Rolls-Royce is preparing to introduce an upgraded version of its Trent XWB-84 turbofan that it expects to deliver a 1% improvement in fuel burn efficiency for the Airbus A350-900 airliner. The company aims to achieve certification later this year for the first production example of a modified engine now undergoing assembly.
The upgrade, which Airbus flight-tested on an A350, centers on aerodynamic improvements that have resulted in efficiency gains in the XWB-84’s compressor system. By redistributing the flow of air through the high-pressure turbine (HPT), Rolls-Royce engineers have reduced operating temperatures.
“The engine runs much cooler now and so it's more durable,” Rolls-Royce group director of engineering, technology, and safety Simon Burr told reporters at a briefing ahead of this week’s Farnborough International Airshow. “We took the engine and instrumented it [to assess] 2,500 parameters, which resulted in a lot of change to the turbine system and upgrades to the fans for better cruise altitude performance.”
Rolls-Royce will make available the new XWB-84 as an option for operators of new A350-900s. In addition to flight tests, engineers have subjected the engine to endurance testing at the company's ground test facility at Derby in the UK, where it ran a 2,800-hour hot-cycle test.
The fuel efficiency boost to the XWB-84 benefits from part of a £1 billion ($1.3 billion) investment in improvements to the Trent family, which has been in service since the 1990s. Rolls-Royce expects the changes to boost the durability of the turbofans on the wing.
The upgrades include a disc alloy to both the XWB-84 and the Trent XWB-97 engine, which powers the larger A350-1000. Burr explained that the RR173 super alloy introduces an improved safety margin that gives operators the option of running engines at least 50 kelvins hotter or extending service life.
Boosting Time On Wing Performance
With the XWB-97, the company's objective centers on doubling the permitted time on wing in challenging operating environments, such as in the Middle East, where extreme heat and sand can pose endurance issues. Rolls-Royce already has increased the temperature margin and enhanced turbine case cooling to support longer in-service times.
The company has added a new coating for HPT seal segments resistant to calcia-magnesia-alumino silicates, which can damage engine components. Rolls expects to make the upgrade available for HPT blades later this year. The third phase of the work, scheduled for rollout in 2028, will include a modified HPT and combustor to reduce metal temperatures with a new ceramic matric composite seal.
“The interface between the engine blade and the case has been running hotter than we’d modeled,” Burr explained. Efforts to resolve the problem have involved extensive rig testing at the Rolls-Royce Testbed 80 facility in Derby, where exercises have included blasting sand into an engine to replicate desert conditions. The manufacturer consulted with PhD-level geologists to ensure that the sand mix used directly mirrored the composition of sand found in the Middle East.
Well-documented reliability issues with the Trent 1000 turbofans that power Boeing’s 787 widebody airliner have prompted Rolls-Royce to introduce a new HPT blade already in service with the Trent 7000 on the A330neo aircraft since September 2022. “We lost market share because it simply wasn’t durable enough,” Burr acknowledged.
Rolls-Royce’s engineering team now plans to start flight testing the new Trent 1000 blade in August using its 747 testbed aircraft. Following initial certification by EASA, the company expects to deliver the first of the new design in early 2025.
Applied on the Trent 7000, the design’s increased cooling airflow has reduced blade metal temperatures by 45-deg C (113-deg F). Changes include additional mid-chord holes and widening of existing holes, improvements the company plans to make retrofittable across the Trent 1000 fleet.
On the commercial front, Rolls-Royce predicts this year will show a return to pre-2019 market conditions, with increased engine deliveries and growing flight activity driving demand for product support. Recent new orders have included Trent XWB purchases by Turkish Airlines, Delta Air Lines, and Japan Airlines, as well as a Trent 7000 order from Vietjet. Newcomers to the cohort of Trent operators include Asian operators IndiGo, EVA Air, and Korean Air.
According to Rolls-Royce's chief customer officer, Ewen McDonald, a boom in express delivery demand continues to underpin growth in the air freight sector, reinforcing the engine maker's position on both the new A350F model and conversions of A330 passenger airliners.