Monthly Archives: October 2015

Presentation on Heat resistant coating for SCBs of AL-31FP (AeroIndia-2015)


Synopsis of Propulsion Presentations from AeroIndia-2015 Seminars.

The video: (Seminar 1 and 2)

Seminar 1

Title: Characterization of Heat Resistance Protective Coating (Aerofil) and Chrome-Alumniizing Coatings (Inner Cavities) of High Pressure Turbine Rotor Single Crystal Blades of AL31FP Aero Engine (Sukhoi MkI)

by G K Sadangi (HAL Koraput)


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The crux of the presentation is: Inner coating of Chrome Aluminising Coating. Outer coating of Al-Si-Y. The currently used inner and outer coatings on the SCBs show no significant deterioration even after 1000hrs (= TBO = half the Total Technical Life (TTL)). SO there can be scope for increase in TTL beyond current 2000hrs.

Q: Since the inner cavity has lower temperature, receives cooling air (>> no oxidation) and no gases coming from Combustion chamber (>> no suphidation). So inner coating needed??

A: Cooling air it at 1330 degC. Also cooling air impenges at high speeds on inner surface. So avoiding erosion is also one aim.

Q: Inspection on inner coating??

A: By taking cross section on sample blades from each batch. And Xray inspection.

Q: Any measurements on thermal gradient across the outer coating?

A: Neither the outer nor inner coatings are TBC.

Q: Repairability?

A: The coatings can be removed and re-applied without issue. Thats the beauty of it.


Seminar 2

Title: Development of Medium Thrust Class Turbofan Engine – HTFE25

by Devanathan, AERDC, HAL

Presenter emphasizes on two points:

  • Time should be the first priority.
  • Role of SME is of paramount importance.

Four technical aspects covered:

  • Multi-disciplinary approach for design
  • Systems Engineering Simulation/Concept
  • Digital Manufacturing
  • Testing
  • Currently (Aug-2015) manufacturing core of the engine and soon to be tested.
  • Planned concept is to develop core engine first and then develop full engine based on the platform it would be fitted to.
  • Emphasize on MD design iterations with quick iteration churning.
  • Secondary flows: First 3D simulations to capture flow characteristics and then use 1D models calibrated using the 3D simulations. 1D for unsteady simulations. Verification sing existing engine data done as a whole.
  • Idle = 70% rpm
  • 3D printing technology adapted right from concept stage. Main idea behind this was to reduce lead time to manufacture critical components in order to reduce risk of program. (Since only CAD input need to be changed to change component produced).
  • Casting to be replaced by 3D printing while forging, sheet metal processes retained.
  • Nozzle GV 3D printed with Inconel material – intricate cooling passages with additional which would not be possible with conventional techniques are easily made with 3D printing.
  • CC part- (flame tube section), Turbine blades, HPC all stator vane sectors, HPC tandem stator, gear box parts,

Pros of 3D printing:

  • Practically zero lead time for implementing design change in manufacturing
  • Full Freedom to designer
  • Possibility of lot of weight reduction by having internal cavities at non-critical locations.

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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.