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New 'Open Rotor' Engine Concept Might Cut Aviation Emissions by 20%

The un-ducted engine could be revived to help the aviation industry fight climate change.

New 'Open Rotor' Engine Concept Might Cut Aviation Emissions by 20%
Open rotor engine concept illustration Safran Group

Franco-American aerospace company CFM is developing an "Open Rotor" engine, or propfan, that could cut the aviation industry's emissions by up to 20 percent, a report by The Drive explains.

The idea originated with engine builder Safran — the French side of the aerospace firm — building a prototype to test the idea for a new un-ducted engine in 2017.

For Safran's prototype, the engine's blades were exposed to the air, with several adjustable stators enabling smoother airflow.

Using non-ducted fans allowed Safran to develop an engine with a larger fan surface area, making it more fuel-efficient.

Since that time, CFM has further developed the concept. The latest iteration of the open rotor engine has a single fan blade and a variable geometry stator placed behind the fan, making the new concept much quieter — Sarfran's prototype noise levels were compared to that of a turbofan.

Reviving the propfan to boost fuel efficiency

The firm says its design could produce approximately a 20 percent reduction in fuel consumption and emissions, all while maintaining a similar level of thrust to a ducted fan equivalent, as seen on most commercial aircraft.

Propfans were first experimented with as a potential response to the oil crisis in the 1970s, due to their ability to boost fuel efficiency. Though they never gained traction in mass-scale commercial flight, new aviation climate change regulations mean that such a design may one day be adopted at a wider scale.

Other steps by the aviation industry to curb emissions include Boeing's commitment to using 100 percent sustainable fuel by 2030 and Rolls-Royce's sustainable fuel engine tests.

The un-ducted engine isn't the only innovation Safran is currently working on. The French company's electric motors, called ENGINeUS, are being tested for VoltAero's new e-plane. Its hybrid propulsion and drive system is also being utilized by Bell Nexus to develop an eVTOL aircraft that could become Uber's first flying taxi.

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CFM has made sure to stress that its "Open Rotor" engine concept, developed as part of its Revolutionary Innovation for Sustainable Engines (RISE) program, still needs a lot more research before it can be considered for production.

In the meantime, the other half of the trans-Atlantic CFM, General Electric Aviation, is hard at work on the world's largest, most powerful jet engine, the GE9X.

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