Atomization viscosity effects

In fan spray atomization, the effects of process parameters on the mean droplet size are similar to those in pressure-swirl atomization. In general, the mean droplet size increases with an increase in liquid viscosity, surface tension, and/or liquid sheet thickness and length. It decreases with increasing liquid velocity, liquid density, gas density, spray angle, and/or relative velocity between liquid and surrounding air. 

The steep thermal gradient along the tube means that any variation in the sample position (e.g. because of pipetting, or spreading due to surface tension and viscosity effects) will alter the atomization peak shape. Peak area integration will help to minimize this problem, as will a rapid heating ramp and isothermal operation (see Sections 3.6.2 and 3.6.3). 

The chlorine atom cage effect was used as a highly sensitive probe for studying the effect of viscosity and the possible role of solvent clusters on cage lifetimes and reactivity for reactions carried out in supercritical fluid solvents. The results of these experiments provide no indication of an enhanced cage effect near the critical point in SC-CO2 solvent. The magnitude of the cage effect observed in SC-CO2 at all pressures examined is well within what is anticipated on the basis of extrapolations from conventional solvents (Fletcher et al., 1998). 

The application of atomic spectroscopy methods to the analysis of petroleum products is important to the oil industry. All oil samples must be prepared in solution form and be at a concentration so as to be detected to quantify all metals of interest with accuracy and precision. Solutions containing petroleum products in organic solvents may be measured directly or with the use of internal standards to correct for viscosity effects. It is important that the selected solvent dissolves the oil and products and does not cause erratic flickering of the plasma, or quenches it. It is also important that the same solvent can be used to prepare calibration standards. The following methods are common sample preparation methods for metal analysis of crude and lubricating oils. 

Tanko, et al. utilized the chlorine atom cage effect as a highly sensitive probe for studying the effect of SCF viscosity and the possible role of solvent clusters on cage lifetimes and reactivity [50,51]. These experiments were con-... 

A. M. Binnie, Viscosity effects in the nozzle of a swirl atomizer. Quart. J. Mech. Appl. Math. 8,394(1955). 

In the data for the shear viscosity, the heavy atom substitution effect is clearly observed with the same trend for any ILs the heavier atom substitution gives a lower shear viscosity. As mentioned previously, this effect is the opposite of that for common neutral molecular liquids (e.g., 77(fluorobenzene) 0.550 cP < 77(chlorobenzene) 0.753 cP < T bromobenzene) 1.074 cP and 77(diethyl ether) 0.224 cP < 77(diethyl sulfide) 0.442 cP at 298 K (Lide, 2008)). In... 

On the other hand, the trend in the surface tension by the heavy atom substitutions is somewhat complicated in comparison with that in the shear viscosity. As listed in Table 1, the surface tension becomes slightly smaller with the heavier element substitution in the aromatic and nonaromatic "cations" but becomes larger with the heavier element substitution in the "anions". There is an inverse correlation between surface tension and molar volume in molten salts, including ILs (Jin et al., 2008). The change in surface tension for the ILs by the heavy atom replacement in the cation is well explained by the empirical scheme. However, the feature in the anions is evidently the opposite of the predicted heavy atom substitution effect on the surface tension. 

In this chapter, we provided an overview of the heavy atom substitution effects of the constituent ions in some ILs on the static properties such as liquid density, shear viscosity, and surface tension, along with the effects on the interionic vibrational dynamics. With respect to the static properties, we can summarize the heavy atom substitution effects in the ILs as follows. 

Equation 14 indicates that Hquid pressure has a dominant effect in controlling the mean droplet sizes for pressure atomizers. The higher the Hquid pressure, the finer the droplets are. An increase in Hquid viscosity generally results in a coarser spray. The effect of Hquid surface tension usually diminishes with an increase in Hquid pressure. At a given Hquid pressure, the mean droplet size typically increases with an increase in flow capacity. High capacity atomizers require larger orifices and therefore produce larger droplets. 

The principal parameters affecting the size of droplets produced by twin-fluid atomizers have also been discussed (34). These parameters include Hquid viscosity, surface tension, initial jet diameter (or film thickness), air density, relative velocity, and air—Hquid ratio. However, these parameters may have an insignificant effect on droplet size if atomization occurs very rapidly near the atomizer exit. 

Both effects can produce coarser atomization. However, the influence of Hquid viscosity on atomization appears to diminish for high Reynolds or Weber numbers. Liquid surface tension appears to be the only parameter independent of the mode of atomization. Mean droplet size increases with increasing surface tension in twin-fluid atomizers (34). is proportional to CJ, where the exponent n varies between 0.25 and 0.5. At high values of Weber number, however, drop size is nearly proportional to surface tension. 

Droplet size, particularly at high velocities, is controlled primarily by the relative velocity between liquid and air and in part by fuel viscosity and density (7). Surface tension has a minor effect. Minimum droplet size is achieved when the nozzle is designed to provide maximum physical contact between air and fuel. Hence primary air is introduced within the nozzle to provide both swid and shearing forces. Vaporization time is characteristically related to the square of droplet diameter and is inversely proportional to pressure drop across the atomizer (7). 

In the 1960s materials became available which are said to have been obtained by chlorination at lower temperatures. In one process the reaction is carried out photochemically in aqueous dispersion in the presence of a swelling agent such as chloroform. At low temperatures and in the presence of excess chlorine the halogen adds to the carbon atom that does not already have an attached chlorine. The product is therefore effectively identical with a hypothetical copolymer of vinyl chloride and symmetrical dichloroethylene. An increase in the amount of post-chlorination increases the melt viscosity and the transition temperature. Typical commercial materials have a chlorine content of about 66-67% (c.f. 56.8% for PVC) with a Tg of about 110% (c.f. approx. 80°C for PVC). 

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