Guy Norris/LOS ANGELES
GENERAL ELECTRIC IS studying the possible development of a dual-annular combustor (DAC) for its CF6 engine family, building on low-emissions technology developed for the GE90 and CFM56.
The company is considering the CF6 DAC as part of a broad-based attempt to take the initiative on low-emission engines. GE has already developed a dual dome combustor for the GE90, which gives the engine emissions of hydro-carbons (HC), nitrous oxide (NOx) and carbon monoxide (CO) around 50% lower than those set by international regulations. The company is also testing a DAC for the CFM56, which cuts NOx by up to 40%.
GE90 market development manager Vince DiGiovanni says that the main challenge is in developing a DAC design retrofittable to the current engine. The new combustor is deeper than the single annular combustor now used and would probably require the re-design of an entire module. "We're working on technology to do that, and it could be available within two or three years for the CF6-80C2 and E1 as well as others," says DiGiovanni.
German flag carrier Lufthansa is studying a fleet-wide retrofit of its CF6 engines with an improved low-emissions combustor developed initially for the UPS Boeing 767-300F competition. "We recognised the development of a low emissions combustor was a key element," says DiGiovanni, who adds that, before this, "...we were satisfied by the levels of NOx, but the CO and HC levels in the engine were not as low as we wanted them to be".
GE has sent a proposal to Lufthansa covering a retrofit plan which would involve replacing the existing single annular-combustor dome with a new version, as well as replacing the inner and outer cooling panels of the side walls.
"We change the cooling patterns in the inner and outer linings by relocating 60 holes in each," he says. The new layout resembles more closely the preferred thermodynamic-combustion pattern during cruise, when the reduction of emissions levels is most important.
The upgraded combustor, which will be installed in production engines from early 1996, cuts emissions of HC (relative to International Civil Aviation Organisation standards) by 12%, CO by 22% and NOx by 49%.
Source: Flight International
