Segmentation of diesel spray images with log-likelihood ratio test algorithm for non-Gaussian distributions

Pastor, Javier; Arrégle, Jean; García, José Manuel Sánchez; Zapata, L. Daniel

doi:10.1364/ao.46.000888

Cited by 44 publications

(40 citation statements)

References 12 publications

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“…The LRT method for the determination of the contour of the diesel spray was introduced by Desantes et al 7 and subsequently has been implemented in a purpose‐made software that offers a user‐friendly interface for the analysis of diesel spray images. The details of the algorithms used by the software for the calculation are comprehensively described in literature 7–9 and it can be easily implemented in most of the programming languages (e.g., Matlab ® , Mathworks, Natick, MA).…”

Section: Likelihood Ratio Test Methodsmentioning

confidence: 99%

Experimental Evaluation of the Best Approach for Diesel Spray Images Segmentation

Macián

Payri

García

et al. 2011

Experimental Techniques

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In this article, two of the most used methods for diesel spray macroscopic characterization are presented; the first one is the likelihood ratio test method (LRT) and the second one is the Otsu's thresholding method (OTM). Both methods are applied to different diesel sprays visualized in a high‐pressure nitrogen chamber obtaining better results with the LRT in terms of both contour determination and coherence of the results. Finally, the influence of the algorithm used for the segmentation on the macroscopic characterization measurements is observed.

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Section: Likelihood Ratio Test Methodsmentioning

confidence: 99%

Experimental Evaluation of the Best Approach for Diesel Spray Images Segmentation

Macián

Payri

García

et al. 2011

Experimental Techniques

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“…Spray penetration and spreading angle comparisons were also carried out in TR1 for SF 6 and N 2 at a relatively low ambient density (7.6 kg/m 3 ), the maximum that can be achieved in the latter case. A thorough description of this facility is given in [5]. Fig.…”

Section: Injection Systemmentioning

confidence: 99%

Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle

Payri

Bardi

et al. 2014

Experimental Thermal and Fluid Science

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In this work, three Engine Combustion Network (ECN) single-hole nozzles with the same nominal characteristics have been tested under a wide range of conditions measuring spray penetration and spreading angle. n-dodecane has been injected in nonevaporative conditions at different injection pressures ranging from 50 to 150 MPa and several levels of ambient densities from 7.6 to 22.8 kg/m 3 . Nitrogen and Sulphur Hexafluoride (SF 6 ) atmospheres have been explored and,in the first case, a temperature sweep from 300 to 550 K at constant gas density has been executed. Mie scattering has been used as the optical technique by employing a fast camera, whereas image processing has been performed through a home-built Matlab code. Differences in spray penetration related to spray orifice diameter, spreading angle and start of injection transient have been found for the three injectors. Significant differenceshave been obtained when changing the ambient gas, whereas ambient temperature hardly affects the spray characteristics up to 400 K. However, a reduction in penetration has been observed beyond this point, mainly due to the sensitivity limitation of the technique as fuel evaporation becomes important. The different behavior observed when injecting in different gases could be explained due to the incomplete momentum transfer between spray droplets and entrained gas, together with the fact that there is an important change in speed of sound for the different gases, which affects the initial stage of the injection.

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“…On the one hand, a purpose-developed code based on a One-Dimensional Loglikelihood Ratio Test (1D LRT) algorithm for segmentation [22] was used for spray penetration measurement. This code statistically determines a threshold digital level value to separate spray and background for every single schlieren image after subtracting a background image, which in the present study is obtained by ensemble-averaging a set of 30 images recorded before start of injection.…”

Section: Processing Routinesmentioning

confidence: 99%

“…Initially this code was meant to analyze the liquid length derived from Diffuse Back Illumination technique (DBI), then it was extended to Mie-scattering visualization and recently, it has been shown to be adequate for double-pass schlieren image analysis [26] with relatively short spray lengths (22.5 mm) [24]. Detailed information of this code can be found in [22], which will be referred to in the next sections as LRT code.…”

Section: Processing Routinesmentioning

confidence: 99%

“…Furthermore, there are cumbersome issues when digital analysis is applied to the resulting images that include: artificial pixel saturation, i.e. blooming phenomenon [21] or unusual histogram distributions [22], which limit or at least introduce uncertainty when systematic measurements are performed. Therefore, when considering the discrepancies among configurations from different authors (schlieren sensitivity, interfering soot luminosity and processing tools), it might seem reasonable that the corresponding reacting tip penetration trends may not fully agree [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution

Pastor¹,

Payri²,

García-Oliver³

et al. 2013

SAE Int. J. Engines

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Schlieren/shadowgraphy has been adopted in the combustion research as a standard technique for tip penetration analysis of sprays under diesel-like engine conditions. When dealing with schlieren images of reacting sprays, the combustion process and the subsequent light emission from the soot within the flame have revealed both limitations as well as considerations that deserve further investigation. Seeking for answers to such concerns, the current work reports an experimental study with this imaging technique where, besides spatial filtering at the Fourier plane, both short exposure time and chromatic filtering were performed to improve the resulting schlieren image, as well as the reliability of the subsequent tip penetration measurement. The proposed methodology has reduced uncertainties caused by artificial pixel saturation (blooming). Additionally, an algorithm to calculate Lift-off length from schlieren images has been developed and compared to the more conventional OH* imaging technique.By means of the improved setup, the analysis of transient diesel flame has been performed throughout the ignition and early combustion phases. When compared to a non-reacting vaporizing spray, the temporal evolution of the reacting case departs from the inert one at the start of combustion, when expansion in both axial (i.e. spray tip increase) and radial direction are observed. After that, the tip penetration progressively decreases on a clear transient period where the flow tries to re-organize itself in response to the induced reaction zone. Eventually, the spray undergoes an acceleration period where the reacting spray tip progresses above the nonreacting one. A parametric study has been conducted for three injection pressure levels to investigate the influence of this parameter upon transient flame evolution.

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Segmentation of diesel spray images with log-likelihood ratio test algorithm for non-Gaussian distributions

Cited by 44 publications

References 12 publications

Experimental Evaluation of the Best Approach for Diesel Spray Images Segmentation

Experimental Evaluation of the Best Approach for Diesel Spray Images Segmentation

Engine combustion network: Influence of the gas properties on the spray penetration and spreading angle

Schlieren Methodology for the Analysis of Transient Diesel Flame Evolution

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