Effect of hydrogen enrichment of laminar ethylene diffusion flames on thermal structure and soot yields at pressures up to 10 bar

Soot formation in turbulent flames of ethylene/hydrogen/ammonia

“…In this study, the amount of dilution is the same for all conditions. An increase in flame temperatures could help to explain the increased soot production in H2 flames, although measurements in laminar flames generally show that the change in temperature for small amounts of H2 addition is negligible [12][13][14]. Moreover, the global heat release rates are nearly identical between the 12.5% NH3 and 12.5% H2 cases, yet these flames result in very different outcomes in terms of soot production.…”

“…Also, effects of differential diffusion may be ruled out by comparing with equivalent amounts of helium substitution [16]. On the other hand, Yang et al [14] have argued that the small molecular diffusivity of H2 allows it to leak through the reaction zone in some cases and this effect could reduce the dilution effect, especially in turbulent non-premixed flames. Nonetheless, the bulk of evidence suggests a chemical effect is the most likely explanation for the trends observed in this study.…”

“…However, measurements by Sun et al [13] in C2H4 laminar coflow diffusion flames showed that N2 is more effective at reducing soot than H2. More recently, Yang et al [14] studied H2 and He addition to C2H4/N2 laminar coflow diffusion flames at pressures up to 10 bar, concluding that the observed soot suppression associated with H2 addition is not a result of direct chemical interaction. With methane simulations of laminar coflow diffusion flames in air (21% oxygen), helium was more effective than H2 at reducing levels of soot [15].…”