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Abstract
Tunable excimer lasers are used to obtain 2-D images to analyse spatial distributions of different species in a liquid fuelled flame of a single burner model combustor with optical access from all sides at ambient pressure and a maximum air inlet temperature of 600 K. The flame is stabilised by a turbulent structure generated by air mixing jets in combination with the axial swirls of an air spoke injector
The spatial structure of the flame is characterized by relative distributions of different species. Measurements of natural fluorescence of OH (without laser) and laser-induced fluorescence (LIF) of NO and vaporized n-heptane fuel as well as laser-induced predissociative fluorescence (LIPF) of OH are presented. Averaged temperature field measurements are performed based on sequential excitation of two rovibronic transitions in the Schumann-Runge band system of O2. Liquid fuel droplets are visualized by Mie-scattering. Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species and to study the natural flame emissions. The averaged fluorescence distributions turned out to be highly reproducible and illustrate clearly the fuel evaporation and consumption process as well as the area of NOx formation within the flame. The obtained flame spectra indicate that the formation of prompt NOx plays an important role in the precombustion zone where the mixture is still rich and the flame-temperature is low