Spark Breakdown of Particulate Clouds: A New Testing Device

A uniform cloud of particles is generated electrostatically between parallel plates of a capacitor. The particulate cloud is then triggered for spark breakdown by a high-speed injected needle electrode. The relevant characteristic times of the spark (first and second spark pulse times and time to ignition) are compared with event times associated with needle penetration and residence times and particle collision time to infer cloud disturbance effects caused by the needle. Both open (with particle diffusion) and closed systems of cloud confinement are discussed. The advantages of this electrostatically controlled sparking system include the uniformity of the clouds produced and the ease of measurement of the particle number density. Applications of this method are spark breakdown and ignition testing of inert or combustible particle and gas mixtures.