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.
Chris Young
Open rotor engine concept illustrationSafran 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.

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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.

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.