摘要:

By asymptotic methods, which treat the ratio of the thermal energy to the activation energy for gasification as a small parameter, the entire temperature-time history is derived for a semi-infinite solid, whose surface is subjected to a constant energy flux. It is found that an initial stage of inert heat-conduction is separated from a final stage of transport-controlled gasification by a short transition stage, which contains reactive-diffusive and transient-diffusive zones if distributed gasification occurs. The time to onset of gasification is obtained from an analysis of the transition stage. The manner of approach to quasisteady regression is described by the perturbation analysis. The results are of interest in connection with ignition of reactive solids which experience exothermic reactions only in the gas phase. In particular, it is shown that within the accuracy to which experiments can be performed, the dependence of ignition time on heat flux for such materials is identical with the dependence for materials which exhibit condensed-phase or interfacial ignition reactions, provided that the gas-phase reaction time is small compared with the time to onset of gasification.

ISSN:0010-2202    

DOI:10.1080/00102207508946653

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Experimental results on the gas-phase extinction of diffusion flame for the pyrolyzed products of PMMA (polymethylmethacrylate) rods burning in laminar flows of O2/Nj mixtures are reported. Critical extinction conditions in terms of oxygen concentration, oxidizer mass flux and pressure are established. Kinetic parameters for the overall gas-phase oxidation process have been obtained from these results with the aid of recently-developed theoretical analyses for extinction of diffusion flames in the stagnation-point boundary layer of condensed fuels. Thus, on the basis of an overall reaction of order one with respect to oxygen and one with respect to PMMA-pyrolysis products, the experimental results provide values of 21 kcal/mole for the overall activation energy and of 3 × 1012cm5/ mole sec for the preexponential factor.

ISSN:0010-2202    

DOI:10.1080/00102207508946654

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The complete reaction history of a spatially homogeneous, adiabatic system composed of a combustible mixture of fuel and oxidizer is described for the case of large activation energy. The time history of the temperature rise and fuel consumption is calculated for the ignition period, the rapid reaction (explosion) phase and for the approach to the final equilibrium state. A detailed estimate of the explosion time scale is found. The limitations of classical ignition theory are discussed.

ISSN:0010-2202    

DOI:10.1080/00102207508946655

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Some theoretical computations are completed, illustrating possible influences of reaction mechanism on the structure of the reaction zone, for reactions which occur by a straight-chain process. The occurrence of single and of double reaction fronts is identified. It is demonstrated that while a double front may occur for hydrogen-fluorine systems, in the case of the hydrogen-bromine reaction only a single front is obtained.

ISSN:0010-2202    

DOI:10.1080/00102207508946656

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The gross structure of turbulent jet diffusion flames developing in a coflowing high temperature vitiated air stream was examined experimentally and theoretically. The observed radial profiles of total pressure within the flame were similar in all axial positions, while the temperature profile showed a sharp peak at the most luminous position. The measured temperature profiles in the upstream region of flame were found to correlate satisfactory with those of a simplified analysis based on the flame surface approximation and the boundary layer similar solution for the velocity field.

ISSN:0010-2202    

DOI:10.1080/00102207508946657

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

It is observed that a layered, unconfined combustible mixture supports a flame propagation velocity of 4 to 5 times the laminar flame speed of the stoichiometric mixture of fuel and air. This effect which has been observed by some and more recently in this laboratory, has never been adequately explained. It is in contrast to the classical soap bubble experiment, in which the flame propagation velocity is of the order of 7 to 8 times the laminar flame speed, that is, the order of the unburned to burned gas density ratio

ISSN:0010-2202    

DOI:10.1080/00102207508946658

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102207508946659

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The characteristics of an axisymmetric flame propagating over a thermally thick fuel bed of polymethyl methacrylate have been studied. For a pyrolysis region diameterdp> 5 cm, the flame propagation rate is constant atV= 0.0050 cm/sec. The mass loss rate has been measured as a function of flame size and compared with results for pool burning. The measured surface temperature profile in the near field (0.4 cm) ahead of the flame has been found to be independent of flame size and to give a ratio of preheat distance to flame radius of curvature which is much less than one. Radiation measurements from the flame to the fuel surface ahead of the flame have been made and are shown to account for the slow temperature rise at distances greater than 0.4 cm ahead of the flame. Fordp> 2.7 cm the flame oscillates and photographic sequences showing the development of the flame over an oscillation cycle are given.

ISSN:0010-2202    

DOI:10.1080/00102207508946660

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

The influence of temperature fluctuations on Nitric oxide formation has been investigated by calculating NO levels with a range of prescribed temperature fluctuations about various mean temperatures. It has been found that NO levels about an order of magnitude above those predicted with zero fluctuation may arise at temperature fluctuation levels typically to be found in gas-turbine combustion chambers

ISSN:0010-2202    

DOI:10.1080/00102207508946661

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor