Showing papers on "Diffusion flame published in 1972"
TL;DR: In this paper, the yield of nitric oxide from small additions of various nitrogen compounds was measured in premixed ethylene flames of mixture strengch= 0.9 to 2.0 and of temperature = 1860 to 2250°K.
144 citations
TL;DR: In this article, the authors measured the burning velocity in the central stream-tube of a button-shaped flame with the particle track method and compared it with data from cone-shaped flames.
101 citations
TL;DR: In this paper, a computer simulation of an opposed-jet methane/oxygen/nitrogen diffusion flame is presented which includes a realistic set of chemical reactions and realistic transport properties.
36 citations
TL;DR: In this article, an experimental investigation of stable laminar ethylene and propylene diffusion flames burning on a nozzle in weightlessness was performed at the NASA-Lewis 2.2 Second Drop Tower.
Abstract: An experimental investigation of stable laminar ethylene and propylene diffusion flames burning on a nozzle in weightlessness was performed at the NASA-Lewis 2.2 Second Drop Tower. For a range of low flow conditions, visual evidence indicated that the flames reaction zone was burning over a wide range of combustion rates; however, for the purposes of correlating flame length the stoichiometric burning rate appeared adequate. It was found that if Re is the ambient pure fuel Reynolds number based on nozzle radius, Sc is the ambient pure fuel Schmidt number, and c, is the mole fraction of fuel burning stoichiometrically in air, the ratio of flame length to nozzle radius was predicted and experimentally verified to be proportional to Sc1/2 Re ln1/2 (1/(1−c8)).
35 citations
TL;DR: In this article, a simplified statistical theory developed previously is employed to analyze the equilibrium and near-equilibrium combustion of initially unmixed reactants, and it is found that the flame zone in the limit of large Damkohler numbers is very thick and is of the order of the local integral scale of turbulence.
Abstract: The simplified statistical theory developed previously is employed to analyze the equilibrium and near‐equilibrium combustion of initially unmixed reactants. It is found that the flame zone in the limit of large Damkohler numbers is very thick and is of the order of the local integral scale of turbulence. This is in contrast to the existing phenomenological theories which predict the infinitesimally thin flame sheet, in the same limit, as it is with the laminar diffusion flame. Qualitative agreements with the available experimental results are shown. It is found that singularities exist at the edges of the flame which are removed as Damkohler number is reduced. Also, it is found that the heat transfer may take place against the local mean temperature gradient in certain regions within the flame.
34 citations
TL;DR: In this paper, it is shown that the fraction of carbon in the fuel liberated as soot is determined largely by the physical characteristics of the flame rather than by the detailed chemical nature of the fuel, and the effect on soot production of the addition of oxygen to the fuel is studied under conditions for which the physical parameters are carefully controlled.
34 citations
23 citations
TL;DR: In this paper, the reaction Ba + O 2 was studied by a diffusion flame technique and it was found that emission from the A → X system of BaO was unaffected by the presence of atomic oxygen but greatly affected by addition of inert third body.
22 citations
TL;DR: The phosphorus content of lubricating oils is determined by measurement of the emission from the HPO molecular species at 528 nm in a cool hydrogen-nitrogen diffusion flame with precision +/- 5% at the 0.04% phosphorus level.
18 citations
TL;DR: In this paper, the authors measured the deviation of the opposed-jet diffusion flame or the distance between the flame and the impingement plane, and found that the deviation varies discontinuously at a certain jet velocity.
18 citations
01 Jan 1972
TL;DR: In this article, a mathematical model for combustion systems is proposed, which can be incorporated into a digital-computer program to improve the design and operation of combustion systems by prior predictions of performance.
Abstract: The Problem Considered — Economical design and operation of combustion systems can be greatly facilitated by prior predictions of performance by way of a mathematical model, incorporated into a digital-computer program. Morever, since the emission of pollutants is more sensitive to detailed design changes than is the overall heat transfer or power output of the system, the refined insight provided by predictions of concentration distributions is especially valuable nowadays. Suitable mathematical models exist for simple combustion systems and are being developed for others.
TL;DR: In this paper, a theoretical analysis of the gas-dynamic structure of a counter-flow diffusion flame established in the forward stagnation region of a porous cylinder is made on the basis of the flame surface and the boundary layer approximations.
Abstract: A theoretical analysis of the gasdynamic structure of a counter-flow diffusion flame established in the forward stagnation region of a porous cylinder is made on the basis of the flame surface and the boundary layer approximations. The numerical calculation is performed to obtain the gasdynamic flame structure for the methane-air system and the obtained profiles of temperature, density and velocity are found to correlate satisfactory with those of experiment.
Patent•
27 Jan 1972
TL;DR: In this paper, the authors propose a method and an approach for obtaining rapid bondings by using a high voltage, high temperature, high humidity, and direct flame in combination with pressure.
Abstract: A METHOD AND APPARATUS FOR OBTAINING RAPID BONDING OF THERMOPLASTIC MATERIALS TO THEMSELVES OR OTHER SIMILAR OR DIFFERENT MATERIALS BY THE USE IOF A HIGH VELOCITY, HIGH TEMPERATURE DIRECT FLAME IN COMBINATION WITH PRESSURE. THE METHOD IS SUFFICIENTLY RAPID SO THAT THE PROPERTIES OF THE MATERIALS ARE NOT SUBSTANTIALLY DETRIMENTALLY AFFECTED. THIN LAMINATES OF HIGHLY ORIENTED MATERIALS CAN BE BONDED WITHOUT LOSS OF STRENGTH CHARACTERISTICS.
TL;DR: In this paper, a set of equations from which turbulent flame velocities can be calculated with reasonable accuracy over a wide range of conditions is presented. They consist of the Karlovitz's equation on turbulent flame velocity and an equation expressing the amplifying effect of a flame on the turbulence level, and they were found to fit the various types of flame fairly well from confined turbulent flames to open burner flames, regardless of the burner size or the fuel type.
01 Jan 1972
TL;DR: In this article, a vertical coaxial burner was used to study the formation of nitric oxide (NO) in diffusion flames, and detailed radial profiles for each of the above species were established through use of a 0.001 inch diameter Pt/Pt-10%Rh thermocouple.
Abstract: A vertical coaxial burner has been used to study nitric oxide formation in diffusion flames. Localized combustion gas samples extracted from the diffusion flame by means of a quartz microprobe have been analyzed for NO as well as for the species CO, CO2 N2, O2 and CH4, the fuel employed. In this manner it has been possible to establish detailed radial profiles for each of the above species. Concomitant temperature profiles have been established through use of a 0.001 inch diameter Pt/Pt-10%Rh thermocouple.
TL;DR: In this paper, the problem of opposed-jet diffusion flame is considered for general Lewis numbers and solutions are obtained by using Modified Flame Surface Theory and Extinction-Ignition characteristics have been brought out.
Abstract: The problem of opposed-jet diffusion flame is considered for general Lewis numbers. The solutions are obtained by using Modified Flame Surface Theory and Extinction—Ignition characteristics have been brought out. Analysis shows that the gases with high Lewis numbers are preferable for the purpose of flame stabilization.
TL;DR: In this article, an analytical description for the generation of noise in burning fuel-air mixtures is presented, and the role of flame and mixture turbulence in causing a varying heat release rate and noise is noted.
Abstract: An analytical description is presented for the generation of noise in burning fuel‐air mixtures. Fluctuating pressure (noise) is shown to result when the heat release rate of the mixture passing through the reaction zone is variable with time. Experimental evidence in support of this view is presented and referenced from the literatures of acoustics and combustion. Several illustrative examples from common experience are pointed out. Premixed and diffusion flames of gas and liquid fuels are considered, and the role of flame and mixture turbulence in causing a varying heat release rate and noise is noted. The possibility appears to exist for substantially reducing the noise output of large combustion systems (jet engine, for example) by more effective control of the flame configuration and stability.
TL;DR: In this paper, the results of experimental and theoretical studies of streamline deflection in diffusion flames are presented for approximately streamwise flames stabilised on a Parker-Wolf hard burner.
Abstract: The results of experimental and theoretical studies of streamline deflection in diffusion flames are presented for approximately streamwise flames stabilised on a Parker-Wolf hard burner. It is shown that both the displacement of the dividing streamline from the flame sheet and the phenomenon of streamline refraction through the flame sheet can be predicted at least qualitatively by a simple linearised model for the diffusion flame in Oseen flow, in which only the irrotational pressure, temperature and composition waves are considered. Although this treatment involves the description of flame properties in terms of disturbances from freestream values, essentially the same results are obtained by linearisation about flame sheet properties. The question is left open whether the present mechanism for streamline refraction is that which leads to transfer of fuel or oxidant across the base of the flame close to extinction, eventually leading to flame lift and complete extinction.
TL;DR: In this article, the authors analyzed the stabilizing region of a fuel-rich methane-air flame, with and without vitiation of the secondary combustion air, with a view to resolving various uncertainties as to the stabilising mechanism of burner-stabilized flames.
TL;DR: The study group of Natural Gas Flames (G.G.E.F.N) made trials on industrial diffusion flames in the Research Station of TOULOUSE as discussed by the authors.
Abstract: The Study Group of Natural Gas Flames (G.E.F.G.N.) makes trials on industrial diffusion flames in the Research Station of TOULOUSE. During these investigations some results about soot particles sampled in flames were collected. These soot particles make up the main source of luminosity of flames Sampling of gas and soot particles in the flame are done with a cooled I.F.R.F. type probe In the case of a diffusion flame of natural gas one can observe the formation and subsequently the burning out of certain products: carbon monoxide, hydrogen and unsaturated hydrocarbons. At the same time the production of soot in the flame is noticed The same phenomenons take place in a heavy fuel oil flame. The soot particles, sampled at different points in a flame have been observed with an electron microscope. The mean size of particles is about 250 A, both for heavy fuel oil and natural gas Electron microdiffraction reveals that soot has an amorphous structure in the two cases The chemical nature is different: ...
TL;DR: In this paper, the authors present results of experiments which were undertaken with the aim of determining reaction rate data in turbulent diffusion flames of industrial size, burning fuel oil and gas, and an effective activation energy for soot formation in propane flame is derived.
Abstract: The report presents some results of experiments which were undertaken with the aim of determining reaction rate data in turbulent diffusion flames of industrial size, burning fuel oil and gas. After a description of the burner systems used, the choice of input parameters which would allow for the evaluation of reaction rate data from locally measured flame properties, is discussed. The change of carbon distribution along the flame axis, as a function of input conditions, is demonstrated, and an effective activation energy for soot formation in propane flame is derived.
TL;DR: In this paper, the phosphorus content of fire-resistant textiles is determined by measurement of the emission intensity at 528 nm of the HPO molecular species, produced by aspiration of an aqueous sample extract into a cool hydrogen-nitrogen diffusion flame.
Abstract: The phosphorus content of fire-resistant textiles is determined by measurement of the emission intensity at 528 nm of the HPO molecular species, produced by aspiration of an aqueous sample extract into a cool hydrogen-nitrogen diffusion flame. In the case of durable flame-retardant agents, a preliminary fusion of the textile with potassium hydroxide is necessary, followed by an ion-exchange treatment of the extract; non-durable flame-retardants are determined directly, after water extraction of the material and ion-exchange separation.
TL;DR: In this paper, an interferometric study of the thermal structure of a flame of a liquid alcohol flame was performed. Butterworth et al. proposed an approach for stabilizing diffusion flames of liquid fuels.
Abstract: A ethod for stabilizing diffusion flames of liquid fuels has been described. Results are presented for the thermal structure of such a flame (of ethyl alcohol) as determined by an interferometric study.
TL;DR: A formulation of the diffusion-kinetic model based on the spherical diffusion flame method is presented and discussed in this article, where the application of this technique has been made to obtain the relative rates o...
Abstract: A formulation of the diffusion-kinetic model based on the spherical diffusion flame method is presented and discussed. The application of this technique has been made to obtain the relative rates o...
TL;DR: In this article, it is shown that for a diffusion flame to exist above the propellant surface, two conditions must be satisfied simultaneously: 1) the surface temperature must equal the gasification temperature for that propellant and 2) the temperature gradient at the surface must be smaller than some value which depends on the kinetics of the chemical reaction in the diffusion flame and on the rate of oxidizer input to the surface during burning.
Abstract: At present, the study of solid-propellant ignition is of particular interest owing to the adoption of hybrid motors [1–3]. The status of experimental and theoretical research in this field can be evaluated on the basis of the rather extensive survey of American papers in [2]. It is noteworthy that a common deficiency in available references is the absence of exact ignition criteria; in most cases the propellant is assumed to have ignited when its surface temperature reaches a prescribed level (gasification temperature), or when the rate at which the temperature increases with time at the propellant surface is sufficiently high. Exact criteria for this rate, however, are not given. In this article, we present ignition criteria for solid propellants and these are based on a diffusion-burning model. It is shown that for a diffusion flame to exist above the propellant surface, two conditions must be satisfied simultaneously: 1) the propellant surface temperature must equal the gasification temperature for that propellant and 2) the temperature gradient at the surface must be smaller than some value which depends on the kinetics of the chemical reaction in the diffusion flame and on the rate of oxidizer input to the propellant surface during burning. Two ignition techniques are examined as examples: ignition by hot gases or radiant heat flow and ignition by means of an active film which reacts with a cold oxidizer; the film is applied to the propellant surface prior to ignition.
TL;DR: In this article, a counterflow burner is used to stabilize one-dimensional diffusion flames of a large size, and temperature treasurements on these flames have been made by the deflection method.
Abstract: A counter-flow burner has been used to stabilize one-dimensional diffusion flames of a large size, and temperature treasurements on these flames have been made by the “deflection method.” The distance between the stagnation point and the flame shows a discontinuity when the velocity gradient along the flame reaches a critical value e tr [1] and there is a corresponding discontinuity in the temperature. Analysis of experimental results indicates that, though the ratio of oxygen to fuel mass flux into the flame front is held constant below this value it shifts towards more fuel rich ratios when e tr is exceeded. This can be ascertained from the measured concentrations of combustion products around the flame front. Furthermore, a kinetic analysis of the flames indicates that such discontinuities are to be expected.
TL;DR: In this article, the authors measured the deviation of the opposed-jet diffusion flame or the distance between the flame and the impingement plane, and found that the deviation varies discontinuously at a certain jet velocity.
Abstract: In this study measuring the deviation of the opposed-jet diffusion flame or the distance between the flame and the impingement plane, it is found that the deviation varies discontinuously at a certain jet velocity. The analytical results on the relation between the deviation and the jet velocity, which are obtained from thin flame kinetics following the usual concept that the ratio of O 2 mass flux to fuel mass flux into the flame front is stoichiomatric, are qualitatively consistent with the measured values at lower jet velocities than the velocity of discontinuity. From these results it is possible to say that the stability of diffusion flames stretched violently at higher jet velocities follows a different concept from usual.