PERFORMANCE STUDIES OF PASSIVE DAMPING TECHNIQUES USED TO SUPPRESS COMBUSTION OSCILLATIONS IN LPP COMBUSTORS

摘要

As part of an EU Framework IV programme, an investigation was undertaken into the design and performance of a variety of passive damping techniques aimed at reducing or eliminating combustion oscillations in an LPP combustor. Earlier in the programme, internal mapping of a 3-sector LPP combustor had to be temporarily suspended when significant structural damage was incurred as a result of high amplitude combustion oscillations. As a direct result, a review was undertaken to investigate damping technologies that were suitable for use within a combustion environment. Acoustic modelling techniques were used to support initial laboratory studies to establish linear absorber design rules. Following these studies, Helmholtz resonators, quarter wave tubes and a bulk absorber were tested in an experimental LPP combustor at atmospheric pressure. Attention was focussed on broadening the attenuation bandwidth whilst maintaining suitable damping performance. The bulk absorber achieved acoustic pressure reductions of up to 50%, whereas an array of combustor head mounted Helmholtz resonators achieved up to 90% pressure reduction.