High-pressure Diesel spray temperature measurements using two-colour laser-induced fluorescence

Abstract

This paper presents a new implementation of an optical technique which aims to measure the temporal and spatial evolution of the liquid temperature of a high injection pressure Diesel spray. Measurements are performed using the two-colour laser-induced fluorescence technique in which a temperature-sensitive fluorescent tracer is added to the fuel (ISO 4113 normafluid in the present case) and all the parameters except the temperature (e.g. tracer concentration, incident laser excitation, droplet number density) are eliminated by processing the ratio of the fluorescence intensity measured on two spectral bands. Diesel sprays, issuing from a single-hole injector, are injected at high pressures ranging from 500 to 1500 bar at a frequency of 10 Hz. The signal acquisition is then triggered on the injection cycle to enable the phase-locked monitoring of the liquid phase temperature. Temperature maps of the spray are presented and the influence of the injection pressure on the droplet temperature can be finally inferred from these results.

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

“…Temperature measurements in sprays: Several studies have more specifically addressed the implementation of the 2cLIF technique in sprays (Bruchhausen et al 2006;Depredurand et al 2011;Labergue et al 2010Labergue et al , 2012aWolff et al 2007). These studies describe how the 2cLIF technique, initially used and validated in the case of single calibrated droplets, should be modified for reliable measurements in sprays.…”

“…Depredurand et al (2011) showed that the size effect is drastically reduced when the dye concentration is increased. A high concentration in dye was also used by Wolff et al (2007) to perform measurements in high-pressure diesel sprays. However, in this work, high concentrations in dye were initially a mean of suppressing MDRs clearly visible both in the red and blue edges of the emission spectrum from droplets seeded with pyrromethene 597-C8.…”

Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays

“…Both intensity images are affected by multiply scattered light, detected as "noisy" fluorescence on the inside of the hollow-cone. Multiply scattered light is a common phenomenon of hollowcone sprays and can only be suppressed by applying SLIPI 12 . The ratio of both intensity images is affected by multiply scattered light as well.…”

“…MDRs occur regardless of the presence of any fluorescent dye. If a fluorescent dye is present, its emission spectrum is changed by the MDRs and reliable 2cLIF thermometry is prevented [2,12,13]. The term MDR describes light being trapped inside a droplet due to almost total internal reflection at the droplet's inner surface and going into resonances.…”

“…Until now, pulsed 2D-2cLIF with MDR-enhanced energy transfer has not been tested on droplets or sprays. However, due to the importance of temperature determination of sprays, more simple 2cLIF setups have been tested: Occurrence of MDRs has only been considered in a single publication [12], where liquid spray temperature is determined point-wise using CW-0D-thermometry. The same type of setup has been used in numerous approaches afterwards, but without consideration of MDR-lasing (e.g.…”