Results for case Propane/air diffusion flame

Code: Code_Saturne

Version: 2.0-beta2

Authors: M. Hassanaly

Method and Numerical Options

All calculations have been done with the scalable wall functions.

Models

%$k-\varepsilon$%, %$k-\omega$%, gas combustion model (COGZ_D3P: Diffusion Flames), Radiation: discrete ordinate method

Mesh

In this study, two meshes have been used, whereas both are axissymetric. The first mesh consists of hexahedronic cells; The second one consists of triangular prisms.

Description of the results files

The simulations have been carried out using both the two-equation %$k-\varepsilon$% and %$k-\omega$% turbulence model. These turbulence models have been tested assuming complete combustion, i.e. all of the fuel carbon is converted into carbon dioxide. The corresponding reaction equation is given by: %BEGINLATEX{label="bal_mom1"}% $ C_{3}H_{8}+5(O_{2}+3.76N_{2}) \Rightarrow 3CO_{2}+4H_{2}O+18.8N_{2} $ %ENDLATEX% Moreover, alternative reaction equations have been tested and tried. Assuming that some of the fuel carbon is converted into carbon dioxide and carbon monoxide as well, the reaction equation can be re-written to: %BEGINLATEX{label="bal_mom2"}% $ C_{3}H_{8}+4.25(O_{2}+3.76N_{2}) \Rightarrow 3(0.5CO_{2}+0.5CO)+4H_{2}O+15.98N_{2} $ %ENDLATEX%

Supposing that all of the fuel carbon is converted into carbon monoxide, which lacks any physical background, yields to the following expression:

%BEGINLATEX{label="bal_mom3"}% $ C_{3}H_{8}+3.5(O_{2}+3.76N_{2}) \Rightarrow 3CO+4H_{2}O+13.16N_{2} $ %ENDLATEX%

In the following figures some results of computed and measured fluid properties (gas temperature) are shown. In order to limit the information given here, only the results obtained using the hexahedronic mesh are presented. In figure 2 and 3, respectively, axial and radial profiles of the gas temperature are plotted. The single radial profiles correspond to different y-distances. It can be seen that the temperatures obtained using the %$k-\omega$% model (CS 2.0 beta2 - k-omg) do not match the measured data very well, whereas using the %$k-\varepsilon$% model (CS 2.0 beta2 - k-eps) yields to reasonable results which are comparable to the experimental observations.

Figure 2: Temperature profiles obtained using both the %$k-\varepsilon$% model and the %$k-\omega$% model as well. Combustion occurs according to equation (1). Mesh consists of hexahedronic cells.

Figure 3: Temperature profiles obtained using both the %$k-\varepsilon$% model and the %$k-\omega$% model as well. Combustion occurs according to equation (1). Mesh consists of hexahedronic cells.

In Figure 4 and 5 temperature profiles are shown using again the %$k-\varepsilon$% model and the %$k-\omega$% model. However, this time combustion occurs according to reaction equation (2). Due to the formation of CO the predicted peak temperatures are reduced, being somewhat lower than the corresponding experimental value. Again, significant differences in the predicted and measured temperature profile can be observed using the k-ω turbulence model.

Figure 4: Temperature profiles obtained using both the %$k-\varepsilon$% model and the %$k-\omega$% model as well. Combustion occurs according to reaction equation (2). Mesh consists of hexahedronic cells.

Figure 5: Temperature profiles obtained using both the %$k-\varepsilon$%; model and the %$k-\omega$% model as well. Combustion occurs according to equation (2). Mesh consists of hexahedronic cells.

The results obtained assuming that combustion occurs according to equation (3) are shown in figure 6 and 7. Despite the fact that the exclusive formation of carbon monoxide during diffusive combustion lacks any physical background, these results are shown to prove that the peak temperature decreases with increased carbon monoxide formation. This can be clearly observed.

Figure 6: Temperature profiles obtained using both the %$k-\varepsilon$% model and the %$k-\omega$% model as well. Combustion occurs according to equation (3). Mesh consists of hexahedronic cells.

Figure 7: Temperature profiles obtained using both the %$k-\varepsilon$% model and the %$k-\omega$% model as well. Combustion occurs according to equation (3). Mesh consists of hexahedronic cells.

Boundary conditions

Reference Publications

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