摘要:

—Using a Bunsen-type burner in which the name temperature was controlled by nitrogen addition, the tendency of hydrocarbon fuels to form soot has been determined systematically. The effective sooting equivalence ratio reported is based on the stoichiometric relation in which the carbon and hydrogen in the fuel are converted to carbon monoxide and water. respectively, rather than the conventional equivalence ratio or the C/O ratio. The temperature effect is clearly shown by plotting the log of the effective equivalence ratio versus the reciprocal of the (adiabatic) flame temperature, and this dependency is similar for all fuels examined and is relatively weak. At a given flame temperature, an increase in either the number of carbon atoms or the C/H ratio in the fuel molecule increases the tendency to soot. These effects are attributed to the increased pyrolysis rate and the decreased oxidative attack, respectively. No significant effects are found with regard to the structure of the fuel molecule. The sooting tendency at a fixed temperature correlates extremely well with the "number of C-C bonds" or the total C-C bond strength in the molecule.

ISSN:0010-2202    

DOI:10.1080/00102208408923743

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The classical diffusion flame model of Burke and Schumann is extended to include the effects of both streamwise and preferential diffusion. The study first identifies a Lewis-number-weighted coupling function as the proper one to usc in formulations involving non-unity Lewis numbers. A perturbation technique is then developed for the realistic situation of ncar-unity Lewis number flows. Results show that, depending on the effective Lewis numbers of fuel and oxidizer, the flame temperature may vary either monotonically or non-monotonically along the flame sheet, and thereby suggesting the possibilities of tip opening, and tip intensification, as well as partial and complete flame blow-off.

ISSN:0010-2202    

DOI:10.1080/00102208408923744

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The recently introduced concept of percolate combustion motivates a refinement of the internal group combustion model analyzed by Chiu and coworkers. The continuous flame sheet separating com busting and non-combusting regions, regarded in the latter model as occupying a zone of negligible thickness, is here regarded as a highly convoluted surface occupying a zone of finite thickness, the "percolate combustion" zone. A simple model is employed to estimate the fraction of the combusting region that is within the percolate combustion zone. This fraction is estimated to be significant for internal group combustion regimes of practical interest. It is proposed that more detailed spray combustion models can incorporate percolation effects by modification of the transport equations and the matching conditions. Possible impacts of such modifications, including practical consequences of percolation effects, are discussed.

ISSN:0010-2202    

DOI:10.1080/00102208408923745

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Calculations are performed for non-premixed, chemically reacting axisymmetric and plane jets involving NO and O3. The jet carries NO diluted with N2into the stagnant surrounding containing traces of O3in the carrier gas N2. The concentrations of the reactants and products are determined from Monte Carlo solutions of the joint PDF equation of two scalars (Shvab-Zeldovich variables). The hydrodynamics are determined from the continuity equation, time averaged momentum equations and a two-equation model for turbulence. In order to compare the Monte Carlo calculations and to estimate the effects of concentration fluctuations on the reaction rate, finite-difference calculations were made on the averaged transport equations for the same two Shvab-Zeldovich variables, with neglect of second-order effects on the reaction rate. It is noted that for the passive scalar (first Shvab-Zeldovich variable) mean transport calculations are advantageous, where the joint PDF formulation has the advantage of closing the source term for the reactive scalar (second Shvab-Zeldovieh variable). This paper contains mean velocity profiles, turbulence scales, the mean and all the second-order moments of scalars calculated from joint PDF formulation.

ISSN:0010-2202    

DOI:10.1080/00102208408923746

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Flame spread aspect along the pool surface of gelled (O/W emulsified) II-octane with high internal phase ratio was investigated from the viewpoint of spilled-fuel fire prevention. The temperature field in the vicinity of the spreading flame front was measured by thermocouples (chromel-alurnel, 0.1 mm dia.) and Mach-Zehnder interferometry, and temperature histories on the unburned surface and in the gas phase adjacent to the surface were shown.From the measured results, the mode of heat transfer from the spreading flame to the unburned pool surface was estimated. The dependence of flame spread velocity on the initial temperature of gelled η-octane and on the oil content in gel (internal phase ratio of O/W emulsion) were also investigated.

ISSN:0010-2202    

DOI:10.1080/00102208408923747

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208408923748

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor