LASER IGNITION IN A LEAN PREMIXED PREVAPORIZED INJECTOR

Abstract

Laser-induced spark ignition has proved to be an alternative way of achieving ignition. In this paper, we demonstrate the feasibility of laser spark ignition at the outlet of a lean premixed prevaporized injector, similar to those used in low-NO_x air jet engines. This injector uses liquid n-heptane as fuel in preheated air with a high level of turbulence. After a description of the combustion facility and of the experimental setup, experimental results are presented and discussed. Special attention is paid to ignition energy thresholds for various positions of the focusing point in the combustion chamber. The influence of energy level on ignition probability is also presented. Finally, shadowgraphy visualization with a high-speed camera of one ignition event is presented and discussed.

Keywords:

• laser ignition
• laser breakdown
• premixed prevaporized injector

K. Zähringer is currently at Lehrstuhl für Strömungsmechanik und Strömungstechnik, Otto-von-Guericke-Universität Magdeburg, Postfach 4120, D-39016 Magdeburg, Germany.

Notes

λ: Laser beam wavelength; MIE: minimum ignition energy; τ_FWHM : full width at half maximum pulse duration; f : focal length.

*20% CO₂.

^†40% CO₂.

^‡21% O₂, 79% He.

^§21% O₂, 79% Ar.