摘要:

The variation with heat flow geometry of minimum heat source temperature which causes smolder initiation in cellulosic insulation has been examined for eight configurations. These configurations range from a wire-like source, to a flat planar source, to a corner formed by planar sources; they simulate such heat sources as electrical conductors and light fixtures and span the geometry range seen by insulation in practice. The ignition temperature for the same 20 cm deep insulation layer varies from 235°C (corner source) to 385°C (wire source). Other variables such as bulk density or the presence of smolder retardants have much less effect on ignition temperature. This behavior is rationalized in an approximate manner by simple heat generation/ heat flow arguments; it is predicted semi-quantitatively by a numerical model using reaction kinetics derived from thermal analysis. A smolder ignitability test for cellulosic insulations is suggested that simulates exposures to recessed light fixtures. The data here provide a correlation between results of such a test and ignition temperatures in other configurations.

ISSN:0010-2202    

DOI:10.1080/00102208108946950

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The properties of a fly ash cloud which determine its radiative influence in furnaces are its dust burden, projected surface area and its mean absorption and scattering efficiency. The first property can be estimated by stoichiometry, the second by laboratory sizing of the ash and the radiative efficiencies should be related to its chemical character.

ISSN:0010-2202    

DOI:10.1080/00102208108946951

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A closed model equation is derived which describes the evolution of the single-point, joint probability density function of a reacting scalar and its gradient in a turbulent advection field. To obtain a closed form a relaxation model is assumed for molecular diffusion and a white noise Kubo approximation for the advection. With this model, the roles of mean velocity, molecular mixing, chemistry and turbulent advection are examined for their effects on the statistics of a transported scalar and its gradient. It is shown that their joint statistical dependence becomes less significant as the Reynolds number increases. An analogy between transport in composition space due to chemical reaction and mass conservation in compressible gas dynamics leads to a methodology for determining the statistical dependence induced by chemical reaction

ISSN:0010-2202    

DOI:10.1080/00102208108946952

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Flame-spreading over the surface of a flat solid propellant in a turbulent boundary layer has been investigated experimentally. Nitrogen gas was used as a main flow gas, and noncatalyzed and catalyzed double-base propellants were used as specimens. Experimental measurements of the flame-spreading were conducted as a function of the main stream velocity in a small scale wind tunnel under atmospheric pressure. After the upstream edge of the specimen was ignited, the flame-spreading phenomena were investigated photographically. The temperature of the unburned propellant surface and the heat flux through the gas-phase to the unburned surface were measured with thermocouples and a calorimeter. It is found that the flame does not always spread downstream continuously but a secondary (and/or tertiary) ignition occurs on the unburned surface far downstream of the main burned region at the lower main stream velocity or for a propellant with higher normal burning rate, and that in general the history of the unburned surface temperature is divided into three stages; (a) the surface temperature rises with time, (b) it reaches a plateau, and (c) it rises again with time up to the critical temperature.

ISSN:0010-2202    

DOI:10.1080/00102208108946953

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A theoretical study is conducted of the spread of flames in gas flows moving in the direction of flame propagation. The study draws on the fact that concurrent flame spread configurations have common general characteristics, thus allowing a unified treatment of the problem. The analysis, although approximate, provides an analytic expression for the rate of flame spread over the surface of thermally thick fuels in laminar gas flow configurations that accept a similarity solution. The predicted flame spread rates for these particular flows provide limits for the rates of spread in other non-similar gas flow configurations.

ISSN:0010-2202    

DOI:10.1080/00102208108946954

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

This paper gives an analysis of the influence of solid matter consumption on the critical diameters for the ignition and extinction of a single particle of solid fuel. The Thomas theory of ignition with reactant consumption for the pre-mixed system was adopted for obtaining the formula for the critical diameters of ignition and extinction. The calculations made for the coal particle show that consumption deflects the critical diameter of extinction about two times stronger than that for ignition

ISSN:0010-2202    

DOI:10.1080/00102208108946955

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Previous work on the addition of methanol, ethanol and water to puren-paraffins is extended to a conventional No. 2 distillate fuel oil. Both the effect of additive content in the fuel oil and oxidizer concentration in the environmental flow on the existence and character of the disruptive behavior of thesesolutionsandemulsionsare investigated.

ISSN:0010-2202    

DOI:10.1080/00102208108946956

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Measurement of coking rate under isothermal conditions has been conducted for a variety of test conditions. Variables included time, fuel flow rate, tube diameter, and surface roughness. Coking rate increases with temperature and Reynolds number, but is not dependent on surface roughness. The activation energy is approximately 10,000 cal/mole. Examination of deposits by infrared spectroscopy and the electron microprobe indicates that oxygen is present in large concentration, both singly- and doubly-bonded to carbon; in addition, nitrogen may be present in an imide structure. The aromatic content of the deposit is higher than that of the unstressed fuel. Transmission electron microscopy indicates the presence of agglomerates of particles about 15 Å in diameter. This suggests that insoluble particles originate within the liquid, although the low overall activation energy and the dependence of coking rate on Reynolds number suggest that oxidation of the fuel is mass-transfer-dependent and surface-catalyzed. Gas chromatographic and infrared analysis of polar fractions of stressed and unstressed fuel are virtually identical, indicating that deposit precursors exist at very low levels.

ISSN:0010-2202    

DOI:10.1080/00102208108946957

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208108946958

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor