- Email: [email protected]
Experimental research on the comprehensive operating parameters of atomized dust collector
Experimental Thermal and Fluid Science 62 (2015) 216–221
Contents lists available at ScienceDirect
Experimental Thermal and Fluid Science journal homepage: www.elsevier.com/locate/etfs
Experimental research on the comprehensive operating parameters of atomized dust collector Qiuzu Liu, Ziming Kou ⇑, Guijun Gao, Tengyan Hou College of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, PR China Shanxi Provincial Engineering Laboratory (Research Center) for Mine Fluid Control, Taiyuan 030024, PR China
a r t i c l e
i n f o
Article history: Received 8 April 2014 Received in revised form 12 December 2014 Accepted 5 January 2015 Available online 13 January 2015 Keywords: Atomized dust collector Operating parameters Nebulization efficiency Collecting efficiency
a b s t r a c t A shear-impact-type atomized dust controller was designed by combining the rotary spray blades and axial flow fan, and the droplet atomizing process included two steps: shear-atomizing and impact-atomizing. The comprehensive operating parameters of this dust controller were studied by measuring different droplet size, airflow velocity, water consumption, nebulization efficiency, and collecting efficiency under different rotating speed, diversion hole-exit diameter, and colliding tooth angle. The relationships among them have been particularly analyzed. Results indicated that the droplet size is greatly influenced by rotating speed; the airflow velocity enhances monotonously with the increase in rotating speed. Excessive rotating speed and diversion hole-exit diameter can cause water waste, and suitable colliding tooth angle h can improve nebulization efficiency. The optimal operating conditions were obtained with rotating speed 1500–2100 r/min, diversion hole-exit diameter 2–2.5 mm and colliding tooth angle 35– 40° by fully considering security, water consumption, nebulization and collecting efficiencies. In this case, the nebulization efficiency exceeds 96.3% and the collecting efficiency tops 98.6%. Ó 2015 Elsevier Inc. All rights reserved.
1. Introduction High concentration of dust in coal mine may cause many problems, such as dust (gas) explosion and pneumoconiosis because of long-term inhalation of respirable dust [1,2]. For security, it is rather significant to select a proper way to reduce dust [3–5]. Spraying dust is one of the most commonly used methods for dust collection, with the advantages of high efficiency and low cost [6]. At present there are mainly two ways to achieve spray dust, i.e. jet nozzle and negative pressure suction. The former is flexible and easy to control, but easy to be blocked by impurities in water or dust in working environment [7,8]. The latter mainly equips with bag or siphon filter, with the advantage of high efficiency for dust collection, but difficult to be maintained [9,10]. A new type of gas– water mixing nozzle developed by Zhang et al. improved the graining precision, but difficult to match the parameters of mixing cavity [11]. Jiang et al. studied the experiment on foam-dust collector, optimized its designing parameters and improved dust collecting efficiency. But it costs highly in application [12]. Rotary-atomized dust collector, a type of dust collecting equipment, disintegrates a liquid by the centrifugal force results from ⇑ Corresponding author. Tel.: +86 0351 6149095. E-mail address: [email protected] (Z. Kou). http://dx.doi.org/10.1016/j.expthermflusci.2015.01.001 0894-1777/Ó 2015 Elsevier Inc. All rights reserved.
high speed rotating components. This atomizer has been widely used in industry, especially in the fields of dust collection and humidification [13]. Recently, most studies on rotary atomized dust collector have been launched from the shear fracture of liquid membrane, but ideal particle sizes are hard to obtained [14]. Wang et al. [15] investigated the mechanism of direct drop formation and ligament formation in a rotary cup which were recorded by a highspeed camera and explained the fracturing process of liquid film. Hadef and Lenze [16] measured a kerosene air blast atomized spray flame between two coswirling air streams by a phase–doppler particle sizing system, and found a small liquid exists in the centre of the combustor due to larger droplets with the swirl effect. Droplets can be effectively broken at a high speed through impacting on solid surface, which attracts many researchers’ attention [17,18]. Julián et al. [19] studied the drop impacting outcome regimes in a broad experimental condition, and illustrated the crushing process of droplet. Cossali et al. [20] reported an experimental analysis of secondary atomizing produced by a single drop impacting on solid surface, analyzed the morphology of drop spreading and breaking-up in details. Liu et al. [21] investigated a hydrophilic particle impact on a gas–liquid interface and found the particle moving velocity, viscosity and surface tension had a great influence on droplet deformation. Up to now, because of
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
droplet colliding process is difficult to follow, studies on droplet impact atomizing in application are seldom mentioned. The main purpose of this study is to develop a device that integrates the rotary atomizing and impact crushing to find an optimal condition in the following aspects: droplet size, airflow velocity, nebulization efficiency and collection efficiency on the basis of analyzing the comprehensive operating parameters (rotating speed, diversion hole-exit diameter, and colliding tooth angle) by taking consideration of high efficiency, less water consumption and safety. Thus Multi-point real-time testing of computer technology and frequency conversion technology were applied, and the performance of atomizing precipitator was tested in a more broad experimental condition. 2. Principle and parameters 2.1. Shear-impact-type atomized dust controller The structure and principle of shear-impact-type atomized dust controller is shown in Fig. 1. The device combines rotary spray blades and axial flow fan, integrating shearing and impacting atomizing. Its core atomizing component is the spray fan with a straight diversion hole inside, making water flow smoothly and reducing water consumption to achieve the combination of wind wheel and nozzle head successfully. The dust collecting process can be divided into two steps: shear-atomizing and impact-atomizing. In the former step, the droplet is thrown out from diversion hole at s high rotational speed, then it is atomized into droplets with the interaction of aerodynamic and centrifugal force. In the latter process, the atomized droplets run into colliding tooth at a high speed and then are broken into smaller droplets. The positional relationship between spray fan and colliding tooth is shown in Fig. 2, where h is the colliding tooth angle. The dust is captured by the atomized water mist which is blown out by spray fan.
Fig. 2. Installation diagram of colliding tooth. 1-colliding tooth; 2-diversion holeexit; 3-spray fan.
pressibility of liquid, the pressure inside a liquid increases immediately when impacting on the colliding tooth at a high speed. When the internal pressure is greater than the combined action of the external pressure, the droplet surface tension and internal cohesion, the liquid will rapidly disintegrate into tiny droplets and form mist field. The atomizing effect is related to the droplet sizes which are affected by the rotating speed and diversion hole-exit diameter; and also associated with the droplet impact angle which can be adjusted by colliding tooth angle. The breakup process of droplets is related to many factors. Here three main factors, i.e. rotating speed, diversion hole-exit diameter and colliding tooth angle are considered. 2.3. Parameters 2.3.1. Droplet size A droplet is atomized by the dust collector, whose characteristic parameters can fully reflect droplet particle size. Here the Sauter mean diameter dSMD is introduced.
dSMD
m X 3 ¼ nidi
,
i¼1
2.2. Droplets formation process When a liquid reaches the diversion hole along the flow channel under the action of centrifugal force, there is a relative motion between the liquid and air because of high-speed rotating blade. The liquid is stretched gradually, then ruptured when it overcomes the shackles of the droplet adhesion and surface tension. Due to the centrifugal force generated by the rotating blade, the droplets have a jet velocity when departing from the diversion channel. The moving droplets interact with the surrounding air to achieve atomizing, which is similar to the nozzle atomizing. The blade speed not only determines the velocity of‘ moving droplets, but also influences the friction between the droplets and air. The average diameter of shear atomized droplets is relatively large (generally hundreds of microns), therefore, the droplet diameter needs to decrease further by atomizing. Because of the incom-
m X 2 nidi
ð1Þ
i¼1
where m is the number of droplet diameter segments, di and ni are respectively the droplet diameter and number of No. i segment. The physical meaning of Sauter mean diameter is the ratio between volume and surface area of a certain droplet equals to that of total volume and total surface area of all droplets [22]. The smaller the dSMD is, the larger the specific surface area of a unit volume is. The simple relationship between specific surface area and Sauter mean diameter is shown as,
S¼
m X 2 ni pdi
,
i¼1
m X p 2 6 ni di ¼ d 6 SMD i¼1
ð2Þ
2.3.2. Nebulization efficiency The water supplied for dust collector is from the different pressures of liquid levels. The atomized mist is blown out and the rest left in cylinder. The nebulization efficiency g0 can be calculated by the formula,
g0 ¼ 1 q0 =q
Fig. 1. Structure and principle diagram of shear-impact-type atomized dust controller. 1-draught fan; 2-airflow intake; 3-spray fan; 4-diversion hole; 5colliding tooth; 6-water supply plant; 7-wind collector; 8-mist outlet; 9-water outlet.
217
ð3Þ
where q is the total water consumption, q0 is the water gathered from water outlet. There are mainly three reasons for water loss. Firstly, the droplets are too dense when water-flow is excessive, which can form large droplets though frequent impact. And the larger droplets can not be blown out from the dust collect because of their heavy mass. Secondly, the particle size of droplets are so small that their flowing speeds reduce when impacting on colliding tooth. Thus these tiny droplets assemble on the colliding tooth and form water film which will absorb more droplets resulting in the decrease in
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
nebulization efficiency. The assembly of water flow on the colliding tooth causes water loss. Thirdly, the poor design of the angle and density of colliding tooth together with the turbulence effect make droplets ineffectively atomize when they pass through the gap between colliding teeth. Then larger droplets will be adherent to the interior wall of atomized dust collector and flow into water outlet. In order to improve nebulization efficiency, we need to control water-flow in the range of 50–80 ml/s and colliding tooth angle in the range of 30–50°. 3. Experimental scheme Fig. 3 shows the experimental system and measuring points. Flameproof three-phase asynchronous motor (YB2-802-2) was selected to form a complete set of spray fan with rated power 1.1 kW and the synchronous speed 3000 r/min; C-4 airfoil blade was used with diameter 0.175 m and the total number of blades 8; diversion hole is a reducing pipe and the surface roughness is 0.1; the spray fan speed was adjusted by the frequency transformer, the diversion hole diameter was measured by micrometer; the dividing ruler was set up at the liquid level of water supply system; the exit velocity was measured by the airflow velocity transducer (TES-1341-type) and the dust concentration sensor (FC-1Atype) was placed to measure the dust concentration before and after spraying; the dust-settling chamber where the dust was blown into by spray fan, is 8 m length, being connected with the outlet of dust collector; the liquid in water outlet was collected by the measuring cylinder and the mist distance was measured by meter ruler. The dust samples collected for experiment were 50 m away from the coal working face in one coal mine. Their particle sizes are listed in Table 1 and the proximate analysis is listed in Table 2. The parameters of droplets size u, airflow velocity V, water consumption q, nebulization efficiency g0 and collection efficiency g under different rotating speed n, diversion hole-exit diameter d, and colliding tooth angle h were measured by keeping the water level 1 m above the dust collector and the dust concentration 200 mg/m3 during the experiment. 4. Results and discussion 4.1. Droplet size Fig. 4 shows the u–n curves with different h on the condition of d = 2 mm. It is clearly seen that u decreases monotonously with the increase of n under the same h. There is a conic relationship between u and n. Because the relative friction of airflow is fierce at a high speed, droplets break sufficiently. And a droplet is broken into finer particles after impacting on colliding tooth surface. The inflection point occurs around 1800 r/min with the corresponding granularity 30–80 lm, an ideal range mentioned in the literature [23], meeting the requirements of dust collection. It can be found in Fig. 4 that the dust collecting efficiency under h = 35°, 40° or
Table 1 Particle sizes of coal dust sample. Particle sizes of coal dust (lm)
Content
Particle number
<2
2–5
5–10
10–20
>20
468
182
106
22
3
Table 2 Proximate analysis of coal dust sample. Content
Moisture
Ash-content
Volatility
Fixed carbon
(wt%)
2.44
13.24
28.46
55.86
θ = 40° θ = 45° θ = 35° θ = 55° θ = 30°
250 200
u/ (μm)
218
150 100 50 0 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 4. u–n diagram with different h under d = 2 mm.
45° is significantly better than that of h = 55° or 30°. According to the momentum conservation theorem, when the jet angle of droplets from diversion hole has a vertical relationship with the colliding tooth, the impact energy becomes intensive and the droplets are atomized more effectively [24]. By comparing the curves when h = 35° with h = 45°, when n is high, the jet angle of droplets is affected greatly by centrifugal force, and the corresponding value of h should be larger. The droplets size is smaller than 25 lm if n > 2100 with h = 45°, and it continues to decline with the increase in rotating speed. The undersized droplets are hardly to absorb dust because of the water-flow turbulent in air. 4.2. Airflow velocity Fig. 5 denotes the v–n curve and y–v curve when d = 2 mm and h = 40°, where y represents the distance that the atomized droplets were erupted from dust collector. From the v–n curve, v increases quadratically with n, which conforms to the characteristics of axial fan, i.e. the faster the rotating speed is, the bigger airflow volume is. And the mist field moves forward under the action of wind power. The y–v curve is got in windless environment with the center of the dust collector 1 m above ground. The y–v curve shows that the mist distance is 6 m at rotating speed 1800 r/min, which expresses a linear trend on the whole. However, the particle size of a droplet is large at a low speed and the corresponding free falling time is short, thus the mist distance drifted with the wind is short, according to the basic parabola theories. The droplet size is small at a high speed and needs more time to fall. 4.3. Water consumption and nebulization efficiency
Fig. 3. Experimental system and measuring points. 1-transducer; 2-goniometer; 3dividing ruler; 4-airflow velocity transducer; 5-dust concentration sensor; 6-dustsettling coomber; 7-meter ruler; 8-measuring cylinder.
Fig. 6 shows the relationship between q and n with different d under h = 40°, and q increases with n. The friction and viscous force
219
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
1.0
3000
10
n
8
6
1500
η0
0.9
y
2000
y /(m)
n/ (r/min)
2500
4
d=1.5mm d=2mm d=2.5mm d=3mm
0.8
1000 2 500 5
10
15
0.7 500
0
20
1000
2500
3000
Fig. 7. g0–n diagrams with different d under h = 40°.
Fig. 5. v–n and y–v diagram when d = 2 mm and h = 40°.
d=1.5mm d=2mm d=2.5mm d=3mm
1.00
0.95
80 60
η
q/ (ml/s)
2000
n/(r/min)
V/ (m/s)
100
1500
0.90
d =2,θ =35° d =2,θ =40° d =2.5,θ =35° d =2.5,θ =40° d =1.5,θ =40° d =3, θ =40°
40 0.85
20 0 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 6. q–n diagrams with different d under h = 40°.
play an important role when a droplet flows in the diversion hole at a low speed, but the centrifugal force produced by the rotating of blades performs priority at a high speed. As shown in Fig. 6, there forms a quadratic curve between q and n when d is small. With the increase in d, the linear relationship has gradually become obvious, meanwhile, q adds obviously. Water consumption is less than 40 ml/s if d = 1.5, moderate when d = 2 or 2.5 and it changes smoothly with the increase in n; approximately 100 ml/s when d = 3 mm. The relationship between g0 and n with different d under h = 40° is shown in Fig. 7. It can be found that g0 presents a parabolic growing trend with the increase of n on the whole. But the nebulization efficiency decreases when the rotating speed is up to 2400 r/ min. Through observing the amount of water collected from the water outlet, we found that the water amount increased significantly when the rotating speed is higher than 2400 r/min. The reason may be that a liquid is divided into more tiny droplets (droplet size less than 25 lm, seen in Fig. 4) and these small droplets move slowly because of the air resistance, then adhere to the colliding tooth and flow into water outlet. The nebulization efficiency is not ideal (less than 95%) when d = 3. From Figs. 6 and 7, it is clear that the values of q and g0 are appropriate when d = 2 or 2.5; when d = 1.5, g0 attains its utmost, but water consumption is the least; when d = 3 water consumption is the most, but g0 is the poorest.
0.80 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 8. g–n diagram under different condition.
4.4. Collecting efficiency Fig. 8 shows the relationship between g and n under different d and h. g increases firstly then decreases with n, and the maximum g occurs when n is in the range of 1500 < n < 2100. The droplet size is around 40 lm when the maximum g occurs, as seen in Fig. 4, which validates that the atomized droplet size influences significantly on collecting efficiency. When d = 2 or 2.5, the values of g change little in the range of 1500 < n < 2100. Compared with h = 40°, the value of g is poor at a low speed when h = 35°, while behaves to the contrary at a high speed. The demarcation point is around 1800 r/min, which is similar to the law of particle size mentioned in Fig. 4. To some extent, the particle size can measure collecting efficiency. The particle size and water consumption are large when d = 3 and h = 40°, and its g is lower than that of when d = 2 or 2.5; the value of g is small under d = 1.5 when h = 40°and its water consumption is less as shown in Fig. 6. But it is not easy to form mist field and affects collecting efficiency.
5. Optimal analysis According to computational fluid dynamics, numerical simulation on the atomizing effect of the designed dust collector was
220
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
6. Conclusions
Fig. 9. Velocity vector of mist field.
(1) Droplet size decreases monotonously with the increase in rotating speed, and the relationship between them is a conic change. Suitable colliding tooth angle can improve impact effect and guarantee fine droplets. But the undersized droplets will adhere to colliding tooth and form water film, which cause water waste. Airflow velocity increases with rotating speed, and the mist distance is up to 6 m with rotational speed at 1800 r/min. (2) Oversized rotating speed and diversion hole-exit diameter can cause water-waste and reduce the nebulization efficiency, while the undersized of them is hardly to form enough mist fields and affects collecting efficiency. Nebulization efficiency behaved abnormally at rotating speed of 2400 r/min. If water-flow is sufficient, collecting efficiency is greatly influenced by droplet size. (3) With full consideration of security, water consumption, nebulization efficiency and collecting efficiency, the optimal operating condition of dust controller was found with rotating speed in the range of 1500–2100 r/min, diversion holeexit diameter 2–2.5 mm and colliding tooth angle 35–40°. In this case, the nebulization efficiency reaches 96.3% and the collecting efficiency tops 98.6%.
Acknowledgements
Fig. 10. Droplet trajectories of mist field.
carried by fluid analysis softwares (Gambit 2.2.30, Fluent 6.3) on the same kinetic and geometric parameters. And the diagrams of velocity vectors and traveling trajectories for droplets were obtained under different combined parameters. Figs. 9 and 10 respectively signified the mist field of velocity vector and traveling trajectories under the condition of n = 1800 r/min, d = 2 mm and h = 35°. It is clear that the droplet size is around 36 lm and the distribution of mist field is uniform and an ideal atomizing effect has achieved. The results show the feasibility and reliability of numerical simulation on the design of atomized dust collector. Since the simulation is easier to do than experimental study, and the simulation research conclusion is reliable, the use of calculating theory and numerical simulation to design the structure parameters of atomized dust collector before experiment is an effective method for the design of atomized dust collector. The natural frequency of dust collector and the rational frequency of spray fan occur resonance at a certain speed, which will affect the operating security of dust collector. According to the experiment, when the frequency of spray fan is in the range of 41.2–46.4 Hz, the amplitude of mechanical vibration of dust collector increases significantly with abnormal noise, which agrees well with Ref. [25]. Therefore, the dust collector should avoid running in the range of resonant frequency. On the precondition of safety and low water consumption, higher nebulization and collecting efficiency are important standards for evaluating the comprehensive operating parameters. From Figs. 4–8, we can see that droplet size can be reasonably controlled around 50 lm when n takes a suitable value, with higher g and effective mist distance. The oversized d can cause water waste, but the undersized can not form enough mist field. Suitable h will improve nebulization efficiency and reduce water cost. In order to keep a state of safety, high efficiency and low water consumption, the most suitable parameters of dust collector are n 1500–2100 r/min, d 2–2.5 mm and h 35–40°, with the corresponding g0 and g being 96.3% and 98.6%.
The authors gratefully acknowledge the financial support of the Joint Funds of the National Natural Science Foundation of China (No. U1261107) and the Fundamental Research Funds for the Natural Science of Shanxi Province (No. 2012011018-1). References [1] J.F. Colinet, Best Practices for Dust Control in Coal Mining, US Department of Human Health Services, Pittsburgh, PA, 2010, p. 65. [2] Y.Q. Li, Y.P. Qin, X.B. Yang, Procedia Engineering, vol. 26, Elsevier Press, Beijing, 2011, p. 738. [3] Qingzhao Li, Baiquan Lin, Shuai Zhao, Huaming Dai, Surface physical properties and its effects on the wetting behaviors of respirable coal mine dust, Powder Technol. 233 (2013) 137–145. [4] D.J. Jing, S.C. Ge, J. Liu, Coal-dust motion law and control technology of the feeder, Adv. Res. Ind. 204–210 (2011) 928–931. [5] Zhiguo Zhao, Maozhao XIE, Numerical simulation about interaction between pressure swirl spray and hot porous medium, Energy Convers. Manage. 49 (2008) 1047–1055. [6] L.Z. Jin, J.P. Li, Y.F. Sun, Prevention Theory of Mine Dust, Scientific Press, Beijing, 2010. 156. [7] Ri Li, Nasser Ashgriz, Sanjeev Chandra, Droplet generation from pulsed microjets, Exp. Thermal Fluid Sci. 32 (2008) 1679–1686. [8] S. Xavier, B. Denis, C. Sandrine, Dominique Thomas, Roland Régnier, Consequences of high transitory airflow flows generated by segmented pulse-jet cleaning of dust collector filter bags, Powder Technol. 201 (2010) 37–43. [9] S. Shaaban, Numerical optimization and experimental investigation of the aerodynamic performance of a three-stage gas–solid separator, Chem. Eng. Res. Des. 89 (2011) 29–36. [10] D.I. Misyulya, New designs of devices for a decrease in power consumption of cyclone dust collectors, Russ. J. Non-Ferr. Met. 53 (1) (2012) 67–72. [11] X. Jiang, G.A. Siamas, K. Jagus, T.G. Karayiannis, Physical modelling and advanced simulations of gas–liquid two-phase jet flows in atomizing and sprays, Prog. Energy Combust. Sci. 36 (2010) 131–167. [12] JQg Zhen, Y.Q. Luo, J. Zhang, H.L. Long, The experiment of best gasconsumption rate on the Pneumatic atomizing, J. Agric. Mach. 38 (10) (2007). 195-120. [13] R. Balevicius, R. Kacianauskas, Z. Mroz, I. Sielamowicz, Analysis and DEM simulation of granular material flow patterns in hopper models of different shapes, Adv. Powder Technol. 22 (2011) 226–235. [14] Junxiang Liu, Qingbo Yu, Qiang Guo, Experimental investigation of liquid disintegration by rotary cups, Chem. Eng. Sci. 73 (2012) 44–50. [15] X.Z. Wang, C.Y. Yu, C.J. Zhou, Spray Drying, second ed., Chemical Industry Press, 2003, pp. 109–115. [16] R. Hadef, B. Lenze, Measurements of droplets characteristics in a swirlstabilized spray flame, Exp. Thermal Fluid Sci. 30 (2005) 117–130.
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221 [17] C.E. Ejim, M.A. Rahman, A. Amirfazli, B.A. Fleck, Effects of liquid viscosity and surface tension on atomizing in two-phase, gas/liquid fluid coker nozzles, Fuel 89 (2010) 1872–1882. [18] A. Deniz Eksi, Benzer Hakan, Sargin Ays_egul, Genc Omurden, A new method for determination of fine particle breakage, Miner. Eng. 24 (2011) 216–220. [19] Julián Palacios, Julio Hernández, Pablo Gómez, Claudio Zanzi, Joaquín López, Experimental study of splashing patterns and the splashing/deposition threshold in drop impacts onto dry smooth solid surfaces, Exp. Thermal Fluid Sci. 44 (2013) 571–582. [20] G.E. Cossali, M. Marengo, M. Santini, Secondary atomisation produced by single drop vertical impacts onto heated surfaces, Exp. Thermal Fluid Sci. 29 (2005) 937–946.
221
[21] D. Liu, Q. He, G.M. Evans, Penetration behaviour of individual hydrophilic particle at a gas–liquid interface, Adv. Powder Technol. 21 (2009) 401–411. [22] F. Liu, X.J. Zhang, Y. Zhang, Experimental study on droplet spectrum of water jet flow, J. Hydroelectr. Eng. 31 (1) (2012) 118–124. [23] G. Zhou, W.M. Cheng, G. Wang, X.F. Cui, Experiment research of the coupling relationship between dust field and droplet field about fully mechanized and roof caving workface, J. China Coal Soc. 35 (10) (2010) 1660–1667. [24] H.E. Zheng, Y. Gao, X. Gu, G. Wang, Investigating a droplet wall impact model, J. Univ. Eng. Harbin 30 (3) (2009) 267–272. [25] X.C. Li, Y.F. Hu, W. Zhang, M.J. Chen, Q. Li, Effect of operation parameters of dust collector, J. Univ. Cent. South (Sci. Technol.) 44 (2) (2013) 862–868.
Contents lists available at ScienceDirect
Experimental Thermal and Fluid Science journal homepage: www.elsevier.com/locate/etfs
Experimental research on the comprehensive operating parameters of atomized dust collector Qiuzu Liu, Ziming Kou ⇑, Guijun Gao, Tengyan Hou College of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, PR China Shanxi Provincial Engineering Laboratory (Research Center) for Mine Fluid Control, Taiyuan 030024, PR China
a r t i c l e
i n f o
Article history: Received 8 April 2014 Received in revised form 12 December 2014 Accepted 5 January 2015 Available online 13 January 2015 Keywords: Atomized dust collector Operating parameters Nebulization efficiency Collecting efficiency
a b s t r a c t A shear-impact-type atomized dust controller was designed by combining the rotary spray blades and axial flow fan, and the droplet atomizing process included two steps: shear-atomizing and impact-atomizing. The comprehensive operating parameters of this dust controller were studied by measuring different droplet size, airflow velocity, water consumption, nebulization efficiency, and collecting efficiency under different rotating speed, diversion hole-exit diameter, and colliding tooth angle. The relationships among them have been particularly analyzed. Results indicated that the droplet size is greatly influenced by rotating speed; the airflow velocity enhances monotonously with the increase in rotating speed. Excessive rotating speed and diversion hole-exit diameter can cause water waste, and suitable colliding tooth angle h can improve nebulization efficiency. The optimal operating conditions were obtained with rotating speed 1500–2100 r/min, diversion hole-exit diameter 2–2.5 mm and colliding tooth angle 35– 40° by fully considering security, water consumption, nebulization and collecting efficiencies. In this case, the nebulization efficiency exceeds 96.3% and the collecting efficiency tops 98.6%. Ó 2015 Elsevier Inc. All rights reserved.
1. Introduction High concentration of dust in coal mine may cause many problems, such as dust (gas) explosion and pneumoconiosis because of long-term inhalation of respirable dust [1,2]. For security, it is rather significant to select a proper way to reduce dust [3–5]. Spraying dust is one of the most commonly used methods for dust collection, with the advantages of high efficiency and low cost [6]. At present there are mainly two ways to achieve spray dust, i.e. jet nozzle and negative pressure suction. The former is flexible and easy to control, but easy to be blocked by impurities in water or dust in working environment [7,8]. The latter mainly equips with bag or siphon filter, with the advantage of high efficiency for dust collection, but difficult to be maintained [9,10]. A new type of gas– water mixing nozzle developed by Zhang et al. improved the graining precision, but difficult to match the parameters of mixing cavity [11]. Jiang et al. studied the experiment on foam-dust collector, optimized its designing parameters and improved dust collecting efficiency. But it costs highly in application [12]. Rotary-atomized dust collector, a type of dust collecting equipment, disintegrates a liquid by the centrifugal force results from ⇑ Corresponding author. Tel.: +86 0351 6149095. E-mail address: [email protected] (Z. Kou). http://dx.doi.org/10.1016/j.expthermflusci.2015.01.001 0894-1777/Ó 2015 Elsevier Inc. All rights reserved.
high speed rotating components. This atomizer has been widely used in industry, especially in the fields of dust collection and humidification [13]. Recently, most studies on rotary atomized dust collector have been launched from the shear fracture of liquid membrane, but ideal particle sizes are hard to obtained [14]. Wang et al. [15] investigated the mechanism of direct drop formation and ligament formation in a rotary cup which were recorded by a highspeed camera and explained the fracturing process of liquid film. Hadef and Lenze [16] measured a kerosene air blast atomized spray flame between two coswirling air streams by a phase–doppler particle sizing system, and found a small liquid exists in the centre of the combustor due to larger droplets with the swirl effect. Droplets can be effectively broken at a high speed through impacting on solid surface, which attracts many researchers’ attention [17,18]. Julián et al. [19] studied the drop impacting outcome regimes in a broad experimental condition, and illustrated the crushing process of droplet. Cossali et al. [20] reported an experimental analysis of secondary atomizing produced by a single drop impacting on solid surface, analyzed the morphology of drop spreading and breaking-up in details. Liu et al. [21] investigated a hydrophilic particle impact on a gas–liquid interface and found the particle moving velocity, viscosity and surface tension had a great influence on droplet deformation. Up to now, because of
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
droplet colliding process is difficult to follow, studies on droplet impact atomizing in application are seldom mentioned. The main purpose of this study is to develop a device that integrates the rotary atomizing and impact crushing to find an optimal condition in the following aspects: droplet size, airflow velocity, nebulization efficiency and collection efficiency on the basis of analyzing the comprehensive operating parameters (rotating speed, diversion hole-exit diameter, and colliding tooth angle) by taking consideration of high efficiency, less water consumption and safety. Thus Multi-point real-time testing of computer technology and frequency conversion technology were applied, and the performance of atomizing precipitator was tested in a more broad experimental condition. 2. Principle and parameters 2.1. Shear-impact-type atomized dust controller The structure and principle of shear-impact-type atomized dust controller is shown in Fig. 1. The device combines rotary spray blades and axial flow fan, integrating shearing and impacting atomizing. Its core atomizing component is the spray fan with a straight diversion hole inside, making water flow smoothly and reducing water consumption to achieve the combination of wind wheel and nozzle head successfully. The dust collecting process can be divided into two steps: shear-atomizing and impact-atomizing. In the former step, the droplet is thrown out from diversion hole at s high rotational speed, then it is atomized into droplets with the interaction of aerodynamic and centrifugal force. In the latter process, the atomized droplets run into colliding tooth at a high speed and then are broken into smaller droplets. The positional relationship between spray fan and colliding tooth is shown in Fig. 2, where h is the colliding tooth angle. The dust is captured by the atomized water mist which is blown out by spray fan.
Fig. 2. Installation diagram of colliding tooth. 1-colliding tooth; 2-diversion holeexit; 3-spray fan.
pressibility of liquid, the pressure inside a liquid increases immediately when impacting on the colliding tooth at a high speed. When the internal pressure is greater than the combined action of the external pressure, the droplet surface tension and internal cohesion, the liquid will rapidly disintegrate into tiny droplets and form mist field. The atomizing effect is related to the droplet sizes which are affected by the rotating speed and diversion hole-exit diameter; and also associated with the droplet impact angle which can be adjusted by colliding tooth angle. The breakup process of droplets is related to many factors. Here three main factors, i.e. rotating speed, diversion hole-exit diameter and colliding tooth angle are considered. 2.3. Parameters 2.3.1. Droplet size A droplet is atomized by the dust collector, whose characteristic parameters can fully reflect droplet particle size. Here the Sauter mean diameter dSMD is introduced.
dSMD
m X 3 ¼ nidi
,
i¼1
2.2. Droplets formation process When a liquid reaches the diversion hole along the flow channel under the action of centrifugal force, there is a relative motion between the liquid and air because of high-speed rotating blade. The liquid is stretched gradually, then ruptured when it overcomes the shackles of the droplet adhesion and surface tension. Due to the centrifugal force generated by the rotating blade, the droplets have a jet velocity when departing from the diversion channel. The moving droplets interact with the surrounding air to achieve atomizing, which is similar to the nozzle atomizing. The blade speed not only determines the velocity of‘ moving droplets, but also influences the friction between the droplets and air. The average diameter of shear atomized droplets is relatively large (generally hundreds of microns), therefore, the droplet diameter needs to decrease further by atomizing. Because of the incom-
m X 2 nidi
ð1Þ
i¼1
where m is the number of droplet diameter segments, di and ni are respectively the droplet diameter and number of No. i segment. The physical meaning of Sauter mean diameter is the ratio between volume and surface area of a certain droplet equals to that of total volume and total surface area of all droplets [22]. The smaller the dSMD is, the larger the specific surface area of a unit volume is. The simple relationship between specific surface area and Sauter mean diameter is shown as,
S¼
m X 2 ni pdi
,
i¼1
m X p 2 6 ni di ¼ d 6 SMD i¼1
ð2Þ
2.3.2. Nebulization efficiency The water supplied for dust collector is from the different pressures of liquid levels. The atomized mist is blown out and the rest left in cylinder. The nebulization efficiency g0 can be calculated by the formula,
g0 ¼ 1 q0 =q
Fig. 1. Structure and principle diagram of shear-impact-type atomized dust controller. 1-draught fan; 2-airflow intake; 3-spray fan; 4-diversion hole; 5colliding tooth; 6-water supply plant; 7-wind collector; 8-mist outlet; 9-water outlet.
217
ð3Þ
where q is the total water consumption, q0 is the water gathered from water outlet. There are mainly three reasons for water loss. Firstly, the droplets are too dense when water-flow is excessive, which can form large droplets though frequent impact. And the larger droplets can not be blown out from the dust collect because of their heavy mass. Secondly, the particle size of droplets are so small that their flowing speeds reduce when impacting on colliding tooth. Thus these tiny droplets assemble on the colliding tooth and form water film which will absorb more droplets resulting in the decrease in
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
nebulization efficiency. The assembly of water flow on the colliding tooth causes water loss. Thirdly, the poor design of the angle and density of colliding tooth together with the turbulence effect make droplets ineffectively atomize when they pass through the gap between colliding teeth. Then larger droplets will be adherent to the interior wall of atomized dust collector and flow into water outlet. In order to improve nebulization efficiency, we need to control water-flow in the range of 50–80 ml/s and colliding tooth angle in the range of 30–50°. 3. Experimental scheme Fig. 3 shows the experimental system and measuring points. Flameproof three-phase asynchronous motor (YB2-802-2) was selected to form a complete set of spray fan with rated power 1.1 kW and the synchronous speed 3000 r/min; C-4 airfoil blade was used with diameter 0.175 m and the total number of blades 8; diversion hole is a reducing pipe and the surface roughness is 0.1; the spray fan speed was adjusted by the frequency transformer, the diversion hole diameter was measured by micrometer; the dividing ruler was set up at the liquid level of water supply system; the exit velocity was measured by the airflow velocity transducer (TES-1341-type) and the dust concentration sensor (FC-1Atype) was placed to measure the dust concentration before and after spraying; the dust-settling chamber where the dust was blown into by spray fan, is 8 m length, being connected with the outlet of dust collector; the liquid in water outlet was collected by the measuring cylinder and the mist distance was measured by meter ruler. The dust samples collected for experiment were 50 m away from the coal working face in one coal mine. Their particle sizes are listed in Table 1 and the proximate analysis is listed in Table 2. The parameters of droplets size u, airflow velocity V, water consumption q, nebulization efficiency g0 and collection efficiency g under different rotating speed n, diversion hole-exit diameter d, and colliding tooth angle h were measured by keeping the water level 1 m above the dust collector and the dust concentration 200 mg/m3 during the experiment. 4. Results and discussion 4.1. Droplet size Fig. 4 shows the u–n curves with different h on the condition of d = 2 mm. It is clearly seen that u decreases monotonously with the increase of n under the same h. There is a conic relationship between u and n. Because the relative friction of airflow is fierce at a high speed, droplets break sufficiently. And a droplet is broken into finer particles after impacting on colliding tooth surface. The inflection point occurs around 1800 r/min with the corresponding granularity 30–80 lm, an ideal range mentioned in the literature [23], meeting the requirements of dust collection. It can be found in Fig. 4 that the dust collecting efficiency under h = 35°, 40° or
Table 1 Particle sizes of coal dust sample. Particle sizes of coal dust (lm)
Content
Particle number
<2
2–5
5–10
10–20
>20
468
182
106
22
3
Table 2 Proximate analysis of coal dust sample. Content
Moisture
Ash-content
Volatility
Fixed carbon
(wt%)
2.44
13.24
28.46
55.86
θ = 40° θ = 45° θ = 35° θ = 55° θ = 30°
250 200
u/ (μm)
218
150 100 50 0 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 4. u–n diagram with different h under d = 2 mm.
45° is significantly better than that of h = 55° or 30°. According to the momentum conservation theorem, when the jet angle of droplets from diversion hole has a vertical relationship with the colliding tooth, the impact energy becomes intensive and the droplets are atomized more effectively [24]. By comparing the curves when h = 35° with h = 45°, when n is high, the jet angle of droplets is affected greatly by centrifugal force, and the corresponding value of h should be larger. The droplets size is smaller than 25 lm if n > 2100 with h = 45°, and it continues to decline with the increase in rotating speed. The undersized droplets are hardly to absorb dust because of the water-flow turbulent in air. 4.2. Airflow velocity Fig. 5 denotes the v–n curve and y–v curve when d = 2 mm and h = 40°, where y represents the distance that the atomized droplets were erupted from dust collector. From the v–n curve, v increases quadratically with n, which conforms to the characteristics of axial fan, i.e. the faster the rotating speed is, the bigger airflow volume is. And the mist field moves forward under the action of wind power. The y–v curve is got in windless environment with the center of the dust collector 1 m above ground. The y–v curve shows that the mist distance is 6 m at rotating speed 1800 r/min, which expresses a linear trend on the whole. However, the particle size of a droplet is large at a low speed and the corresponding free falling time is short, thus the mist distance drifted with the wind is short, according to the basic parabola theories. The droplet size is small at a high speed and needs more time to fall. 4.3. Water consumption and nebulization efficiency
Fig. 3. Experimental system and measuring points. 1-transducer; 2-goniometer; 3dividing ruler; 4-airflow velocity transducer; 5-dust concentration sensor; 6-dustsettling coomber; 7-meter ruler; 8-measuring cylinder.
Fig. 6 shows the relationship between q and n with different d under h = 40°, and q increases with n. The friction and viscous force
219
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
1.0
3000
10
n
8
6
1500
η0
0.9
y
2000
y /(m)
n/ (r/min)
2500
4
d=1.5mm d=2mm d=2.5mm d=3mm
0.8
1000 2 500 5
10
15
0.7 500
0
20
1000
2500
3000
Fig. 7. g0–n diagrams with different d under h = 40°.
Fig. 5. v–n and y–v diagram when d = 2 mm and h = 40°.
d=1.5mm d=2mm d=2.5mm d=3mm
1.00
0.95
80 60
η
q/ (ml/s)
2000
n/(r/min)
V/ (m/s)
100
1500
0.90
d =2,θ =35° d =2,θ =40° d =2.5,θ =35° d =2.5,θ =40° d =1.5,θ =40° d =3, θ =40°
40 0.85
20 0 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 6. q–n diagrams with different d under h = 40°.
play an important role when a droplet flows in the diversion hole at a low speed, but the centrifugal force produced by the rotating of blades performs priority at a high speed. As shown in Fig. 6, there forms a quadratic curve between q and n when d is small. With the increase in d, the linear relationship has gradually become obvious, meanwhile, q adds obviously. Water consumption is less than 40 ml/s if d = 1.5, moderate when d = 2 or 2.5 and it changes smoothly with the increase in n; approximately 100 ml/s when d = 3 mm. The relationship between g0 and n with different d under h = 40° is shown in Fig. 7. It can be found that g0 presents a parabolic growing trend with the increase of n on the whole. But the nebulization efficiency decreases when the rotating speed is up to 2400 r/ min. Through observing the amount of water collected from the water outlet, we found that the water amount increased significantly when the rotating speed is higher than 2400 r/min. The reason may be that a liquid is divided into more tiny droplets (droplet size less than 25 lm, seen in Fig. 4) and these small droplets move slowly because of the air resistance, then adhere to the colliding tooth and flow into water outlet. The nebulization efficiency is not ideal (less than 95%) when d = 3. From Figs. 6 and 7, it is clear that the values of q and g0 are appropriate when d = 2 or 2.5; when d = 1.5, g0 attains its utmost, but water consumption is the least; when d = 3 water consumption is the most, but g0 is the poorest.
0.80 500
1000
1500
2000
2500
3000
n/(r/min) Fig. 8. g–n diagram under different condition.
4.4. Collecting efficiency Fig. 8 shows the relationship between g and n under different d and h. g increases firstly then decreases with n, and the maximum g occurs when n is in the range of 1500 < n < 2100. The droplet size is around 40 lm when the maximum g occurs, as seen in Fig. 4, which validates that the atomized droplet size influences significantly on collecting efficiency. When d = 2 or 2.5, the values of g change little in the range of 1500 < n < 2100. Compared with h = 40°, the value of g is poor at a low speed when h = 35°, while behaves to the contrary at a high speed. The demarcation point is around 1800 r/min, which is similar to the law of particle size mentioned in Fig. 4. To some extent, the particle size can measure collecting efficiency. The particle size and water consumption are large when d = 3 and h = 40°, and its g is lower than that of when d = 2 or 2.5; the value of g is small under d = 1.5 when h = 40°and its water consumption is less as shown in Fig. 6. But it is not easy to form mist field and affects collecting efficiency.
5. Optimal analysis According to computational fluid dynamics, numerical simulation on the atomizing effect of the designed dust collector was
220
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221
6. Conclusions
Fig. 9. Velocity vector of mist field.
(1) Droplet size decreases monotonously with the increase in rotating speed, and the relationship between them is a conic change. Suitable colliding tooth angle can improve impact effect and guarantee fine droplets. But the undersized droplets will adhere to colliding tooth and form water film, which cause water waste. Airflow velocity increases with rotating speed, and the mist distance is up to 6 m with rotational speed at 1800 r/min. (2) Oversized rotating speed and diversion hole-exit diameter can cause water-waste and reduce the nebulization efficiency, while the undersized of them is hardly to form enough mist fields and affects collecting efficiency. Nebulization efficiency behaved abnormally at rotating speed of 2400 r/min. If water-flow is sufficient, collecting efficiency is greatly influenced by droplet size. (3) With full consideration of security, water consumption, nebulization efficiency and collecting efficiency, the optimal operating condition of dust controller was found with rotating speed in the range of 1500–2100 r/min, diversion holeexit diameter 2–2.5 mm and colliding tooth angle 35–40°. In this case, the nebulization efficiency reaches 96.3% and the collecting efficiency tops 98.6%.
Acknowledgements
Fig. 10. Droplet trajectories of mist field.
carried by fluid analysis softwares (Gambit 2.2.30, Fluent 6.3) on the same kinetic and geometric parameters. And the diagrams of velocity vectors and traveling trajectories for droplets were obtained under different combined parameters. Figs. 9 and 10 respectively signified the mist field of velocity vector and traveling trajectories under the condition of n = 1800 r/min, d = 2 mm and h = 35°. It is clear that the droplet size is around 36 lm and the distribution of mist field is uniform and an ideal atomizing effect has achieved. The results show the feasibility and reliability of numerical simulation on the design of atomized dust collector. Since the simulation is easier to do than experimental study, and the simulation research conclusion is reliable, the use of calculating theory and numerical simulation to design the structure parameters of atomized dust collector before experiment is an effective method for the design of atomized dust collector. The natural frequency of dust collector and the rational frequency of spray fan occur resonance at a certain speed, which will affect the operating security of dust collector. According to the experiment, when the frequency of spray fan is in the range of 41.2–46.4 Hz, the amplitude of mechanical vibration of dust collector increases significantly with abnormal noise, which agrees well with Ref. [25]. Therefore, the dust collector should avoid running in the range of resonant frequency. On the precondition of safety and low water consumption, higher nebulization and collecting efficiency are important standards for evaluating the comprehensive operating parameters. From Figs. 4–8, we can see that droplet size can be reasonably controlled around 50 lm when n takes a suitable value, with higher g and effective mist distance. The oversized d can cause water waste, but the undersized can not form enough mist field. Suitable h will improve nebulization efficiency and reduce water cost. In order to keep a state of safety, high efficiency and low water consumption, the most suitable parameters of dust collector are n 1500–2100 r/min, d 2–2.5 mm and h 35–40°, with the corresponding g0 and g being 96.3% and 98.6%.
The authors gratefully acknowledge the financial support of the Joint Funds of the National Natural Science Foundation of China (No. U1261107) and the Fundamental Research Funds for the Natural Science of Shanxi Province (No. 2012011018-1). References [1] J.F. Colinet, Best Practices for Dust Control in Coal Mining, US Department of Human Health Services, Pittsburgh, PA, 2010, p. 65. [2] Y.Q. Li, Y.P. Qin, X.B. Yang, Procedia Engineering, vol. 26, Elsevier Press, Beijing, 2011, p. 738. [3] Qingzhao Li, Baiquan Lin, Shuai Zhao, Huaming Dai, Surface physical properties and its effects on the wetting behaviors of respirable coal mine dust, Powder Technol. 233 (2013) 137–145. [4] D.J. Jing, S.C. Ge, J. Liu, Coal-dust motion law and control technology of the feeder, Adv. Res. Ind. 204–210 (2011) 928–931. [5] Zhiguo Zhao, Maozhao XIE, Numerical simulation about interaction between pressure swirl spray and hot porous medium, Energy Convers. Manage. 49 (2008) 1047–1055. [6] L.Z. Jin, J.P. Li, Y.F. Sun, Prevention Theory of Mine Dust, Scientific Press, Beijing, 2010. 156. [7] Ri Li, Nasser Ashgriz, Sanjeev Chandra, Droplet generation from pulsed microjets, Exp. Thermal Fluid Sci. 32 (2008) 1679–1686. [8] S. Xavier, B. Denis, C. Sandrine, Dominique Thomas, Roland Régnier, Consequences of high transitory airflow flows generated by segmented pulse-jet cleaning of dust collector filter bags, Powder Technol. 201 (2010) 37–43. [9] S. Shaaban, Numerical optimization and experimental investigation of the aerodynamic performance of a three-stage gas–solid separator, Chem. Eng. Res. Des. 89 (2011) 29–36. [10] D.I. Misyulya, New designs of devices for a decrease in power consumption of cyclone dust collectors, Russ. J. Non-Ferr. Met. 53 (1) (2012) 67–72. [11] X. Jiang, G.A. Siamas, K. Jagus, T.G. Karayiannis, Physical modelling and advanced simulations of gas–liquid two-phase jet flows in atomizing and sprays, Prog. Energy Combust. Sci. 36 (2010) 131–167. [12] JQg Zhen, Y.Q. Luo, J. Zhang, H.L. Long, The experiment of best gasconsumption rate on the Pneumatic atomizing, J. Agric. Mach. 38 (10) (2007). 195-120. [13] R. Balevicius, R. Kacianauskas, Z. Mroz, I. Sielamowicz, Analysis and DEM simulation of granular material flow patterns in hopper models of different shapes, Adv. Powder Technol. 22 (2011) 226–235. [14] Junxiang Liu, Qingbo Yu, Qiang Guo, Experimental investigation of liquid disintegration by rotary cups, Chem. Eng. Sci. 73 (2012) 44–50. [15] X.Z. Wang, C.Y. Yu, C.J. Zhou, Spray Drying, second ed., Chemical Industry Press, 2003, pp. 109–115. [16] R. Hadef, B. Lenze, Measurements of droplets characteristics in a swirlstabilized spray flame, Exp. Thermal Fluid Sci. 30 (2005) 117–130.
Q. Liu et al. / Experimental Thermal and Fluid Science 62 (2015) 216–221 [17] C.E. Ejim, M.A. Rahman, A. Amirfazli, B.A. Fleck, Effects of liquid viscosity and surface tension on atomizing in two-phase, gas/liquid fluid coker nozzles, Fuel 89 (2010) 1872–1882. [18] A. Deniz Eksi, Benzer Hakan, Sargin Ays_egul, Genc Omurden, A new method for determination of fine particle breakage, Miner. Eng. 24 (2011) 216–220. [19] Julián Palacios, Julio Hernández, Pablo Gómez, Claudio Zanzi, Joaquín López, Experimental study of splashing patterns and the splashing/deposition threshold in drop impacts onto dry smooth solid surfaces, Exp. Thermal Fluid Sci. 44 (2013) 571–582. [20] G.E. Cossali, M. Marengo, M. Santini, Secondary atomisation produced by single drop vertical impacts onto heated surfaces, Exp. Thermal Fluid Sci. 29 (2005) 937–946.
221
[21] D. Liu, Q. He, G.M. Evans, Penetration behaviour of individual hydrophilic particle at a gas–liquid interface, Adv. Powder Technol. 21 (2009) 401–411. [22] F. Liu, X.J. Zhang, Y. Zhang, Experimental study on droplet spectrum of water jet flow, J. Hydroelectr. Eng. 31 (1) (2012) 118–124. [23] G. Zhou, W.M. Cheng, G. Wang, X.F. Cui, Experiment research of the coupling relationship between dust field and droplet field about fully mechanized and roof caving workface, J. China Coal Soc. 35 (10) (2010) 1660–1667. [24] H.E. Zheng, Y. Gao, X. Gu, G. Wang, Investigating a droplet wall impact model, J. Univ. Eng. Harbin 30 (3) (2009) 267–272. [25] X.C. Li, Y.F. Hu, W. Zhang, M.J. Chen, Q. Li, Effect of operation parameters of dust collector, J. Univ. Cent. South (Sci. Technol.) 44 (2) (2013) 862–868.