Shock tube study on auto-ignition characteristics of kerosene/air mixtures

Abstract

Ignition delay times are obtained for kerosene/air mixtures behind the reflected shock waves at temperatures between 1445 and 1650 K, at a pressure of 0.11 MPa and an equivalence ratio of 1.0. A nebulization device with Laval nozzle is used to nebulize kerosene and form an aerosol phase, which evaporates and diffuses rapidly behind the incident shock waves. Mixtures auto-ignite behind the reflected shock waves. An ICCD is used to visualize the kerosene/air mixture’s ignition characteristics. The mixture’s ignition intensity increases with increase in initial temperature. Continuous and irregular flames exist below 1515 K while plane and discontinuous flames exist over 1560 K. Ignition delay times decrease with increase in initial temperature. Experimental data shows good agreement with results reported previously in the literature. A new surrogate (consisting of 10% toluene, 10% ethylbenzene and 80% n-decane) is proposed for kerosene. Honnet et al.’s mechanism is used to simulate the ignition of kerosene with calculations agreeing well with the experimental data. The sensitivity of reaction H+O2⇔OH+O, which shows the highest sensitivity to the ignition delay time, increases with an increase in temperature. The chain breaching reaction of CH3 with O2 accelerates the total reaction rate and the H-atom abstraction of n-decane controls the total reaction rate. The rate of production and instantaneous heat production indicate that two reactions, H+O2⇔OH+O and O+H2⇔OH+H, are the key reactions to the formation of OH radicals, as well as the main endothermic reaction. However, the reaction of R3 is the main heat release reaction during ignition. Flame structure analysis shows that initial pressure is increased slightly as CO and H2O will appear before main ignition.