Guy Norris/LOS ANGELES
General Electric has successfully completed initial tests of an upgraded GE90 compressor which is expected to yield specific fuel consumption (SFC) and temperature margin improvements on the Boeing 777-200ER, as well as act as a potential platform for new thrust growth.
Key to the improvement is the use of advanced "three dimensional" aerodynamic design methods on the vanes, blades and variable stators of the 10-stage high-pressure compressor (HPC). The HPC was combined with combustors and the HP turbine for a core test in GE's Evendale, Ohio site which has "just finished" according to Dick Ostrom, manager GE90 integration. "Based on core testing, the data we expect to get shows the 3D aero is delivering the compressor efficiencies that we predicted. Therefore fuel burn is on track as well as an improved EGT (exhaust gas turbine) margin," says Ostrom.
GE is also improving the engine by optimising fan and low pressure turbine clearances, as well as enhancing the HPT active clearance control system. Together with the 3D compressor, the improvements are expected to net up to a 1.7% SFC reduction and a 20° EGT margin. Of this, the compressor alone is expected to account for 0.9% to 1% of SFC and between 12° and 15° of EGT margin.
A full engine incorporating all the improvements was due to be "fired up" at GE's Peebles test site in Ohio as Flight International closed for press. "The focus will change a bit now. So far we're happy with what we've seen. Now we will have a real LP system running with the real HP system and our intent is to go back and run those tests we just did with the core," he adds. The company is hoping to flight test the engine on its 747 testbed at Mojave, California, early in the fourth quarter. Target certification date for the engine is December 1999, while the outline schedule for certification of the 777-200ER calls for completion of tests and entry-into-service around June 2000.
Although the improvements are aimed at longer life on wing (up to 10,000h longer based on an average 5h sector), reduced fuel consumption and flat ratings above 30°C, they also open up the possibility of a thrust increase with a "thrust bump". The package "may allow us to push up to near 93,000lb [415kN]," says Ostrom.
GE is conducting laboratory analysis on the bearing that failed in a GE90-powered Air France 777-200ER en route from Sao Paulo, Brazil to Paris, causing it to divert to Tenerife on 1 July. The failure was originally thought to have been caused by problems with the sump pump. GE says lubrication system contamination and a bearing failure have now been isolated as the cause. The company has instructed operators to interrogate the debris monitoring system regularly until the analysis is complete.
Source: Flight International
