Experimental Measurement Of Flame Response To Acoustic Oscillations
MetadataShow full item record
Acoustic instabilities in a combustion chamber arise due to the coupling of acoustic pressure with in-phase heat-release, and are characterized by large amplitude oscillations of one or more natural modes of combustor. Even though an array of studies, both theoretical and experimental, has been conducted by a number of authors in this field to extract the flame response, most of these are based on kinematic flame models. In this dissertation, an experimental study of a subsonic flame's intrinsic response to acoustic pressure perturbations is performed for the case of a tube closed at one end and the other end opened to the atmospheric conditions. Pressure fluctuations inside the tube are measured for hot and cold side flows, and their varying trend is explained. The frequencies obtained from Fourier transform analysis exhibit a strong dependence with the distance between the stabilized flame position and open end of the tube. For different values of flame position (xf ), the values of growth constant 's' are calculated from the pressure versus time data readings procured from acoustic pressure transducer and dominant frequencies are analyzed from windowed FFT of the same. The expression for obtaining response function from the measured pressure fluctuations has been derived from the 1-D linearized conservation equations. The undamped response function plot is obtained by adding the decay rates at different frequencies inside the tube to the corresponding growth rates. Finally, the effect of blockage of pre-mixed flow on the growth rates inside the tube and consequently, the flame response values, is studied by repeating the experiment with different types of flame holders. A large number of theoretical flame-response models have been developed in modern literature, and some of these models are compared with the experimentally obtained response. Suggestions are also cited in this study so as to account for the observed deviations in trends. This includes a revisit of the intrinsic flame model by incorporating the effect of flame-area perturbations, with the aid of analyzed steady flame images.
Showing items related by title, author, creator and subject.
Resonances and beats in nonlinear structural acoustic waveguides Bharat, BiswajitIn this thesis that is entirely analytical in nature, nonlinear wave propagation in various structural-acoustic waveguide geometries is studied. The waveguides considered include a circular cylindrical waveguide with a ...
Call Diversity, Spatio-Temporal Patterning And Masking Interference In An Assemblage Of Acoustically Communicating Ensiferan Species Of A Tropical Evergreen Forest In Southern India Diwakar, Swati (2011-02-21)The present study provides the first description of the calls of a multi-species ensiferan assemblage in a tropical evergreen forest of the Indian subcontinent. I have identified and described the calls of twenty ensiferan ...
Analysis Of Multiply-Connected Acoustic Filters with Application To Design Of Combination Mufflers And Underwater Noise Control Linings Panigrahi, Satyanarayan (2008-10-01)This thesis endeavors towards developing various concepts employed in analysis and design of acoustic ﬁlters for varied applications ranging from combination mufflers for automobiles to complex networks of gas carrying ...