Acoustoelastic Interaction in Combustion Chambers: Modeling and Experiments

Abstract

To decrease NOx emissions from combustion systems, lean premixed combustion is used. A disadvantage is the higher sensitivity to combustion instabilities, leading to increased sound pressure levels in the combustor and resulting in an increased excitation of the surrounding structure: the liner. This causes fatigue, which limits the lifetime of the combustor. This paper presents a joint experimental and numerical investigation of this acoustoelastic interaction problem for frequencies up to 1kHz. To study this problem experimentally, a test setup has been built consisting of a single burner, 500kW, 5bar combustion system. The thin structure (liner) is contained in a thick pressure vessel with optical access for a traversing laser vibrometer system to measure the vibration levels of the liner. The acoustic excitation of the liner is measured using pressure sensors measuring the acoustic pressures inside the combustion chamber. For the numerical model, the finite element method with full coupling between structural vibration and acoustics is used. The flame is modeled as an acoustic volume source corresponding to a heat release rate that is frequency independent. The temperature distribution is taken from a Reynolds averaged Navier Stokes (RaNS) computational fluid dynamics (CFD) simulation. Results show very good agreement between predicted and measured acoustic pressure levels. The predicted and measured vibration levels also match fairly well.

Numerical study of coupled fluid–structure interaction for combustion system

“…The ability to predict the stability of a given burner is the centre of many studies, which can be experimental [2] or numerical [8][9][10][11]. The turbulent flame in the lean combustion regime in a gas turbine combustor generates significant acoustic pressure oscillations which induce liner vibrations that may lead to fatigue damage of the combustion system.…”

“…The numerical simulation of fluid-structure interaction (FSI) problems occurs in many engineering and scientific applications, ranging from airfoil oscillations or aero-hydrodynamics, blade flutter analysis in turbomachinery, to power generation in the design of gas turbine combustors [1,2].…”

Simulation of 2-Way Fluid Structure Interaction in a 3D Model Combustor

“…These oscillations may reach such amplitudes that they cause flame extinction, structural vibration, flame flashback and ultimately failure of the system [2,3]. Several coupled mechanisms are known to promote such interactions, for example, flame-acoustic wave interactions, flame vortex interactions , thermal-structure interactions, fluid-structure interactions, all of them may be present in a system individually or simultaneously [4][5][6][7].…”

Numerical prediction of interaction between combustion, acoustics and vibration in gas turbines

“…The liner wall is driven into vibration due to differential pressure oscillations and the liner velocities can reach high amplitudes due to the very low damping. These processes were investigated experimentally in the DESIRE test rig at the University of Twente [9,11]. This provided data for numerical code validation.…”