Droplet Velocity Measurements in Direct-Injection Diesel Sprays Under High-Pressure and High-Temperature Conditions by Laser Flow Tagging

Wissel, S.; Hoffmann, Thomas; Hottenbach, Peter; Koß, Hans-Jürgen; Pauls, Christoph; Grünefeld, Gerd

doi:10.4271/2008-01-0944

Cited by 6 publications

(5 citation statements)

References 9 publications

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“…This excitation wavelength is not easily generated from standard commercially available lasers, and requires a wavelength-tunable (dye) laser or a KrF excimer laser. Excitation by frequency-quadrupled Nd:YAG laser radiation at 266 nm is possible, as shown in previous work, 4,5 but the efficiency is poor compared to the europium solution, which might lead to problems at the low imaging exposure times required for the investigations of high-velocity sprays. The europium solution can be excited efficiently using a standard frequency-tripled Nd:YAG laser, and it has a large emission intensity compared to the terbium-DPA solution.…”

Section: Spectral Propertiesmentioning

confidence: 76%

“…Laser-induced phosphorescence (LIP) has been used as a diagnostic tool for investigating flows for over a decade. 3,4 The characteristic long lifetime of phosphorescence, in the order of milliseconds, caused by efficient intramolecular transfer of energy to a metastable state after electron excitation, allows for flow tracking in sprays. 5,6 However, the usefulness of phosphorescence in sprays depends on the tracer/molecule used.…”

Section: Introductionmentioning

confidence: 99%

“…Krüger and Grünefeld 3 used a Tb-DPA complex to study spray formation by adding the molecules in low concentration to a liquid spray and tracking excited lines to obtain a spray velocity field. More recently, Wissel 4 and Brands et al 5 used terbium molecular complexes to determine spray velocities by tagging a part of the spray close to the nozzle and tracking the movement of the glowing fluid, showing that measurements are possible even in highspeed sprays. In previous work, 6 we have used an europium complex to investigate spray breakup and dispersion through phosphorescent fluid tracking, showing that even the small droplets (<10 µm) in a spray can be tracked over time using phosphorescence at velocities of 150 m/s.…”

Section: Introductionmentioning

confidence: 99%

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Lanthanide-based laser-induced phosphorescence for spray diagnostics

Voort

Maes

Lamberts

et al. 2016

Review of Scientific Instruments

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Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (∼1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

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Section: Spectral Propertiesmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lanthanide-based laser-induced phosphorescence for spray diagnostics

Voort

Maes

Lamberts

et al. 2016

Review of Scientific Instruments

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“…Because of this, the formation and structure of the diesel fuel jet can vary greatly. techniques include laser anemometry [6], holography [7], schileren imaging [8,9], shadowgraphy [10,11], reflection and scattering [12][13][14][15], laser flow tagging [16], ballistic imaging [17,18], and x-ray imaging [19,20].…”

Section: Diesel Spraysmentioning

confidence: 99%

High-frame-rate planar laser-induced fluorescence imaging of diesel sprays using pulse burst diagnostics

Fuller¹

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A planar laser-induced fluorescence technique for spatially and temporally resolving individual diesel fuel injection events into various gas temperatures and pressures was demonstrated. An optically accessible chamber of constant temperature and pressure was used to create the desired thermodynamic state of gas. The chamber was capable of achieving typical thermodynamic states seen at top dead center of the compression stroke in a four stroke diesel engine. The third harmonic of an Nd:YAG laser supplied excitation near 355 nm, which was provided at high frequencies using a pulse-burst diagnostic scheme. Individual pulses of 35 mJ in energy and 10 ns in duration were provided at rates of 10 kHz and 20 kHz. The UV laser beam was passed through a calibration cell filled with a laser dye, which was used for spatially correcting variations in individual laser pulses. The technique demonstrated that individual species concentrations can be temporally resolved using pulseburst lasers.

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“…LIP can be used for relatively long-lifetime (ms) applications, such as flow tracking. 3,4 In particular, single-phase phosphorescent tracers (such as lanthanide-based organic complexes) can be used to exclusively visualize and track the liquid content in a spray. 5 The phosphorescent compounds can be characterized by their lifetime, and the concentration of excited molecules can at any time directly be related to the liquid content.…”

mentioning

confidence: 99%

Decreasing luminescence lifetime of evaporating phosphorescent droplets

Voort

Dam

Sweep

et al. 2016

Applied Physics Letters

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Laser-induced phosphorescence has been used extensively to study spray dynamics. It is important to understand the influence of droplet evaporation in the interpretation of such measurements, as it increases luminescence quenching. By suspending a single evaporating n-heptane droplet in an acoustic levitator, the properties of lanthanide-complex europium-thenoyltrifluoroacetone-trioctylphosphine oxide (Eu-TTA-TOPO) phosphorescence are determined through high-speed imaging. A decrease was found in the measured phosphorescence decay coefficient (780 → 200 μs) with decreasing droplet volumes (10−9 → 10–11 m3) corresponding to increasing concentrations (10−4 → 10−2 M). This decrease continues up to the point of shell-formation at supersaturated concentrations. The diminished luminescence is shown not to be attributable to triplet-triplet annihilation, quenching between excited triplet-state molecules. Instead, the pure exponential decays found in the measurements show that a non-phosphorescent quencher, such as free TTA/TOPO, can be attributable to this decay. The concentration dependence of the phosphorescence lifetime can therefore be used as a diagnostic of evaporation in sprays.

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Droplet Velocity Measurements in Direct-Injection Diesel Sprays Under High-Pressure and High-Temperature Conditions by Laser Flow Tagging

Cited by 6 publications

References 9 publications

Lanthanide-based laser-induced phosphorescence for spray diagnostics

Lanthanide-based laser-induced phosphorescence for spray diagnostics

High-frame-rate planar laser-induced fluorescence imaging of diesel sprays using pulse burst diagnostics

Decreasing luminescence lifetime of evaporating phosphorescent droplets

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