Forced ignition of dispersions of liquid fuel in turbulent air flow

Abstract

© 2017 by Pedro M. de Oliveira. This work consists of an experimental investigation of the early phase of ignition in uniformly dispersed kerosene droplets carried in a turbulent air flow. Ignition was achieved by focusing a laser beam. Jet A and two other alternative fuels for aviation were assessed in terms of the probability of igniting a small kernel, the probability of producing a selfpropagating flame, and the flame speed. Overall, all fuels showed high kernel ignition probability due to the high laser energy used. However, although a kernel was formed in most ignition attempts, its growth varied considerably between the three fuels and with changes in equivalence ratio, temperature, and flow velocity. Thus, the probability of ignition varied between 100% and 0% for overall lean conditions, with Jet A being the most difficult to ignite among the three fuels. The flame speed also showed considerable variations between the fuels at the same conditions with Jet A being the slowest, attributed to the smallest degree of evaporation achieved at the spark location with this fuel.