摘要:

The dilution of a homogeneous combustible mixture with products of combustion has proven to be a successful method of reducing the oxides of nitrogen produced by a combustion process. The Exhaust Gas Recirculation (EGR) affects the flame velocity, ignition energy, and quenching behavior. An experimental program has been conducted to determine the effects of EGR on these fundamental aspects of a turbulent methane/air flame in a constant volume bomb. Data are presented showing that the decrease in flame velocity caused by the EGR can to some extent be compensated for by an increase in the turbulence intensity at a price of increased ignition difficulty. The effect of the EGR, as determined from both heat transfer and ionization measurements, is to increase the single-wall quenching distance.

ISSN:0010-2202    

DOI:10.1080/00102208008952392

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A one-dimensional model has been developed for pulverized coal combustors and gasifiers. The model describes the response of a coal particle system to its thermal, chemical and physical environment. Moisture vaporization, coal devolatilization, heterogeneous char oxidation, gas particle interchange, radiation, gas phase oxidation, primary and secondary stream mixing, and heat losses are considered. A predictor-corrector solution technique was used to solve the ordinary non-linear differential equations. Several combustor and gasifier predictions are shown. The model predictions are compared with experimental data. The effects of particle size and distribution are shown to be particularly important. Significant rate controlling processes include initial particle heat-up and char surface reaction.

ISSN:0010-2202    

DOI:10.1080/00102208008952393

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The effect of different cresols (o, m, p), resorcinol and pyrogallol in the presence and absence of lead stearate on the burning rates of cast double base propellants has been studied in the 35−140 kg/cm2pressure range. While their effect is not significant without lead stearate, these phenolic compounds increased burning rates in the presence of lead stearate. Their mode of action is explained on the basis of differential thermal analysis data.

ISSN:0010-2202    

DOI:10.1080/00102208008952394

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The American Society of Testing and Materials test E84 is widely employed in North America to characterize the rate of flame spread along samples of material proposed for use in construction of buildings; by this test, materials, in part, are qualified with respect to fire safety for classes of application. In this ten-minute-duration test, an 8 meter slab of the material comprises the ceiling of a sealed duct (termed a Steiner tunnel) through which hot vitiated air (up to about 1150 K) flows after time zero at about 1.2 m/s. Materials are rated according to the distance from the leading edge that the wind-aided flame propagates (or, alternatively for samples that become totally involved, by the elapsed time to flameover at the downwind end). An unsteady two-spatial-dimensional model of this test has been undertaken, as a first step toward the goal of anticipating behavior of a sample from knowledge of its chemical and physical properties. In the formulation, at any fixed position along the sample, as time increases, the sample is heated, by conduction and radiation, from its initial temperature to its pyrolysis temperature, but any further heat transfer from the gas phase to the sample (not conducted into the interior of the sample) contributes to gasification at that constant “pyrolysis temperature.” The gas-phase heat transferred to the sample is furnished by the initial vitiated-air enthalpy, supplemented by chemical exothermicity from a homogeneous diffusion flame at which fuel vapor pyrolyzed from the sample reacts with oxygen from the vitiated air stream. An isobaric Shvab-Zeldovich formulation of heat and species conservation [with treatment of the flame after Burke and Schumann; of convective transport, after Oseen, but with a nonlinear expression to account adequately for interphase mass transfer; and of diffusive transport, after Prandtl] proves amenable to an approach believed to be of general interest in Stefan problems with a split-type boundary condition. Split-type boundary condition here alludes to the fact that, at the two-phase interface, preheating boundary conditions (i.e., continuity of temperature and of heat flux) apply downwind of the pyrolysis front, but mass-transfer conditions (i.e., sublimation at a known, constant temperature) apply upwind of the pyrolysis front; the translation of the front with time must be found as part of the solution. The approach entails the use of the Fourier transform to integrate out the dependence on the coordinate transverse to the two-phase interface; with the parabolic nature of the full partial differential operator so removed, one may use method-of-characteristics solution in the interfacial plane for the Volterra integral equations derived from the hyperbolic suboperator. From knowledge of the dependence on time and stream-wise co-ordinate of the solution in the interfacial plane, the solution may be extended readily off the interfacial plane. The model presented here retains radiative transfer in simplistic form; in particular, the radiative cooling of the ambient hot air stream down the tunnel is included. Only by including such cooling may the model recover a result occasionally observed for a fire-retardant-treated foamed-plastic sample: visible flame propagates rapidly a finite distance along the sample, and then, abruptly, goes no further.

ISSN:0010-2202    

DOI:10.1080/00102208008952395

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An alternative derivation of the integral equations introduced in the preceding paper is presented. The method avoids the use of transform techniques. Instead, the equations governing the evolution of the gas phase dependent variables are transformed into the heat conduction equation. The introduction of the Greens function corresponding to a one dimensional heat source then leads to the desired result.

ISSN:0010-2202    

DOI:10.1080/00102208008952396

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Three effects found during the measurement of oxides of nitrogen produced by liquid fuel diffusion flames are reported. In each experiment a diffusion flame at one atmosphere pressure was formed around a horizontal fuel wetted cylinder. In the first experiment a porous metal cylinder of 5.2 mm diameter was wetted by normal heptane and placed in a low velocity stream of ambient air. Soot escaping from the turbulent wake of the diffusion flame was deposited on the surfaces of a large collection system located above the flame. This collection system drew in all of the flame products plus some entrained ambient air. The soot was found to give off NO slowly at ambient temperature and more rapidly when healed. The NO from the soot amounted to 20 percent of the gas phase NO produced by the flame. In the second experiment, a quartz microprobe was used to take gas samples along a horizontal line perpendicular to the cylinder axis. The cause of high NO leadings indicated by the chemiluminescent analyzer for samples taken near the liquid surface was traced to sensitivity of the analyzer to pyrolysis products. In the third experiment, the fuel wetted surface was a horizontal moving thread. It was found that the presence of unburned hydrocarbons in the air around the flame promoted the conversion of NO to NO2without changing the total amount of NOxproduced.

ISSN:0010-2202    

DOI:10.1080/00102208008952397

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Inhomogeneities produced in an initially homogeneous liquid layer by mass transfer of several components may lead to a potentially detonable local concentration even though the average concentration of the explosive component in the system remains below the detonation limit. Equations are developed for a three-component system in which one component preferentially vaporizes from solution and a second component is condensed. The equations are applied to the hydrazine-hydrazine nitrate-water system. Local concentrations which exceed the safe limit of hydrazine nitrate are found. In comparable situations, additional tests should be performed which take this inhomogeneity into account before the system is accepted as safe from accidental detonation.

ISSN:0010-2202    

DOI:10.1080/00102208008952398

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor