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Author : R. F. McAlevy
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (66 download)
Download or read book Some Recent Experimental Observations on Flame Spreading Over Solid Fuel Surfaces written by R. F. McAlevy and published by . This book was released on 1969 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Sarzina Hossain
Publisher :
ISBN 13 :
Total Pages : 203 pages
Book Rating : 4.5/5 (355 download)
Download or read book Investigation of Opposed Flow Flame Spread Over Solid Fuels written by Sarzina Hossain and published by . This book was released on 2021 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: The opposed flow flame spread over flat solid fuels is of fundamental importance to the field of fire safety. Several features of opposed flow flame spread are experimentally, numerically and analytically investigated.Thermally thick slab of PolyMethylMethAcrylate (PMMA) was used to study the effects of opposed flow velocity (8-58 cm/s) and fuel thickness (6.6, 12.1 and 24.5 mm). The experiments were conducted with a Narrow Channel Apparatus (NCA) at Michigan State University (MSU). The flame spread rate results show that the maximum flame spread occurs at a lower flow velocity for relatively thicker fuel. The peak flame spread rate for 6.6 mm, 12.1 mm and 24.5 mm occurs at 18.5 cm/s, 12.1 cm/s and 10.3 cm/s, respectively. Several flame spread regimes: thermal, chemical and regressive burning are identified from the results. Flame spread regimes are usually depend on the opposed flow velocity. However, the flame spread rate for newly found regressive burning regime is independent of flow velocities. Visual observation of the flame indicates that the flame intensity augments with flow velocity for all thicknesses of PMMA. The comparison between NCA data and legacy data for similar material (PMMA) and thickness (12.1 mm) demonstrated excellent agreement, subject to the extension of the numerical and theoretical analysis to include relevant features of the flame spread stretch rate theory. The results also demonstrated the effectiveness of the stretch rate theory for markedly different experimental configurations. Although thick slab is used to perform tests, complete burn out of the samples for thickness 6.6 and 12.1 mm are observed at high opposed flow velocities (30 ℗ł 5 cm/s and higher). On contrary, the thickest sample (24.5 mm) did not go through complete burning. This indicates the nature of surface regression and its impact on flame spread rate.Based on the results, it can be emphasized that the factors controlling the flame front advancement involves both flame spread and surface regression. So, the burnt samples at different opposed flow velocities of 24.5 mm thickness from flame spread study is measured for surface regression depth experimentally. A semi-empirical correlation is developed to relate the flame spread and regression and to determine the mass loss rate from the burnt fuel surface. Mass loss rate is also a key aspect of characterizing the flammability of materials. Results show that the power law dependency of mass loss rate changes with opposed flow velocity. A comparison of power law exponents of current results and results from literature are made. Results demonstrate that the power law dependency at flow velocity 8.2, 10.3 and 12 cm/s is -0.5 which show excellent agreement with legacy work.Next, another study is conducted on the post-flame-spread 24.5 mm PMMA sample, burnt at opposed flow velocity 15 cm/s. Visual observation of post-burn sample shows the formation of significant number of internal bubbles. Three samples of similar thickness burnt at similar condition were investigated for bubble count and size. Results indicate higher and smaller bubble presence near the leading edge of the flame compared to the trailing edge side. Comparison of bubble size distribution with several distribution function demonstrates that the bubble size shows good agreement with Log-normal distribution function.Finally, the transient regression rate has been investigated analytically and numerically. The effect of external heat flux simulating flame heat flux is analyzed for PMMA considering it as an ideal-vaporizing solid. Results indicate a strong dependency of heat flux on material regression for a time duration. After a certain time period, the regression rate became insensitive to heat flux change. A scale analysis is performed to compare the analytical-numerical regression rate results with experimental surface regression depth. The predicted regression followed a similar pattern as the experimental surface regression.
Author : Michael J. Gollner
Publisher :
ISBN 13 : 9781267361677
Total Pages : 114 pages
Book Rating : 4.3/5 (616 download)
Download or read book Studies on Upward Flame Spread written by Michael J. Gollner and published by . This book was released on 2012 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental techniques have been used to investigate three upward flame spread phenomena of particular importance for fire safety applications. First, rates of upward flame spread during early-stage burning were observed during experiments on wide samples of corrugated cardboard. Results indicated a slower acceleration than was obtained in previous measurements and theories. It is hypothesized that the non-homogeneity of the cardboard helped to reduce the acceleration of the upward spread rates by physically disrupting flow in the boundary layer close to the vertical surface and thereby modifying heating rates of the solid fuel above the pyrolysis region. The results yield alternative scalings that may be better applicable to some situations encountered in practice in warehouse fires. Next, a thermally thick slab of polymethyl methacrylate was used to study the effects of the inclination angle of a fuel surface on upward flame spread. By performing experiments on 10 cm wide by 20 cm tall fuel samples it was found that the maximum flame-spread rate, occurring nearly in a vertical configuration, does not correspond to the maximum fuel mass-loss rate, which occurs closer to a horizontal configuration. A detailed study of both flame spread and steady burning at different angles of inclination revealed the influence of buoyancy-induced flows in modifying heat-flux profiles ahead of the flame front, which control flame spread, and in affecting the heat flux to the burning surface of the fuel, which controls fuel mass-loss rates. Finally, vertical arrays of horizontally protruding wood matchsticks were used to investigate the influence of the spacing of discrete fuel elements on rates of upward flame spread. Rates of upward flame spread were found to increase dramatically for spacings between 0 cm and 0.8 cm and experienced only a slight increase thereafter. Based on these observations, the influence of convective heating was hypothesized to dominate this spread mechanism, and predictions of ignition times were developed using convective heat-transfer correlations. Mass-loss rates followed a similar pattern and were predicted along with matchstick burnout times using a droplet burning theory extended for a cylindrical geometry.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722903831
Total Pages : 158 pages
Book Rating : 4.9/5 (38 download)
Download or read book A Model of Concurrent Flow Flame Spread Over a Thin Solid Fuel written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: A numerical model is developed to examine laminar flame spread and extinction over a thin solid fuel in lowspeed concurrent flows. The model provides a more precise fluid-mechanical description of the flame by incorporating an elliptic treatment of the upstream flame stabilization zone near the fuel burnout point. Parabolic equations are used to treat the downstream flame, which has a higher flow Reynolds number. The parabolic and elliptic regions are coupled smoothly by an appropriate matching of boundary conditions. The solid phase consists of an energy equation with surface radiative loss and a surface pyrolysis relation. Steady spread with constant flame and pyrolysis lengths is found possible for thin fuels and this facilitates the adoption of a moving coordinate system attached to the flame with the flame spread rate being an eigen value. Calculations are performed in purely forced flow in a range of velocities which are lower than those induced in a normal gravity buoyant environment. Both quenching and blowoff extinction are observed. The results show that as flow velocity or oxygen percentage is reduced, the flame spread rate, the pyrolysis length, and the flame length all decrease, as expected. The flame standoff distance from the solid and the reaction zone thickness, however, first increase with decreasing flow velocity, but eventually decrease very near the quenching extinction limit. The short, diffuse flames observed at low flow velocities and oxygen levels are consistent with available experimental data. The maximum flame temperature decreases slowly at first as flow velocity is reduced, then falls more steeply close to the quenching extinction limit. Low velocity quenching occurs as a result of heat loss. At low velocities, surface radiative loss becomes a significant fraction of the total combustion heat release. In addition, the shorter flame length causes an increase in the fraction of conduction downstream compared to conduction to the fuel. The...
Author : Jeffrey S. West
Publisher :
ISBN 13 :
Total Pages : 842 pages
Book Rating : 4.:/5 (318 download)
Download or read book Forced Opposed Flow Flame Spread Over Flat Solid Fuels in the Thermal, Near Quiescent and Chemical Kinetic Regimes written by Jeffrey S. West and published by . This book was released on 1998 with total page 842 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed numerical model of opposed-flow flame spread over solid fuels is developed. The model is used to study flame spread in three regimes of flame spread; the Thermal, Chemical Kinetic and Near Quiescent Regimes. Simplifying assumptions that have been historically applied to this problem are investigated and their effect on the flame spread rate and flame structure are quantified in each regime. A semi-empirical flame spread formula for thermally thick fuels is developed from knowledge of the dominant simplifying assumptions in this regime. Spread rate predictions compare well to experimental and computed results. This semi-empirical model provides field variables which previous theories are unable to predict. Mechanisms of heat transfer ahead of the flame are studied in each regime. Forward heat transfer though the solid fuel becomes more important in the Chemical Kinetic and Near Quiescent Regimes, a previously unknown result. The rate and path of forward heat transfer is found to depend strongly on simplifying assumptions and the flame anchor location. These results explain the relationship between previous analytical and experimental forward heat transfer results. A dimensionless criterion predicting the fuel thickness at which transition from thermally thick to thermally thin is developed which compares well with experimental and computed results. Finite-rate gas-phase chemical kinetics are found to be the cause of the super-thin regime of flame spread. A formula for the limiting flame spread rate in this regime is developed. Correlation of computed spread rates with the Damkohler number is revisited. Uncertainty in residence time due to uncertainties in characteristic velocity and gas-phase properties is found to be the cause of spread in the correlation. The Damkohler number alone explains variations in many parameters although it alone cannot explain changes in gas-phase activation energy. The boundary between the Near Quiescent and Thermal Regime is quantified using a dimensionless radiation number. A new extinction limit for thick fuels in the Near Quiescent Regime is discovered. Radiative losses cause the flame to grow small and spread so slowly that sufficient oxygen is not available to sustain the flame. Recent experimental results confirm this conclusion.
Author : United States. National Bureau of Standards
Publisher :
ISBN 13 :
Total Pages : 848 pages
Book Rating : 4.:/5 (31 download)
Download or read book Journal of Research of the National Bureau of Standards written by United States. National Bureau of Standards and published by . This book was released on 1976 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Liming Zhou
Publisher :
ISBN 13 :
Total Pages : 480 pages
Book Rating : 4.:/5 (33 download)
Download or read book Solid Fuel Flame Spread and Mass Burning in Turbulent Flow written by Liming Zhou and published by . This book was released on 1991 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow turbulence also has a significant effect on the flame extinction conditions, resulting in a smaller extinction velocity for larger flow turbulence intensity. For concurrent flow flame spread, it is found that the flow turbulence decreases the flame spread rate for both floor and ceiling geometries, mainly as a result of the flame length shortening at high turbulence intensity. It is also found that flow velocity intensifies the spread of the flame. The experimental data of flame spread rate, flame length and surface heat flux agree well with the formula obtained from a simplified thermal model, indicating that the heat transfer from flame to solid surface is the dominant controlling mechanism in the turbulent concurrent flame spread and, that the gas phase chemical reaction is of secondary importance.
Author : United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Space Science and Applications
Publisher :
ISBN 13 :
Total Pages : 1188 pages
Book Rating : 4.0/5 ( download)
Download or read book NASA Reports Required by Congress written by United States. Congress. House. Committee on Science, Space, and Technology. Subcommittee on Space Science and Applications and published by . This book was released on 1990 with total page 1188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.0/5 ( download)
Download or read book Fire Technology Abstracts written by and published by . This book was released on 1977 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Center for Fire Research (U.S.)
Publisher :
ISBN 13 :
Total Pages : 48 pages
Book Rating : 4.0/5 ( download)
Download or read book Attacking the Fire Problem written by Center for Fire Research (U.S.) and published by . This book was released on 1976 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 78 pages
Book Rating : 4.3/5 (91 download)
Download or read book NBS Special Publication written by and published by . This book was released on 1976 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 542 pages
Book Rating : 4.:/5 (26 download)
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1972 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 1052 pages
Book Rating : 4.:/5 (31 download)
Download or read book Fossil Energy Update written by and published by . This book was released on 1977 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Building and Fire Research Laboratory (U.S.)
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ISBN 13 :
Total Pages : 138 pages
Book Rating : 4.E/5 ( download)
Download or read book Building and Fire Research Laboratory Publications written by Building and Fire Research Laboratory (U.S.) and published by . This book was released on 1994 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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Total Pages : 136 pages
Book Rating : 4.3/5 (91 download)
Download or read book NIST Building & Fire Research Laboratory Publications written by and published by . This book was released on 1994 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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Total Pages : 394 pages
Book Rating : 4.:/5 (317 download)
Download or read book The Second International Microgravity Combustion Workshop written by and published by . This book was released on 1993 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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Total Pages : 656 pages
Book Rating : 4.F/5 ( download)
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1997 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
