Applications and evaluation of two-line atomic LIF thermometry in sooting combustion environments

Temperature measurements using planar laser-induced fluorescence (PLIF) are most often associated with experimental challenges. In addition, no PLIF technique is generally applicable in all kinds of environment. Especially under sooting conditions problems are prone to arise, which limits the use of these techniques. In this paper the two-line atomic fluorescence (TLAF) technique was investigated in sooting environments. Indium atoms were used as thermometry species and seeded into the combustion region. Data from two-dimensional measurements are often difficult to analyse, because of problems with treating noise. A statistical analysis method for correction of laser fluctuations was developed to increase the precision of the temperature calculations. The results show that TLAF holds promise for temperature measurements in rich combustion, such as diesel engines, where other techniques have proven to fail. Drawbacks with the TLAF technique are that the probe volume is biased towards the post-flame zone and that seeding is required. The statistical analysis improved the precision considerably and is suitable for evaluation of other two-dimensional thermometry techniques. This paper also presents a critical review and comparison with alternatives, such as OH and NO thermometry.