Date of Award

Summer 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Shizhi Qian

Committee Member

Kareem Ahmed

Committee Member

Xiaoyu Zhang

Call Number for Print

Special Collections; LD4331.E56 F567 2015

Abstract

With increasing interest to engineer more efficient combustion engines, the use of laser induced ignition demonstrates to be a compelling alternative to the conventional electric spark plug. The benefits greatly outweigh those found in a conventional electric spark motor whereas research shows improvements in reduced energy consumption and harmful emissions. In addition, the ability to divert the laser beam and its reliability are advantages. Laser-based ignition is capable of generating a plasma for combustion in versatile surroundings where ignition is desired. Laser induced ignition of methane-air was investigated under diverse flow and mixture conditions. To perform this experiment three air/fuel (AF) ratios were selected a rich (AF= l0), stoichiometric (AF= l7.2) and lean (AF=22). Each of the AF mixtures were observed at velocity flows of 1.0, 1.25 and 1.5 mis. Flame kernel evolution was examined by internal and external dynamic characteristics. Advanced laser diagnostics and optical imaging techniques are utilized to capture the flame kernel dynamics using Schlieren and Particle Imagery Velocimetry (PIV) systems. The Schlieren system collected images of the flame kernel mechanism, revealing the flame structure, propagation, and evolution. PIV data images display the internal and external fluid flame motion and transfer of energy across the flame. The techniques revealed that as the AF mixture increases the flame kernel shows decrease in turbulent kinetic energy velocity fluctuations and surface deformations. The lean 1 mis run is ideal

because the laminar flame speed is approximately .45 mis, so the closer it is to that value the more ideal it is for flame propagation. The flame kernel propagation speed was the quickest and the flame showed minimal surface defects. As the velocity increases for the lean case, the fluctuations and structure deformations return. It is also evident that the flame kernel energy decreases as time progresses. The knowledge gained from this experiment provides the ability to identify the effects and interactions that are expected on the flame surface and internal to the kernel.

Rights

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DOI

10.25777/sjr5-kv57

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