1. Jerzy Mizeraczyk XII INTERNATIONAL CONFERENCE ON ELECTROSTATIC PRECIPITATION Nuernberg May 9 – 13, 2011 Centre for Plasma and Laser Engineering The Szewalski Institute of Fluid-Flow Machinery Polish Academy of Sciences Gdańsk, Poland PIV MEASUREMENTS OF ELECTROHYDRODYNAMIC FLOW IN ESPs

2. Motivation of laser investigations of flow patterns in electrostatic precipitators Interest in improving electrostatic precipitator (ESP) collection of fine particles (micron and submicron sizes). How does the EHD flow caused by the presence of electric field and charge in ESPs influence the particle precipitation process? 2

3. OUTLINE Laser flow visualization Principles of laser flow visualization Particle Image Velocimetry (PIV) Principles of of 2-dimensional (2D) and 3-dimensional (3D) Particle Image Velocimetry Products of PIV (flow velocity field, flow streamlines, vorticity map) Example of PIV measurements in a spike-to-plate electrostatic precipitator (ESP): PIV measurement of the dust particle flow structures Structures of the dust particle deposits Correlation between the dust particle flow structures and the dust particle deposit structures Conclusions 3

4. PRINCIPLE OF PARTICLE IMAGE VELOCIMETRY (PIV) Flow seeded with particles following the motion of the flow Light source for illumination of the flow Camera to capture 2 images of the motion of the seed particles v =  S / (t 2 – t 1 ) 4 2 consecutive CCD images

5. 2D PARTICLE IMAGE VELOCIMETRY - PRINCIPLE 5

6. EXPERIMENTAL SETUP FOR 2D PIV MEASUREMENTS The standard PIV equipment (Dantec PIV 1100): - a twin second harmonic Nd-YAG laser system capable of changing  t = t 2 – t 1 - cylindrical telescope to produce a laser beam sheet - CCD camera,  t min = 2  s, 1018x1018 pixels - image processor - PC computer 6

7. 7 EXPERIMENTAL SETUP FOR 3D PIV MEASUREMENTS

8. 8 Products of PIV (flow velocity field, flow streamlines, vorticity map)

9. Time-averaged flow streamlines in the ESP V p = 0.9 m/s Flow streamlines not much disturbed in comparison with no voltage flow streamlines. Some disturbances near the plate electrodes in the discharge region. V p = 0.6 m/s Stronger disturbances than for the V p =0.9 m/s, vortices in the discharge region. V p = 0.2 m/s Strong vortices in the discharge region. Pair of vortices placed 100 mm dowstream the wire electrode block the flow in the ESP duct centre. Laser flow visualization and PIV - example Study of the dust particle flow structures in a wire-plate ESP – laboratory 9

10. Flow velocity field in the ESP model at a main flow velocity of 0.6 m/s. Positive polarity, voltage 24 kV. 10 LASER FLOW VISUALIZATION AND PIV IN ESP Study of the dust particle flow structures in 7-electrode wire ESP - laboratory

11. 11 Primary flow velocity: 0.6 m/s (Reynolds number 4000) Flow gas: ambient air Dust: TiO 2 particles (2D PIV) or cigarette smoke (3D PIV) Operating voltage: 0 – 28 kV (positive polarity) Discharge current: 0 – 210  A (Ehd number up to 3 * 10 8 ) Spike electrode: 12 spikes 200 mm long 1 mm thickness 14 measurement planes: A, B, C - longitudinal E - N - transverse EHD FLOW PATTERNS IN A SPIKE-PLATE ESP EHD FLOW PATTERNS IN A SPIKE-PLATE ESP UNDER POSITIVE AND NEGATIVE POLARITIES UNDER POSITIVE AND NEGATIVE POLARITIES

12. Side view V [m/s] 12 EHD FLOW PATTERNS IN A WIDE SPACING SPIKE-PLATE ESP EHD FLOW PATTERNS IN A WIDE SPACING SPIKE-PLATE ESP UNDER POSITIVE AND NEGATIVE POLARITIES UNDER POSITIVE AND NEGATIVE POLARITIES

13. IMAGE OF THE PRECIPITATED DUST Dust 13 EHD FLOW PATTERNS IN A SPIKE-PLATE ESP EHD FLOW PATTERNS IN A SPIKE-PLATE ESP UNDER NEGATIVE POLARITY UNDER NEGATIVE POLARITY

14. FLOW PATTERN AND IMAGE OF THE PRECIPITATED DUST 14 U = -27.4 kV I = 260  A Plane A Dust EHD FLOW PATTERNS IN A SPIKE-PLATE ESP EHD FLOW PATTERNS IN A SPIKE-PLATE ESP UNDER NEGATIVE POLARITY UNDER NEGATIVE POLARITY

15. 15 3D PIV MEASUREMENT OF VELOCITY X-COMPONENT EHD FLOW PATTERNS IN A SPIKE-PLATE ESP EHD FLOW PATTERNS IN A SPIKE-PLATE ESP UNDER POSITIVE POLARITY UNDER POSITIVE POLARITY

16. Side view 16 V [m/s] Front view NARROW ESP WITH LONGITUDINAL WIRE ELECTRODE

17. Y in mm X in mm Air flow generated by DC corona discharge Electrode configuration determines the flow direction Flow velocity up to 1 m/s Flow rate up to 630 cm 3 /s EHD gas pump features: Velocity profiles at the exit section of EHD gas pump Velocity profile at the exit of EHD gas pump (3D PIV) EHD gas pump overview Flow generated by EHD gas pump PIV measurement EHD GAS PUMP 17

18. Length of HV and grounded electrodes: 50 mm Length of floating interelectrodes: 45 mm High voltage electrodes width: 15 mm HV and FL interelectrodes in optimum position Floating interelectrodes width: 3 mm Floating to grounded electrode distance: 6 mm Grounded electrodes width: 3 mm Grounded to floating electrode distance: 13 mm Dielectric: glass plate – 2 mm thickHigh voltage: U pp = 32 kV, f = 1.5 kHz Airflow velocity m/s Time-averaged streamlines of a airflow induced by multi DBD actuator with floating saw-like interelectrodes 18

19. EXPERIMENT - CALCULATION Flow patterns in wire-plate ESP for various dust densities ExperimentCalculation – K. Adamiak & P. Atten 19

20. Flow patterns in wire-plate ESP for various Ehd/Re 2 ratio Calculation – Chun & ChangExperiment Ehd / Re 2 – a measure of the EHD disturbance of the primary flow Ehd = I t * L 3 / (A *  * g 2 *  i ) Re = U 0 * L / g EXPERIMENT - CALCULATION 20

21. LASER FLOW VISUALIZATION IN INDUSTRIAL ESP 21

22. LASER SYSTEM FOR FLOW VISUALIZATION ON THE TOP OF INDUSTRIAL ESP 22

23. All four sections ON, hammering at t = 0 in section 4 LASER FLOW VISUALIZATION IN INDUSTRIAL ESP Light-green spots – dust in the ESPYellow lines – flow streamlines deduced from the flow images 23

24. CONCLUSIONS 24 Laser visualization and Particle Image Velocimetry proved to be useful instruments in studying flow and collection phenomena in electrostatic precipitators Owing to the PIV measurement a correlation between structures of the particle flow and particle deposit in the spike-plate ESP was found. The particle flow structures explain how the particle deposit structures are formed. Basing on the PIV results we found a correlation between the particle flow structures and the total collection efficiency for the various configurations of spike-type electrode. Negative effect for downstream-directed one- sided electrode.

25. Centre for Plasma and Laser Engineering Institute of Fluid Flow Machinery Polish Academy of Sciences, Gdańsk, Poland J. Mizeraczyk, J. Podliński, M. Kocik, M. Dors, J. Dekowski, A. Niewulis COLLABORATORS Department of Electrical and Electronic Engineering Oita University, Japan T. Ohkubo, Y. Nomoto, S. Kanazawa Department of Engineering Physics McMaster University, Hamilton, Ontario, Canada J.-S. Chang, D. Brocilo, K. Urashima, Y.N. Chun, A.A. Berezin Laboratoire d'Electrostatique et de Matériaux Diélectriques Université Joseph Fourier, Grenoble, France P. Atten Laboratoire d’Etudes Aérodynamiques Université de Poitiers, France G. Touchard Department of Ecological Engineering Toyohashi University of Technology, Japan A. Mizuno 25