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India Develops Near Isothermal Forging Technology For Aero-Engines

Image credit: Defence Research and Development Organisation

The Defence Research and Development Organisation (DRDO) has established the near isothermal forging technology to produce all the five stages of high-pressure compressors (HPC) discs out of titanium alloy using its isothermal forge press.

According to a press release, the technology has been developed by the Defence Metallurgical Research Laboratory (DMRL), a premier metallurgical laboratory of DRDO at Hyderabad. The technology is a step toward establishing self-reliance in aero-engine technology. With this development, India has joined the league of limited global engine developers to have the manufacturing capabilities of critical aero-engine components.

DMRL developed this forging technology by integrating various science and knowledge-based tools. The methodology adopted by DMRL is generic and can be tuned to develop other similar aero-engine components. A news report explained that fighter jet engines function by sucking in a large volume of air, compressing it rapidly in several stages, injecting aviation fuel into the air, and then setting it alight to create a high-pressure, high-temperature gaseous mix. That is expelled backwards through the exhaust, its reaction propels the aircraft forward.

To achieve this, jet engines have seven modules, which from front to rear are: the input fan, low pressure and high-pressure compressors, the combustion chamber, high pressure and low-pressure turbines, and the exhaust. An aero-engine requires finely tuned design and manufacture. The report added that for over three decades, the DRDO’s Gas Turbine and Research Establishment (GTRE) has spearheaded a multi-laboratory effort to design the so-called Kaveri engine, but with only limited success. DRDO is now exploring the possibility of using the Kaveri as a marine propulsion turbine for warships.

DMRL, which developed the technology to produce the five-stage HPC discs, is a laboratory without the facilities for bulk production. To meet the mass production requirements, DMRL has transferred technology to the defence public sector undertaking (DPSU) MIDHANI through a licensing agreement for technology transfer (LAToT). Using the isothermal forge press facility available at DMRL, Hyderabad, a bulk quantity (200) of HPC disc forgings pertaining to various compressor stages have been jointly produced and successfully supplied to HAL (E), Bengaluru for fitment into Adour Engine that powers the Jaguar/Hawk Aircrafts.

In India, the Adour engine is overhauled by HAL (E), Bengaluru under a licensed manufacturing agreement with OEM. Like in any aero-engine, the HPC Drum assembly has to be replaced after a specified number of operations or in case of damage. The annual requirements of these high-value HPC discs are quite large, warranting indigenisation. The HPC drum is a highly stressed sub-assembly and is also subjected to low cycle fatigue and creep at elevated temperatures. The raw materials and forgings for HPC drum are required to be of the highest quality which can meet the specified combination of static and dynamic mechanical properties.

The compressor discs produced using this methodology met all the requirements stipulated by the airworthiness agencies for the desired application. Accordingly, the technology was type certified and a letter of technical approval (LoTA) was accorded. Based on the exhaustive component level and performance evaluation test results, HAL (E) and the Indian Air Force cleared the components for engine fitment. Apart from DMRL and HAL (E), various agencies such as MIDHANI, CEMILAC, and DGAQA worked to establish the technology.

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