Bøger af James Fayiah Willie

The main objective of this thesis is to analyze combustion instabilities in a matrixburner. The various tools that exist for analyzing thermoacoustic instabilities areapplied to the matrix burner with multiple flames. The principal goals are to determinethe primary causes of combustion instabilities in the burner and to exploreways of controlling such instabilities in order to prevent damage to the burner.To achieve these goals, the stability map of the burner obtained from measurementsis analyzed. This is followed by the analysis of the aerodynamics of the cold flowusing CFD. Results obtained from CFD are validated with PIV and LDA resultsfrom measurements. Critical are the centerline axial velocity inside the combustionchamber and the recirculation zones on the walls of the combustion chamber andthose between the various slots of the matrix burner.Cold flow simulations are followed by reactive flow simulations for both gaseous andliquid fuels. A detailed atomization model is developed for the liquid fuel case fromexperimental data. Two combustion models, namely, the combined finite rate/eddydissipation model and the finite rate chemistry model are compared in the CFDsimulations of combustion instabilities and validation with measurements are done.The latter is chosen over the former because it accounts for chemistry and it is notnumerically dissipative. Two CFD softwares, Fluent and CFX are also compared todetermine which is better at capturing acoustics. System identification using CFDis used to determine the flame transfer function and the acoustic transfer matrix.This is followed by the use of acoustic forcing and fuel modulation on the primaryand pilot in order to limit the amplitude of the instabilities inside the matrix burnercombustor.The 1D acoustic network is used to determine the longitudinal eigenmodes of thematrix burner. This is followed by the use of 3D finite element method (FEM) andfluid-structure interaction (FSI) to determine whether a coupling exist between thefluid and structure of the matrix burner combustor and vice versa.Finally, Full harmonic analysis is performed for the rectangular combustor and theresults obtained are validated with analytical results. This is followed by the 3Dstructure modal analysis of the full matrix burner test rig.