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Numerical Investigation of Kerosene Spray Combustion with Preheated and Diluted Airflow

Moti Khalifeloo, Fatemeh | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55853 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Mardani, Amir
  7. Abstract:
  8. MILD combustion can be a promising technology to prevent global warming. In this study, for the first time, the numerical simulation of MILD spray combustion of kerosene fuel with preheated and diluted air has been conducted in the faculty's SMSTR test stand. The modeling framework is based on the Reynolds averaged Navier-Stokes turbulence approach and the standard k–ε model, the DPM discrete phase model, and the EDC combustion model, using the skeletal chemical mechanism of Jet A POSF10325 kerosene with the air and droplet being tracked in Lagrangian coordinates. The simulation is done in a steady state and by an axisymmetric method, and the effects of inlet oxygen concentration, inlet air temperature, chemical mechanisms, and the volume and time constants of the EDC combustion model, on parameters such as flame structure, flame lift-off height, temperature field and mass fraction of combustion species in the reaction zone have been studied. Based on the results in modeling with an overall kerosene/air mechanism, air preheating causes a double flame structure with a low lift-off height consisting of an external main diffusion branch and an internal weak premixed combustion area. With the simultaneous preheating and oxygen dilution effects in the mentioned chemical mechanism, an increase in the flame lift-off height, a decrease in the area of hot combustion area and a decrease in the maximum temperature have been observed, compared to the preheated flame, but the double flame structure has not changed. In repeating the simulation of both mentioned flames with the Jet A POSF10325 skeletal mechanism, in addition to the double flame structure consisting of an external diffusion branch and an internal premixed one, a significant increase in the area of the premixed zone in the flame index contour was observed, compared to the overall mechanism; a phenomenon that testifies to the importance of the chemical mechanism in these flames and was achieved as a result of increased flame lift-off height and effective mixing. Also, in the hot-diluted flame, a decrease in the mean flame temperature, creation of a more homogeneous temperature field, a drop in the maximum temperature, and a decrease in soot production was observed, compared to the preheated condition; which is an evidence of further progress towards MILD combustion. However, the overall flame area and lift-off height have not changed. Based on these results, MILD combustion has been assessed as possible
  9. Keywords:
  10. Moderate or Intense Low Axygen Dilution (MILD) ; Kerosene ; Preheated Air ; Spray Combustion ; Oxygen Dilution

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