Date of Award
Doctor of Philosophy
Mechanical and Aerospace Engineering
Dr. Claudia Fajardo-Hansford
Dr. Parviz Merati
Dr. Tianshu Liu
Dr. Javier Montefort
Internal combustion engines, turbulence, anisotroov, tensor invariant analysis
Turbulence significantly impacts the operation of energy conversion devices. In internal combustion (IC) engines, mixing, heat transfer, and combustion are all strongly dependent on the turbulence inside the cylinder. Consequently, knowledge of the state of turbulence is critical for improving our understanding and modeling of engine processes.
Turbulence states may be determined through analysis of the Reynolds stress tensor, which can in turn be experimentally quantified using velocity data. In this research, stereoscopic particle image velocimetry (stereo-PIV) experiments were conducted in a single-cylinder, motored engine with optical access to measure the two-dimensional, three-component (2D-3C) velocity fields throughout the compression stroke. Invariants of the Reynolds stress anisotropy tensor were calculated and visualized, using the Lumley triangle, at various piston positions.
Results showed the turbulence to be mostly anisotropic throughout the compression stroke, in contrast to commonly employed modeling assumptions. Despite some spatial dependence of turbulent states, the turbulence was preferentially two-dimensional and axisymmetric at the beginning of the compression stroke, showing a tendency toward isotropy as the piston approached top-dead-center. Findings provide new insights into turbulence in dynamic, bounded flows to assist with the development of physics-based, quantitative models.
MacDonald, James R., "Turbulence Investigations in the Core-Flow of an Internal Combustion Engine" (2020). Dissertations. 3569.