Closed SDBD-driven two-stage electrostatic precipitator

Journal of Cleaner Production 226 (2019) 74e84

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Closed SDBD-driven two-stage electrostatic precipitator
ski a, *, Artur Berendt a, Jerzy Mizeraczyk b Mateusz Tan a b

Institute of Fluid Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-231, Gdansk, Poland Department of Marine Electronics, Gdynia Maritime University, Morska 81-87, 81-225, Gdynia, Poland

a r t i c l e i n f o

a b s t r a c t

Article history: Received 6 September 2018 Received in revised form 22 December 2018 Accepted 26 March 2019 Available online 2 April 2019

Recently, the so-called two-stage electrostatic precipitators (ESPs) have again become an object of interest due to their usefulness in efficient collection of PM2.5 particles (of size < 2.5 mm) from polluted air. A two-stage ESP consists of two sections: an air ionisation and particle charging section (called a charging section) and a collecting section for precipitating the charged particles. The ESP has to be equipped with a means for forcing the polluted air to pass through both sections. Various forms of the corona discharges (DC, AC, pulsed) have been used for the air ionisation and particle charging in the first section, while the particle collecting section has usually been electrically supplied with a DC voltage of an amplitude insufficient for the corona discharge onset in this section. In this paper, we propose and present the use of the so-called surface dielectric barrier discharge (SDBD) in the form of an electrohydrodynamic (EHD) actuator as an alternative discharge source in the two-phase fluid (air þ particles) of the two-stage ESP, instead of the commonly used corona discharge. Although different in terms of the electrical arrangement, discharge characteristics and morphology, the SDBD can play a similar role as the corona discharge plays in the two-stage ESPs. First, in the two-phase fluid (air þ particle) of two-stage ESP the SDBD would be capable of generating bipolar (positive and negative) ions in air, which in turn would charge bipolarly the particles suspended in it. The bipolarly charged particles would agglomerate into larger charged particles, the collection of which is more efficient when subjected to the electrostatic force in the collecting section. Second, the SBDB would induce a unidirectional EHD flow in the twophase fluid. The EHD flow can either enhance the primary flow of the two-phase fluid or act as a sole flow actuator (rather in relatively small ESPs). The suitability of SDBD for the two-stage ESP systems have been tested in the experiment performed by us using a laboratory-scale closed-volume SDBD-driven two-stage ESP. The experiment comprised measurements of the SDBD discharge characteristics, PTV (Particle Tracking Velocimetry) indirect detecting the production of bipolarly charged particles by the SDBD and then monitoring their trajectories in the collecting section of the SDBD-driven ESP, and qualitative and quantitative studies of the particle removal (or collection) efficiency of the closed SDBDdriven ESP. The PTV monitoring of the particle trajectories was aimed at visualization of the collecting section operation. The experimental results showed that the lab-scale SDBD-driven ESP has proved successful in collecting the particles suspended in air in a closed volume. However, it turned out that the presented lab-scale SDBD-driven ESP was not optimally designed. Despite this, it exhibited the particle removal efficiency similar to that of the single needle-to-plate negative DC corona one-stage ESP, considered as the basic unit for forming larger ESPs. After optimizing the design of lab-scale SDBD-driven ESP unit, we intend to study its performance in flow system, i.e. for the removal of particles from a particle-polluted air stream. © 2019 Elsevier Ltd. All rights reserved.

Keywords: Air purification Two-stage electrostatic precipitator Particle filtering devices Surface dielectric barrier discharge Electrohydrodynamic actuator Particle tracking velocimetry

1. Introduction The energy sector based on coal combustion for producing heat and electricity, cement plants and diesel-driven transport means * Corresponding author.
ski). E-mail address: [email protected] (M. Tan https://doi.org/10.1016/j.jclepro.2019.03.280 0959-6526/© 2019 Elsevier Ltd. All rights reserved.

produce huge amounts of solid particles. They can be captured with high mass efficiency, exceeding 99%, by various filtering devices (Neeft et al., 1996; Guan et al., 2015; Di Natale and Carotenuto, 2015; Stamatellou and Stamatelos, 2017). Examples of such devices are filtering cyclones, bag filters, granular-bed filters, scrubbers and electrostatic precipitators. However, the fractional removal (or collection) efficiency (the percentage of the number of


ski et al. / Journal of Cleaner Production 226 (2019) 74e84 M. Tan

collected particles for a given particle dimension range) of those devices for small particles, the dimensions of which are smaller than 2.5 mm (i.e. the so-called PM2.5 fraction) is unsatisfactory (approximately 80% (Koizumi et al., 2000; Zhu et al., 2010),). This fact is alarming, since numerous studies have confirmed that the presence of PM2.5 fraction in the atmosphere results in an increase in the occurrence of respiratory and circulatory system diseases, allergies, asthma and lung cancers that can lead to premature death (Goodarzi, 2006; Radulescu et al., 2015; Meng et al., 2016). Therefore, the current emission of immense number of particle fraction PM2.5 into the atmosphere requires the development of new, more efficient methods of capturing such small particles. One of the means of increasing the removal efficiency in the PM2.5 particle size range is improving the performance of the existing filtering devices by implementing electrostatic processes in them or by upgrading the electrostatic processes in existing ESPs. A concise survey of the electrostatic methods for increasing the removal efficiency in the PM2.5 particle size range is given by Jaworek et al. (2017). The literature given in this survey shows that the performances of cyclones, bag filters and granular-bed filters, when assisted with electrostatic processes, have improved in terms of the removal efficiency of PM2.5 particles. Also, some improvement has been achieved through the modification of electric power supply forms (DC, AC and pulsed voltages), the electrode design and arrangement in ESPs. Unfortunately, these removal efficiency improvements are unsatisfactory. The main reason for that lies in the weak charging of small particles, which, when weakly charged (or completely uncharged) cannot be electrostatically collected and are blown out of the ESP into the atmosphere. Apart from that, poor removal efficiency of PM2.5 particles due to their reduced susceptibility to the electrostatic force can be aggravated by reentrainment of the small particles, already deposited on the collecting electrodes, into the flue gas flowing towards the ESP outlet. The re-entrainment of already deposited particles is caused by the relatively strong electric (ionic) wind flowing from the discharge electrodes towards the collecting ones, and by the so-called back corona discharge that pulverises the particle layer formed on the collecting electrodes (Chang and Bai, 1999). The particle reentrainment into flue gas is very typical for the “classical” onestage process ESPs, which has been mostly used. In such onestage process precipitators, sometimes called Cottrel-type precipitators, the processes of the particle charging and particle collection due to the electrostatic precipitation occur in a single device, which is vulnerable to the back corona. The ESPs which are much less back corona-vulnerable are the so-called two-stage process precipitators, in which the processes of the air ionisation and particle charging and the collection of particles are separated. These two-stage processing is carried out in an air ionisation and particle charging section (briefly called a charging section) and in a collecting section for precipitating the charged particles, respectively. Both sections are placed separately in the ESP (Fig. 1). The need for the separate charging and collecting sections arises also from the difference in optimal conditions for the both processes. The air ionising and particle charging take place very rapidly, as compared to their separation from the polluted air stream. The saturation of particle charging can be achieved in 0.01 s or less in most industrial applications. On the other hand, long residence times are needed for the separation and subsequent collection of the particles from the polluted air stream (from 1 to 10 s for the industrial one-stage ESP unit). Not only that, the charging process prefers a non-uniform electric field, whereas a uniformly high electric field is required for the efficient separation of the particles from the air stream. Thus, such vastly different optimal conditions cannot be met in the one-stage ESPs. Therefore, separating the air ionising and particle charging from the particle

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collecting offers more efficient use of the electric energy as well as provides the opportunity to employ different electric energy forms (DC, AC and pulsed voltages) in both sections of two-stage ESPs. Moreover, the two-stage ESPs enable easy and diverse incorporation of other elements, which can improve the particle collection, such as particle agglomeration processing and gas stream manipulation. The two-stage ESP concept was developed in early 1910s €ller, 1920; Schmidt, 1920). The development of two-stage ESP (Mo systems until 1970 can be traced following papers (Penney, 1937, 1938, 1952, 1959, 1962, 1975; White, 1957, 1963; Lloyd, 1988; Parker, 2007). Survey of research on the development of two-stage ESPs after 1960 is given in (Jaworek et al., 2017, 2018). Despite the considerable progress in the development of two-stage ESPs, as reported in the literature above, the two-stage ESPs are still inadequate in applications where very high loading and/or high particulate content are involved. Originally, the two-stage ESPs were considered appropriate for removing low-concentration fine dust. The foreseen fields of application were removal of industrial dusts, which constitute a hazard to health of employees, room air cleaning for those suffering from allergies such as hay fever, neurodermitis or asthma, air cleaning to protect delicate apparatus or processes, and air cleaning in homes, offices and stores in soft-coal burning cities to reduce cleaning of walls, draperies, merchandise, etc. (Penney, 1937). Although the two-stage ESP designs have been modified to make them suitable for industrial applications (Jaworek et al., 2017, 2018; €ller, 1920; Schmidt, 1920; Penney, 1937, 1938, 1952, 1959, 1962, Mo 1975; White, 1957, 1963; Lloyd, 1988; Parker, 2007), they still are regarded as the most suitable for small-scale ESPs, for example used for indoor air cleaning, removal of nanoparticles from diesel engine exhausts, cleaning the air in road tunnels, and providing the air conditions for clean production in the industry. As already mentioned above, a two-stage ESP comprises a gas ionisation and particle charging section, a collecting section for precipitating the charged particles, and a means for causing the polluted air to pass through both stages (Fig. 1). Various forms of the corona discharges (DC, AC, pulsed) have been most often used for the air ionisation. The particle collector has been usually supplied with a reduced DC voltage, incapable of generating any electric discharge in the collector, but high enough to efficiently collect the charged particles. Usually the dust particle-laden air flow through both sections has been forced by a fan. However, the gas flow of a velocity of a few m/s can also be produced by the electric wind generated by the corona discharge (e.g. see recent publications related to the so-called self-pumped ESPs: (Katatani and Mizuno, 2010; Podlinski et al., 2013; Mizeraczyk et al., 2013). In this paper, we propose using the surface dielectric barrier discharge (SDBD) (Gibalov and Pitsch, 2000; Kogelschatz, 2010; Brandenburg, 2017) in the form of an EHD actuator in the twophase (air þ particles) environment of the two-stage ESP. The EHD SDBD actuator is powered with sinusoidal voltage (applying other forms of the alternating voltage is possible). It seems that in some ESP applications the SDBD can successfully replace the corona discharge, so far commonly used in the two-stage ESPs. The widely known features of SDBD that predestines it for the use in two-stage ESPs are: the generation of bipolarly charged ions in air and the generation of EHD flow causing unidirectional pumping of air (see e.g. reviews (Johnson and Go, 2017; Corke and Post, 2005; Moreau, 2007; Corke et al., 2007; Touchard, 2008; Corke et al., 2010; Wang et al., 2013; Benard and Moreau, 2014)). In a two-phase fluid (air þ particles), the SDBD would allow employing the bipolar air ions, generated by this discharge, for bipolar charging the particle suspended in the air. This would promote the charged particle agglomeration, which could result eventually in more efficient

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Fig. 1. Scheme of the two-stage ESP with the particle charging section and the particle collecting section. In the particle charging section a wire-to-plate corona discharge (DC, AC or pulsed) arrangement has mostly been used. The collecting electrodes are supplied with a DC high voltage.

particle precipitation. The unidirectional EHD flow induced by the SDBD can either enhance the primary flow of the treated two-phase fluid or act as a sole flow actuator (mostly in small-scale ESPs). It is worth noting that another type of the dielectric barrier discharge (DBD), the so-called volume DBD (VDBD) (Gibalov and Pitsch, 2000; Kogelschatz, 2010; Brandenburg, 2017), having the discharge characteristics and morphology different from those of the SDBD, has been previously employed in several electrode arrangements for the collection of particles suspended in air (Kuroda et al., 2003; Dramane et al., 2009; Gouri et al., 2011, 2013; Zouzou and Moreau, 2011; Zouzou et al., 2016). The VDBDs have also been tested as charging tools (originally called the prechargers) in two-stage type ESPs (Kawada et al., 1999, 2002; Kubo et al., 1999; Byeon et al., 2006), which may be classified as VDBD type two-stage ESPs. In all these cases there has been solely a replacement of the corona discharge as a charging source. Since the VDBD had to be directed perpendicularly to the particle-laden air flow, the VDBD could not play the role of a fan, capable of pushing the particleladen air towards the collecting section of two-stage ESP. This is a disadvantage of using the VDBD instead of the corona discharge and the SDBD, both of can be used for pushing the particle-laden air towards the collecting section in the two-stage ESP. The experimental research carried out in this work included: measurements of the SDBD discharge characteristics, PTV (Particle Tracking Velocimetry (Westerweel, 2011)) detecting indirectly the production of bipolarly charged particles by the SDBD and then monitoring their trajectories in the collecting section of the SDBDdriven ESP, and qualitative and quantitative studies of the particle removal efficiency in the SDBD-driven ESP. The results of PTV monitoring of the particle trajectories visualised the operation of the collecting section. In the presented investigations the usefulness of SDBD for efficient particle removal from a particle-laden air in a closed volume have been tested. In the next step, we intend to study the performance of the SDBD in flow system, i.e. for the removal of particles from a particle-laden air. 2. Concept of an SDBD-driven two-stage ESP In this work, a two-stage ESP system was investigated (Fig. 2), the concept of which is based on the use of the SDBD as a discharge source instead of the corona discharge generator, which has commonly been used in the conventional two-stage ESPs (Fig. 1). The SDBD actuator, forming the first section of the ESP, serves two functions in this SDBD-driven ESP system: a) it generates gaseous ions in the polluted air, which then charge particles suspended in the air (an ioniser function), and b) it forces the flow of polluted air towards the collecting electrodes (a function of an EHD flow

generator). The electrostatic collection of the particles takes place in the second section of the SDBD-driven ESP, which resembles the collecting sections of the conventional two-stage ESPs. 2.1. SDBD actuator The SDBD has been demonstrated to be capable of generating bipolar ions in air and producing unidirectional EHD pumping of air (Gibalov and Pitsch, 2000; Kuroda et al., 2003; Corke and Post, 2005; Moreau, 2007; Touchard, 2008; Corke et al., 2007, 2010; Kogelschatz, 2010; Wang et al., 2013; Benard and Moreau, 2014; Johnson and Go, 2017; Brandenburg, 2017). Both these features make the SDBD useful as an air ioniser and air flow actuator. This work is an attempt to test simultaneously both features of SDBD in a two-phase fluid (air þ particles) in a closed-volume two-stage ESP. Over the two past decades, various configurations of the SDBD plasma actuators have been developed (Gibalov and Pitsch, 2000; Kuroda et al., 2003; Corke and Post, 2005; Moreau, 2007; Corke et al., 2007, 2010; Touchard, 2008; Kogelschatz, 2010; Wang et al., 2013; Benard and Moreau, 2014; Johnson and Go, 2017; Brandenburg, 2017). The basic configuration is the so-called “classic” SDBD plasma actuator (Fig. 3). The classic SDBD plasma actuator is usually built from two electrodes and a dielectric plate inserted between them. The dielectric plate, of a high dielectric strength (e.g. glass, ceramics, Kapton), forms an electrical barrier between the two electrodes. The thickness of the dielectric plate usually ranges from tenths of a millimeter to several millimetres. The electrodes in the SDBD actuator are usually made of thin metal tape and are placed asymmetrically on both sides of the dielectric plate. The first electrode, called a high voltage (HV) or discharge electrode, is placed on the active side (the upper side in Fig. 3) of the dielectric plate and is connected to an AC voltage source. The second electrode is placed on the opposite side of the dielectric plate and is grounded. The grounded electrode is usually electrically insulated to avoid any discharge on the non-active side of the SDBD actuator. Various forms of the AC high voltage are applied. Mostly an alternating sinusoidal voltage is used. The frequency of AC high voltage applied to the discharge electrode is usually not higher than a dozen kilohertz. The peak-to-peak amplitude of the AC high voltage ranges from several kilovolts up to tens of kilovolts. When a high voltage is applied to the discharge electrode, the SDBD is generated and the low temperature plasma with bipolar ions develops on the active surface of the dielectric plate. As shown in Figs. 3 and 4, the SDBD plasma generates an EHD air flow of a velocity reaching about 5 m/s above the dielectric barrier surface (higher velocities can be obtained, if other SDBD actuator configurations are used, up to 10 m/s in (Berendt et al., 2011b)). The


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Fig. 2. Scheme of the two-stage ESP in which the SDBD is used. The SDBD performs the functions of an ioniser and an EHD flow generator in the first section (the charging section) of the ESP. The second section is a conventional collecting section. The charging section is energised with AC high voltage. The collecting electrodes are supplied with a DC high voltage.

velocity range of air flow up to several m/s offered by the SDBD can be attractive for the two-stage ESPs. In the two-stage SDBD-driven ESP shown in Fig. 2, the particle suspended in the air flowing (pushed by an external fan and/or by the internally induced EHD flow) above the SDBD actuator surface become bipolarly charged by the bipolar air ions produced in the SDBD. Then the bipolarly charged particles enter the second section, which plays the role of an electrostatic collector. 2.2. Electrostatic collecting section

Fig. 3. The classic SDBD actuator (without electrode shift) and the time-averaged flow velocity vector field of airflow generated by it over the actuator surface. The y-axis shows a distance above the actuator surface. The HV electrode was saw-shaped. The applied sinusoidal voltage was 32 kVpp and the frequency - 1.5 kHz. The experiment was carried out in an open-ends flow tunnel having L: W: H ¼ 1000 mm: 100 mm: 200 mm (Berendt et al., 2011a).

The second section of the SDBD-driven two-stage ESP (the electrostatic collecting section) consists of two plate collecting electrodes arranged in parallel to each other (Fig. 2). Usually high DC voltage (either positive or negative) is applied to one of these electrodes. The second of the electrodes is grounded. The applied voltage amplitude is set sufficiently low to not initiate any electric discharge between the plate electrodes. The bipolarly charged particles, coming from the charging section, pass through the collecting section where they are subjected to the electric force existing in it. As a result, the bipolarly charged particles separate, forming two unipolarly charged particle groups, which migrate towards the oppositely charged collecting electrodes, where they eventually deposit. The bipolarly charged particles can agglomerate on their ways from the SDBD to the collecting section and in it, whereby the particle removal is commonly expected to be more efficient. 3. Experimental procedure and setup

Fig. 4. EHD flow velocity profiles for various applied voltages measured in the classic SDBD actuator (without electrode shift) for sawlike HV electrode, shown in Fig. 3. The profiles were determined 12 mm downstream the active edge of HV electrode. The experiment was carried out in an open-ends flow tunnel having dimensions L: W: H ¼ 1000 mm: 100 mm: 200 mm (Berendt et al., 2011a).

The following experiments were carried out in this work: measurements of the SDBD discharge characteristics (voltage and discharge current waveforms), detecting the bipolarly charged particles and monitoring their trajectories in the collecting section of the SDBD-driven ESP (using Particle Tracking Velocimetry method), and qualitative and quantitative studies of the particle removal efficiency in the SDBD-driven ESP. The closed two-stage ESP chamber used in these investigations was made of acrylic glass. Its dimensions were: L: W: H ¼ 700 mm: 120 mm: 120 mm. The charging section and the collecting section were placed inside the closed chamber as shown in (Fig. 5). The charging section of the presented SDBD-driven two-stage ESP was basically a kind of the classic SDBD actuator (Fig. 6). It had two smooth flat electrodes (the discharge electrode to which a sinusoidal high voltage HVAC was supplied, and the grounded electrode placed asymmetrically on the opposite side of a glass plate, which played a role of a dielectric barrier in the SDBD system). Both electrodes were made of a copper foil having a thickness of 50 mm.

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Fig. 5. Scheme of the measuring system for the PTV monitoring of the particle trajectories in the collecting section. The thick arrows show the direction of the EHD flow. The scheme does not keep the dimension proportions.

Fig. 6. Scheme of the SDBD actuator (the scheme does not keep the dimension proportions). The width (the length of electrode side perpendicular to the EHD flow arrow) of both electrodes was 100 mm.

Their lengths are given in Fig. 6. The length and width of the glass plate were 250 mm and 100 mm, respectively. The glass plate thickness was 1 mm. The position of the SDBD in the ESP chamber during the measurements is shown in Fig. 7. The particle collecting section of the presented SDBD-driven two-stage consisted of two stainless-steel plates with a thickness of 0.5 mm, placed parallel to each other (Fig. 7). The length and width of the plates were 200 mm and 100 mm, respectively. The distance between the plates was 60 mm. The grounded electrode of the collecting section was set on an extension of the SDBD actuator glass plate, at a distance of 15 mm apart. The high voltage electrode (connected to a HVDC supply) were shifted 15 mm in respect to the grounded electrode, as shown in Fig. 7, to avoid an electric breakdown to the SDBD on the dielectric barrier plate. The collecting section was not equipped with any cleaning system of the collecting electrodes. When needed, the electrodes were cleaned of the deposited particles using a cleaning cloth wetted with alcohol. The high voltage for energising the SDBD was generated as follows. A sinusoidal signal with a frequency of f ¼ 1 kHz from a function generator (Tektronix AFG 3052C) was amplified by a highvoltage amplifier (TREK, model 40/15) and supplied to the SDBD discharge electrode. As a result, the sinusoidal voltage of a peak-topeak amplitude up to 20 kV could be obtained. The voltage between the discharge electrode and the grounded electrode of the SDBD actuator was measured using a high-voltage probe (Tektronix,

P6015A) and recorded by a digital oscilloscope (Keysight, DSO 9064A, bandwidth 600 MHz, sampling rate 10 GS s1). Using a voltage probe (Agilent, N2873A), the discharge current waveforms of the SDBD was recorded by a digital oscilloscope, as a voltage drop across a 1 kU resistor, which was connected the grounded electrode and the electrical ground (the electrical elements and apparatus are not shown in Figs. 5e7). The constant high voltage potential of an amplitude up to 10 kV was delivered to the high voltage electrode of the collecting section from a DC power supply. The detecting and monitoring of the particle trajectories in the collecting section of the SDBD-driven ESP aimed at visualization of the collecting section operation were performed with the use of Particle Tracking Velocimetry (PTV) method, often called low particle number density Particle Image Velocity (PIV) (Westerweel, 2011). In contrast to PIV, in which the mean displacement of a small group of particles (present in the so called interrogative area (Westerweel, 2011)) is determined, PTV tracks the trajectories of individual particles in a moving fluid. PTV measurements are easier to perform and more reliable when the fluid contains larger particles of not high particle number volume density. Since detection, identification and position determination of an individual particle in the fluid is the essence of PTV, it seems to be particularly suitable for monitoring the trajectories of individual bipolarly charged particles in the collecting section of the SDBD-driven ESP. PTV method enables tracking the movement of an individual

Fig. 7. Scheme of positioning the SDBD actuator and the collecting section in the ESP chamber. The scheme does not keep the vertical dimension proportions.


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particle in a selected cross section of a flow. The selected flow cross section, called the observation plane is set in the flow by introducing into it a pulsed laser beam in the form of a laser sheet. The PTV method is based on observation of the displacement of the individual particle in the interrogation areas (the subareas of the observation plane (Westerweel, 2011)) during a given time interval defined by the repetition frequency of the laser beam pulses. The particle displacement in the interrogative area is determined by imaging the pulsed laser sheet light scattered by the particle moving in this area. Each laser beam pulse forms an image showing the instantaneous position of the particles in the interrogation area. From two consecutive images recorded by a CCD camera the particle displacement in the time interval between two laser beam pulses can be found using a computer algorithm for selecting an individual particle in every interrogation areas of the observation plane. Then each of these selected individual particles is tracked through the consecutive images of the observation area. As a result, a map of the individual particle trajectories in the observation area over a given time interval can be performed. For the PTV measurement a measuring system tested in a series of our previous PIV measurements in ESP environments (Mizeraczyk et al., 2001, 2013, 2016) was used. In brief, the system consisted of a double pulsed laser unit (Nd:YAG Litron LDY304, wavelength l ¼ 527 nm, pulse duration t ¼ 150 ns, pulse repetition rate f ¼ 300 Hz, pulse energy Ei ¼ 30 mJ), a laser beam guiding and focusing optics (including a cylindrical telescope), a high speed CMOS camera (Speedsense M34) and a PC with the Dantec DynamicStudio analysis software for PTV - Fig. 5. The observation plane, formed by the laser beam sheet passed along the longer axis of the collecting section, perpendicularly to the collecting electrodes. Alumina Al2O3 powder consisting of relatively large particles suspended in air were used in the PTV investigations. The average diameter and concentration of the Al2O3 particles were measured using an optical aerosol spectrometer GRIMM 1.109. The average diameter of Al2O3 particles, having a mass density of 3.95 g/cm3, was about 10 mm. The initial concentration of Al2O3 particles was about 1000 particles/cm3. Cigarette smoke was used for creating a two-phase fluid (air þ particles) for the investigations of fine particle removal process in the SDBD-driven ESP. The average diameter of the suspended particles was about 0.3 mm. Their initial concentration was about 200$103 particles/cm3. At such a particle concentration the two-phase fluid was fairly visible to the naked eyes. 4. Results 4.1. Voltage and discharge current waveforms Fig. 8 presents the typical voltage and discharge current waveforms of the SDBD actuator (shown in Fig. 6) recorded by digital oscilloscope during the hour-long experiment. The waveforms presented in Fig. 8 are similar to those measured earlier by other groups (Gibalov and Pitsch, 2000; Kuroda et al., 2003; Corke and Post, 2005; Moreau, 2007; Corke et al., 2007, 2010; Touchard, 2008; Kogelschatz, 2010; Wang et al., 2013; Benard and Moreau, 2014; Johnson and Go, 2017; Brandenburg, 2017). The SDBD was energised by a sinusoidal voltage of a peak-to-peak voltage amplitude of 20 kV and a frequency of 1 kHz. The SDBD current waveform shown in Fig. 8 consists of three components. The first component is a capacitive current due to the capacitance of the SDBD electrode arrangement, the second component is a pulsed discharge current, and the third component is a virtual capacitive current (called a quasi-synchronous current), which is in phase with the pulsed discharge current. The capacitive current between

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Fig. 8. Voltage and discharge current waveforms of the SDBD actuator (sinusoidal peak-to-peak voltage Vpp ¼ 20 kV, frequency f ¼ 1 kHz). 1 - the capacitive current þ the virtual capacitive current, 2 - the positive streamers, 3 - the negative glow microdischarges.

the SDBD electrode electrodes is shifted in phase by p/2 in respect to the sine waveform. The virtual capacitive current is a kind of capacitive current between the SDBD electrodes and a virtual electrode formed by the electric charges left by the current pulses on the dielectric surface. The pulsed discharge current consists of two distinct groups of current pulses. The first group of current pulses, corresponding to a filamentary microdischarges on the dielectric barrier (called the positive streamers), occur during the positive voltage-going cycles of sine voltage wave. The second group of current pulses, of clearly lower amplitude than that of the positive streamers, occur during the negative voltage-going cycles of sine voltage wave. These current pulses correspond to the negative glow regime microdischarges of the SDBD. 4.2. PTV (Particle Tracking Velocimetry) for detecting the production of bipolarly charged particles by the SDBD and monitoring their trajectories in the collecting section. Visualization of the collecting section operation On the basis of the operation principle of two-stage ESPs €ller, 1920; Schmidt, 1920; Penney, 1937, 1938, 1952, 1959, 1962, (Mo 1975; White, 1957, 1963; Lloyd, 1988; Parker, 2007) and the SDBD features (Gibalov and Pitsch, 2000; Kuroda et al., 2003; Corke and Post, 2005; Moreau, 2007; Corke et al., 2007, 2010; Touchard, 2008; Kogelschatz, 2010; Wang et al., 2013; Benard and Moreau, 2014; Johnson and Go, 2017; Brandenburg, 2017) it can be expected that the proposed SDBD-driven ESP would operate as follows. The particle suspended in the air are bipolarly charged by the SDBD and electrohydrodynamically pushed towards the collecting section. Passing through the collecting section the bipolarly charged particles are subjected to the electric force existing there. Due to the electric force they separate into two unipolarly particle groups, which migrate towards the oppositely charged collecting electrodes, where they eventually deposit. Generally, it is expected that the bipolarly charged particles can agglomerate on their ways from the SDBD to the collecting section and in it, whereby the particle removal can be more efficient. The investigations presented in this subsection (4.2) were aimed at confirming some of the above expectations on the operation of the proposed SDBD-driven ESP. For this purpose the PTV method

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was used. It is capable of indirect detecting the production of bipolarly charged particles by the SDBD, their presence and separation into two unipolarly charged particle groups in the collecting section, and then onward separate migration of the two unipolarly charged particle groups in the collecting section. Our preliminary PTV tests detected the presence and movement of the bipolarly charged particles in the collecting section of the SDBD-driven ESP, however, due to a relatively high difference between the convection velocity of all particles (uncharged and charged, caused by the EHD flow generated by the SDBD, about 1 m/s) and the migration velocity of the bipolarly charged particles (caused by the electric force, about 0.1 m/s for a DC high voltage of 5 kV between the collecting plates) a clear visualization of the charged particle movement in the collecting section was hindered. Therefore, to eliminate the convection movement of the particle, the particle trajectories in the collecting section were measured as follows. First, the ESP chamber was evenly filled with the air þ particles fluid. Then, the SDBD actuator was activated for about 5 s (Vpp ¼ 16 kV, f ¼ 1 kHz) to charge the particles and introduce them into the collecting section, which was not connected to the DC high voltage supply. After deactivating the SDBD actuator, the EHD convection forces practically vanished, and the PTV images could be recorded without and with a DC high voltage (þ5 kV, the voltage rising time was 5 ms) applied to the collecting section. The time of applying the DC high voltage to the collecting section was taken as the reference time t ¼ 0. Due to a relatively long life-time of the charged particles the PTV observation of the collecting section operation could last several seconds. Since the PTV investigations have been conducted in the still (air þ particles) fluid conditions, the particle agglomeration in the collecting section has been expected to be weak. Therefore, any study of the particle agglomeration has not been attempted in this work. Due to to-some-extent stochastic character of the particle movement in the collecting section, although governed by the electric field, the instantaneous PTV images and maps of the trajectories of the particles shown below have been selected as typical from a series of repeated experiments (usually 3e5 repetitions). The instantaneous PTV images shown in Fig. 9 illustrate the process of particle removal in the collecting section. It is seen from the images that the vast majority of the particles introduced to the collecting section disappeared within a few seconds, supposedly deposited on the collecting electrodes. This supposition justifies the following set of PTV maps (Fig. 10). PTV maps of the trajectories of the particle moving between the collecting electrodes at various times with respect to the time t ¼ 0 of applying the DC high voltage to the collecting section are shown in Fig. 10. Map A shows the particle trajectories recorded over a time period between t ¼ - 1 s and t ¼ - 0.5 s before applying the DC high voltage. It can be seen that although the particles have been already introduced into the collecting section by the EHD flow several seconds ago, still they possessed a small horizontal component of the velocity (up to 0.02 m/s). Also it can be seen that the relatively heavy Al2O3 particles (of a density of about 103 higher than that of air) exhibited a tendency to descent due to the gravity forces. At the moment (t ¼ 0) of applying the DC high voltage to the collecting electrodes (Fig. 10 B), the horizontal movement of the particles has been disturbed. The particles, which have previously been electrically charged by the SDBD discharge began to acquire the vertical velocity component and to move towards the collecting electrodes due to the electric field created in the collecting section. As it is seen more clearly in Fig. 10 C (the particle trajectory recorded within a time period of 0.5 se0.7 s), the particles have separated. One group of the charged particles have been moving

towards the positively charged electrode, while another group - to the negatively charged grounded electrode. It means that the particles of the former group were negatively charged, while the particle belonging to the latter group were positively charged. We estimate that about 15% more charged particles moved towards the negatively charged grounded electrode. This is consistent with the fact that the net electric charge generated by SDBD is positive (Borra et al., 2009). After a time of t ¼ 6 s (Fig. 10 D) the majority of the charged particles have disappeared from the collecting section volume, most likely they have deposited on the collecting electrodes (the deposits could be seen with the naked eye). The trajectories present still in Fig. 10 D correspond supposedly to either the weakly charged (and therefore slow) or uncharged particles suspended in the air. The migration velocity (towards the collecting electrode) of electrically charged particle could reach 0.15 m/s (at a DC high voltage of þ5 kV). It could be higher, if the applied DC voltage were higher. However, increasing the DC voltage above þ10 kV resulted in a discharge between the collecting electrodes and the SDBD actuator. This was caused by the short spacing between both elements, unfortunately not optimised in this experiment, which provided conditions favoured for the development of electric breakdown. We believe that optimizing the arrangement: SDBD actuator - collecting section would result in higher migration velocities of the charged particles and correspondingly higher collecting efficiency. This would enable PTV investigations of charged particle movement in the collecting section also with the operating SDBD actuator, which in the present investigations was switched off. So far, the PTV method has proved to be useful for visualizing the behaviour of bipolarly charged particle in the collecting section under static conditions, i.e. without externally forced flow of the (air þ particles) fluid. Summing up, the above PTV investigations confirmed our expectations that: - the bipolarly charge particles are produced in the SDBD, - they separate into two groups of unipolarly charged particles in the collecting section, - the unipolarly charged particles migrate to the collecting electrodes, on which they deposit.

4.3. Qualitative and quantitative studies of the particle removal efficiency of SDBD-driven ESP Our qualitative studies of the particle removal efficiency in the SDBD-driven two stage ESP were based on the analysis of images produced by the laser beam light scattered by the two-phase fluid (air þ particles) present in the ESP chamber. Similarly as in PTV measurements, a laser beam in the form of the laser sheet was introduced into the ESP chamber and set along its longer axis, perpendicularly to the collecting plates. The observation plane thus created illuminated the particles present in it. The light scattered by the particles in the observation plane were recorded by the camera of our PTV system (Mizeraczyk et al., 2001, 2013, 2016). The recorded images delivered information on the presence and concentration of the particles suspended in the observation plane. The bright images or bright areas in the images denoted high concentration of the particles (due to high intensity of the scattered light recorded by the camera), while dark images and areas meant lack or low concentration of the particles. The very dark images indicated that the fluid in the ESP chamber was void of particles, i.e. we dealt with a gaseous single-phase fluid (air). A series of images captured during the operation of SDBD-driven two-stage ESP presented temporal changes of the suspended particle concentration


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Fig. 9. PTV images: Illustration of the particle collection process in the collecting section. The upper image: Instantaneous number and position of the particles in the collecting section at a time of 0.7 s after applying the DC high voltage to the collecting section. The lower image: Instantaneous number and position of the particles in the collecting section at a time of 6 s after applying the DC high voltage. The particles are presented as dark dots (a negative of the original image).

in the ESP chamber, caused by the electrostatic precipitation. The temporal change in brightness (from bright to dark) of the recorded images is a qualitative indication of the ongoing process of particle removal. Four cases, denoted in Fig. 11 as A, B, C, and D were examined. Each case was repeated 3 times showing reasonable repeatability. Typical results are shown in Fig. 11. In the first case (A), the removal of the particles from the two-phase fluid: air þ particles in SDBDdriven two stage ESP was recorded (SDBD: 20 kV means that the peak-to peak Vpp voltage applied to the SDBD actuator was 20 kV, frequency f ¼ 1 kHz; the DC voltage applied to the collecting section (CS) was þ5 kV). In case A, as well as in the others (B, C, and D) the initial (at t ¼ 0) concentration of particles suspended in air was 200$103 cm3 (measured with the laser aerosol spectrometer GRIMM model 1.109). For all cases A, B, C and D, the brightness of images captured at t ¼ 0 is a visual benchmark for assessing progress in the ongoing particle removal. As it is seen in the images presented in Fig. 11 A, the brightness of images captured in a time interval between t ¼ 0 and t ¼ 120 s is continuously reducing with elapsing time. 120 s after the experiment beginning the image is dark, and the darkness of the following images (at times t ¼ 150 s and t ¼ 180 s) remains constant. The plausible interpretation of the worsening brightness of images shown in Fig. 11 A is that the suspended particles have continuously been removed electrostatically from the two-phase fluid (air þ particles) filling the ESP chamber, whereby the scattered laser beam light has weakened (following the decreased concentration of the particles in the ESP chamber). Correspondingly the successive images have begun to darken. After about 120 s the vast majority of particles have been removed from the two-phase fluid and deposited on the collecting electrodes. Practically the two-phase fluid (air þ particles) has been transferred into the single-phase air.

In the second case (B), the experiment (A) was repeated, the only change was that the DC voltage applied to the collecting section (CS) was increased to þ 10 kV. This, as could be expected, speeded up the particle collection in the collecting section due to the double increase of the electric field in it. The increased rate of particle removal is reflected in the images shown in Fig. 11 B. As it can be easily found, the image captured at t ¼ 60 s in the case B is as dark as that of the case A captured at t ¼ 120 s. This would suggest that doubling the electric field in the collecting section doubles the particle removal rate. In the case C, the SDBD actuator operated as in two previous cases, while the collecting section was switched off (CD: 0 kV). As it could be expected, the captured images did not show any signs of particle removal, at least until 90 s after the experiment beginning (Fig. 11 C). Case D (the SDBD actuator switched off, the DC voltage applied to the collecting section doubled (CS: 10 kV); Fig. 11 D) showed that the collecting section had not any capability of charging the particles, even at as high voltage as 10 kV. The images presented in Fig. 11 A and B are the visual evidence of the particle removal in the SDBD-driven two-stage ESP. Our quantitative studies of the particle removal efficiency in the SDBD-driven two stage ESP were based on the measurements of particle concentration as a function of time during the ESP operation. The measurements were carried out under similar conditions as those of cases A (SDBD: 20 kV, CS: 5 kV) and B (SDBD: 20 kV, CS: 10 kV). In both cases the initial concentration of the particles suspended in air was 200$103 cm3. The dependences of particle number (equal to the product of the air volume in the closed ESP chamber and the particle concentration) in the SDBD-driven two stage ESP on removal time are shown for both cases in Fig. 12 (A and B). The plot: particle number versus

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Fig. 10. PTV maps of the trajectories of the particles moving between the collecting electrodes at various times with respect to the time t ¼ 0 of applying the DC high voltage to the collecting section.

time can be divided into two time intervals. In the first interval, the particle removal is fast and almost a linear function of time. In the second interval, the particle removal is noticeably slower. In both cases (A and B) the second, slower removal interval starts when the particle number in the chamber decreases below about 0.5$109 particles, which corresponds to a concentration of 50$103 particles cm3. In the first interval, the particle number removal rates (in particles s1) are about 23$106 and 45$106, respectively for case A and B. The particle number removal rates decrease in the second interval to about 3.6$106 particles s1 and 7.9$106 particles s1, respectively for case A and B. The faster particle number removal rate for case B is justified by a higher DC high voltage applied to the collecting section. It is worth mentioning, that the two different intervals of particle number removal rate on the plot: particle number as a function of removal time was earlier found by us in a small single needle-to-plate negative DC corona discharge ESP (of its ESP chamber volume comparable to that of the presented SDBD ESP

chamber) (Berendt et al., 2017). The most plausible cause of two distinct removal time intervals might be the existence of two groups of charged particles: a group of heavily charged particles (a fraction of larger particles charged in the field charging mechanisms) and a group consisting of weakly charged particles (usually a fraction of smaller particles charged in the diffusion charging mechanism) and of neutral particles that have stochastically avoided charging (they can be charged afterwards since in the closed ESP the particle charging process lasts until all particles have been removed). Usually the electrostatic removal of heavily charged particles is faster than those which are less charged, and as a consequence the two time intervals of different particle removal rates have been observed. It is important to notice that the particle number removal rates (in particles s1) in the presented SDBD-driven two-stage ESP unit and the single needle-to-plate negative DC corona one-stage ESP unit presented in (Berendt et al., 2017), both representing smalltype experimental ESPs, are very similar (about 50$106 particles s1). This suggests that these two different basic single discharge units, which can be employed to form larger ESPs (either driven by the SDBD units or by the needle-to-plate negative DC corona units), exhibit similar particle removal efficiencies. In other words, if both basic single discharge units are employed for removing the particles from the same air volume, the removal would take similar amount of time. This shows the potential of the SDBD for particle removal. The above shows that the particle number removal rate appears to be one important parameter useful for estimating and comparing the abilities of various basic single discharge units for application in the particle precipitation. When this criterion is used, the SDBD and the needle-to-plate DC negative corona basic units are similar to one another in terms the particle removal capability. So far, the needle-to-plate DC negative corona basic units have been successfully implemented in the small- and large-scale ESPs (to augment the removal effect of a single negative corona unit, some of 50 km of such units (in the discharge electrode form of ribbon peaks and square teeth, serrated strips, formed shapes with spikes, protrusions and barbs) can be found in a large ESP installation (Parker, 2007). Similarly, if a practical SDBD-driven ESP is considered, it must be an ESP system consisted also of a large number of the SDBD basic units. The qualitative and quantitative results presented above are in good agreement. The image captured at t ¼ 60 s in case B (Fig. 11 B) is as dark as that of the case A, captured at t ¼ 120 s (Fig. 12 A). It meant that the particle concentrations at these times should have been similar. Fig. 12 shows that for both cases (A and B) the measured particle numbers (and concentrations) were really very close to each other at a time of t ¼ 120 s and t ¼ 60 s, respectively for case A and B. 5. Summary and conclusions The concept and operation of the so-called SDBD-driven twostage ESP were presented in this paper. As a novelty, the SDBD in the form of an EHD actuator was employed in the proposed twostage ESP, instead of the commonly used corona discharge. The SDBD has two features which make it predestined to be used in the two-stage ESPs. These are: the generation of bipolarly (positively and negatively) charged ions and particles in the working (air þ particle) fluid, and the generation of a unidirectional EHD flow in the working fluid. The suitability of SDBD for the two-stage ESP systems has been experimentally tested in the closed SDBDdriven two-stage ESP. The experiment comprised measurements of the SDBD discharge characteristics, PTV detecting the bipolarly charged particles produced by the SDBD and then monitoring the


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Fig. 11. Images showing temporal changes of the suspended particle concentration in the SDBD-driven two-stage ESP. Abbreviations: t - the time elapsing after the experiment beginning; e.g., SDBD: 20 kV e the peak-to peak Vpp voltage applied to the SDBD actuator; e.g., CS: 10 kV e the DC voltage applied to the collecting section (CS). The proportions of the height and width of the electrostatic precipitator were not kept in the images.

Fig. 12. Number of particles suspended in air filling the SDBD-driven two-stage ESP as a function of removal time for two values of the DC high voltage applied to the colleting section (CS): A) 5 kV and B) 10 kV. SDBD actuator - Vpp ¼ 20 kV, frequency f ¼ 1 kHz. The presented results are average values of 3 measuring trial runs. The difference between the recorded values and their average value did not exceed ±10%.

trajectories of these particles in the collecting section of the SDBDdriven ESP, and qualitative and quantitative studies of the particle removal efficiency of the SDBD-driven ESP. The PTV measurements confirmed that the SDBD in the first section of the ESP produced bipolarly charged particles in the twophase fluid (air þ particles), which then were transported with the induced EHD flow to the collecting section, being the second section of the ESP. As the PTV measurements showed, in the collecting section the bipolarly charged particles separated in two groups of unipolarly charge particles and migrated in the electric field towards the relevant collecting electrodes, where they deposited.

Therefore, the suitability of the SDBD for the two-stage ESPs have been proved by the performed PTV measurements. The measurements carried out with the PTV proved its unique capability of visualization of the operation of the electrostatic collecting section by showing images of the trajectories of charged particles which are to be collected electrostatically. The performed studies of the particle removal efficiency of the SDBD-driven ESP showed that the SDBD-driven ESP has proved successful in collecting the particles suspended in air. The particle number removal rate in the SDBD-driven ESP is comparable with that of the small-type experimental single needle-to-plate negative DC corona single stage ESP (Berendt et al., 2017). Deeper and more accurate comparisons between the both ESP are prematured, because they were by no means optimised. More studies are needed to optimize the lab-scale SDBD-driven two-stage ESP. What we have already noticed is that the distance between the charging section and the collecting sections was too small. This small distance between both sections caused an electric discharge between both sections, when the DC high voltage was higher than 10 kV. Such a limitation of the DC high voltage, which could have been applied to the collecting section reduced the particle collection efficiency in this section. The particle collection efficiency could also be improved by reducing the distance between collecting plates in the collecting section by a factor of 3e4 (whereby the electric field can increase to 106 V/m (Jaworek et al., 2018)), without essential interference of the flow in the collecting section. This would allow shortening considerably the length of the SDBD-driven ESP unit. The results presented in subsection chapter 4.2 showed that the PTV method could be very helpful in the studies aimed at optimizing the collecting section. In the presented experiment we showed the usefulness of the SDBD for efficient precipitating particles from polluted air in a closed volume. After optimizing the design of lab-scale SDBDdriven ESP unit, we intend to study its performance in flow system, i.e. for the removal of particles from a particle-polluted air stream.

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Acknowledgment This work was supported by the National Science Centre (grant UMO-2013/09/B/ST8/02054). References Brandenburg, R., 2017. Dielectric barrier discharges: progress on plasma sources and on the understanding of regimes and single filaments. Plasma Sources Sci. Technol. 26 (5), 053001. Benard, N., Moreau, E., 2014. Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control. Exp. Fluid 55, 1846.
ski, J., Mizeraczyk, J., 2011. Comparison of airflow patterns proBerendt, A., Podlin duced by DBD actuators with smooth or saw-like discharge electrode. J. Phys. Conf. Ser. 301, 012018.
ski, J., Mizeraczyk, J., 2011. Elongated DBD with floating inBerendt, A., Podlin terelectrodes for actuators. Eur. Phys. J. Appl. Phys. 55 (1), 13804.
ski, J., 2017. Electrostatic particle precipitation in a Berendt, A., Mizeraczyk, J., Podlin two-phase fluid in a needle-to-plate negative DC corona discharge. Przeglad Elektrotechniczny 2, 224e227. Borra, J.P., Jidenko, N., Bourgeois, E., 2009. Atmospheric pressure plasmas for aerosols processes in materials and environment. Eur. Phys. J. Appl. Phys. 47 (2), 22804. Byeon, J.H., Hwang, J., Park, J.H., Yoon, K.Y., Ko, B.J., Kang, S.H., Ji, J.H., 2006. Collection of submicron particles by an electrostatic precipitator using a dielectric barrier discharge. J. Aerosol Sci. 37, 1618e1628. Chang, C.L., Bai, H., 1999. The experimental study on the performance of a single discharge wire-plate electrostatic precipitator with back corona. J. Aerosol Sci. 30, 325e340. Corke, T.C., Post, M.L., 2005. Overview of Plasma Flow Control: Concepts, Optimization and Applications, p. 563. AIAA Paper. Corke, T.C., Post, M.L., Orlov, D.M., 2007. SDBD plasma enhanced aerodynamics: concepts, optimization and applications. Prog. Aero. Sci. 43, 193e217. Corke, T.C., Enloe, C.L., Wilkinson, S.P., 2010. Dielectric barrier discharge plasma actuators for flow control. Annu. Rev. Fluid Mech. 42, 505e529. Di Natale, F., Carotenuto, C., 2015. Particulate matter in marine diesel engines exhausts: emissions and control strategies. Transport. Res. D. 40, 166e191. Dramane, B., Zouzou, N., Moreau, E., Touchard, G., 2009. Electrostatic precipitation of submicron particles using a DBD in axisymmetric and planar configurations. IEEE Trans. Dielectr. Electr. Insul. 16 (2), 343e351. Gibalov, V.I., Pitsch, G.J., 2000. The development of dielectric barrier discharges in gas gaps and on surfaces. J. Phys. D. 33, 2618e2636. Goodarzi, F., 2006. Morphology and chemistry of fine particles emitted from a Canadian coal-fired power plant. Fuel 85, 273e280. Gouri, R., Zouzou, N., Tilmatine, A., Moreau, E., Dascalescu, L., 2011. Collection efficiency of submicrometre particles using single and double DBD in a wire-tosquare tube ESP. J. Phys. D. 44 (49), 495201. Gouri, R., Zouzou, N., Tilmatine, A., Dascalescu, L., 2013. Enhancement of submicron particle electrostatic precipitation using dielectric barrier discharge in wire-tosquare tube configuration. J. Electrost. 71 (3), 240e245. Guan, B., Zhang, R., Lin, H., Huang, A., 2015. Review of the state-of-the-art of exhaust particulate filter technology in internal combustion engines. J. Environ. Manag. 154, 225e258. Jaworek, A., Marchewicz, A., Sobczyk, A.T., Krupa, A., Czech, T., 2017. Two-stage electrostatic precipitator with dual-corona particle precharger for PM2.5 particles removal. J. Clean. Prod. 164, 1645e1664. Jaworek, A., Marchewicz, A., Sobczyk, A.T., Krupa, A., Czech, T., 2018. Two-stage electrostatic precipitators for the reduction of PM2.5 particle emission. Prog. Energy Combust. Sci. 67, 206e233. Johnson, M.J., Go, D.B., 2017. Recent advances in electrohydrodynamic pumps operated by ionic winds: a review. Plasma Sources Sci. Technol. 26 (10), 103002. Katatani, A., Mizuno, A., 2010. Generation of ionic wind by using parallel located flat plates. J. Inst. Electrosat. Japan. 34 (4), 187e192. Kawada, Y., Kubo, T., Ehara, Y., Ito, T., Zukeran, A., Takahashi, T., Kawakami, H., Takamatsu, T., 1999. Development of high collection efficiency ESP by barrier discharge system. Conf. Rec. IEEE-IAS. 2, 1130e1135. Kawada, Y., Kaneko, T., Ito, T., Chang, J.S., 2002. Simultaneous removal of aerosol particles, NOx and SO2, from incense smokes by a DC electrostatic precipitator

with dielectric barrier discharge prechargers. J. Phys. D. 35, 1961e1966. Kogelschatz, U., 2010. Collective phenomena in volume and surface barrier discharges. J. Phys. Conf. Ser. 257, 012015. Koizumi, Y., Kawamura, M., Tochikubo, F., Watanabe, T., 2000. Estimation of the agglomeration coefficient of bipolar-charged aerosol particles. J. Electrost. 48, 93e101. Kubo, T., Kawada, Y., Zukeran, A., Ehara, Y., Ito, T., Takahashi, T., Kawakami, H., Takamatsu, T., 1999. Reduction of particles and NOx exhausted from diesel engine by barrier discharge type ESP. J. Aerosol Sci. 30 (1), S793eS794. Kuroda, Y., Kawada, Y., Takahashi, T., Ehara, Y., Ito, T., Zukeran, A., Kono, Y., Yasumoto, K., 2003. Effect of electrode shape on discharge current and performance with barrier discharge type electrostatic precipitator. J. Electrost. 57, 407e415. Lloyd, A.D., 1988. Electrostatic Precipitator Handbook. CRC Press, Boca Raton. Meng, X., Zhang, Y., Yang, K.Q., Yang, Y.K., Zhou, X.L., 2016. Potential harmful effects of PM2.5 on occurrence and progression of acute coronary syndrome: epidemiology, mechanisms, and prevention measures. Int. J. Environ. Res. Public Health 13 (8), E748.
ski, J., Ohkubo, T., Mizeraczyk, J., Kocik, M., Dekowski, J., Dors, M., Podlin Kanazawa, S., Kawasaki, T., 2001. Measurements of the velocity field of the flue gas flow in an electrostatic precipitator model using PIV method. J. Electrost. 51, 272e277.
ski, J., Niewulis, A., Berendt, A., 2013. Recent progress in Mizeraczyk, J., Podlin experimental studies of electro-hydrodynamic flow in electrostatic precipitators. J. Phys. Conf. Ser. 418 (1), 012068.
ski, J., 2016. Temporal and spatial evolution of EHD Mizeraczyk, J., Berendt, A., Podlin particle flow onset in air in a needle-to-plate negative DC corona discharge. J. Phys. D. 49, 205203. €ller, E., 1920. Art of Separating Suspended Particles from Gases. U.S. Pat. vol. 1 Mo 357 466. Moreau, E., 2007. Airflow control by non-thermal plasma actuators. J. Phys. D. 40, 605e636. Neeft, J.P.A., Makkee, M., Mouljin, J.A., 1996. Diesel particulate emission control. Fuel Process. Technol. 47, 1e69. Parker, K., 2007. Electrical Operation of Electrostatic Precipitators. IET, London. Penney, G.W., 1937. A new electrostatic precipitator. Electr. Eng. 56 (7), 869e871. Penney, G.W., 1938. Electrical Precipitator for Atmospheric Dust. U.S. Pat. vol. 2 129 783. Penney, G.W., 1952. Ionizing Unit for Electrostatic Filters. U.S. Pat. vol. 2 672 948. Penney, G.W., 1959. Electrostatic Precipitator. U.S. Pat. vol. 2 875 845. Penney, G.W., 1962. Two-stage Precipitator. U.S. Pat. 3 066 463. Penney, G.W., 1975. Adhesive behaviour of dust in electrostatic precipitation. J. Air Pollut. Control Assoc. 25 (2), 113e117. Podlinski, J., Niewulis, A., Berendt, A., Mizeraczyk, J., 2013. Pumping effect measured by PIV method in a multilayer spike electrode EHD device for air cleaning. IEEE Trans. Ind. Appl. 49 (6), 2402e2408. Radulescu, C., Iordache, S., Dunea, D., Sithi, C., Dulama, I.D., 2015. Risks assessment of heavy metals on public health associated with atmospheric exposure to PM2.5 in urban area. Rom. J. Phys. 60 (7), 1171e1182. Schmidt, W.A., 1920. Means for Separating Suspended Matter from Gases. U.S. Pat. vol. 1 343 285. Stamatellou, A.M., Stamatelos, A., 2017. Overview of diesel particulate filter systems sizing approaches. Appl. Therm. Eng. 121, 537e546. Touchard, G., 2008. Plasma actuators for aeronautics applications - state of art review. Int. J. Plasma Environ. Sci. Technol. 2, 1e25. Wang, J.J., Choi, K.S., Feng, L.H., Jukes, T.N., Whalley, R.D., 2013. Recent developments in DBD plasma flow control. Prog. Aero. Sci. 62, 52e78. Adrian, R.J., Westerweel, J., 2011. Particle Image Velocimetry. Cambridge University Press, Cambridge. White, H.J., 1957. Fifty years of electrostatic precipitation. J. Air Pollut. Control Assoc. 7 (3), 166e177. White, H.J., 1963. Industrial Electrostatic Precipitation. Addison-Wesley, Boston. Zhu, J., Zhang, X., Chen, W., Shi, Y., Yan, K., 2010. Electrostatic precipitation of fine particles with a bipolar pre-charger. J. Electrost. 68, 174e178. Zouzou, N., Moreau, E., 2011. Effect of a filamentary discharge on the particle trajectory in a plane-to-plane DBD precipitator. J. Phys. D. 44 (28), 285204. Zouzou, N., Aba’a Ndong, A.C., Braud, P., Moreau, E., 2016. Time-resolved measurements of electrohydrodynamic phenomena in an AC dielectric barrier discharge electrostatic precipitator. IEEE Trans. Dielectr. Electr. Insul. 23 (2), 651e657.