Patent ID: 7031133

Claim:
A device for adjusting the electrical charge distribution of an aerosol, including: a body defining a flow path to guide passage of an aerosol in a flow direction through the body; a corona discharge component mounted with respect to the body and having a corona discharge region disposed along the flow path; an electrically conductive structure mounted with respect to the body, electrically isolated from the corona discharge component and disposed in spaced apart relation to the corona discharge component; and circuitry for, generating a voltage between the corona discharge region and the conductive structure, said voltage having opposite polarities during respective first and second periods alternating at a selected frequency to produce an electrical field between the corona discharge component and the conductive structure that alternates between the opposite polarities at the selected frequency; wherein the voltage, during a predetermined part of each first period, exceeds a corona discharge threshold voltage thereby causing ions of a first polarity to enter an aerosol space along a flow path for a merger with the aerosol to change an electrical charge distribution of the aerosol; wherein the conductive structure is sized to provide the electrical field with a field strength that diminishes rapidly in the flow direction away from the aerosol space; and wherein the selected frequency and the predetermined part of each first period are selected with respect to the voltage, and with respect to the distance between the corona discharge region and the conductive structure, to reduce a field charging effect of the electrical field relative to a diffusion charging effect and prevent any substantial loss of ions to the conductive structure.