Guy Norris/LOS ANGELES
Rolls-Royce's Trent 8104 has exceeded 110,000lb (490kN) of thrust during initial test runs, proving the viability of a new swept fan blade design and other core enhancements and clearing the way for future growth, says the engine maker.
The 8104, rated at 104,000lb thrust for potential use on Boeing's ultra long range 777-200X/300X derivatives, had its first run on 16 December, 1998, and broke the 110,000lb barrier five days later. R-R director of engineering Mike Howse says that the engine "-has been flawless in its running".
R-R plans to continue tests of the 8104 and to add two more engines to the programme by mid-1999, but it is not expected to consider full production while questions still hang over the final thrust requirements from Boeing.
These have continued to drift upwards while the Trent 8104 was in development, and are up to the 110-114,000lb thrust bracket based on a recently defined 340,500kg (750,000lb) maximum take-off weight (MTOW).
"At the moment, the Trent 8104 is for the programme [777-200X/300X] that we've committed to, but, if Boeing gets to the point where they want a bigger thrust, we're pretty confident we will be in a position to do that. One of the reasons for the tests is to determine where we can get this engine to.
This is why we are excited about the swept fan and core items. The testing will give us the means of moving thrust forward and we will determine what we have to do in order to do that," says Howse.
The wide chord fan blades have been manufactured in the same super-plastically formed, diffusion bonded, process used for the current Trent 800, but are swept into a "sabre" shape. "We introduced the swept fan to get more thrust with the same diameter," says Howse, who adds that the change produces "2-3% more flow at a speed relative to the previous fan".
The sweep changes the alignment of supersonic shock waves on the blade itself and, for the Trent 800's existing fan diameter of 2.8m, produces an additional 10,000lb of thrust. The transition of the shock waves away from the blade tip towards the core improves fan efficiency by as much as 1%, and makes the engine "significantly quieter".
R-R is also thought to be considering increasing the thrust by increasing the effective diameter of the fan to almost 2.9m (114in) by moving it forward, enabling it to retain the existing nacelle and keep drag and cost down.
The first 8104 is being tested with three-dimensional (3D) aerodynamically designed intermediate pressure compressor (IPC) stators and all high pressure compressor rotors and stators.
Trent 800/8104 chief engineer Paul Craig says: "The intent is that we will test 3D rotors in the IPC as well." The swept blade design and the 3D aero features are being incorporated in the Airbus A340-500/600's Trent 500.
The engine also incorporates a revised seal segment in the first, high pressure, turbine stage. New blade coatings are also being tested, as is a third generation, single crystal alloy, material being used for the first time on the second, intermediate, turbine. An aerodynamically improved "high-lift" low pressure turbine (LPT) is also part of the hot section changes being tested in the 8104. The higher performance of each individual LPT blade means that fewer need to be used, reducing overall weight and boosting efficiency.
Source: Flight International