(633f) A New View of Riser Flow Fields Using High Speed Particle Imaging Velocimetry (PIV)

A new high speed particle image velocimetry (HSPIV) system developed at the NETL is providing new visualization and measurement of particle motion in particle flows of high particle concentration. The HSPIV system has adequate spatial resolution (1280 x 800 pixel x 4096 grey levels) and temporal resolution (frame rates up to 7000 per second at maximum pixel resolution and up to 500,000 per second at lower resolutions) to resolve the fastest temporal scales and shortest spatial scales of the particle flow fields up to 100 m/s. The HSPIV system measures particle velocities with uncertanties less than + 1%. The HSPIV system has been applied to experimental risers at USDOE NETL and PSRI with riser diameters from 0.2 m (8?) to 0.3 m (12?) and heights up to 21 m (70 ft). Visualization of flow field behavior and simultaneous measurements of particle velocity and concentration with the HSPIV system are revealing that riser flow fields do not exhibit steady core-annulus behavior consisting of a single high-speed jet ?core? of low particle concentration surrounded by a low velocity, high concentration ?annulus.? Rather, riser flow fields are highly unsteady and, under all riser conditions studied, consist of one or more high speed ?jets? of low particle concentration. The high speed jets are unsteady and appear to move around the riser, flowing against the riser wall at one location then moving to another. When a high speed jet moves away from an area, the area is immediately filled with high concentrations of particles at low velocities, usually in the form of large clusters. Analysis of the correlation between time series data for particle velocity and relative particle concentration clearly shows the existence of high speed, low concentration jets. Frequency analysis of the velocity time series indicates that the high speed jets flow against a measurement location in the riser at a frequency in the range of 0.1 to 5 Hz. This HSPIV data is being used to improve existing CFD models and develop new CFD models of riser flow fields.