Etude de la combustion de gaz de synthèse issus d'un processus de ...

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Experimental and numerical laminar syngas combustion across the flame, increasing with increasing density ratio, σ. Thus σ is probably the most sensitive parameter controlling the onset of hydrodynamic instability. Next to σ, the flame thickness, δ, is also expected to have a strong influence on the hydrodynamic instability, for two reasons. First, it measures the influence of curvature which, being positive for the outwardly propagating spherical flame, has a stabilizing effect on the cellular development. The thinner the flame, the weaker is the influence of curvature and consequently the stronger is the destabilizing propensity. The second influence is that it controls the intensity of the baroclinic torque developed over a slightly wrinkled flame surface, which depends on the density gradient across the flame and the pressure gradient along the flame (Sun et al., 1999). tel-00623090, version 1 - 13 Sep 2011 For the development of the diffusional-thermal instability, an appropriate parameter representing the effect of non-equidiffusion is the flame Lewis number, L e [Markstein, (1951); Matalon and Matkowsky, (1982); Law and Sung, (2000)]. It is well established and understood theoretically that unstretched flames are diffusionally unstable (stable) for L e that are smaller (greater) than a value slightly less than unity. However, the calculation of effective Lewis number for a multi-component fuel mixture is not as straightforward as for pure fuel-air mixtures and is a subject that is out of the scope of the present work. 4.1.1.2 Flame Radius Fig. 4.16 gives the variations of flame radius versus the time for syngas-air mixtures. The study shows that flame expands spherically after the ignition, and the flame radius will increase rapidly in the subsequent process. There are a quasi-linear correlation between flame radius and time for all syngas cases. The higher gradient of radius-time curves is obtained for stoichiometric syngas-air mixtures. The lean (φ=0.8) and rich (φ=1.2) syngas-air mixtures have similar gradients in the updraft case. This difference increases for the downdraft syngas case. Fluidized syngas has the lowest radius-time curve gradients. Information for rich mixture of fluidized syngas is missing due to ignition difficulties. According to the Markstein view the gradient of the radius-time curve reflects the stretching effectiveness of flame. For an unstable flame, the gradient of the radius-time curve will decrease with the flame expansion, while for a stable flame; the gradient of the radius-time curve will increase with the flame expansion. The quasi-linear 100
Chapter 4 behaviour of the curves radius-time shows that that the stretch rate has low effect in the syngas-air mixtures. 25 20 Radius (mm) 15 10 5 φ 0.6 0.8 1.0 1.2 tel-00623090, version 1 - 13 Sep 2011 Radius (mm) 25 20 15 10 5 0 0 25 0 5 10 15 20 Time (ms) (a) 0.6 0.8 1.0 1.2 0 5 10 15 20 Time (ms) (b) φ 20 Radius (mm) 15 10 5 0 0.8 1.0 0 5 10 15 20 Time (ms) (c) φ Figure 4.16 – Flame radius versus time for syngas-air mixtures at various equivalence ratios and 1.0 bar. (a) Updtraft. (b) Downdraft (c) Fluidized bed. 101
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THÈSE Pour l’obtention du Grade
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Acknowledgements Acknowledgements T
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Résumé __________________________
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Nomenclature Nomenclature Roman tel
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Nomenclature Subscripts tel-0062309
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Contents tel-00623090, version 1 -
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Contents 6.4. SYNGAS FUELLED-ENGINE
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Introduction CHAPTER 1 INTRODUCTION
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Introduction proves to have higher
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Introduction Chapter 3 - Experiment
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Bibliographic revision CHAPTER 2 BI
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Bibliographic revision point today
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Bibliographic revision - Boudouard
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Bibliographic revision Table 2.1 -
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Bibliographic revision Biomass Dryi
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Bibliographic revision Circulating
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Bibliographic revision or eliminate
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Bibliographic revision established
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Bibliographic revision Hydrogen Hyd
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Bibliographic revision of low moist
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Bibliographic revision scrubbing an
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Bibliographic revision suggests tha
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Bibliographic revision 1 d( δ A) 1
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Bibliographic revision Since n is
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Bibliographic revision 2 ( rsr ) 2
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Bibliographic revision This evoluti
Page 53 and 54: Bibliographic revision The burning
Page 55 and 56: Bibliographic revision δVG = − a
Page 57 and 58: Bibliographic revision 2 1 − −
Page 59 and 60: Bibliographic revision where the su
Page 61 and 62: Bibliographic revision the stretche
Page 63 and 64: Bibliographic revision burning velo
Page 65 and 66: Experimental set ups and diagnostic
Page 89 and 90: Chapter 4 CHAPTER 4 EXPERIMENTAL AN
Page 91 and 92: Chapter 4 4.1 Laminar burning veloc
Page 93 and 94: Chapter 4 4.1.1.1 Flame morphology
Page 95 and 96: Chapter 4 P i = 1.0 bar, Ti = 293 K
Page 97 and 98: Chapter 4 Figure 4.5 shows schliere
Page 99 and 100: Chapter 4 P i = 2.0 bar, T i = 293
Page 101 and 102: Chapter 4 Sn (m/s) 3.0 2.5 2.0 1.5
Page 103: Chapter 4 5 ms 10 ms 15 ms 20 ms 25
Page 107 and 108: Chapter 4 1.50 Sn (m/s) 1.25 1.00 0
Page 109 and 110: Chapter 4 0.5 0.4 φ =1.0 Su (m/s)
Page 111 and 112: Chapter 4 variation of the normaliz
Page 113 and 114: Chapter 4 4.1.1.6 Comparison with o
Page 115 and 116: Chapter 4 The values of laminar bur
Page 117 and 118: Chapter 4 Pressure (bar) 7 6 5 4 3
Page 119 and 120: Chapter 4 0.5 0.4 φ=1.2 Su (m/s) 0
Page 121 and 122: Chapter 4 0.3 φ=0.8 Su (m/s) 0.2 0
Page 123 and 124: Chapter 4 a minimum pressure to exp
Page 125 and 126: Chapter 4 Notice the similar behavi
Page 127 and 128: Chapter 4 A very good agreement bet
Page 129 and 130: Chapter 4 ( ) Q = h T − T (4.21)
Page 131 and 132: Chapter 4 tel-00623090, version 1 -
Page 133 and 134: Chapter 4 are tested and discussed.
Page 135 and 136: Chapter 4 7 500 Pressure (bar) 6 5
Page 137 and 138: Chapter 4 Pressure (bar) 7 6 5 4 3
Page 139 and 140: Chapter 4 4.2.3.4 Quenching distanc
Page 141 and 142: Chapter 4 10000 Quenching distance
Page 143 and 144: Chapter 5 CHAPTER 5 EXPERIMENTAL ST
Page 145 and 146: Chapter 5 30 10 25 8 Pressure (bar)
Page 147 and 148: Chapter 5 30 Piston position (mm) 2
Page 149 and 150: Chapter 5 5.1.1.4 In-cylinder press
Page 151 and 152: Chapter 5 estimation of various par
Page 153 and 154: Chapter 5 TDC 1.25 ms 2.5 ms 3.75 m
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Chapter 5 Piston position (mm) 500
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Chapter 5 tel-00623090, version 1 -
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Chapter 5 From figure 5.15 is possi
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Chapter 5 From figure 5.16 is obser
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Chapter 5 80 Pressure (bar) 70 60 5
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Chapter 5 80 10 Pmax (bar) 70 60 50
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Chapter 5 -5.0 ms -3.75 ms -2.5 ms
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Chapter 5 observation emphasis the
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Chapter 6 CHAPTER 6 NUMERICAL SIMUL
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Chapter 6 centered at the spark plu
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Chapter 6 H 2 O, (3) N 2 , (4) O 2
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Chapter 6 For all the above express
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Chapter 6 motions within the cylind
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Chapter 6 tel-00623090, version 1 -
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Chapter 6 Heat transfer Wei et al.,
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Chapter 6 The calibration coefficie
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Chapter 6 6.3.2.2 In-cylinder volum
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Chapter 6 40 Experimental 30 Numeri
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Chapter 6 80 70 60 Numerical Experi
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Chapter 6 downdraft syngas than for
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Chapter 6 80 23º BTDC 60 29.5º BT
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Chapter 6 with experimental results
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Conclusions CHAPTER 7 CONCLUSIONS 7
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Conclusions radius and time for syn
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Conclusions conditions, therefore s
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Conclusions tel-00623090, version 1
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References References tel-00623090,
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References tel-00623090, version 1
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Appendix A - Overdetermined linear
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Appendix A - Overdetermined linear
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Appendix B- Syngas-air mixtures pro
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Appendix C -Rivère model Heat flux
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Appendix C -Rivère model The work
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tel-00623090, version 1 - 13 Sep 20
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