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Tuesday, July 14, 2020 | History

3 edition of Imposed radiation effects on flame spread over black PMMA in low gravity found in the catalog.

Imposed radiation effects on flame spread over black PMMA in low gravity

Imposed radiation effects on flame spread over black PMMA in low gravity

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Published by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC, Springfield, Va .
Written in English

    Subjects:
  • Radiation effects.,
  • Microgravity.,
  • Flame propagation.,
  • Fuel combustion.,
  • Polymethyl methacrylate.,
  • Plastic propellants.

  • Edition Notes

    Statement[S.L.] Olson, U. Hegde.
    Series[NASA contractor report] -- NASA-CR-202553., NASA contractor report -- NASA CR-202553.
    ContributionsHegde, U., United States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL15507313M

    This work studies the effect of ambient pressure and oxygen concentration, on opposed flame spread and mass burning in cylindrical samples of polymethyl methacrylate (PMMA). Experiments in normal gravity are conducted using ambient pressures ranging between and 60 kPa and oxygen concentrations between 21% and 35% by volume, while.   FLASH radiation may one day enable cancer patients to receive their full radiation dose within seconds and with fewer side effects than conventional radiation treatments.

    sorption of the imposed thermal radiation. Because ignition times ar. sensitive to the wavelength of the imposed radiation it is desirable (bu1 not always practical) to use a long wavelength infrared radiant sour-c­ characteristic of fires., thermally thick b. Flame Spread - Around basic creeping flame over a smooth solid surface. interaction of the radiation energy with the polymer itself. Material Evaluation When weighing the radiation stability of a polymer and the ultimate success of a component or medical device, the following factors should be taken into consideration: • Stabilizers and antioxidants added to a polymer can reduce the effects of.

    The "attracted" object will also cast a shadow on the shadowing object and thus the resultant force between the two objects will depend on the mass of both objects. This is compliant with Newton's law of gravity: F=GmM/r 2. This shadowing effect can easily describe the high/low tides of sea level, depending upon the shadowing position of the moon.   As radiation exposure around the Fukushima nuclear power plant reach levels of mSv per hour (although they've since gone down), we .


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Imposed radiation effects on flame spread over black PMMA in low gravity Download PDF EPUB FB2

Imposed Radiation Effects on Flame Spread over Black PMMA in Low Gravity. The objective of this work is to determine the effect of varying imposed radiation levels on the flame spread and. Get this from a library. Imposed radiation effects on flame spread over black PMMA in low gravity.

[Sandra L Olson; U Hegde; United States. National Aeronautics and Space Administration.]. Imposed Radiation Effects on Flame Spread over Black PMMA in Low Gravity. By S. Olson and U. Hegde. Abstract. The objective of this work is to determine the effect of varying imposed radiation levels on the flame spread and burning characteristics of PMMA in low gravity.

The NASA Learjet is used for these experiments; it provides an Author: S. Olson and U. Hegde. Imposed Radiation Effectson Flame Spread over Black PMMA inLow Gravity NASA-CRS3 Olson, NASA Lewis Research Center U.

Hegde, Nyma Inc. / obj voof work" " ofv, posed di tionlevelson fl e of PMMA in low gravity. _l_e°dAsT_a_eetesff_x_f° e experiments;,tprov,nt°tlu gs,orapproxunat_,y 20 seconds. The tests consisted of determining the opposed flame spread rate over PMMA cylinders under low-flow velocities ranging from to 8 cm/s and oxygen concentrations from 15% to 21%.

The ignition delay and subsequent downward flame spread over a finite-length PMMA slab with the effect of radiation included in a two-dimensional wind tunnel are investigated using the opposed.

The objective of this work is to study the effect of pressure, and consequently buoyancy and indirectly gravity, on downward flame spread rate over cylindrical samples of polymethyl-methacrylate. Flame spread over a thin polymethylmethacrylate sheet in microgravity is investigated experimentally and analytically.

A scale analysis yields a simple equation, η+R/ζ=1, which states the radiation loss is a function of relative flow velocity and the fuel prediction with the scale analysis states that the reduction in the relative flow velocity enlarges the size of the preheat.

The development of liquid fires commonly accompanies with the external heat radiation. This subject concentrates on the laboratory-scale experiments ( cm × cm × cm) on flame spread over jet fuel of RP-3 with radiant heat fluxes of,and kW/m results show that the flame behaviors, subsurface flow and heat transfer mechanism depend strongly on the.

Five radiation models are evaluated at atmospheric and elevated oxygen levels at flow velocities covering the range of the three flame spread regimes over a thin PMMA fuel. While radiation is found to have a strong influence on flame temperature in all regimes, it is most significant at low flow velocities of the so-called microgravity regime.

For opposed-flow flame spread over thick solid fuels, to get an overall picture of the dependence of the flame spread rate on the gas flow velocity over the full range, we combine the present experimental data with some currently available experimental results and plot in Fig.

9 the normalized flame spread rate, V f /V f,EST, as a function of. A computational model of flame spread over a thermally thick solid fuel in an opposing-flow environment is presented.

Unlike thermally thin fuels, for which the effect of fuel surface radiation is negligible for high levels of opposing flow, fuel surface radiation is important for thermally thick fuels for all flow levels.

Beaulieu and Dembsey [13] made some experiments on the effect of oxygen on flame heat flux in horizontal and vertical orientations for black PMMA, propylene and black polyoxymethylene (POM) in. Flame spread rates and burned fuel sample fractions agree. The results indicate that the NCA quantitatively captures the essential features of these microgravity tests, and thus provides a new method to study non-buoyant flame spread without the costs of actual low-gravity testing.

POLYMETHYLMETHACRYLATE COMBUSTION IN A NARROW CHANNEL APPARATUS SIMULATING A MICROGRAVITY ENVIRONMENT _____ A Thesis Presented to the Faculty of San. A series of Shuttle tests, the Solid Surface Combustion Experiment (SSCE), provided quantitative data on the effects of atmospheric oxygen concentration and total pressure on thin-paper flame spread in quiescent micro- gravity [27].

A summary of flame-spread rate determina- tions is shown in Fig. Electromagnetic radiation is a form of radiation that includes visible light, radio waves, gamma rays, and X-rays, in which electric and magnetic fields vary simultaneously.

The dissipation factor is an important characteristic to be considered in situations where plastics may potentially be exposed to such electromagnetic waves. Flame-spread takes place once the fuel is ignited and the flame spreads over the solid fuel once the surface attains the temperature for ignition, Tig.

The test measures the flame-spread velocity for different heat-fluxes and a fit of theory to the data permits the empirical determination of what is labeled the “flame spread parameter”, φ.

Correlating flame geometry in opposed-flow flame spread over thin fuels Model calculation of steady upward flame spread over a thin solid in reduced gravity Numerical model of upward flame spread on practical wall materials. Factors Affecting Gamma Radiation Resistance of Plastic Radiation resistance of a material greatly depends on: Polymer formulation (Additives, reinforcement, crosslinking in elastomers etc.) Conditions of radiation exposure such as the environmental atmosphere, temperature, dose rate, mechanical stress, etc.

It is important to note that. In this work, experiments were conducted to evaluate the effect of exterior radiation on vertical PMMA fires. The mass loss, flame height, and radiant heat flux were measured. A critical heat flux of 10 kW/m 2 was determined as a boundary for radiation blockage effect.

For lower exterior radiation heat fluxes .An upper layer of a low-density combustible liquid and a lower layer of a higher-density combustible liquid. What effect does an increase in atmospheric pressure have on the rate of flame spread over solid surfaces?

the incandescent orange-yellow glow within a flame and is/are seen as black smoke emanating from the flame? Soot.Acute radiation dose usually refers to a large dose of radiation received in a short period of time.

Chronic dose refers to the sum of small doses received repeatedly over long time periods, for example, 20 mrem (or millirem, which is 1-thousandth of a rem ( mSv) per week every week for several years.