Aerodynamic and fuel dilution effects on non-premixed gas jet flames

This study examines the changes in the flame structure and emissions from
laboratory-scale flares over a wide range of test conditions.
In the initial study, the experimental measurements examined the effect of
varying the fuel jet velocity on the flame temperature, flame structure, and the inflame
and post-flame composition of species in methane flames. The test conditions
involved laboratory-scale flares in the attached and lifted regimes under laminar,
transitional and turbulent conditions. The results show that while an increase in the
jet velocity leads to an increase in EINOx, this also leads to a decrease in EICO, and
similarly, EICO decreases with decreasing flame luminosity and sooting propensity.
The second study examined the effect of CO2 dilution on methane jet flames
where CO2, which was used as a diluent, was injected into the fuel-jet stream. The
dilution-induced extinction was achieved by fixing the fuel flow rate, while varying
the diluent mole fraction. The effect of the changes in the flame length, lift-off
height, and in the emissions due to this dilution was studied. Amongst other
findings, this study shows that CO2 is effective in reducing the EINOx in the postflame
region of methane jet flames at Reynolds number ranging from 1584 to
14254, and that soot formation is suppressed at higher diluent concentrations in the
jet flame.
The final study involved the characterisation and the comparison of the inflame
composition of major species and the post-flame soot and pollutant emissions
generated from the combustion of methane and propane flames. The results show
that the dilution of the fuel stream with CO2 reduces the size of soot aggregates in
propane flames and that the soot emission factor decreases at increased diluent
concentrations. In addition, for the same test conditions utilised in this study, the
EICO and EINOx are higher in methane flames than in propane flames.