A widely used instrument capable of detecting and measuring PM is an electrical PM detector. A typical PM detector consists of an aerosol charger, an ion collector, and an aerosol electrometer. In the PM detector, aerosols are directed into the aerosol charger to charge the aerosol particles by ion-particle collisions via the diffusion charging andfield charging mechanisms. The charged aerosol then passes through an ion collector to remove excess ions and moves on to a highly sensitive aerosol electrometer for charge measurement [2,3]. Generally, an ion collector is one of the most important parts of the electrical PM detector because it can prevent contamination of the signal current to be measured by free ions potentially reaching the electrometer[4]. The ion collector typically uses the principle of electrostatic precipitation and has a geometrical configuration similar to the coaxial cylindrical electrostatic pre-cipitator. It consists of an inner electrode placed along the axis of an outer electrode. For generating an electrostaticfield inside the collector a DC voltage is applied to the inner electrode, while the outer electrode is grounded. When ions are introduced into the collector, the electrostatic force drives them toward the outer electrode where they deposit on the inner surface of the electrode. The design and performance evaluation of the ion collector has received little attention in the literature [5e12]. Higher applied voltages (10e150 V) andflow rates (5e15 L/min) were theoretically and experimentally studied by numerous works[5e7,12]. However, a mini-volume electrical PM detector commonly has been operated at volumetric aerosolflow rates lower than 5 L/min and therefore needed a compactable system for afield test and measurement. Therefore, an ion electrostatic collector needs to be designed and numerically and experimentally evaluated for the efficiency of collecting both negative and positive ions at ionflow rates smaller than 5 L/min and collection voltages lower than 50 V. The geom-etry, dimension and size of the ion collector would have influenced to the complexity and expense of the ion collector and then to keep
it cost effective.
A widely used instrument capable of detecting and measuring PM is an electrical PM detector. A typical PM detector consists of an aerosol charger, an ion collector, and an aerosol electrometer. In the PM detector, aerosols are directed into the aerosol charger to charge the aerosol particles by ion-particle collisions via the diffusion charging andfield charging mechanisms. The charged aerosol then passes through an ion collector to remove excess ions and moves on to a highly sensitive aerosol electrometer for charge measurement [2,3]. Generally, an ion collector is one of the most important parts of the electrical PM detector because it can prevent contamination of the signal current to be measured by free ions potentially reaching the electrometer[4]. The ion collector typically uses the principle of electrostatic precipitation and has a geometrical configuration similar to the coaxial cylindrical electrostatic pre-cipitator. It consists of an inner electrode placed along the axis of an outer electrode. For generating an electrostaticfield inside the collector a DC voltage is applied to the inner electrode, while the outer electrode is grounded. When ions are introduced into the collector, the electrostatic force drives them toward the outer electrode where they deposit on the inner surface of the electrode. The design and performance evaluation of the ion collector has received little attention in the literature [5e12]. Higher applied voltages (10e150 V) andflow rates (5e15 L/min) were theoretically and experimentally studied by numerous works[5e7,12]. However, a mini-volume electrical PM detector commonly has been operated at volumetric aerosolflow rates lower than 5 L/min and therefore needed a compactable system for afield test and measurement. Therefore, an ion electrostatic collector needs to be designed and numerically and experimentally evaluated for the efficiency of collecting both negative and positive ions at ionflow rates smaller than 5 L/min and collection voltages lower than 50 V. The geom-etry, dimension and size of the ion collector would have influenced to the complexity and expense of the ion collector and then to keepit cost effective.
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