Abstract
Abstract This study reports the effects of hydrogen (H 2 ) and nitrogen (N 2 ) blended into the fuel on soot evolution and flame temperature in axisymmetric ethylene/air diffusion flames at atmospheric pressure. Two series of laminar ethylene (C 2 H 4 ) diffusion flames blended with H 2 and N 2 were experimentally investigated, in which soot volume fraction ( f v ), primary particle diameter ( d p ) and flame temperature ( T ) were measured using planar laser-based techniques. These twelve flames are grouped into two sets. In the first one, H 2 or N 2 are added into a constant volumetric flow of C 2 H 4 to separate their complementary effects. In the second set, the total volumetric flow rate of the mixture of C 2 H 4 /H 2 /N 2 was kept constant for the same ratios of dilution to isolate the influence of exit velocity. For both sets, a reference flame corresponding to a mixture of C 2 H 4 /H 2 /N 2 = 40%/40%/20%, by volume, was included to match the fuel composition of a turbulent ‘target’ sooting flame (termed the “Adelaide simple jet flame” in the International Sooting Flames Workshop). Planar laser-induced incandescence (LII), time-resolved LII (TiRe-LII) and two-line atomic fluorescence (TLAF) thermometry (using atomic indium as tracer) were applied to measure f v , d p and T . Radial profiles of the flame temperature were also measured using a thermocouple positioned 3 mm above the burner lip, which is just upstream from the sooting region. It is found that dilution either with H 2 or N 2 causes a significant reduction in f v and d p , while the influence on the peak flame temperature is weaker. Flame structure (length and spatial profiles) is also influenced by the blending with H 2 and N 2 . This database can serve as benchmark for model development due to its systematic nature and combination of measured scalars.
Published Version
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