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Effects of Swirl Number and Central Rod on Flow in Lean Premixed Swirl Combustor

Yellugari, Kranthi
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872979440851

Abstract Details

2019, MS, University of Cincinnati, Engineering and Applied Science: Aerospace Engineering.
Gas turbine combustors are used to extract chemical energy from the combustion of fuel in presence of an oxidizer to power turbines. Environmental concerns provide motivation to develop more efficient and less polluting gas turbine engines. To achieve good emission performance, lean burn combustors with low pollutant emissions have been developed. These combustors operate at fuel lean conditions and they can be classified into lean premixed and pre-vaporized (LPP) combustor, where the fuel and oxidizer are premixed and pre-vaporized to form a homogeneous mixture in a dedicated region, premixer, just before the fuel-oxidizer mixture enters the combustion chamber, and lean direct injection (LDI) combustor, where the fuel is directly injected into the flame zone without any premixing with oxidizer. The premixing and pre-vaporizing reduce the residence time, the amount of time the gases are in the combustion chamber. The reduction in residence time reduces the NOx emissions, as the high NOx emissions are produced with a long residence time in the combustion chamber. The flow behavior of non-reacting and reacting flow in a lean premixed swirl combustor, adapted from KAUST experimental rig, has been studied using RANS in the commercial software, Ansys - Fluent. Turbulence is modeled using the two equation realizable k-epsilon model and the turbulence - chemistry interaction is modeled by a flamelet generated manifold (FGM) technique with methane-air mixture at an equivalence ratio of 0.67. GRI 3.0 mechanism was used for modeling chemistry, which had 325 chemical equations and 53 species to solve. A central toroidal recirculation zone (CTRZ) was observed from a swirl number, S = 0.52 in the case with a central rod, and from S = 0.54 in the case without a central rod and it helped to stabilize the flame. At low swirl numbers, the central rod, which was in the injection tube, helped the flow and flame to stabilize on top of it. In the absence of this central rod, the flame is lifted off and stabilized at a distance from the burner exit. Also, the flame length was shortened at high swirl numbers. As the swirl number was increased, the CTRZ started to move upstream. This phenomenon with flame flashback was observed from S = 0.7. A very high turbulence was observed in the inner shear layer. At high swirl numbers, as the CTRZ moved upstream, the turbulent kinetic energy was very high near the burner exit and the in shear layers. Central rod is best suited at low swirl numbers. Whereas, at high swirl numbers (S>0.6), the need for the central rod is minimized. NOx emissions are higher in the regions of high temperature. Along the downstream direction, the NOx concentration is increased. But, it starts to decrease near the exit of the combustion chamber due to the decrease in the temperature. The NOx concentrations decrease with increasing swirl numbers. The case without the central rod produced slightly lower NOx, when compared to the case with the central rod.
Ephraim Gutmark, Ph.D. (Committee Chair)
Prashant Khare, Ph.D. (Committee Member)
Rodrigo Villalva Gomez, Ph.D. (Committee Member)
108 p.
Aerospace Materials
Swirl Number; Lean Premixed Combustion; NOx Emissions; Central Rod; Reacting Flow; Non-reacting Flow

Recommended Citations

Citations

  • Yellugari, K. (2019). Effects of Swirl Number and Central Rod on Flow in Lean Premixed Swirl Combustor [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872979440851

    APA Style (7th edition)

  • Yellugari, Kranthi. Effects of Swirl Number and Central Rod on Flow in Lean Premixed Swirl Combustor. 2019. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872979440851.

    MLA Style (8th edition)

  • Yellugari, Kranthi. "Effects of Swirl Number and Central Rod on Flow in Lean Premixed Swirl Combustor." Master's thesis, University of Cincinnati, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872979440851

    Chicago Manual of Style (17th edition)

ucin1563872979440851
490
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This open access ETD is published by University of Cincinnati and OhioLINK.