Dynamic and acoustic analysis for a low Nox emissions combustor

This paper presents an approach to characterize the combustor structural dynamic behaviour under dynamic pressure load due to combustion instability. This activity has been developed in collaboration with AVIO S.p.A. product center of Pomigliano d'Arco that furnished us a prototype of gas turbine engine combustor chamber with architecture based on ASC (Axial Stage Combustor). The advantage of such an architecture is the versatility and adaptability at various condition of use (take-off, landing, taxi). Lean, prevaporized and premixed combustors are very prone to induce the combustion instability consisting in the lighting, turning o and re-lighting of the ame with a pressure load development that increases the Stress. Dynamic analysis has been performed in NASTRAN. The F.E.M. model has been validated through experimental tests with a modal approach and even pressure loads have been experimentally measured. The most critical load conditions occurs when the combustion instability excites the acoustic modes with consequent production of strong noise and vibrations and a HCF (High Cycle Fatigue) life reduction. We defined the acoustic modes through a F.E.M. approach and we evaluated the coupled Acoustic-Structural behavior.