摘要:

The method of activation energy asymptotics (AEA) is used to study the structure and extinction characteristics of premixed laminar flames in two counterflowing reactant streams such that a layer of products is bounded by two reaction zones. The analysis includes the influences of realistic density variations and of large rates of strain. Account is taken of Lewis numbers different from unity and of different temperatures in the two reactant streams. It is found that abrupt extinction occurs either upon merging of the two reaction zones or prior to merging depending on the Lewis number and on the temperature difference of the two streams. In the adiabatic case Lewis numbers suitably greater than unity, i.e., greater than a critical value, are found to be needed for extinction to occur prior to merging. The critical Lewis number decreases as the temperature difference increases such that at suitably large differences extinction prior to merging occurs for Lewis numbers less than unity. Density nonuniformities associated with heat release are shown to increase the critical Lewis number with increases in such release if the reactant temperature is held fixed but not if the adiabatic flame temperature is held fixed. Expressions are developed for the calculation of reaction zone locations and of their variation with rate of strain, Lewis number and temperature difference. Predictions obtained from the analysis are found to be in qualitative agreement with experimental results.

ISSN:0010-2202    

DOI:10.1080/00102208408923755

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The concept of local, non-intrusive diagnostics in chemically reacting systems with acoustic imaging is developed. The desirability of diagnosing local, instantaneous zones in reacting flows is mentioned. A brief description is given of the state of the art in acoustics and acoustic diagnostics of chemically reacting systems. The elements of acoustic imaging through ellipsoidal mirrors are theoretically discussed. The system is chosen in these studies to be a simple, open—jet, non—premixed, turbulent flame. Methane is the fuel and enriched air is the oxidizer. A chemically reacting flow system is established at a Reynolds number (based on cold viscosity) of 50,000. A 1.5—m—diameter acoustic mirror with an f—number of 0.74 is used to map the acoustic source zone along the axis of the flame. The results are presented as the acoustic power spectra at various distances from the nozzle exit. It is seen that most of the reaction intensity is localized in a zone 4 to 8 diameters from the exit. The bulk reactions (possibly around the periphery of the larger eddies) are evenly distributed along the length of the flame. Possibilities are seen for locally diagnosing single zones in a multiple cluster of reaction zones that occur frequently in practice.

ISSN:0010-2202    

DOI:10.1080/00102208408923756

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abstract-Measurements of the polarized components of the reflectivity of a compressed propane soot pellet are presented which demonstrate that, for wavelengths in the infrared, the reflection is specular and is described by the Fresnel equations. By matching these equations to the full angular variations of the specular reflectivities, an effective refractive index of the soot/air mixture is determined at each wavelength. To deduce the refractive indices of the particles themselves, theories for the optical properties of composites are considered and a new relationship based upon the effective medium theory is introduced. The void fraction near the surface of the pellet must be known. A technique is presented for measuring this voidage by performing image analyses of scanning electronmicrographs of the pellet surface. This value of void is found to be substantially less than the bulk void. The inferred indices of the particles are seen to be sensitiveto the value of the void fraction but somewhat insensitive to the particular theory adopted for the optical properties of the soot/air mixture.

ISSN:0010-2202    

DOI:10.1080/00102208408923757

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The underfed combustion of dried bagasse in the forms of loose fibre, dense fibre, small pellets and large pellets has been investigated. The large pellets ignited rapidly on the surface and each pellet burnt slowly as an individual fuel lump, so that a bed depth greater than ∼700 mm would be necessary to reduce primary air to the stoichiometric rate. The other three forms exhibited the characteristic ignition and burn-out stages at low air rates. Their maximum combustion rates were ignition limited and decreased as the bulk density increased. Since the corresponding primary air flow rates were less than or equal to stoichiometric, their combustion at the maximum rate would be practicable. The ash from the small pellets fused into clinker, so they should only be fired, in existing bagasse boilers, as a supplement to wet bagasse at temperatures below the ash fusion temperature.

ISSN:0010-2202    

DOI:10.1080/00102208408923758

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Heats of explosion of composite propellants containing ammonium perchlorate and various acrylic polymers are measured by bomb calorimetric technique. These data have been correlated to the total reducing valencies of the stoichiometric balanced compositions.

ISSN:0010-2202    

DOI:10.1080/00102208408923759

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208408923760

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor