Endoskopische laserinduzierte Fluoreszenz in der Brennverfahrensentwicklung

Wensing, Michael; Günther, Michael; Zboralski, André; Liebsch, S.

doi:10.1007/s35146-014-0364-y

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…One option is laser-induced fluorescence (LIF), which is an established diagnostic for determining the local air/fuel ratio in the gas phase. 4–8 This very sensitive method has the potential to detect even small amounts of liquid fuel inside the intake manifold of engines with port fuel injection (PFI) 9,10 or the combustion chamber of engines with GDI. 11–13 However, quantification of the LIF signal at elevated pressures and temperatures still needs improvement.…”

Section: Introductionmentioning

confidence: 99%

Development of laser-induced fluorescence to quantify in-cylinder fuel wall films

Geiler

Grzeszik

Quaing

et al. 2017

International Journal of Engine Research

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Laser-induced fluorescence of a fuel tracer is a very sensitive technique to image in-cylinder liquid fuel films, but quantification of the measured film thickness has proven difficult so far. This article describes improvements in the quantification procedure and presents an example application in a motored, optically accessible spark-ignition engine with direct injection. We designed a calibration tool that could be pressurized and heated, allowing investigation of the laser-induced fluorescence intensities at temperatures exceeding the liquid's standard-pressure boiling point. The fluorescence intensity of liquid toluene and 3-Pentanone dissolved in isooctane upon excitation with a pulsed laser at 266 nm was investigated as a function of temperature and pressure. Consistent with the literature results on gas-phase laser-induced fluorescence, the signal from toluene was much stronger than from 3-Pentanone, about two orders of magnitude for films thinner than 50 mm. Laser-induced fluorescence from both tracers decreased with increasing temperature but that of toluene significantly more. The response to pressure was less pronounced. For imaging across a large field of view, the spatial non-uniformity of laser excitation and detection efficiency was taken into account using a solid fluorescing substrate, an inexpensive Schott-glass WG280 filter. Isooctane with 0.5 vol.% toluene was used for application in the motored engine, imaging the liquid film on the piston-top window after direct injection from a central multi-hole injector. Air as a bulk gas was found to be advantageous over nitrogen in that gas-phase fluorescence was quenched by oxygen. The imaged film distributions and thicknesses and the derived total fuel film mass were physically plausible. Consistent with the recent literature results from a constant pressure vessel, increasing injection pressure from 50 to 100 bar did not decrease wall wetting but further increase to 200 bar did.

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