A comprehensive evaluation of the non gray gas thermal radiation using the line-by-line model in one- and two-dimensional enclosures

Effects of total pressure on non-grey gas radiation transfer in oxy-fuel combustion using the LBL, SNB, SNBCK, WSGG, and FSCK methods

A comprehensive evaluation of different radiation models in a gas turbine combustor under conditions of oxy-fuel combustion with dry recycle

In oxy-fuel combustion with CO2 recycle, the non-gray gas radiative heat transfer characteristics of gaseous participating media are different from those in air-fuel combustion. Therefore, the choice of a non-gray gas radiation model should be carefully made since it plays an important role in modeling the oxy-fuel combustion system. Using the statistical narrow-band model as a benchmark, in this paper we provide a comprehensive assessment of the development of the weighted-sum-of-gray-gase (WSGG) model, which has been achieved in recent years. The results show that the predicted values obtained by the WSGG model are generally reasonably accurate, though some significant differences still exist. For the total emissivity, the WSGG models by Dorigon et al. (2013 Int. J. Heat Mass Transfer 64 863) and Bordbar et al. (2014 Combust. Flame 161 2435) are consistent well with the benchmark model, within a relative error of less than about 20%. Under the conditions of PH2O/PCO2=1 and 2, the magnitudes of radiative heat transfer between two planar plates are calculated using the discrete-ordinate method and WSGG model. It is found that the radiative source and radiative net heat flux obtained using the WSGG model parameters of Dorigon et al. and Bordbar et al. are more accurate than using other parameters developed in the literature (about 10% relative errors). It is worth noting that the WSGG model parameters of Jonhansson et al. (2011 Combust. Flame 158 893) and Bordbar et al. have a wider range of applications.

Generally, the involvement of hydrocarbons such as C2H4 and its derivative C2H2 in thermal radiation has not been accounted in the numerical simulation of their flames, which may cause serious error for estimation of temperature in the early stage of combustion. At the first, the Statistical Narrow-Band (SNB) model parameters for C2H2 and C2H4 are generated from line by line (LBL) calculations. The distributions of the concentrations of radiating gases such as H2O, CO2, CO, C2H2 and C2H4, and the temperature along the centerline of a laminar ethylene/air diffusion flame were chosen to form a one-dimensional, planar enclosure to be tested in this study. Thermal radiation transfer in such an enclosure was calculated using the LBL approach and the SNB model, most of the relative errors are less than 8% and the results of these two models shows an excellent agreement. Below the height of 20 mm, which is the early stage of the flame, the average fraction contributed by C2H2 and C2H4 in the radiative heat source is 33.8%, while that by CO is only 5.8%. This result indicates that the involvement of C2H2 and C2H4 in radiation heat transfer needs to be taken into account in the numerical modeling of the ethylene/air diffusion flame, especially in the early stage of combustion.

Using a weighted sum of gray gases model with gray gas regrouping technique (WSGGM-RG), problems of radiative transfer within three-dimensional enclosures filled with non-homogeneous and non-isothermal combustion gas mixtures were solved. The radiative transfer equation was solved based on discrete ordinate method (DOM) and raytracing method (RTM) with WSGGM-RG. The results using WSGGM-RG were compared with those using the statistical narrow band (SNB) model. The average radiative intensities and radiative heat fluxes using WSGGM-RG corresponded relatively well to those using the SNB model as reference data. A very good computational efficiency was also noted.

Calculations of thermal radiation transfer of C2H2 and C2H4 together with H2O, CO2, and CO in a one-dimensional enclosure using LBL and SNB models

The effect of different HITRAN databases on the accuracy of the SNB and SNBCK calculations

Numerical calculation of infrared emission from hot plume is of great significance for flight monitoring and detections. In this paper, the SNB (statistical narrow band) model established with parameters derived from the high-resolution spectral database HITEMP 2010 is used to perform the hot plume infrared signature simulations. Accuracy of the model is examined by the exact LBL (line by line) method, which proves the model’s reliability to predict radiative properties of combustion gases. In the application part, the SNB model is used to analyze infrared signatures of aircraft plumes cruising at different flight altitudes. The results show that cruising at a higher-altitude will obviously reduce the plume infrared emission. Besides, the plume infrared emissive energy mainly concentrates in a special wavenumber interval and can be strongly absorbed by atmosphere.

In combustion applications, the weighted-sum-of-grey-gases (WSGG) model is widely used because it is computationally efficient, but it often yields relatively large errors. The objective of this study is to examine the effect of radiation models on CFD predictions of flame spread. To this end, a statistical narrow band (SNB) model and the WSGG model are employed for the simulation of two upward flame spread scenarios, one being a largescale flame spread over a vertical PMMA wall while the other representing flame spread along vertical corner walls. The entire flame spread model also consists of a four equation turbulence model, an eddy-break-up (EBU) combustion model, a discrete transfer (DT) radiation model, a simple soot model and a non-charring pyrolysis model. Quantitative comparison is made between the prediction results obtained with the SNB model and the WSGG model as well as the experimental data. Results clearly show that the SNB model yields more accurate results than the WSGG approach. However, the SNB model is about four to five times more time consuming than the WSGG model. Therefore, for simulations of complex engineering applications a compromise between accuracy and numerical efficiency should be taken into account.

Numerical calculation of infrared emission from hot plume is of great significance for flight monitoring and detections. In this paper, the SNB (statistical narrow band) model established with parameters derived from the high-resolution spectral database HITEMP 2010 is used to perform the hot plume infrared signature simulations. Accuracy of the model is examined by the exact LBL (line by line) method, which proves the model’s reliability to predict radiative properties of combustion gases. In the application part, the SNB model is used to analyze infrared signatures of aircraft plumes cruising at different flight altitudes. The results show that cruising at a higher-altitude will obviously reduce the plume infrared emission. Besides, the plume infrared emissive energy mainly concentrates in a special wavenumber interval and can be strongly absorbed by atmosphere.

Narrow-band transmissivities in the spectral range of 150 to 9300 cm−1 and at a uniform resolution of 25 cm−1 were calculated using the statistical narrow-band (SNB) model with the band parameters of Soufiani and Taine, the more recent parameters of Andre and Vaillon, and the line-by-line (LBL) method along with the HITEMP-2010 spectroscopic database. Calculations of narrow-band transmissivity were conducted for gas columns of different lengths and containing different isothermal and non-isothermal CO2-H2O-N2 mixtures at 1 atm. Narrow-band transmissivities calculated by the SNB model are in large relative error at many bands. The more recent SNB model parameters of Andre and Vaillon are more accurate than the earlier parameters of Soufiani and Taine. The Planck mean absorption coefficients of CO2, H2O, CO, and CH4 in the temperature range of 300 to 2500 K were calculated using the LBL method and different versions of the high resolution transmission (HITRAN) and high-temperature spectroscopic absorption parameters (HITEMP) spectroscopic databases. The SNB model was also used to calculate the Planck mean absorption coefficients of these four radiating gases. The LBL results of the Planck mean absorption coefficient were compared with the classical results of Tien and those from the SNB model.

Non-gray gas radiation analysis and comparison are conducted by combining a ray tracing method and two statistical narrow band (SNB) spectral models, namely the Goody SNB model and the Malkmus SNB model. In this paper, gas radiation in real gas containing H2O, H2O/N2, or H2O/CO2/N2 mixtures at 1 atm in planar plates was studied. Comparisons between these models are performed using the latest narrow-band database. The present computations are validated by reproducing the published results in the literature. The radiative source term, the wall fluxes, the narrow-band radiation intensities along a line-of-sight and the computing time are all compared. From the comparisons, it is found that the Malkmus SNB model is somewhat superior to the Goody SNB model and the former is preferred in engineering application.

Calculations of gas thermal radiation transfer in one-dimensional planar enclosure using LBL and SNB models

Calculations of radiative intensity in one-dimensional gaseous media with black boundaries using the statistical narrow band model

Combined effects of nongray radiation and pressure on premixed CH 4/O 2/CO 2 flames