摘要:

A residential airtight woodstove was used to burn oak cordwood at dry-basis moisture contents of 12 and 50 percent. The mass-time history of the stove's charge was determined using an electronic scale. The products of combustion, which include copious quantities of condensed hydrocarbons, volatile hydrocarbons, and carbon monoxide, were analyzed to determine the oxygen/carbon and hydrogen/carbon ratios of the instantaneously gasified fuel. These ratios have been nondimensionalized to give two parameters which indicate when oxygen and hydrogen are preferentially (compared to carbon) released from the fuel as it is gasified during the burn cycle. To a first approximation these parameters vary in the same way as a function of time, giving indication that for the type of fuel and stove design studied much of the hot-to-hot burn cycle may be crudely modeled as a drying process combined with uniform burning of dry wood. However, it appears that a more sophisticated model is required if meaningful instantaneous efficiencies are to be measured.

ISSN:0010-2202    

DOI:10.1080/00102208608923913

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In the pdf approach to turbulent combustion the molecular diffusion is to be modeled. In recent years, several authors have employed the Curl model (Curl, 1963) for closure. A modified version of the Curl model has been introduced by Pope (1982b). The modified model contains an unspecified function A∥α) [cf. Eq. (la)] which has been defined in the context of Monte-Carlo simulation. The paper Clarifies the physical meaning of this function by relating it to the physics of the initial phase of mixing of an inert scalar in homogeneous turbulence. A relationship is established between the modified Curl model and the linear mean square estimation closure introduced by Dopazo and O'Brien (1976). The asymptotic behavior of the pdf is discussed.

ISSN:0010-2202    

DOI:10.1080/00102208608923914

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The oxidation of ammonia during the combustion of ethane in a thermally stabilized burner (TS8) was studied in order to test the independence of the mechanism of fuel-NOxproduction on the type of nitrogen in the fuel. In a previous investigation of fuel-NOxproduction in the TSB using carbon-containing fuel-nitrogen compounds, nitrogen was found to be converted almost entirely to NOxat equivalence ratios near stoichiometric for post-flame residence times greater than 1.5 ms. This result was reproduced by the current study using ammonia as the fuel-nitrogen source. For fuel-rich stoichiometrics, NOxproduction from the ammonia was found to be a stronger function of post-flame residence time, with the peak in the concentration of NOxoccurring at about 1.5-2 ms after the flame front, and a moderate reduction thereafter. These results were confirmed theoretically using a plug-flow model for the TSB coupled with reaction mechanisms for ethane and ammonia oxidation. The fractional"conversion of ammonia to NOxas a function of equivalence ratio was otherwise found to compare closely with the prior results for complex carbon-bearing nitrogen additives.

ISSN:0010-2202    

DOI:10.1080/00102208608923915

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Radiation is important in all but the smallest flames. This paper describes a model designed to predict the local effects of radiation in flames which may be turbulent and burn at a finite rate. Such local effects are important because of the strongly nonlinear dependence of many properties on temperature. An accurate estimate of average properties may be made through the use of existing stochastic chemistry models in adiabalic processes. The model described in this paper is required to determine the divergence of radiant heat flux in random mixtures generated in stochastic processes where significant radiation is expected. Because there is an ensemble of such mixtures at each point in the flame, realizations are constructed by selecting one mixture at random from each point. Local radiative properties are determined and a governing equation is then solved over each realization. The divergence term is then calculated and the energy equation solved with the correct departure from adiabalic conditions for each random mixture. The model described in this paper has been successfully incorporated into a numerical model of turbulent diffusion flames which is capable of predicting the effect of the discharge diamelcr of the gas jet ranging from the laboratory to the industrial scale.

ISSN:0010-2202    

DOI:10.1080/00102208608923916

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Acoustic emission spectra have been obtained for non-premixed turbulent combustion from two small-diameter laboratory gas burners, two commercial gas burners, and a large gas burner in the firebox of a Babcock-Wilcox Boiler (50,000 lb steam/hr). The changes in burner size and firing rate represent changes in Reynolds number, and changes in air/fuel ratio represent departure from stoichiometric proportions. The combustion efficiency was measured independently through gas analysis. The acoustic spectra obtained from the various burners exhibit a persistent shape over the Reynolds number range of 8,200-82,000. The spectra were analyzed for identification of apredictablefrequency domain that is most responsive to, and readily correlated with, combustion efficiency. A simple parameter (consisting of the ratio of the average acoustic power output in the most responsive frequency bandwidth to the acoustic power level of the loudest frequency) is proposed, whose value increases significantly and unmistakably as combustion efficiency approaches 100 percent. The dependence of the most responsive frequency domain on the various Reynolds numbers associated with turbulent jets is discussed.

ISSN:0010-2202    

DOI:10.1080/00102208608923917

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Zeldovich-Li[nbar]án model, originally proposed by Zeldovich and analyzed asymptotically by Li[nbar]án, has recently been analyzed by Joulinet al.(1985) under a particular distinguished limit. The limit considered by Joulinet al.only has solutions with algebraically small concentrations of radicals in the neighborhood of a particular flame temperature. For flame temperatures above this, the concentration of radicals becomes 0(1) whereas for flame temperatures below the pivotal value the concentration of radicals become exponentially small. Joulinet al.do not discuss this aspect of the problem but it is demonstrated here.

ISSN:0010-2202    

DOI:10.1080/00102208608923918

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In an earlier analysis, matched asymptotic expansions in a parameter representing the ratio of the energy required for liquid heating to that required for liquid vaporization were applied to slurry-droplet combustion for solid loadings sufficiently large that the droplet diameter remains approximately constant. Here that analysis is extended to smaller solid loadings for which the droplet diameter decreases with time during part of the combustion history, and implications concerning burning of pure liquid droplets are drawn.

ISSN:0010-2202    

DOI:10.1080/00102208608923919

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This paper stresses the point that, contrary to common notion, temperature gradients do exist in pulverized coal particles, and that such gradients may or may not be important, depending on the coal thermal properties. Such properties are not routinely measured and are not well documented. In general a particle heats up by an inward moving “heat wave” which is followed by a “pyrolysis wave”. The pyrolysis rate is a function of time and position as described by an “onion peel” model.

ISSN:0010-2202    

DOI:10.1080/00102208608923920

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The full problem of flame stability, in which fluid mechanics is properly taken into account for all disturbance wavelengths, is examined further. Previously obtained results are extended to include the effects of gravity and non-adiabaticity.

ISSN:0010-2202    

DOI:10.1080/00102208608923921

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor