Marek Kocik

Measurements of the velocity field of the flue gas flow in an electrostatic precipitator model using PIV method

Abstract In this paper, results of use of the PIV method to measure the flow field in a wire-plate type ESP model are presented. The results show that the PIV method is well suited to investigate the flow field in ESP models, in particular the characteristics of secondary and reversal flows, which increase the flow turbulence. The PIV investigation of the near-collecting electrode region shows the importance of the secondary flows, the velocity of which is several tens of cm/s. This means that the secondary flows can have a great impact on the motion and precipitation of small particles, mainly those in the submicron range.

Laser Flow Visualization and Velocity Fields by Particle Image Velocimetry in an Electrostatic Precipitator Model

AbsractAlthough improving electrostatic precipitator (ESP) collection of fine particles (micron and submicron sizes) remains of interest, it is not yet clear whether the turbulent flow patterns caused by the presence of electric field and charge in ESPs advance or deteriorate fine particle precipitation process. In this paper, results of the laser flow visualization and Particle Image Velocimetry (PIV) measurements of the particle flow velocity fields in a wire-to-plate type ESP model with seven wire electrodes are presented. Both experiments were carried out for negative and positive polarity of the wire electrodes. The laser flow visualization and PIV measurements clearly confirmed formation of the secondary flow (velocity of several tens of cm/s) in the ESP model, which interacts with the primary flow. The particle flow pattern changes caused by the strong interaction between the primary and secondary flows are more pronounced for higher operating voltages (higher electrohydrodynamic numbernehd) and lower primary flow velocities (lower Reynolds number Re). The particle flow patterns for the positive voltage polarity of the wire electrodes are more stable and regular than those for the negative voltage polarity due to the nonuniformity of the negative corona along the wire electrodes (tufts).

Diagnostics of NO oxidation process in a nonthermal plasma reactor: features of DC streamer-corona discharge and NO LIF profile

Features of the streamer-corona discharge and the NO processing area in corona radical shower system was studied experimentally. The time evolution of the streamer-corona discharges induced by laser irradiations was measured to understand the discharge characteristics responsible for NO removal. Using the wide-range planar laser-induced fluorescence imaging (image size: 240 mm in width and 35 mm in height), two-dimensional distributions of ground-state NO were observed not only at the discharge zone but also both the downstream and the upstream regions of the reactor. The obtained results showed that the density of NO molecules decreased not only in the plasma region formed by the corona streamers and downstream region of the reactor but also in the upstream region of the reactor. In the present reactor at low main gas flow rate, it was considered that electrohydrodynamic (EHD) flow became to be dominant, and the flow toward the upstream affected the decrease of NO in the upstream region. As the EHD-induced secondary flow is correlated with the current flow from the stressed electrode to grounded electrode, the control of the streamers seems to be an important factor for optimizing the reactors used for NOx removal.

Particle image velocimetry measurements of wire-nonparallel plates type electrohydrodynamic gas pump

2D particle image velocimetry (PIV) measurements were performed in a wire nonparallel plates type electrohydrodynamic (EHD) gas pump. Using simultaneously two CCD cameras allowed obtaining high resolution vector maps which illustrate the flow patterns generated inside the EHD gas pump.

Electrohydrodynamic flow and its effect on ozone transport in corona radical shower reactor

New arguments supporting the supposition that the ozone is transported along a corona discharge radical shower (CDRS) reactor by the electrohydrodynamic (EHD) flow are presented. The arguments are based on the analysis of the corona discharge, which is a precursor of the EHD flow in the CDRS reactor, and on the measurements of velocity field of the EHD flow in the CDRS reactor by the particle image velocimetry (PIV). The obtained velocity flow structures and the possible causes of the ozone transport in the CDRS, i.e., diffusion, additional gas flow, EHD flow, and convection by the main flow, were discussed basing on the conservation equations for the EHD flow. The discussion showed that the EHD flow plays a dominant role in the ozone transport. This is also supported by the results of a simple phenomenological model for one-dimensional description of EHD-induced ozone transport in the CDRS reactor. The results of the computer simulation based on this model explained the main features of the measured ozone distribution in the CDRS reactor, establishing the EHD flow as the main cause of the ozone transport from the discharge region upstream, i.e., against the main flow.

Characteristics of DC Corona Streamers Induced by UV Laser Irradiation in Non-Thermal Plasma

Abstract Positive corona streamers are widely used in the field of air pollution control such as NOx or SOx removal and VOCs decomposition based on non-thermal plasma chemical process. In this study, the characteristics of DC positive corona streamers induced by UV laser irradiation are investigated in the tube-to-plane electrode configuration with electrode gap spacing of 3 cm. The streamer images were recorded using an ICCD camera with a nanosecond order time resolution. During the DC corona discharge, regular streamers appear with tens of ms intervals, the duration of which considerably fluctuates. This makes time resolved streamer observation by the ICCD camera extremely difficult. However, additional streamers with a predictable inception time can be induced by UV laser irradiation. As a result, the current waveform characteristics of the laser-induced streamers were obtained. In this work, three-dimensional streamer structures including the streamer propagation and branching were studied. Also the streamer propagation velocity was evaluated.

Observing Three-Dimensional Structures of Streamer Discharge Channels

Three-dimensional structures of atmospheric and underwater streamer discharges are reconstructed using a newly developed 3-D observation method based on stereophotography. In this method, a streamer discharge is captured from three directions simultaneously. The advantage of the foregoing is the 3-D reconstruction with the least uncertainty of the 3-D coordinate and easy pairing of identical streamer channels between the two photographs taken from different directions. Reconstructed 3-D structures exhibit all characteristic morphological properties of streamer channels such as branching and zigzag-shaped paths.

Images of electrohydrodynamic flow velocity field in a DC positive polarity needle-to-plate nonthermal plasma reactor

Images showing the flow pattern and velocity field in a positive polarity needle-to-plate nonthermal plasma reactor are reported. The images were obtained using the particle image velocimetry. They showed a strong secondary flow, caused by the electrohydrodynamic forces, which transport the working gas also in the upstream main-flow direction. This may influence operation of the nonthermal plasma reactors and affect their capability of gaseous pollutant remediation.

A System for Cooling Electronic Elements with an EHD Coolant Flow

A system for cooling electronic components where the liquid coolant flow is forced with ion-drag type EHD micropumps was tested. For tests we used isopropyl alcohol as the coolant and CSD02060 diodes in TO-220 packages as cooled electronic elements. We have studied thermal characteristics of diodes cooled with EHD flow in the function of a coolant flow rate. The transient thermal impedance of the CSD02060 diode cooled with 1.5 ml/min EHD flow was 7.8°C/W. Similar transient thermal impedance can be achieved by applying to the diode a large RAD-A6405A/150 heat sink. We found out that EHD pumps can be successfully applied for cooling electronic elements.

Electrohydrodynamic gas pump with both insulated electrodes driven by dielectric barrier discharge

In this paper, we report the use of a surface dielectric barrier discharge (DBD) for the generation of unidirectional flow inside a glass tube, using external ring electrodes. The electrodes were made of thin metal stripes mounted on the external wall of the glass tube and insulated with resin. One of the electrodes was grounded, the other was connected to an AC power supply. The DBD discharge was generated between the electrodes on the internal wall of the glass tube. As a result, pumping of air through the glass tube occurred. The presented discharge geometry is attractive for electrohydrodynamic (EHD) gas pumping since there is no direct contact between the external discharge electrodes and the pumped medium. The flow rate generated by the EHD pump was calculated using the measured flow velocity maps at the outlet of the pump. The flow velocity maps were obtained using 3D Particle Image Velocimetry (PIV) technique. It was found that the increase in frequency of the ac voltage caused an increase of the flow rate generated by the EHD pump. Accordingly, the increase in the flow rate occurred when the distance between the electrodes had been increased.