Abstract

Using the high-resolution experimental spectral absorption coefficients of six fuel gases and the line by line absorption spectra of CO and CH4 based on HITRAN and HITEMP spectral databases, in this paper, novel coefficients for weighted-sum-of-gray-gases (WSGG) model are presented for Heptane, Methane, Methanol, MMA, Propane, Propylene, Toluene, and CO. Moreover, for soot, the spectral absorption coefficients were calculated assuming Rayleigh regime implementing the complex index of refraction obtained from the correlations of Chang and Charalampopoulos. The presented WSGG models were coupled with those of literature for CO2 and H2O by means of the superposition method. The models were first validated in several one-dimensional benchmarks representing various levels of inhomogeneous conditions in temperature, gas concentration and soot loading. Then, the WSGG models were employed in solving a three-dimensional case representing a Heptane pool fire. Using the time averaged 3-D CFD profiles, the WSGG models solved the spectral radiative heat transfer exhibiting excellent agreement with the results of line by line calculations in terms of radiative heat flux and radiative heat source. Moreover, the emissivity charts were provided comparing the emissivity calculated by LBL calculations with those of the new WSGG models.

Highlights

  • Spectral radiative heat transfer in gaseous combustion is among the most challenging engineering problem to solve

  • Besides the model verification through the emissivity charts, to further validate the new WSGG models, the radiation heat transfer is solved in several 1-D benchmarks representing various levels of complexity and heterogeneity in thermal conditions of participating media which consist of fuel gases, combustion gases and soot

  • As described in [9], the WSGG model can be used with any method to integrate the radiative transfer equation (RTE) over the spatial domain

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Summary

Introduction

Spectral radiative heat transfer in gaseous combustion is among the most challenging engineering problem to solve. Pierrot et al [23] compared the accuracy of several narrow-band and global models in predicting wall radiative heat flux of three slab problems representing emission-dominated and absorption-dominated problems They re­ ported up to 50% error in their WSGG model predictions while SLW and ADF models had deviations around 10%–20% with the same computa­ tional costs. Its drawbacks can be listed as 1) mixing of different species which should be done by superposition which drastically increases the computational cost due to the high number of the required RTE solutions, 2) its dependency on total emissivity in the development stage which limits the model to certain ranges of pL and temperature and reduces the accuracy of the model in absorption-dominated problems [23], 3) its lower accuracy compared to other global models [26,31], and 4) no chance of scalability as explained before. Quite the same total emissivity can be expected for these gases followed by similar WSGG model’s coefficients

Spectral absorption databases
WSGG coefficients for individual species
Superposition method in solving RTE for a gas mixture
Results and discussion
One-dimensional verification
Three-dimensional validation
CPU time analysis
Conclusion and remarks
Declaration of competing interest
Full Text
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