Multi-species detection in spray flames with tunable excimer lasers

Abstract

Planar imaging with tunable excimer-laser sheet illumination is used to determine spatial distributions of different species in liquid-fuelled spray flames of commercial oil burning furnaces. Two burner configurations, which differ only in the fuel/air mixing devices, are investigated to understand why one configuration yields 30% less NOx emission. Iso-octane and n-heptane fuels are used. To understand the origin for NOx reduction spatial distributions of reactants (fuel, O2), the reaction intermediate OH and the pollutant NO are recorded. OH and O2 are measured by LIPF, NO by LIF. Fuel distributions are determined by another broad-band emission, whose origin is not yet identified. Both single shot and averaged distributions are recorded. The averaged distributions are extremely reproducible and depend sensitively on details of the burner geometry and the fuel/air mixing device. They can clearly be used to distinguish fine details in different injection systems. The spatial distribution of different species relative to each other yield considerable insight in the differences between the two combustion processes. On the basis of purely qualitative visualization it is possible to understand the origin for NOx reduction: it results from faster injection of air in the one fuel/air mixing device.