Volatile Fuels Research Articles

L-3-1 - Neuropeptides and their receptors

Volatile organic solvents, fuels and anesthetics are subject to abuse. The aim of the present study was to evaluate i.v. self-administration of several of these chemicals in drug- and experiment-naive mice using a commercially available vehicle, intralipid. Two strains of mice (DBA/2 and Swiss) were allowed to self-administer toluene (0.0017–0.17 μmol/infusion), 1,1,1-trichloroethane (0.006–0.19 μmol/infusion), ethanol (0.32–1.6 μmol/infusion), cyclohexane (0.0017–0.052 μmol/infusion), propofol (0.01–0.53 μmol/infusion) and flurothyl (0.00042–0.072 μmol/infusion) or their vehicles during 30-min tests. During the test, each nose-poke of the master mouse resulted in a 1.88-μl i.v. infusion to the master mouse and a yoked control mouse. When the delivery line was loaded with a reinforcing drug solution, the number of nose-pokes of the master mice significantly exceeded that for yoked control mice. In the present experiments, significant differences in rates of nose-poking were observed between mice receiving response-contingent and response-noncontingent deliveries of ethanol and toluene in both strains of mice and of 1,1,1-trichloroethane in Swiss mice. These data suggest that the reinforcing effects of abused inhalants can be studied using i.v. self-administration procedures.

Spark Ignition Characteristics of Monodisperse Multicomponent Fuel Sprays

Abstract This study experimentally investigated the spark ignition characteristics of monodisperse bi-component (n-heptane, C7/n-decane, C10rpar; sprays. Spray droplet diameters tested were 38,44, and 49 urn. Particular concerns were on the effects of species proportion and droplet size on the minimum ignition energy. The results indicate that minimum ignition energies increase with increasing droplet diameter for all the bicomponent fuels with different constituents, as for monocomponent fuels. The minimum ignition energies associated with 75%-C7/25%-C10bicomponent fuel sprays and pure C, sprays are nearly equal. Also, when the less volatile C7is the major species in the bicomponent fuels, the minimum ignition energies reduce considerably with the more volatile C, component increasing. It can therefore be inferred that mixing a certain amount of low-quality nonvolatile fuels into volatile fuels may not degrade the ignition characteristics of the fuel sprays, and blending a small amount of volatile fuels ...

The dynamics of flash fires involving flammable hydrocarbon liquids.

Victims of fires are sometimes discovered to have less-than-lethal levels of carbon monoxide (CO) in the blood and no significant antemortem fire damage. Such occurrences are often linked to flash fires involving volatile hydrocarbon fuels. In this study, the dynamics of hydrocarbon fuel fires are examined, and the results of fullscale room tests ignited with small (< 2 L) quantities of flammable liquid are found to confirm the theoretical predictions. These tests showed that flame plumes with temperatures of 500-975 degrees C were produced above flammable liquids. Ignition of their vapors in a carpeted room produced a very short-lived flash of fire throughout the room, followed by intense flames in a layer above the floor approximately 1 m deep, which quickly degenerated to isolated pools of low flames. Combustion of hydrocarbon vapors in a room caused oxygen levels to drop below 8.5% in < 100 s, while causing carbon dioxide (CO2) levels to increase to 12-16% whether the door to the room was open or closed. Production of CO trailed maximum CO2 production by 15-30 s. A victim exposed to such a fire may collapse from extreme heat (aided by the water vapor created by the combustion of hydrocarbons), weakened by oxygen deprivation, before CO inhalation becomes a significant factor.

Nitrogen chemistry in FBC with limestone addition

A laboratory study of NO and N2O formation from limestone-catalyzed HCN oxidation under fluidizedbed combustion (FBC) conditions is reported. The experiments include the influence of NO and O2 on HCN oxidation over calcined limestone, formation of CaCN2 by reaction between HCN and calcined limestone, and oxidation of CaCN2 and simultaneous HCN oxidation and sulfation of the limestone in the presence of NO. For oxidation of HCN over calcined limestone at O2 concentrations of about 5000 ppmv or more, NO is formed with a selectivity of 50–60%. At a temperature of 1025 K, the selectivity for N2O formation exhibits a maximum at an O2 concentration of 1000–2000 ppmv. The presence of NO in the inlet gas enhances the formation of N2O. The selectivity for NO and N2O decreases and increases, respectively, with increasing degree of sulfation of the limestone. The results from the present work and from the literature are used to discuss how limestone addition influences the nitrogen chemistry in FBC. The results indicate that (1) the NO emission decreases for low volatile fuels such as pet coke because NO is reduced by CO over the calcinel limestone; and (2) for medium- to high-volatile fuels, the NO and N2O emission increases and decreases, respectively, because calcined limestone catalyzes the oxidation of volatile nitrogen (HCN and NH3) to NO and the decomposition of N2O. For large CFBCs, limestone has only a small effect on N2O. This is partly because a major part of the N2O emitted is formed in the upper part of the riser where the solids concentration is low and little N2O is destroyed heterogeneously.

The Influence of Automotive Diesel Back End Volatility and New Fuel Additive Technology on Regulated Emissions

Public concern over diesel emissions and air quality has provided the focus for testing the effects of changes to diesel fuel back end volatility using test fuels obtained by closely following real refinery practice and new fuel additive technology. On a typical European city bus engine, the increase in 95 per cent distillation temperature has no overall effects on regulated emissions; conversely, particulate emissions can be controlled by new fuel additive technology.

Combustion studies of coal derived solid fuels by thermogravimetric analysis: III. Correlation between burnout temperature and carbon combustion efficiency

Burning profiles of 35–53 μm size fractions of an Illinois coal and three partially devolatilized coals prepared from the original coal were obtained using a thermogravimetric analyzer. The burning profile burnout temperatures were higher for lower volatile fuels and correlated well with carbon combustion efficiencies of the fuels when burned in a laboratory-scale laminar flow reactor. Fuels with higher burnout temperatures had lower carbon combustion efficiencies under various time-temperature conditions in the laboratory-scale reactor.

Effect of fuel properties on spray combustion.

The effects of fuel properties on the blow-off limit, the flame stability, the temperature distribution and emissions in a swirl type combustor were studied. The fuels used were gasoline, kerosene, and heavy oil. Gasoline and heavy oil were used as representing the most and the least volatile fuels, respectively. The momentum flux and the Sauter mean diameter of the issuing sprays of the three fuels were controlled to have the same value.For all fuels used in this paper, the fuel flow rate of blow-off limit decreased with increasing swirl strength. Under weak swirl, the fuel volatility had a greater effect on the blow-off limit than under strong swirl where the recirculation zone had a greater effect on flame stability. Emissions of soot and NOx had high values in the heavy oil flame and low values in kerosene flame. The exhaust soot emission increased by increasing the swirl strength of the flow for all three fuels.

A parametric exploration of the dynamic behavior of flame propagation in planar sprays

An exploration of the dynamic nature of flame propagation in planar sprays at ambient conditions has been performed. The parametric influence of three different levels of fuel-vapor concentrations (corresponding to three liquid fuel initial temperatures of 43°C, 25°C, and 15°C), two droplet sizes (305 and 407 μm), three fuel compositions (hexane, iso-octane, and a 50-50 by weight mixture of these fuels), and two levels of gas-phase turbulence intensity (17% and 2.5%) on the average speed of flame propagation and its fluctuations have been investigated using sequential photographic information. It was found that higher fuel-vapor concentrations, smaller droplet sizes, and more volatile fuels caused the average flame speed to increase while reducing its fluctuations. The effect of higher gas-phase turbulence intensity also caused the average flame speed to increase, but increased its fluctuations. Some of the observed phenomena can be qualitatively explained through the ignition process in a spray. When the presence of fuel vapor in the gas phase becomes significant due to the evaporation of droplets before the flame front, a premixed-gas type of ignition process prevails. At this condition the variations of average flame speed and its fluctuations may be explained through the effect of gas-phase equivalence ratio on the premixed-gas average flame speed. When the presence of fuel vapor in the flame front is reduced at high turbulence, a relay type of ignition process occurs. In this latter case, the increase of average flame speed and of flame speed fluctuations may be interpreted from the enhanced turbulent diffusion of thermal energy and from the turbulent fluctuations caused by the eddy transport phenomenon in the flow field, respectively.

Numerical study of multicomponent fuel spray flame propagation in a spherical closed volume

The flame propagation through a fuel spray-air mixture in a spherical geometry is investigated by means of a one-dimensional, unsteady mathematical model with a hybrid Eulerian-Lagrangian formulation. Finite-difference numerical schemes are employed, with non-uniform grid spacing and adaptive time step. The solution applies to the whole extent of the propagation, giving an accurate description of the ignition and flame propagation towards the wall, until combustion is completed. Multi-component and polydisperse sprays are considered. Emphasis is given to: presence and role of diffusion and premixed flames; the movement of the droplets due to expansion of hot gases and the resulting stratification; the effect of rapid vaporization of more volatile components; and the influence of the droplet size on droplet time history in a spray flame. More volatile fuels produce faster flame propagation. Nonuniform vapor fuel composition is generated due to the different volatilities of the components of the liquid fuel spray. Increasing the droplet size causes strong local deviation from the initially uniform equivalence ratio, due to the relative motion of the two phases; fuelrich and fuel-lean zones are present, and both premixed type and diffusion-type flames are observed at the same time.

Effects of additives on the microexplosion of carbon slurry droplets

Experimental investigations were conducted on the effects of volatile additives in inducing and intensifying the microexplosion of combusting carbon slurry droplets. The mixture explosion temperatures were determined, and a new droplet generator capable of producing small droplets of well-controll ed size was developed for the slurry fuel used. Agglomerate fragments produced through microexplosion were collected by using an impactor-type sampling probe and statistically analyzed. Results show that the fragment sizes follow the log-normal distribution, and that addition of 5% volatile miscible fuels to the carbon slurry can substantially reduce the mean fragment size. ARBON slurries hold potential as high-energy-d ensity fuels for application in volume-limite d propulsion sys- tems. The realization of this potential, however, has been com- plicated by the occurrence of particle agglomeration, which is usually associated with the burning of slurry fuels. That is, it has been demonstrated that the gasification mechanism for slurry droplets consists of two stages.14 In the first stage the liquid component is preferentially gasified, leaving behind an agglomerate of the particles. In the second stage this agglomer- ate subsequently heats up, ignites, and burns, spanning a pe- riod that can be substantially longer than that involving liquid gasification. Thus, the overall burning time of a slurry droplet is significantly longer than those corresponding to either a liquid droplet of similar initial size or the single particles by themselves. Two suggestions have been offered to reduce the severity of this agglomeration problem. The first is to coat the particles with suitable chemicals in order to prevent particle adhesion. The second is to break up either the slurry droplet before the agglomerate is formed or the agglomerate itself after it is formed. The present investigation is concerned with the second alternative, based on the phenomenon of droplet micro- explosion. Recent theoretical and experimental studies on the droplet combustion of multicomponent fuels have demonstrated that, for suitable components and composition, rapid gasification within the droplet interior can occur spontaneously, leading to intense internal pressure buildup with consequent catastrophic fragmentation of the droplet. The occurrence of microexplo- sion can be facilitated through several major factors.5 First, the volatility differentials between the more and less volatile com- ponents should be as wide as possible in that the less volatile component is needed to drive up the droplet temperature while the more volatile component is needed for the ease with which it will spontaneously gasify. Second, internal gasification is facilitated in the presence of particles, as in slurries, which provide heterogeneous nucleation sites; without such sites the

Effect of Fuel Properties on Spray Flame Characteristics

The effect of fuel properties on the temperature distribution and emissions in a swirl type combustor was studied. The fuels used were gasoline, kerosene and heavy oil. Gasoline and heavy oil were used as the most and the least volatile fuels respectively. The momentum flux and the Sauter mean diameter of the issuing sprays of three fuels were controlled to have the same value. The difference of the temperature distributions between the flames was prominent in a non-swirling flow condition. Emissions of soot and NOx took high values in the heavy oil flame and low values in the kerosene flame. Under the heavy oil combustion, exhaust emission of NOx increased by decreasing the swirl strength of the flow. Exhaust soot emission increased by increasing the swirl strength of the flow for all three fuels.

Flame Spread Rates Over Methanol Fuel Spills

Abstract Flame spread rates over pooled methanol and pooled gasoline were compared with flame spread rates over a porous surface saturated with these fuels. If the surface temperature was above the fuel flashpoint, the flame spread rate over a fuel-soaked porous surface was the same as for pooled fuel. Just below the flashpoint, flame spread was slower over a porous surface, since liquid flow was restricted. Far below the flashpoint, the flame spread over the porous surface more rapidly than over pooled fuel. For highly volatile fuels, such as methanol-5 percent isopentane mixture, the rate of flame spread depended on lime available for development of a flammable vapor layer over the liquid.

A Combustion of Lean Mixture with High Volatile Fuel Droplets

The effect of addition of high volatile fuel droplets to a lean mixture on a burning velocity, using an inverted cone burner, has been investigated. The used droplets are methanol-water, ethanol-water and soapbubbles enclosed propane-air or hydrogen-air mixtures. With these fuels, it is possible 1) to change the heat of combustion and the latent heat of fuel droplet without a significant change of droplet diameter, 2) to change the fuel vapour quantity around the droplet, and 3) to produce any concentration of gas cloud when the soapbubbles are used. The results obtained are follows : 1) The effect of addition of high volatile fuel droplets on the increase of burning velocity becomes large with an the increase of heat of combustion or a decrease of latent heat of the droplet ; 2) burning velocity increase when the soapbubble encloses a high burning velocity gas even if the latent heat of the soapsuds is greater than the heat of combustion ; and 3) the addition of droplets will increase the area of reacting zone of flame.

Effect of fuel volatility on spray combustion

The effect of fuel volatility on the lean blow-off limit and the temperature distribution in a swirl type combustor was studied. The flame stabilizing mechanism was also discussed. The fuels used were gasoline, kerosene and two types of heavy oils. Gasoline and heavy oil were used as the most and the least volatile fuels respectively. For all fuels used, the blow-off limit shifts to the lean side by increasing the swirl numberof the flow, i.e. the flame stability increases. With a weak swirl, the fuel volatility has the higher effect on the blow-off limit than with the strong one where the established recirculation zone has the higher effect on the flame stability. In the absence of a swirl, only one main reaction zone is formed inside the flame around its axis. With a strong swirl, two main reaction zones are formed for kerosene and heavy oil flames, but only one reaction zone for a gasoline flame.

Reaction of Thiophene with Sodium on Alumina. A Method for Desulfurization of Volatile Fuels

Reaction of Thiophene with Sodium on Alumina. A Method for Desulfurization of Volatile Fuels

Physical Mechanisms Governing the Oxidation of Volatile Fuel Nitrogen in Pulverized Coal Flames

Abstract The general problem of volatile fuel nitrogen oxidation in pulverized coal flames is considered. A review of field and pilot data indicates that physical mechanisms which control the local ratio of oxygen to volatile nitrogen are of paramount importance in determining nitrogen oxide emissions, This ratio can be viewed as being controlled both by the manner in which nitrogen evolution occurs during coal combustion and by mixing induced through aerodynamic or process changes. Theoretical results presented support the view that physical phenomena during coal particle volatilization can radically alter micro mixing between volatile nitrogen and air and are used to interpret a step change in fuel nitrogen conversion observed at very high temperatures. Data resulting from special experimentation on self-sustaining pulverized fuel flames are presented and interpreted in the light of fundamental physical mechanisms controlling contact between nitrogeneous species and oxygen. Unsolved problems and fruitfu...

Flame Stabilization of Low Volatile Fuels

Abstract Four chars, an ultra fine grind anthracite and a bituminous coal were burned in a special one-dimensional furnace. With a standard grind anthracite, the flame would not stabilize. The furnace used was a reconstruction of that used 10 years ago by Howard and Essenhigh (1965, 1966, 1967, 1967a). The principal observations were: flame front location determined as ignition distance below a stabilizing water-cooled tube bank; and wall temperature profiles. Effects of particle size, fuel/air ratio, cloud velocity and influence of a hot or cold boundary at the furnace bottom were investigated. Search for particle shattering at the flame front was negative. The fuels were found to split into two groups, either of high reactivity with flame fronts 4 or 5 cm below the tube bank, or low reactivity with flame fronts 40 to 50 cm below the tube bank. The high reactivity group included the bituminous coal and two of the chars thus supporting the contention that reactivity is not conferred by volatile matter per se. Reactivity is controlled by the gasification process not the parent coal. The conclusion, supported by appropriate N2 area and porosity measurements, is that high reactivity is primarily a function of internal surface. This is further supported by the critical importance of ultra fine grinding with the anthracite at one extreme and the insensitivity of behavior to particle size of the high reactivity fuels. Ignition times of the high reactivity fuels are in good agreement with simple radiation theory, but the theory does not account properly for the factor 5 to 10 difference in ignition times between the high and low reactivity fuels. This is under investigation in a theoretical model with results to be published elsewhere in due course

Computer Modelling of a Plane Flame Furnace Firing Low Volatile Fuels

Abstract A computer model of a plane flame furnace firing low volatile fuels has been modelled as a one dimensional flow problem between plane-parallel boundaries. The dominant element of the model is the radiation flux, with reaction included by adoption of experimental data for char particles cited in the literature (Field, 1969), modified by inclusion of a “reactivity” parameter, β that takes values from unity to zero. The objective of the modelling was to explain otherwise anomalous experimental values of ignition distance (50 cm) of low reactivity, low-volatile fuels (Cogoli et al., 1977) that simple radiation theory (Essenhigh and Csaba, 1963) could not account for although it did account for the ignition distance (5 cm) of high reactivity fuels. The more complete model described in this paper did account for ignition distances up to 50 cm with flame lengths and temperatures reasonably comparable to those found experimentally, when the reactivity parameter lay between 0.5 and 0.1. The results show t...

Composite solid propellant ignition - Ignition of ammonia and other fuels by perchloric acid vapor.

Abstract : The ignition of polyisobutene, polyurethane, polystyrene and polymethyl-methacrylate has been studied with oxygen gas and with perchloric acid vapour under the same experimental conditions. All these fuels ignited with perchloric acid vapour at 200-250C whereas ignitions with oxygen were only achieved at temperatures above 350C. Less volatile fuels such as carbon black, nylon and terylene also ignited with perchloric acid vapour at 200-250C. ignition of ammonia, methane, ethylene and isobutene was not achieved by perchloric acid vapour in the absence of a surface at 200-250C. In the presence of a surface the order of decreasing ignitability was ammonia, isobutene, ethylene, methane. Cupric chromate and ferric oxide were effective catalysts in the ignition of gaseous fuels with perchloric acid vapour. Titanium dioxide, silica and alumina had no detectable effect. It is concluded that in ammonium perchlorate propellents the important reactions leading to ignition are heterogeneous rather than homogeneous, and that in a catalysed propellent the reaction of ammonia and perchloric acid on the surface of the catalyst is the significant reaction. The results are discussed in relation to current theories of the mechanism of the ignition of composite solid propellents containing ammonium perchlorate.

Rate of combustion from free surfaces of liquid hydrocarbons

The burning velocity of n-hexane and cyclohexane as related to the area of the burning fuel surface was studied using 10 open pans ranging from 0·22 to 11·94 in. in diameter. On the four larger pans fuel temperatures were also measured during the burning period at two depths below the surface. For small pans less than 5 in. in diameter burning velocity decreased with increasing pan size. For pans greater than 5 in. in diameter burning velocity increased with increasing pan size. Thus, there appear to be two burning regimes in the range of pan diameters tested, a laminar flow regime on small pans, and a transition flow regime on larger pans. This observation is in agreement with the experimental results reported by others for equivalent pan sizes burning less volatile hydrocarbon fuels.