Application of structured illumination for multiple scattering suppression in planar laser imaging of dense sprays

Berrocal, Edouard; Kristensson, Elias; Richter, Mattias; Linne, Mark; Aldén, Marcus

doi:10.1364/oe.16.017870

Cited by 156 publications

(100 citation statements)

References 17 publications

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“…The structured illumination technique referred to as SLIPI (Structured Illumination Planar Imaging) was developed for sprays by Berrocal et al [7] and Kristenson et al [8] and commercially implemented by LaVision [9]. The experimental setup including the SLIPI optics for structured light generation is shown in Fig.…”

Section: Slipimentioning

confidence: 99%

Laser diagnostics for urea-water solution spray characterization

Kapusta

Teodorczyk

2017

MATEC Web Conf.

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Abstract. In this study, we summarize the laser techniques used for urea-water solution (UWS) spray characterization at the Institute of Heat Engineering (ITC), Faculty of Power and Aeronautical Engineering at Warsaw University of Technology. In presented studies several techniques for both, global and local spray characterization were used. Shadowgraphy-based long distance microscopy was used to visualize individual droplets and primary breakup. High speed imaging of Mie scattering (scattering on the gas-liquid interface) signal was used for global spray characterization. Combination of LIF (Laser Induced Fluorescence) and Mie scattering allowed to determine qualitative droplet size distribution across the whole spray cloud. The structured illumination technique used to modulate laser light sheet allowed to minimize the effects of multiple scattering in detection of Mie signal, what indicated huge potential of this technique in characterization of UWS sprays. The results presented here prove the importance of laser diagnostics in SCR systems development.

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Section: Slipimentioning

confidence: 99%

Laser diagnostics for urea-water solution spray characterization

Kapusta

Teodorczyk

2017

MATEC Web Conf.

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“…Within optically dense media, the majority of photons are scattered multiple times, and therefore, the single scattering approximation is no longer valid. The SLIPI technique, standing for structured laser illumination planar imaging (Berrocal et al 2008), that combines structured illumination (Neil et al 1997) and laser sheet imaging, has proven to be a valuable approach for suppressing the contribution from multiple light scattering.…”

Section: Introductionmentioning

confidence: 99%

“…This is achieved by shifting the line pattern one-third of the spatial period and recording a set of three modulated images (sub-images). From this data set, a final demodulated SLIPI image can be extracted, wherein the contribution from the multiply scattered light has been reduced (Berrocal et al 2008). However, due to the need for recording three sub-images, SLIPI has been mostly used for temporally averaged measurements of spray quantities such as droplet SMD in sprays (Mishra et al 2014), 3D-mapping of the droplet extinction coefficient (Wellander et al 2011), spray temperature using two-color LIF , as well as flame temperature using Rayleigh thermometry (Kempema and Long 2014).…”

Section: Introductionmentioning

confidence: 99%

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

et al. 2017

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images with an intensity profile close to the corresponding single scattering case. Experimentally, this suppression renders both an improvement in image contrast and the removal of undesired stray light components that could be interpreted as signal. However, while 2p-SLIPI preserves most of the initial spatial resolution, 1p-SLIPI results in a loss of spatial resolution, where high-frequency image information is not visible anymore. Thus, there is a tradeoff between preserving the most detailed information of the spray structure-with 2p-SLIPI-and being able to record an SLIPI image from a single modulated image only-with 1p-SLIPI. The comparison and technical overview of these two methods presented in this paper can facilitate in selecting which approach is the most suitable for a given application for spray visualization.

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“…Note, however, that a single experimental system that can satisfy all these needs does not currently exist (Heindel 2011). Despite the recent advances in laser diagnostics, such as ballistic imaging or structured illumination to mitigate the multiple scattering effects (Berrocal et al 2008;Linne et al 2006), their ability to measure fluid density is still limited (Leick et al 2011). Moreover, flows with significant refractive index gradients, such as liquid diesel and vapour, exhibit beam-steering effects that interfere with optical diagnostics by creating uncertainty in the location of the volume under observation (Heindel 2011).…”

Section: Introductionmentioning

confidence: 99%

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

et al. 2016

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efficiency of such engines. Among others, the fuel injection equipment (FIE) is a key component for improving the efficiency of environmentally friendly engines. Recent advances dictate the use of extra high injection pressures, of the order of 3000 bar and tiny flow passages (injection holes) of the order of 100-250 μm in diameter, for improved fuel atomisation and combustion efficiency. Under these circumstances, cavitation has been found to develop inside fuel injection nozzles at the early studies of Badock et al. (1999), Bergwerk (1959), Chaves et al. (1995) and Nurick (1976), followed by Arcoumanis et al. (2000), Blessing et al. (2003), Mitroglou et al. (2014) and Roth et al. (2002) in more realistic real-size nozzle geometries offering optical access; equally helpful studies performed in transparent enlarged nozzle replicas [selectively (Andriotis et al. 2008;Arcoumanis et al. 2000;Miranda et al. 2003; Mitroglou and Gavaises 2013;Powell et al. 2000)] also indicate that cavitation plays an increasingly significant role in the nozzle's internal flow structure and development. Cavitation inside an injection hole is believed to enhance spray atomisation, either directly through the implosion of cavitation bubbles or indirectly because it increases turbulence in the nozzle flow (Badock et al. 1999;Walther 2002); unfortunately, under certain circumstances induces erosion (Dular and Petkovšek 2015;Koukouvinis et al. 2016) that may lead to catastrophic failures. Moreover, cavitation inside the injection holes promotes shot-toshot spray instabilities (Mitroglou et al. 2011(Mitroglou et al. , 2012Suh and Lee 2008), which, in turn, are responsible for poor combustion efficiency and increased emissions (Hayashi et al. 2013). Two distinct macroscopic forms of cavitation have been identified, which are referred to as geometryinduced and vortex or 'string' cavitation. The former can be, partially or totally, suppressed by appropriate design of the inlet hole curvature and non-cylindrical injection hole Abstract The flow inside a purpose built enlarged singleorifice nozzle replica is quantified using time-averaged X-ray micro-computed tomography (micro-CT) and highspeed shadowgraphy. Results have been obtained at Reynolds and cavitation numbers similar to those of real-size injectors. Good agreement for the cavitation extent inside the orifice is found between the micro-CT and the corresponding temporal mean 2D cavitation image, as captured by the high-speed camera. However, the internal 3D structure of the developing cavitation cloud reveals a hollow vapour cloud ring formed at the hole entrance and extending only at the lower part of the hole due to the asymmetric flow entry. Moreover, the cavitation volume fraction exhibits a significant gradient along the orifice volume. The cavitation number and the needle valve lift seem to be the most influential operating parameters, while the Reynolds number seems to have only small effect for the range of values tested. Overall, the study demonstrates that use of micro-CT can ...

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Application of structured illumination for multiple scattering suppression in planar laser imaging of dense sprays

Cited by 156 publications

References 17 publications

Laser diagnostics for urea-water solution spray characterization

Laser diagnostics for urea-water solution spray characterization

Comparison between two-phase and one-phase SLIPI for instantaneous imaging of transient sprays

Application of X-ray micro-computed tomography on high-speed cavitating diesel fuel flows

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