P. V. Ferkul
Bio: P. V. Ferkul is an academic researcher. The author has contributed to research in topics: Premixed flame & Reynolds number. The author has an hindex of 1, co-authored 1 publications receiving 64 citations.
TL;DR: In this article, a numerical model was developed to examine steady, laminar flame spread and extinction over a thin solid fuel in low-speed concurrent flow, incorporating an elliptic treatment of the upstream flame stabilization zone near the fuel burnout point, and a parabolic treatment of downstream flame, which has a higher flow Reynolds number.
Abstract: A numerical model is developed to examine steady, laminar flame spread and extinction over a thin solid fuel in low-speed concurrent flow. The model incorporates an elliptic treatment of the upstream flame stabilization zone near the fuel burnout point, and a parabolic treatment of the downstream flame, which has a higher flow Reynolds number. This provides a more precise fluid-mechanical description of the flame than using parabolic equations throughout, and is the first time such an approach has been used in concurrent flame spread modeling. The parabolic and elliptic regions are coupled smoothly by matching boundary conditions. The solid phase consists of an energy equation with surface radiative loss and a surface pyrolysis relation. Calculations (with the flame spread rate being an eigenvalue) are performed for forced flow without gravitational influences in a range of velocities which are lower than those induced in a normal gravity buoyant environment. Steady spread with constant flame and...
••01 Jan 2015
TL;DR: In this paper, the authors introduce fire safety standards for flammability evaluation of solid material intended for use in a spacecraft habitat, and the difference between the limiting value in microgravity and the indices given by the standard test methods on the ground is discussed.
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.
Glenn Research Center1, Case Western Reserve University2, University of California, Berkeley3, University of Maryland, College Park4, University of Paris5, University of Bremen6, Moscow State University7, Hokkaido University8, European Space Research and Technology Centre9, University of Edinburgh10
TL;DR: In this paper, a large-scale flame spread experiment was conducted inside an orbiting spacecraft to study the effects of microgravity and scale and to address the uncertainty regarding how flames spread when there is no gravity and if the sample size and the experimental duration are, respectively, large enough and long enough to allow for unrestricted growth.
TL;DR: In this paper, a two-dimensional, opposed-flow, flame-spread model, with flame radiation, has been formulated and solved numerically, and a comparison of flammability limits and flame-spreading rates between opposing and concurrent spreading flames are made; both models contain the same assumptions and properties.
01 Jan 2009
TL;DR: In this article, a 5.18-s drop tower with a thin cellulose fuel was used to investigate flame spread in both concurrent and opposed flow in a spacecraft, with a focus on pressure/oxygen combinations that result in earth-equivalent oxygen partial pressures (normoxic conditions).
Abstract: Flame spread experiments in both concurrent and opposed flow have been carried out in a 5.18-s drop tower with a thin cellulose fuel. Flame spread rate and flame length have been measured over a range of 0–30 cm/s forced flow (in both directions), 3.6–14.7 psia, and oxygen mole fractions 0.24–0.85 in nitrogen. Results are presented for each of the three variables independently to elucidate their individual effects, with special emphasis on pressure/oxygen combinations that result in earth-equivalent oxygen partial pressures (normoxic conditions). Correlations using all three variables combined into a single parameter to predict flame spread rate are presented. The correlations are used to demonstrate that opposed flow flames in typical spacecraft ventilation flows (5–20 cm/s) spread faster than concurrent flow flames under otherwise similar conditions (pressure, oxygen concentration) in nearly all spacecraft atmospheres. This indicates that in the event of an actual fire aboard a spacecraft, the fire is likely to grow most quickly in the opposed mode as the upstream flame spreads faster and the downstream flame is inhibited by the vitiated atmosphere produced by the upstream flame. Additionally, an interesting phenomenon was observed at intermediate values of concurrent forced flow velocity where flow/flame interactions produced a recirculation downstream of the flame, which allowed an opposed flow leading edge to form there.
01 Jan 1996
TL;DR: In this article, an experimental and numrical investigation of ignition and the subsequent transition to flame spread over a thermally thin cellulosic sample is described, using a lamp as an external radiant source in a 50% oxygen atmosphere at three diffeirent wind velocities of 0.2, and 5 cm/s in a 10 s drop tower.
Abstract: An experimental and numrical investigation of ignition and the subsequent transition to flame spread over a thermally thin cellulosic sample is described. The experiments were conducted using a lamp as an external radiant source in a 50% oxygen atmosphere at three diffeirent wind velocities of 0.2, and 5 cm/s in a 10 s drop tower. The results show that there are no significants effects of the slow wind on the ignition-delay time. Photographic sequences of both the experiments and the calculations show that the wind increases the flame propagation speed in the upwind direction. while decreasing it in the downstream direction. The downstream clame fails the transition to flame spread and becomes a tail of the upstream flame. The downstream char front propagates much slower than that for the upstream direction. Three-dimensional, time-dependent numerical solutions to the Navier-Stokes equations are used to simulate the experiments. Three global degradation reactions describe the pyrolysis of the sample paper, and one gasphase reaction describes the combustion of the fuel gases. The model results reflect the qualitative features of the experiments and also are in reasonable quantitative agreement, give the uncertainty of the gasphase reaction mechanism.