Indranil wrote:JayS wrote:
Not dry but wet, in this context ie the intended Mil application. But in other context, as a high BPR civil jet engine for Business jet class like the Falcon series, it could.I think.
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.
Q: Why fan under loaded and HPC overloaded (looking at PR)?
A: Only core is being focused on right now. Fan/LPT design will change based on platform requirement.
Q: Surge margin for HPC targeted?
A: Not fixed. Normally its 14-19%.
Q: Which material for Turbine blades?
A: FOr IJT, TIT=1455K, so Inconel718 used. For AJT, something else can be used.
Q: What about Compressor?
A: Forged Titanium. And machined as blisks. Laser welding. First 4 stg = Ti, Last = Inconel718. HPC bolted – like in Al-55. First priority is to get Turbines and gearbox tested and validated (Other parts well within capability). Once this is done, core testing will go on for high altitude test etc, in parallel two (platform specific?) prototypes will be built.
Q: Why build 25kN engine when HAL license mfg same thrust class engines (adour-871 et al). Why not make Al-55 replacement?
A: Initially 20kN was proposed. Since Al-55 is ~17kN, a 20kN would have been good for IJT MK2. But the higher authorities went with 25kN. Wrt adour871 advantage in technology (smaller size, PR 11 vs 20, ~600mm vs ~450mm Turbine dia – huge turbine operating at lower rpm for Adour) , weight and size. So This engine while replacing Adour would give better performance. This engine can be used for Jagaur (which has 28kN engine) as well. Just need to change mounting points (and perhaps LP module?). Its very easy to adjust the design to various thrust levels by changing materials etc. Analysis already done. With similar core 35-40kN is achievable easily. SFC for this engine 0.72, better than older engines.
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.