Title Page
Abstract
Contents
Nomenclature 15
Preface 17
Chapter 1. Introduction 18
Chapter 2. Hydrogen-enriched partially premixed combustor: combustion instability 21
2.1. Background and objective 21
2.2. Experimental and numerical method 23
2.3. Results and discussion 30
2.3.1. Flame structure 30
2.3.2. Mean flow fields 35
2.3.3. Combustion instability 38
2.4. Conclusions 50
Chapter 3. Hydrogen-enriched partially premixed combustor: flame transfer function 52
3.1. Background and motivation 52
3.2. Numerical approach 54
3.3. Results and discussions 57
3.3.1. Grid independence test 57
3.3.2. Flow response inside the fuel supply line 59
3.3.3. Flow response without external forcing 65
3.3.4. Reacting flow: mean flow field 68
3.3.5. Reacting flow: flame transfer function 70
3.4. Conclusions 74
Chapter 4. Multiple premixed combustors 75
4.1. Background and motivation 75
4.2. Numerical approach 78
4.3. Results and discussion 84
4.3.1. Case 1: Single combustor in open condition for validation of LES result 84
4.3.2. Case 2: A whole system with dual combustors with the cross-talk in closed condition 86
4.3.3. Case 3: Single combustor without the cross-talk in closed condition 99
4.3.4. Case 4: The asymmetry issue related to the cross-talk existance 100
4.4. Conclusions 106
Chapter 5. Dual-mode scramjet combustor with disturbance: reduced order analysis 107
5.1. Background and objective 107
5.2. Mathematical modeling 108
5.3. Results and discussions 112
5.4. Conclusions 119
Chapter 6. Conclusion 120
Bibliography 122
Abstract 132
Table 2.1. Initial conditions of the simulated cases in various syngas compositions. 29
Table 3.1. Boundary conditions for LES. 55
Table 4.1. Inlet conditions for each computational test. 81
Table 4.2. Inlet pulsation conditions. 101
Table 5.1. Flight conditions applied in the simulation. 113
Fig. 2.1. (a) Schematic of the model gas turbine combustor and detailed view of the swirl vane in the (b) partially premixed and (c)... 23
Fig. 2.2. Verification of the chemical kinetics with the previous results. 27
Fig. 2.3. Planar schematic of the partially premixed cylindrical gas turbine combustor. 30
Fig. 2.4. (a) Accumulation of the 3D profiles into a 2D image, (b) the accumulated image, and (c) the Abel-inversion image. 31
Fig. 2.5. Comparison of the partially premixed flame structure shown in the experiment and LES with the H₂ content of 25%, 50%,... 32
Fig. 2.6. Contours of the LES OH mass fraction results with different H₂ compositions in (a) partially premixed and (b)... 34
Fig. 2.7. Temperature contours superimposed with streamline in the combustor with (a) partially premixed and (b) premixed conditions. 36
Fig. 2.8. The time averaged (a) radial and (b) axial velocity profiles in partially premixed (dark line) and premixed (red line) conditions... 37
Fig. 2.9. Pressure spectra of the pressures inside the (a) partially premixed and (b) premixed combustor. 39
Fig. 2.10. Phase-locked pressure fields inside the gas turbine combustor with 6 phases in oscillation period. 40
Fig. 2.11. RMS pressure amplitude distribution in the unstable H₂/CH₄ result. 41
Fig. 2.12. FFT results for numerical pressure profile for increased H₂ composition (100% H₂) and reduced fuel flow rate (20kW). 41
Fig. 2.13. (a) Isosurface of OH mass fraction and (b) yz-plane OH mass fraction profiles of oscillating flame in four different phases. 43
Fig. 2.14. Temporal variation of normalized p' and q' profiles at the middle of the combustor in unstable case where the phase... 44
Fig. 2.15. H₂/CH₄ flame in phase 1 and 3 shown with streamline. 45
Fig. 2.16. H₂ flame shown with streamline. 46
Fig. 2.17. H₂/CH₄ flame with reduced flow rate shown with streamline. 47
Fig. 2.18. (a) Flame length measurement and (b) flame structure profile and stableness of three test cases. 47
Fig. 2.19. FFT results for the oscillation of equivalence ratio inside a swirler. 48
Fig. 2.20. FFT results for the flow rate (a) before and (b) after entering through a swirler. 49
Fig. 3.1. (a) Schematic of the model gas turbine combustor and (b) a detailed view of a swirler. 56
Fig. 3.2. Grid refinement shown with the blue region indicating the fuel supply system and the red region indicating the combustor.... 56
Fig. 3.3. FTF gain by LES and experiment compared with fine and coarse meshes. 58
Fig. 3.4. Contours of LES_IQ corresponding to phase 1 (0°) and phase 3 (180°). 59
Fig. 3.5. Experimental measurements and LES results for CTF as obtained at the outlet of the swirler. 60
Fig. 3.6. Velocity distribution inside the fuel supply system shown with the cases of (a) minimum and (b) maximum mass flow... 61
Fig. 3.7. The flow responses calculated at three different location of the fuel supply line for forcing frequencies of 50Hz (red line) and... 62
Fig. 3.8. Velocity distribution in the cross-sectional view at the location of (a) 0.03m, (b) 0.3m, and (c) 0.6m from the fuel supply... 63
Fig. 3.9. Oscillating vortices shown in the cross-sectional side view near the swirler inlet with the forcing frequency of 50 Hz. 64
Fig. 3.10. Oblique view of the flow distribution in the fuel supply system in the case with no forcing. 66
Fig. 3.11. FFT spectrum of the flow rate at the outlet of a swirler without forcing. 66
Fig. 3.12. (a) Decaying and (b) strengthening of vortices near the swirler inlet in the case without external forcing. 67
Fig. 3.13. Mean temperature profile inside a combustor. 68
Fig. 3.14. Profiles of the time-averaged (a) radial and (b) axial velocity components for the current simulations (lines) and... 70
Fig. 3.15. Instantaneous OH mass fraction fields for four different phases of 0°, 90°, 180°, and 270° for 50 Hz forcing frequency... 71
Fig. 3.16. Instantaneous OH mass fraction fields for four different phases of 0°, 90°, 180°, and 270° for 300 Hz forcing frequency... 72
Fig. 3.17. (a) FTF gain and (b) FTF phase predicted by LES compared with experimental results. 73
Fig. 4.1. Schematic of can-annular gas turbine combustors. 78
Fig. 4.2. Planar schematic of a single gas turbine combustor in the (a) open condition of Case 1 and (b) closed condition of Case 3. 82
Fig. 4.3. Selective grid refinements for resolving near wall turbulence in the present simulation. 83
Fig. 4.4. Dynamic pressure comparison inside the combustor (probe 1) for mesh independence test. 84
Fig. 4.5. Flame structure profiles in the open condition of Case 1: (a) calculated OH* mass fraction and (b) experimentally observed... 85
Fig. 4.6. Mean axial velocity profile in the closed condition of case 2. 87
Fig. 4.7. Symmetric streamlines plotted together with the mean temperature background. 88
Fig. 4.8. Profiles of (a) mean and (b) root-mean-square fluctuations of axial velocity for transverse planes of combustor 2... 89
Fig. 4.9. Fast Fourier transform results of pressure oscillations measured at (a) probe 1 and (b) probe 2 90
Fig. 4.10. (a) Temporal profile of pressure oscillation in the cross-talk and (b) the fast Fourier transform profile (black line) at probe... 92
Fig. 4.11. Time history of normalized pressure and heat release oscillations at probe 1. 93
Fig. 4.12. Time history of acoustic pressure measured at probes 1 and 2. 93
Fig. 4.13. Pressure oscillations shown in four different phases angle in the direction of the pressure wave. 94
Fig. 4.14. Injection velocity profile normalized with (a) mean inlet velocity and (b) local pressure and heat release rate at the... 95
Fig. 4.15. Isocontour of oscillating flame in four different phases for the H mass fraction of 5x10⁻⁵ 96
Fig. 4.16. Scatter plots of the heat release rate, plotted in four different phases where the results for fully stretched flame (180°)... 99
Fig. 4.17. (a) Fast Fourier transform results of pressure oscillation inside a single combustor (probe 4, red line) in Case 1 and dual... 100
Fig. 4.18. FFT of the pressure without (solid line) and with (dashed line) inlet pulsation obtained from (a) probe 2 and (b) probe 1. 103
Fig. 4.19. FFT of the pressure at the cross-talk (probe 4) without (solid line) and with (dashed line) inlet pulsation. 103
Fig. 4.20. Transient fields of velocity magnitude in four different phases. 104
Fig. 4.21. A comparison of inlet pulsation effect: magnified transient fields of velocity magnitude for (a) with and (b) without the inlet pulsation. 105
Fig. 5.1. Algorithm in the simulation module. 111
Fig. 5.2. Schematic of a computational domain 112
Fig. 5.3. (a) The concentration of CO₂ representing ignition delay and (b) ignition delay profile for various initial temperature. 113
Fig. 5.4. The thrust profile in case 1 condition. 114
Fig. 5.5. The thrust and thermal choking location in case 2 condition. 115
Fig. 5.6. The thrust and thermal choking location in case 3. 116
Fig. 5.7. Flow variables in the scramjet combustion mode. 117
Fig. 5.8. Flow variables in the ramjet combustion mode. 118