摘要:

Using matched asymptotic expansions for large activation energies of the reaction rates, we have studied the structure and stability properties of steady spherical premixed flames which, in this geometry, need not be supported by any source (or sink) of fresh (or burned) gases. The radius of such unsupported flames strongly depends on the differential diffusion of heat and reactant and is interpreted as a flame initiation criterion which corresponds to an unstable equilibrium. This radius must be exceeded for the flame to self-propagate outward. We then focus attention on two means to modify, or even suppress, such a critical flame size, viz.: (i) the effect of a central heal source of constant power, and (ii) the addition of small amounts of a hydrogen-like reactive species with large molecular diffusivity. Multiple steady solutions-including stable, non-propagating flames-or the disappearance of equilibrium solutions are exhibited as are qualitative changes in flame dynamics.

ISSN:0010-2202    

DOI:10.1080/00102208408923749

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abstract—A detailed chemical kinetic reaction mechanism is developed to describe the oxidation and pyrolysis of propane and propene. The mechanism consists of 163 elementary reactions among 4l chemical species. New rate expressions are developed for a number of reactions of propane, propene, and intermediate hydrocarbon species with radicals including H, 0, and OH. The mechanism is tested by comparisons between computed and experimental results in shock tubes and the turbulent flow reactor. The resulting comprehensive mechanism accurately reproduces experimental data for pressures from 1 to 15 atmospheres, temperatures from 1000 to 1700 K, and fuel-oxidizer equivalence ratios from 0.066 to pyrolysis conditions. The mechanism also predicts correctly laminar flame properties for propane and propene, and detonation properties for propane.

ISSN:0010-2202    

DOI:10.1080/00102208408923750

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

An analytical model of the hydrocarbon oxidation processes in an engine exhaust port was developed. A thermodynamic analysis was used to obtain the exhaust gas conditions as a function of lime and axial distance in the port. The major features of the exhaust port processes were described by submodels for the pan heat transfer, reaction rates. and instantaneous and overall levels of hydrocarbon concentrations as functions of engine conditions. Experimental determinations of the fraction of hydrocarbons oxidized in the exhaust port were obtained in engine experiments by the injection of a quench gas at selected locations within the port. By differencing the hydrocarbon concentrations observed during quenching and non-quenching operation, the degree of hydrocarbon oxidation was determined for each location. Analytical and experimental results were in good agreement for a range of engine operating conditions. The fraction of hydrocarbons reacted in the exhaust port ranged between about 2 and 70 percent for the various engine conditions examined for both the model and the experiment. These results were dominated by changes of gas temperatures, port residence times and oxygen concentration which occurred due to variations in the engine operating conditions and due to the injection of secondary air. The model was also used to examine hydrocarbon oxidation in the port as a function of cylinder gas temperature, port wall temperature, port length and port cross-sectional area.

ISSN:0010-2202    

DOI:10.1080/00102208408923751

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abstract-An aerothcrmochemical analysis has been made on the counterflow diffusion flame established in the forward stagnation region of a porous cylinder and the effects of transport properties on the temperature of the flame are investigated.By making the flame sheet approximation and adopting a model in which the fuel and oxygen are treated as trace species while an inert gas is treated as a major species. general analytic expressions for the boundary layer properties are obtained for large as well as moderate rates of injection.Based on several numerical calculations, it is found that the flame sheet temperature varies not only with the ejection rate but also with transport properties such as the Lewis number, and that the effects of transport properties on the flame temperature become remarkable when the flame is located around the stagnation point.A comparison with experimental results shows that the present analysis well describes the results qualitatively.

ISSN:0010-2202    

DOI:10.1080/00102208408923752

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Experimental flashpoint temperatures are reported for n-hexane-methanol, n-heptane-methanol, n-octane-methanol, and n-hexane-n-octane binary solutions. Results are discussed in terms of non-ideal thermodynamic solution behavior. A lower bound for methanol-n-alkane flashpoint temperatures is derived and validated.

ISSN:0010-2202    

DOI:10.1080/00102208408923753

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abstract-Three theoretical models of plane flames burning on a cooled porous-plug type of flame-holder are reviewed and compared with experimentally observed relationships between stand-off distance, flame speed and temperature.It is shown that for most practical burners their conductance is large and that for near adiabatic conditions, the order of the non-dimensional stand-off distance ceases to be 0(1), but is O(ln θ) where θ is the non-dimensional activation energy.

ISSN:0010-2202    

DOI:10.1080/00102208408923754

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor