Turbulent swirling flows and methane-air swirling diffusion combustion are simulated by both large-eddy simulation (LES) using a Smagorinsky-Lilly subgrid-scale (SGS) turbulence model, a second-order moment (SOM) subg...Turbulent swirling flows and methane-air swirling diffusion combustion are simulated by both large-eddy simulation (LES) using a Smagorinsky-Lilly subgrid-scale (SGS) turbulence model, a second-order moment (SOM) subgrid-scale combustion model and an eddy break up (EBU) combustion model and Reynolds-averaged NavierStokes (RANS) modeling using the Reynolds stress equation model and a second-order moment (SOM) combustion model. For swirling flows, the LES statistical results give better agreement with the experimental results than the RANS modeling, indicating that the adopted subgrid-scale turbulence model is suitable for swirling flows. For swirling combustion, both the proposed SOM SGS combustion model and the RANS-SOM model give the results in good agreement with the experimental results, but the LES-EBU modeling results are not in agreement with the experimental results.展开更多
The second-order moment combustion model, proposed by the authors is validated using the direct numerical simulation （DNS） of incompressible turbulent reacting channel flows. The instantaneous DNS results show the n...The second-order moment combustion model, proposed by the authors is validated using the direct numerical simulation （DNS） of incompressible turbulent reacting channel flows. The instantaneous DNS results show the near-wall strip structures of concentration and temperature fluctuations. The DNS statistical results give the budget of the terms in the correlation equations, showing that the production and dissipation terms are most important. The DNS statistical data are used to validate the closure model in RANS second-order moment （SOM） combustion model. It is found that the simulated diffusion and production terms are in agreement with the DNS data in most flow regions, except in the near-wall region, where the near-wall modification should be made, and the closure model for the dissipation term needs further improvement. The algebraic second-order moment （ASOM） combustion model is well validated by DNS.展开更多
A single-element shear-coaxial combustor using gaseous hydrogen(GH2) and oxygen(GO2) was designed and hot-tested.The wall temperature was measured.The combustion flowfield of this GH2 /GO2 single-element combustor was...A single-element shear-coaxial combustor using gaseous hydrogen(GH2) and oxygen(GO2) was designed and hot-tested.The wall temperature was measured.The combustion flowfield of this GH2 /GO2 single-element combustor was modeled by RANS(Reynolds Averaged Navier-Stokes) and LES(Large Eddy Simulation) methods respectively.The impact of using various turbulence and turbulent combustion models was investigated to obtain the model combination which best represented the experimental data in the RANS modeling.The flamelet model was used in the LES modeling and the validity of its application to the GH2 /GO2 combustion in the combustor was carefully examined.The combustor wall heat flux distributions of both RANS and LES results show good agreement with the experimental data.The experimental wall temperature distribution can be clearly explained through analyzing the inner flowfield structure.The results indicate that both RANS and LES used in this paper can give good predictions of the development of the whole flowfield and the combustion completion length.LES can resolve large-scale flow motions in the combustor and accurately predict the influence of the wall heat loss on the combustion efficiency.展开更多
基金Supported by the Special Funds for Major State Basic Research (No. G-1999-0222-07).
文摘Turbulent swirling flows and methane-air swirling diffusion combustion are simulated by both large-eddy simulation (LES) using a Smagorinsky-Lilly subgrid-scale (SGS) turbulence model, a second-order moment (SOM) subgrid-scale combustion model and an eddy break up (EBU) combustion model and Reynolds-averaged NavierStokes (RANS) modeling using the Reynolds stress equation model and a second-order moment (SOM) combustion model. For swirling flows, the LES statistical results give better agreement with the experimental results than the RANS modeling, indicating that the adopted subgrid-scale turbulence model is suitable for swirling flows. For swirling combustion, both the proposed SOM SGS combustion model and the RANS-SOM model give the results in good agreement with the experimental results, but the LES-EBU modeling results are not in agreement with the experimental results.
基金Supported by the National Natural Science Foundation of China （50606026, 50736006）.
文摘The second-order moment combustion model, proposed by the authors is validated using the direct numerical simulation （DNS） of incompressible turbulent reacting channel flows. The instantaneous DNS results show the near-wall strip structures of concentration and temperature fluctuations. The DNS statistical results give the budget of the terms in the correlation equations, showing that the production and dissipation terms are most important. The DNS statistical data are used to validate the closure model in RANS second-order moment （SOM） combustion model. It is found that the simulated diffusion and production terms are in agreement with the DNS data in most flow regions, except in the near-wall region, where the near-wall modification should be made, and the closure model for the dissipation term needs further improvement. The algebraic second-order moment （ASOM） combustion model is well validated by DNS.
文摘A single-element shear-coaxial combustor using gaseous hydrogen(GH2) and oxygen(GO2) was designed and hot-tested.The wall temperature was measured.The combustion flowfield of this GH2 /GO2 single-element combustor was modeled by RANS(Reynolds Averaged Navier-Stokes) and LES(Large Eddy Simulation) methods respectively.The impact of using various turbulence and turbulent combustion models was investigated to obtain the model combination which best represented the experimental data in the RANS modeling.The flamelet model was used in the LES modeling and the validity of its application to the GH2 /GO2 combustion in the combustor was carefully examined.The combustor wall heat flux distributions of both RANS and LES results show good agreement with the experimental data.The experimental wall temperature distribution can be clearly explained through analyzing the inner flowfield structure.The results indicate that both RANS and LES used in this paper can give good predictions of the development of the whole flowfield and the combustion completion length.LES can resolve large-scale flow motions in the combustor and accurately predict the influence of the wall heat loss on the combustion efficiency.
