Date of Award

6-2020

Degree Name

Doctor of Philosophy

Department

Mechanical and Aerospace Engineering

First Advisor

Dr. Claudia Fajardo-Hansford

Second Advisor

Dr. Parviz Merati

Third Advisor

Dr. Tianshu Liu

Fourth Advisor

Dr. Javier Montefort

Keywords

Internal combustion engines, turbulence, anisotroov, tensor invariant analysis

Abstract

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.

Comments

Fifth Advisor: Callum Gray, Ph.D.

Access Setting

Dissertation-Campus Only

Restricted to Campus until

6-30-2022

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