Characterization of Diesel Spray Images Using a Shape Processing Methodology

Abstract

In Diesel engines, a key element in achieving a clean and efficient combustion process is a proper fuel-air mixing, which is a consequence of the fuel spray development and fuel-air interaction inside the engine combustion chamber. The spray structure and behavior are classically described by the length (penetration) and width (angle) of the spray plume but these parameters do not give any clue on the geometrical injection center and on the spray symmetry. The purpose of this paper is to find out original tools to characterize the Diesel spray: the virtual spray origin is the geometrical injection center, which may (or may not) coincide with the injector axis. Another interesting point is the description of the Diesel spray in terms of symmetry: the spray plume internal and external symmetry characterize the spray and the injector performance. Our approach is first to find out the virtual spray origin: after the image segmentation, the spray is coded with the Freeman code and with an original shape coding from which the moments are derived. The symmetry axes are then computed and the spray plumes are discarded (or not) for the virtual spray origin computation, which is derived from a Voronoi diagram. The last step is the internal and external spray plume symmetry characterization thanks to correlation and mathematical distances.

Characterization of Diesel Spray Images Using the Logarithmic Image Processing Framework

“…The virtual spray origin (VSO) calculation was first presented in Petit et al (2005). A raw virtual spray origin is calculated (RVSO), then an accurate virtual spray origin is deduced from a Voronoi diagram (AVSO).…”

“…A single spray plume symmetry axis can be calculated from its boundary as presented in Petit et al (2005). Nevertheless, the quantified image of the spray describes the physical process of the flow evolution.…”

“…The advantages of this method over the one presented in Petit et al (2005) are that images taken Image Anal Stereol 2007;26:145-155 with different setups (monochromatic, polychromatic light) are be compared, the axis presenting the spray development is calculated and finally the high grey level pixels have more influence on the results and the low ones. It means that using our optical setup, this distance determines the liquid continuous core internal symmetry.…”

“…Delacourt et al (2005) study the injection pressure influence on spray macroscopic parameters as penetration, angle, area and volume. Petit et al (2005) present a methodology to calculate the virtual spray origin (virtual injection center), the single plume shape inertia axes, and tools to study the single plumes internal and external symmetry.…”