The Gas Turbine Research Establishment (GTRE) is a premier Defence Research and Development Organisation (DRDO) lab entrusted with the critical task of designing and developing an operational gas turbine engine for the Tejas Light Combat Aircraft (LCA). While the road has been long and arduous, FORCE visited GTRE to get a better understanding of the challenges faced by the team and the milestones that have been achieved till date.

Kaveri Programme

The Gas Turbine Research Centre as it was called way back in 1959 consisted of a modest team of 10 engineers, scientists and 20 technicians entrusted with designing a centrifugal type gas turbine engine generating 1000 kg (2200 lb) of thrust. This engine ran for the first time on a test bed at Kanpur in 1961, by the end of that year the entire establishment moved to Bangalore and was renamed as Gas Turbine Research Establishment (GTRE). From that infant stage, today, GTRE has grown to house more than 1,250 technical personnel whose primary responsibility is to design and develop an aero gas turbine engine for military applications besides carrying out advanced research in subsystems for the same.

The project ‘Design and Development of Kaveri Engine’ was sanctioned on 30 March 1989 is yet ongoing and has incurred an expenditure of more than Rs 3,000 crore. The programme can in hindsight be termed as having been highly optimistic considering the fact there was a complete lack of knowhow ranging from design and development of a modern aero engine to technology and materials, not to mention a nonexistent vendor base capable of supplying high quality aero components on a consistent basis initially. However, aero engine development world over has always been a technology-intensive and time consuming task and the lessons that have been learnt so far are sure to be put to good use in the coming years. The effort has also resulted in numerous spinoffs over a variety of applications and the creation of a large knowledge pool with regards to gas turbine engines and associated sub systems.

The Kaveri is a twin spool, low bypass ratio, augmented turbofan generating a dry thrust of 52 kN (11,690 lb) and reheat thrust of 81 kN (18,210 lb) weighing approximately 1250 kg. A quick comparison with engines that the Kaveri must match by the time it enters service before the end of this decade is given below.

The Eurojet 2000 and F414-GE-400 are already in a competition for the ‘Tejas’ engine contract while Snecma will partner GTRE in the quest to develop a higher thrust variant of the Kaveri engine. The Eurojet 2000 is a twin spool turbofan with an afterburner thrust of 20,000 lb and 13,500 lb without reheat weighing 1,000 kg. The GE F414-400 has a maximum reheat thrust of 22,000 lb and weighs 1,109 kg. The Snecma M-88-2 offers 17,000 lb of thrust with reheat and 11,250 lb without reheat and weighs 1977 kg. However a Snecma brochure does say that improvements could increase the thrust to 20,000 lb.
Interestingly, while the General Electric (GE) engine powers the twin engine F/A 18 ‘Super Hornet’ and the single engine Saab Gripen, the other two engines power twin engine fighters only. Also the GE and Snecma engines are used in fighters that also have naval variants in the ‘Super Hornet’ and Rafale respectively unlike the Eurojet 2000 which is used on the Eurofighter.

Challenges

According to director, GTRE, T Mohana Rao the, “materials required for a gas turbine engine are extremely complex. They have to be light and strong at high temperatures. An exotic alloy called Ti-64 is used for the low pressure compressor and parts of the high pressure compressor. Another alloy is used for the high temperature sections at elevated temperatures of 900 degrees centigrade for the high pressure compressor blades. Titanium, super alloys and maraging steel, all form essential components of an aero engine and a lot of these materials were developed for the Kaveri programme along with DMRL Hyderabad and Midhani. Now we have 12 important alloys for air worthiness and use on aircraft that have been certified by Centre for Military Airworthiness and Certification (CEMILAC) and RCMA. This has taken a decade to develop and we used to import all these materials previously.”

Some of the other crucial technologies that are required for a modern combat aero engine are single-piece bladed compressor disks (blisks), single crystal high pressure turbine blades, powder metallurgy disks, ceramic coatings and composite materials. These are essential to provide the high thrust, reliability and low weight demanded of present fighter engines. Many of these technologies are not available readily and the task of developing this type of technology in house has proved to be insurmountable. However, with the entry of Snecma one can expect the programme to have access to newer technologies.