Masters Theses

Date of Award

12-2006

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Gary Flandro

Committee Members

John Steinhoff, Trevor Moeller

Abstract

The thesis outlines an experiment done in the oscillation of a closed tube near to its fundamental frequency. A tube with a length of ten feet was oscillated via a piston driven by a DC motor. The pressure waveform and mean pressure was recorded at the end of the tube and the mean pressure was measured at the middle of the tube. When the tube was excited near to its 1st mode non-linear features such as shock-like waveforms, cascading of energy to higher modes and mean pressure shift were recorded.

These Results are only possible to predict by using a non-linear analytical approach. Work by Chester5 successfully predicts the shock-like waveform phenomenon; however, it fails to predict the mean pressure shifts. Flandro6,16-17 successfully correlates the shock- like waveforms and mean pressure shift in his non-linear combustion instability research.

Predicting these phenomena has critical importance to the field of combustion instability and rocket combustion chamber design. Solid and liquid rocket engines often have large amplitude pressure oscillations marked by shock-like features and mean pressure shifts. These both act to cause large mechanical vibrations, thrust variations, internal damage and catastrophic failure of the engine. Understanding these phenomena in an analytical way is important if rocket engines are to be designed in a reliable and inexpensive way. The use of the highlighted experiment in this thesis will serve to elucidate which analytical approach is the most appropriate.

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