摘要:

The disruptive burning characteristics of isolated free droplets of binaryn-paraffin mixtures have been observed experimentally. For disruptions to occur a minimum difference in the normal boiling points of the components as well as a certain initial concentration of the more volatile component must exist. The initial concentration of the volatile component must be within a limited range defined by the relation of the homogeneous superheat limit of the mixture to the normal boiling point of the less volatile material. Disruptive burning is a result of homogeneous nucleation of the mixture somewhere within the interior of the droplet. Mass diffusion is the limiting liquid transport process which results in superheating of the droplet interior. Comparison with previous studies of micro-explosive atomization of water-in-fuel emulsions shows that the disruptive burning of a binary fuel mixture is a slower and less violent process. It is also concluded that through relieving the requirement for homogeneous nucleation, the presence of a suspending filament perturbs the droplet combustion characteristics and results in the enhancement of disruptive burning.

ISSN:0010-2202    

DOI:10.1080/00102208008952383

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An experimental study was made of the structure of the stabilizing region of plane, laminar fuel-jet flames of methane ejected parallel to the air stream. Velocity and temperature profiles were measured in detail and were analyzed to yield the distributions of the heat-flux vector and the heat-release rate throughout the stabilizing region. Results show that, a region of the higher heat-release rate appears near the flame base. This is due to combustion of a small volume of premixed gases produced as a result of fuel and air coming into direct contact. Another region of the negative heat-release rate appears on the fuel side of the flame zone. This is attributed to pyrolysis-type reactions. Towards the fuel-nozzle wall the heat-release rate decreases remarkably, still the heat-release rate in the dark space is substantial.

ISSN:0010-2202    

DOI:10.1080/00102208008952384

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The quasi-steady (QS) burning rates of interacting spherical fuel droplets are calculated by transforming the equations governing the inter-droplet fields to the Laplace equation and then solving the transformed equations by the method of images. The results of this work indicate that QS interactions can significantly reduce the droplet burning rates even for large droplet spacings. Further, the well known D2-law is found to be only approximately correct when applied to interacting droplets.

ISSN:0010-2202    

DOI:10.1080/00102208008952385

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A numerical analysis for the transient combustion of a single fuel droplet with finite rate of chemical reaction has been performed under the assumptions of spherical symmetry and constant transport properties. Evaporation curves and transient variation of the flame location, temperature profiles, and the ratio of flame to droplet radius were obtained in detail. Moreover, the effects of finiteness of chemical reaction were revealed. It was found that there exists a critical droplet diameter beneath which no stable combustion can be realized. The present results support those of earlier analytical works of Waldman, which were obtained by virtue of an asymptotic expansion method.

ISSN:0010-2202    

DOI:10.1080/00102208008952386

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The sooting behavior of laminar diffusion flames were altered by addition of diluents to the fuel flow. Fuel additives which decrease the sooting tendency had an effectiveness in order of their molar specific heat capacity; helium exhibited some exaggerated trends, probably due to its high thermal diffusivity. The effect of water vapor, carbon dioxide and sulphur dioxide in reducing the tendency to soot was purely thermal with no observable chemical interaction. Trace amounts of oxidizers and halogenated compounds increased the sooting tendency substantially. Results from tests with blended fuels and fuel-hydrogen nitrogen mixtures in which the C/H ratio and temperature were controlled revealed that C/H ratio was not a dominant parameter in the sooting tendency. These results and temperature measurements provided evidence that the sooting behavior of a diffusion flame is controlled by the initial fuel pyrolysis which is dominated by the flame temperature and the field it causes. Since accurate calculations of flame temperature in diffusion flames are difficult to make, we offer the heat production rate and heat capacity of the system as the most practical means of correlating the data. Fuel structure was the other major parameter determining the propensity to soot and it was shown that undercontrolled temperature conditions, butadiene has a far greater tendency to soot than acetylene. Overall these diffusion flame experiments have shown as well that for circular ports the sooting height, as a special case of the flame height, is strictly proportional to the volumetric fuel flow rate.

ISSN:0010-2202    

DOI:10.1080/00102208008952387

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An equation for the average departure from equilibrium of a species is derived. This equation has a source term for the production of this non-equilibrium material due to the. mixing process. In some systems the chemical kinetic rate is proportional to a simple power of the departure from equilibrium and a perturbation analysis for this quantity is possible for large Damkohler number. The lead term in (his expansion is that formed by setting the mean kinetic rate equal to the source term for the rate of production of non-equilibrium material by mixing. Two systems of interest are examined in the light of this analysis. The ozone/NOxsystem of photochemical smog is found to have a Damkohler number near unity and full integration of the departure from equilibrium equation is indicated. For hydrogen/air diffusion flames the Damkohler number is reasonably high and estimates of the departure from equilibrium and the effect on nitric oxide formation are possible.

ISSN:0010-2202    

DOI:10.1080/00102208008952388

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The effects of gas sample probes and conditioning techniques on the measurements of flame- generated NO, NO2, and CO have been further examined. (1) A low-pressure, condensation free sampling system was compared with a conventional system, which operated at higher pressure and involved H2O condensation. The conventional system demonstrated apparent losses of CO and NOx, in the range 10 to 50 percent. (2) Sampling from fuel-rich combustion and pyrolysis zones was examined. High NO2-to-NO ratios, approaching unity, were measured repeatedly in the fuel-rich pyrolysis zone of a high-intensity recirculative flame.

ISSN:0010-2202    

DOI:10.1080/00102208008952389

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The oxides of chromium, magnesium, manganese, cobalt and iron in single or in binary mixtures were used for the catalytic combustion of propane/air in an adiabatic tubular reactor. Each of the catalysts was deposited on an alumina coated honeycomb ceramic substrate. The effect of inlet temperature and equivalence ratio on the combustion efficiency, temperature and emission levels were investigated. Among the catalysts examined, the most suitable was the binary mixture of cobalt oxide and chromium oxide. Complete combustion started at an equivalence ratio of 0.196 and an inlet temperature of 580°K. The residence time was 19 ms and the NOxemission index for these conditions was 0.03 g/kg fuel. Chromium oxide alone gives a maximum of 89 percent conversion at inlet temperatures slightly higher than those used with cobalt oxide-chromium oxide catalysts.

ISSN:0010-2202    

DOI:10.1080/00102208008952390

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An analytical solution is presented for the combustion of a gaseous mixture inside a semi-infinite porous solid when the activation energy of the reaction is large. The analysis is carried out using matched asymptotic method in the same case numerically studied by Takeno and Sato (1979) i.e. in the case of a globally-adiabatic burner.

ISSN:0010-2202    

DOI:10.1080/00102208008952391

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor