Noureddine Zouzou

Electrostatic precipitation of submicron particles using a DBD in axisymmetric and planar configurations

The aim of the present work has been to quantify the efficiency of Dielectric Barrier Discharges (DBDs) for the collection of submicron particles. The experiments were performed with incense smoke particles having a mean size of about 0.3 mum. An aerosol spectrometer was employed for characterizing the size distribution of these particles at the outlet of Wire-to-Cylinder (WC) and Plate-to-Plate (PP) DBD reactors. The collection efficiency was estimated for various applied voltages (6 - 26 kV, 1 - 2000 Hz), and airflow rates of 1.6 - 24 L/min. The discharge mode was diffuse, in the case of the axisymmetric configuration, and filamentary, in the case of the planar configuration. When flow rate increases, the discharge current and the electric power decrease in both cases. This effect is less pronounced with the planar configuration. Results obtained with the aerosol spectrometer show that the particle collection efficiency of both reactors is higher at high applied voltage and low flow rate; it decreases at high frequency because of particle oscillations, and at low frequency due to the intermittent nature of the discharge. The frequency range for which the collection efficiency is higher than 90% is wider in the case of WC reactor.

EHD Flow and Collection Efficiency of a DBD ESP in Wire-to-Plane and Plane-to-Plane Configurations

In this paper, particle velocity fields inside three electrostatic precipitators (ESPs) are investigated experimentally using particle image velocimetry (PIV). The reference case is a typical wire-to-plane ESP under negative and positive dc high voltages. The two other ESPs use an ac high voltage to generate a dielectric barrier discharge (DBD) in wire-to-plane and plane-to-plane configurations. The main objective of this paper is to analyze the effect of the ionic wind on the particle collection efficiency in such systems. The high voltage magnitude and the frequency are the major parameters taken into account. With the wire-to-plane ESPs, PIV results show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and viscous forces. With this configuration, the particle trajectory is 3-D. In the case of the plane-to-plane ESP, a 2-D analysis of the time-averaged flow can be accepted. The time-averaged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of the ionic wind on the primary flow in such a configuration is negligible. The correlation between the electrohydrodynamic flow and the collection efficiency shows that increasing the ionic wind magnitude did not improve necessarily the electrostatic precipitation effectiveness of submicrometer particles, particularly using DBD precipitators.

Collection efficiency of submicrometre particles using single and double DBD in a wire-to-square tube ESP

The aim of this work is to study the collection of submicrometre particles charged by a dielectric barrier discharge (DBD) in two types of wire-to-square glass tube electrostatic precipitators (ESPs). They are, respectively, designated as single DBD-ESP and double DBD-ESP, depending on the absence or presence of a dielectric layer around the high-voltage wire electrode. The experiments are performed with incense smoke particles having a mean size of about 0.32 µm. An aerosol spectrometer is employed for characterizing the size distribution of these particles at the outlet of the ESPs. The collection efficiency is estimated for various applied voltages and frequencies (ranges: 8–28 kV, 0.3–1000 Hz) at a fixed air flow rate (5.1 L min−1). The electrical measurements show that in the case of the single DBD-ESP, the discharge mode is rather homogeneous. In contrast, the discharge has a filamentary behaviour in the case of the double DBD-ESP. Results show that the particle collection efficiency of both ESPs is higher at high applied voltages and within a certain frequency range. However, corroborating the collection efficiency results with the power consumption measurements reveals that the double DBD-ESP offers better performances for a larger frequency range.

Smart Home Precipitator for Biomass Furnaces: Design Considerations on a Small-Scale Electrostatic Precipitator

With the use of wood pellets becoming more popular for heating in private households, an increase in particulate matter problems across urban areas has been detected. As this contributes to significant health risks, effective reduction of dust emissions will become mandatory even for comparably small heating systems. The smart home precipitator was designed for this scope of application. This paper demonstrates the development steps aiming at a cost-effective precipitator that can be used for central heating processes up to 30 kW. It starts with research on the mechanical design and on the collection efficiency for the development of a space-saving structure with comparable large collection area. In a next step, two different circuit topologies for the high-voltage power supply have been analyzed. The latest and final work step in the design phase was the development of a smart and efficient control algorithm using fuzzy logic for dynamic optimization.

Effect of a filamentary discharge on the particle trajectory in a plane-to-plane DBD precipitator

In this paper, particle velocity fields inside a plane-to-plane dielectric barrier discharge (DBD) precipitator are investigated using time-resolved particle image velocimetry. The main objective is to analyse the effect of a filamentary discharge on the particle trajectory. A sine wave high voltage (24 kV, 30 Hz) is applied to create a DBD inside a planar gap (6.4 mm) filled with particles with a mean size of about 0.28 µm. The time-averaged velocity of the flow in the centre of the channel is about 1 m s−1.After the establishment of the discharge several filaments cross the gap, and induce a strong effect on the particle trajectory. During a complete period of the voltage, successive phenomena are observed. Before the first filament propagation, the shape of the velocity profiles is typical of a laminar flow. At the early stage following the filament propagation across the gap, the grey-level images show a sudden disappearance of the particles at the same location where the filament takes place. This is due to the fast precipitation of particles. During the positive half-cycle, the particles migrate mainly towards the grounded electrode due to their positive net charge. At the end of a half-cycle, the polarity of the electric field is reversed then the particles initially charged return towards the channel centre. Consequently, the particles oscillate delaying their collection.

Effect of Relative Humidity on the Collection Efficiency of a Wire-To-Plane Electrostatic Precipitator

This paper aims to analyse the influence of the atmospheric relative humidity level (RH) on the collection efficiency of a wire-to-plane electrostatic precipitator (WP-ESP). The experiments were performed with incense smoke particles having a mean size of about 0.28 µm. An aerosol spectrometer was employed for characterizing the size distribution of these particles at the outlet of the ESP. Then, the total and fractional collection efficiencies were estimated for different relative humidity levels ranging from 40 to 70 %. Various DC applied voltages in the case of positive and negative polarities have been under consideration. For given atmospheric conditions, the results obtained with the aerosol spectrometer show that the performances of the ESP increases with the applied voltage (range: 10 to 40 kV) and the particle diameter (range: 0.2 to 0.7 µm). The collection efficiency is higher at increased RH. The negative corona discharge is overall more effective than the positive one. However, the difference between the two polarities becomes minor at high RH.

Interpretation of surface potential measurements performed with the vibrating capacitive probe of an electrostatic voltmeter

In case that the vibrating capacitive probe of an electrostatic voltmeter is facing a metallic plate of known electric potential V, which can be easily imposed by connecting it to a DC high-voltage supply, the value displayed by the instrument is equal to V. The same surface potential measurement technique is employed to characterize the charging state of insulating materials, such as films or non-woven media. The aim of the paper is to give some elements of answer to the following question: What significance can be attributed to the value displayed by the electrostatic voltmeter when the charge is non-uniformly distributed at the surface of the bodies examined by the probe and no constant surface potential can be defined? The measurements were performed for some simple experimental models that simulate surface potential non-uniformity. Thus, a copper wire, a copper rod, and two aluminium strips, connected to a high-voltage supply (V = 875 V) were located at 5 mm above a grounded metal plate. The vibrating capacitive probe was placed at various distances h above the grounded plate and at various distances x from the axial plan of the high-voltage strip/rod/wire - grounded plate system. Different V(x) curves obtained for each of the situations under study, pointing out that the value displayed by the instrument depends on the distribution of the potential across the surface examined by the probe. A commercial computer program based on the superficial charge simulation method was employed for the numerical analysis of the electric field in a simplified model of the geometric system formed by the probe, the high-voltage strip/rod/wire, and the grounded plate. The potential that anneals the electric field at the surface of the probe (to simulate its principle of operation) was calculated by an iterative method. A good agreement was found between the results of the numerical simulations and the experimental data.

Collection of submicron particles using DBD electrostatic precipitator in wire-to-square tube configuration

The aim of the present work is to investigate the capability of a Wire-to-Square Tube Electrostatic Precipitator (or WST-ESP) to collect submicron particles using a Dielectric Barrier Discharge (DBD). A parametric study is carried out to evaluate the effects of four control variables that might affect the collection efficiency of the WST-ESP: diameter of the corona wire electrode, width of the ground electrode and the area of the tube section. The experimental data show that the wire diameter has a negligible effect on the WST-ESP collection characteristics. However, better overall performances can be obtained by putting in parallel several WST-ESPs with reduced section. The extension of the ground electrode and its discretization increase the collection efficiency.

Study of DBD precipitator energized by a modified square waveform voltage

This experimental work is aimed at evaluating the effects of high voltage waveform (modified square waveform) on the collection efficiency of a wire-to-square tube electrostatic precipitator using dielectric barrier discharge. The experiments are performed with incense smoke particles having a mean size of about 0.32 μm. An aerosol spectrometer is employed for characterizing the size distribution of these particles at the outlet of the electrostatic precipitator. The collection efficiency is estimated for various applied voltages (ranges: 4 to 20 kV) at fixed frequency (100 Hz) and flow rate (10 L.min-1). The input parameters under study are the pulse duration, the rise and fall times, the presence of an Offset, and the plateau of the high voltage. The experimental results show that the square waveform with modified plateau is able to increase the performance of the electrostatic precipitation.

Analysis of electric field and current density in an electrostatic precipitator

This paper aims at analysis of the monopolar ionized field in an Electrostatic Precipitator (ESP). The corona parameters are analyzed by a combined iterative computational technique based on the Finite Element Method (FEM) and Charge Simulation Method (CSM). We proposed the introduction of a potential corresponding to the critical minimum ionization field directly in the finite element formulation as a Dirichlet condition. The computational model is validated by a comparison with experimental measurements of current density and electric field and with data from the electrostatic precipitator literature on a simple system.