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 ...
Numerical simulation of a syngas-fuelled engine In order to compare pressure evolution of the different fuels at the same ignition timing, figure 6.13 shows this cylinder pressure comparison. 50 Pressure (bar) 40 30 20 Updraft Dow ndraft Methane 10 tel-00623090, version 1 - 13 Sep 2011 0 240 270 300 330 360 390 420 450 480 Crank Angle (degrees) Figure 6.13- Cylinder pressure versus crank angle for various fuels. ε= 8.5, IT= 20º BTDC, 900 rpm. Figure 6.13 shows that higher peak pressure is obtained for methane-air (39 bar) mixture in comparison to both syngas compositions. Syngas compositions have similar behavior. Peak pressures are 35 bar for downdraft syngas and 34 bar for updraft syngas. These results are qualitatively in agreement with the RCM experimental results. However, quantitatively the difference in the maximum pressure is not as high as in RCM. This could be endorsed to the different characteristics of the experimental set ups, emphasized in sections 6.3.1 and 6.3.2. 6.5 Conclusion A simulation code for the power cycle of syngas-fuelled engines has been described, using a quasi-dimensional model with ‘standard’ modeling assumptions. A combustion model consisting of two differential equations was used, one for the mass conservation and one for energy conservation. Model testing has been carried on over detailed experimental data available in literature for hydrogen and methane, two of the main constituents of syngas. The very good agreement found allows validating the developed model and applied it to typical syngas compositions. An attempt to adapt the model to the RCM is made by changing several aspects of the model namely the in-cylinder volume function and burning rate model. The comparison 192
Chapter 6 with experimental results obtained in this work in the RCM shows that the adapted code is able to reproduce fairly well the in-cylinder pressure. The validated model is then applied to a syngas-fuelled engine in order determine its performance. Conclusions can be drawn that typical syngas compositions besides its lower heat value and burning velocities can be used on SI engines even at elevated rotation speeds. Another conclusion is that varying the ignition timing is possible to keep closely the same peak pressure for different rotation speeds. tel-00623090, version 1 - 13 Sep 2011 193
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Chapter 6<br />
with experimental results obtained in this work in the RCM shows that the adapted<br />
co<strong>de</strong> is able to reproduce fairly well the in-cylin<strong>de</strong>r pressure.<br />
The validated mo<strong>de</strong>l is then applied to a syngas-fuelled engine in or<strong>de</strong>r <strong>de</strong>termine its<br />
performance. Conclusions can be drawn that typical syngas compositions besi<strong>de</strong>s its<br />
lower heat value and burning velocities can be used on SI engines even at elevated<br />
rotation speeds. Another conclusion is that varying the ignition timing is possible to<br />
keep closely the same peak pressure for different rotation speeds.<br />
tel-00623090, version 1 - 13 Sep 2011<br />
193
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