Temperature measurements using exciplex fluorescence with TMPD and methylnaphthalene as tracers

Other conference contribution, 2008

Laser-induced exciplex fluorescence has been used to measure the temperature in a spray of a diesel-like fuel. To a model fuel consisting of 70 % n-decane and 30 % 1-methylnaphthalene, TMPD was added in a concentration of 0.2 %. When excited with UV-light TMPD efficiently forms an exciplex with methylnaphthalene fluorescing with a peak intensity at a wavelength around 505 nm at room temperature. When the temperature of the fuel increases the peak position shifts to shorter wavelengths, and the peak reaches a position of 475 nm at 150 ºC. This shift of the fluorescence spectrum can be used to estimate the temperature of the liquid fuel, by measuring the fluorescence light intensity in two different wavelength intervals and evaluate the ratio between them as a function of temperature. The intensity ratio as a function of temperature was evaluated and calibrated, and subsequently used to determine the temperature of the liquid fuel along the spray axis.