Etude de la combustion de gaz de synthèse issus d'un processus de ...
Etude de la combustion de gaz de synthèse issus d'un processus de ... Etude de la combustion de gaz de synthèse issus d'un processus de ...
Experimental and numerical laminar syngas combustion tel-00623090, version 1 - 13 Sep 2011 Figure 4.38 – Combust flowchart. 4.2.3 Results discussion and code validation The numerical results are validated for syngas-air mixtures by comparison with experimental results of pressure evolution. Different equivalence ratios and pressures 128
Chapter 4 are tested and discussed. The numerical code described above is then used to estimate the heat flux and quenching distance of syngas-air mixtures. 4.2.3.1 Influence of the heat transfer model In order to define the heat transfer model to use, one first compare two formulations already mentioned above: the classical Woschni (1967) correlation and the recent Rivère (2005) formulation. The comparison of both formulations is made in the figure 4.39. tel-00623090, version 1 - 13 Sep 2011 Pressure (bar) 7 6 5 4 3 2 1 0 Experimental P Woschni P Rivère P Woschni Qw Rivère Qw 0 10 20 30 40 50 60 70 80 90 100 Time (ms) Figure 4.39 – Influence of the heat transfer model – stoichiometric downdraft syngas-air, P=1.0 bar. From figure 4.39 is possible to conclude that the heat transfer model has only marginal influence on pressure curve. However, the Rivère model shows to better follow the 500 400 300 200 100 0 Qw (kW/m 2 ) pressure curve on the cooling side. The reason is the higher value of the heat flux through the wall using this model. This result is in agreement with Boust, (2006), who compared these models with experimental heat flux values for methane-air mixtures and concluded that Rivère model is most suitable to simulate the wall-flame heat transfer and that Woschni model is inadequate in the absence of a strong flow. Thus, Rivère model is applied throughout the following results. 4.2.3.2 Influence of equivalence ratio The influence of the equivalence ratio in the burning velocity and pressure was experimentally determined for the syngas compositions under study. It was seen that the pressure and burning velocity decreases when departing from stoichiometric 129
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Experimental and numerical <strong>la</strong>minar syngas <strong>combustion</strong><br />
tel-00623090, version 1 - 13 Sep 2011<br />
Figure 4.38 – Combust flowchart.<br />
4.2.3 Results discussion and co<strong>de</strong> validation<br />
The numerical results are validated for syngas-air mixtures by comparison with<br />
experimental results of pressure evolution. Different equivalence ratios and pressures<br />
128
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