摘要:

Discrete·ordinates S2' 54, 56 and 58 approximations arc used to study radiative transfer in athree-dimensional furnace with complex geometry including cooling-pipes in the combustion chamber. Theability of the discrete-ordinates method to model highly-directional shadowing effects caused by the internalpipes is illustrated. Predicted values for incident wall flux and net radiative transfer to the pipes are shown tocompare well with experimental data. The large energy sink produced by the pipes minimizes the sensitivityof results to variations in wall emissivity. The 54 approximation is shown to produce results of adequateaccuracy except in cases where detailed modeling of the pipe shadows requires the higher order 56 and 58approximations. Results from mesh densities of 76.000, 388,000 and 815,000 cells show different mesh sizesdo not significantly alter incident flux or net heat transfer predictions,

ISSN:0010-2202    

DOI:10.1080/00102209308947241

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new integral thermal pyrolysis model for the transient pyrolysis of charring and on-charring materials has been developed and evaluated by comparison of the results with exact solutions. The purpose for the development of this simple model has been the desire for predicting pyrolysis histories of materials exposed to pre heat fluxes by using “equivalent” properties tailored to the present model and common flammability test measurements. The pyrolyzing material is divided into a char layer and a unpyrolyzed (virgin) layer where the material has not yet pyrolyzed. These two layers are separated by an isothermal interface which is at a pyrolysis temperature (characteristic of the material). At this interface, heat is transferred to the virgin layer, causing further pyrolysis of the material (namely a thermal pyrolysis model is used). A one-dimensional transient heat conduction model is used to predict the heat transfer within the material. Exponential temperature profiles were assumed for the heat conduction model. Using a rwo-equation 9-moment method, the original partial differential equations were transformed into a set of two ordinary differential equations for each layer. These equations were numerically salved to I) determine the pyrolysis rate. regression depth and surface temperature, and 2) establish a dimensional and sensitivity analysis. The model has been shown to be very accurate (errors ~ 2%) from comparisons between numerical results and exact solutions. Despite the neglect of derailed chemical kinetic (Arrhenius) pyrolysis expressions, the accuracy of the integral model together with its simplicity has allowed the deduction of pyrolysis properties of materials by using common flammability test data as it ';ill be proved in a subsequent paper.

ISSN:0010-2202    

DOI:10.1080/00102209308947242

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In order to see the accurate role of low temperature reactions in autoignition nd nock phenomena, oxidation of stoichiometric hydrocarbons/air mixtures has been performed in a CFR engine and in a flow system. The results show that reactions of isomerization of R02 radicals areimponant for hydrocarbons containing five or more carbon atoms. The pernxidic compounds formed through these isomerization reactions are alkylketohydroperoxides. A correlation is made between fuel structure, octane number. isomerization reactions and autoignition. A chemical kinetic model. created to interpret autoignition and knock. reproduces the results obtained with n-heptane and the influence of engine parameters as speed, intake temperature and pressure.

ISSN:0010-2202    

DOI:10.1080/00102209308947243

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In our laboratory, we have attempted to simulate MSW-incineration with a spouted bed combustion system. Our studies show that the combustion of simple chlorinated compounds can lead to some potentially important precursors to PCDDIF. This paper presents results from the lean combustion of 1,2·dichlorobenzene. The effect of equivalence ratio and the chlorine to carbon ratio in the fuel are investigated. Maxima in CE, ORE and PICs are observed as a function of equivalence ratio. The carbon to chlorine ratio influences the chtcrobcnzcne (CB) to chlorophenols (CP) ratio in the products.

ISSN:0010-2202    

DOI:10.1080/00102209308947244

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The kinetics of hydrogen oxidation in supercritical water were determined in an hermal, ug-flow reactor at temperatures between 495 and 600°C and at a pressure of 246 bars. Inlet hydrogen and oxygen concentrations ranged from 0.4 × 10−6to 4.6 × 10−6mol/cm3, with fuel equivalence ratios varying from 0.04 to 4.0. Over the range of conditions studied, the kinetics were independent of oxygen concentration and exhibited a first-order dependence on hydrogen concentration, with an activation energy of 372±34 kJ/mol and a pronounced induction time. An elementary reaction model, based on existing gas-phase models and modified to account for the high-pressure environment, was able to reproduce closely the experimental results. including the overall concentration dependencies (reaction orders) and activation energy. Based on the model. important elementary reactions were identified and details of the oxidation mechanism were inferred.

ISSN:0010-2202    

DOI:10.1080/00102209308947245

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor