Rolls-Royce Continues To Improve Whole Trent Engine Family
Rolls-Royce’s strategy of feeding technological developments from new programs back to established engines for upgrades or retrofit changes is creating a range of enhanced-performance (EP) packages being available to customers. Since the original Trent 700 entered service on a Cathay Pacific Airbus A330 in 1985 (the carrier received the 1,000th A330 four months ago), subsequent models have led to a tailored family involving common architecture among variants dedicated to specific airframes.
Airbus has introduced a suite of EP developments that raise production standards or contribute to upgrading of earlier Trent family designs. EP improvements have been developed for the T500 (which powers the Airbus A340-500), T700 (A330), T800 (Boeing 777) and T900 (A380)–the latter now emerging in an improved EP2 form.
Technology feedback began with the Trent 700 (T700), which spawned upgrades for the RB211-535 and many older -524G/H engines powering Boeing 757s and 747s, respectively. In turn, the T700 has benefited from development of both Trent 800 (powering the Airbus A330) and Trent 1000 (Boeing 787) variants, and technology from the Airbus A380’s Trent 900 has been applied to the Trent 500 (A340-500) and the new Trent XWB (A350XWB) is feeding back into the Trent 1000.
A good example of such feedback arises from T1000’s elliptical leading-edge (ELE) high- and intermediate-pressure compressor (HPC and IPC) blades, which lower fuel burn and are available for all Trent models, including upgrade kits for the T800EP and T500EP+. The blades’ sophisticated aerodynamics, which reduces airflow separation behind the leading edge, provides a 0.5- to 0.7-percent benefit to fuel consumption worth up to $200,000 per aircraft per year, said R-R. With the higher benefit being felt by T800 operators, because that engine is older and therefore relatively less efficient, the first T800EP engine entered service last month.
T700EP2 Earmarked for A330
Rolls-Royce (Stand 1845) is continuing to enhance the T700, as Airbus considers further improvements to the A330 twin-aisle twinjet, according to civil large engines head of customer marketing Peter Johnston. A T700EP2 package is earmarked to power higher gross weight A330s entering service from 2015. An EP2 kit, going through prelaunch phases in October, was expected to become a final package that could be launched this month, perhaps here in Dubai.
The T700, which has a 58-percent share of the A330 engine market and is being produced in ever-higher numbers, is now the leading variant in the RB211/Trent family with around 540 in service with 58 operators (having overtaken the 510 RB211-535 engines powering Boeing 757s earlier this year). R-R said new-build T700EPs provided over $250,000 fuel saving per year.
T700 EP2 characteristics include HPC and IPC stator-blade changes expected to offer 0.2-percent and 0.3-percent fuel-efficiency gains, respectively, as well as better low-pressure turbine (LPT) nozzle guide-vane (NGV) sealing and an improved “aero-standard [anti-]flutter bridge” that together provide a combined 0.2-percent benefit. Improvements in engine build standard, particularly clearances and sealing contribute a further 0.3-percent reduction in fuel burn.
The new NGV anti-flutter bridges would be introduced in LPT Stages 3 and 4, with the redesigned bridge being reduced in thickness by one third to one millimeter (0.040 inches) to provide better aerodynamics. Johnston said the work does not constitute a huge change, since modern engines can be improved only through the introduction of constant incremental development.
Previously, Trent 700 fuel burn on in-service engines had improved by 1.1 percent through introduction of a 2009 initial EP retrofit package. The kit included ELE IPC/HPC blades and optimized turbine-case cooling, changes also incorporated on new-build engines. Other developments, such as optimized blade-tip clearance, pocketless fan-spinner fairing, super-polished turbine hardware and HPC improvements, contributed to a 1.3-percent fuel-efficiency gain on new engines.
With the Airbus A380 having recently celebrated six years of operations and with about 60 Trent-powered examples in service with six airlines, R-R said the Trent 900 engine has “come into its own in the past 18 months.” It has been selected by 11 of the A380’s 17 customers and Johnston suggested the powerplant’s comparative reliability is better than that of the competing General Electric/Pratt & Whitney Engine Alliance GP7200.
Standard for Production Units
Following introduction of T900EP Block 1, the production variant since the beginning of 2012 that addressed early operational issues, the manufacturer is continuing improvement with the EP2–now running and destined to be the standard for all production units from early next year. Block 1 engines are delivering a 1-percent improvement in fuel consumption over original units and R-R is increasingly confident that EP2s can extend this further by up to 0.8 percent.
The new variant sports an optimized air system and IPC and also benefits from technology feedback. For example, engine-section ELE stator blades come from the T1000, while the latest Trent XWB contributes optimized turbine-case cooling and improved LPT sealing. Experience with both of those variants has influenced T900EP2 fan blade-tip clearance optimization.
R-R has five powerplants in the T900EP2 program. Engine serial number 91001 is being used to gather strain-gauge data and for X-ray assessment of engine structural movement during running, while T900 SN90004/11 is the type-test engine running European Aviation Safety Agency certification tests, for which highest temperature and rpm demonstrations were completed in mid-October.
Trials under way on SN 90005/9 cover air- and oil-system tests, bearing-load assessment and engine functional performance. The fully instrumented SN90006/5 (scheduled to have run at the end of October) is intended to demonstrate cyclic endurance and to assess behavior of the production standard powerplant (including all EP2 core modifications). Additional functional validation (with and without EP2 changes) is being performed on SN 91248, which is regarded as a production engine.
The “maturity” elements among EP2 improvements would be available for retrofit to earlier T900s at any maintenance shop visit and could also contribute to some performance packages applied to T500s, T700s, and T800s, concluded Johnston.