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Effects of the Fuel-Air Mixing on Combustion Instabilities and NOx Emissions in Lean Premixed Combustion

Estefanos, Wessam
http://orcid.org/0000-0002-1765-7346
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731723

Abstract Details

2016, PhD, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
An experimental study was conducted to investigate the effects of the fuel-air mixing on combustion instabilities and NOx emissions in lean premixed combustion. High speed PIV measurements in water were conducted to capture the mean and dynamic behavior of the cold flow generated by a 3X model of the tested premixer. High speed PLIF in water measurements were conducted to quantify the mean and unsteady fuel-air mixing at different momentum flux ratios. Atmospheric combustion tests using the original premixer, were conducted using natural gas and propane at the same momentum flux ratios of the PLIF mixing tests. An emissions analyzer was used to measure the emissions from combustion tests. Dynamic pressure transducers were used to measure the amplitude and the frequency of the dynamic pressure oscillations associated with the combustion instabilities. CHEMKIN-PRO was used to model the atmospheric combustion and predict NOx emissions at different conditions. Results showed that unsteady fuel-air mixing was concentrated at the center and near the outer edges of the premixer. These regions were characterized by high fuel concentration gradients. With the increase in the momentum flux ratio, the concentration gradient and the level of unsteady mixing increased, indicating that the fuel-air spatial unmixedness was the source of the unsteady mixing. It was found that local flow turbulence tended to decrease the concentration gradient through enhancing the fuel-air mixing, which resulted in decreasing the level of unsteady mixing. NOx emissions from atmospheric combustion increased with the increase in the momentum flux ratio due to the increase in the flame temperature and the fuel-air spatial and temporal unmixedness. The intensity of the combustion dynamics increased with the increase in the level of unsteady mixing. Axial injection of the fuel into the regions of strong unsteady mixing eliminated the combustion dynamics through damping the unsteady mixing. Results of CHEMKIN-PRO agreed very well with the experimental results and showed that the spatial and temporal unmixedness have a significant effect on NOx emissions for very lean combustion (F = 0.4). With the increase in the equivalence ratio, their relative contribution decreased.
San-Mou Jeng, Ph.D. (Committee Chair)
Anne Geraldine Mouis, Ph.D. (Committee Member)
Awatef Hamed, Ph.D. (Committee Member)
Samir Tambe, Ph.D. (Committee Member)
205 p.
Engineering
Lean premixed combustion; Fuel-air mixing; NOx emissions; Combustion instabilities; Unsteady flow behavior

Recommended Citations

Citations

  • Estefanos, W. (2016). Effects of the Fuel-Air Mixing on Combustion Instabilities and NOx Emissions in Lean Premixed Combustion [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731723

    APA Style (7th edition)

  • Estefanos, Wessam. Effects of the Fuel-Air Mixing on Combustion Instabilities and NOx Emissions in Lean Premixed Combustion. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731723.

    MLA Style (8th edition)

  • Estefanos, Wessam. "Effects of the Fuel-Air Mixing on Combustion Instabilities and NOx Emissions in Lean Premixed Combustion." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460731723

    Chicago Manual of Style (17th edition)

ucin1460731723
842
© 2016, some rights reserved.Creative Commons License Effects of the Fuel-Air Mixing on Combustion Instabilities and NOx Emissions in Lean Premixed Combustion by Wessam Estefanos is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.
Release 3.2.12