Trent family will benefit from UltraFan technology by 2025

Rolls-Royce intends to feed technology bricks from the UltraFan demonstrator engine into existing Trent programs within two to three years. Although UltraFan has just started ground tests, some technology will be available sooner rather than later. Trent family will benefit from UltraFan technology by 2025. “We are already bringing some of the UltraFan technologies across, including a new disk alloy. We believe we got a world lead in disk alloys. We spent eight years developing a new disk alloy that has got an incredible performance that we will introduce on the Trent engines to increase their time on wing. We intend to bring it to service in 2025,” said Simon Burr, Director of Engineering & Technology. Rolls-Royce shared various program updates during pre-Paris Airshow media briefings in Dahlewitz near Berlin. The engine maker said in May that it had ‘recently’ run the first and only UltraFan engine on Testbed 80 in Derby. Rob Watson, the recently appointed new President of Civil Aerospace, confirmed that the first run was actually done on April 24. “Testing is exactly going as we were expecting it to go. We are taking our time running up the power in the engine, as we obviously want to make sure we learn as we go. We are cautious but we will continue to push the envelope.” UltraFan is the first Rolls-Royce with a gearbox that allows the fan and turbines to operate at their optimum speed. It sits very compactly behind the 140-inch fan, the biggest seen on any R-R civil engine. The engine is designed for a power range of 25.000 to 100.000 pounds. The power gearbox has demonstrated that it can handle 100.000 horsepower. (Rolls-Royce) “It reached its mid-power. Idle fan speed is in the sort of mid-20s, we are well under 60 percent. We are running it about three times a week and are incrementing up,” Burr said. Full power will be reached before the end of the year. “Why not go to full power straight away? There are three reasons for that. One is that it is on the world’s largest and most sophisticated testbed as well as a completely novel engine. The last time Rolls-Royce ran an engine of this size with a new architecture was the RB211 in 1967. It is a big change because you are calibrated on how a three-shaft engine works. You have to build up your knowledge on an engine that behaves differently.” Planetary arrangement Compared to the Pratt & Whitney Geared Turbofan that has star arrangements of the gears, Rolls-Royce has opted for a planetary arrangement. “The star arrangement gets you to a certain gearbox ratio. The planetary arrangement allows you to push the ratio up. As you anticipate higher bypass ratios going forward, that enables you to reach even higher bypass ratios. To give you a feel: a Trent 1000 has a 10:1 bypass ratio, the GTF 12:1, and the UltraFan 15:1,” said Simon Burr. During a pre-Paris visit to Dahlewitz near Berlin, media were shown the dedicated test facility for the power gearbox that was first used in 2017. The facility cost €84 million. Here, the power gearbox demonstrated it can produce 64 megawatt/100.000 horsepower of power from the fan, way over the 50 Mw required for the engine. A number of gearboxes have been tested with different designs that were rebuilt. A dedicated rig has been built in Dahlewitz to test the power geared to the extremes. Tests will continue for the foreseeable future. (Rolls-Royce) “We have done a huge amount of testing. The rig can test all sorts of loads like bending loads, and running the gearbox backward or in a tilted position. You can see how the oil operates in different attitudes. A tremendous amount of work has gone into the bearings, for which we have dedicated test facilities,” said Burr. “Recently, we tested the gearbox to destruction. We ran the gearbox and starved the bearings with oil to make sure we understand the failure mode. Because when you are designing something as an engineer, you have to make sure that it can deal with any type of failure. All kinds of bird strikes on the fan blades and shock waves but also how the gearbox will behave.” “We did already simulate a flight to New York and back on a gearbox. We are taking it step by step to understand the full system. Gearboxes are typically very heavy because there is a lot of energy in there and the material is very rigid. You can’t use titanium like we like to do on engines. But we believe this is the net architecture to reduce fuel. If you can consume 25 percent less fuel, you have a very good business case,” Jan Schnitzler, head of the gearbox testing department in Dahlewitz. Testing will continue on the rig for the foreseeable future, says Schnitzler: “On the rig, we are always a little bit ahead on the engine. We will get the next changes in materials. We are developing new planetary gears that are lighter, will test them hear, then in an engine, and finally on an airplane.” Optimizing the engine Since the first tests of UltraFan on April 24, the fan and gearbox have been optimized to check how they respond to throttle movements. Also, the lean combustion systems have been set up to optimize the ratios between the injectors. The turbine case clearance has also been optimized. “We are working through this now before you get to full power. You don’t do those setups at full power, you do those at part and you can build up. But I am very, very happy. It has gone very well so far, but I am an engineer, so something can always surprise you. There is no prize for rushing.” The UltraFan engine has eighteen carbon composite titanium blades. (Rolls-Royce) Testing will be paused in the summer for a few weeks as upgrades are coming to Testbed 80. It will get X-ray facilities. “We will have the capability to take sections through the engine and check the clearances between the rotating parts. It enables you to calibrate the model. As you are driving efficiency, the gap between the rotating and static parts is a key thing that you want to be able to design for, manufacture, and control.” Scalable UltraFan is 25 percent more fuel efficient than the Trent 700 and 10 percent better than de XWB. It has been designed for a wide power range, which means the engine and gearbox are scalable. “If you start large, you can scale down across the range, particularly on the bearing design. We worked with our partner Liebherr on this,” Burr explained. “We tested a smaller gearbox but not in a planetary configuration yet. We did design studies and we have research programs, but we haven’t built one yet. You also have to think about where to spend your money. Once I have understood all the details of the physics of the large version, then I can scale it down. I need proof points to validate my money. So you need to be ready when someone says to you to build something a bit smaller.” And then there are new technologies that can be included in future UltraFan derivatives, like hybrid-electric power, hydrogen fuel cells, and direct injection of hydrogen. “The gas turbine will be around, whether you power it with jet fuel, sustainable aviation fuels (SAF), or hydrogen. That’s why we continue to invest to make the gas turbine better. It is a journey, we are not out of road.” Scaling down UltraFan is part of the HEAVEN project under Europe’s Clean Aviation program, which specifically looks at including hybrid-electric and hydrogen to get a 20 percent fuel burn improvement over current engines. However, HEAVEN doesn’t include actually building a smaller UltraFan engine.

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