Shadow Doppler Velocimetry for Simultaneous Size and Velocity Measurements of Irregular Particles in Confined Reacting Flows

Abstract

We report the application of the Shadow Doppler Velocimeter (SDV) for spatial precise, simultaneous measurement of the size and velocity to assess the particle retention performance of a laboratory, 1/6 scale, 10 kW vertically‐fired atmospheric model of the pressurised pulverised‐coal furnace of Reichert et al. [1]. The SDV is based on the imaging of a conventional LDV probe volume onto a linear photodiode array and has the advantage over other sizing methods for irregular particles that it is tolerant of the optical misalignment and fouling which are inevitable when passing laser beams through windows in such furnaces. The size and two components of velocity of burning coal particles were measured in the present geometry which has 172 mm furnace diameter and 40 mm lateral exit duct diameter and a calculated exit bulk velocity of 4 m/s, evaluated at 300 K. The Sauter mean diameter of the particles is, within the experimental error, uniform at about 40 μm in the vertical profile normal to the axis of the exhaust pipe, 34.5 mm upstream of the exit. Coal particle velocities in the near‐exit region are directed towards the exit, closely following the gas‐phase velocities. Both these observations imply that particle retention efficiency due to streamline curvature is low and extrapolation suggests that there will be even less at large scales.

Application of Optical Diagnostics Techniques to a Laboratory-Scale Turbulent Pulverized Coal Flame

“…The new aspect of this instrumentation is that the shape of the particles is obtained from the temporal output from elements of a linear photodiode array positioned at the focal plane of the collection optics of LDV to record the shadow of the passage of the particle. The detailed measurement principle is described in refs and . The shape and two components of velocity of burning pulverized coal particles are measured in the turbulent pulverized coal flame.…”

“…However, the application is limited to spherical particles. Hardalupas et al and Maeda et al developed shadow Doppler particle analyzer (SDPA) by extending the LDV system as a method for simultaneous measuring of velocity and particle shape of nonspherical particles such as pulverized coal. The SDPA has the advantage over other sizing methods for irregular particles in that it is tolerant of the optical misalignment and fouling which are inevitable when passing laser beams through optical access windows in a confined flame measurement .…”

Application of shadow Doppler velocimetry to paint spray: potential and limitations in sizing optically inhomogeneous droplets

“…For an optically inhomogeneous but strongly absorbing medium, SDV operates well, as demonstrated by Morikita et al (1995) and Maeda et al (1997), if the flow of particles is dilute. However, it has not been used for spray measurement and its limitations are not known.…”

James Hunter Whitelaw. 28 January 1936 — 16 August 2006

“…In parallel with the above, the pressing need for a reduction in the NO x from coal-fired burners led Whitelaw and Taylor to explore the particle dynamics of pulverized fuel in smallscale model burners. It quickly became evident that a different sizing technique would be needed for the irregular coal particles and this led, through their collaboration with a group at Keio University in Japan, to the development of the shadow-Doppler anemometer (20,22).…”

“…It quickly became evident that a different sizing technique would be needed for the irregular coal particles and this led, through their collaboration with a group at Keio University in Japan, to the development of the shadow-Doppler anemometer (20,22).…”