Russian engine specialist Aviadvigatel has made substantial changes in the configuration of its prospective PD-14 turbofan to enhance its performance and variability.
The firm is steering the PD-14 development project, aimed at creating a family of engines to power Irkut's medium-range MS-21 twinjet.
While retaining the core engine's two-shaft, two-bypass architecture, Aviadvigatel has decided to revise the location of particular engine modules.
"The key move involved the accessory drive gearbox," says Aviadvigatel deputy director and PD-14 chief designer Igor Maksimov. "We opted to put it under the nacelle cowl rather than under the gas generator. This ensures a steadier thermal regime and reduces temperature-related risks for oil lines and cooling systems.
"There is now more room inside the nacelle for rejigging other modules," adds Maksimov. "So it is easier to modify the baseline engine configuration and meet thrust requirements of stretched and shortened MS-21 variants."
Aviadvigatel has introduced an array of innovations to enhance service life and slim down all core engine components.
Maksimov explains: "To reduce weight, we've thoroughly re-designed the low-pressure turbine. It has become smaller and lighter. We've also worked in improvements stemming from the latest aerodynamic research. As a result, we've bumped up the turbine's efficiency."
In cooperation with domestic engine makers Perm Motors, UMPO and Motor, Aviadvigatel has begun the assembly of two modern low pressure turbines for the PD-14 prototype. One will be tested at its own laboratory and the other at the Central Aeroengine Institute (TsIAM) in Moscow.
Both Aviadvigatel and TsIAM have completed tests of the combustor prototype. Maksimov says these checks, which were also carried at a high-altitude test facility, validated all pre-test predictions in terms of emission and performance data measurements.
To further reduce risks, Aviadvigatel is co-operating with the Ukrainian engine design bureau Ivchenko-Progress in developing an alternative combustor. The partners plan to start testing the prototype this year - initially on a designated test-bed and then within a demonstrator engine.
If the jointly-developed prototype proves to be a better solution, Maksimov does not rule out that Ivchenko-Progress-affiliated engine manufacturer Motor Sich could become a major supplier of combustors for the PD-14.
Test runs of the technology demonstrator engine are scheduled to begin in the third quarter of 2013. Maksimov notes that the MS-21 project envisages - for the first time in Russia - that the engine developer is also in charge of developing the turbofan nacelle.
"Under our agreement with Irkut we bear an overall responsibility, from designing the engine to customer specifications and selecting suppliers to certifying and providing after-sales support," says Maksimov.
"We've already defined nacelle configuration. It features sliding panels rather than hinged cowl doors. This makes for a lighter and more rigid nacelle frame. It is also better from the maintainability standpoint.
"In addition, key nacelle components, such as air intakes, thrust reverser grid and cowl panels will be made of carbon-fibre reinforced plastics. Overall, composite materials will account for up to 60% of nacelle weight."
Full-scale engine nacelle tests are scheduled to begin in early 2014. By then, Aviadvigatel plans to have finalised the selection of second- and third-tier suppliers for the PD-14 serial production.