JayS wrote:Indranil wrote:
I am not so sure that he was speaking of wet thrust. I think we was speaking of materials. With a higher TET. See the quoted part below. I think with a 25 kN engine, they can easily get 40kN of wet thrust.
https://aquantumofmind.wordpress.com/20 ... ndia-2015/
HAL has a great engine on their hands. I wish they design an engine with ~36kN of dry thrust and ~54 kN of wet thrust. They can design an awesome AJT/LIFT based on that.
Thats my blog page btw and its from AI-2015. You said AI-2019. So I was thinking something else.
When HAL talks about 35-50kN for HTFE its always with A/B.
Its not just about materials, whole aerothermodynamic design and system level architecture needs to be relooked at with such large change. The hot core has
very limited organic growth potential with some refined redesign (called PIP in industry), typically ~2-3%. Unless some significant tech infusion happens something like from metallic to CMC blades, of that order (which is a huge change BTW), it wont give much bigger thrust without system level redesign.
A big chunk of dry thrust can be changed thru tailoring LP system actually, but even then the total organic growth wont be larger than ~10%. Max 20% with all sorts of stuff added up.
HTFE uses uncooled blades. If one wants to
extract significantly higher thrust with same air intake (proportionally higher intake would mean full redesign of core) means burning more fuel, that is much higher TIT. Though HTFE has a lot of margin on TIT as of now, any increase from current level would require introducing either CMC like material (currently even GE has not demonstrated CMC in HP, IIRC, rest are all lightyears behind) to keep uncooled blades, else introducing cooling for HPT/LPT blades. Introducing cooling is a tedious job, especially for a small engine. And it doesn't give the proportional benefit we may thing it would give, hiking TIT, because cooling takes up upto 25% of HPC output, proportionally reducing the air passing thru the combustion chamber. You can imagine the whole sizing of the engine would need a relook with such change. Then there is a matter of making cooling air channels/spaces in the engine, which would increase complexities of entire secondary air system by orders of magnitude. I'll leave it at this.
The Tech gap between HTFE and Kaveri is huge. But a Geometrically scaled larger engine with same tech level as HTFE can be built for 35kN dry thrust, but it will essentially be a different engine.
I got asked, in the AMCA thread, that if HTFE can be scaled to a 30/48KN turbofan or not ... and
the reason why I quoted JayS post is that there's not much more to say than what he's already said in it - I've highlighted some important points in it.
Today HTFE achieves 25KN dry ... making it to produce 30KN, so 20% more, would be quite difficult without completely redesigning the core.
Typically, with the same core, 5-7% more should be achievable by a lighter/more-efficient Fan.
Trouble is, HAL "cheated" with the HTFE ... aka they went for the higher quoted max dry thrust figures (more suitable for glossy-brochures), achieved though a higher BPR setting. What I mean is, the proportion of the dry-thrust coming form the Fan is quite high (like F404 for example), compared to that coming from the Core.
But that's ok for a platform designed for training (IJT/AJT etc), where success-factor is more on MTBO/MTBF type engine lifecycle costs than that of a raw fighter application - anybody having wet-dreams of having a Jaguar re-engined with a HTFE derivative, would be surprised when that platform will inevitably switch-to A/B on max/higher weapon load in Apr-Jul timeframe in any north-Indian airfield. Of course, HTFE, like F404 or any other western engine, wouldn't have such issues operating from western countries etc.
Kaveri will not have that issue - because it was way-ahead of it times, in deliberately keeping the brochure-quoted dry thrust figures low, but achieving it ALL indian conditions ... after all, a desi system designed by desi kallurams, you see.
Instead, it uses the peak TeT (1455 deg C) to make the HPC turn faster in those hot ambient condition, utilising the deliberately more air-mass available (a function of low BPR) for the HPC and maintain it quoted thrust dry figures.
In reality it would be operating more at TeT levels of 1250deg C regime, 90% of the time - it doesn't need to huff-puff to the higher and max TeT figures (and there goes the engine life), as it already has the adequate mass-flow available for achieving the 51KN dry thrust.
Of course, today there's huge cacophony of randi-rona-dhona about oh-so-almighty GE running its EPE/EDE and all those alphabetic-soup programs, while poor SDREs labour out the primitive-and-stone-aged Kaveri/Kabini.
But as is the usual nowadays, I have again digressed to a completely unrelated topic - I was wishing, again as always, to write-up a post on this very aspect, but as usual again lack of b/w meant, it's lying somewhere in hdd, maybe at 25-30% completion stage - SIGH!!!!
Back to topic ... question was HTFE can be scaled to a 30/48KN turbofan or not?
Answer is, no it can't without significantly changing the core ... because it didn't allow those "headrooms" in it's core design, instead choosing to chase the glamorous brochure figures.
My guess is, it can be tweaked to 27-28KN dry (so may be 37-40KN max Wet) with a better fan , but that'll be it.
To go any further, they will have to improve first the TeT to 1400deg C levels - and that means a brand-new core.
These temp-levels mean a whole paradigm of cutting edge technologies like DS or even SC HPT blades and vanes casting, convectional-cooling and what not.
I'm deliberately not mentioning TBC, as I think it already uses YSZ based uni-layer TBC (much like Kaveri/Kabini) - as without that achieving 1200deg C TeT on polycrystalline casted blades/vanes is next to impossible.
However they have an advantage there - unlike Kaveri, the contemporary kallurams in MIDHANI etc, have mastered bilayer LZ-YSZ TBC, that'd certainly give another 100-150+ deg C TeT advantage (all they need to master is the anti-spalding characteristics of fast rotating turbine etc).
So, if they can go to the relatively low-tech solid SC casted blades/vanes (Rodina-gifted-made-in-koraput-AL-31F ones) and come up with a bilayer LZ-YSZ TBC, they may as well touch the 1400deg C TeT figure - and thus make a lot of headway towards 30-32KN dry thrust figures.
But even then, they will still not achieved those dry-thrust figures, if they are not able to scale the OPR to atleast 20-21 levels - and that'll be a steeper challenge actually, as tinkering the HPC blade geometry etc for higher SPR, is highest level of rotor dynamics and CFD mastering "technology", that requires, well, pen-and-paper and some really smart and tenacious fellows - something that grand-mullah-enquoobuddin-gas-turbini (PissBUH) would attest.
This OPR increase, will also require a slightly higher mass-flow-thru-core to be allowed which will require a new inlet (higher dia) design (and thus a new, bigger Fan as well).
No easy meals, I guess!! But with all these in place it can and should achieve 38KN/50KN figures.
But what really is impressive about HTFE, and that gives me a lot of confidence about it, is the way 3D manufacturing tech has been utilised to cut down the design and development schedule. So these technical developments, though very tough, can still be achieved in a reasonable timeframe, I guess!!
Anything is fine.
