Masters Theses

Date of Award

12-2000

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Ke Nguyen

Committee Members

Stuart Daw, Jeff Hodgson, J. R. Parsons

Abstract

The instabilities of rich premixed-flames in a low-NOx burner operated with overfire air were experimentally investigated. Specifically, the effects of equivalence ratio and gas volumetric flowrate on the instabilities of the flame were examined. The transition from stability to instability was explored and documented as burner parameters were varied. The feasibility of using both linear and nonlinear time-series analysis techniques of pressure and light measurements to predict instabilities was also studied. A frequency generator was also used to further study the effects that very small changes in equivalence ratio have on flame stability. Using overfire air the flame had a propensity to anchor at locations other than at the burner leading to periodic behavior. Analysis of the pressure and light signals demonstrated that instabilities of the flame could be observed by using both linear and nonlinear analysis techniques. It was found that linear techniques are adequate at characterizing the flame behavior due to the periodic nature of its instabilities. The equivalence ratio of the premixed gases was found to have a more pronounced effect on flame stability than the gas flowrate. It is recommended that further investigations be conducted using a better-suited pressure transducer in order to get more accurate data. The effect of varying the length of the glass tube above the burner on flame stability should also be studied.

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