For this study, a unipolar corona-based ionizer was constructed and experimentally evaluated for charging efficiencies and losses of ultrafine particles in the size range of 15-75 nm at different corona voltage, ion trap voltage and particle flow rate. The corona voltage was applied to the ionizer between 2.0-3.0 kV. The discharge currents increased from 0.16 nA to 4.23 mu A and the ion number concentration increased from 6.27 x 10(9) to 1.36 x 10(14) ions/m(3). Increasing the corona voltage lead to a higher discharge current and ion number concentration in the ionizer. The best intrinsic charging efficiency of the ionizer was about 92.15-99.33% for particle diameters ranging from 15 to 75 nm, and occurred at corona voltage, ion trap voltage and particle flow rate of about 3.0 kV, 100 V, 0.6 L/min, respectively. At a given corona voltage, the extrinsic charging efficiency increased as the particle flow rate increased. The best extrinsic charging efficiency ranged from 14.93 to 57.70% for particle diameters increasing from 15 to 75 nm, and occurred at corona voltage, ion trap voltage and particle flow rate of about 2.6 kV, 100 V, and 1.5 L/min, respectively. In the present ionizer, the highest electrostatic loss was observed for particles with a diameter of about 45 nm, and it was about 88.03% at a corona voltage of 3.0 kV and an ion trap voltage of 200 V. Finally, the highest diffusion loss of about 22.66% was seen to occur with singly charged particles with a diameter of 15 nm at the particle flow rate of about 0.6 L/min.
