ROLLS-ROYCE is developing a new combustor for its RB.211-535E4B turbofan, which it claims will reduce the engine's nitrogen-oxide (NOx) emissions by up to 40%. The new variant is due to enter service, powering Condor's first Boeing 757-300, in the first quarter of 1999.

According to David Snape, chief of combustion-engineering civil projects at R-R, the new combustor is based on technology developed for the Trent 700, which was later further refined for the larger Trent 800 for the Boeing 777.

"We have taken that Trent technology, made some fairly minor changes to integrate it with [RB.211] -535 components, and put that into the E4," says Snape. "It will reduce NOx by about 40%," he adds.

The new "phase 5" combustor has 24 fuel injectors, compared with 18 on the existing "phase 2" device. Although turbine-inlet-temperatures are unchanged, says Snape, NOx is reduced because the gases have a shorter "residency" time inside the combustor at very high temperatures.

Initial rig tests of the new combustor have been carried out, and the first full-engine run is due in 1997. It will eventually be incorporated in all production -535s. R-R says that all other aspects of the engine's performance, such as fuel consumption and weight, will remain unchanged. The -535E4B is rated at 192kN (43,100lb) thrust.

Source: Flight International