摘要:

Low frequency pressure oscillations in a research ramjet combustor have been studied using an integral technique. The analysis deals with plane one-dimensional oscillations with a two-dimensional mean flowfield. The flowfield in the dump combustor consists of three parts: a flow of reactants, a region containing combustion products, and a recirculation zone. separated by a flame sheel and a dividing streamline. Each region is treated separately and matched with the other. Acoustic fields in the inlet section and in the combustion chamber are coupled at the interface to determine the complex wave number characterizing the linear stability. Good agreement with experimental results has been demonstrated.

ISSN:0010-2202    

DOI:10.1080/00102208608923839

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

–The extinction characteristics of two interacting premixed flames in counterflow configuration is investigated within the framework of large activation energy asymptotics. The major modes of interactive combustion analyzed include (a) two lean premixed flames, (b) two rich premixed flames, and (c) a lean premixed flame and a rich premixed flame separated by a diffusion flame. It is found that regions corresponding to symbiotic combustion or two lean or two rich premixed flames exist, where either flame will extinguish in the absence of the other. Furthermore. conditions for the existence of superadiabalic flames within mixtures outside of the conventional flammability limit compositions are established. Comparison of the results with the experimental data on extinction of counterflow methane-air flames show good agreement for lean but not rich mixtures; the inadequacy is believed to be caused by the assumption of unity Lewis number and identical kinetic mechamism for lean and rich flames made in the theory. Practical implications of flame interaction on combustion in inhomogeneous mixtures and the modeling of turbulent flames are discussed.

ISSN:0010-2202    

DOI:10.1080/00102208608923840

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Various methods for computing the inverse of Abel's integral equation, the underlying problem in the retrieval of temperature and concentration profiles from absorption measurements for axisymmetric spatially in homogeneous flows, have been reviewed. A nonlinear inversion method based on functional representation by cubic splines has been developed with a view to minimize the number of measurements required. Factors affecting this number, such as the choice of absorption frequencies and the phenomenon of error magnification inherent in the inversion process, have been studied. The efficacy of this inversion method has been demonstrated using absorption data synthetically generated from (previously reported) typical experimentally observed temperature and concentration profiles. The effect of pseudo-measurement error on the retrieval accuracy has been studied and the inversion method has been refined to limit error magnification in the solution process. The associated problem of low signal to noise ratio in regions with small absorption levels andpossible measures to overcome it have also been studied.

ISSN:0010-2202    

DOI:10.1080/00102208608923841

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The time dependent interaction of a laminar diffusion flame with a single plane vortexand with a stretched line vortex is examined with the aim of determining the flame configuration and the augmentation to the reactant consumption rate resulting from the interaction. Elements of the resulting curved flame sheets behave essentially as isolated flamesuntil the neighboring flame sheets become so closely spaced that they interact and consumethe intervening reactant. This process creates a core of combustion products with external isolated flame surfaces. The augmentation of the reactant consumption rate results bothfrom the local straining of the flame in its own plane and from the overall increase in flame surface area. Three examples are treated in detail. The first is the plane problem in which an initially straight flame is distorted by a vortex. In the second, the situation is similar except that the problem is expanded to three dimensions and the vortex line is being stretched along its own axis. Finally, the effects of the density change resulting from the heat release are examined.

ISSN:0010-2202    

DOI:10.1080/00102208608923842

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Abstrart-Experiments have been conducted with a homogeneous charge spark ignition engine fitted with a transparent dual (or divided) chamber cylinder head. High-speed cine photography has been used to chart flame progress. The rate of burning and performance of the engine have been determined for a range of pre-chamber sizes and pre-chamher to main-chamber interconnecting orifice sizes. A comparative series of experiments has been made with the same engine equipped wilh a disc-shaped single chamber cylinder head. Combustion proved faster with the dual chamber geometry; the rare of combustion has been shown to increase in accord with the calculated maximum orifice flow velocity during compression and the associated degree of turbulence generated. The range of turbulence intensity generated by the flow through the orifice is likely to have been greater than that noted in previous single chamber studies. A levelling OK in burning speed at very high turbulence levels, previously observed in stirred bomb studies, was encountered.

ISSN:0010-2202    

DOI:10.1080/00102208608923843

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The spread of a line fire through wildland fuel is modeled for situations in whichunignited fuel is heated by radiation and cooled by radiation and convection. The fuel bed is idealized as a continuum in a homogeneous layer composed of uniformly distributed, approximately convex particles that are randomly oriented, thermally thin, and radiometrically black. The model is implemented as an algorithm that finds the temperature of the fuel particles every-where in the unignited bed and solves simultaneously for the rate of fire spread and the shape o f the surface (the ignition interface) upon which the particles are ignited. This algorithm is an extension of one presented earlier that neglects particle cooling by convection. Results predicted by the revised model are compared to measurements made on experimental fires. The ignition interface shape predicted for the experimental fires agrees reasonably well with measuremenls when two free parameters have values chosen so as to yield the measured rate of fire spread.

ISSN:0010-2202    

DOI:10.1080/00102208608923844

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor