The Ofelia (acronym for Open Fan for Environmental Low Impact of Aviation) demonstrator program aims to establish the advantages of an Open Fan type architecture in terms of energy efficiency to meet the needs of the future generation of short and medium-haul by 2035. The French engine manufacturer Safran will work with 26 key European industrial partners, including Airbus, Avio Aero, GKN Aerospace, as well as research laboratories such as ONERA and universities in several European countries . OFELIA will benefit from European funding of 100 million euros from Clean Aviation. (This article was published in issue 2829 of Airlines and Destinations).
Ofelia or Unducted fan for aviation with low environmental impact
Safran Aircraft Engines will coordinate the demonstration program for new Open Fan engine technologies as part of Clean Aviation’s Open Fan for Environmental Low Impact of Aviation (OFELIA) project. The French engine manufacturer will work with 26 key European industrial partners, including Airbus, Avio Aero, GKN Aerospace, as well as research laboratories such as ONERA and universities in several European countries. The OFELIA consortium will benefit from European funding of 100 million euros from Clean Aviation.
Demonstrate the benefits of Open Fan
OFELIA’s objective is to demonstrate the advantages of an Open Fan type architecture in terms of energy efficiency to meet the needs of the future generation of short and medium-haul aircraft by 2035, and beyond. the aviation industry’s goal to achieve carbon neutrality by 2050. The Open Fan architecture aims to reduce fuel consumption and CO2 emissions by 20% compared to current engines. As part of Clean Aviation’s OFELIA initiative, Safran Aircraft Engines and its partners will bring to maturity up to TRL 5 a set of technologies relating to low-pressure systems, high-pressure bodies and advanced systems such as hybridization.
An A380 as a test bed
These developments will pave the way for ground and flight demonstrations that will take place in the middle of this decade on an Airbus A380 equipped with an Open Fan. The consortium will also ensure that this breakthrough architecture will be 100% compatible with sustainable aviation fuels (SAF) and hydrogen. “As a world leader in civil and military propulsion, our responsibility is to develop key technologies that will lead to more sustainable aviation,” said Michel Brioude, Technical and R&T Director of Safran Aircraft Engines. The Open Fan Architecture is the major innovation of our CFM RISE technology demonstration program, conducted with GE Aerospace, and is a key element to improve the energy efficiency of next-generation engines. We look forward to partnering with European industry leaders to shape the future of sustainable aviation,” adds Michel Brioude.
A concept tested in 1981
The concept of the Open Rotor is not new in itself. Called UDF or UnDucted Fan (unducted fan) or even Propfan (propulsive fan), this engine principle was tested in 1981, two years after the second oil shock, by General Electric and with the help of NASA. It was above all the prospect of consumer gains that was at the origin of the program. Subsequently becoming GE36, the technological demonstrator was tested in flight in 1986, first on a Boeing 727, then on a McDonnell Douglas MD81. Within the UDF adventure, what was not yet called Safran but Snecma took part in the development of the engine, which turned out to be extremely promising.
A bit noisy GE36
With its non-ducted architecture with counter-rotating propellers, the gains offered in terms of specific fuel consumption were there, but the GE36 struggled to meet the objectives in terms of acoustics. The major problem is then the noise, which spreads both around the aircraft and in the cabin, in the fuselage. Anyway, the project is abandoned when the OPEC embargo ends. But the significant gains obtained in terms of fuel consumption led Snecma to take the next step in the 2000s. With the experience acquired on the GE36, the engineers tried to imagine an architecture that would enable them to overcome the acoustic and dynamic constraints of this type of engine, to reduce vibrations and to adapt it to increasingly demanding environmental standards.
Open Rotor with M88 gas generator
In 2008, as part of the Clean Sky program, Safran took over the principle of the GE36 and perfected it, modernized it and brought it up to date. The Open Rotor was born, the much more efficient design tools make it possible to calculate the dynamics of a complete engine, with extensive work carried out at the acoustic level on the demonstrator. The latter used an M88 gas generator, found on the Rafale.
The main technological difference between the Open Rotor and the GE36 was at the level of the gearbox that the Safran technological demonstrator has and that the GE36 did not have. Positioned between the gas generator and the propellers, it thus made it possible to reduce the speed of the propellers. The GE36 had a direct drive and as a result the propellers had an extremely high rotational speed, which did not favor the reduction of acoustic emissions. The Open Rotor has also benefited from a particular treatment of the shape of the propellers, in order to minimize their interactions. The noise is then channeled by leaving it in the “tunnel” formed by the two propellers, so that it does not move radially.
3D woven composite
These propellers are made of 3D RTM composite materials, a technology specifically developed for the blades and the fan casing of the Leap engine, although the propeller blades of the Open Rotor are of larger dimensions than those of the fan blades of the Leap . The three-dimensional woven composite behaves in a different way compared to a metal blade. In the event of a bird strike, the blade deforms but does not break and the impact does not cause internal deformation. In view of these specificities and the experience gained, we therefore understand the decision to retain Safran as program coordinator.
More than 20 trials
OFELIA will include more than 20 tests carried out at partner facilities. Safran Aircraft Engines, Avio Aero and GKN Aerospace will work together to design and produce the Open Fan demonstrator components. Thanks to this unique collaboration between program partners, laboratories and universities, OFELIA will deal with specific subjects of the Open Fan technological maturation plan such as the whirl flutter, the unducted fan, the propellers and blades, the high-speed compressor, high-speed low-pressure turbine aerodynamics, high-power compact gearbox, lightweight engine components, combustion chamber emissions, high-pressure compressor aerodynamics and engine hybridization. In order to be ready for the second phase of Clean Aviation focused on flight testing, Airbus will prepare the preliminary file for the flight demonstrator.
“The OFELIA project is one of Clean Aviation’s 20 bold projects aimed at developing innovative solutions to power the next generation of sustainable aircraft. With the support of the European Union, European aviation has the power to lead the way towards climate-neutral aviation and set new global standards for safe, reliable, affordable and clean air transport,” said Axel Kerin, Executive Director of Clean Aviation.