摘要:

A device for monitoring the maximum temperature in an extended region was applied to the control of combustion for regeneration of a diesel particulate filter. The device's main objective is to monitor internal thermal radiation of an optically transparent rod probe at its end. In both the experiments using carbon black and real diesel exhaust particulates, a stable regeneration process was realized by controlling the flow rate of air needed for combustion according to the light intensity from the probe.

ISSN:0010-2202    

DOI:10.1080/00102209108951726

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Temperature and radiation properties of 1-8 MW heat release rate methane/air jet diffusion flames without and with the addition of liquid water suppressant to the fuel stream are studied. The analysis includes an existing parabolic flow solver, in conjunction with the locally homogeneous flow approximation and the laminar flamelet concept. State relationships for methane + liquid water mixtures are calculated from species concentration measurements for methane flames without water added. The analyses are compared with previously published data. Tests for flames without water addition show the applicability of the analyses to the present flame scales. The results for flames with water addition indicate that finite rates of evaporation and separated flow effects need to be considered for accurate predictions at high water loading.

ISSN:0010-2202    

DOI:10.1080/00102209108951727

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Metal fibre burners exhibit stable radiant surface combustion over a range of thermal inputs. The model outlined in this report explains why stable surface combustion is possible for some values of thermal input but not for others. It also identifies parameters which will affect burner operation and provides temperature profiles through the burner material which cannot be obtained experimentally. The model takes account of heat transfer by conduction, convection and radiation within the burner, combustion near the burner surface and radiation from the surface. The method of activation energy asymplotics is used to simplify the equations which result.

ISSN:0010-2202    

DOI:10.1080/00102209108951728

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The mechanisms responsible for driving and damping of pressure oscillations in a laboratory combustor have been investigated. The chamber contains a turbulent methane/hydrogen/air premixed flame stabilized behind a rearward-facing step. Shadowgraph cinematography reveals the shedding of large vortices from the step at frequencies of the system acoustic modes. Variations in the fuel equivalence ratio and the mean flow speed result in a wide variety of nonlinear dynamical behavior. Typically, large cycle-to-cycle variations are observed such that energy may be added or subtracted over one cycle of oscillation but zero net energy change occurs many cycles of oscillation. A quantitative version of Rayleigh's Criterion is constructed by using the cross-spectral-density of the measured flame radiation and pressure. The results under one set of operating conditions show that large driving near the flameholder is balanced by equally large damping further downstream. A second set of conditions results in large energy addition to an acoustic mode balanced by attenuation at the mode subharmonic.

ISSN:0010-2202    

DOI:10.1080/00102209108951729

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The oxidation of H-pentane is studied in a jet-stirred flow reactor in the temperature range 950-1050K at atmospheric pressure for a wide range of fuel-oxygen equivalence ratios (0.2 to 2.0). A chemical kinetic reaction mechanism developed from previous studies on smaller hydrocarbons and extended to C5species is used to reproduce the experimental data. Good agreement between computed and measured concentrations of major chemical species is obtained for the entire range of experimental conditions. The major reaction paths for H-pentane consumption and for the formation of the main products are identified.

ISSN:0010-2202    

DOI:10.1080/00102209108951730

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Laboratory-scale experiments on wind-aided firespread across an array of very-small-diameter (1.3-4.4-mm), discrete fuel elements were carried out in a specially designed wind tunnel. The rate of firespread, ty, is inferred from the output of streamwise-disiributed, near-bed-surface thermocouples. The fuel consists of an array of identical, regularly arranged, wooden, toothpick-like Tuel elements, positioned upright in shallow holes drilled in a ceramic substrate. Adoption of this well-defined fuel bed facilitates repetition. Extensive testing suggests that νy∼ (U/m)1/2over a wide range of the uniform ambient wind speed U and the fuel-mass distribution m (fuel, per unit planform area of the bed, consumed with firefront passage). The effects on the firespread rate of other parameters investigated and reported include the type of wood species; fuel-element length; fuel-element diameter; fuel-bed width, including streamwise-varyjng width; enhanced moisture content of the substratum and/or fuel; small-scale variability within macroscop-ically identical fuel beds; and mixed beds (beds with combustible elements of multiple thicknesses; beds with thermoplastics or inert material in addition !o wooden elements). The firespread rates reported here are compared with the results of previous investigators.

ISSN:0010-2202    

DOI:10.1080/00102209108951731

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A theoretical analysis is developed to study the downward flame spread over the thermally-thin solid fuel vertically in the gravitational field. The combustion model is basically similar to that of Chen (1990). The effect of Damkohler number (Da), as a function of gravity level (g), is under investigation. Beyond the blowoff limit, the flame spread rate is found to be proportional to (g)−1/3. A combination of the isotherm and velocity vector distributions in gas phase and the solid fuel pyrolysis are presented together to illustrate flame structures at normal gravity. Subject to the same Da, the flame is weaker than that in forced convection. Within the elevated gravity domain of experiment, the computed flame spread rate agree very well with the measurements obtained by Altenkirch el at. (1980).

ISSN:0010-2202    

DOI:10.1080/00102209108951732

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Swan band emission of C2, which had been produced and excited (d3πg← u3πuΔv = 0) by focused, tunable, visible laser radiation, was studied in sooting ethylene flames. The C2signal from the sooting regions of the flames was found to be proportional to the measured volume fractions of soot, indicating laser-vaporized soot to be the source of the signal, and as such it can be used as a diagnostic tool for point measurements of the volume fraction of soot. C2emission was detected for all incident wavelengths between 485 and 540 nm, with a C2, signal 1-2 orders of magnitude higher when the wavelength was tuned to a C2resonance than when tuned to a wavelength between the Swan bands. High concentrations of laser-produced C2, and emission from C2, Swan bands can, through interference effects, limit the applicability of laser diagnostic techniques to sooting flames.

ISSN:0010-2202    

DOI:10.1080/00102209108951733

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An efficient method for the formation of the numerical Jacobian in combustion codes has been applied to premixed laminar and counterflow diffusion flames. The improvements are portable to similar codes for treating ignition, two-dimensional flames and the general class of reactive-diffusive processes. Execution times were reduced by a factor of seven with no decrease in accuracy, for a mechanism containing 46 species and 213 reactions, when compared with the starting form of the premixed flame code developed at Sandia Laboratories (Smooke, 1982).

ISSN:0010-2202    

DOI:10.1080/00102209108951734

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The concept of the combustion rate in the regime where the flame fluctuations result in the ejection of pockets of unburned gas is discussed.

ISSN:0010-2202    

DOI:10.1080/00102209108951735

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor