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Experimental Investigation of Air Preheating and Diluting on Flame in the Sharif Double-Swirl Gas Turbine Model Combustor (SGTMC)

Nourifard, Mohammad | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58100 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mardani, Amir
  7. Abstract:
  8. In this study, the effects of increasing the temperature of the air or oxidizer used in the combustion process were investigated. Additionally, the effects of oxidizer dilution through nitrogen gas injection into the inlet air of the combustion chamber were examined. The research was conducted experimentally on the Sharif model gas turbine combustion chamber. Moreover, LPG gaseous fuel, which is a mixture of propane and butane gases, was utilized. Data acquisition techniques such as imaging, bandpass-filtered imaging, spectroscopy, and thermometry were employed throughout the tests. The results are reported in four sections: base flame characteristics, preheating effects, dilution effects, and the combined effects of preheating and dilution. The findings indicate that flame luminosity increases with preheating. An increase of 200°C in the oxidizer temperature led to an 80% rise in CH* chemiluminescence, while increasing the oxidizer temperature by 300°C extended the lean stability limit from 0.32 to 0.27. Furthermore, the combination of preheating and dilution increased the flame area and expanded the concentrated combustion zone within the tested model combustion chamber. Under maximum preheating and dilution conditions—where the oxidizer mixture contained up to 640 K temperature and 14.3% oxygen—the combustion zone occupied up to 90% of the chamber volume. In this state, the flame luminosity decreased by 90% compared to the conventional flame, and both temporal and spatial fluctuations in luminosity were significantly reduced. The results demonstrate that under the highest preheating and dilution conditions, the observed combustion regime closely resembles mild combustion conditions. To further enhance research in the field of mild combustion, recommendations include increasing the combustion chamber volume, relatively reducing the strength of the recirculation zone induced by swirlers, and improving structural considerations before the combustion zone
  9. Keywords:
  10. Preheating ; Dilution ; Gas Turbine Model Combuster (GTMC) ; Moderate or Intense Low Axygen Dilution (MILD)

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