| The study of the auto-ignition and stabilization mechanism of fuels is one of the most important researches on improving combustion. The auto-ignition and stabilization of several fuels have been researched based on controllable active thermo-atmosphere combustor (CATAC) in this paper. Focusing on criterion temperature, the auto-ignition and flame stabilization mechanisms of various fuels are analyzed throughout the paper.The CATAC was simulated and validated, which temperature field and velocity field were analyzed to maintain combustion stability.The auto-ignition and stabilization mechanisms of gaseous fuels and liquid fuel have been silulated and analyzed, separately. The criterion temperature of fuels stable auto-igntion and flame has been proved exisitent in the theoretical way. The influence of various parameters, such as jet velocity or average injection pressure, nozzle diameter, co-flow velocity, atmosphere pressure, on auto-ignition and stability were analyzed coupled with exhaust. Furthermore, the auto-ignition and stability mechanism of fuel injected into a running diesel engine was analyzed.Based on the above completion, conditional moment closure (CMC) model was coupled into STAR-CD and adopted to calculate the auto-ignition and stabilization mechanism of fuel at atmospheric pressure,high pressure atmosphere, and in-cylinder of a diesel engine conditions. The diesel was presented by C7H16. Hewson 32-step reaction mechanism was adopted. The combustion results of this model are validated with the experimental results, except that the exhaust results do not come from professional model,and worse than those got by STAR-CD. Through this model, the auto-ignition and flame stabilization mechanism focused on critiron temperature are proved in the view of micro-way by spieces mass fraction, temperature and mixture fraction. Finally, the CMC coupled STAR-CD models were tried to apply to simulate quasi HCCI engine. The auto-ignition and lifed flame stabilization of the fuel in quasi HCCI engine was analyzed, which approved the existence of a similar criterion temperature in quasi HCCI engine too.Through above analysis, this paper proved the auto-ignition and stabilization based on the criterion temperature have a good applicability. Gaseous fuel or liquid fuel, atmospheric or high pressure atmosphere, stable region or in-cylinder moving region, the criterion temperature can be found in any of above conditions. Fuel can not auto-ignition stably or their lifted flame can not be stable in the temperature region which below their criterion temperature. Contrarily, fuels can auto-ignite stably and their lifted flame can be stable in the temperature region which is higher than their criterion temperature. Analyzing combined with the exhaust emissions to ensure the atmosphere temperature approaching downward to the criterion temperature can both improve the combustion characteristics and reduce exhaust, which is significant. |
