Abstract
Keywords
Diesel Combustion, Optical Diagnostics, Soot Fornation, Thermometry/ Pyrene-LIF
Abstract
In order to investigate early soot formation process in diesel combustion, spectral analysis and optical thermometry of early soot formation region in a transient spray flame under diesel-like conditions was attempted vis laser-induced fluorescence (LIF) from pyrene (C16H10) doped in the fuel. Pyrene is known to exhibit a temperarure dependant variation of LIF spectrum: the ratio of S2/S1 fluorescence yields, from the second/lowest excited singlet stated, depends on temperature. In the present study, pyrene was doped in a model diesel fuel and the variation of LIF spectra from the pyrene in the spray flame were examined at different ambient temperatures, ambient oxygen concentrations, measurement positions and timings after start of fuel injection. The pyrene LIF spectra measured in spray flame up to ignition showed increase in the S2/S1 ratio of LIF intensity and shift of peak wavelength of S1 towards red as the time progresses after start of injection, showing that the temperature variation of the gas mixture up to ignition can be captured by this technique. The LIF spectra after ignition showed increase in emission intensity in longer wavelength region due to LIF from combustion products.