I am meeting the new RM very very soon. I have known him personally for over a decade and so does him.
The K9 itself is more or less ready for flight testing. They only have to integrate it with the LCA and get it flying.
The original plan was to get it flying early this year, but the program went nowhere. And nobody knows why. Likely bureaucratic hurdles.
Similarly, my Tejas Mk2 vs Gripen NG article was picked up to made video word by word.
If S. Jha says something will come off it then I am willing to believe that.
Copied
[Part 1]
If you are only going by the metal temperature handling capability alone, then pls note the following:
1) The DS casted blades provide ~14deg C advantage over equiaxed polycrystalline casted blades (e.g. MAR M247, with approx metal temp capability of 950-1050 deg C).
e.g. Kaveri/Kabini uses DS casted blades (and vanes) using Supercast 247A (a variant of CM247LC which is itself derived from equiaxed MAR M247)
2) The 1st Gen SC blades provide another ~20deg C advantage, over these DS casted blades.
e.g. RR2060/PW1480/CMSX3/ReneN4 - 1060 deg C
3) The 2nd Gen SC blades provide another ~30deg C advantage over these 1st Gen SC casted blades.
e.g. PWA1484/CMSX4/ReneN5 - 1120 deg C
4) After that, the 3-5th Gen SC blades are produced with an aim of adding further ~30deg C advantage, as follows:
CMSX10 - 1135 deg C
ReneN6 - 1110 deg C
TMS80/MC-NG/DMS4 - 1140 deg C
TMS196 - 1150 deg C
Pls further note DMS4 is the DMRL developed suddha-desi SC alloys for turbine blade application - and it's almost shoulder to shoulder to best available (i.e. published).
---------------------------------------------------------------
Note - GE uses Rene-6 in F414.
DMRL developed a DS cast version of DMS4 called DMD4 - it was specifically developed for complex turbine aerofoil parts that are difficult to cast in SC form - and also as an cost-effective alternative. Further research continued with DMD4 by adding Ru and it was actaully proved to significantly improve the rupture life etc etc.
So it's obvious simply graduating from Equiaxed -> DS -> SC casting, it's not possible to reach the 1400-1650 deg C TeT capabilities of many modern turbofans.
Also the question obviously arises, how is the 1455deg C TeT of Kaveri achieved given the metal temperature capability of 1050 deg C of DS casted CM247LC based blades?
Answer, of course, and is well known in BRF as well is, from following two aspects:
1) Implementing various Blade Cooling techniques (e.g. Film/Convection cooling) - with this, a decent DS casted blade would provide for 200-250 deg C advantage (eg DS GTD 111) over metal-temperature-handling capabilities.
However a SC casted blade, again with a decently designed blade cooling techniques, would allow this advantage to go upto ~400 deg C.
2) Thermal Barrier Coating (TBC) application - Generally, the 7-8 wt% Yttria Stabilized Zirconia (8YSZ) TBC provides 150 deg C advantage (not to be confused with "thick layer"-TBC-application-capable-surfaces like the combustor walls etc, which can allow as much as 250-300 deg C advantages).
So Kaveri's DS blades gets to 1455 deg C via 1050 deg C (DS Cast) + 250 deg C thru blade cooling + 150 deg C via 8YSZ based TBC.
[Part 2]
Thus one assertion can be - that higher TeT is desired of, DS to SC graduation is inevitable in any modern turbofan development program.
But that is not because of incremental metal temperature capability addition etc (at best 20-60 deg C advantage).
The actual advantage of moving from DS to SC is not simply via the raw blade metal temp enhancement - it's more to do with thin section property optimisation that is inherent to SC processing. This thin section property optimisation (for e.g. in the thinnest section of a blade, the wall thickness (metal portion) is as small as 0.5 mm) allows for further intricate cooling passage designing etc which in turn allows drastic increase in overall TeT etc (200-250deg C of DS casted to 400+ deg C levels of SC casted blades).
This of course is in addition to the fantastic improvement of creep-resistance, tensile strength etc properties that entails from Equiaxed -> DS -> SC graduations (details in the Kaveri Sticky thread).
Also another aspect is advances in TBC ... recently we have seen reports of Indian Rare Earths Limited developing bi-layer TBC of Lanthanum Zirconate (LZ) over Yttrium Stabilized Zirconia (YSZ).
A bilayer top-coat consisting of Lanthanum Zirconate (LZ) over 8YSZ applied over "traditional" bond coat of say NiCrAlY enhances the temperature capability of the coating by >100deg.
So basically this advanced TBC if successfully applied to Kaveri's DS casted HPT turbine blades will easily bring the TeT to mid-1500deg C regime.
And if (and when) DMRL graduates to SC casted blades (and vanes), of the already developed DMS4 material, the absolute cutting edge TeT regimes of 1600+ deg C, becomes well within reach.
[Part 3]
A word about 8YSZ and LZ TBCs - note, Wiki has good level of general details wrt the TBC concept:
1) The "traditional" 8YSZ TBC (that has been ther for 4 decades now) allows for maximum surface temperature capability of about 1200 °C - beyond that degradation of the coating (in form of reduced strain tolerance and a decrease in thermal fatigue life of the coating) takes place due to changes in microstructure.
2) Lanthanum Zirconate (LZ), has much higher thermal and phase stability - close to 2000deg C.
It also has lower thermal conductivity and sintering tendency compared to YSZ.
(Thermal Conductivity - 2 W/m/K of YSZ vs 1.56 W/m/K of LZ)
3) LZ is also less oxygen transparent than YSZ, providing better bond coat oxidation resistance and minimises the growth of TGO (Thermaly Grown Oxide layer) - Wiki has good details about TGO and it's impact on TBC.
4) LZ has lower coefficient of thermal expansion compared to YSZ - so it can not be applied directly on the NiCrAlY bond coat. Therefore LZ is applied as a top coat material over YSZ forming a bilayer TBC. Furthermore LZ has good chemical compatibility with YSZ, making them a very good candidate for bilayer top coat applications.
5) Nano-structured TBCs often exhibit excellent performance compared with conventional TBCs such as adhesive strength, thermal shock resistance, thermal insulation, corrosion resistance and so on.
Furthermore nano-structured bi-layer is also expected to reflect certain amount of radiations (std phyzziks says wavelength of the reflected light is directly proportional to the particle diameter) thus providing a more effective TBC. So for reflecting heat in the near IR spectrum, TBC micro-particles needs to be of the order of 1-3 μm.
6) In India Nano-structured high purity grade YSZ and LZ are prepared from beach sand containing monazite and zircon following wet chemical route i.e. co-precipitation method.
7) DRDO has tested air-plasma sprayed TBC comprising of NiCrAlY bond coat (of 50 μm thickness), YSZ top coat (thickness 100 μm) and LZ top-most coat (thickness 50 μm) on to cast Ni-base super alloy substrates. The total maximum thickness was kept well below 250 μm.
8 ) DRDO has already assembled and validated the bi-layer YSZ-LZ coated flaps in an aero-engine for test cases involving rapid thermal transients, supersonic flow of combustion products, vibratory loads of about 4 ‘g’, sustained 1,000 h equivalent of engine operation and more than 30,000 nozzle actuations.
======================================================================================
All of these in Parts 1-3, still doesn't clarify following two questions:
1) why is DMRL not able to create SC casted blades for Kaveri?
2) and if it was not, able to what are these SC casted turbine blade images from various AI and other published literature that's doing round for many years now?
@randomradio, @vstol Jockey, @Gautam
[Part 1]
If you are only going by the metal temperature handling capability alone, then pls note the following:
1) The DS casted blades provide ~14deg C advantage over equiaxed polycrystalline casted blades (e.g. MAR M247, with approx metal temp capability of 950-1050 deg C).
e.g. Kaveri/Kabini uses DS casted blades (and vanes) using Supercast 247A (a variant of CM247LC which is itself derived from equiaxed MAR M247)
2) The 1st Gen SC blades provide another ~20deg C advantage, over these DS casted blades.
e.g. RR2060/PW1480/CMSX3/ReneN4 - 1060 deg C
3) The 2nd Gen SC blades provide another ~30deg C advantage over these 1st Gen SC casted blades.
e.g. PWA1484/CMSX4/ReneN5 - 1120 deg C
4) After that, the 3-5th Gen SC blades are produced with an aim of adding further ~30deg C advantage, as follows:
CMSX10 - 1135 deg C
ReneN6 - 1110 deg C
TMS80/MC-NG/DMS4 - 1140 deg C
TMS196 - 1150 deg C
Pls further note DMS4 is the DMRL developed suddha-desi SC alloys for turbine blade application - and it's almost shoulder to shoulder to best available (i.e. published).
---------------------------------------------------------------
Note - GE uses Rene-6 in F414.
DMRL developed a DS cast version of DMS4 called DMD4 - it was specifically developed for complex turbine aerofoil parts that are difficult to cast in SC form - and also as an cost-effective alternative. Further research continued with DMD4 by adding Ru and it was actaully proved to significantly improve the rupture life etc etc.
So it's obvious simply graduating from Equiaxed -> DS -> SC casting, it's not possible to reach the 1400-1650 deg C TeT capabilities of many modern turbofans.
Also the question obviously arises, how is the 1455deg C TeT of Kaveri achieved given the metal temperature capability of 1050 deg C of DS casted CM247LC based blades?
Answer, of course, and is well known in BRF as well is, from following two aspects:
1) Implementing various Blade Cooling techniques (e.g. Film/Convection cooling) - with this, a decent DS casted blade would provide for 200-250 deg C advantage (eg DS GTD 111) over metal-temperature-handling capabilities.
However a SC casted blade, again with a decently designed blade cooling techniques, would allow this advantage to go upto ~400 deg C.
2) Thermal Barrier Coating (TBC) application - Generally, the 7-8 wt% Yttria Stabilized Zirconia (8YSZ) TBC provides 150 deg C advantage (not to be confused with "thick layer"-TBC-application-capable-surfaces like the combustor walls etc, which can allow as much as 250-300 deg C advantages).
So Kaveri's DS blades gets to 1455 deg C via 1050 deg C (DS Cast) + 250 deg C thru blade cooling + 150 deg C via 8YSZ based TBC.
[Part 2]
Thus one assertion can be - that higher TeT is desired of, DS to SC graduation is inevitable in any modern turbofan development program.
But that is not because of incremental metal temperature capability addition etc (at best 20-60 deg C advantage).
The actual advantage of moving from DS to SC is not simply via the raw blade metal temp enhancement - it's more to do with thin section property optimisation that is inherent to SC processing. This thin section property optimisation (for e.g. in the thinnest section of a blade, the wall thickness (metal portion) is as small as 0.5 mm) allows for further intricate cooling passage designing etc which in turn allows drastic increase in overall TeT etc (200-250deg C of DS casted to 400+ deg C levels of SC casted blades).
This of course is in addition to the fantastic improvement of creep-resistance, tensile strength etc properties that entails from Equiaxed -> DS -> SC graduations (details in the Kaveri Sticky thread).
Also another aspect is advances in TBC ... recently we have seen reports of Indian Rare Earths Limited developing bi-layer TBC of Lanthanum Zirconate (LZ) over Yttrium Stabilized Zirconia (YSZ).
A bilayer top-coat consisting of Lanthanum Zirconate (LZ) over 8YSZ applied over "traditional" bond coat of say NiCrAlY enhances the temperature capability of the coating by >100deg.
So basically this advanced TBC if successfully applied to Kaveri's DS casted HPT turbine blades will easily bring the TeT to mid-1500deg C regime.
And if (and when) DMRL graduates to SC casted blades (and vanes), of the already developed DMS4 material, the absolute cutting edge TeT regimes of 1600+ deg C, becomes well within reach.
[Part 3]
A word about 8YSZ and LZ TBCs - note, Wiki has good level of general details wrt the TBC concept:
1) The "traditional" 8YSZ TBC (that has been ther for 4 decades now) allows for maximum surface temperature capability of about 1200 °C - beyond that degradation of the coating (in form of reduced strain tolerance and a decrease in thermal fatigue life of the coating) takes place due to changes in microstructure.
2) Lanthanum Zirconate (LZ), has much higher thermal and phase stability - close to 2000deg C.
It also has lower thermal conductivity and sintering tendency compared to YSZ.
(Thermal Conductivity - 2 W/m/K of YSZ vs 1.56 W/m/K of LZ)
3) LZ is also less oxygen transparent than YSZ, providing better bond coat oxidation resistance and minimises the growth of TGO (Thermaly Grown Oxide layer) - Wiki has good details about TGO and it's impact on TBC.
4) LZ has lower coefficient of thermal expansion compared to YSZ - so it can not be applied directly on the NiCrAlY bond coat. Therefore LZ is applied as a top coat material over YSZ forming a bilayer TBC. Furthermore LZ has good chemical compatibility with YSZ, making them a very good candidate for bilayer top coat applications.
5) Nano-structured TBCs often exhibit excellent performance compared with conventional TBCs such as adhesive strength, thermal shock resistance, thermal insulation, corrosion resistance and so on.
Furthermore nano-structured bi-layer is also expected to reflect certain amount of radiations (std phyzziks says wavelength of the reflected light is directly proportional to the particle diameter) thus providing a more effective TBC. So for reflecting heat in the near IR spectrum, TBC micro-particles needs to be of the order of 1-3 μm.
6) In India Nano-structured high purity grade YSZ and LZ are prepared from beach sand containing monazite and zircon following wet chemical route i.e. co-precipitation method.
7) DRDO has tested air-plasma sprayed TBC comprising of NiCrAlY bond coat (of 50 μm thickness), YSZ top coat (thickness 100 μm) and LZ top-most coat (thickness 50 μm) on to cast Ni-base super alloy substrates. The total maximum thickness was kept well below 250 μm.
8 ) DRDO has already assembled and validated the bi-layer YSZ-LZ coated flaps in an aero-engine for test cases involving rapid thermal transients, supersonic flow of combustion products, vibratory loads of about 4 ‘g’, sustained 1,000 h equivalent of engine operation and more than 30,000 nozzle actuations.
======================================================================================
All of these in Parts 1-3, still doesn't clarify following two questions:
1) why is DMRL not able to create SC casted blades for Kaveri?
2) and if it was not, able to what are these SC casted turbine blade images from various AI and other published literature that's doing round for many years now?
@randomradio, @vstol Jockey, @Gautam
There is a great deal of misreporting around the SC blades development. So let me write a long post.
The DMRL has created a Single Crystal blades way back in 2003. The blades were called DMS3, 3 here signifies 3rd generation. People often say DMS4 is the 3rd gen blade, that's wrong, 4 signifies fourth gen. I'll get to the DMS4 later.
When it first came around the DMS3 was described as :
"DMS3 is a third generation single crystal nickel-base superalloy developed by the Defence Metallurgical Research Laboratory. This alloy offers more than 80 deg C metal temperature advantage over the first generation single crystal superalloy CMSX-2 and about 8 deg C advantage over modern third generation alloys such as CMSX10. DMS4 has a nominal composition (in weight %) of: 67Ni-2.4Cr-4Co-5.5W-6.5Re-9Ta-0.1Hf-0.3Nb-5.2Al. The alloy has a density of 9.08 g/cc and a total refractory content of 21.4 wt. % including 6.5 wt. % Re to provide improved creep resistance. Mo and Ti have been completely eliminated in order to ensure adequate phase stability."
So was it put to use in Kaveri ? No it wasn't. Reason ? It had many deficiencies and GTRE wanted them removed. Deficiencies like a lack of a well designed cooling system, insufficient creep resistance etc. A lot of these problems are borne out of the fact that this was a "first time" development.
Things went silent for a long time. Then around 2013 DMRL stated that they have upgraded the 3rd gen SC blades into 4th gen standard, they have overcome the problems of the older blades. DMRL named the new 4th gen blades DMS4. This was around AI13 and got a lot of media attention. But as was expected of Indian media, they f**ked up the reporting. They reported DMSR4 as a 3rd gen SC blade.
But it seems the DMRL learned from previous experience. Just making a lump of exotic metal won't do, it has to be properly designed too with all the intricacies like cooling channels and physical properties like creep resistance. So to gather experience DMRL sought help from HAL's Koraput facility. The Koraput facility makes, among other things, the AL-31FP, RD-33 and R-25 jet engines for the Su-30MKI, Mig-29K/UPG and Mig-21 Bison respectively. Among these, the AL-31FP is the most continuously produced item. DMRL learned from HAL about the more practical needs from a SC blade, they eventually ended outdoing the AL-31FP's blades. Well to be fair, the AL-31FP, for all her power, is still an old engine.
This HAL Koraput-DMRL partnership continues till date. Check post no #375 on page no 19 of this thread for more info. HAL for some reason tries to play down the partnership. Maybe we played around with the AL-31FP without asking the Russians.
In any case, the DMS4 outdoes most contemporary 3rd to 5th generation SC blades in creep tolerance department :
Note : "CM" is designation for American made blades. "DM" is Indian. The DMD4 is a DS blade made by the DMRL that the Kaveri uses today.
Two main competitors of the DMS4 stands out : the American made CMSX10 and the Japanese made TMS 196. The graph above shows you the difference between the CMSX10 and the DMS4. Notice how the DMS4 is just barely better than the CMSX10, the Americans designate the CMSX10 as a 3rd gen SC blade. Our 4th gen(we use American classification of generation BTW) is just narrowly better, the American 4th gen/5th gen is not available in open source to do a comparison. But I'm sure the DMS4 wouldn't stand a chance.
The Japanese however have their own terminology of generations and it makes no sense to us. For example, their best SC blade so far was developed by the National Institute for Materials Science(NIMS) in Tsukuba, Ibaraki, Japan. The development was fully funded by the IHI Corporation and the material developed(called TMS 196) was used in the making of blades for the IHI Corporation XF5 afterburning turbofan used in flying the prototype of the Japanese stealth fighter Mitsubishi X-2 Shinshin. The Japanese call the TMS 196 a 5th generation SC blade.
Here is the twist, the XF5 produces less thrust with the afterburner "on" than Kaveri produces with the afterburner "off"(49KN vs 53KN). Suffice it to say, their 5th gen blade doesn't come close to our 4th gen. The TMS 196 can survive a max temperature of about 1150 deg C where as the DMS4 can easily survive 1200 deg C with out any cooling and TBC. The manufacturing process of DMS4 involves a multi-stage heat treatment at 1160 deg C, the TMS 196 wouldn't even survive that.
The Kaveri today has a Turbine Entry Temperature(TET) of 1455 deg C using DS blades that can survive 1050 deg C and other supplements. Replace the DS blades with the SC blades and we have ourselves a 150 deg C gain in TET which should push the overall TET to 1600+ deg C. That's supercruise territory. Not all engines with 1600+ deg C TET supercruise, but all supercruising engines need a TET over 1600 deg C. Other things mater a lot too. Like thrust to weight ratio, distortion tolerant intake and compressor and obviously an efficient design.
So why doesn't the Kaveri today use SC blades ? Well using SC blades with the engine as is and without making any design changes wouldn't allow us to extract maximum benefits of the SC blades. As such the thrust will increase but thrust to weight ratio, which is already not good, will fall further.
The Kaveri was designed from ground up with the DS blades and thus it is sub-optimal with SC blades. What can be done however, is to design the Kaveri from ground up with SC blades. Such an endeavour would be expensive and the Kaveri wouldn't remain Kaveri anymore. This is what the MoD has chosen, apparently. Read post #326, #327 and #337 on page no 17.
A number of tenders have been put out by GTRE regarding the developments of what is described as "Distortion tolerant compressor". Then in AI19 a model of the new compressor was put out.
The fan will achieve an overall compression ratio of 30:1, Kaveri had a compression ratio of 21.5:1. The fan was touted to be flow distortion tolerant, as in it can suck air from a serpentine intake and can survive supersonic oblique compression shock infront of the intake. Make of that what you will. As to why is that needed, I'll just leave these here :
AMCA experimental intake :
Ghatak UCAV experimental intake :
We will see what comes of it. In the meantime, DMRL hasn't been sitting there. They have tasted success with the development of the DMS4 and they want to continue on that.
Ramachandran Sankarasubramanian - Google Scholar Citations
Remember the HSTDV that was recently flight tested :
DMRL is providing materials for the scramjet combustion chamber, nozzle, outer skin etc. Basically any part of the HSTDV that is expected to heat up exorbitantly. Here is a breakdown of temperature each section is likely to face :
The HSTDV failed to sustain ignition of the scramjet engine. There will be another test in 4 months or so. However it does validate that DMRL has developed alloys that can survive temperatures of 2000+ deg C.
The problem today with Kaveri isn't material. Its design. The new engine to replace Kaveri will also feature a higher bypass ratio than the Kaveri's measly 0.16. Hopefully we will take lessons from what we've learned so far from the Kaveri and lets see if we can stitch up some new deal with the French. Some assistance in design will be very beneficial.
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