A bipolar charge measurement system for aerosol characterization

This paper reports the development of a bipolar charge measurement system for aerosol characterization. The system incorporates a front-end cylindrical arrangement consisting of two "D"-shaped precipitation sections. Each of these sections incorporates wire electrodes maintained at a high potential of opposite polarity. The interface between the two "D" sections is a thin wedge, the front-end of which acts as a bifurcation for the incoming aerosol. The test aerosol is drawn through the bifurcation separator using a suction pump, and subject to an appropriate electric field. Depending on the electric field distribution and air-flow characteristics, particles of the same polarity as that of the potential applied to the wire electrodes are deflected toward an outer collecting wall and give up their charge. This precipitation section is connected to a series of five "D"-shaped electrodes (open-ended Faraday chambers) to collect the charged aerosol of different charge to mass ratio. Both analytical and numerical calculations were performed to optimize the design of the manufactured system. Preliminary tests were carried out with an aerosol of known size and charge distribution. The results obtained are in good agreement with the theoretical predictions.