J. Dekowski

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).

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.

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.

Electrohydrodynamic flow patterns in a wide spacing spike-plate electrostatic precipitators under negative coronas

Publisher Summary This chapter presents an electrohydrodynamic (EHD) flow patterns in a wide-spacing spike-plate electrostatic precipitation (ESP) under negative corona, which are categorized based on the 3D-particle image-velocimetry method. For negative corona, irregular locations of discharge tufts on the surface of the wire introduce quasi-steady EHD flows that contribute to the redistribution of pre-existing turbulence and oppose to the formation of large-scale secondary flow. The formation of EHD flow patterns as well as their effect on the transport of submicron and micron dust particles is discussed based on the dimensionless analysis of particle-transport equation. Based on the experimental results, five EHD flow patterns are characterized and correlated to the ratio between EHD number and Reynolds number squared.

Measurement of the flow velocity field in multi-field wire-plate electrostatic precipitator

In this paper results of Particle Image Velocimetry (PIV) measurements of the partiele flow velocity fields in a wire-to-plate type electrostatic precipitator (ESP) are presented. One or two grounded stainless-steel plate electrodes and seven wire electrodes in the middle of the ESP height were used. The measurements were carried out in the plane placed perpendicularly to the wire electrodes (for the ESP version with two plate electrodes) and in four planes placed parallel to the wire electrodes (for the ESP version with one plate electrode). Either negative or positive voltage polarity was applied to the wire electrodes. The main gas flow velocity was 0.14 m/s.The obtained results showed strong influence of the electrohydrodynamic (EHD) forces on the flow patterns, which exhibited strong upstream and downstream vortexes. The experiment confirmed that the flow patterns in the ESP have 3-dimensional character.

Laser measurements of flow fields in electrostatic precipitator models using PIV method

There is still interest in improving electrostatic precipitator (ESP) collection of fine particles (micron and submicron sizes). However, 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 reuslts of the Particle Image Velocimetry (PIV) measurements of the particle flow velocity field in a wire-to-plate type ESP model with seven wire electrodes are presented. The PIV measurements clearly confirmed formation of the secondary flow pattern changes caused by the strong interaction between the primary and secondary flows are more pronounced for higher operating voltage (high electrohydrodynamic number NEHD) and lower primary flow velocity (lower Reynolds number Re).

Measurement of flow velocity field in corona discharge radical shower non-thermal plasma reactor

In this paper results of the Particle Image Velocimetry (PIV) measurements of the flow velocity fields in a corona discharge radical shower (CDRS) non-thermal plasma reactor are presented. The discharge electrode of the CDRS reactor was a thin tube with several nozzles, through which a gas mixture was added to the reactor. The velocity fields were measured in two flow planes perpendicular to the electrode tube: the first plane was set between two nozzles in the middle of the discharge electrode, and the second passed through one of them. In both planes electrohydrodynamically generated vortexes were found. However, in the plane set between the two nozzles, the vortexes were smaller. This investigation shows that in the reactor with the CDRS discharge electrode is used, the vortexes revolve in the opposite direction to those generated in the non-thermal plasma reactors with smooth wire discharge electrodes. The flow patterns in the reactor with CDRS electrode are more stable than those with the smooth wire electrode. This can have an influence on the performance of the CDRS reactors.

Electrohydrodynamically induced secondary flow in non-thermal plasma reactor and its effect on flue gas NOx cleaning

Summary form only given, as follows. Laser-induced fluorescence (LIF) proved to be a useful diagnostic method for in-situ two-dimensional observation of the discharge-induced plasma chemistry processes responsible for NOx decomposition occurring in nonthermal plasma reactors. Using this powerful technique, It was found that the corona discharge-induced removal of NO molecules in a needle-to-plate and corona radical shower nonthermal plasma reactors occurs not only in the vicinity of the plasma region formed by the corona streamers and in the downstream region of the reactor but also in the upstream region of the reactor. The study, carried out using other laser techniques, i.e. the laser visualization and particle image visualization (PIV), showed that a strong electrohydrodynamic (EHD) flow from the discharge electrode towards both the upstream and downstream directions of the main flow is formed.

CuBr laser in measurements of fluid-flow fields with PIV method

Pulsed metal vapour lasers in general, and pulsed copper vapour lasers in particular are now considered to be enabling technology for a number of important processes. The pulsed conventional copper vapour lasers (CVLs), the technology of which has continued to develop to the point today where multiple green/yellow laser beams of more than 1 kilowatt average power are routinely generated at around 1% efficiency (Lawrence Livermore National Laboratory), are the highest power visible lasers ever developed. Today the conventional CVLs producing 100 W average power at 5 kHz pulse recurrence frequency and about 1% efficiency are at the laser market. However, due to their high operating temperatures (1500-1600 degree(s)C), the conventional CVLs are of complex construction, require flowing gas system, and have long warm-up time (90-120 minutes). The pulsed copper bromide (CuBr) laser is another representative of the copper laser family, which does not exhibit the disadvantages associated with the conventional devices. CuBr lasers have been demonstrated to have high-efficiency (2-3%) and high specific output powers (0.1-1 Wcm-3). Up to now a CuBr laser of 120 W average output power has been reported. There is no other type of laser which can deliver such a high average power in the visible range with such a high efficiency and high beam quality. The rapid development of laser technique in the past decade allows to introduce new methods of measurements into various areas of scientific and technical activities. One of the possibility is to apply the laser technique to visualisation of flows and to particle image velocimetry (PIV). In this paper we present the potential of CuBr laser in this field.