Aerosol charge altering device

A process for altering an electrical charge distribution of an aerosol, including:

• causing an aerosol to move in a flow direction along a flow path;
• disposing a corona discharge component along the flow path;
• disposing an electrically conductive structure in proximate spaced apart relation to the corona discharge component and electrically isolated from said component;
• generating a voltage between the corona discharge component and the conductive structure, at opposite polarities during respective first and second time segments 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;
• during a predetermined part of each first time segment, generating the voltage at an amplitude exceeding a corona discharge threshold, thus to cause ions of a first polarity to enter an aerosol space along the flow path for a merger with the aerosol to change an electrical charge distribution of the aerosol;
• and
• selecting a size of the conductive structure such that the electrical field has a field strength that diminishes rapidly in the flow direction away from the aerosol space;
• whereby generating the voltage includes selecting the predetermined part of each first time segment and the selected frequency with reference to the amplitude of the voltage and the distance between the corona discharge component and the conductive structure, to reduce a field charging effect of the electrical field relative to a diffusion charging effect and prevent any substantial ion precipitation losses.

A device for selectively charging an aerosol, including:

• a conduit for guiding an aerosol along a flow path, wherein the aerosol entering the conduit includes suspended aerosol particles;
• an active electrode disposed along the flow path;
• a passive electrode disposed proximate the active electrode and electrically isolated from the active electrode;
• and
• circuitry for generating an alternating voltage at a selected frequency between the active and passive electrodes to produce an electrical field along the flow path that alternates between opposite polarities at the selected frequency;
• wherein the alternating voltage has a magnitude sufficient to create a corona discharge at the active electrode and thus produce ions that enter the flow path for a merger with the aerosol particles to selectively alter an electrical charge distribution of the aerosol while substantially maintaining particle concentration, whereby a particle concentration level of a given portion of the aerosol downstream of the active and passive electrodes is substantially equal to an initial particle concentration level of that portion entering the conduit.

A system for characterizing aerosol particles, including:

• a conduit for guiding an aerosol along a flow path, wherein the aerosol entering the conduit includes suspended aerosol particles;
• an active electrode disposed along the flow path;
• a passive electrode disposed proximate the active electrode and electrically isolated from the active electrode;
• circuitry for generating an alternating voltage at a selected frequency between the active and passive electrodes to produce an electrical field along the flow path that alternates between opposite polarities at the selected frequency;
• and
• wherein the alternating voltage has a magnitude sufficient to create a corona discharge at the active electrode and thus produce ions that enter the flow path for a merger with the aerosol particles to selectively alter an electrical charge distribution of the aerosol thereby providing a selectively charged aerosol;
• and
• a particle characterizing instrument disposed to receive the selectively charged aerosol and adapted to separate the aerosol particles according to size, based on electrical mobility.

A device for selectively charging an aerosol, including:

• a conduit for guiding an aerosol along a flow path, wherein the aerosol entering the conduit includes suspended aerosol particles;
• an active electrode disposed along the flow path;
• a passive electrode disposed proximate the active electrode and electrically isolated from the active electrode;
• circuitry for generating an alternating voltage at a selected frequency between the active and passive electrodes to produce an electrical field along the flow path that alternates between opposite polarities at the selected frequency, the circuitry being adapted to generate the alternating voltage at magnitudes that exceed positive and negative corona discharge thresholds to alternatively produce positive and negative ions at the active electrode that enter the flow path for a merger with the aerosol particles, to alter an electrical charge distribution of the aerosol;
• and
• a circuit adapted to apply a displacement voltage to a selected one of the active and passive electrodes, and further adapted for controlling the displacement voltage to adjust the concentrations at which the positive and negative ions are produced relative to each other.