Direct numerical simulation of a pulverized coal jet flame employing a global volatile matter reaction scheme based on detailed reaction mechanism

Abstract

A two-step global reaction scheme for the volatile matter of coal is proposed, and the unsteady coal particle and combustion behaviors in a turbulent pulverized coal jet flame are investigated by performing a direct numerical simulation (DNS) employing the proposed global reaction scheme. The two-step global reaction scheme is constructed to take into account the properties of the volatile matter such as transport coefficients, laminar flame speed and unburned gas temperature and to be applicable to various coal types, and it is validated by comparing the results with those obtained by the detailed reaction mechanism which includes 158 chemical species and 1804 reactions. The validity of the DNS is also assessed by comparing the results with those in the previous experiment (Hwang et al., Energy & Fuels, 2005), and the unsteady coal particle motions and combustion characteristics are examined in detail. The results show that the proposed two-step global reaction scheme for the volatile matter of coal can precisely predict the laminar flame speed and burned gas temperature for various coal types from bituminous to low-rank coals over wide ranges of conditions of equivalence ratios, pressures and unburned gas temperatures. In addition, it can correctly take into account the effects of dilutions by H 2 O and CO 2 which compromise the evaporated moisture from coal and products of char reaction. It is also verified that a lab-scale turbulent pulverized coal jet flame is well predicted by the DNS em

Primary soot particle distributions in a combustion field of 4 kW pulverized coal jet burner measured by time resolved laser induced incandescence (TiRe-LII)

“…The burner is known as one of the target flames for coal combustion researchers in the world. Various numerical simulation techniques have been applied for this burner (Hashimoto et al, 2012b, Zhao et al, 2014, Vascellari et al, 2014, Stein et al, 2013, Cai et al, 2015, Hara et al, 2015. From the previous studies, the distributions of OH radical (by OH-PLIF) and the velocity and size of coal particles (by SDPA) (Hwang et al, 2005) and the distribution of soot volume fraction (by LII) (Hayashi et al, 2013) of the burner have been reported.…”

Numerical study of HCl and SO2 impact on sodium emissions in pulverized-coal flames

“…The flame index, F.I., [35,50] Fig. 7 represents the stoichiometric conditions for 363 reactions between the volatile and the oxidizer.…”

“…[24][25][26]) towards high-fidelity approaches, i.e., large-eddy simulation (LES, 85 e.g. [27][28][29][30][31][32][33][34]) and direct numerical simulation (DNS, e.g., [35][36][37]). The high-fidelity approaches of 86 LES and DNS have demonstrated advantages over RANS in predicting local distributions of gas 87 temperature and species concentrations.…”

Detailed simulations for flamelet modelling of SOx formation from coal

“…In a series of papers Wen et al [16][17][18][19] studied laminar counterflow combustion of coal relevant for flamelet modelling. Hara et al [22] performed CP-DNS of a coal particle jet flame using tailor-made homogeneous two-step chemistry. volatile matter composition, homogeneous chemistry, particle size, particle loading, fluid strain, radiative heat transfer), (ii) coal flames are significantly different from pure (non-premixed) gas flames, with the former potentially exhibiting double flame structures with both premixed and non-premixed combustion regimes and (iii) flamlet tabulation methods for PCC should -at least-consider the governing variables total mixture fraction (volatiles + char off-gases), a mixing parameter, progress variable and normalised enthalpy.…”