Kaveri Dry Heads for Flight Trials

– Srivatsa R.V

Kaveri-Dry Engine to Soon Touch the Skies

The Gas Turbine Research Establishment (GTRE) has slowly been preparing for their next big objective, and possibly their second potentially successful engine to come out from their lab after STFE. Yes, we are talking about the Kaveri-Dry that is slated to power India’s first stealth UCAV, the Ghatak.

Let’s start off by clearing off some confusion here, Kaveri as a name has been around for a while, and iterations of the same have resulted in different applications (UCAV, Aero, Marine, etc). To make the article more focused on what we are discussing, here are some common names,

Kaveri Dry = Kaveri Derivative

Flight Tests

Coming to the Kavery Dry now, as it nears the phase end of ground tests, the usual trend has been that an evaluation team from Russia visits the facility in GTRE, Bangalore and we run some tests while they are present. Once completed, a group of scientists and technical officers from GTRE will fly to Russia’s Gromov Flight Research Institute near Moscow, where the IL-76 LL testbed would mount our engine on 1 of 4 of its engines to start taxi and flight tests.

It is a crucial feat waiting to be accomplished, as many hopes are pinned on this, and so far we can tell you that Kaveri-Dry has not been disappointing. In fact, It has now achieved a 46kN thrust, versus the dry-rated thrust of 52kN.

Notable Changes Made to Kaveri Dry

New Inlet Fan

A new fan had to be designed for the inlet owing to the application requirements, fabricated using complex and indigenously designed Nickel and Titanium alloys in alliance with Midhani, HAL, and other private smaller players from Bangalore and Hyderabad.

  • Variable guide vane system to improve the matching of stages at part speeds, Specifically designed to meet unmanned vehicles applications with Serpentine Intake ( resist high distortion and surge tolerance).
  • The technology has been completely focused on UCAV applications, which also has made use of 3-D Stacking, to minimize shock-loss and control shock-loss boundary layer interaction, which incorporates wider chord-blades for flutter avoidance and increased distortion tolerance.
  • Has potential to operate at 105% over speed.
  • 100% indigenous from Raw Material sourcing to Component Realization
Source : Reach Defence
Kaveri-Dry’s newly redesigned blades are suited for high inlet distortion and surge tolerance.
Source : https://www.drdo.gov.in/technology-cluster-links/labs-products-detail/1591/173

Afterburner Component Removed

The Afterburner component which enabled it to have 81kN of expected thrust (76kN achieved) has been removed, and instead, a fixed nozzle has been put in its place, the manipulation of thrust will have to be done by methods such as Fluid Thrust Vectoring, notice the static nozzle outlet at the rear (right)

It is not needed for UCAV class aircraft, as the goal is to keep our stealth aircraft light, agile, and most importantly, reduce the RCS.

Observations

  1. A static nozzle gives us the opportunity to make it easier to cover the exhaust, leading to a reduction in heat signature, which in turn reduces over RCS profile of the aircraft. (Unlike the S-70 Okhotnik)
  2. The engine has repurposed its bleed system, will be used for De-Icing Mechanism instead.
  3. To reduce heat signature, the inlet air will be channeled through two routes, one pass through the compressor, combust, and will go straight out of the nozzle (Hot Air-Out), the other one flows through the casing of the engine (Cool Air-Out), also called the Bypass Duct which shields the inner exhaust note, which is relatively hotter. Overall IR detection levels go down with this style of bypass.
Image Source : Amiet R. Kashyap( https://twitter.com/Amitraaz?t=mOiSaNep9IK-lie4GUawCA&s=08 )
Infographic : Reach Defence

With these primary changes, what it will retain is, the state-of-the-art FADEC (Full Authority Digital Engine Control) made indigenously again by GTRE, we might see an upgraded version of it called the A-FADEC (Advanced) already in use perhaps.

What to Expect From the Tests

Some interesting things to note is that not the generic parameters such as how much thrust is it generating, But rather more important parameters like,

  1. Distortion Tolerance,
  2. Ability to Operate despite High Surge Pressure,
  3. Sustained Peak Endurance,
  4. New Fan Blade performance, etc.

The test schedule in Russia is also expected to not only test the engine in flight but also at various stages, such as

  • High Altitude Testing,
  • Bird-Ingestion Testing (probable) etc

The Kaveri-Aero seems to have stalled, but it has given birth to more opportunities than GTRE could have expected, the STFE, Kaveri-Dry have performed so much better than expected. Only goes to show that even the Kaveri-Aero could have been realized if the project was started say, a decade ago where the rock was being set for Indian Manufacturing and Fabrication standards with respect to Aero Engines.

Present Status

Design Validation Phase Completed,

Integrated with Engine (fan blades, that is),

Qualification Testing Near Completion

Appreciating The Efforts

This particular engine definitely shows the lengths to which GTRE has gone in implementing the lessons learned from the Kaveri-Aero along with so much more relatively new technology that has gone into it.

GTRE has made Stealth-specific enhancements to the engine based on requirements, such as designing it around a Serpentine Air Intake vane, reducing its heat signature, and the entire redesign of the fan blades to accommodate what the Ghatak might endure during the flight due to the nature of its air intake (Serpentine) and exhaust note (conformal with Fluid Thrust Vectoring).

Overall, from the ground tests itself, GTRE officials on multiple occasions have stated that GTRE test facilities have the capability to test the engine against 100s of test channels. This only shows the progress they have steadily, but slowly made towards realizing their key products. Its success will be a testimonial to the perseverance of the GTRE scientists and most importantly on-facility technical staff who assisted in the fabrication, assembly, testing stages of this engine.

Way Forward

The faster the Kaveri-Dry takes off, the faster Ghatak shall take off, in a move what can come as a surprise to others, is that Kaveri-Aero failed to integrate on to Tejas, and we had the back of GE-404x and 414x family choices to use along with it. The same goes for the Nirbhay missile where we used the NPO-Saturn family, and then slowly integrated the STFE onto it which was flight tested twice in the ITCM. In short,

  • LCA Program – GE-404 ordered, Kaveri-Aero planned (but failed)
  • Nirbhay/ITCM Program/KH-35 Uran -NPO-Saturn flying, STFE Planned and Test Flown( Success)
  • Ghatak Program – Only Kaveri Derivative Solution exists right now. nothing else on our plate.

We have to definitely take note of this, India has had programs delayed due to various reasons, but apprehension to use our own technology on the very first try is definitely one of them.

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