Janusz Kulon

Efficiency of smoke removal by charged water droplets

The removal of fine aerosol particles such as dust or smoke by charged droplets was investigated experimentally. The droplets were sprayed by a rotary atomiser and simultaneously charged inductively. The cigarette smoke was used as a source of submicrometer dust. Smoke was charged in a specially designed corona-discharge charger. The suppression of particle concentration was determined after different time intervals of spraying of water. The electrical charging of droplets significantly increases the efficiency of removal of fine particles from air as compared to the uncharged aerosol. Further improvement was obtained after charging smoke particles. The cleaning process was up to four times better for charged smoke and droplets than that for uncharged species.

Simultaneous measurement of particle size and electrostatic charge distribution in DC electric field using phase Doppler anemometry

The proposed noninvasive method of measurement of the charge level on a population of particles employs the phase Doppler anemometry (PDA) technique in conjunction with a high-resolution computer-controlled traversing system. The PDA system was used to track the motion of charged particles in the presence of a DC electric field. By solving the equation of particle motion in a viscous medium combined with the simultaneous measurement of its size and velocity, the magnitude as well as the polarity of the particle charge can be obtained. In order to detect particles with high electrical mobility and to cover the wide range of electrostatic charges the probe volume was moved mapping the velocity of the particles within the space between the parallel-plate electrodes. The preliminary experimental tests were carried out on dioctyl-phthalate aerosol droplets produced by nebulizing isopropanolic solutions using a Medic-Aid Sidestream nebulizer. The narrow size distribution, in the range from 0.5 to 3 /spl mu/m, was achieved using this method of aerosolization. The experimental results show that inherent electrostatic charge on dioctyl-phthalate droplets ranged from -250 to 250 electrons with an average charge-to-mass ratio of 0.24 /spl mu/C/g. After charging the aerosol using corona source the average charge-to-mass ratio increased to 20 /spl mu/C/g. The results demonstrate the capability of the technique to allow real-time determination of particle size and charge with a high-particle-count rate on the order of several thousands particles per second.

The measurement of bipolar charge on aerosols

Abstract This paper describes a novel automatic method for measurement of bipolar charge on aerosols. The developed system is dedicated to measuring aerosols existing in the form of short duration, high velocity plumes with a wide angle of particle dispersion. The system incorporates a front-end cylindrical arrangement consisting of two “D” shaped precipitation sections followed by a series of charge sensing electrodes. Apart from theoretical and construction details, the results of the experimental tests carried out with unipolarly and bipolarly charged aerosols are presented.

Comparative Study of Square and Sine-Wave Excitation Methods for the Measurement of Aerosol Particles Charge and Size Distribution Using Phase Doppler Anemometry

This paper describes and compares two particle excitation methods, square and sine wave, used in conjunction with an application of phase Doppler anemometry to simultaneously obtain particle size and charge in real time. Different signal-processing strategies for particle velocity and size estimation are investigated, including quadrature demodulation, spectral analysis, and correlation technique. The systems performance has been tested using Monte Carlo simulations obtained from the synthesized Doppler burst signals. A mathematical model has been developed to estimate the percentage of particles captured in the measurement volume and successfully analyzed by the signal-processing system, leading to the optimization of the system parameters. Finally, some preliminary experimental results are given. It can be concluded that the measurement system using the square-wave excitation and based on the spectral analysis performs better in terms of the measurement range, SNR requirement, and particle capture efficiency.

Cramér-Rao Bounds for a Laser Doppler Anemometer: The effect of the particle trajectory via the measurement volume

This paper derives the Cramér-Rao Bound for the frequency estimation of the noisy Doppler Burst Signal from the Laser Doppler Anemometry. The problem is solved by considering the effect of the particle trajectory via the measurement volume together with the dependency of the burst length on the Doppler frequency. The results provide an analytical expression for the lowest variance of the estimation of the Doppler frequency as a function of the direction of particle velocity relative to the fringe pattern.

Simultaneous analysis of particle size and electrostatic charge distribution using phase Doppler anemometry

The proposed noninvasive method of measurement of the charge level on a population of particles employs the phase Doppler anemometry (PDA) technique in conjunction with a high-resolution computer controlled traversing system. The PDA system was used to track the motion of charged particles in the presence of a DC electric field. By solving the equation of a particle motion in a viscous medium combined with the simultaneous measurement of its size and velocity the magnitude as well as the polarity of the particle charge can be resolved. In order to detect particles with high electrical mobility and to cover the wide range of electrostatic charges the probe volume was moved mapping the velocity of the particles within the space between the parallel plate electrodes. The preliminary experimental tests were carried out on dioctyl phthalate aerosol droplets produced by nebulising isopropanolic solutions using a Medic-Aid Sidestream nebuliser. The experimental results show that inherent electrostatic charge on dioctyl-phthalate droplets ranged from -250 to 250 electrons with an average charge-to-mass ratio of 0.24/spl mu/C/g. In case of precharged aerosol the average charge-to-mass ratio increased to 20/spl mu/C/g. The results presented demonstrate capability of the technique to allow real-time determination of particle size and charge with a high particle count rate in order of several thousands particles per second.

Pelvis feature extraction and classification of Cardiff body match rig base measurements for input into a knowledge-based system.

The purpose of this paper is to determine whether it is possible to use an automated measurement tool to clinically classify clients who are wheelchair users with severe musculoskeletal deformities, replacing the current process which relies upon clinical engineers with advanced knowledge and skills. Clients’ body shapes were captured using the Cardiff Body Match (CBM) Rig developed by the Rehabilitation Engineering Unit (REU) at Rookwood Hospital in Cardiff. A bespoke feature extraction algorithm was developed that estimates the position of external landmarks on clients’ pelvises so that useful measurements can be obtained. The outputs of the feature extraction algorithms were compared to CBM measurements where the positions of the client’s pelvis landmarks were known. The results show that using the extracted features facilitated classification. Qualitative analysis showed that the estimated positions of the landmark points were close enough to their actual positions to be useful to clinicians undertaking clinical assessments.

Real-time particle size and charge estimation from laser Doppler burst signals using Quadrature Demodulation and correlation techniques

This paper describes an integrated signal processing system based on Quadrature Demodulation (QD) and correlation techniques to obtain particle size and charge simultaneously using phase Doppler anemometry (PDA). By solving the equation of particle motion in an AC electric field combined with the measurement of its size and velocity, the magnitude as well as the polarity of the particle charge can be obtained. The Matlab Simulink models of the signal processing system have been implemented and tested on the particle with velocity amplitude approximately from 16 mm/s to 550 mm/s. The corresponding charge measurement range is from several electrons to the saturation level.

Maximum Likelihood Estimator, FFT Estimator and Cramér-Rao bounds of the laser Doppler frequency: The effect of a particle trajectory through the measurement volume

This paper addresses the problem of estimating the Doppler frequency in Laser Doppler Velocimetry (LDV) systems by taking into account the effect of the particle trajectory via the measurement volume. The dependency of the burst length on the Cramér-Rao lower bound (CRLB) and the Doppler frequency estimation is investigated by employing the 2D model of the Doppler Burst Signal with the Gaussian envelope. The Maximum Likelihood Estimator (MLE) equations are solved for estimates of the Doppler frequency for LDV systems operating in one particle scattering mode. The numerical examples show the performance of the MLE and FFT with various parameter configurations compared with the derived CRLB. The numerical results confirm the validity of the analysis in terms of the relative effect of the particle trajectory, relative measurement time, size of the volume and signal-to-noise ratio on the accuracy of the estimation.

The effect of a particle trajectory through the measurement volume on the accuracy of the laser Doppler frequency estimation

The minimum achievable uncertainty of the Doppler frequency estimation of any unbiased estimator is given by the Cramér-Rao lower bound (CRLB). In this paper, we consider the effect of the particle trajectory via the measurement volume on the CRLB by employing the 2D model of the Gaussian envelope of the Doppler Burst Signal (DBS). The simulation results confirmed the theoretical predictions in terms of the relative effect of the particle trajectory, the measurement time, the size of the volume and SNR on the accuracy of the Doppler frequency estimation. The obtained analytical expression for the CRLB could be applied in engineering applications, e.g. requiring the estimation of the uncertainty of cross flow particle velocity with a known mean flow velocity component.