The first Pratt & Whitney PW4000 engines fitted with redesigned high-pressure compressor (HPC) vanes to combat surge problems have entered service on newly delivered Boeing 747-400s and 767-300s.
The redesign improves the surge margin by 6%, says P&W large commercial engines widebody engine marketing manager Peter Corliss.
"The kit is in production and a service bulletin to incorporate it in the field is being released," says Corliss, who expects over 2,000 engines to be retrofitted as a result.
The modification increases the surge margin by improving streamwise flow at the base of the vane using three-dimensional, computational fluid dynamics- based analysis techniques perfected by P&W for the compressor design in the PW4084 turbofan. Using the technique, P&W engineers devised a redesigned shape which redistributes the airflow toward the outer diameter gaspath wall at the blade tip area.
The change involves cutting back the trailing edge of the vanes at Stages 8, 10, 11, 12 and 13 in the HPC. Although the redesign was certificated in October 1999, the service bulletins are now going out for Boeing aircraft fitted with the 2.4m (94in) fan diameter engines.
"We are in the process of doing the Airbus and [Boeing] MD-11 bulletins now. They should be out by mid-year," says Corliss. New production engines have incorporated the changed compressor since December.
The change, which involves reworking the vanes in the specific HPC stages, can be undertaken during a standard shop visit.
· P&W has begun tests of a PW4168A equipped with the TALON II (technically achievable low nitrous oxide) low emissions combustor. The company plans to achieve US certification in November and European approval by April next year.
Source: Flight International
