PhD Proposal by Suo Yang

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  • Date/Time:
    • Friday December 2, 2016
      2:00 pm - 4:00 pm
  • Location: Guggenheim Building Room 442
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Summary Sentence: EFFECTS OF DETAILED FINITE RATE CHEMISTRY IN TURBULENT COMBUSTION

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Ph.D. Thesis Proposal by

Suo Yang

(Advisers: Prof. Wenting Sun and Prof. Vigor Yang)

EFFECTS OF DETAILED FINITE RATE CHEMISTRY IN TURBULENT COMBUSTION

02:00 pm Friday, 2nd December 2016

Guggenheim Building Room 442

 

ABSTRACT

Direct numerical simulation (DNS) and large eddy simulation (LES) are critical to analyze and improve design and development of advanced energy conversion and propulsion systems, for ignition, combustion instability, lean blow-out, and emissions. However, stiff finite-rate chemistry and mixture-averaged transport are computationally intensive, especially in 3D turbulent combustion simulations. For this reason, except for those consuming excessive computational resources and time, most past DNS/LES studies of turbulent combustion have used either a flamelet model with detailed chemistry (~50 species or more) or a simplified/reduced finite-rate chemical model with non-stiff reactions (~10 species). Both approaches, however, are of limited accuracy and reduce the overall quality of prediction. Therefore, it is required to accelerate the computation of chemical kinetics and transport properties to enable computationally efficient and accurate simulations employing detailed finite-rate chemical kinetic models.

In addition, the sensitivity of simulation results to different chemical kinetic models is unclear, particularly on the prediction of local extinction and re-ignition events in turbulent combustion environments. Knowledge of local extinction and re-ignition events are vital, as they may lead to increased emissions, combustion instability, or flame blow-out. Therefore, accurate prediction of these events is an important task for high-fidelity simulations, which requires quantitatively capturing the wide range of time and length scales involved and the complex interactions between turbulent mixing, molecular diffusion, and chemical reactions. Most existing chemical models have similar predictions of ignition and extinction in 0D/1D finite-rate simulations of laminar combustion processes. Is it appropriate to extend this observation to a 3D turbulent combustion environment?

In this work, a new regime-independent simulation framework for turbulent combustion is developed by incorporating techniques of correlated dynamic adaptive chemistry (CoDAC), correlated transport, and an efficient point-implicit ODE solver to allow computationally efficient DNS/LES with detailed finite-rate chemistry. In particular, CoDAC generates locally-optimized reduced kinetics for each spatial location and time step, and only the reaction rates of active species are calculated. Using this tool, 2 chemical kinetic models are compared by performing 3D finite-rate kinetics based simulations of a temporally evolving turbulent non-premixed syngas flame. Significant quantitative deviations indicate high sensitivity of local extinction and re-ignition predictions to different chemical kinetic models. This sensitivity is significantly magnified by the effects of 3D and turbulence relative to a 1D laminar simulation, with the deviations in species concentrations, temperature, and reaction rates forming a positive feedback loop. At local extinction, the major differences are the peak values and their volume, which is dominated by the 3D effects; whereas at re-ignition, the differences are mostly observed in spatial distribution of the reacting flow field, which is primarily dominated by the complex turbulence-chemistry interaction. In the next stage, the new framework will be extended to LES in a preconditioning scheme to cover a wide range of Mach numbers for practical applications.

 

Committee:

Dr. Wenting Sun, ME

Dr. Vigor Yang, AE

 

Dr. Suresh Menon, AE

 

 

 

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  • Created By: Tatianna Richardson
  • Workflow Status: Published
  • Created On: Oct 21, 2016 - 9:36am
  • Last Updated: Oct 21, 2016 - 9:36am