Kevin Tolejko

Bio: Kevin Tolejko is an academic researcher from Case Western Reserve University. The author has contributed to research in topics: Flame spread & Combustion. The author has an hindex of 2, co-authored 2 publications receiving 16 citations.

A Computational Study on Flame-Solid Radiative Interaction in Flame Spread Over Thin Solid-Fuel

Abstract: A detailed, two-dimensional, laminar flame spread model over a thin solid is solved in both a normal gravity downward spread configuration and in a microgravity quiescent atmosphere configuration. The radiation transfer equation is solved using discrete ordinates methods. While flame radiation plays only a secondary role in normal gravity spread, it is crucial in microgravity By using the solid fuel total emittance and total absorptance as parameters, systematic computations have been performed to isolate the roles of flame radiative loss to the ambient, absorption of flame radiation by the solid and solid emission

Effects of fuel Lewis number on flame spread over solids

Abstract: Using a detailed two-dimensional numerical model, a systematic investigation has been made to study the effect of fuel Lewis number (Le F = α /D F ) and mass transfer on flame spread over thin solids. The fuel Lewis number affects the flame spread rates for both concurrent and opposed flames over thin fuels. The dependence of the flame spread rate on Le F for these two spreading modes is, however, not the same. In opposed flame spreads (zero-gravity, self-propagation, and normal gravity downward propagation), the flame spread rate vs. Le F curve is non-monotonic with a maximum value occurring at an intermediate value of Le F = 0.5. In steady, concurrent spread in zero-gravity with low-speed flow and a constant flame length, the flame spread rate decreases with Le F in a monotonic manner. By using the computational model as a tool, the effects of fuel mass diffusion perpendicular to and parallel with the solid surface are isolated to obtain more physical insight on the two-dimensional aspect of fuel mass transfer on flame spread. In addition, the model has also been used to decouple the solid evaporation process so that the fuel diffusion effect in the gas-phase can be isolated. Both of these theoretical exercises contribute to the understanding of mass transfer effects on the flame spreading phenomena over solids.

Solid combustion research in microgravity as a basis of fire safety in space

Abstract: This paper introduces fire safety standards for flammability evaluation of solid material intended for use in a spacecraft habitat. Two types of existing standards include material evaluation by pass/fail criteria corresponding to Test 1 of NASA STD 6001B and evaluation by a flammability index such as maximum oxygen concentration (MOC) corresponding to the improved Test 1. The advantage of the latter is the wide applicability of the MOC index to different atmospheres in spacecraft. Additionally, the limiting oxygen index (LOI) method is introduced as a potential alternative index for the evaluation using the improved Test 1 method. When criteria based on an index such as MOC or LOI are applied for material screening, the discrepancy of the index to the actual flammability limit in microgravity such as minimum limiting oxygen concentration (MLOC) is essential information for guaranteeing fire safety in space because material flammability can be higher in microgravity. In this paper, the existing research on the effects of significant parameters on material flammability in microgravity are introduced, and the difference between the limiting value in microgravity and the indices given by the standard test methods on the ground is discussed. Finally, on-going efforts to develop estimation methods of material flammability in microgravity according to normal gravity tests are summarized.

Literature Survey of Numerical Heat Transfer (2000–2009): Part II

Abstract: A comprehensive survey of the literature in the area of numerical heat transfer (NHT) published between 2000 and 2009 has been conducted Due to the immenseness of the literature volume, the survey

Numerical modeling of limiting oxygen index apparatus for film type fuels

Abstract: A detailed three-dimensional numerical model is used to compute the flow pattern and the flame behavior of thin solid fuels in a rectangular column that resembles a standard Limiting Oxygen Index (LOI) device. The model includes full Navier-Stokes equations for mixed buoyant-forced flow and finite rate combustion and pyrolysis reactions so that the sample LOI can be computed to study the effect of feeding flow rate, sample width and gravity levels. In addition to the above parameters, the sample location in the column and the column cross-sectional area are also investigated on their effect on the ambient air entrainment from the top.