Technology insertion will lower maintenance costs, fuel consumption and emissions

CFM International has revealed plans to launch later this year a technology insertion "upgrade" of the CFM56-5B and -7B engines for the Airbus A320 and Boeing Next Generation 737 families respectively, marking the first significant application of the new features developed under the Tech 56 effort since its launch in 1998.

"The plan is to introduce it on the -5B and -7B flightline in early 2007, and to make it available as an upgrade kit for earlier engines built from 1998," says CFMI president Pierre Fabre, adding that a launch is being considered for later this year.

The package includes Tech 56-based technology improvements to the high-pressure (HP) compressor, the combustor, and HP and low-pressure (LP) turbines, all of which are aimed at reducing operating costs through longer time on wing, reduced maintenance and lower fuel consumption. The upgrade is also expected to lower nitrous oxide (NOx) emissions, thereby reducing airport taxes.

The upgrade would be introduced into the production line for delivery from early 2007 and for retrofit into the current fleet of more than 4,800 CFM56-5B/7B engines. Performance improvements will be derived mainly from the enhanced HP compressors, which are expected to have an increased pressure ratio of close to 15 compared with the baseline Tech 56 reference level of 11.4. At the same time it has a reduced number of stages, six compared with nine on the baseline compressor. The number of blades and vanes is also reduced by over a third to less than 1,000, reducing maintenance costs.

Turbine improvements are based on the Tech 56-validated "low shock" HP turbine blade contour enhancement. The third-generation singe-stage turbine design, tested on the Tech 56 counter-rotating dual shaft rig with a new LP turbine, had a 10% reduction in blade/vane parts count, and a higher stage loading of above 0.9 versus 0.86 for the reference turbine.

The LP turbine parts count, again thought to have been reduced by up to 19%, is also expected to contribute to the predicted savings. The newer aft-loaded blade design also incorporates a more durable LP turbine nozzle with modified cooling. The improved single annular combustor design will have improved cooling using techniques that were developed for the twin-annular pre-swirl Tech 56 combustor programme.

Originally aimed at a 50% margin to international CAEP 2 standards for NOx, smoke and other emissions, CFMI says the new unit will provide margin "to the CAEP 6 emissions regulations scheduled to take effect in 2008".

Source: Flight International