Planar, stereoscopic, and holographic PIV-measurements of the in-cylinder flow of combustion engines

Abstract

The experimental analysis of the highly unsteady three-dimensional flow in internal combustion (IC) engines requires measurement techniques that are able to capture the velocity field with high temporal and spatial resolution. Among other techniques, particle-image velocimetry (PIV) is used to measure the flow in combustion engines. Depending on the specific goal of a measurement series, either standard 2D-2C PIV, stereoscopic PIV (2D/3C) or fully three-dimensional PIV methods (3D/3C) can be used. In this study, the fundamentals of particle-image velocimetry (PIV) are explained in detail, with a special focus on the application of this measurement technique to internal combustion engines. As far as the generation of the particle images is concerned, this paper describes the special characteristics of seeding particles for use in IC engines including the generation process followed by a short introduction into different light sources and light-sheet generation methods. With regard to image acquisition and processing, digital imaging devices and image evaluation methods are described. Moreover, three component two dimensional and three dimensional PIV measurement techniques, namely stereoscopic- PIV and holographic-PIV, are concisely explained. Hereafter, two-component PIV measurements in several planes, three-component-PIV measurements in a set of planes and holographic-PIV measurements in the whole volume of the intake flow of a four valve piston engine at 160° crank angle are analyzed. The results of the stereoscopic PIV measurements show the highly three-dimensional propagation of the engine flow. Furthermore, the feasibility of holographic PIV for the analysis of engine flows is confirmed.