Hydrocarbon species concentrations in nitrogen diluted ethylene-air laminar jet diffusion flames at elevated pressures

Hydrocarbon species concentrations are measured in a laminar jet diffusion flame at elevated pressures with the objective of better understanding soot production and oxidation mechanisms, which will ultimately lead to a reduction in soot emissions from practical combustion hardware. Samples were extracted from the centerline of an ethylene flame diluted with nitrogen. The diluted fuel and co-axial air top-hat exit velocities were matched and the mass fluxes were held constant at all pressures. This paper reports centerline concentration profiles of major non-fuel hydrocarbons and 5 different PAH species measured via extractive sampling with a quartz microprobe and quantification using GC/MS + FID. The peak concentration of acetylene decreased with increase in pressure, suggesting rapid conversion to heavier compounds, whereas the concentrations of the other major heavier non-fuel hydrocarbons increase with an increase in pressure. The measured peak species concentration as a function of pressure is seen to closely follow a power law function, Pn, where n varies from less than zero for acetylene, propane and diacetylene to greater than unity for the larger PAH species.