Plenoptic single-shot 3D imaging of in-cylinder fuel spray geometry

Abstract

Progress in understanding turbulent combustion requires access to information that is derived from instantaneous 3D images showing the contours of the flame front, the flow field, and other quantities. The experimental effort to acquire such information is typically extraordinarily high and therefore not as widely used as needed. The introduction of commercially available plenoptic cameras now provides a means to simplify some of these measurements as is described in this study. A single 29 mega-pixel plenoptic camera was used to record the Mie scattering signals from volumetrically illuminated fuel sprays. Instantaneous 3D images were acquired from within the cylinder of an optically accessible engine for three automotive fuel injectors of differing nominal spray angles. Current reconstruction algorithms do not yet take translucent imaging conditions into account and therefore a quantitative analysis of the full 3D structure of the sprays was not possible. However, the plenoptic system did prove capable of accurately reconstructing bulk spray features such as spray angles. The 3D spray images were validated with data from a conventional 2D imaging system. This study demonstrates the feasibility of using a single plenoptic camera to view spray geometry in 3D, even from within the challenging in-cylinder engine environment.