摘要:

Experiments were made in open coaxial jets of a Mach 1.26 oxidizer flow and a subsonic fuel flow; the ratio of the mass flux of the fuel flow to the oxidizer flow was 0.094; and city gas was used as the fuel. The inner fuel jet had an initial diameter of 13 mm and the outer oxidizer jet 36.7 mm; the oxidizer had a static temperature of 1350K and an oxygen mole fraction of 0.063. Pitot pressure, static pressure, total temperature, and species concentrations were measured in the combustion field. It was found that the flow pattern downstream of the fuel injector was like a wake having a recirculation zone in it. The flame was formed at the edge of the wake. The luminous zone was thin down to the end of the recirculation zone, and downstream of the recirculation zone the luminous zone rapidly thickened.

ISSN:0010-2202    

DOI:10.1080/00102207708946788

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The decomposition rate of NO on the alumina surface is obtained by two different experimental methods in the temperature region of 920-1220°K. One is carried out by a laminar convective mass transfer experiment of the fuel lean combustion gas including various quantities of NO in a horizontal alumina pipe. The other is by an experiment of introducing such mixed gases as Ar-NO, Ar-NO-CO and Ar-NO-H2flowing through a packed bed of alumina pebbles. First, the decomposition rate of NO is proved to be of zeroth order on the NO concentration when it is larger than about 300 ppm. However, in the case of NO concentration lower than about 300 ppm, all the reaction rates come to depend on the NO concentration. Secondly, the effect of the reducing species such as CO and H2on the decomposition rate was studied by adding CO and H2and, depending on the amount of CO and H2included, the rate was seen to increase up to 3 to 12 times that in the case without these reducing species.

ISSN:0010-2202    

DOI:10.1080/00102207708946789

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102207708946790

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

A similarity parameter has been obtained for a confined turbulent jet system of constant cross section for which the nozzle fluid and the surrounding fluid have different densities. This parameter was derived from the time smoothed equations of motion with certain simplifying assumptions. Velocity, temperature and tracer concentration profiles were measured on such a system with the similarity parameter, called the non-isothermal Craya-Curtet number, varied over a range of 0.22 to 1.2. The experimental data were correlated with the similarity parameter in a manner which supports its validity.

ISSN:0010-2202    

DOI:10.1080/00102207708946791

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

In an earlier paper an asymptotic analysis was presented for the radiant ignition of a solid fuel that gasifies endothermically then reacts exothermically in the gas phase through a one-step Arrhenius process. The theory was restricted to surface absorption of the incoming radiation and to ignitions occurring during the stage of transport-controlled gasification which follows the stage of transition to gasification. These two restrictions are removed in the present paper. Emphasis is placed on determining the ignition time, defined as the interval between initiation of irradiation and thermal runaway. It is shown that if the gas is sufficiently reactive then ignition can occur early in the stage of transition to gasification and that decreasing the absorptivity of the solid increases the ignition time. Comparisons are made with results of earlier numerical integrations, demonstrating the existence of regimes in which the ignition time depends strongly on the ignition criterion adopted. Graphs are given containing results of a parametric study for the ignition time.

ISSN:0010-2202    

DOI:10.1080/00102207708946792

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

The influence on the self-ignition of single fuel droplets of ambient temperature and oxygen concentration, droplet relative velocity, droplet size, and fuel type was investigated both experimentally and theoretically. Using a unique droplet combustion experimental system, measurements of droplet ignition delay times were obtained for two pure fuels having widely different properties (furfuryl alcohol and butyl alcohol) and two different droplet diameters (200μ and 300μ nominal diameter) for representative droplet combustion conditions. A mathematical model describing the development of profiles for fuel vapor, temperature, and oxygen in the boundary layer surrounding a single fuel droplet moving relative to a hot oxidizing atmosphere was used to correlate the observed ignition delay times. Ignition delay times are found to increase substantially with decreasing ambient temperature and to a somewhat lesser degree with increasing droplet diameter and decreasing fuel volatility. A modest tendency for decreasing ignition delay times with increasing droplet relative velocity is noted, but this effect of relative velocity diminishes rapidly with increasing fuel volatility or decreasing droplet size. While the measured effect of ambient oxygen weight fraction on ignition delay times is shown to be negligible, the theoretical correlation shows a decrease in ignition times with decreasing oxygen weight fraction. This lack of agreement is ascribed to an oversimplification in the ignition criterion used in the mathematical model. Differences in predicted ignition delay times using mathematical models based on uniform and nonuniform internal droplet heating are found to be so small that no conclusions can be made regarding the actual mode of droplet heating during the preignition period.

ISSN:0010-2202    

DOI:10.1080/00102207708946793

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

摘要:

This paper presents a model describing the flow field due to a two-dimensional infinitely long heat source in a stably-stratified atmosphere with a uniform wind cross-flow. The governing equation which is valid for any wind shear is non-linear in its general form and is solved for uniform flow only. The energy equation is not solved but a “source” function is assumed. The results of this model exhibit some of the observed mass fire characteristics such as the inflow window, the pinch effect, the upstream downdraft and a strong dynamic convection column. Blocking and the formation of eddies are shown to be the most important characteristics of the onset of mass fire conditions.

ISSN:0010-2202    

DOI:10.1080/00102207708946794

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102207708946795

出版商:Taylor & Francis Group    

年代:1977

数据来源: Taylor