Showing papers on "Combustion published in 1983"

Gas Turbine Combustion

Abstract: 1.Basic Considerations 2.Combustion Fundamentals 3.Diffusers 4.Aerodynamics 5.Combustion Performance 6.Fuel Injection 7.Combustion Noise 8.Heat Transfer 9.Emissions

Compression-Ignited Homogeneous Charge Combustion

Abstract: Experimentally obtained energy release results, a semi-empirical ignition model, and an empirical energy release equation developed during this research were used to evaluate the combustion of compression-ignited homogeneous mixtures of fuel, air, and exhaust products in a CFR engine. A systematic study was carried out to evaluate the response of compression-ignited homogeneous charge (CIHC) combustion to changes in operating parameters with emphasis being placed on the phenomena involved rather than the detailed chemical kinetics. This systematic study revealed that the response of the combustion process to changes in operating parameters can be explained in terms of known chemical kinetics, and that through the proper use of temperature and species concentrations the oxidation kinetics of hydrocarbon fuels can be sufficiently controlled to allow an engine to be operated in a compression-ignited homogeneous charge combustion mode.

Nitrogen oxides in the troposphere: Global and regional budgets

Abstract: The cycle of nitrogen oxides in the troposphere is discussed from both global and regional perspectives. Global sources for NO(x) are estimated to be of magnitude 50 (+ or - 25) x 10 to the 12th gm N/yr. Nitrogen oxides are derived from combustion of fossil fuels (40 percent) and biomass burning (25 percent) with the balance from lightning and microbial activity in soils. Estimates for the rate of removal of NOx based on recent atmospheric and precipitation chemistry data are consistent with global source strengths derived here. Industrial and agricultural activities provide approximately two thirds of the global source for NOx. In North America, sources from combustion of fossil fuels exceed natural sources by a factor of 3-13. Wet deposition removes about one third of the combustion source of NOx over North America, while dry deposition removes a similar amount. The balance is exported from the continent. Deposition of nitrate in precipitation over eastern Canada and the western Atlantic is clearly influenced by sources of NOx in the eastern United States.

Development and Use of a Spray Combustion Modeling to Predict Diesel Engine Efficiency and Pollutant Emissions : Part 1 Combustion Modeling

Abstract: A mathematical model of a spray combustion in direct-injection diesel engines has been developed to predict engine performance, thermal efficiency and pollutant emissions. Injected fuel spray was divided into many small packages. Gas and fuel droplet temperatures and evaporated mass of fuel in each package were computed. In considering the complete air-fuel jet mixing process and temperature in each package, the model also enabled subsequent spatial and temporal history of burning rate, local temperature and air-fuel ratio to be calculated.

Retene-a molecular marker of wood combustion in ambient air

Abstract: The use of wood as a fuel has increased since the oil embargo in 1973. Several studies have shown that wood combustion may make a significant contribution to air pollution. Using 14C as a tracer for contemporary carbonaceous materials, 30–70% of the atmospheric carbon has been shown to originate from wood combustion in areas affected by this source1–3. Other studies have shown that emissions from wood combustion contain large amounts of particles4–6 and organic compounds, one class being poly cyclic aromatic hydrocarbons (PAH)7–11. However, these compounds are also formed by combustion of other carbonaceous materials. In our studies on PAH in wood combustion emissions and in ambient air in wood-heated residential areas, we have identified several PAH compounds which may be related to combustion of coniferous wood. These are alkylated phenanthrene compounds with the main compound 1-methyl-7-isopropylphenanthrene (trivial name retene) formed by thermal degradation of resin compounds in the wood.

Combustion gas powered fastener driving tool

Abstract: A fastener applying tool is disclosed, powered by the gases produced from internal combustion of a fuel and air mixture. A piston connected to a fastener driver is slidably mounted within a cylinder to move reciprocally downwardly and upwardly through a driving and a return stroke. A combustion chamber is formed at the upper end of the cylinder. A compression chamber is formed at the lower end of the cylinder. A spark plug powered by a piezo-electric firing device, is located within the combustion chamber. The combustion chamber features a set of fan blades driven by an electric motor which is continuously in operation when the tool is in use. A main valve mechanism actuated by a set of lifting rods which are moved upwardly and downwardly when the tool is moved toward and away from the workpiece, is used to control the flow of fresh air through the combustion chamber. When the combustion chamber is isolated from the atmosphere and the fuel and air are thoroughly mixed, the spark plug is fired to explode the fuel and air mixture and force the piston through its driving stroke. The rapid discharge of combustion gases at the end of the driving stroke produces a thermal vacuum within the combustion chamber. Additional air supplied to the lower face of the piston from the atmosphere forces the piston through its return stroke.

Method for operating a production well in an oxygen driven in-situ combustion oil recovery process

Abstract: A method for operating a production well during an oxygen driven in-situ combustion oil recovery process comprising continuously injecting an inert gas such as nitrogen or carbon dioxide into the bottom of the production well at a predetermined low injection rate, preferably 0.1 to 2 MSCF/day, and continuously monitoring the oxygen concentration of the produced effluent gas and the bottomhole temperature of the production well. In the event that the oxygen content of the effluent gas increases to a value within the range of 5 to 20 volume percent or the bottomhole temperature of the production well increases to a value within the range of 200° to 300° F., the injection rate of the inert gas into the bottom of the production well is increased to a maximum rate until the oxygen concentration of the effluent gas and the bottomhole temperature are reduced to a safe level.

Portable gas-powered tool with linear motor

Abstract: An efficient, portable, easy to operate tool employing a linear motor is disclosed that is powered by the gases produced from the internal combustion of a fuel and air mixture. A supply of liquified gas stored under pressure in a cylinder provides the source of power. The linear motor is slidably mounted within a cylinder to move reciprocally downwardly and upwardly through a driving and return stroke. A combustion chamber is formed at the upper end of the cylinder. A spark plug powered by a piezo-electric firing device is located within the combustion chamber. The combustion chamber features a turbulence generator, such as a fan, driven by an electric motor which is continuously in operation when the tool is in use. A main valve mechanism actuated by a set of lifting rods that are moved upwardly and downwardly when the tool is moved towards and away from the workpiece, is used to control the opening and closing of the combustion chamber and to control the flow of fresh air through the combustion chamber. When the combustion chamber is isolated from the atmosphere and the fuel and air are thoroughly mixed, the spark plug is fired to explode the fuel and air mixture and force the linear motor through its driving stroke. The linear motor is returned to its driving position by a spring or air acting against the underside of the linear motor. The unique use of the electric fan improves the overall operational efficiency of the tool and the utilization of the liquified combustible gas.

The Mechanism of High Temperature Combustion of Propane and Butane

Abstract: By combination of a mechanism describing lean and moderately rich combustion of alkanes and alkenes with a mechanism describing rich combustion and formation of soot pre-cursors in acetylene flames, a general reaction scheme is developed for the simulation of lean and rich high-temperature combustion of hydrocarbons up to C4 - species. Results of these simulations are compared to experimental data, and some consequences of this reaction scheme are discussed with respect to future experimental work on rich flames of propane and butane.

Comparison of quartz and Pyrex tubes for combustion of organic samples for stable carbon isotope analysis

Abstract: Most laboratories that perform routine stable carbon isotope determinations on organic samples employ a sealed-tube combustion method. Because Pyrex tubing is approximately 14% of the cost of quartz tubing, /sup 13/C values and percent carbon obtained on a variety of organic substances have been compared using both the combustion in quartz tubing at 850/sup 0/ and in Pyrex tubing at 550/sup 0/C. On the average, yields of carbon were 28% lower for the Pyrex method. Despite incomplete combustion, mean /sup 13/C values were virtually identical for a given organic sample whether it was combusted by the quartz or Pyrex method. Potential drawbacks of the Pyrex method include: susceptibility to cracking during rapid temperature change; incomplete combustion preventing quantitative analysis of carbon; and more variable replicate /sup 13/C determinations. 5 references, 1 table.

Using a global hydrogen-air combustion model in turbulent reacting flow calculations

Abstract: A two-step global model describing the combustion of hydrogen in air at 1 atm pressure is developed by comparing the temperature histories obtained from a 28 reaction H-O mechanism. Using criteria discussed herein, good agreement is obtained in the range of initial mixture temperatures of 1000-2000 K and in the range of equivalence ratios of 0.2-2.0. The two-step global model is compared with the results obtained using an eightstep, H-O reaction mechanism in a computer program describing the turbulent diffusion of hydrogen in supersonic axisymmetric and two-dimensional reacting flows. Comparisons of profiles of temperature and pitot pressure are presented. The global model is judged to be adequate in flows which are not dominated by long ignition delay times.

Lectures on mathematical combustion

Abstract: Pre-asymptotic combustion revisited Governing equations, Asymptotics, and deflagrations General deflagrations SVFs and NEFs Stability of the plane deflagration wave Cellular flames Pulsating flames Counterflow diffusion flames Spherical diffusion flames Free-boundary problems.

Carbon attrition during the fluidized combustion of a coal

Abstract: The generation of carbon fines by attrition during the fluidized combustion of a bituminous coal has been studied by means of a 140mm ID fluidized-bed combustor under variable excess air factor, bed temperature, fluidizing velocity and size of bed sand and coal. Results indicate that rates of attrited fines are roughly proportional to excess of gas velocity above the minimum for fluidization and bed carbon exposed surface. Attrition rate constant is affected by size of sand and, to a less extent, and particularly with finer coal, by bed temperature.

Metallic elements in fossil fuel combustion products: amounts and form of emissions and evaluation of carcinogenicity and mutagenicity.

Abstract: Metallic elements contained in coal, oil and gasoline are mobilized by combustion processes and may be emitted into the atmosphere, mainly as components of submicron particles. The information abou...

An Introduction to the Burning Behaviour of Cellulosic Fibres

Abstract: The actions of heat and flame on cellulosic fibres are compared with the physical and chemical behaviour of other fibres. The combustion mechanism is discussed in terms of concerted pyrolysis and oxidative stages, which can be represented as an energy feedback system. The action of different flame retardants are seen to interfere with the system and thereby inhibit burning. The condensed-phase synergistic mechanism of phosphorus-nitrogen-containing retardants used for cotton and viscose rayon are discussed in terms of char enhancement whereas halogen-based retardants operate in the vapour phase. The latter synergistically function in the presence of antimony (III) oxide and, although lacking extreme durability, offer the advantage of conferring flame retardance to adjacent fibrous and non-fibrous materials. The effect of retardants on smoke and combustion product toxicity is also considered.

Filtration combustion of gases

Abstract: 1. The process of filtration combustion of a gas in an inert porous medium has been carried out experimentally and investigated. The possibility is shown for the propagation of combustion waves counter to the flow and in the direction of the flow, and for the “standing wave” state. The significant role in the process of such factors as the flow velocity, heat content of the mixture, and the size of the elements of the medium is established. 2. A two-temperature model of the filtration combustion of gases has been constructed and validated which describes the effect of the parameters on the characteristics of the process. The model predicts, in particular, the existence of a temperature peak in the zone of chemical reaction and of the existence of anomalously low and high combustion temperatures. The theoretical conclusions coincide satisfactorily with experiment. 3. The presence of two regimes of filtration combustion of gases is established: low velocities with a strong thermal interphase interaction, and high velocities with a weak thermal interaction. The possibility is shown for the existence of limits of combustion wave propagation, due to thermal losses. 4. An important element of the mechanism of filtration combustion of a gas in the regime of low velocities is the recuperation of heat in the cycle: combustion products-porous medium-fresh gas-combustion products. In this case the thermophysical characteristics of the medium play a decisive role in the structure and propagation of combustion waves.

Hydrocarbon Oxidation at High Temperatures

Abstract: The detailed knowledge of combustion mechanisms is important, for example for the control of (kinetically determined) pollutant formation (e.g. NO, hydrocarbons, soot), for ignition problems, or for the extrapolation to technologically important but experimentally inaccessible condition. – In this review it is described how by suitable separation and elimination of unimportant reactions a mechanism is developed with the aid of the present kinetic data for the elementary reactions involved. This mechanism explains, without fitting, the currently available experimental results for laminar premixed flames of alkanes, alkenes and acetylene (flame velocity and structure of free flames, concentration and temperature profiles in burner-stabilized flames). These experimental results are simulated by the solution of the corresponding conservation equations with suitable models describing diffusion and heat conduction in the multicomponent mixture considered. – In lean and moderately rich flames the hydrocarbon is attacked by O, H, and OH in the first step. These radicals are produced by the chain-branching steps of the oxyhydrogen reaction. The alkyl radicals formed in this way always decompose to smaller alkyl radicals by fast thermal elimination of alkenes. Only the relatively slow thermal decomposition of the smallest alkyl radicals (CH3 and C2H5) competes with recombination and with oxidation reactions by O atoms and O2. This part of the mechanism is rate-controlling in the combustion of alkanes and alkenes, and is therefore the reason for the similarity of all alkane and alkene flames. – In rich flames of aliphatic fuels, acetylene becomes a very important intermediate leading to soot precursors and to Non-Zeldovich-NO. Details of the reaction mechanisms are not yet known.

An Asymptotic Theory of Condensed Two-Phase Flame Propagation

Abstract: A model is presented for flame propagation though a condensed combustible mixture in which the limiting component of the mixture melts during the reaction process. An asymptotic analysis, valid for large activation energies, is employed to derive a two-term expansion for the steady, planar adiabatic flame speed. A linear stability analysis is then used to show that for sufficiently large values of the activation energy and/or a special group of melting parameters, the steady, planar solution loses stability to various types of planar and nonplanar pulsating modes. The effect of melting is found to be destabilizing in the sense that these pulsating modes occur for lower values of the activation energy than would be the case for strictly solid fuel combustion.

Experiments concerning the mechanism of flame blowoff from bluff bodies

Abstract: The general problem of flame stabilization on bluff objects centers about the determination of the maximum stream velocity at which stable combustion may be achieved for various flame holder geometries, gas mixtures and conditions of the approaching combustible stream. Since the process involves both gas dynamic problems and chemical kinetic problems of great complexity, the most reasonable approach is one of similarity, that is, to determine under what conditions the behavior of one flame holder is similar to the behavior of another one. Because a very large number of physical and chemical variables is involved in a combustion problem, similarity conditions can be formulated most easily after experimental investigations have indicated which parameters or groups exert little influence on the mechanism and hence may be neglected. The experiments described in this paper were conducted with the object of clarifying the role of the more important parameters in the flame holding mechanism. The results indicate that a relatively simple formulation of the similarity conditions may be obtained in which the fluid mechanical parameters and chemical parameters are effectively separated.

Resonator for internal combustion engines

Abstract: A resonator for internal combustion engines, having an enclosed chamber of predetermined volumn connected to an intake duct by a tubular connecting member which is composed of an external member and an internal member. The internal member is disposed within the external member and moved by an actuator which is controlled by an electrical signal corresponding to a resonant frequency calculated by a computer in synchronism with engine rotational speeds. The resonator thereby functions to absorb resonant noises from the engines by appropriately changing the length and/or cross-sectional area of the tubular connecting member.

Cavity resonances in engine combustion chambers and some applications

Abstract: Cavity resonances in engine cylinders are caused by combustion events such as the rapid rate of pressure rise that occurs during compression ignition in diesels or from knock in gasoline engines. These resonances generally occur at frequencies greater than 4 to 5 kHz where the engine structure is not an efficient acoustical radiator. However, when they occur at lower frequencies such as in engines with a large bore or in indirect injection diesels, they can be important in the noise generation process. They are also important for knock detection in gasoline engines. Current knock detection systems are tuned to the frequency band of the lowest cavity resonance in the combustion chamber. It is shown in the paper that higher order resonances can also be detected by a knock vibration sensor on the surface of the engine. Another use for the cavity resonances is to determine the bulk temperature of the gas in the combustion chamber as a function of crank angle. This technique is demonstrated in the paper for a heavy‐duty two‐stroke diesel. Also, the results of several fundamental investigations of cavity resonances in engine combustion chambers are reported briefly. Good agreement is obtained between theoretical prediction of the resonant frequencies and experimental observation. The splitting of degenerate modes into two components is discussed.

Hybrid solar/combustion powered receiver

Abstract: An improved hybrid solar/combustion powered receiver, for use e.g. with a hot gas engine, the receiver being of the type having a housing and an aperture for admitting solar radiation to the cavity defined by the housing. The improved receiver includes a heat exchanger within the cavity and having the tubes tangentially spaced; multiple burners for providing a combustion gas flow path during combustion powered operation between and around the portions of the tubes upon which solar radiation impinges; and a fused silica, internally mounted window to seal the aperture against combustion gas leakage out of the receiver.