Laminar Burning Speed of n-Hexane-Air Mixtures
n-Hexane is an easy-to-use fuel for laboratory investigations of hydrocarbon vapor explosions and has been used widely as a surrogate for commodity fuels such as kerosene. As part of our ongoing studies into flammability hazards in aircraft environments, we have been carrying out experiments at reduced pressure, below 100 kPa, in order to measure ignition and flame propagation in n-hexane-air mixtures. The objectives of the present study were to study experimentally the effects of composition, initial temperature, and initial pressure on the burning speed of n-hexane-air mixtures. Our study expands on and complements existing data and compares the experimental measurements with numerical predictions from various chemical models. The laminar burning speed of n-hexane-air mixtures was measured experimentally using the spherically expanding flame technique. The effects of equivalence ratio, initial temperature and initial pressure were investigated in the ranges: Φ = 0.75–1.7, T_1 = 295–380 K and P_1 = 40–100 kPa, respectively. A typical inverted U-shaped curve was obtained for the evolution of the burning speed as a function of equivalence ratio. At a fixed composition, the burning speed increases as the initial temperature increases and as the initial pressure decreases; this is in agreement with previous burning speed studies done using n-alkanes, from C_5 to C_8. Three detailed reaction models, the JetSurF model, the model of Ramirez et al., and the Caltech model were evaluated with respect to the present data. The present study indicated that among the models tested, the JetSurF model is the most accurate model for evaluating n-hexane-air mixtures.
© 2013 Curran Associates, Inc. Paper # 070LT-0383. The authors would like to thank Professor Guillaume Blanquart from Caltech for generously providing us with the Caltech reaction model. The present work was carried out in the Explosion Dynamics Laboratory of the California Institute of Technology and was supported by The Boeing Company through a Strategic Research and Development Relationship Agreement CT-BA-GTA-1.