A super-efficient “propfan” engine, which claims to save 20% fuel compared to conventional turbojet engines, is being developed and built by General Electric (GE) and CFM Rise, a joint venture that is owned 50:50 by Safran Aircraft Engines. This technology, also known as unducted fans or open rotor engines, is not new, but concern over fuel prices and the quest for net zero have revived the idea.

The propfan concept, which was initially envisaged in the 1970s, advanced significantly in the 1980s before being put on hold. With their sleek nacelles, air intakes at the front, and two sets of fan blades sticking out into the open in the back, they also have a peculiar appearance. However, they do not deliver on their claim of fuel economy.

Propfans are not a new technology

Resurrected GE propfan increases aeroplane fuel efficiency by 20%.Propfans typically have several, frequently strongly twisted, swept-back blades, with the rear blades twisted in the opposite direction as the front blades. To improve flow recovery, some types use counter-rotation, while others include stationary blades that function as variable-pitch stator blades.

A GE whitepaper claims that improvements in aircraft propulsion have been made possible by the use of new technologies that permit bigger fan diameters and greater bypass ratios. The propfan design achieves both capabilities by combining the fuel economy of a turboprop with the speed and capability of a turbofan.

Given the recent sharp rise in fuel costs, the aviation sector is now concentrating on lowering the carbon footprint of its energy-intensive operations. This has sparked a resurgence of curiosity about propelling effectiveness. While kerosene cannot entirely be replaced by batteries and hydrogen as an energy source, boosting the mileage has become essential. In response, GE announced a new UDF airliner engine named the “Rise” in 2021 in partnership with Safran Aircraft Engines.

GE asserts that their “Rise” engine will still offer 20% greater mileage than any other engine now on the market for a given quantity of energy, despite the fact that the aviation industry has significantly improved efficiency over the past few decades. Previous propfan designs have come under fire for being too noisy both on the ground and within the cabin. The CFM team still guarantees that the “Rise” engine is undergoing extensive testing to fulfil the strictest noise emission norms.

They offer significant fuel savings, however

“According to Mohamed Ali, vice president of engineering at GE Aerospace, “the industry can’t reach its net zero ambition by 2050 with the status quo incremental improvements in fuel efficiency.” Innovative technology are required. We think the timing is right for [an] open fan, a cutting-edge engine architecture that might enable the single-largest increase in generational engine efficiency yet attained by CFM. Our most thorough testing strategy to establish and develop these technologies for the future of flying supports this, he continued.

The “Rise” engine may be readily mounted on either the top or bottom of an airliner’s wing and is very versatile. The group has teamed up with Airbus to create an open fan demonstrator, which is planned to take to the skies in the middle of the 2020s. Until then, GE has produced a few prototypes and CFM has carried out about 400 ground tests. GE Aerospace has been working hard on simulations in the interim and just disclosed that it is using the “fastest supercomputer” in the world in a press release on Friday.

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