Segmentation algorithm for diesel spray image analysis

Abstract

An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.

Hydraulic characterization of diesel engine single-hole injectors

“…9, two different gray levels can be identified: One corresponding to the background, and another corresponding to the nozzle exit orifice (brighter). Accordingly, a threshold corresponding to the gray level on the corner to the right of the background maximum has been proved successful for all images processed [17]. As a rule of thumb, that value corresponded to a pixel count of 1% of the maximum background peak.…”

“…The algorithm divides the image in two different regions: nozzle orifice and background. In order to decide which pixels correspond to which region and consequently define the boundary of the nozzle orifice, a threshold value is calculated using a similar procedure to that explained in [17]. First, an histogram is plotted using the 256 values of gray level.…”

“…First, an histogram is plotted using the 256 values of gray level. The histogram is smoothed out by applying a median filter of 5 samples [17]. The result is shown in As can be seen in Fig.…”

“…• The grayscale image is converted to binary black (binary 0) and white (binary 1) by setting a threshold in the grayscale values [17].…”

Fuel spray visualization and its impingement analysis on in-cylinder surfaces in a direct-injection spark-ignition engine

“…8 Spray development of E85 (SOI 240°BTDC at 1500 rpm engine speed and full-load) with LPDI at 3 MPa (left) and HPDI at 5 (middle) and 10 (right) MPa impingement among different test points for a given experimental setup. However, change in experimental setup may result in overall lower (or higher) values based on optical path and camera position; e.g., see Cronhjort and Wahlin (2004) for different illumination arrangements. Nonetheless, the experimental setup is not changed in this study.…”