Efficacy of a nonlinear acoustic model for combustion stability prediction

Ajay R Madhav, Purdue University

Abstract

A nonlinear, acoustic model, which is used to predict combustion stability, is applied to eight modes. By a unique experimental setup, inputs required for this model such as linear growth rates were able to be obtained from limit cycle amplitude data. The model's results were compared to experimental data through a variety of analysis techniques. Two experimental cases (length of oxidizer posts being 139.7 mm (5.5 in.) for the first and 165.1 mm (6.5 in.) for the second) were compared to three model case variations. The model variations were based on varying growth rates for the 3rd through 8th modes. The analysis techniques included Power Spectral Densities (PSDs) comparisons, modal pressure trace comparisons, growth rate comparisons, and energy analysis comparisons. Each analysis confirmed that one particular configuration of the model's inputs shared many similarities to both experimental cases. These similarities included similar modal frequencies, steep-fronted waveforms, and modal energy distributions. These results indicate that the eight-mode nonlinear model has the capability to predict combustion stability, but further work is needed to refine the model and its inputs.

Degree

M.S.A.A.

Advisors

Anderson, Purdue University.

Subject Area

Aerospace engineering|Acoustics

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