Multi-line OH-LIF for gas-phase temperature and concentration imaging in the SpraySyn burner

Gas-phase temperature and OH concentration images are measured in the SpraySyn nanoparticle-synthesis standard burner using multi-line OH laser-induced fluorescence (LIF) thermometry. In this burner, a spray flame fed by a combustible nanoparticle precursor solution is stabilized by a surrounding axisymmetric lean premixed laminar methane/oxygen pilot flame. For measuring OH rotational temperature, the laser is scanned across the 282.05-282.17 nm range and LIF excitation spectra are fitted for each image pixel by simulated spectra. Temperature maps are determined for the pilot flame and the ethanol spray flame with variable dispersion gas flow rates of oxygen used in the two-fluid nozzle. The addition of 2-EHA (2-ethylhexanoic acid) to the solution was found to increase the flame temperature. Laser attenuation across the flame was measured using simultaneous recordings of the fluorescence of uranine/water solution from two dye cuvettes illuminated with the laser sheet before and after the flame and the effect of attenuation was quantified. Absolute OH concentration distributions are determined by combining the LIF images, laser attenuation measurements, and derived temperature distributions. The temporal stability of the flame is investigated for various operating conditions by statistical evaluation of recorded instantaneous OH-LIF images.