摘要:

The complete time-history of a spatially homogeneous, constant volume model of self-initiated branched-chain explosion including high temperature dissociation arid recombination is examined. This model is motivated by characteristic chemical kinetic steps that are known to occur in H2-O2systems. The kinetic scheme consists of high activation energy/initiation and chain-branching reactions, a zero activation energy gas phase termination reaction, a high activation energy dissociation reaction and a zero activation energy recombination reaction. Perturbation techniques and asymptotic methods are employed to find the transient response of the system temperature and species concentrations, when the high activation energy limit is valid. The chain branching explosion time is defined by very rapid growth of the chain carriers with little change in temperature. It is found that the slow initiation reactions delay the chain branching explosion time significantly compared to that found in simple reactive systems. Subsequently, we find the major part of the thermal explosion where the temperature rises to a maximum value higher than the adiabatic explosion temperature. This difference results from the compression heating in a finite volume. Then the temperature decreases to its final equilibrium value due to the endothermic dissociation reaction.

ISSN:0010-2202    

DOI:10.1080/00102208608960306

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In this work we present the exact solution for the rate of creeping flame spread over thermally thin materials based on de Ris' (1969) formulation of the problem. The publication of the present work was prompted by a recent paper by Wichman and Williams (1984). These authors noted that de Ris (1969) obtained theoretical values for flame spread rates which are by a factor of two larger than recent experimental data (Fernandez-Pello et at., 1981). Wichman and Williams (1984) correctly suggested that this discrepancy between the theory and the experiment may have resulted from an approximation by de Ris(1969) of an irrational kernel by a rational function. The substitute kernel used by de Ris (1969) allowed him to obtain an analytical solution of the flame spread rates; however, this approximation may have introduced errors in the calculation of proportionality constants. The exact solution for creeping flame spread rates, which we present in the final analysis, agrees with the experimental data.

ISSN:0010-2202    

DOI:10.1080/00102208608960307

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Optical methods for particle size distribution measurements in practical high temperature environments have achieved feasibility and offer significant advantages over conventional sampling methods. The present paper describes a mobile electro-optical system which has been designed for general use in a wide range of research and industrial environments. The instrument has demonstrated capability for measuring individual particles in the size range 0.25-100 microns at number densities up to 1012/m3.- The system incorporates an in situ alignment procedure that is easy to set up and use in a wide variety of research and industrial environments. In addition to demonstration of the system's wide dynamic range, we show the utility of the in situ alignment method in hot (1100 K) turbulent flows where beam steering can be a problem. A major focus of the work described here is the application of the particle sizing technique to measurements of flyash formation in laboratory reactors. Number and mass frequency distribution measurements of flyash and pulverized coal obtained in a turbulent and a laminar flow reactor show that the raw pulverized coal contains large numbers of submicron particles similar to the flyash formed after combustion. These results suggest another source for much of the submicron flyash formed in pulverized combustion, with significant implications for control of fine particle emissions.

ISSN:0010-2202    

DOI:10.1080/00102208608960308

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Combustion behaviors, mainly focused on the secondary micro-atomization phenomenon of oil-in-water (O/W) and water-in-oil (W/O) hydrocarbon emulsion droplets, were observed under weightless conditions, and compared with the combustion behaviors of free-falling emulsion droplets under the effect of gravitation. Experimental results are reported on the burning of droplets of puren-paraffine (C5-C15), gas-oil, kerosene, JP-4, and O/W type JP-4/N2H4emulsions suspended on a quartz tip. It was found that under weightless (zero gravity, no buoyancy) conditions in air no violent micro-explosion would occur with regard to n-tridedane, -tetradecane, -pentadecane, gas-oil, and JP-4 emulsions, but, for all of them, the onset of micro-explosions resulting in instantaneous droplet disruption was observed in quiescent air or free-falling combustion in oxygen enriched atmospheres under one gravity. “Spray-like” and non-disruptive micro-atomization under weightless conditions and importance of gravity which promotes the micro-explosion are described.

ISSN:0010-2202    

DOI:10.1080/00102208608960309

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A time-resolved two-dimensional Rayleigh seatiering technique for mapping the temperature Held or a nonpremixed methane-hydrogen flame is presented. The laser Rayteigh scattered tight from an illuminated plane intersecting the flow field was digitized in an 8,000 data point array. The two-dimensional jnd quantitative character or the data makes it possible to apply calculations to the data, e.g., ensemble averaging and pattern recognition, to obtain more information on the flame structure. The results of these calculations are presented along with instantaneous measurements of the temperature field of the flame.

ISSN:0010-2202    

DOI:10.1080/00102208608960310

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208608960311

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor