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Experimental Study of Fuel Concentration Fluctuations on Diffusion Flame Structure

Fathieh, Farhad | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40284 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Farshchi, Mohamad
  7. Abstract:
  8. In the present study, the axisymmetric liquid gas/air diffusion flame in the presence of fuel concentration oscillations and velocity perturbations has been investigated experimentally. Several industrial combustions take a place by diffusion mechanism which necessitate scientists to make far better understanding of diffusion flames. In order to study diffusion flames, the instrument with two separated lines of fuel and air has been developed. Nitrogen is used for fuel dilution oscillatory with pulse of 1, 2, and 4 Hz frequencies. The pulse duration effects on flame structure are also studied. The flame shape has been captured by high speed camera and the results are processed by image processing methods. The length of flame obtained experimentally is in good accordance with theoretical relations. Different flame structures have been observed and phenomena like flame flickering and clip off have been detected. It is seen that with the increase in the flow of nitrogen, there is an insignificant decrease in flickering frequency. In addition, with the rise in the excitation frequency and approaching flickering frequency, the flame response to fluctuations weakened; in contrast, the flickering oscillations increase. Furthermore, it is understood that the mail reason of clip off is vortex generation and vortex shedding which is in contrast with the available theory indicating that the high and low concentration region in the flame are the bases of clip off. Moreover, it is found that the pulse duration does not have significant effect on the time at which clip off formed
  9. Keywords:
  10. Flame Structure ; Excitation Frequency ; Diffusion Flame ; Flicker ; Flame Clip-Off

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