Turbulent nonpremixed CH4/H2 flame has been simulated using several typical differential secondmoment turbulence closure (SMTC) models. To clarify the applicability of the various models, the LRR-IP model,JM model, SS...Turbulent nonpremixed CH4/H2 flame has been simulated using several typical differential secondmoment turbulence closure (SMTC) models. To clarify the applicability of the various models, the LRR-IP model,JM model, SSG model as well as two modified LRR-IP models were tested. Some of above-mentioned SMTC models cannot provide the overall satisfactory predictions of this challenging case. It is confirmed again that the standard LRR-IP model considerably overpredict the centerline velocity decay rate, and therefore performs not well. Also it is interesting to observe that the JM model does not perform well in this challenging test case, although it has already been proved successful in other cases. The SSG model produces quite satisfactory prediction and performs equally well or better than the two modified LRR-IP models in the reacting case. It can be concluded that the modified LRR-IP models as well as the SSG model are superior to the other SMTC models in the turbulent nonpremixed CH4/H2 flame.展开更多
The Arrhenius law implies that reaction rate is a continuous function of temperature.However,the steady laminar flamelet model(SLFM)does not explicitly give this functional relationship.The present study addresses thi...The Arrhenius law implies that reaction rate is a continuous function of temperature.However,the steady laminar flamelet model(SLFM)does not explicitly give this functional relationship.The present study addresses this relation in the SLFM.It is found that reaction rate is not continuous in the mixture-fraction space.As a result,the SLFM is unable to predict local extinction and reignition.Furthermore,we use the unstable branch of the'S-curve'to fill the gap between steady burning branch and extinction one,and find that this modification leads to a continuous dependent of reaction rate on temperature.Thus the modified SLFM can describe the local extinction and reignition.展开更多
文摘Turbulent nonpremixed CH4/H2 flame has been simulated using several typical differential secondmoment turbulence closure (SMTC) models. To clarify the applicability of the various models, the LRR-IP model,JM model, SSG model as well as two modified LRR-IP models were tested. Some of above-mentioned SMTC models cannot provide the overall satisfactory predictions of this challenging case. It is confirmed again that the standard LRR-IP model considerably overpredict the centerline velocity decay rate, and therefore performs not well. Also it is interesting to observe that the JM model does not perform well in this challenging test case, although it has already been proved successful in other cases. The SSG model produces quite satisfactory prediction and performs equally well or better than the two modified LRR-IP models in the reacting case. It can be concluded that the modified LRR-IP models as well as the SSG model are superior to the other SMTC models in the turbulent nonpremixed CH4/H2 flame.
基金supported by CAS(KJCX2-SW-L08),973 Program of China(2007CB814800,2009CB724100)NSFC(11072247,10702074,10732090,50906096)the LNM initial funding for young investigators
文摘The Arrhenius law implies that reaction rate is a continuous function of temperature.However,the steady laminar flamelet model(SLFM)does not explicitly give this functional relationship.The present study addresses this relation in the SLFM.It is found that reaction rate is not continuous in the mixture-fraction space.As a result,the SLFM is unable to predict local extinction and reignition.Furthermore,we use the unstable branch of the'S-curve'to fill the gap between steady burning branch and extinction one,and find that this modification leads to a continuous dependent of reaction rate on temperature.Thus the modified SLFM can describe the local extinction and reignition.
