Autoignition of butanol isomers/n-heptane blend fuels on a rapid compression machine in N-2/O-2/Ar mixtures

作者：Yang Zheng; Wang Yue; Yang Xin; Qian Yong; Lu XingCai^*; Huang Zhen

来源：Science China Technological Sciences, 2014, 57(3): 461-470.

DOI：10.1007/s11431-014-5475-7

• butanol isomers
• blend fuels
• ignition delay
• rapid compression machine
• chemical kinetics

Ignition delay times of butanol isomers/n-heptane mixture were measured using a rapid compression machine at compressed pressures of 15, 20 and 30 bar, in the compressed temperature range of 650-830 K and equivalence ratio of 1.0. Sensitivity analysis and reaction fluxes analysis were performed using a detailed mechanism of blend fuels so as to evaluate the impact of n-heptane addition and temperature variation on the ignition and combustion process. Over the experimental conditions in this study, the blend fuels displays apparent low and high temperature reactions and a negative-temperature-coefficient (NTC) behavior. With increasing butanol isomers mole fraction in the mixtures, the ignition delay times increase. It is worth noting that the suppression to n-heptane ignition from tert-butanol is very limited. The ignition delay time of 40/60 tert-butanol/n-heptane mixture is smaller than other three kinds of blends. With the increasing of tert-butanol mole fraction, the increasing range of its ignition delay time is very large. Moreover, compressed pressure has a limited effect on the ignition of blend mixture at low temperature but certain influence at medium temperature arrange. Tert-butanol/n-heptane mixture is not sensitive to the pressure. The chemical analysis indicates that butanol isomers also present the NTC behavior because of the low temperature reactivity radicals pool produced by n-heptane. Reaction fluxes analysis shows that the n-heptane addition has little impact on the reaction path. Sensitivity analysis shows that for the pure n-butanol, 2-butanol and iso-butanol fuel, H-abstraction from the alpha-carbon plays the dominant role in the reactions having the inhibiting effect on the low-temperature branching, while the H-abstraction from the gamma-carbon can promote the ignition; for tert-butanol/n-heptane mixtures, reaction R16. H2O2( M)aOE (c)=> OH OH( M) plays the leading role. For n-butanol/n-heptane, iso-butanol/n-heptane mixtures, the major promoting reactions include some H-abstraction from n-heptane and OH branching reactions, the influence of H-abstraction from alpha-carbon is weaken; For 2-butanol/n-heptane, tert-butanol/n-heptane mixtures, R16 plays an absolutely dominant role, while the major inhibiting reactions add some elementary reactions of small radicals.

• 出版日期2014-3
• 单位上海交通大学