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AE Combustion Lab

   

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Projects:

 
   

 

Ozone Assisted Combustion

If ozone is doped into air and ethylene is used as fuel in a diffusion jet flame, ozonolysis reaction starts in the mixing layer. The heat lease and radical production from ozonolysis reaction will cause autoignition of the diffusion jet flame. For lifted jet flame, if ozone is added, autoignition kernels will form in flame front and cause flame attachment. From the below images from high speed camera, it can be clearly shown the flame propagation is controlled by autoignition kernel which is separated from flame front.

The time differences between frame (a) and the rest frames are (b) 0.2 ms, (c) 0.4 ms, (d) 0.6 ms, (e) 0.8 ms, (f) 1.2 ms, (g) 2.0 ms, (h) 4.0 ms, (i) 6.0 ms, and (j) 10.0 ms.

 

Autoignition and Combustion Stability of High Pressure Supercritical CO2 Oxy-Combustion

The successful development of directly heated supercritical carbon dioxide gas turbine power systems utilizing pressurized oxy-combustion, that have high efficiency while capturing nearly 100% of the CO2 produced, is critically dependent on the design of combustors. Two key issues that need to be considered in the design of combustors are basic burning properties of the mixture (e.g., autoignition times), as well as the high pressure system dynamics (e.g., combustion stability). The objective of this project is to experimentally investigate (for the first time) the autoignition delays at practical conditions for SCO2 oxy-combustion (150 to 330 atm). An optimized chemical mechanism will then be developed for the design of combustors for SCO2 oxy-combustion. Large Eddy Simulation (LES) will utilize the mechanism developed in this proposed program to simulate autoignition and flame stability in a dump combustor under these operating conditions.

Project presentation: pdf

 

 

Combustion Instability Control Using Plasma

Laser Absorption Spectroscopy for Combustion Chemistry

Dynamic Adaptive Kinetics for Turbulent Combustion

In this project, a new regime-independent framework for 3D DNS of turbulent combustion with detailed kinetics is developed by incorporating on-the-fly adaptive kinetics (OAK), correlated transport (CoTran) techniques, and an efficient point-implicit ODE solver (ODEPIM) into a conventional DNS platform. All three methods are modified and optimized to adapt to 3D turbulent combustion and parallel high performance computing (HPC). A canonical turbulent premixed flame configuration corresponding to the thin reaction-zone regime is considered, where an initially planar premixed flame front interacts with a decaying isotropic turbulence. The computational domain consists of a cube with length 0.015 m. With the new numerical frame work, calculation of chemistry can be accelerated 46 times, calculation of transport can be accelerated 72 times, and overall acceleration of calculation is 20 times.

Temperature (upper) and vorticity (lower) at the center plane (z = 0.75 cm) using conventional DNS (left) and proposed framework (right)

Mass fraction (upper) and reaction rate (lower) of fuel at the center plane (z = 0.75 cm) from conventional DNS (left) and proposed framework (right)

spatial distribution of the number of active species at the center plane (z = 0.75 cm)

Average CPU time distribution per time step (sec) for four methods (from left to right): DVODE, ODEPIM, ODEPIM+OAK, and ODEPIM+OAK+CoTran

 

 

 

Numerical Modeling of Plasma Assisted Combustion System

 

The 1D numerical model contains the Poisson equation for electric potential, electron energy equation, and species continuity equations for all charged and neutral species given by Eqs. (1)-(3) respectively, where electron energy density   is given by the product of electron density  and electron energy. The transport of energy and species is calculated by the drift (mobility)-diffusion model. Reduced electric field (E/N) and energy input can then be calculated rather than pre-specified as in 0D model.

The gas flow is modeled by solving mass, momentum and total energy conservation equations simultaneously, as given by Eqs. (4)-(6) respectively. Unlike equilibrium plasma, which transfers electrical energy only into sensible enthalpy, Joule heating in non-equilibrium plasma transfers electrical energy into the total energy of the gas mixture. This means that not all energy from Joule heating contributes to gas temperature rise. Heat release from chemical reactions is implicitly included in the unsteady term of total energy with the form of chemical energy converting to sensible enthalpy.

The simulations were conducted at pressure p=60 Torr, and initial temperature T=300 K, to match the experiments. The initial mixture composition was C2H4:Ar:O2 = 0.062:0.75:0.18 in mole-fractions.

Zero potential is set at the left boundary, and gap voltage  at the right boundary.  is obtained from the applied voltage  by the equation (7), where dielectric constant  is 4.8 for quartz, and 3.2 for silicone rubber.

Zero flux wall boundary condition is used for neutral species. The wall boundary fluxes for electrons, positive ions, negative ions and electron energy are given by Eq. (8)-(11) respectively.

where secondary electron emission coefficient  is taken to be 0.05. Temperature of secondary electrons ejected from the electrode surface  is assumed to be 1 eV. =1 if , and =0 otherwise.

A zero flux boundary condition is also imposed for the mass and momentum conservation equations. Analytic self-similar solutions of transient temperature distribution in a semi-infinite solid with constant heat flux are used as the boundary condition for gas temperature:

where thermal conductivity of quartz  is 1.4 Wm-1K-1. In practice, this boundary is closer to isothermal than adiabatic conditions.

See more details and comparison with experimental data here.

 

 

 

 

 

 

 

 

 

 

Lab Information:

Ben T. Zinn Combustion Lab

635 Strong St, Atlanta, GA 30318

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Contact: Wenting Sun, 404-894-0524, wenting.sun at aerospace.gatech.edu