TY - JOUR

T1 - Experimental investigation and modeling of boundary layer flashback for non-swirling premixed prevaporized n-propanol/air and /isopropanol/air flames

AU - Bajrami, Julian

AU - Zimmermann, Paul

AU - Dinkelacker, Friedrich

N1 - Publisher Copyright: © 2024 The Author(s)

PY - 2024

Y1 - 2024

N2 - The idea of utilizing lean, premixed and prevaporized (LPP) combustion could be a step towards sustainable aviation in the future, with the absolute absence of soot particles and very low nitrogen oxide emissions. However, premixing with compressed hot air presents a challenge for both conventional jet fuel and synthetically produced sustainable aviation fuel (SAF) due to self-ignition and flashbacks. Our group is thus seeking LPP-compatible advanced sustainable aviation fuels, which are evaluated based on their flashback propensity. Preliminary studies indicate that short-chain alcohols, with their higher ignition delay times and lower flame velocities, may be appropriate for LPP combustion concepts. In this study, the isomers of propanol, n-propanol, and isopropanol, are the first representatives of the short-chain alcohols to be investigated experimentally and numerically with respect to their flame stability limits. The experimental determination of stability limits for n- and isopropanol/air premixed flames was conducted on a generic, non-swirled atmospheric burner for an equivalence ratio range of 0.82 to 1.11. A fully automated measurement procedure was used to generate 119 measurement points with Reynolds numbers in the range from 1430 to 2750. The influence of the positional isomerism and of the preheat temperature (422 K, 446 K and 466 K) of the unburned mixture are investigated. A clear influence of the isomeric fuel structure is found. A theoretical analysis shows that it can be related to the different laminar flame speed and laminar flame thickness of the isomers. Moreover, a detailed analysis shows that the critical velocity gradient concept to describe boundary layer flashback is well usable with a Péclet number model.

AB - The idea of utilizing lean, premixed and prevaporized (LPP) combustion could be a step towards sustainable aviation in the future, with the absolute absence of soot particles and very low nitrogen oxide emissions. However, premixing with compressed hot air presents a challenge for both conventional jet fuel and synthetically produced sustainable aviation fuel (SAF) due to self-ignition and flashbacks. Our group is thus seeking LPP-compatible advanced sustainable aviation fuels, which are evaluated based on their flashback propensity. Preliminary studies indicate that short-chain alcohols, with their higher ignition delay times and lower flame velocities, may be appropriate for LPP combustion concepts. In this study, the isomers of propanol, n-propanol, and isopropanol, are the first representatives of the short-chain alcohols to be investigated experimentally and numerically with respect to their flame stability limits. The experimental determination of stability limits for n- and isopropanol/air premixed flames was conducted on a generic, non-swirled atmospheric burner for an equivalence ratio range of 0.82 to 1.11. A fully automated measurement procedure was used to generate 119 measurement points with Reynolds numbers in the range from 1430 to 2750. The influence of the positional isomerism and of the preheat temperature (422 K, 446 K and 466 K) of the unburned mixture are investigated. A clear influence of the isomeric fuel structure is found. A theoretical analysis shows that it can be related to the different laminar flame speed and laminar flame thickness of the isomers. Moreover, a detailed analysis shows that the critical velocity gradient concept to describe boundary layer flashback is well usable with a Péclet number model.

KW - Boundary layer flashback

KW - Experimental data

KW - Flame stability

KW - Modeling

KW - Premixed propanol/air flames

UR - http://www.scopus.com/inward/record.url?scp=85199299637&partnerID=8YFLogxK

U2 - 10.1016/j.proci.2024.105567

DO - 10.1016/j.proci.2024.105567

M3 - Article

AN - SCOPUS:85199299637

VL - 40

JO - Proceedings of the Combustion Institute

JF - Proceedings of the Combustion Institute

SN - 1540-7489

IS - 1-4

M1 - 105567

ER -