- Email: [email protected]
The atomization of water–oil emulsions
Experimental Thermal and Fluid Science 33 (2009) 955–962
Contents lists available at ScienceDirect
Experimental Thermal and Fluid Science journal homepage: www.elsevier.com/locate/etfs
The atomization of water–oil emulsions L. Broniarz-Press *, M. Ochowiak, J. Rozanski, S. Woziwodzki Department of Chemical Engineering and Equipment, Faculty of Chemical Technology, Poznan University of Technology, Pl. M. Sklodowskiej-Curie 2, PL 60-965 Poznan, Poland
a r t i c l e
i n f o
Article history: Received 10 March 2009 Received in revised form 9 April 2009 Accepted 9 April 2009
Keywords: Atomization Visualisation Emulsion Spray Sauter mean diameter
a b s t r a c t The paper presents the results of experimental studies on atomization of the emulsions flowing through twin-fluid atomizers obtained by the use of the digital microphotography method. The main elements of the test installation were: nozzle, reservoir, pump and measurement units of liquid flow. The photographs were taken by a digital camera with automatic flash at exposure time of 1/8000 s and subsequently analyzed using Image Pro-Plus. The oils used were mineral oils 20–90, 20–70, 20–50 and 20–30. The studies were performed at flow rates of liquid phase changed from 0.0014 to 0.011 (dm3/s) and gas phase changed from 0.28 to 1.4 (dm3/s), respectively. The analysis of photos shows that the droplets being formed during the liquid atomization have very different sizes. The smallest droplets have diameters of the order of 10 lm. The experimental results showed that the changes in physical properties of a liquid phase lead to the significant changes in the spray characteristics. The analysis of the photos of water and emulsions atomization process showed that the droplet sizes are dependent on gas and liquid flow rates, construction of nozzle and properties of liquid. The differences between characteristics of atomization for water and emulsions have been observed. Analysis of photos on forming the droplets in air–water and air-emulsions systems showed that droplets are bigger in air-emulsion system (at the same value of gas to liquid mass ratio). The values of Sauter mean diameter (SMD) increased with increase of volume fraction of oil in emulsion. The droplet size increased with emulsion viscosity. Ó 2009 Elsevier Inc. All rights reserved.
1. Introduction The atomization of emulsions is wide-spread process in many branches of industry, for instance, in power engineering and combustion engines, in engineering industry and in agriculture. The cooling agent for machine elements, fuel oil, pesticides and milk can be emulsions [16]. In the food industry, oils are used to carry oil-soluble colours, flavours and nutrients that are coated onto the outside of the food. However, many colours, flavours and nutrients are water-soluble, which require water to be the carrier. Emulsions, which carry both oil and water-soluble additives to the food at the same time, are also commonly sprayed [1]. The studies of emulsions atomization were also directed to improve the combustion performances of emulsions as fuels in furnaces for local power generation [12,21,26,29]. The spray characteristics are: spray angle, covering of surface, droplet size distribution, droplet velocity distribution, volume distribution pattern, spray structure, the structure of individual droplets. These basic parameters are described by Lefebvere [13], Orzechowski and Prywer [19] and some other authors. The measurement technique was described by Lefebvere [13], Orzechowski
* Corresponding author. Tel.: +48 61 6652789; fax: +48 61 8103003. E-mail addresses: [email protected], [email protected] (L. Broniarz-Press). 0894-1777/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.expthermflusci.2009.04.002
and Prywer [19] and Liu [14]. Measurements of droplet size distribution are routinely made by the use of optical techniques. The prediction of droplet size distributions is accomplished through empirical correlations accounting for liquid properties, atomizer design and fluid flows [13]. The most relevant properties of a liquid are surface tension, viscosity, and density [3,11]. A typical spray includes a wide range of droplet sizes. Some knowledge of the droplet size distribution is helpful in evaluating process applications in sprays, especially in calculations of heat or mass transfer between the dispersed liquid and the surrounding gas. SMD is the diameter of that drop whose volume/surface ratio value is the same as the arithmetic mean of volume/surface values on the total number of drops belonging to the sample spray under examination. The SMD is often of use in applications where the active surface or surface area is important, e.g. atomization, catalysis or combustion. The SMD is calculated as the ratio as follows:
P i
SMD ¼ P i
3
ni di
2
ni di
ð1Þ
Many different correlations for SMD have been presented in literature. The correlation proposed by Nukiyama and Tanasawa [18] is the most often in use. The investigation of atomization process in a plain-jet atomizer resulted in the empirical equation for the SMD:
956
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
SMD ¼
0:5 2 0:25 1:5 0:585 r lL QL þ 53 uR qL rqL QG
ð2Þ
This equation was obtained at diameters of water outlet changed from 0.2 to 1.0 mm and nozzle outlet diameters from 2 to 5 mm. The equation applies to a range of air velocities from 60 to 340 m/s and values of gas to liquid mass ratio (GLR) from 1 to 14. Hereby GLR is defined as follows:
GLR ¼
_G m _L m
ð3Þ
_ G and m _ L are mass flow rates of atomizing gas and liquid, where m respectively. The correlation does not take into account the diameters of atomizer as well as the density and viscosity of gas. Rizkalla and Lefebvre [24] investigated atomization process in plain-jet air-blast nozzles and obtained the following empirical equation for the SMD:
1:70 _ L Þ0:33 ðrm 1 1þ 0:37 0:30 GLR uR qL qG 1:70 2 0:5 l dout 1 þ 0:13 L 1þ GLR rqL
SMD ¼ 0:95
ð4Þ
From studies carried out on the atomization of water, with air as the atomizing fluid, Sakai et al. [25] derived the following experimental correlation for SMD: 0:75
SMD ¼ 14 106 dout
_L m _G m
0:75
0:75
¼ 14 106 dout ðGLRÞ0:75
ð5Þ
The equation presented above applies to a range of liquid flow rates from 0.008 to 0.028 kg/s and values of gas to liquid mass ratio from 0.01 to 0.2. Rizk and Lefebvre [23] have examined the effects of air and liquid properties and atomizer geometries on SMD. The tests were conducted using two geometrically similar atomizers having liquid orifice diameters of 0.55 and 0.75 mm. The results obtained have shown that the increases in air pressure, air velocity, and GLR, all tend to lower the value of SMD. An empirical equation for SMD was derived as follows:
0:4 0:4 SMD r 1 ¼ 0:49 1 þ dout GLR qG u2R dout 0:5 l2L 1 þ 0:15 1þ GLR rqL dout
depends upon the interaction between the spray liquid properties and nozzle design [6], and therefore the effect of a particular formulation sprayed through one nozzle may not be the same when sprayed through a different nozzle design [15]. In the present paper the results of experimental observations on emulsions atomization in pneumatic nozzles using the digital microphotography method have been presented. The main parameters which have been selected in the experimental characterization of nozzles are the Sauter mean diameter and gas to liquid mass flow ratio. The experimental facility, nozzle geometry, measurement method and instruments are introduced. 2. Experimental setup and conditions Fig. 1 illustrates the schematic diagram of the experimental setup. The main elements of the test installation were nozzle (3) (Fig. 2), reservoir (5), pump (8), blower (6), measurement units of gas (7) and liquid (2) flows, computer (1) and digital camera (4) with lamps. The water–oil emulsion was pumped from the tank to the nozzle. The nozzles used in the study were plain-jet atomizers with internal mixing of the geometries presented in Table 1. The nozzle was mounted vertically on a stand. The investigated emulsion was injected vertically downstream through an atomizer into the room temperature and atmospheric pressure environment. The photographs with 3888 by 2592 pixels were obtained using a Canon EOS 1D Mark III camera and an automatic flash that allowed exposure times of 1/8000 s placed directly in front of the nozzle at a distance of approximately 0.6 m. The setup was equipped in four Canon Speedlite 580EX II lamps controlled by Canon STE-2 transmitter. The spray characteristics were obtained by averaging the values of five images for each experimental condition. The photographs were analyzed using Image Pro-Plus delivered by Media Cybernetics which provides in-depth and precise measurement analysis of the parameters of spray characteristics: the spray angle, the spray droplet spectrum produced by a nozzle and Sauter Mean Diameter (SMD). This one eliminates a human error and maintains the highest quality standard possible. The process temperature of 293 K in all measurements was regulated by a heat exchanger and controlled in the reservoir. The rotameters have been scaled for each of the investigated liquids. The studies were performed at flow rates of liquid phase changed from
ð6Þ
Antkowiak and Heim [2] have investigated atomization process in pneumatic atomizer for dust granulation and obtained the following empirical relationship:
SMD ¼ 1:06105 u3:0 G
4:1 pout _ 0:83 m L pG
ð7Þ
where pout is the pressure of surrounding gas. Spray nozzles have many important applications and have been the subjects of considerable researches [5,8,17]. Pneumatic nozzles are operated with comparatively low gas pressures and relatively high efficiencies. A wide variety of designs of this type have been produced for use in industrial gas turbines and oil-fired furnaces. Typical applications of pneumatic nozzles are: spray-drying, humidification, evaporative cooling, coating, moistening and greenhouse applications [10,28]. Several different atomizer designs have been described in literature [9,13,19]. The set-up can be designed so that either air and liquid are mixed inside the atomizer and ejected through the same orifice, or air and liquid impact, mix and generate the atomized spray after having been ejected from the atomizer through separate orifices. Nozzle performance
Fig. 1. Test installation: 1 – PC computer, 2 – liquid rotameters, 3 – nozzle, 4 – digital camera, 5 – vessel, 6 – blower, 7 – gas rotameter, 8 – pump.
957
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
0.0014 to 0.011 (dm3/s) and of gas phase changed from 0.28 to 1.4 (dm3/s), respectively. It corresponded to gas to liquid mass ratio (GLR) values from 0.028 to 0.92. Used oils were mineral oils delivered by Institute of Petroleum Processing (Cracow, Poland). The emulsion was prepared by blending mixtures of oil, water, and surfactant within 20 min. The surfactant EMB-2 delivered by PCC Rokita S.A. (Brzeg Dolny, Poland) was used. The emulsions had the mineral oil volume fraction in the range from 0.2 to 0.8. The surface tensions were measured by tensiometer K9 delivered by Krüss GmbH. The all oils and emulsions investigated had surface tension rL in the range from 29 to 34 (mN/m). The characteristics of emulsions used are presented in Table 2. The simple and multiple emulsions viscosity is described by Starov and Zhdanov [27], Dan and Jing [7] and Pal [20]. In the present work the equivalent viscosity of emulsions was determined from Arrhenius–Kendall’s equation:
log lL ¼ UD log lD þ ð1 UD Þ log lC
ð8Þ
Table 2 Characteristics of emulsions studied. Oil
Volume fraction
Denotation
Uoil (m3/m3) 0.2 0.4 0.6 0.8 Pure oil
20–30 20–30 20–30 20–30 20–30
0.2 0.4 0.6 0.8
1.92 103 3.70 103 7.13 103 13.7 103 26.4 103
973 946 919 892 866
20–50
0.2 0.4 0.6 0.8 Pure oil
20–50 20–50 20–50 20–50 20–50
0.2 0.4 0.6 0.8
2.12 103 4.50 103 9.53 103 20.2 103 42.8 103
973 946 920 893 866
20–70
0.2 0.4 0.6 0.8 Pure oil
20–70 20–70 20–70 20–70 20–70
0.2 0.4 0.6 0.8
2.27 103 5.14 103 11.7 103 26.4 103 59.9 103
973 946 919 892 865
20–90
0.2 0.4 0.6 0.8 Pure oil
20–90 20–90 20–90 20–90 20–90
0.2 0.4 0.6 0.8
2.39 103 5.70 103 13.6 103 32.5 103 77.7 103
974 948 921 895 869
Table 1 Geometry of investigated nozzles. Diameter of liquid outlet din (mm)
Diameter of nozzle outlet dout (mm)
A2 A3 A4 A5 A6
1.06
2.0 3.0 4.0 5.0 6.0
B2 B3 B4 B5 B6
1.35
2.0 3.0 4.0 5.0 6.0
C2 C3 C4 C5 C6
1.65
2.0 3.0 4.0 5.0 6.0
D2 D3 D4 D5 D6
2.0
2.0 3.0 4.0 5.0 6.0
E2 E3 E4 E5 E6
2.5
2.0 3.0 4.0 5.0 6.0
F2 F3 F4 F5 F6
3.0
2.0 3.0 4.0 5.0 6.0
Density qL (kg/m3)
Viscosity
20–30
Fig. 2. Construction of nozzles investigated.
Geometry
lL (Pa s)
Fig. 3. Viscosity of emulsions used.
958
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
where lL is the viscosity of emulsion, lC and lD are the viscosities of continuous and dispersed phases, respectively, and UD is the volume fraction of dispersed phase:
UD ¼
V oil VL
ð9Þ
The relationship between viscosity and oil volume fraction for oils used in experiments is shown in Fig. 3. 3. Experimental results and discussion Exemplary results of the visualization of air–water atomization are shown in Fig. 4 and these for air-emulsions systems in Figs. 5 and 6, respectively. The development of the spray passes through
several stages such as dribble (Fig. 4d), distorted pencil (Fig. 6) and fully developed spray (Figs. 4a, 5a and b) [13]. The observations suggest that the stage of spray development is strongly affected by the physical properties of liquid atomized and are in agreement with the measurements of Rhim and No [22] for investigations of emulsion atomization in pressure-swirl atomizer. In this study, there were not observed the onion and tulip stages characteristic for flow in smooth liquid film. In the pneumatic atomizers, atomizing gas is breaking the liquid film flow into droplets, therefore the distinct stages are not observed. The analysis of photos shows that the droplets which have been formed during the liquid atomization have very different sizes (Figs. 4–6). The smallest droplets have diameters of the order of 10 lm. The differences between air–water and air-emulsions
Fig. 4. Air–water atomization for VG = 0.28 (dm3/s) and VL = 0.0014 (dm3/s) in nozzle of geometry: (a) D3, (b) D4, (c) D5, (d) D6.
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
959
Fig. 5. Air–liquid atomization for VG = 0.56 (dm3/s) and VL = 0.0014 (dm3/s) in nozzle of geometry of B4: (a) water, (b) 20–30, Uoil = 0.2, (c) 20–50, Uoil = 0.4.
atomization have been observed. In liquid atomization two effects have been noted: firstly – the effect of viscosity, and secondly – the effect of surface tension. In many respects, viscosity is the key liquid property that governs atomization. High viscosity generally delays the onset of jet disintegration (Figs. 5 and 6), causing atomization to occur further downstream in regions of lower relative velocity. Lower surface tension of investigated emulsions (in comparison with water) causes acceleration of jet disintegration. For atomizers with smaller orifice diameters the atomization is complete within a short distance from the discharge orifice (Fig. 4a). The break-up of the jet has been observed at larger diameters of nozzle orifices (Fig. 4d). Values of gas and liquid velocities at smaller diameters of orifices exceed these ones observed for atomization process in larger atomizers. Higher values of the velocities cause the acceleration of jet disintegration. It has been shown that the atomization quality deteriorates with increases in diameters of liquid and nozzle outlets (Fig. 4). The experiments showed that the atomization quality depends on gas and liquid flow rates, type of atomizing liquid (density, viscosity and surface tension) and the atomizer construction used. It has been shown that the resulting sprays were strongly dependent on the nozzle geometry. The exemplary relation of SMD as a function of GLR for water atomization is shown in Fig. 7. It has been shown that the nozzle outlet diameter has effect on produced droplets. Exemplary dependence of SMD vs. GLR for 20–70 0.4 emulsion atomization is shown in Fig. 8. The comparison of plots presented in Fig. 7 and Fig. 8 shows that droplets formed during the emulsions atomization
have different sizes in comparison with droplets for water atomization, resulting in different values of SMD for water and emulsions atomization. At a constant gas mass flow rate, the increase of liquid mass flow rate brings about large droplets as shown in Figs. 9 and 10. In general, SMD exhibits a tendency to decrease with increasing the GLR. At high values of GLR, atomization is complete within a short distance from the discharge orifice. In the cases of larger diameters of nozzle outlet (5 and 6 mm) liquid and gas flow with relatively small velocities, and consequently, the liquid flows as a rigid body (plug) of cylindrical form. The jet was difficult to atomize (Fig. 6). At low values of GLR, the jet disintegration into large drops was observed. The data obtained in the present study have shown that the increasing of the atomizing gas mass flow will reduce the spray’s SMD at fixed liquid mass flow value. In Fig. 11 the exemplary relation between SMD and GLR for emulsion with oil volume fraction Uoil = 0.4 is shown. It has been observed that the viscosity of an oil added to water affects SMD value. The investigations have shown that SMD is increasing with increase of oil viscosity. In Fig. 12 the exemplary relation between SMD and GLR for emulsion at various oil volume fractions is shown. When the oil content increases, along with it the viscosity will increase, suppressing the breakup tendency and resulting in larger values of SMD in emulsion. That effect is also affirmed by the measurements of Broniarz-Press and Ochowiak [4] and Broniarz-Press et al. [5]. The effect of nozzle diameters is smaller at GLR values exceeding
960
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
Fig. 7. SMD as a function of GLR for water atomization.
Fig. 8. Exemplary plot of SMD as a function of GLR for 20–70 (Uoil = 0.4) emulsion atomization.
Fig. 6. Air–liquid atomization for VG = 0.28 (dm3/s) and VL = 0.0084 (dm3/s) in nozzle of geometry of C4: (a) water, (b) 20–30, Uoil = 0.2, (c) 20–30, Uoil = 0.8.
0.8. It is reasonable to request that the effect may be disregarded in atomization process at larger values of GLR. In the following analysis the results of the present study have been compared with those of representative studies in the literature (Fig. 13). The comparison of SMD values is difficult for the sake of different constructions of the atomizers investigated. The results obtained are in good approximation to correlations given by Rizkalla and Lefebvre [24] and Antkowiak and Heim [2]. The correlation proposed by Nukiyama and Tanasawa [18] gives the understated values of SMD at values of GLR investigated and is probably valid at higher values of GLR. The droplets diameters (SMD) produced by the investigated nozzles are not in an agreement with the results published by Sakai et al. [25]. The equation of Rizk and Lefebvre [23] gives large dispersion of points. All the correlations
Fig. 9. SMD vs. GLR for water and 20–30 (Uoil = 0.2) emulsion.
proposed have shown that SMD is decreasing with increase of GLR. Nevertheless not all of them take into account nozzle diameters. Effect of nozzle diameters is clear and should be taken into consideration (in investigated range of nozzle diameters and GLR values). The studies have shown that SMD is decreasing with decrease of nozzle diameters. The experimental data are approximated by the relationship as follows:
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
961
Fig. 13. SMD as a function of GLR resulted from various studies.
Fig. 10. SMD vs. GLR for water and 20–70 (Uoil = 0.4) emulsion.
Fig. 11. SMD vs. GLR for emulsion with oil volume fraction Uoil = 0.4
Fig. 14. Comparison between the experimental data and the data resulted from relationship (10).
between the experimental data and correlation proposed is presented in Fig. 14. 4. Conclusions
Fig. 12. SMD vs. GLR for emulsion with increasing of oil volume fraction.
0:12
SMD ¼ A
dout
0:56 din
l0:12 L GLR0:30 lG
ð10Þ
where A is dependent on nozzle internal geometry, surface tension as well as on other parameters influencing atomization process. For the systems studied A was equal to 8.55 104. The comparison
The experimental observations of emulsions atomization process in pneumatic nozzles have been presented. The differences between characteristics of atomization for water and emulsions, as well as the influence of emulsion composition on the droplet sizes, have been observed. Stages presented in this article are in good agreement with the observations of Rhim and No [22] of emulsion atomization in pressure-swirl atomizer. The development of the spray passes through several stages such as dribble, distorted pencil and fully developed spray as the liquid and gas flow rates. The analysis of the photos of water and emulsions atomization process showed that the SMD is dependent on gas and liquid flow rates, construction of nozzle and properties of a liquid sprayed. SMD for all investigated geometries was decreasing with an increase of GLR value. It can be seen that GLR is a key parameter in determining the quality of atomization. The experimental results showed that the changes in geometries of a nozzle lead to the significant changes in spray characteristics. SMD is decreasing with increase of liquid and nozzle outlets diameter. The study showed that the SMD is dependent on a content of oil in emulsions. SMD
962
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
is increasing with increase of volume fraction of oil in emulsion. SMD increase is connected with increase of emulsion viscosity and with increase of viscosity of an oil added to water. It is evident that the addition of water changes emulsions properties which are the important parameters influencing the atomization of the spray. The experimental data are approximated by the relationship (10). The results obtained are in good approximation to correlations given by Rizkalla and Lefebvre [24] and Antkowiak and Heim [2]. Acknowledgements The authors are indebted to the Polish Ministry of Science and High Education under the auspices of whose this work was carried out (Grant No. N207 043 31/1786).
[11]
[12] [13] [14] [15]
[16] [17] [18]
References [19] [1] J. Abu-Ali, S.A. Barringer, Method for electrostatic atomization of emulsions in an EHD system, Journal of Electrostatics 63 (2005) 361–369. [2] W. Antkowiak, A. Heim, Investigation of pneumatic spray nozzle for wetting granulate fine material, Inzynieria Chemiczna i Procesowa (Chemical and Process Engineering) 8/1 (1987) 57–65 (in Polish). [3] P.A. Baron, K. Willeke, Aerosol Measurements Principles, Techniques and Applications, John Wiley and Sons Ltd., New York, 2001. [4] L. Broniarz-Press, M. Ochowiak, The vegetable oil atomization in a ring-shaped orifice nozzle, in: Proceedings of International Conference SSCHE’2007, Full Text, Tatranske Matliare, Slovakia, 2007, pp. 1–10. [5] L. Broniarz-Press, M. Ochowiak, W. Szaferski, Atomization of the oils analysis in nozzle using digital microphotography, in: Symposium and VII Workshop on Modelling of Multiphase Flows in Thermo-Chemical Systems, Book of Abstracts, Poster, Gdansk, 2007. [6] M.C. Butler Ellis, C.R. Tuck, How adjuvants influence spray formation with different hydraulic nozzles, Crop Protection 18 (1999) 101–110. [7] D. Dan, G. Jing, Apparent viscosity prediction of non-Newtonian water-incrude oil emulsions, Journal of Petroleum Science and Engineering 53 (2006) 113–122. [8] A. Gajtkowski, Effect of Sprayers Parameters in Form Swirl Discs on the Spray Quality of Liquid used in Plant Protection, Agricultural University, Poznan, 1978. [9] A. Gajtkowski, Investigations and Selection of Operation Parameters for Sprayers used in Field Spraying, Agricultural University, Poznan, 1987. [10] T. Hino, S. Shimabayashi, N. Ohnishi, M. Fujisaki, H. Mori, O. Watanabe, K. Kawashima, K. Nagao, Development of a new type nozzle and spray-drier for
[20] [21] [22]
[23]
[24] [25]
[26]
[27] [28] [29]
industrial production of fine powders, European Journal of Pharmaceutics and Biopharmaceutics 49 (2000) 79–85. P.J. Holloway, M.C. Butler Ellis, D.A. Webb, N.M. Western, C.R. Tuck, A.L. Hayes, P.C.H. Miller, Effects of some agricultural tank-mix adjuvants on the deposition efficiency of aqueous sprays on foliage, Crop Protection 19 (2000) 27–37. G.N. Laryea, S.Y. No, Spray angle and break-up length of charge-injected electrostatic pressure-swirl nozzle, Journal of Electrostatics 60 (2004) 37–47. A.H. Lefebvere, Atomization and Sprays, Hemisphere Publishing Corporation, New York, 1989. H. Liu, Science and Engineering of Droplets Fundamentals and Applications, William Andrew Publishing/Notes, New York, 2000. P.C.H. Miller, M.C. Butler Ellis, Effects of formulation on spray nozzle performance for applications from ground-based boom sprayers, Crop Protection 19 (2000) 609–615. A. Millqvist-Fureby, Characterisation of spray-dried emulsions with mixed fat phases, Colloids and Surfaces B: Biointerfaces 31 (2003) 65–79. G.G. Nasr, A.J. Yule, L. Bendig, Industrial Sprays and Atomization, SpringerVerlag, London, 2002. S. Nukiyama, Y. Tanasawa, Experiments on the atomization of liquids in an air stream, Transactions of the Society of Mechanical Engineers 5 (1939) 68–75 (from A.H. Lefebvere, 1989). Z. Orzechowski, J. Prywer, Liquid Atomization, Wydawnictwo Naukowo Techniczne, Warszawa, 1991. R. Pal, Viscosity models for multiple emulsions, Food Hydrocolloids 22 (2008) 428–438. A.S. Ramadhas, S. Jayaraj, C. Muraleedharan, Use of vegetable oils as I.C. engine fuels – a review, Renewable Energy 29 (2004) 727–742. J.H. Rhim, S.Y. No, Breakup length of conical emulsion sheet discharged by pressure-swirl atomizer, International Journal of Automotive Technology 2 (3) (2001) 103–107. N.K. Rizk, A.H. Lefebvre, Spray characteristics of plain-jet airblast atomizers, Transactions on ASME Journal of Engineering for Gas Turbines and Power, 106 (1984) 639–644, (from A.H. Lefebvere, 1989). A. Rizkalla, A.H. Lefebvre, The influence of air and liquid properties on air blast atomization, ASME Journal of fluid Engineering 973 (1975) 316–320. T. Sakai, M. Kito, M. Saito, T. Kanbe, Characteristics of internal mixing twinfluid atomizer, in: Proceedings of the 1st Conference on Liquid Atomization and Sprays, Tokyo, 1978, (from A.H. Lefebvere, 1989). S. Slupek, The polynuclear aromatic hydrocarbons formation during combustion, in: Proceedings of the Conference on Low-emission Combustion Techniques, Ustron-Zawodzie, Poland, 1996 (in Polish). V.M. Starov, V.G. Zhdanov, Viscosity of emulsions: influence of flocculation, Journal of Colloid and Interface Science 258 (2003) 404–414. A. Tarnogrodzki, The atomizers used in air protection, Ochrona Powietrza (Air Protection) 4 (1991) 92–95 (in Polish). G. Vaitilingom, C. Perilhon, A. Liennard, M. Gandon, Development of rape seed oil burners for drying and heating, Industrial Crops and Products 7 (1998) 273–279.
Contents lists available at ScienceDirect
Experimental Thermal and Fluid Science journal homepage: www.elsevier.com/locate/etfs
The atomization of water–oil emulsions L. Broniarz-Press *, M. Ochowiak, J. Rozanski, S. Woziwodzki Department of Chemical Engineering and Equipment, Faculty of Chemical Technology, Poznan University of Technology, Pl. M. Sklodowskiej-Curie 2, PL 60-965 Poznan, Poland
a r t i c l e
i n f o
Article history: Received 10 March 2009 Received in revised form 9 April 2009 Accepted 9 April 2009
Keywords: Atomization Visualisation Emulsion Spray Sauter mean diameter
a b s t r a c t The paper presents the results of experimental studies on atomization of the emulsions flowing through twin-fluid atomizers obtained by the use of the digital microphotography method. The main elements of the test installation were: nozzle, reservoir, pump and measurement units of liquid flow. The photographs were taken by a digital camera with automatic flash at exposure time of 1/8000 s and subsequently analyzed using Image Pro-Plus. The oils used were mineral oils 20–90, 20–70, 20–50 and 20–30. The studies were performed at flow rates of liquid phase changed from 0.0014 to 0.011 (dm3/s) and gas phase changed from 0.28 to 1.4 (dm3/s), respectively. The analysis of photos shows that the droplets being formed during the liquid atomization have very different sizes. The smallest droplets have diameters of the order of 10 lm. The experimental results showed that the changes in physical properties of a liquid phase lead to the significant changes in the spray characteristics. The analysis of the photos of water and emulsions atomization process showed that the droplet sizes are dependent on gas and liquid flow rates, construction of nozzle and properties of liquid. The differences between characteristics of atomization for water and emulsions have been observed. Analysis of photos on forming the droplets in air–water and air-emulsions systems showed that droplets are bigger in air-emulsion system (at the same value of gas to liquid mass ratio). The values of Sauter mean diameter (SMD) increased with increase of volume fraction of oil in emulsion. The droplet size increased with emulsion viscosity. Ó 2009 Elsevier Inc. All rights reserved.
1. Introduction The atomization of emulsions is wide-spread process in many branches of industry, for instance, in power engineering and combustion engines, in engineering industry and in agriculture. The cooling agent for machine elements, fuel oil, pesticides and milk can be emulsions [16]. In the food industry, oils are used to carry oil-soluble colours, flavours and nutrients that are coated onto the outside of the food. However, many colours, flavours and nutrients are water-soluble, which require water to be the carrier. Emulsions, which carry both oil and water-soluble additives to the food at the same time, are also commonly sprayed [1]. The studies of emulsions atomization were also directed to improve the combustion performances of emulsions as fuels in furnaces for local power generation [12,21,26,29]. The spray characteristics are: spray angle, covering of surface, droplet size distribution, droplet velocity distribution, volume distribution pattern, spray structure, the structure of individual droplets. These basic parameters are described by Lefebvere [13], Orzechowski and Prywer [19] and some other authors. The measurement technique was described by Lefebvere [13], Orzechowski
* Corresponding author. Tel.: +48 61 6652789; fax: +48 61 8103003. E-mail addresses: [email protected], [email protected] (L. Broniarz-Press). 0894-1777/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.expthermflusci.2009.04.002
and Prywer [19] and Liu [14]. Measurements of droplet size distribution are routinely made by the use of optical techniques. The prediction of droplet size distributions is accomplished through empirical correlations accounting for liquid properties, atomizer design and fluid flows [13]. The most relevant properties of a liquid are surface tension, viscosity, and density [3,11]. A typical spray includes a wide range of droplet sizes. Some knowledge of the droplet size distribution is helpful in evaluating process applications in sprays, especially in calculations of heat or mass transfer between the dispersed liquid and the surrounding gas. SMD is the diameter of that drop whose volume/surface ratio value is the same as the arithmetic mean of volume/surface values on the total number of drops belonging to the sample spray under examination. The SMD is often of use in applications where the active surface or surface area is important, e.g. atomization, catalysis or combustion. The SMD is calculated as the ratio as follows:
P i
SMD ¼ P i
3
ni di
2
ni di
ð1Þ
Many different correlations for SMD have been presented in literature. The correlation proposed by Nukiyama and Tanasawa [18] is the most often in use. The investigation of atomization process in a plain-jet atomizer resulted in the empirical equation for the SMD:
956
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
SMD ¼
0:5 2 0:25 1:5 0:585 r lL QL þ 53 uR qL rqL QG
ð2Þ
This equation was obtained at diameters of water outlet changed from 0.2 to 1.0 mm and nozzle outlet diameters from 2 to 5 mm. The equation applies to a range of air velocities from 60 to 340 m/s and values of gas to liquid mass ratio (GLR) from 1 to 14. Hereby GLR is defined as follows:
GLR ¼
_G m _L m
ð3Þ
_ G and m _ L are mass flow rates of atomizing gas and liquid, where m respectively. The correlation does not take into account the diameters of atomizer as well as the density and viscosity of gas. Rizkalla and Lefebvre [24] investigated atomization process in plain-jet air-blast nozzles and obtained the following empirical equation for the SMD:
1:70 _ L Þ0:33 ðrm 1 1þ 0:37 0:30 GLR uR qL qG 1:70 2 0:5 l dout 1 þ 0:13 L 1þ GLR rqL
SMD ¼ 0:95
ð4Þ
From studies carried out on the atomization of water, with air as the atomizing fluid, Sakai et al. [25] derived the following experimental correlation for SMD: 0:75
SMD ¼ 14 106 dout
_L m _G m
0:75
0:75
¼ 14 106 dout ðGLRÞ0:75
ð5Þ
The equation presented above applies to a range of liquid flow rates from 0.008 to 0.028 kg/s and values of gas to liquid mass ratio from 0.01 to 0.2. Rizk and Lefebvre [23] have examined the effects of air and liquid properties and atomizer geometries on SMD. The tests were conducted using two geometrically similar atomizers having liquid orifice diameters of 0.55 and 0.75 mm. The results obtained have shown that the increases in air pressure, air velocity, and GLR, all tend to lower the value of SMD. An empirical equation for SMD was derived as follows:
0:4 0:4 SMD r 1 ¼ 0:49 1 þ dout GLR qG u2R dout 0:5 l2L 1 þ 0:15 1þ GLR rqL dout
depends upon the interaction between the spray liquid properties and nozzle design [6], and therefore the effect of a particular formulation sprayed through one nozzle may not be the same when sprayed through a different nozzle design [15]. In the present paper the results of experimental observations on emulsions atomization in pneumatic nozzles using the digital microphotography method have been presented. The main parameters which have been selected in the experimental characterization of nozzles are the Sauter mean diameter and gas to liquid mass flow ratio. The experimental facility, nozzle geometry, measurement method and instruments are introduced. 2. Experimental setup and conditions Fig. 1 illustrates the schematic diagram of the experimental setup. The main elements of the test installation were nozzle (3) (Fig. 2), reservoir (5), pump (8), blower (6), measurement units of gas (7) and liquid (2) flows, computer (1) and digital camera (4) with lamps. The water–oil emulsion was pumped from the tank to the nozzle. The nozzles used in the study were plain-jet atomizers with internal mixing of the geometries presented in Table 1. The nozzle was mounted vertically on a stand. The investigated emulsion was injected vertically downstream through an atomizer into the room temperature and atmospheric pressure environment. The photographs with 3888 by 2592 pixels were obtained using a Canon EOS 1D Mark III camera and an automatic flash that allowed exposure times of 1/8000 s placed directly in front of the nozzle at a distance of approximately 0.6 m. The setup was equipped in four Canon Speedlite 580EX II lamps controlled by Canon STE-2 transmitter. The spray characteristics were obtained by averaging the values of five images for each experimental condition. The photographs were analyzed using Image Pro-Plus delivered by Media Cybernetics which provides in-depth and precise measurement analysis of the parameters of spray characteristics: the spray angle, the spray droplet spectrum produced by a nozzle and Sauter Mean Diameter (SMD). This one eliminates a human error and maintains the highest quality standard possible. The process temperature of 293 K in all measurements was regulated by a heat exchanger and controlled in the reservoir. The rotameters have been scaled for each of the investigated liquids. The studies were performed at flow rates of liquid phase changed from
ð6Þ
Antkowiak and Heim [2] have investigated atomization process in pneumatic atomizer for dust granulation and obtained the following empirical relationship:
SMD ¼ 1:06105 u3:0 G
4:1 pout _ 0:83 m L pG
ð7Þ
where pout is the pressure of surrounding gas. Spray nozzles have many important applications and have been the subjects of considerable researches [5,8,17]. Pneumatic nozzles are operated with comparatively low gas pressures and relatively high efficiencies. A wide variety of designs of this type have been produced for use in industrial gas turbines and oil-fired furnaces. Typical applications of pneumatic nozzles are: spray-drying, humidification, evaporative cooling, coating, moistening and greenhouse applications [10,28]. Several different atomizer designs have been described in literature [9,13,19]. The set-up can be designed so that either air and liquid are mixed inside the atomizer and ejected through the same orifice, or air and liquid impact, mix and generate the atomized spray after having been ejected from the atomizer through separate orifices. Nozzle performance
Fig. 1. Test installation: 1 – PC computer, 2 – liquid rotameters, 3 – nozzle, 4 – digital camera, 5 – vessel, 6 – blower, 7 – gas rotameter, 8 – pump.
957
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
0.0014 to 0.011 (dm3/s) and of gas phase changed from 0.28 to 1.4 (dm3/s), respectively. It corresponded to gas to liquid mass ratio (GLR) values from 0.028 to 0.92. Used oils were mineral oils delivered by Institute of Petroleum Processing (Cracow, Poland). The emulsion was prepared by blending mixtures of oil, water, and surfactant within 20 min. The surfactant EMB-2 delivered by PCC Rokita S.A. (Brzeg Dolny, Poland) was used. The emulsions had the mineral oil volume fraction in the range from 0.2 to 0.8. The surface tensions were measured by tensiometer K9 delivered by Krüss GmbH. The all oils and emulsions investigated had surface tension rL in the range from 29 to 34 (mN/m). The characteristics of emulsions used are presented in Table 2. The simple and multiple emulsions viscosity is described by Starov and Zhdanov [27], Dan and Jing [7] and Pal [20]. In the present work the equivalent viscosity of emulsions was determined from Arrhenius–Kendall’s equation:
log lL ¼ UD log lD þ ð1 UD Þ log lC
ð8Þ
Table 2 Characteristics of emulsions studied. Oil
Volume fraction
Denotation
Uoil (m3/m3) 0.2 0.4 0.6 0.8 Pure oil
20–30 20–30 20–30 20–30 20–30
0.2 0.4 0.6 0.8
1.92 103 3.70 103 7.13 103 13.7 103 26.4 103
973 946 919 892 866
20–50
0.2 0.4 0.6 0.8 Pure oil
20–50 20–50 20–50 20–50 20–50
0.2 0.4 0.6 0.8
2.12 103 4.50 103 9.53 103 20.2 103 42.8 103
973 946 920 893 866
20–70
0.2 0.4 0.6 0.8 Pure oil
20–70 20–70 20–70 20–70 20–70
0.2 0.4 0.6 0.8
2.27 103 5.14 103 11.7 103 26.4 103 59.9 103
973 946 919 892 865
20–90
0.2 0.4 0.6 0.8 Pure oil
20–90 20–90 20–90 20–90 20–90
0.2 0.4 0.6 0.8
2.39 103 5.70 103 13.6 103 32.5 103 77.7 103
974 948 921 895 869
Table 1 Geometry of investigated nozzles. Diameter of liquid outlet din (mm)
Diameter of nozzle outlet dout (mm)
A2 A3 A4 A5 A6
1.06
2.0 3.0 4.0 5.0 6.0
B2 B3 B4 B5 B6
1.35
2.0 3.0 4.0 5.0 6.0
C2 C3 C4 C5 C6
1.65
2.0 3.0 4.0 5.0 6.0
D2 D3 D4 D5 D6
2.0
2.0 3.0 4.0 5.0 6.0
E2 E3 E4 E5 E6
2.5
2.0 3.0 4.0 5.0 6.0
F2 F3 F4 F5 F6
3.0
2.0 3.0 4.0 5.0 6.0
Density qL (kg/m3)
Viscosity
20–30
Fig. 2. Construction of nozzles investigated.
Geometry
lL (Pa s)
Fig. 3. Viscosity of emulsions used.
958
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
where lL is the viscosity of emulsion, lC and lD are the viscosities of continuous and dispersed phases, respectively, and UD is the volume fraction of dispersed phase:
UD ¼
V oil VL
ð9Þ
The relationship between viscosity and oil volume fraction for oils used in experiments is shown in Fig. 3. 3. Experimental results and discussion Exemplary results of the visualization of air–water atomization are shown in Fig. 4 and these for air-emulsions systems in Figs. 5 and 6, respectively. The development of the spray passes through
several stages such as dribble (Fig. 4d), distorted pencil (Fig. 6) and fully developed spray (Figs. 4a, 5a and b) [13]. The observations suggest that the stage of spray development is strongly affected by the physical properties of liquid atomized and are in agreement with the measurements of Rhim and No [22] for investigations of emulsion atomization in pressure-swirl atomizer. In this study, there were not observed the onion and tulip stages characteristic for flow in smooth liquid film. In the pneumatic atomizers, atomizing gas is breaking the liquid film flow into droplets, therefore the distinct stages are not observed. The analysis of photos shows that the droplets which have been formed during the liquid atomization have very different sizes (Figs. 4–6). The smallest droplets have diameters of the order of 10 lm. The differences between air–water and air-emulsions
Fig. 4. Air–water atomization for VG = 0.28 (dm3/s) and VL = 0.0014 (dm3/s) in nozzle of geometry: (a) D3, (b) D4, (c) D5, (d) D6.
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
959
Fig. 5. Air–liquid atomization for VG = 0.56 (dm3/s) and VL = 0.0014 (dm3/s) in nozzle of geometry of B4: (a) water, (b) 20–30, Uoil = 0.2, (c) 20–50, Uoil = 0.4.
atomization have been observed. In liquid atomization two effects have been noted: firstly – the effect of viscosity, and secondly – the effect of surface tension. In many respects, viscosity is the key liquid property that governs atomization. High viscosity generally delays the onset of jet disintegration (Figs. 5 and 6), causing atomization to occur further downstream in regions of lower relative velocity. Lower surface tension of investigated emulsions (in comparison with water) causes acceleration of jet disintegration. For atomizers with smaller orifice diameters the atomization is complete within a short distance from the discharge orifice (Fig. 4a). The break-up of the jet has been observed at larger diameters of nozzle orifices (Fig. 4d). Values of gas and liquid velocities at smaller diameters of orifices exceed these ones observed for atomization process in larger atomizers. Higher values of the velocities cause the acceleration of jet disintegration. It has been shown that the atomization quality deteriorates with increases in diameters of liquid and nozzle outlets (Fig. 4). The experiments showed that the atomization quality depends on gas and liquid flow rates, type of atomizing liquid (density, viscosity and surface tension) and the atomizer construction used. It has been shown that the resulting sprays were strongly dependent on the nozzle geometry. The exemplary relation of SMD as a function of GLR for water atomization is shown in Fig. 7. It has been shown that the nozzle outlet diameter has effect on produced droplets. Exemplary dependence of SMD vs. GLR for 20–70 0.4 emulsion atomization is shown in Fig. 8. The comparison of plots presented in Fig. 7 and Fig. 8 shows that droplets formed during the emulsions atomization
have different sizes in comparison with droplets for water atomization, resulting in different values of SMD for water and emulsions atomization. At a constant gas mass flow rate, the increase of liquid mass flow rate brings about large droplets as shown in Figs. 9 and 10. In general, SMD exhibits a tendency to decrease with increasing the GLR. At high values of GLR, atomization is complete within a short distance from the discharge orifice. In the cases of larger diameters of nozzle outlet (5 and 6 mm) liquid and gas flow with relatively small velocities, and consequently, the liquid flows as a rigid body (plug) of cylindrical form. The jet was difficult to atomize (Fig. 6). At low values of GLR, the jet disintegration into large drops was observed. The data obtained in the present study have shown that the increasing of the atomizing gas mass flow will reduce the spray’s SMD at fixed liquid mass flow value. In Fig. 11 the exemplary relation between SMD and GLR for emulsion with oil volume fraction Uoil = 0.4 is shown. It has been observed that the viscosity of an oil added to water affects SMD value. The investigations have shown that SMD is increasing with increase of oil viscosity. In Fig. 12 the exemplary relation between SMD and GLR for emulsion at various oil volume fractions is shown. When the oil content increases, along with it the viscosity will increase, suppressing the breakup tendency and resulting in larger values of SMD in emulsion. That effect is also affirmed by the measurements of Broniarz-Press and Ochowiak [4] and Broniarz-Press et al. [5]. The effect of nozzle diameters is smaller at GLR values exceeding
960
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
Fig. 7. SMD as a function of GLR for water atomization.
Fig. 8. Exemplary plot of SMD as a function of GLR for 20–70 (Uoil = 0.4) emulsion atomization.
Fig. 6. Air–liquid atomization for VG = 0.28 (dm3/s) and VL = 0.0084 (dm3/s) in nozzle of geometry of C4: (a) water, (b) 20–30, Uoil = 0.2, (c) 20–30, Uoil = 0.8.
0.8. It is reasonable to request that the effect may be disregarded in atomization process at larger values of GLR. In the following analysis the results of the present study have been compared with those of representative studies in the literature (Fig. 13). The comparison of SMD values is difficult for the sake of different constructions of the atomizers investigated. The results obtained are in good approximation to correlations given by Rizkalla and Lefebvre [24] and Antkowiak and Heim [2]. The correlation proposed by Nukiyama and Tanasawa [18] gives the understated values of SMD at values of GLR investigated and is probably valid at higher values of GLR. The droplets diameters (SMD) produced by the investigated nozzles are not in an agreement with the results published by Sakai et al. [25]. The equation of Rizk and Lefebvre [23] gives large dispersion of points. All the correlations
Fig. 9. SMD vs. GLR for water and 20–30 (Uoil = 0.2) emulsion.
proposed have shown that SMD is decreasing with increase of GLR. Nevertheless not all of them take into account nozzle diameters. Effect of nozzle diameters is clear and should be taken into consideration (in investigated range of nozzle diameters and GLR values). The studies have shown that SMD is decreasing with decrease of nozzle diameters. The experimental data are approximated by the relationship as follows:
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
961
Fig. 13. SMD as a function of GLR resulted from various studies.
Fig. 10. SMD vs. GLR for water and 20–70 (Uoil = 0.4) emulsion.
Fig. 11. SMD vs. GLR for emulsion with oil volume fraction Uoil = 0.4
Fig. 14. Comparison between the experimental data and the data resulted from relationship (10).
between the experimental data and correlation proposed is presented in Fig. 14. 4. Conclusions
Fig. 12. SMD vs. GLR for emulsion with increasing of oil volume fraction.
0:12
SMD ¼ A
dout
0:56 din
l0:12 L GLR0:30 lG
ð10Þ
where A is dependent on nozzle internal geometry, surface tension as well as on other parameters influencing atomization process. For the systems studied A was equal to 8.55 104. The comparison
The experimental observations of emulsions atomization process in pneumatic nozzles have been presented. The differences between characteristics of atomization for water and emulsions, as well as the influence of emulsion composition on the droplet sizes, have been observed. Stages presented in this article are in good agreement with the observations of Rhim and No [22] of emulsion atomization in pressure-swirl atomizer. The development of the spray passes through several stages such as dribble, distorted pencil and fully developed spray as the liquid and gas flow rates. The analysis of the photos of water and emulsions atomization process showed that the SMD is dependent on gas and liquid flow rates, construction of nozzle and properties of a liquid sprayed. SMD for all investigated geometries was decreasing with an increase of GLR value. It can be seen that GLR is a key parameter in determining the quality of atomization. The experimental results showed that the changes in geometries of a nozzle lead to the significant changes in spray characteristics. SMD is decreasing with increase of liquid and nozzle outlets diameter. The study showed that the SMD is dependent on a content of oil in emulsions. SMD
962
L. Broniarz-Press et al. / Experimental Thermal and Fluid Science 33 (2009) 955–962
is increasing with increase of volume fraction of oil in emulsion. SMD increase is connected with increase of emulsion viscosity and with increase of viscosity of an oil added to water. It is evident that the addition of water changes emulsions properties which are the important parameters influencing the atomization of the spray. The experimental data are approximated by the relationship (10). The results obtained are in good approximation to correlations given by Rizkalla and Lefebvre [24] and Antkowiak and Heim [2]. Acknowledgements The authors are indebted to the Polish Ministry of Science and High Education under the auspices of whose this work was carried out (Grant No. N207 043 31/1786).
[11]
[12] [13] [14] [15]
[16] [17] [18]
References [19] [1] J. Abu-Ali, S.A. Barringer, Method for electrostatic atomization of emulsions in an EHD system, Journal of Electrostatics 63 (2005) 361–369. [2] W. Antkowiak, A. Heim, Investigation of pneumatic spray nozzle for wetting granulate fine material, Inzynieria Chemiczna i Procesowa (Chemical and Process Engineering) 8/1 (1987) 57–65 (in Polish). [3] P.A. Baron, K. Willeke, Aerosol Measurements Principles, Techniques and Applications, John Wiley and Sons Ltd., New York, 2001. [4] L. Broniarz-Press, M. Ochowiak, The vegetable oil atomization in a ring-shaped orifice nozzle, in: Proceedings of International Conference SSCHE’2007, Full Text, Tatranske Matliare, Slovakia, 2007, pp. 1–10. [5] L. Broniarz-Press, M. Ochowiak, W. Szaferski, Atomization of the oils analysis in nozzle using digital microphotography, in: Symposium and VII Workshop on Modelling of Multiphase Flows in Thermo-Chemical Systems, Book of Abstracts, Poster, Gdansk, 2007. [6] M.C. Butler Ellis, C.R. Tuck, How adjuvants influence spray formation with different hydraulic nozzles, Crop Protection 18 (1999) 101–110. [7] D. Dan, G. Jing, Apparent viscosity prediction of non-Newtonian water-incrude oil emulsions, Journal of Petroleum Science and Engineering 53 (2006) 113–122. [8] A. Gajtkowski, Effect of Sprayers Parameters in Form Swirl Discs on the Spray Quality of Liquid used in Plant Protection, Agricultural University, Poznan, 1978. [9] A. Gajtkowski, Investigations and Selection of Operation Parameters for Sprayers used in Field Spraying, Agricultural University, Poznan, 1987. [10] T. Hino, S. Shimabayashi, N. Ohnishi, M. Fujisaki, H. Mori, O. Watanabe, K. Kawashima, K. Nagao, Development of a new type nozzle and spray-drier for
[20] [21] [22]
[23]
[24] [25]
[26]
[27] [28] [29]
industrial production of fine powders, European Journal of Pharmaceutics and Biopharmaceutics 49 (2000) 79–85. P.J. Holloway, M.C. Butler Ellis, D.A. Webb, N.M. Western, C.R. Tuck, A.L. Hayes, P.C.H. Miller, Effects of some agricultural tank-mix adjuvants on the deposition efficiency of aqueous sprays on foliage, Crop Protection 19 (2000) 27–37. G.N. Laryea, S.Y. No, Spray angle and break-up length of charge-injected electrostatic pressure-swirl nozzle, Journal of Electrostatics 60 (2004) 37–47. A.H. Lefebvere, Atomization and Sprays, Hemisphere Publishing Corporation, New York, 1989. H. Liu, Science and Engineering of Droplets Fundamentals and Applications, William Andrew Publishing/Notes, New York, 2000. P.C.H. Miller, M.C. Butler Ellis, Effects of formulation on spray nozzle performance for applications from ground-based boom sprayers, Crop Protection 19 (2000) 609–615. A. Millqvist-Fureby, Characterisation of spray-dried emulsions with mixed fat phases, Colloids and Surfaces B: Biointerfaces 31 (2003) 65–79. G.G. Nasr, A.J. Yule, L. Bendig, Industrial Sprays and Atomization, SpringerVerlag, London, 2002. S. Nukiyama, Y. Tanasawa, Experiments on the atomization of liquids in an air stream, Transactions of the Society of Mechanical Engineers 5 (1939) 68–75 (from A.H. Lefebvere, 1989). Z. Orzechowski, J. Prywer, Liquid Atomization, Wydawnictwo Naukowo Techniczne, Warszawa, 1991. R. Pal, Viscosity models for multiple emulsions, Food Hydrocolloids 22 (2008) 428–438. A.S. Ramadhas, S. Jayaraj, C. Muraleedharan, Use of vegetable oils as I.C. engine fuels – a review, Renewable Energy 29 (2004) 727–742. J.H. Rhim, S.Y. No, Breakup length of conical emulsion sheet discharged by pressure-swirl atomizer, International Journal of Automotive Technology 2 (3) (2001) 103–107. N.K. Rizk, A.H. Lefebvre, Spray characteristics of plain-jet airblast atomizers, Transactions on ASME Journal of Engineering for Gas Turbines and Power, 106 (1984) 639–644, (from A.H. Lefebvere, 1989). A. Rizkalla, A.H. Lefebvre, The influence of air and liquid properties on air blast atomization, ASME Journal of fluid Engineering 973 (1975) 316–320. T. Sakai, M. Kito, M. Saito, T. Kanbe, Characteristics of internal mixing twinfluid atomizer, in: Proceedings of the 1st Conference on Liquid Atomization and Sprays, Tokyo, 1978, (from A.H. Lefebvere, 1989). S. Slupek, The polynuclear aromatic hydrocarbons formation during combustion, in: Proceedings of the Conference on Low-emission Combustion Techniques, Ustron-Zawodzie, Poland, 1996 (in Polish). V.M. Starov, V.G. Zhdanov, Viscosity of emulsions: influence of flocculation, Journal of Colloid and Interface Science 258 (2003) 404–414. A. Tarnogrodzki, The atomizers used in air protection, Ochrona Powietrza (Air Protection) 4 (1991) 92–95 (in Polish). G. Vaitilingom, C. Perilhon, A. Liennard, M. Gandon, Development of rape seed oil burners for drying and heating, Industrial Crops and Products 7 (1998) 273–279.