Kerosene Droplets Research Articles

Performance of Flammability and NOx Emission in Premixed Oil Burner Using Ultrasonic Atomization.

In the combustion of low vapor pressure liquid fuel, it is necessary for instantaneous ignition to preheat the liquid fuel evaporator at any required time. For example, in the kerosene vaporizing type boiler for home use, electric power is consumed in the preheating kerosene vaporization to supply hot water, even on standby. To avoid the preheating process by electric power during the standby period, the technology that can vaporize liquid fuel instantaneously needs to be developed. From this viewpoint, the application of the ultrasonic atomization was proposed to ignite liquid fuel without any heating process. Similar trials had already been done but no stabilized combustion was accomplished by ultrasonic atomizing, using an MHz frequency.In this work, a kerosene pre-mixed burner equipped with a 1.7-MHz ultrasonic oscillator was manufactured and the characteristics of the atomization of kerosene, stable combustion region and NOx emission on this ultrasonic atomization burner are examined. The relatively quick ignition with a few seconds delay was realized. The atomization of kerosene was obtained at the rate of 0.75 g/min, which is proportional to the time and the average kerosene droplet size, 3.1 μm, produced by 1.7 MHz ultrasonic oscillation. 0.54 kW load was obtained by using this combustor. Stable combustion was obtained around 0.7 in the equivalence ratio. The stable combustion was defined as [CO]/[CO2] x emission (O2 0% base) is accomplished in the stable combustion region as it can provide the balance between both primary and secondary air flow rates.

Fundamental study of reactive oily-bubble flotation

A novel concept of reactive oily bubbles (i.e., bubbles covered by a thin layer of oil containing oil-soluble collectors) as a carrier in flotation is proposed. In addition to the role of fine particle agglomeration by oily films, the surface properties of air bubbles coated with a thin oil film can be better controlled for the desired selectivity by adding certain types and concentrations of water insoluble collectors into the oil phase. Oily bubbles attain a much higher contact angle than air bubbles, ensuring a strong collecting power, favorably for floating both coarse and fine particles. The reactive oily bubble flotation can eliminate the addition of collector to the aqueous phase, avoid undesired synergetic interactions among collectors, activators, depressants and dispersants present in slurry, minimize undesired activation of gangue particles and significantly reduce the amount of collectors needed. The electrokinetics of kerosene droplets in aqueous collector solutions was measured as a function of solution pH. The results clearly showed that the surface charge and hence the surface properties of oil droplets can be finely tuned by controlling the type of the collectors to suit the desired flotation needs. The attachment of collector-containing oily bubbles on silica, sphalerite and galena surfaces was investigated with contact angle measurement. The concept of using reactive oily bubble to achieve selective flotation was demonstrated in microflotation tests.

Experimental and numerical investigation of kerosene flammability

In an attempt to contribute to aircraft safety, it is fundamental to define the explosions conditions of kerosene vapor in an aircraft tank. Flammability properties of kerosene F-34 and F-35 have been determined experimentally. The flash point and the vapor pressure have been measured by means of an appropriate apparatus. A first analysis of the composition by GC-MS analysis shows four essential compounds: decane, dodecane, 1,2,4 trimethylbenzene and butylcyclohexane. The evolution of maximum pressure is compared with the theoretical values obtained with a simple model based on the theory of molecule collisions. A simple modelling has been developed as part of a novel study on ignition and combustion of classical propulsive powders and transposed to liquid kerosene droplets in order to predict the main characteristics of these explosions in a closed vessel.

Dynamics of an Airblast Spray in a Double Swirled Stabilized Flame

The present study aims to provide experimental data describing the characteristics of kerosene droplets in a swirl-stabilized spray flame. The fuel injector is a prefilming airblast atomizer where the fuel is sandwiched between two co-swirling turbulent air streams. Measurements are obtained by application of the phase Doppler anemometry technique for a simultaneous measurement of a droplet's size and velocity. In order to develop a full understanding of the aerodynamic and mixing processes of the droplets, spatially resolved information (i. e., liquid flux and concentration, velocity fluctuations of the both phases) are also determined. The measured mean tangential velocity component indicates that the rotating gas flow is the combined forced-free vortex. From determination of the Sauter's mean diameter, a strong separation of particles is observed, resulting in a radial increase of the particles' size. This effect is a result of the strong spreading of the swirling jet and the action of centrifugal forces. The liquid flux is closely associated with the number density change of the droplets. The maximum liquid flux is situated at the edge of the jet, while only a small amount of liquid is transported by the smaller droplets at the central part of the burner. Further downstream, its distribution is found to be V-shaped with an inclination angle of 85°. It is uniform in the center and gradually increases with radial distance to reach a peak followed by a decrease towards the outer edges of the spray. The concentration of liquid is small in the central region and increases towards the edge of the jet. The centrifugal effect is again evident since the liquid fuel's concentration is larger at the edge of the spray.

Oil agglomeration and its effect on beneficiation and filtration of low-rank/oxidized coals

Low-rank/oxidized coals respond poorly to oil agglomeration. Emulsification of kerosene in the presence of surfactants dramatically reduces the size of the kerosene droplets, lowering the consumption of kerosene needed to agglomerate oil down to 0.25–0.5%. Surfactants can also entirely change the interaction between oil droplets and coal particles. Consequently, kerosene cationic emulsions can efficiently agglomerate oxidized coal particles. The agglomerates obtained in such a process can still be recovered by screening.

96/03547 Flotation of oil-aggiomerated coal for ash and pyrite removal

Low-rank/oxidized coals respond poorly to oil agglomeration. Emulsification of kerosene in the presence of surfactants dramatically reduces the size of the kerosene droplets, lowering the consumption of kerosene needed to agglomerate oil down to 0.25–0.5%. Surfactants can also entirely change the interaction between oil droplets and coal particles. Consequently, kerosene cationic emulsions can efficiently agglomerate oxidized coal particles. The agglomerates obtained in such a process can still be recovered by screening.

Production of oil/water type uniformly sized droplets using a convergent AC electric field

The authors proposed a new method to produce uniformly sized insulating liquid droplets (such as kerosene or plastic monomer) in immiscible liquid media (distilled water) by means of an applied convergent electric field generated using AC or pulsed voltage. The disintegration mechanism of the liquid column was observed precisely using video images and still photographs. Kerosene droplets with an essentially uniform diameter ranging from 100 to 250 /spl mu/m were produced synchronously with the applied AC frequency using a nozzle diameter of 100 /spl mu/m. When the flow rate of the co-flowing liquid surrounding the oil-phase liquid jet was increased, the synchronous frequency became higher and the size of the resulting droplets was decreased due to the elongation of the liquid jet. The disintegration mechanism is most likely the forced oscillation of the liquid jet stimulated by each cycle change of the applied voltage. The droplet size can be widely controlled by varying the AC frequency, nozzle diameter, liquid flow rate and velocity ratio between the oil-phase and co-flowing water.

Surface Energy and Induction Time of Fine Coals Treated with Various Levels of Dispersed Collector and Their Correlation to Flotation Responses

Separation of fine coal in froth flotation relies upon the wettability difference between the coal-rich and mineral-rich particles in the aqueous solution. Two methods were used to measure the wettability of six ranks of coal as well as coal samples treated with various levels of dispersed collector in aqueous solution. Wettability was determined by measuring the distribution of critical wetting surface tension, i.e., surface energy, using the film flotation technique and by measuring the induction time, i.e., bubble-particle attachment time, of the material. The wetting of coal particles is strongly dependent upon the coalification processes and can be affected by ash content. For anthracite coal with a high ash content, very high surface energy and intermediate induction time were measured, but intermediate floatability with a very good ash rejection was obtained. Sub-bituminous coal with low mineral inclusion was found to have a relatively low surface energy, and thus a high floatability, but very poor selectivity was observed, which was reflected in lengthened induction time. When dynamics of flotation behaviors are involved, flotation results can be better interpreted by induction time. For dispersed collector-treated coal samples, an increase in collector dispersion (i.e., a decrease in kerosene droplet size), by direct liquid collector mechanical agitation, ultrasonic energy emulsification, or atomization, caused decreases in surface energy and induction time and closely matched the increase of flotation recovery and selectivity. With similar particle density, mineral liberation conditions, and particle size, the induction time was found to be closely related to the mean critical surface tension for untreated coal samples and for HV-bituminous coal samples treated by various levels of dispersed collector.

Simultaneous measurement of droplet velocity and size and flame mantle temperature by phase Doppler anemometry and two-colour pyrometry

Phase Doppler anemometry and a two-colour pyrometer have been combined to provide simultaneous, local measurements of kerosene droplet velocity and size and temperature of the burning soot mantle. Preliminary measurements within the flame brush that develops in the shear layer of a swirl-stabilized, gas-supported kerosene flame with a swirl number of about 0.19 and potential heat releases of 10.6 and 15.5 kW, respectively, are described. The results show that the maximum burning fraction of the droplets occurs adjacent to the region denoted as gas flame but the value ranges between 20+or-5 and 40+or-5% depending on the axial station, and decreases sharply across the shear layer. The flame mantle temperature was found to be independent of droplet diameter, which agrees with previous results in the literature. The likely experimental errors are assessed in the context of the measurements in the swirl burner.

Mass flux, mass fraction and concentration of liquid fuel in a swirl-stabilized flame

Mass flux, mass fraction and concentration of kerosene droplets have been measured by a phase-Doppler instrument in a swirl-stabilized burner during inert and reacting flow. In the reacting flow, the flame was supported by natural gas added through the fuel stalk, while the kerosene was added to and atomized by the combusting air. The bulk mean velocity of the combustion air was 30.4 m/s, corresponding to a Reynolds number of 30,000, and the swirl numbers were 0.48 and 0.29, respectively, upstream and downstream of the kerosene injection. The equivalence ratios were 0.45 and 2.11 for the natural gas and the kerosene, respectively. The results show that the minimum swirl necessary for flame stability caused fuel to centrifuge from the region of combustion, so that only 8 kW of energy could be released out of the available 37.4 kW of the kerosene fuel. An important conclusion is that an optimum swirl number will exist with every atomization and burner arrangement of a liquid-fuelled flame and will be different from that associated with the corresponding gas-fuelled flame. The measurement techniques appropriate to regions where the flow instantaneously reverses are described and the existence of large droplets, which moved towards the injector inside the recirculation zone and supplied fuel to the base of the flame, are explained in terms of a “fountain effect” based on the mean drag between the gas phase and the droplets. Sources of uncertainties of the mass flux and concentration measurements with the phase Doppler instrument are considered in detail.

水中における油滴へのＣａＣＯ３粒子の付着に関する研究

Adhesion of quartz particles (size 5-10μm) to various oil droplets (kerosene, hydrocarbons) in aqueous surfactant-free solutions was studied. Electrokinetic behavior of quartz particles and oil droplets, recovery of quartz with the oil phase and contact of oil drops with quartz surfaces in the aqueous solutions were examined. The results are summarized as follows:(1) In the aqueous phase of pH3, hydrophilic quartz particles adhered to kerosene droplets, whereas kerosene drops did not contact with quartz surfaces.It was suggested that, on this condition, the negatively charged quartz particles and the positively charged kerosene droplets coagulate across water layers.(2) In CaCl2 solution of pH 11.5, where quartz particles adhered to droplets of hydrocarbons as well as those of kerosene, oil drops were found to contact directly with quartz surfaces. In this case, water layers between quartz particles and oil droplets should be removed by specific interaction, probably due to specific adsorption of [CaOH]+ on both quartz and oil surfaces.

Effect of Humic Acids on Coal Flotation Part I. Coal Flotation Selectivity in the Presence of Humic Acids

Humic acids, products of profound coal oxidation, were shown to strongly affect coal floatability. These anionic polyelectrolytes make the zeta potential values of kerosene droplets as well as coal particles much more negative. Coal flotation selectivity in the presence of a humic acid has been shown to depend upon the time of conditioning with the humic acid and an oily collector (kerosene or fuel oil). After conditioning both humic acid and kerosene (or fuel oil) with coal for a few minutes, subsequent smaller additions of kerosene (or fuel oil) leads to a drastic increase in recovery at much better selectivity.

Aerosol Wind Tunnel for Vector Insecticide Evaluation1

The droplet-size distribution patterns of five solvents injected under controlled pressures and into controlled wind velocities were measured with a laser in a laboratory wind tunnel used to evaluate insecticidal aerosols. Each solvent was injected through an atomizer at one of four air pressures into a constant velocity air stream (2.5 m/sec). Air pressures of 31.0 and 41.3 kPa produced the smallest droplet-size distribution patterns; >75% of the acetone, fuel oil, and kerosene droplets atomized at 31.0 kPa were <10 μm, whereas water and methanol required 41.3 kPa for similar patterns. Resmethrin as a 1% solution in each solvent had little effect on altering the patterns. Insecticide evaluation and cleanup time can be greatly reduced when the wind tunnel is used instead of individual topical applications or Peet-Grady tests.

Calculation of the Detonation Velocity of a Mixture of Liquid Fuel Droplets and a Gaseous Oxidizer

Abstract The calculation of the detonation velocity in monodisperse mixtures of kerosene droplets and gaseous oxygen is described. The stationary Z-N-D detonation wave model is used. It is proposed that only that part of the fuel, which has been shattered by the high speed gas flow can react instantaneously at the C-J plane. The part of the fuel which burns behind the C-J plane does not have any effect on the detonation wave velocity. The C-J plane position is determined by the ignition time delay. The amount of fuel supporting the detonation was calculated using experimentally determined expressions for the variation of the velocity and the mass of the shattering droplets. Results of the calculations show good agreement with published experimental results.

Theoretical and experimental study of cylindrical shock and heterogeneous detonation waves

A simplified theory of blast initiation of detonations in clouds of fuel in gaseous or droplet form is developed and agrees with the experiments described below. The flow is at first dominated by the strong blast wave but transition from blast to detonation behavior occurs near a critical radius r∗ where the blast energy and the heat of combustion contained in r < r∗ are equal. The complex flow in this transition region cannot be determined analytically. In the simplified theory the details of the transition region are ignored but the flow is represented by the self-similar solution for a strong blast wave for r < r∗ and by the self-similar detonation solution for r > r∗. The development of a sectored shock tube to study cylindrical shock waves and two-phase detonations is described. Data are presented for shock waves as well as for blast initiated detonations of a monodisperse spray of 400 μ kerosene droplets in air at standard conditions. Two regimes of propagation were established experimentally: (1) the subcritical energy regime, where decoupling of shock and reaction zone results in a strong blast wave type decay and, (2) the supercritical energy regime, where the initially overdriven cylindrical detonation decays, at some critical radius, to its Chapman-Jouguet state. Experimentally determined critical radii and steady-state detonation velocity agree very well with theoretical predictions. Detonation velocity was found to be constant at the plane C–J value for radius greater than the critical radius.

Investigation of the detonation of aluminum powder-oxygen mixtures.

It is shown that mixtures containing 48 to 64% (by mass) fine aluminum powder in oxygen are detonable. In 26.4-mm-diam tubes the detonation induction distances of these mix- tures are less than 1.6 m; they decrease with increasing aluminum concentration. The det- onation wave speeds for the lean mixtures are approximately 1550 m/sec and decrease slightly with increasing amounts of aluminum in the mixture. The pressures behind the detonation waves were found to be approximately 31 atm for the mixtures examined. The measured detonation speeds and pressures are approximately 9 and 14%, respectively, below the theo- retical values. This deviation is probably caused by incomplete combustion of the alumi- num particles. The detonation waves of these mixtures show the typical characteristics of spin. LTHOUGH the existence of detonation waves in solid fuel-gaseous oxidizer mixtures has been questioned by some researchers, there appears to be evidence that detonation waves can exist in heterogeneous mixtures. When high- energy shock waves were passed through mixtures .of kerosene droplets and gaseous oxidizer (Kling and Maman1), tion waves were obtained with a stoichiometric mixture only after reflection of the incident shock. The measured speeds agreed with the calculated ones. Cramer2 observed detona- tion-like waves propagating through DECH (diethylcyclo- hexane, CioH20) fuel spray-oxygen mixtures. Eraser3 was able to detonate both octane-oxygen and benzene-oxygen mixtures (also initiated with high-energy shock waves). Nicholls et al. 4 also reported detonation-like waves in heterogeneous DECH-oxygen mixtures. Although these observations support the theory that liquid-gas mixtures detonate, they do not permit us to predict the behavior of solid-fuel systems. The combustion of metal powders with gaseous oxidizers was studied by Hartmann and Greenwald.5 They reported that aluminum dust can be ignited easily in air, oxygen, carbon dioxide, and under certain conditions it can react even with nitrogen. Cassel et al. 6 measured the burning velocities of powdered aluminum in various oxygen-nitrogen atmo- spheres. For a 70% oxygen, 30% nitrogen atmosphere, they reported tube burning speeds of approximately 40 cm/sec. Bunsen-burner flame speeds of aluminum powder-oxygen mixtures have been measured previously (not reported) at this laboratory and were found to be approximately 25 cm/sec. Mixtures having low burning speeds are somewhat difficult to detonate.

The evaporation of sprays

The rate of evaporation of an aircraft spray of kerosene droplets in the atmosphere has been measured, and was found to approximate to the theoretical estimates.

Instruction in mechanical engineering

The incident shock wave strongly affects the transversal injection field in cold kerosene-fueled supersonic flow, possibly due to its affecting the interaction between incoming flow and the fuel through various operation conditions. Optimum selection of fuel injection parameters indicates optimum interaction between incoming flow and fuel. Based on three dimensional Couple Level Set & Volume of Fluids (CLSVOF) approach, a detailed Computational Fluid Dynamics model of a cold kerosene-fueled scramjet combustor is developed in this study. Next, the effects of various injection angles on the interaction between incident shock wave and transversal cavity injection are addressed. The injection angles are specified from 45̊ to 135̊ in 45̊increments when other operation parameters, i.e. the injection diameter, velocity and pressure drop are all constant. The CLSVOF-based predictions are focused on penetration height, span-wise expansion area, angle of shock wave and sauter mean diameter (SMD) distribution of the kerosene droplets. Our findings show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet all increased with the injection angle, and that the kerosene droplets are more prone to breakup and atomization at the outlet of the combustor for the injection angle of 45̊. This study demonstrates the effectiveness of CLSVOF modeling for better understanding of kerosene-fueled supersonic mixing and scramjet combustor design improvement.