates so don't accuse me of being cruel.
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Re: Kaveri & aero-engine discussion

Post by ramana »

IR if you know any Kaveri design guy ask him how a M88 core will work in a Kaveri shroud?

I don't think it will unless its de-rated.
And they say its dia is smaller than the Kaveri shroud.
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Re: Kaveri & aero-engine discussion

Post by Indranil »

I can't discuss specifics here. WE can speculate based on the laws of physics.
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Re: Kaveri & aero-engine discussion

Post by ramana »

Sure let it be Physics based.
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Re: Kaveri & aero-engine discussion

Post by Indranil »

The core of the engine is where the fuel is burnt to generate energy. This energy can be changed into thrust by pushing the hot exhaust at back of the core or by changing into the mechanical energy of a fan which pushes air back around the core. Turboshafts and turboprops are at one end of the spectrum where almost all the thrust is derived from the fan pushing air back. Turbojets are at the other end of the spectrum wherein almost all the energy is derived from the hot gases ejecting out of the back. Turbofans are in between, where part of the thrust comes from a ducted fan and part from the exhaust of the core. The Bypass ratio loosely defines where in this spectrum do you lie. A turbofan with a high BPR derives relatively higher thrust from the fan vis-a-vis a turbofan with a low BPR.

As it turns out, engines with higher BPR have better efficiency at high altitudes and subsonic/transonic regimes. That's why civilian jets designed for mostly cruising along this regime have high BPR turbofans. But high BPR turbofans have the disadvantages that you brought forward.

A fighter designer is faced with an even more challenging flight envelop. What should be the "design point" of the engine? There is no good answer. Every designer chooses a different point and hence you see the different BPRs.

What Maitya sir, JayS, UB, Haridas ji can teach us is what would be the BPR of a Kaveri fan with a M88 core. These numbers can be easily calculated from numbers present online. Maitya sir had a good excel sheet going. But it is obvious that the M88 being a smaller core than the Kabini will give rise to higher BPR engine with all its associated pluses and minuses.

Will it be a 404 equivalent. I don't think so. The refinement and materials that have gone into the latest 404s/414s is right up there. We still have lot to learn. Will it be a RD-33/93 equivalent. I think so.
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Re: Kaveri & aero-engine discussion

Post by maitya »

Indranil wrote:<snip>
What Maitya sir, JayS, UB, Haridas ji can teach us is what would be the BPR of a Kaveri fan with a M88 core. These numbers can be easily calculated from numbers present online. Maitya sir had a good excel sheet going.
<snip>
Hello Indranil, I think you are talking about this excel: Image

Frankly, I'm completely lost wrt this new discussion wrt BPR etc ... Admiral took a leaky-turbojet and started comparing with next gen turbofans (he may have got confused with F-404 BPR values, which is contemporary to Kaveri etc), which is not the right thing to do.

What people may want to do is COMPARE the various columns of the excel and see for themselves, what is the effect of increasing the BPR with or without OPR and TeT increase (last 3 columns, of the Ganga ((c)Vinaji) injin).
Hint: Where exactly will the energy come from if we simply put a large Fan in the front and scream high-BPR, high-BPR etc - from the same old LPT right - which is limited by same "leftover" of the rotating energy extracted by the HPT, which in turn is itself limited by TeT-OPR combo (refer to Kaveri Sticky for the relationship betw them).

You want high emergency thrust - how about increasing the mass-flow (refer to the same excel) instead - yes dry SFC will increase, but then again we are talking about military application right?
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Re: Kaveri & aero-engine discussion

Post by chaitanya »

Hi everyone,

Something has been bothering me about this 'Safran-ized' Kaveri. We have seen many articles highlighting serious technical issues with the current Kaveri design and how this M88 hybrid might be the best solution to get the engine running 'in time'. While it might give us a working jet engine, will it provide any knowledge on how to rectify these issues in future jet engines? Or was that never on the table? I hope this process isn't being rushed so much that we lose the ability to gain critical knowledge.
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Re: Kaveri & aero-engine discussion

Post by SaiK »

Wasn't the Concorde's RR/Snec engine a ZERO BPR one?
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Re: Kaveri & aero-engine discussion

Post by ramana »

SaiK wrote:Wasn't the Concorde's RR/Snec engine a ZERO BPR one?
Yes. Its BPR=0 as its a turbojet.
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Re: Kaveri & aero-engine discussion

Post by ramana »

Maitya, Maybe I should have addressed you?
IR if you know any Kaveri design guy ask him how a M88 core(designed for BPR 0.3) will work in a Kaveri (Designed for BPR 0.16) shroud?

I don't think it will unless its de-rated.
And they say its dia is smaller than the Kaveri shroud.
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Re: Kaveri & aero-engine discussion

Post by Rakesh »

maitya wrote:Frankly, I'm completely lost wrt this new discussion wrt BPR etc ... Admiral took a leaky-turbojet and started comparing with next gen turbofans (he may have got confused with F-404 BPR values, which is contemporary to Kaveri etc), which is not the right thing to do.
Aiyoo Saar, No, No :lol:

All I did was post an email that someone sent me. You are obviously knowledgeable on turbofans and I defer to you. My only wish is to get a certified Kaveri engine. Whether that is via GTRE, Safran, RR or whoever else....matters little to me.

The end goal is to reduce dependence on a foreign engine and have our own. Till then, screwdrivergiri it is...
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Re: Kaveri & aero-engine discussion

Post by Kartik »

This event seems to have been done with an eye towards some of the F-414 manufacturing being shifted to India, as part of whatever offsets will be needed if the Tejas Mk2 comes about and uses the F-414.

GE & TASL develop engine manufacturing facility
General Electric (GE) and Tata Advanced Systems Limited (TASL) have started construction of a new facility in India that will be positioned to build engine components for military and commercial applications.

A joint statement on 12 February said the facility, located in Hyderabad, will incorporate GE technologies in support of localised manufacturing, assembling, integration, and testing of components.

An initial focus of the factory will be to supply components for the CFM International LEAP aircraft engine for customers worldwide. However, the companies’ added that the facility will also enable TASL to expand into other GE product lines including military aircraft engines.
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Re: Kaveri & aero-engine discussion

Post by Rakesh »

Very good move and good find Kartik.
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Re: Kaveri & aero-engine discussion

Post by VinodTK »

Kartik wrote:This event seems to have been done with an eye towards some of the F-414 manufacturing being shifted to India, as part of whatever offsets will be needed if the Tejas Mk2 comes about and uses the F-414.
Tata-GE aircraft engine JV order book full for next 5 years

HYDERABAD: A joint venture between Tata Advanced Systems and General Electric, which is setting up an aircraft engine component manufacturing-cum-research hub in Hyderabad, has already got orders for the next five years, a top official said.

The facility is expected to be ready for manufacturing by the year end, catering to GE's global demands as well as India's defence market. The joint venture will also sup a skilling centre to train youth in engine manufacturing.

"This facility will manufacture components for Leading Edge Aviation Propulsion (LEAP) engines for jets and will cater to aircraft manufacturers like Airbus and Boeing and supply components for India and global markets of GE," Vishal Wanchoo, president of GE South Asia, told journalists in Hyderabad on Monday at the venue of the ground-breaking ceremony. "We have already received 200 orders from 35 aerospace companies even before the start of the facility," he said.

While GE will bring its expertise in aircraft engine design and research, TASL will be the manufacturing partner. The upcoming facility in Adibatla on the outskirts of Hyderabad is at a location where Tata already has manufacturing units with other joint venture partners including Boeing. "We have two aerospace parks in Hyderabad along with five airstrips that will help in setting up a skilling academy," said KT Rama Rao, Telangana industries minister.
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Re: Kaveri & aero-engine discussion

Post by ramana »

Rakesh,

Don't want to rain on the parade but , civil aircraft jet engine component mfg is way different than military combat jet engines as last page has shown. I really don't know what these companies bring to table.

The CFM International LEAP is a high-bypass turbofan engine. It is produced by CFM International, a 50-50 joint venture company between GE Aviation of the United .........

I would like to go back to Kaveri. I think we are on verge of understanding what is lacking.
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Re: Kaveri & aero-engine discussion

Post by JayS »

IIRC - CFM = GE core + Safran LP system
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Re: Kaveri & aero-engine discussion

Post by NRao »

Only for commercial engines.
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Re: Kaveri & aero-engine discussion

Post by chetak »

NRao wrote:Only for commercial engines.
No country, big or snall, is willing to go it alone for the ab initio development of a jet engine.

Too risky and too rich for their blood.

Some people, it seems have yet to learn this lesson.
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Re: Kaveri & aero-engine discussion

Post by nvishal »

In the past we have seen the west offer certain technologies to india only when local R&D attained a breakthrough

Judging from the above article, I would like to Boldly state that the kaveri seems to have very likely attained a breakthrough.
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Re: Kaveri & aero-engine discussion

Post by SaiK »

^like saying closing hot selling ice-cream corner shops reduce traffic accidents. we need a good source and confirmation about Kaveri program. I doubt it is something so classified that none will know. It ain't a boomer or a half-warp nuke engine for next Indian military space odyssey (just saying). The point being, we are getting into too much of ass-u-me process.
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Re: Kaveri & aero-engine discussion

Post by chetak »

SaiK wrote:^like saying closing hot selling ice-cream corner shops reduce traffic accidents. we need a good source and confirmation about Kaveri program. I doubt it is something so classified that none will know. It ain't a boomer or a half-warp nuke engine for next Indian military space odyssey (just saying). The point being, we are getting into too much of ass-u-me process.
All said and done, this is a military project and not a commercial one.

People posting gyan on program specifics can very very easily be tracked, identified and dealt with, often in drastic career changing/ending ways.

best to limit discussions on an open forum to either open source stuff or general principles.

some heroes, have, in the past, landed up in the red fort, fcuked and really, really far from home.
one of the few occasions when such news has made it to the public domain.

A large majority of the rest of such "cases" are handled very quietly.

Army officer posted in Jabalpur detained by Military Intelligence
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Re: Kaveri & aero-engine discussion

Post by nvishal »

SaiK,

If profits ranked high in the american policy then we would have seen restricted hardwares being sold to india decades ago.

So why the f16 now? Why the GE turbofan now?

What changed in the last few years?

And why hasn't the GoI accepted the f16 or the GE proposal(both have partnered with local private firms instead)?
Is it premature of me to state something that is obvious?
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Re: Kaveri & aero-engine discussion

Post by chetak »

I think that they need the f-16 plant running somewhere in the world and they are trying to con the Indians by claiming that its part of Modi's "make in India" program. A less obtrusive version of the cheeni belt and road drama but nevertheless the covert coercive push seems to be there.

In the meanwhile, to offset the cost of plant and machinery being transported and setup in India, they are pitching for Indian orders.

For them to be pushing so hard on flogging this outmoded teen to India, there has to be something big in the background or someone very big in the govt is quietly pushing it.

on what terms, only time will tell.

but there is already a rancid smell wafting in the breeze in terms of intent.

Rest assured that none of the cutting edge systems nor the high tech munitions will follow without a whole lot of restrictive conditions that India will not be able to fulfill.

A lot of sheet metal and a whole load of screwdrivers is what I am seeing.
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Re: Kaveri & aero-engine discussion

Post by JayS »

nvishal wrote:SaiK,

If profits ranked high in the american policy then we would have seen restricted hardwares being sold to india decades ago.

So why the f16 now? Why the GE turbofan now?

What changed in the last few years?

And why hasn't the GoI accepted the f16 or the GE proposal(both have partnered with local private firms instead)?
Is it premature of me to state something that is obvious?
In my opinion nothing has changed (barring some obvious changes with time).

About money, whatever we can provide to US in terms of profits is peanuts for them.
NRao wrote:Only for commercial engines.
CFM is Civil only JV. So that's kinda obvious.

There is another equivalent JV I know of - Russian engine which is on Sukhoi Superjet. French core + Russian LP system.
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Re: Kaveri & aero-engine discussion

Post by JayS »

So why exactly we are discussing BPR here..?
What is optimal value of BPR..?
Why 0.16 is good or bad for Kaveri...?
which one is tougher to achieve, low BPR or high BPR..?
If all reported problems of Kaveri are with LPC and A/B, why are we replacing the core..?
If Kabini was all that problematic, why UCAV was given go ahead with dry Kaveri..?

Many questions, no definite answers.
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Re: Kaveri & aero-engine discussion

Post by NRao »

CFM is Civil only JV. So that's kinda obvious.
To a few/most, it is obvious. Better to include it in posts. Very good posters have made two mistakes: they expect civilian and military segments in the same company to share techs (the default is they do not) and that the company will then share it with other nations (which, by default, is not true either). Anyways ....................
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Re: Kaveri & aero-engine discussion

Post by SaiK »

The tougher aspect to achive are in the precision domain.

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

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

The optimal BPR is trade secret worth GTRE itself.

So far.
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Re: Kaveri & aero-engine discussion

Post by Rakesh »

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

Post by Cybaru »

Even that is great! TASL can provide components to Kaveri88 when it goes into production.
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Re: Kaveri & aero-engine discussion

Post by ramana »

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

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

Need to spend money to get there.
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Re: Kaveri & aero-engine discussion

Post by ramana »

Or tell GE to setup 100% F404 mfg facility in Bengluru.None of this screwdrivegiri.
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Re: Kaveri & aero-engine discussion

Post by SaiK »

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

Post by Haridas »

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

Will lead into interesting intake design discussion, if only yak herder stops collecting dung in such cold arctic weather :wink:
Haridas-ji: Might I humbly suggest that you take the lead in aero engine discussion? We all on BRF can learn so much!

To start off, can you please advise on the questions you posed above?
Rakesh ji, Have to apologize as I am on BR Forums for timepass only. I don't have time nor energy to lead anything, not that I have much competence in even few subject matters. Please tolerate me.

The questions that I asked however are hint/guidance for seekers on worthwhile pursuit for better understanding.
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Re: Kaveri & aero-engine discussion

Post by Avtar Singh »

Bypass Ratio...

see here

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

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

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

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

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

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

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


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

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

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

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

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

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

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

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

Hope this helps.

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

https://aviation.stackexchange.com/ques ... -n1-and-n2
ramana
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Re: Kaveri & aero-engine discussion

Post by ramana »

Avatar using all that knowledge please comment on Kaveri design.
Specifically look at why it is not achieving the afterburner thrust.
Indranil
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Re: Kaveri & aero-engine discussion

Post by Indranil »

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