The work presented in this paper deals with the synchronous multiwavelength
detection of thermal, chemiluminescent and laser-excited (lambda(o)=266nm)
emission from spray of a large saturated paraffin (tetradecane) in auto-ig
niting conditions. Two of these have been selected by varying oxygen molar
fraction (0.13 acid 0.21) of high pressure (2MPa), high temperature oxidant
(900K) stream yielding non-sooting combustion.
The main measured spectroscopic feature was an isolated broadband fluoresce
nce signal detected around lambda=330nm. This signal is here attributed to
aldehyde functionality on the basis of both calibration tests, performed on
liquid aldehydes with the same Optical set-up, and literature data relativ
e to fluorescence and chemiluminescence measurements in simpler conditions.
Furthermore, temporal evolution of this signal, in the conditions reported
here, is consistent with two-step ignition kinetics of paraffins to which
a large production of aldehydes and ketones is related. Chemiluminescence m
aximum, due to HCO and Ct radicals, is slightly delayed with respect to the
fluorescence maximum and is in synchrony with a minimum of the aldehydic s
pecies fluorescence signal. These maxims and minima mark unambiguously the
time interval in which combustion evolves in premixed and diffusion control
led conditions, when pyrolitic species formation occurs.