Comprehensive characterization of sooting butane jet flames, Part 2: Temperature and soot particle size

Abstract

The present work investigates the effect of jet-exit Reynolds number (Re) on soot particle size and flame temperature in n-butane jet flames. Correlation of temperature with soot volume fraction (f v ), soot precursor (polycyclic aromatic hydrocarbons or PAH), and reaction zone (OH) is also examined. The investigated flames (Re = 5000 to 21500) are identical as of the companion work (Part 1). The temperature was measured in a low-sooting region using a fine-wire thermocouple. The soot particle size distribution was obtained using a scanning mobility particle sizer (SMPS). Temporal evolution (with 0.1 s resolution) of f v in the extracted aerosol sample was monitored with a Pegasor particle sensor (PPS). f v from LII and PPS are compared, and the reasons for differences are discussed in detail. The radial location of peak temperature is biased towards the fuel-rich side. At Re 5000, peak-PAH occurs at 650 K, whereas in lifted turbulent flame (Re 21500), peak-PAH shifts to 940 K. PAH formation temperature is influenced by air/fuel mixing. Despite the variation of turbulence level (Re = 5000 -21500), peak-f v in the soot inception region occurs at a nearly identical temperature of 1400 K. Peak-f v shifts towards lower temperature with increasing height, likely due to oxidation by diffused OH. The soot mode diameter (D m ) was measured along the axis. D m increases with height and reaches a maximum near peak-f v region. D m at moderate Re