Droplet kerosene

A minimum volatihty is frequently specified to assure adequate vaporization under low temperature conditions. It can be defined either by a vapor pressure measurement or by initial distillation temperature limits. Vaporization promotes engine start-up. Fuel vapor pressure assumes an important role particularly at low temperature. For example, if fuel has cooled to —40°C, as at arctic bases, the amount of vapor produced is well below the lean flammabihty limit. In this case a spark igniter must vaporize enough fuel droplets to initiate combustion. Start-up under the extreme temperature conditions of the arctic is a major constraint in converting the Air Force from volatile JP-4 to kerosene-type JP-8, the military counterpart of commercial Jet Al. 

With the oil/water/surfactant droplet system which was used, no investigations could be performed because of strong foaming. However, studies with water/kerosene emulsions are known from the literature. The results of Yoshida... 

The hydrodynamics of the moving drop are difficult to calculate, particularly the flow characteristics within the droplet itself. However, this technique is still used widely, because it is a simple and straightforward method. It was recently applied to study the stripping-extraction kinetics of Mn(II) in an aqueous-kerosene system [50,51]. The effect of anionic surfactants on the kinetics of extraction of lactic acid from an aqueous phase by Alamine 336 in a toluene phase was also studied by this technique [52]. 

A two-color pyrometer has been used along with the phase-Doppler anemometer to simultaneously measure the local velocity and size of kerosene droplets and the temperature of burning soot mantle in a swirl burner.[648] The measurements were conducted 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. The results showed that the maximum burning fraction of the droplets occurs adjacent to the region denoted as gas flame but the value ranges from 20 5 to 40 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. 

Images of pure JP-10 and the mixtures are shown in Figs. 5.2a to 5.2/. As shown in Figs. 5.2a to 5.2c, recorded at t = 0, 0.997, and 1.673 s, respectively, the kerosene droplet did not indicate internal vaporization until close to complete combustion. The situation changed when mixtures of kerosene with methylated PCU alkene dimer were used, as shown in Figs. 5.2d to 5.2/ for a 18% mixture. For the 18% mixture the first internal vapors appeared at 1 = 0.713 s (Fig. 5.2e) and indication of strong effervescence appeared at t = 1.23 s (Fig. 5.2/). 

These results indicate that the enthalpy associated with air (and also steam) has an effect on the resulting droplet size. A larger droplet size with preheated air than steam reveals that there must be effects other than just the enthalpy associated with steam. Some of the possible factors include viscosity and density differences between the gases, and that water contained in steam may become miscible under these conditions. In this case, the large differences in the boiling points between the two fluids (water and kerosene) may lead to disruptive breakup of the liquid fuel, even at 10 mm, via rapid heat transfer from the flame. 

The general method of procedure was to disperse a known volume pf parafl n in water with the aid of the soap. The average diameter of the kerosene emulsion droplets was determined by counting with the aid of a microscope and hemacytometer, from which the total interfacial area could be calculated. 

Abou-Ellail, M. M. M., Elkotb, M. M. and Rafat, N. M. (1978). Effects of fuel pressure, air pressure and air temperature on droplet size distribution in hollow cone kerosene sprays. Proc. 1st Inter. Conf. on Liquid Atomization and Spray Systems (ICLAS 78), Tokyo, 85-99. 

Emulsion flotation is analogous to carrier flotation. Here, small-sized particles become attached to the surfaces of oil droplets (the carrier droplets). The carrier droplets attach to the air bubbles and the combined aggregates of small desired particles, carrier droplets, and air bubbles float to form the froth. An example is the emulsion flotation of submicrometre-sized diamond particles with isooctane. Emulsion flotation has also been applied to the flotation of minerals that are not readily wetted by water, such as graphite, sulfur, molybdenite, and coal [623]. Some oils used in emulsion flotation include mixed cresols (cresylic acid), pine oil, aliphatic alcohols, kerosene, fuel oil, and gas oil [623], A related use of a second, immiscible liquid to aid in particle separation is in agglomeration flocculation (see Section 5.6.4). 

Undercooling is the driving force in freeze drying. An aqueous salt solution is introduced dropwise into an immiscible liquid (hexane or a petroleum fraction such as kerosene) cooled below 243 K. The individual droplets are frozen instantaneously and the solid particles are decanted or filtered. The frozen particles are then sublimed in a vacuum to obtain a homogeneous powder of fairly uniform particle size. Important parameters in freeze drying are the final temperature of the salt solution and the cooling rate. These can be controlled to some extent, but only on a small scale. Hence the method is not very suited for large-scale manufacture of catalysts. 

The emulsification efficiency can be increased by increasing surfactant concentration in the medium in fact, emulsion droplets find it difficult to disperse and tend to grow large at low concentrations of surfactant. Figure 6.12C shows the variation of droplet size (expressed as the Sauter diameter, 0/3 2) in a w/o water-in-kerosene emulsion at variable... 

Propane Fuel—Results and Discussion. Onuma (12) showed that in a kerosene spray flame, there is no evidence of droplet burning. The vapor cloud formed by evaporation of the droplets bums like a turbulent diffusion flame. A close relationship between kerosene spray flame and gaseous diffusion flames (using propane as the fuel) was provided. The results reported in this section are those obtained from the modulated swirl combustor using propane as the fuel. 

Measurements have been made of the combustion characteristics of an air blast kerosene spray flame and of droplet sizes within the spray boundary of isothermal sprays. Specific techniques were used to measure velocity, temperature, concentration, and droplet size. Velocities measured by laser anemometer in spray flames in some areas are 400% higher than those in isothermal sprays. Temperature profiles are similar to those of gaseous diffusion flames. Gas analyses indicate the formation of intermediate reactants, e.g., CO and Hg, in the cracking process. Rosin-Rammler mean size and size distribution of droplets in isothermal sprays are related to atomizer efficiency and subsequent secondary atomizer/vaporization effects. 

Air from the compressor enters the mixing chamber of the atomizer at sonic velocity and, after interaction with the liquid kerosene stream, emerges as a two-phase mixture, directed vertically upwards. The air flow from the annular stream forms a recirculation zone in the wake of the stabilizer disk. The flame is ignited by an external gas stream and subsequently bums independently as a flame in the open atmosphere. Droplets are initially confined to the air jet from the atomizer nozzle, but some of the finer droplets are taken up by the reverse flow of the stabilizer disk recirculation zone. Previous studies on spray combustion and details of atomizer design are reviewed by Chigier (J). 

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