Sami Aslam

High Performance Combustor Cloth Seals

Design of combustor seals poses a real challenge to designers who seek to achieve extended service life. In gas turbines with can-annular combustion systems, the combustor seals are used to seal the gap between the cans (transition duct) and the first stage nozzles. Combination of concentrated contact loads caused by thermal distortions and combustor dynamics limit the part service life. The introduction of flexible cloth seals has demonstrated the promise to extend the service life by 50% or more. However, to provide more air for combustion, and to satisfy decreasing NOx emissions limits, leakage reduction beyond existing levels is also required in addition to extending the service life. This paper describes the new combustor cloth seals designed to minimize leakage while extending the service life. Flexibility introduced by composite cloth assembly extends seal life by reducing contact load severity. Uniform slot contact minimizes leakage. To achieve maximum part life with minimum leakage rate, seal design has been optimized using statistical analysis tools. The systematic life improvement started with optimization of the metallic cloth. Once the process capability has been defined, the best vendor, weave and orientation were identified. Critical design areas have been identified through field inspections of prototypes. To minimize cloth wear in transition duct aft frame slots, seal slot engagements have been optimized using the tolerances on design parameters. The parameter values were assumed to be normally distributed within the tolerance bands. Inner-outer and side seal junctions have been redesigned to reduce contact load severity. Two separate Design of Experiments (DOE) series were conducted to develop load distribution transfer functions for both in-plane and out-of-plane cases representing the observed offset between neighboring * Copyright