|Manufacturer||Gas Turbine Research Establishment|
The GTRE GTX-35VS Kaveri is a low-bypass-ratio afterburning turbofan being developed by the Gas Turbine Research Establishment (GTRE), a lab under the DRDO in Bangalore, India. An indigenous Indian design, the Kaveri was intended to power production models of the HAL Tejas fighter, originally called the "Light Combat Aircraft" (LCA), but it was officially de-linked from HAL Tejas program in September, 2008. It was announced in November 2008 that the Kaveri engine will be installed on HAL Tejas by December 2009.
In 1986, the Indian Defence Ministry's Defence Research and Development Organisation (DRDO) was authorized to launch a programme to develop an indigenous powerplant for the Light Combat Aircraft. It had already been decided early in the LCA programme to equip the prototype aircraft with the General Electric F404-GE-F2J3 afterburning turbofan engine, but if this parallel program was successful, it was intended to equip the production aircraft with this indigenous engine.
The DRDO assigned the lead development responsibility to its Gas Turbine Research Establishment (GTRE), which had some experience in developing jet engines. It had developed the GTX37-14U afterburning turbojet, which first ran in 1977, and was the first jet engine to be designed entirely in India. A turbofan derivative, the GTX37-14UB, followed. The GTRE returned to turbojet technology with the greatly redesigned, but unsatisfactory, GTX-35.
For the LCA programme, the GTRE would again take up a turbofan design which it designated the GTX-35VS "Kaveri" (named after the Kaveri River). Full-scale development was authorised in April 1989 in what was then expected to be a 93-month programme projected to cost 382 crores (nearly US$82 million at the time).
The original plans called for 17 prototype test engines to be built. The first test engine consisted of only the core module (named "Kabini"), while the third engine was the first example fitted with variable inlet guide vanes (IGV) on the first three compressor stages. The Kabini core engine first ran in March 1995. Test runs of the first complete prototype Kaveri began in 1996 and all five ground-test examples were in testing by 1998; the initial flight tests were planned for the end of 1999, with its first test flight in an LCA prototype to follow the next year. However, progress in the Kaveri development programme was slowed by both political and technical difficulties.
The Kaveri is a low-bypass-ratio (BPR) afterburning turbofan engine featuring a six-stage core high-pressure (HP) compressor with variable inlet guide vanes (IGVs), a three-stage low-pressure (LP) compressor with transonic blading, an annular combustion chamber, and cooled single-stage HP and LP turbines. The development model is fitted with an advanced convergent-divergent ("con-di") variable nozzle, but the GTRE hopes to fit production Tejas aircraft with an axisymmetric, multi-axis thrust-vectoring nozzle to further enhance the LCA's agility. The core Turbojet engine of the Kaveri is the Kabini, named after the Kabini River (which is a tributary of the Kaveri river).
The general arrangement of the Kaveri is very similar to other contemporary combat engines, such as the Eurojet EJ200, General Electric F414, and Snecma M88. At present, the peak turbine inlet temperature is designed to be a little lower than its peers, but this is to enable the engine to be flat-rated to very high ambient temperatures. Consequently, the bypass ratio that can be supported, even with a modest fan pressure ratio, is only about 0.16:1, which means the engine is a "'leaky' turbojet" like the F404.
The Kaveri engine has been specifically designed for the demanding Indian operating environment, which ranges from hot desert to the highest mountain range in the world. The GTRE's design envisions achieving a fan pressure ratio of 4:1 and an overall pressure ratio of 27:1, which it believes will permit the Tejas to "supercruise" (cruise supersonically without the use of the afterburner). The Kaveri is a variable-cycle, flat-rated engine and has 13% higher thrust than the General Electric F404-GE-F2J3 engines equipping the LCA prototypes.
Plans also already exist for derivatives of the Kaveri, including a non-afterburning version for an advanced jet trainer, and a high-bypass-ratio turbofan based on the Kabini core. Another concept being considered is an enlarged version of the Tejas with two engines fitted with fully vectoring nozzles, which might make the vertical tail redundant (the Tejas has no horizontal tail).
An indigenous Full-Authority Digital Engine Control (FADEC) unit, called Kaveri Digital Engine Control Unit (KADECU) has been developed by the Defence Avionics Research Establishment (DARE), Bangalore. The Combat Vehicles Research and Development Establishment (CVRDE) of Avadi was responsible for the design and development of the Tejas aircraft-mounted accessory gear box (AMAGB) and the power take-off (PTO) shaft.
Little information has been publicly released to date concerning the nature of the Kaveri's technical challenges, but it is known that the Kaveri has had a tendency to "throw" turbine blades, which required securing blades from SNECMA (as well as digital engine control systems).
Continuing development snags with the Kaveri resulted in the 2003 decision to procure the uprated F404-GE-IN20 engine for the eight pre-production Limited Series Production (LSP) aircraft and two naval prototypes. The ADA awarded General Electric a US$105 million contract in February 2004 for development engineering and production of 17 F404-IN20 engines, delivery of which is to begin in 2006.
In mid-2004, the Kaveri failed its high-altitude tests in Russia, ending the last hopes of introducing it with the first production Tejas aircraft. This unfortunate development led the Indian Ministry of Defence (MoD) to order 40 more IN20 engines in 2005 for the first 20 production aircraft, and to openly appeal for international participation in completing development of the Kaveri. In February 2006, the ADA awarded a contract to SNECMA for technical assistance in working out the Kaveri's problems. At that time, the DRDO had hoped to have the Kaveri engine ready for use on the Tejas by 2009-10.
The Kaveri is still in development, and reports indicate that it will be ready to fly by 2009. Testing and certification for use on the Tejas is expected to take some more time after that. Till then, the first two squadrons of Tejas will be powered by the GE404 engine.
Scientific Advisor to Defence Minister M Natarajan said nearly 90 to 93 per cent of the expected performance had been realised and the government had recently floated an expression of interest to seek partners to move the programme further
DRDO has reportedly been able to develop single crystal blades, which represent a major technological achievement for engine development. Production and integrating this technology into the engine is expected to take some more time.
Kaveri has already undergone 1,700 hours of tests and has been sent twice to Russia to undergo high-altitude tests for which India has no facility. The engine is also being tested to power the next generation of Unmanned Aerial Vehicles.
In September 2008, it was announced that the Kaveri would not be ready in time for the Tejas, and that an in-production powerplant would have to selected. Development of the Kaveri by the GTRE would continue for other future applications.
It was announced in November 2008 that the Kaveri engine will be installed on LCA by December 2009, apparently for tests only. On 28th nov 2009 a top DRDO official said kaveri engine would be ready for Tejas by march-april 2010
Development of the Kaveri engine was projected in 1989 to cost Rs. 382.81 crores (nearly US$82 million). In Dec. 2004, it was revealed that the GTRE had spent over Rs. 1,300 crores (around US$295 million) on developing the Kaveri. Furthermore, the Cabinet Committee on Security judged that the Kaveri would not be installed on the LCA before 2012, and revised its estimate for the projected total development cost to Rs. 2,839 crores (more than US$640 million). The DRDO, however, currently hopes to have the Kaveri engine ready for use on the Tejas by 2009-10.
The Kaveri program has attracted much criticism due to its ambitious objective, protracted development time, cost and time overruns, and the DRDO's lack of clarity and openness in admitting problems. Much of the criticism of the LCA program has been aimed at the Kaveri and Multi-Mode Radar programs.
There has been much criticism of the degree of realism in the DRDO's planning schedules for various elements of the LCA programme, most particularly for the Kaveri development effort. France's SNECMA, with over half a century of successful jet engine development experience, took nearly 13 years to bring the Rafale fighter's M88 engine to low-volume production after bench testing had begun; a similar timespan for the less-experienced GTRE would see Kaveri production beginning no earlier than 2009.
Another criticism has been DRDO's reluctance to admit problems in the engine and its resistance to involve foreign engine manufacturers until the problems became too large to handle.
Plans are also already under way for derivatives of the Kaveri, including a non-afterburning version for an advanced jet trainer and a high-bypass-ratio turbofan based on the Kaveri core, named as Kabini.