Radiative heat transfer is analyzed in rocket combustion chambers and in the flow around a re-entry vehicle. To do so, the governing equations of the P1 radiation transport model are derived, afterwards discretized using the Finite Volume Method and finally implemented in the CFD solver NSMB. For spectral integration, different models are combined with the P1 radiation model. For radiative heat transfer in rocket combustion chambers Weighted Sum of Gray Gases Models (WSGGM) are identified for spectral modeling and their governing equations with the P1 model are derived to implement them in NSMB. For radiative heat transfer in re-entry flows, a spectral model is developed based on a Full Spectrum k-Distribution (FSK) using the spectral database PARADE. The model is applicable to nonhomogeneous media with varying temperature and mole fractions. The governing equations of the P1 model in conjunction with this model are derived and the model is also implemented in NSMB.
All models for radiative heat transfer are validated in several one-dimensional cases and show good agreement with analytical solutions. The sole P1 model yields an error below 5 %. The combination of the P1 model and the WSGGM gives satisfactory results. The FSK reproduces nearly exact results with errors below 1 % for homogeneous media. For nonhomogeneous media, the Multi Group Full Spectrum Correlated k-Distribution (MGFSCK) reduces devia-tions of the FSK from over 250 % to below 10 %. Radiative transfer in rocket combustion chambers is analyzed using the P1 model and several WSGGM for H2/O2 and CH4/O2 combustion. The results reveal that simple WSGG models yield nearly the same radiative wall heat flux (RWHF) with less computational efforts than more complex WSGGM. Using WSGGM appropriate for nonhomogeneous media decreases the RWHF. An enlarged chamber volume increases the RWHF. The influence of radiation on the flow is investigated in a loosely coupled simulation, revealing a negligible effect. For CH4/O2 combustion the maximum relative RWHF decreases compared to H2/O2 combustion. The maximum local ratio of the RWHF and total wall heat flux (TWHF) is between 8-10 % near the injector face plate while the integrated ratio is below 3 % for both propellant combi-nations. The analysis reveals a small influence of radiation on the heat loads in the combus-tion chambers investigated. The second system analyzed is the re-entry of the FIRE II capsule. Several models in NSMB for the simulation of the flow are improved and tested. With a final set of models, the convec-tive wall heat flux (CWHF) as well as the temperature and species number densities lie within 10 % deviation compared to former numerical investigations of the FIREII flight test. A one-dimensional Line-by-Line (LBL) radiative heat transfer analysis along the stagnation line is done afterwards with PARADE. The deviation of this analysis is below 2% in terms of RWHF at the stagnation point with regard to the flight experiment. The P1 model with the MGFSCK yields good accuracy compared to the LBL results with a reduction in computational effort by a factor of nearly 1000. Concerning RWHF at the stagna-tion point, the error is around 20 %. Concerning divergence of radiative heat flux the error is lower than 30 % over most of the stagnation line. The divergence of radiative heat flux predicted by the P1 model with the MGFSCK for the entire domain is coupled in the total energy equation of NSMB to examine the influence of radiation on the flow. It reveals that the CWHF decreases by a maximum of 10 % and the flow properties do not change by more than 5 %. This concludes a minor influence of radia-tion on the flow for the chosen trajectory point of the FIREII flight test.
«Radiative heat transfer is analyzed in rocket combustion chambers and in the flow around a re-entry vehicle. To do so, the governing equations of the P1 radiation transport model are derived, afterwards discretized using the Finite Volume Method and finally implemented in the CFD solver NSMB. For spectral integration, different models are combined with the P1 radiation model. For radiative heat transfer in rocket combustion chambers Weighted Sum of Gray Gases Models (WSGGM) are identified for sp...
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