Two-dimensional imaging of fuel-vapour concentration by use of LIEF technique during mixture formation process in a DI diesel engine

Abstract

The laser-induced exciplex fluorescence (LIEF) technique, which is based on spectrally resolved two-colour fluorescent emissions, has been applied to an evaporating diesel spray for the simultaneous separation of liquid and vapour phases on the two-dimensional images. The exciplex system is based on the TMPD/naphthalene system proposed by Melton. The temporal and spatial distribution of liquid and vapour phases during the mixture formation process was detected by this technique. In the LIEF technique, the vapour phase is detected by the monomer fluorescence while the liquid phase is tracked by the exciplex fluorescence. It is able to provide quantitative information on the diffusion state for applying the statistical entropy concept. This concept was put into practice in the image sets obtained through LIEF measurement in order to investigate the diffusion process of vapour phase in the evaporating diesel spray. The laser shadowgraph was taken to deduce the effect of turbulent mixing on the ignition. The experiments were conducted in a direct injection diesel engine with optical access required for the two-dimensional laser imaging. From the results, it is found that ignition occurs in the region where turbulent mixing has advanced a nearly homogeneous mixture of fuel vapour and air. Multi-sectional images obtained by LIEF indicate that there is a spatial dependence of ignition on the vapour-phase fuel in the combustion chamber.

An application of digital image processing techniques to the characterization of liquid petroleum gas (LPG) spray

“…However, optical techniques are generally considered to be the best, since they are nonintrusive. Among many optical techniques such as laser scattering, PIV (particle image velocimetry), PDI (phase Doppler interferometry), LDV (laser Doppler velocimetry) and photographic imaging and so on [6][7][8][9][10][11][12][13], schlieren photography [14] is particularly suitable for the quantification of geometrical characteristics of LPG spray, for its lower costs and its ability to allow observation of the gas. Furthermore, with the help of digital image processing techniques, the quantitative geometrical spray characteristics can be obtained more quickly and with the same accuracy as with manual measurement [12].…”

Spray measurement technology: a review

“…Laser-induced exciplex fluorescence (LIEF) has been used successfully for both visualization [107][108][109] and quantitative measurements with both diesel-like (TMPD-napthalene [110][111][112][113][114][115][116][117]) and gasoline-like (FB-DEMA [87,[118][119][120][121][122]; TEA-benzene [120,123]) tracer-fuel mixtures. One complication is that the broadband exciplex fluorescence from the liquid usually overlaps some or all of the vapor fluorescence band.…”

Temperature and chemical composition of droplets by optical measurement techniques: a state-of-the-art review

“…In many applications of LIEF to droplet measurements, this feature is used to discriminate between the liquid and gaseous phases. Ultimately this has been exploited for quantifying the amount of liquid still present in evaporating sprays (Desantes et al 2005;Fansler et al 2009;Felton et al 1993;Fujimoto et al 2002;Ghandhi et al 1994). In works dealing with vapor/liquid visualization, an excess of the ground state partner G is usually introduced to suppress the monomer in the liquid in favor of the exciplex (Melton 1983).…”