TY - JOUR

T1 - On the universality of ignition delay times of distillate fuels at high temperatures: A statistical approach

AU - KHALED, Fethi

AU - Farooq, Aamir

N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Research reported in this work was funded by King Abdullah University of Science and Technology (KAUST). We are thankful to Prof. Omar Knio (CEMSE Division, KAUST) for helpful discussion on random numbers.

PY - 2019/8/31

Y1 - 2019/8/31

N2 - Ignition delay times (IDTs) of fuels provide very important macro-information about the fuel reactivity and autoignition behavior. IDTs constitute a key metric for fuel/engine co-optimization studies. Chemical kinetic modeling pursuits rely on experimental IDTs as their primary validation target. There have been extensive works in literature on measuring, calculating, modeling and correlating IDTs of a wide range of hydrocarbons, oxygenates, mixtures of pure components and real fuels. Recently, some studies employed a simplified ignition model at high temperatures, comprising of a fast fuel decomposition step and a rate-determining small molecule oxidation step. This description suggests that high-temperature IDT is mainly controlled by the ignition of fuel fragments and is rather weakly dependent on the initial fuel composition. In this work, we study the validity of the hypothesis that IDT of multi-component fuels is weakly dependent on fuel composition under specific thermodynamic conditions. If so, high-temperature IDTs of practical fuels may be described by a universal Arrhenius type correlation. By combining experimental observations and chemical kinetic simulations, we determine the ranges of key parameters (temperature, pressure, equivalence ratio, composition) under which a universal IDT assumption is valid. We conclude that, for fairly random composition and within a P-T-ϕ constraint, IDTs of gasolines and jet fuels may be predicted with a high degree of certainty by the following modified Arrhenius expressions (P = 10–80 bar, P0 = 1 bar, ϕ = 0.5–2, fuel/air mixtures, units are ms, bar, K, mol, kcal): τgasoline=6.76*10−7( [Formula presented] )−1.01φ1.13− [Formula presented] exp( [Formula presented] ), forT> [Formula presented] τjetfuel=4.46*10−7( [Formula presented] )−1.21φ2.04− [Formula presented] *exp( [Formula presented] ), forT> [Formula presented]

AB - Ignition delay times (IDTs) of fuels provide very important macro-information about the fuel reactivity and autoignition behavior. IDTs constitute a key metric for fuel/engine co-optimization studies. Chemical kinetic modeling pursuits rely on experimental IDTs as their primary validation target. There have been extensive works in literature on measuring, calculating, modeling and correlating IDTs of a wide range of hydrocarbons, oxygenates, mixtures of pure components and real fuels. Recently, some studies employed a simplified ignition model at high temperatures, comprising of a fast fuel decomposition step and a rate-determining small molecule oxidation step. This description suggests that high-temperature IDT is mainly controlled by the ignition of fuel fragments and is rather weakly dependent on the initial fuel composition. In this work, we study the validity of the hypothesis that IDT of multi-component fuels is weakly dependent on fuel composition under specific thermodynamic conditions. If so, high-temperature IDTs of practical fuels may be described by a universal Arrhenius type correlation. By combining experimental observations and chemical kinetic simulations, we determine the ranges of key parameters (temperature, pressure, equivalence ratio, composition) under which a universal IDT assumption is valid. We conclude that, for fairly random composition and within a P-T-ϕ constraint, IDTs of gasolines and jet fuels may be predicted with a high degree of certainty by the following modified Arrhenius expressions (P = 10–80 bar, P0 = 1 bar, ϕ = 0.5–2, fuel/air mixtures, units are ms, bar, K, mol, kcal): τgasoline=6.76*10−7( [Formula presented] )−1.01φ1.13− [Formula presented] exp( [Formula presented] ), forT> [Formula presented] τjetfuel=4.46*10−7( [Formula presented] )−1.21φ2.04− [Formula presented] *exp( [Formula presented] ), forT> [Formula presented]

UR - http://hdl.handle.net/10754/656828

UR - https://linkinghub.elsevier.com/retrieve/pii/S001021801930389X

UR - http://www.scopus.com/inward/record.url?scp=85071502327&partnerID=8YFLogxK

U2 - 10.1016/j.combustflame.2019.08.026

DO - 10.1016/j.combustflame.2019.08.026

M3 - Article

VL - 210

SP - 145

EP - 158

JO - Combustion and Flame

JF - Combustion and Flame

SN - 0010-2180

ER -