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Stalcup, Erik JamesNumerical Modeling of Upward Flame Spread and Burning of Wavy Thin Solids
Master of Sciences, Case Western Reserve University, EMC - Aerospace Engineering
Flame spread over solid fuels with simple geometries has been extensively studied in the past, but few have investigated the effects of complex fuel geometry. This study uses numerical modeling to analyze the flame spread and burning of wavy (corrugated) thin solids and the effect of varying the wave amplitude. Sensitivity to gas phase chemical kinetics is also analyzed. Fire Dynamics Simulator is utilized for modeling. The simulations are two-dimensional Direct Numerical Simulations including finite-rate combustion, first-order pyrolysis, and gray gas radiation. Changing the fuel structure configuration has a significant effect on all stages of flame spread. Corrugated samples exhibit flame shrinkage and break-up into flamelets, behavior not seen for flat samples. Increasing the corrugation amplitude increases the flame growth rate, decreases the burnout rate, and can suppress flamelet propagation after shrinkage. Faster kinetics result in slightly faster growth and more surviving flamelets. These results qualitatively agreement with experiments.

Committee:

James T'ien (Committee Chair); Joseph Prahl (Committee Member); Yasuhiro Kamotani (Committee Member)

Subjects:

Aerospace Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

modeling;simulation;numerical modeling;combustion;computational combustion;direct numerical simulation;flame spread;burning;wavy;corrugated;fire dynamics simulator;FDS;fuel structure;fuel geometry;complex geometry;cardboard;

Rajput, PrafullaA Model of the Emission and Dispersion of Pollutants From a Prescribed Forest Fire in a Typical Eastern Oak Forest
Master of Science (MS), Ohio University, 2010, Chemical Engineering (Engineering and Technology)
A simulation model is completed to study the emission and dispersion of carbon dioxide, carbon monoxide, particulate matter and the temperature variation caused from prescribed forest burning in a typical eastern hardwood forest. The purpose of the present study is to estimate of the output quantities from the fire and exposure to them for life in the vicinity of the fire. A FORTRAN code is generated which is furnished as an input to the Fire Dynamic Simulator (FDS) model to simulate the realistic scenario of a prescribed fire which occurred at the Arch Rock forest in south eastern Ohio. This FORTRAN model, which provided terrain elevation, heat release, wind flow, soot yield data for the Arch Rock burning scenario, was built using MATLAB. The heat data was collected by hovering planes over the fire carrying remote sensing equipment which recorded the Infra Red radiation from the fire. The results show spatially and temporally resolved emissions from the fire and how long surrounding life is exposed. The resultant concentration values give an idea of the extent of the harmful pollutants released from the fire.

Committee:

Valerie L. Young, PhD (Advisor)

Subjects:

Chemical Engineering; Engineering; Environmental Science; Fluid Dynamics

Keywords:

Fire Dynamics simulator; prescribed fire modeling; FDS; forest fire modeling;

Endo, MakotoNumerical modeling of flame spread over spherical solid fuel under low speed flow in microgravity: Model development and comparison to space flight experiments
Doctor of Philosophy, Case Western Reserve University, 2016, EMC - Mechanical Engineering
Flame spread over solid fuel presents distinctive characteristics in reduced gravity, especially when the forced flow velocity is low. The lack of buoyancy allows a blue, dim flame to sustain where the induced velocity would otherwise blow it off. At such low velocities, a quenching limit exists where the soot content is low and the effect of radiative heat loss becomes important. The objective of this study is to establish a high fidelity numerical model to simulate the growth and extinction of flame on solid fuels in a reduced gravity environment. The great importance of the spectral dependency of the gas phase absorption and emission were discovered through the model development and therefore, Statistical Narrow-Band Correlated-k (SNB-CK) spectral model was implemented. The model is applied to an experimental con figuration from the recent space experiment, Burning And Suppression of Solids (BASS) project conducted aboard the International Space Station. A poly(methyl methacrylate) (PMMA) sphere (initial diameter of 2cm) was placed in a small wind tunnel (7.6cm x 7.6cm x 17cm) within the Microgravity Science Glovebox where flow speed and oxygen concentration were varied. Data analysis of the BASS experiment is also an important aspect of this research, especially because this is the first space experiment that used thermally thick spherical samples. In addition to the parameters influencing the flammability of thin solids, the degree of interior heat-up becomes an important parameter for thick solids. For spherical samples, not only is the degree of internal heating constantly changing, but also the existence of stagnation point, shoulder, and wake regions resulting in a different local flow pattern, hence a different flame-solid interaction. Parametric studies using the numerical model were performed against (1) chemical reaction parameters, (2) forced flow velocity, (3) oxygen concentration and (4) amount of preheating (bulk temperature of the solid fuel). Flame Spread Rate (FSR) was used to evaluate the transient effect and maximum flame temperature, standoff distance and radiative loss ratio were used to evaluate the spontaneous response of the gas phase to understand the overall response of the burning solid fuel. After evaluating the individual effect of each parameter, the efficacy of each parameter was compared. Selected results of this research are: [1] Experimental data from BASS and numerical simulation both showed that within the time period between ignition until the flame tip reaches the shoulder of the sample, the flame length and time have almost a linear relation. [2] Decreasing forced flow velocity increases the radiative loss ratio whereas decreasing oxygen mole fraction decreases the radiative loss ratio. This fi nding must be considered in the effort to replicate the behavior of flame spread over thick solid fuels in microgravity on earth. [3] Although the standoff distance will increase when the forced flow velocity is decreased as well as when the oxygen mole fraction is decreased, the forced flow velocity has a much stronger effect on the standoff distance than the oxygen mole fraction. [4] Unlike the previous two comparisons, the effect of forced flow velocity and oxygen mole fraction on the maximum flame temperature was at similar level, reduction of either parameter would result in lowering the maximum flame temperature. [5] The effect of preheating on the flame spread rate becomes stronger when either the oxygen flow rate or forced flow velocity becomes larger. Depending on which element is more important, we can distinguish oxygen flow rate driven flame spread from preheating driven flame spread. Findings of this research are being utilized in the design of the upcoming space experiment, Growth and Extinction Limits of solid fuel (GEL) project. This research is supported by the National Aeronautics and Space Administration (NASA). This work made use of the High Performance Computing Resource in the Core Facility for Advanced Research Computing at Case Western Reserve University and the Ohio Supercomputer Center.

Committee:

James S. T'ien (Committee Chair); Yasuhiro Kamotani (Committee Member); Fumiaki Takahashi (Committee Member); Erkki Somersalo (Committee Member)

Subjects:

Aerospace Engineering; Mechanical Engineering

Keywords:

Numerical modeling; flame spread; solid fuel; spherical fuel; microgravity; combustion; space experiment; NASA; GEL; SoFIE; SNB-CK; Radiation; Heat transfer; Finite Element; FEM; FDS; Microgravity Experiment; NASA-STD-6001; BASS; SIFI; FSR; axisymmetric;