Radiative Fraction and Flame Length of Propane Jet Diffusion Flames in a Crossflow
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Radiative Fraction and Flame Length of Propane Jet Diffusion Flames in a Crossflow J.-W. Wanga,b , J. Fanga , J.-F. Guanb , L.-Y. Zhaoa , S.-B. Lina , H. R. Shaha , Y.-M. Zhanga , and J.-H. Suna
UDC 536.46
Published in Fizika Goreniya i Vzryva, Vol. 56, No. 4, pp. 5–13, July–August, 2020. Original article submitted January 9, 2020; revision submitted February 19, 2020; accepted for publication February 19, 2020.
Abstract: Many industrial combustion devices rely on jet flame combustion in the crossflow to achieve mixing and reaction. Previous research offers a limited predictive capability regarding the coupling effects of the crossflow and jet flow on the flame radiative fraction. In this work, a new theoretical equation is derived to relate the radiative fraction to the fuel flow rate and the crossflow velocity. The experimental results show that the flame length increases as the crossflow velocity increases for all considered flames. The results of this work suggest that the stretching factor is 0.08 s. The radiative fraction is almost independent of the nozzle diameter in the case of a low crossflow velocity. The crossflow has the strongest effect on the radiative fraction for a smaller nozzle diameter. This is because of the effect of the crossflow and jet flow velocities on the soot residence time, which is proportional to the radiative fraction. Keywords: crossflow, propane, radiative fraction, soot, turbulent diffusion flame. DOI: 10.1134/S0010508220040012
INTRODUCTION Studies of the jet flame in a crossflow have been undertaken in a wide range of applications, such as gas turbine combustors, industrial boilers, and flare stacks. In practical engineering, characteristics of the flame in crossflows, such as flame radiative fraction, flame length, and tilt angle, are critical. Radiation heat emitted by flames is closely related to the thermal stability of combustors, and it must be evaluated to design safe flare systems in the power engineering and petrochemical industry. Most of the previous studies have been focused on predicting the flame length or trajectory, temperature, and radiative fluxes for the reacting jet in the crossa
State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui, 230026 China; [email protected]. b Hefei Institute for Public Safety Research, Tsinghua University, Hefei, Anhui, 230601 China.
flow [1]. Escudier [2] presented numerical calculations for the variation of temperature and species concentrations along the plume trajectory. Brzustowski [3] modelled the flame as a bent-over of an initially vertical and non-buoyant circular jet with top-hat profiles of the composition, temperature, and velocity. Fairweather et al. [4] predicted the radiative heat flux from field-scale flares and showed that an increase in the crossflow speed first reduces the soot level, but eventually lead to its increase once the critical crossflow speed is exceeded. This might be attributed to the crossflow, which at first enhances air entrainment into the flame, causing a decrease in the residence times for so
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