Laser ignition of flammable mixtures via a solid core optical fiber

To date no commercial fiber coupled laser systems have reached the irradiance and pulse energy required for flammable mixtures ignition. In this work we report preliminary results on the ignition of two-phase mixtures promoted by a laser delivering pulses through optical fiber. Experiments undertaken on free beam path configurations have allowed identification of the optical parameters required for laser ignition. The fiber coupled system used is based on a Q-switched nanosecond laser operating at 1064 nm. The fiber input angle and the focal length have been identified as the most important parameters. We demonstrated the possibility of delivering nanosecond pulses of 30 mJ focused onto a spot of 200 mu m through a solid core optical fiber, and to promote ignition of n-heptane/air and JP4/air mixtures.