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

Abstract

The liner of a gas turbine combustor is a very flexible structure that is exposed to the pressure oscillations that occur in the combustor. These pressure oscillations can be of very high amplitude due to thermoacoustic instability, when the fluctuations of the rate of heat release and the acoustic pressure waves amplify each other. The liner structure is a dynamic mechanical system that vibrates at its eigenfrequencies and at the frequencies by which it is forced by the pressure oscillations to which it is exposed. On the other hand the liner vibrations force a displacement of the flue gas near the wall in the combustor. The displacement is very small but this acts like a distributed acoustic source which is proportional to the liner wall acceleration. Hence liner and combustor are a coupled elasto-acoustic system. When this is exposed to a limit cycle oscillation the liner may fail due to fatigue.In this paper the method and the results will be presented of the partitioned simulation of the coupled acousto-elastic system composed of the liner and the flue gas domain in the combustor. The partitioned simulation uses separate solvers for the flow domain and the structural domain, that operate in a coupled way. In this work 2-way fluid structure interaction is studied for the case of a model combustor for the operating conditions 40-60 kW with equivalence ratio of 0.625. This is done in the framework of the LIMOUSINE project. Computational fluid dynamics analysis is performed to obtain the thermal loading of the combustor liner and finite element analysis renders the temperature, stress distribution and deformation in the liner. The software used is ANSYS workbench V13.0 software, in which the information (pressure and displacement) is also exchanged between fluid and structural domain transiently.

Transient heat transfer between a turbulent lean partially premixed flame in limit cycle oscillation and the walls of a can type combustor

“…The effect of the solid deformation induced by the mechanical loads is neglected (i.e. u ୱ = 0) and hence no change in the shape of the solid and fluid domain is taken into account; this assumption is well supported with the reported very small deformation amplitudes of the solid body in the work done by Shahi et al [24], on the same combustor configuration.…”

Sensitivity of the Numerical Prediction of Flow in the LIMOUSINE Combustor on the Chosen Mesh and Turbulent Combustion Model

“…Note that the integrals are also spatial, which means that both effects, destabilizing and stabilizing, can occur in different locations of the combustor and at different times, so the stability of the combustor will be decided by the net mechanical energy added to the combustor domain. Indeed when the acoustic energy losses match the energy gain stationary oscillatory behavior is obtained which is referred to as the limit cycle oscillation (LCO) [25].…”

Sensitivity of Combustion Driven Structural Dynamics and Damage to Thermo-Acoustic Instability: Combustion-Acoustics-Vibration

“…Furthermore, together with the published research on the thermo-acoustic instabilities in the literature [1,[9][10][11][12][13][14], the coupled-domains within the thermo-acoustic feedback mechanism have been investigated to include the multiphysics such as combustion-acoustics [15,16] and acoustics-vibrations [17,18]. instabilities analysis to cover the two-way interaction of the fluidstructure [22][23][24], however, the results are not linked to structural damage conditions. This paper presents an investigation performed in a combustor test system to explore and assess the structural dynamics characteristics, under intact and damaged conditions, altered by the dynamic two-way interaction between the oscillating pressure load in the fluid and the motion of the structure under limit cycle conditions due to thermo-acoustic instabilities.…”