Showing papers on "Combustion published in 1987"

Catalysis in Combustion

Abstract: Catalysis and combustion have long been linked. In fact, the science of catalysis stems from Davy's discovery [1] that platinum wires could promote the flameless combustion of flammable fuel-air mixtures. Today, catalysis is a mainstay of our modern chemical industry. Oxidation catalysts are used not only for the complete oxidation of fuels to carbon dioxide and water, as in radiant catalytic tent heaters and fume abatement devices, but also for the selective partial oxidation of hydrocarbons or other “fuels” to produce basic chemicals such as ethylene oxide (from ethylene), terephthalic acid (from p-xylene), and nitric acid (from ammonia). However, despite the long-known capability of catalysts to oxidize hydrocarbons without significant production of carbon monoxide, soot, or thermal NOx, there seemed little possibility that catalytic oxidation reactors could ever displace conventional flame combustors as primary fuel combustors. This is because the volumetric heat release rates of conventional...

Chemical Kinetic Data Base for Combustion Chemistry. Part 2. Methanol

Abstract: This publication contains evaluated and estimated data on the kinetics of reactions involving methanol and hydroxymethyl radicals and various small inorganic and organic species which are of importance for the proper understanding of methanol combustion and pyrolysis. It is meant to be used in conjunction with the kinetic data given in an earlier publication pertaining to methane pyrolysis and combustion, but which also contains a large volume of data that are applicable to the methanol system. The temperature range covered is 300–2500 K and the density range 1×1016 to 1×1021 molecules cm−3.

Method and apparatus for conversion of coal in situ

Abstract: A method for the electro-thermal and electrochemical underground conversion of coal into oil and by-products comprises the steps of inserting an underground probe into a bore hole until the probe is in close proximity to a coal seam. A mixture of air, steam, an electrolyte and a suitable catalyst is supplied to the probe, and the mixture is then sprayed directly on the coal seam through a passage in a nozzle. The probe is also energized with electricity applied to the nozzle to produce an arc between the coal and the probe, simultaneous with the spraying of the mixture on the coal seam. Heat of the combustion from the arc and the steam combine to produce a pyrolysis, oxidation, and reduction of the coal, thereby converting the coal into a gaseous combination of oil and by-products. The arc can be rotated to increase the tunnel diameter. An apparatus for performing the method is also provided.

Process for converting heavy crudes, tars, and bitumens to lighter products in the presence of brine at supercritical conditions

Abstract: A majority amount of a heavy hydrocarbon crude is reacted with a minor amount of brine, at supercritical temperature and pressure for the brine, for a predetermined period of time in order to upgrade and convert the heavy hydrocarbon crude into a lighter hydrocarbon crude of higher API gravity. The upgrading and conversion of a viscous heavy hydrocarbonaceous crude oil into lighter hydrocarbons is accomplished in a continuous reactor system and may be accomplished in a subterranean petroleum reservoir at supercritical temperature and pressure. The overall heat of reaction is neutral, i.e., neither exothermic nor endothermic. In order to provide the necessary temperature, heat is added to the system prior to the reaction. For an in situ application, a combustion operation may be utilized to provide the necessary temperature, and is initiated using an oxidizing gas injected through an injection well. After a predetermined amount of time, injection of the oxidizing gas is terminated and the injection well is shut-in for a predetermined period of time to permit the petroleum reservoir to undergo a soak period in order to increase the temperature and decrease the viscosity of the viscous heavy hydrocarbonaceous crude oil. As the viscosity of the heavy hydrocarbonaceous crude oil decreases, the oil flows downwardly into the combustion zone steam and/or brine is injected which is at supercritical conditions in order to upgrade the heavy hydrocarbonaceous crude oil into lighter fractions. The reaction products from a reactor or an in situ operation are also lower in obnoxious constituents such as sulfur, nitrogen and heavy metals.

Structural analysis of soot agglomerates

Abstract: Etude de la structure des agglomerats de noir de carbone formes par combustion d'acetylene dans un bruleur a diffusion coannulaire

An investigation of the synthesis of nickel aluminides through gasless combustion

Abstract: The formation of nickel aluminidms by the thermal explosion mode of gasless combustion synthesis was investigated for Ni-Al powders ranging in composition from 5 to 3O at% Al. Compound formation was found to take place sequentially starting with the most aluminium-rich and ending with AlNi3 as the predominant compound in the product. Compounds formed through both solid- and liquid-sate reactions, with the relative contribution of each depending on the rate of heating of the powders to the reaction temperature. The effect of the particle size of nickel on these reactions vvasalso investigated for powders with average diameters from 14 to 58μm.

Estimating Heat-Release and Mass-of-Mixture Burned from Spark-Ignition Engine Pressure Data

Abstract: A First Law analysis based on the cylinder pressure variation during combustion is a commonly used diagnostic for determining actual spark-ignition engine burning rates. Both simple one-zone and more complex two-zone models have been developed for this purpose. It is shown that the fraction of the fuel's chemical energy which has been released and the fraction of fuel-air mixture burned, within the engine's cylinder, can be accurately estimated from a one-zone analysis if appropriate values for the “average ratio of specific heats”, y¯, of the one-zone contents are used. These values are determined by matching the output of the one-zone analysis to that of the more rigorous two-zone analysis of the same cylinder pressure data. Use of this one-zone burning rate analysis procedure is illustrated.

Autoignition of adiabatically compressed combustible gas mixtures

Abstract: Measurements of explosion limits for fuel/air/diluent mixtures compressed by an expanding laminar flame have been made in a constant volume spherical bomb. The fuels studied to date range from butane to octane at fuel/air equivalence ratios from 0.8 to 1.3. The explosion pressures and temperatures range from 10 to 100 atm and 650 to 850 K. The pressure versus time curves show the behavior typical of the two-stage ignition process observed in rapid compression machines. A branched chain kinetic model has been developed to correlate the data. The model has been used to predict both the explosion limits measured in the current bomb experiments and ignition delays measured in prior rapid compression machine experiments. Good agreement between experiment and theory can be achieved with minor adjustment in published rate constants.

Heat insulation of combustion chamber walls ― a measure to decrease the fuel consumption of I.C. engines?

Abstract: Experimental investigations were made with a single-cylinder direct-injection Diesel engine with heat-insulated piston. The most important result is an inferior economy compared with the not insulated aluminum-piston engine. It was found that this phenomenon is not caused by neither a changed combustion process nor increased blowby nor different friction losses, but rather by a drastic increase of the heat transfer coefficient during the first part of combustion with increasing surface temperature. This is taken into account in a modified equation for the heat transfer coefficient. Cycle-simulations using this modified equation show that there is neither a gain in fuel economy of naturally aspirated nor of turbocharged nor of turbocompound Diesel engines with ''heat insulated'' combustion chamber walls.

Muffler apparatus with filter trap and method of use

Abstract: Muffler apparatus for reducing both sound and particulates from exhaust gases from an engine. The apparatus includes resonating chambers, flow distribution structure and a cellular ceramic core filter module. Filter regeneration mechanism includes a heating element for heating the carbon on the inlet end of the ceramic core to combustion temperature. Particulate ignition resulting in regeneration occurs when combustion air is provided; in alternate embodiments, combustion air first flows through a preheater system. A processor unit with particular logic controls the apparatus.

Progress Toward Shock Enhancement of Supersonic Combustion Processes

Abstract: In air breathing propulsion systems for flight at Mach numbers 7 to 20, it is generally accepted that the combustion processes will be carried out at supersonic velocities with respect to the engine. The resulting brief residence time places a premium on rapid mixing of the fuel and air. To address this issue we are investigating a mechanism for enhancing the rate of mixing between air and hydrogen fuel over rates that are expected in shear layers and jets.

Process for producing power

Abstract: A process is disclosed for producing mechanical energy or electric power from chemical energy contained in a fuel, utilizing a combustion turbine. The compressed air which is used for combustion of the fuel to drive the turbine is humidified prior to combustion in a multistage countercurrent saturator to replace some or all of the thermal diluent air with water vapor. Humidification is effected with the water at a temperature below its boiling point at the operating pressure. The compressed air is cooled prior to humidification by passing in heat exchange relationship with the water used for humidification. Low level heat is rejected from the compressed air during intercooling and prior to humidification. This process provides a significant improvement in thermal efficiency, compared to combined cycle, steam injected cycle, intercooled regenerative cycle, and other air humidification based processes. Additionally, the entire steam cycle of a combined cycle process is eliminated, including the steam turbine generator, steam drums, surface condenser and cooling towers.

Liquid-fueled supersonic combustion ramjets - A research perspective

Abstract: A review of past and current research applicable to liquid-fueled supersonic combustion ramjets is presented and discussed. An assessment of its strengths and shortcomings is made and, finally, a list of research opportunities that merit consideration in this rapidly expanding area of airbreathing propulsion is presented. Nomenclature = area Cf = average combustor wall skin friction coefficient D = isolator duct diameter d = injector diameter ER = fuel-air equivalence ratio / = fuel-air ratio h - penetration height, enthalpy Ah = driving enthalpy (Ref. 85) M -Mach number P = static pressure q = fuel-to-freestream dynamic pressure ratio, average q = combustor wall heat flux Ree = Reynolds number based on momentum thickness Sd = length of precombustion shock structure in supersonic combustion Ss = total length of precombustion shock structure T = temperature w =fuel jet lateral spreading w =mass flow rate x = axial distance downstream of injection 6 =fuel injection angle 6m = boundary-layer momentum thickness r/c =heat release combustion efficiency f = average combustor skin friction

Quantitative two-photon LIF imaging of carbon monoxide in combustion gases

Abstract: Two-dimensional imaging of CO concentration in combustion gases is demonstrated using two-photon-excited planar laser-induced fluorescence. A quantitative model is presented for the simultaneous two-photon excitation of several rotational transitions of the B1∑+ ← X1∑+ system and the subsequent visible fluorescence (B1∑+ → A1Π). The model is verified by comparison of predicted and measured excitation spectra and of temperature-corrected relative fluorescence measurements to standard probe measurements of the center line CO distribution in a CO–air diffusion flame. In addition, CO imaging experiments in a premixed methane–air flame indicate the production of C2 by laser photodissociation of acetylene.

Combustion: A Study in Theory, Fact and Application

Abstract: Part 1 Combustion of gases: fundamentals of chemical kinetics - reaction rates, chemical equilibrium, chemical kinetic rate equations flame propagation in laminar flows - aerodynamics, dynamic stability, flammability limits flame propagation in turbulent flows - vortex stretching, combustion models, wrinkled laminar flame and local reaction models ignition and flame stabilization explosion and detonation diffusion flames. Part 2 Combustion of liquids and solids: combustion of droplets and sprays combustion of coal, combustion of char, transformations of ash, fixed-bed and fluidized-bed combustion free-burning fires - cellulosic materials, fire suppression combustion of condensed systems - the SHS process, combustion of solid propellants environmental aspects of combustion - major pollutants, clean systems. Part 3 Combustion design and research fundamentals: application of chemical reactor theory to combustor design physical modeling of combustion processes - similarity theory basic diagnostic techniques in combustion - measurements, visualization, diagnostics combustion in practical systems - gas-turbibes, boilers, LCVG. Appendices: The earliest scientific definition of combustion and flame data for thermochemical calculations.

Low-Temperature Oxidation Kinetic Parameters for In-Situ Combustion Numerical Simulation

Abstract: The principal objective of this study was to provide low temperature oxidation (LTO) reaction models which are suitable for use in numeric simulators in in situ combustion for bitumen and heavy oil reservoirs. A systematic study was conducted to investigate the LTO reactions of the liquid phase components of bitumen and heavy oils. Kinetic models are established for the liquid phase reaction components involved in the LTO reactions of a mixture of complex hydrocarbons. Based on the experimental kinetic data, 2 main types of reaction models are proposed. There are (1) a nonsteady state kinetic model to represent the overall rate of oxygen consumption, and (2) 4 nonsteady multiresponse kinetic models representing the oxidation reactions of the liquid phase components. 18 references.

The relationship between elemental composition and heat of combustion of microbial biomass

Abstract: Four models taken from the literature, which permit calculation of heats of combustion from elemental analysis, are evaluated from a theoretical point of view. In order to obtain experimental values of heats of combustion with a higher degree of accuracy than those being available in the literature, an improved sample preparation technique based on lyophilisation of microbial biomass has been developed. Heats of combustion were determined by direct measurement in a calorimeter and compared to calculated values from each of the literature models. Giese's formula turned out to predict heats of combustion the most accurately. The enthalpy content of the bacteria investigated (23.13±0.52 kJ/g) differs from that of yeasts (21.21±0.47 kJ/g) in a significant manner.

Low NOx rich-lean combustor especially useful in gas turbines

Abstract: A combustor capable of reducing the noxious emissions such as fuel bound and thermal nitrogen oxide products, during combustion of high nitrogen bearing and high aromatic content fuels is disclosed. The combustor includes a plurality of substantially concentric pipes defining annular passages with annular divergent nozzles. The divergent nozzles may be formed by rings having a venturi shaped axial section to facilitate fast mixing of axially supplied air between adjacent annular passages. The longitudinal spacing between at least two adjacent nozzles defines first and second divergent cavities. A fuel rich torodial vortex is formed in proximity to a central fuel jet in the first cavity and advantageously converts fuel bound nitrogen to N2. A fuel lean torodial vortex formed in the second cavity mixes hot combustion products with additional gaseous reactant to complete the combustion while avoiding locally high temperatures, and thus thermal NOx formation. A ring of jet nozzles radially injects relatively small amounts of high pressure gaseous reactant or steam to form a throat to separate and stabilize the vortices. Alternatively, the pipe extending between the two cavities can include a convergent and divergent portion forming the throat between the cavities for separating and reinforcing the toroidal vortices. Guide vanes may be positioned in the annular passages to swirl the gaseous reactant entering the cavities to assist in the formation of the toroidal vortices.

Rotary internal combustion engine

Abstract: A rotary internal combustion engine has adjacent circular compression and combustion rotors fixed to a shaft and each having a radial vane sliding on an inner surface of a surrounding eccentric circular chamber, and an arcuate transfer passage communicating between the chambers through an intermediate wall via slots in the rotors adjacent the vanes.

Integrated furnace control having ignition and pressure switch diagnostics

Abstract: An integrated electronic control arrangement is disclosed in the illustrative environment of burner such as in a gas-fired furnace. The control incorporates a self-test feature which shuts down the furnace in the event of any one of a number of possible sensed faults. Self-testing occurs automatically before an attempt at ignition and during furnace operation. Proper functioning of the sensor which senses for induced air flow through the burner combustion chamber is tested prior to enabling a fan which causes that induced air flow. Air flow is confirmed by sending to and receiving back from the sensor a sequence of pulses. Should air flow not be sensed during a combustion period, combustion is terminated. A flame sensor is provided for determining the presence of a flame in the combustion chamber. During times when a flame should be present, pulse sequences are sent to and received back from the flame sensor to confirm that a flame is present. When it is known that no flame is present, if sent pulses are received back, a fault has occurred and the system locks out. If, at any time, any pulses are received when none were sent the system also locks out.

Combustion of Aluminum-Based Slurry Agglomerates

Abstract: The combustion of aluminum and aluminum/carbon slurry agglomerates was studied in the post-flame region of a flat-flame burner using cinematography Diameters of the agglomerates after both burnout of the carrier fuel (JP-10) and coalescence of the particles ranged from approximately 300 to 800 microns Burner operating conditions were varied to provide oxygen mole fractions ranging from 010 to 025 and gas temperatures from 1500 K to 1800 K Flame environments both with and without water vapor were considered Vapor-phase burning with a significant accumulation of oxide product was observed for aluminum slurry agglomerates Burning times were approximately four times those of pure JP-10 droplet at corresponding initial sizes and test conditions Exercise of an analytical model which included radiation suggested that gas-phase transport of species from the flame zone and subsequent condensation at the surface is not likely to be the sole mechanism responsible for surface oxide accumulation The

Interaction of radiation with turbulence - application to a combustion system

Abstract: Turbulence/radiation interaction is examined in order to provide better fundamental understanding of temporal aspects of radiative transfer in combustion systems. Two aspects of radiative transfer in a turbulent medium are considered in this paper. In the first, transfer of radiation along a path with turbulent concentration and temperature fluctuations is calculated for the time-mean irradiance at a combustion chamber wall due to random concentration of absorbing species and emission with Gaussian probability density functions. In the second, turbulence/radiation interaction and the effect of radiation transfer on the fully coupled structure and mean properties are assessed for an industrial natural gas-fired furnace. The results of calculations based on the approximate formulation utilized here show that the effects of turbulence/radiation interaction on combustion and flow properties is relatively small for a preheated methane-air mixture. The interaction is greater when the oxidant is cold and the flame is relatively long. 24 references.