Application of a pitometer to measure the tangential velocity in a cylindrical through-flow hydrocyclone operated with a fiber suspension

摘要

This investigation evaluates a novel fluid velocity measurement method to measure the tangential velocity in a hydrocyclone. The hydrocyclone was operated with an opaque fiber suspension in order to investigate the influence of fiber presence on the tangential velocity distribution. The tangential velocity was measured with a one-hole pitometer, 0.9 mm in diameter, that was equipped with a micro pressure transducer. The pitometer was kept clean with a continuous purge flow. The probe was tested in a cylindrical through-flow hydrocyclone operated with water and 0.4 g/l and 0.8 g/l (0 %, 0.04 % and 0.08 %) addition of a bleached softwood kraft pulp. The velocity profiles measured in pure water agreed qualitatively with velocity distributions that are found in the literature. The outer section had a free vortex-like distribution and the inner section had a solid body rotation. The addition of small amounts of fibers changed the tangential velocity profile significantly. The radius of solid body rotation increased, the maximum tangential velocity decreased and the transition from solid body rotation to free vortex rotation was smoothened.