摘要:

Neutral species (molecules, atoms and radicals) present in rich C2H2/O2premixed flat flame stabilized under reduced pressure (20 torrs) have been analyzed by the coupled molecular beam-mass spectrometry technique. To investigate whether particular variations are observed at the sooting limit (φ = 2.1) six flames of equivalence ratio respectively equal to 1.8, 2.0, 2.1, 2.2, 2.6 and 3.0 have been studied. Results have been mainly used to compare the role played by polyacetylenic hydrocarbons and polycyclic aromatic hydrocarbons (PAH) in the mechanism of soot formation. Main features of the profiles of mole fraction and mass fraction flux versus distance to the burner show that polyacetylenics cannot be considered as active intermediates. On the other hand a strong reactivity is observed at the boundary between oxidation and soot formation zones for PAH. If PAH play an active role in soot formation, it is worth knowing the nature of the species leading to the production of the first aromatic rings. For (his purpose variation of the profiles of mass fraction flux for species containing one to six carbon atoms has been examined as well as the role played by deshydrogenation reactions. Results suggest that C4H4may play a major role in the first step of the mechanism of soot formation.

ISSN:0010-2202    

DOI:10.1080/00102208408923818

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208408923817

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The lift-off heights and visible-flame lengths of jet diffusion flames in still air have been determined for hydrogen, propane, methane and ethylene.

ISSN:0010-2202    

DOI:10.1080/00102208408923819

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In the present work the effect of the wind on a fuel storage tank fire is studied. A brief theoretical analysis shows the evolution of the dynamic parameters that govern the flow (Archimedes number, Froude number and Reynolds number) in function of the wind velocity.

ISSN:0010-2202    

DOI:10.1080/00102208408923820

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A necessary element in the development of predictive procedures for the spread of fires in enclosures is a satisfactory description of the turbulent source. The absence of an established experimental data base inhibits the necessary model development specific to fires. Their buoyant, low source momentum mixing characteristics are quite different from the more widely investigated jet flames and require the application of both particular models and measurement techniques. This paper describes velocity measurements in and around a buoyant flame on a 25 cm diameter porous refractory burner, using LDA with photon correlation signal processing. This technique makes all parts of the flame accessible wilhout recourse to any artificial seeding. The air entrainment region, in which velocities are very low and susceptible to disturbance, is readily, and perhaps uniquely, accessible. Closer to the flame. the large scale inhomogeneities which accompany buoyant flame motion pose important questions of seeding bias as the LDA volume is intermittently engulfed first by hot fuel/product (and therefore higher velocities) and then by cooler ambient air. LDA systems relying on seeding of the fuel stream are particularly susceptible to bias in this regime. Conditional sampling of the velocity, using a thermocouple to trigger the acquisition of data, reveals the scale of differences between these distinctive pockets. On the centre-line, measurements with a variety of techniques are compared and the natural conditioning of the present study, associated with soot concentration and particle size, is used as a diagnostic in an attempt to consolidate all the data.

ISSN:0010-2202    

DOI:10.1080/00102208408923821

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In order to contribute to the modelling of room fires, experimental results are presented concerning turbulent diffusion flames obtained with a 30 cm diameter burner and corresponding to initial Froude number F in the range 2 × 10–6< F < 1.2 × 10–5, and calorific powersQin the range 16 kW <Q< 38 kW. The results concern main species mole fractions, temperature and flow velocity. The spectral analysis of the signal obtained by laser velocimetry shows that the flow is periodic or quasi-periodic in the lower part of the flame, where the quasi-totality of the combustion is achieved. Although thek-ε-gmodels imply a fully turbulent flow, the comparison of our experimental results with predictions based on the models developed by F. Tamanini shows that the Wallburn model gives a satisfactory approximation of the mean velocity distribution along the flame axis. However these models underestimate the lateral expansion of the flame.

ISSN:0010-2202    

DOI:10.1080/00102208408923822

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This work is connected to the modelling of the fire growth in a room, for which the knowledge of the radiation emitted by the flames to surrounding combustible elements is significant.Working on propane diffusion flames rising above the surface of a 0.3 m diameter circular burner, we have established the radiative flux distributions in vertical planes facing the fire.The radiative fraction χ has been measured; χ increases first with fuel flow rate and then reaches anasymptolic value. Starting from measured temperature distributions, the radiation fluxes emitted by the nonisothermal flames have been computed and compared with values obtained making constant flame properties assumption, and with experimental values.

ISSN:0010-2202    

DOI:10.1080/00102208408923823

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

It is recognized that small scale test methods are unable to predict the fire growth potential of interior finish materials. This has led to an interest in the use of full scale room fire tests. One of the reasons for the effectiveness of these full scale experiments is their ability to reproduce a turbulence similar to the one expected under actual fire conditions. This paper describes some of the flame morphologies observed in full scale fire experiments, and their origins are ascribed to certain turbulent conditions. The corner placement of the ignition source is shown to produce a more severe exposure to the walls than a side wall exposure. The spread of fire to the ceiling is shown to follow the corner between the two walls, and the subsequent flame spread at the ceiling is in the narrow region at the intersection between the walls and the ceiling, termed in this paper the "T" pattern flame morphology. In cases where the walls and/or the ceiling are combustible, it has been observed that the "T" pattern begins to burn first, and it is only afler this "T" burning is established that the remainder of the ceiling is ignited and begins to burn. A special flame morphology is shown which appears to be important to the flame spread under the ceiling of a compartment. A mechanism is presented lo explain the observed morphology in which a vortex structure originally formed on one wall is interrupted by fluctuations in the buoyant plume at the corner, is captured by the flow on the other wall, and is then swept along with the flow at that wall. The significance of this turbulence is discussed, and it is suggested that it be taken into account when developing compartment fire models.

ISSN:0010-2202    

DOI:10.1080/00102208408923824

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Abstract– Measurements of stabilization heights in lifted turbulent methane-air jet diffusion flames are performed in order to test a theory on local quenching of dilfusion flamelets. The global residence time (d/u0the nozzle diameter, u0, the nozzle exit velocity) is scaled with Zqthe instantaneous scalar dissipation rate at quenching. This quantity had been identified before to be charncteristic for the extinction of diffusion flamelets. Values for Zg, are deduced from measurements of laminar diffusion flames in a counter flow geometry. The scaling is performed for constant values of Zqthe conserved scalar variable at sioichiometric conditions. Both the fuel and the air stream are diluted to obtain constant values of Zq. Scaling with Zqmakes the curves for different residence times collapse into one curve with however, considerable experimental scatter. From this is concluded that Zq, is the essential kinetic parameter describing quenching effects in turbulent diffusion flames.

ISSN:0010-2202    

DOI:10.1080/00102208408923825

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor