The CFM RISE* program announced in June will demonstrate and mature a range of new, disruptive technologies for future engines that could enter service by the mid-2030s. The program targets more than a 20% reduction in emissions compared to today’s most efficient engine, in addition to including open fan architecture and hybrid electric capability. Also in scope is 100 percent Sustainable Aviation Fuel and Hydrogen capability.
Already CFM is evaluating several promising architectures as part of the technology maturation plan. The most ambitious architecture — and the one that will yield the greatest benefit — is the open fan. For GE, Safran and Avio Aero, open fan architecture has roots in experimental programs and technological developments from the 1980s, first with the GE36 (the very first experimental “open fan” engine that flew to the Farnborough Air Show in 1988). And again in the 2000s as part of Europe’s largest R&D program, Clean Sky, with the SAGE project for a jet engine called Counter-Rotating Open Rotor, for which Safran and Avio Aero teamed up for validation tests.
This is why for the RISE program — after a 40% reduction in fuel consumption and CO2 emissions achieved by the CFM engines over the last 40 years — European aeronautical R&D is more than just a starting point; it is a fundamental element that brings technological contributions that have been matured over a few decades. This technology has been an important part of Luca Bedon’s, Head of Advanced Technologies at Avio Aero, professional path.
The RISE program opens a new era in commercial aviation, what does it represent for Avio Aero as the European outpost of GE?
The RISE program is the result of a ‘journey’ that began a few years ago, aimed at consolidating the results of technological investments that have produced a distillate of technologies on which the next generation of CFM engine architectures is based. Avio Aero has been present from the very beginning in this process. Now that we are about to enter an important phase of execution of the technology roadmap, our expertise in mechanical transmissions and turbines will be decisive in achieving RISE goals. But our involvement will not be limited to our historically recognized expertise; rather, it will extend to the entire engine. For example, helping the combustor provide even greater benefits to the entire propulsion system. As part of GE Aviation’s Advanced Technology pivot in European, the overall impact on the RISE program will be even broader, from the compressor to electrical machine integration. Virtually all GE Aviation sites in Germany, Poland, and Turkey will be involved.
These are two very different, but equally important, ventures. Through the SAGE programs we created the foundation for our roadmap on power gearboxes for turbofan engines, both for ducted engines (meaning engines enclosed by their own nacelle) and open fan configurations. We have directly experienced the complexity of these systems by testing them to their limits… and sometimes beyond. All this learning is critically important in directing the RISE roadmap. Thanks to IRON, on the other hand, we have had preliminary design experience at the engine level with open fan architecture. In fact, the program demonstrated the superiority of the solution based on a single rotating fan compared to the two counter-rotating fans. It is a simpler and, at the same time, more efficient s olution. This has allowed us to understand engine-related issues in a much more in-depth manner, including integration assessments with the aircraft operator, aspects that have expanded our systems capability exponentially.
Gearboxes and turbines are central components to RISE technology and, at the same time, are modules for which Avio Aero is considered a world leader. After producing the largest power transmission in the western world for the TP400, what’s new for these two modules in the RISE program?
Let’s say that these modules, given what has been done so far, retain little more than the name. The high-speed low-pressure turbine has a power gearbox between the shaft and the fan. This solution allows the turbine to turn much faster than traditional designs and, therefore, achieve higher levels of efficiency. Is it all so straightforward? Obviously not… The high centrifugal load to which the vanes are subjected under these conditions makes the aerodynamic and mechanical design particularly challenging. Again, the SAGE experience on Clean Sky helps; we have designed and tested an initial configuration of this type of turbine in the open rotor demonstrator developed with Safran. Talking about the gearbox, we are in a situation that is not so different. Considering the reduction ratio and the power involved, we are taking a new approach in terms of power density compared to what we have done before. To achieve the desired results, we are advancing the technological development of new-generation materials and processes for gears and bearings.
Today, decarbonization is the ultimate goal of our sector, something which Avio Aero has studied, developed and heavily invested in for years. How does the RISE program fit into our vision and future offerings for sustainable aviation systems?
The decision to evaluate an open fan configuration as part of the RISE demonstration plan stems from the imperative to make aviation sustainable and ensure we keep the dream of flight alive for future generations. RISE technology can deliver a 20% reduction in fuel consumption compared to the current generation, which is twice what generation-over-generation products have achieved historically. Even more relevant is the fact that this reduction in fuel consumption is crucial to enabling the adoption of the alternative fuels of the future, which, today, are limited by production capacity and price dynamics. Even more significant is the impact of the potential adoption of hydrogen as a fuel to replace jet fuel. RISE foundational technologies are key to overcoming the same limitations that characterize SAFs (Sustainable Aviation Fuels), as well as the difficulties related to integrating hydrogen, namely the greater volume occupied by hydrogen and the challenges of housing it in the wings. An ultra-efficient engine allows us to reduce the amount of hydrogen on board, limiting the impact on aircraft range, as well as the number of passengers it can carry.
What are the next steps for the RISE development program and what do we need to make this technological project tangible? That is, to achieve a truly sustainable balance for the environment, as well as for the economy?
As I mentioned earlier, RISE technology was being developed long before the public announcement. The program is now in full swing and, in the coming months, we will see an increasing number of technology demonstrations of increasing complexity really come to life, until the full engine-level demonstration both on the ground and in-flight, scheduled for sometime in the mid-2020s. Engine-level testing is a key to determining the reliability of an ambitious foundational technology demonstration like the RISE program, and the plan is to complete these tests over the next few years. The timeframe is consistent with the new European program Clean Aviation, for which we are working hard to offer these technologies as the flagship of the program. The success of a product is no longer measured in relative terms with respect to competitors, but in absolute terms with respect to climate neutrality objectives. For this reason, the CFM RISE Program represents the level of investment and commitment needed to address the challenges of sustainable development. In this sense, GE and Avio Aero have accepted this challenge and believe that this will act as a driving force for the entire aviation research sector, stimulating discussions, and accelerating the introduction of products and solutions for decarbonization.
*RISE is a registered trademark of CFM International, a 50/50 joint company between GE and Safran Aircraft Engines