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

摘要

The present work investigates the effect of jet-exit Reynolds number ( Re ) on soot particle size and flametemperature 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 investigatedflames ( Re = 5000 –21,500) are identical as of the companion work (Part 1). The temperature wasmeasured in a low-sooting region using a fine-wire thermocouple. The soot particle size distribution wasobtained using a scanning mobility particle sizer (SMPS). Temporal evolution (with 0 . 1 s resolution) off v in the extracted aerosol sample was monitored with a Pegasor particle sensor (PPS). f v from LII andPPS are compared, and the reasons for differences are discussed in detail. The radial location of peaktemperature is biased towards the fuel-rich side. At Re 50 0 0 , peak-PAH occurs at 650 K, whereas inlifted turbulent flame ( Re 21,500 ), peak-PAH shifts to 940 K. PAH formation temperature is influencedby air/fuel mixing. Despite the variation of turbulence level ( Re = 5000 ? 21,500 ), peak- f_v in the sootinception region occurs at a nearly identical temperature of 1400 K. Peak- f_v shifts towards lower temperaturewith increasing height, likely due to oxidation by diffused OH. The soot mode diameter ( D_m ) wasmeasured along the axis. D_m increases with height and reaches a maximum near peak- f v region. D_m atmoderate Re ( 5000 ? 7200 ), varies between 12 and 28 nm along the flame axis. At high Re (21,500), D_mrange decreases to 12 ? 24 nm . The decrease in peak- D_m with Re is likely due to reduced residence timeand enhanced reactant mixing. The comprehensive database containing a wide range of parameters fromthe present and companion (Part 1) papers will aid in the development and validation of turbulence andsoot chemistry models, especially for fuels of practical relevance.