Investigation of soot formation in fuel-rich premixed propane/air microcombustion at low temperatures

The advantage of micro/meso combustion includes higher efficiency, improved heat and mass transfer, swift startup and shutdown when compared with regular combustion. This study aims to investigate the critical sooting equivalence ratio and soot precursor formation in a micro-flow reactor with a controlled temperature profile of diameter 2.3mm and their dependence on the temperature ranging from 800-1250 °C. The equivalence ratio is varied from 1-13 and flow rates of 10 and 100sccm were investigated. Also, nitrogen is used to study the effect of inert gas dilution. A gas chromatograph is used to study the exhaust gas composition. The reactor is analyzed visually for the traces of soot particles before and after combustion, each time the temperature and/or equivalence ratio is varied. From 750-950°C, no soot is indicted at all equivalence ratios even up to 100. The inert gas dilution helped in raising the critical sooting equivalence ratio as expected because of the lower temperature. The results indicated an opposite trend to what has been well understood for the pre-mixed sooting flames, i.e., decreasing temperature decreases soot formation. The capability of the reactor to examine the effects of temperature on the critical sooting equivalence ratio at different flow rates has been successfully demonstrated.