SHADOW DOPPLER VELOCIMETRY FOR SIMULTANEOUS SIZE AND VELOCITY-MEASUREMENTS OF IRREGULAR PARTICLES IN CONFINED REACTING FLOWS

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, 10kW vertically-fired atmospheric model of the pressurised poulverised -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 th at it is tolerant of the optical misalignment and fouling which are in evitable when passing laser beams through windows in such furnaces. Th e size and two components of velocity of burning coal particles were m easured in the present geometry which has 172mm furnace diameter and 4 0 mm lateral exit duct diameter and a calculated exit bulk velocity of 4 m/s, evaluated at 300K. The Sauter mean diameter of the particles i s, within the experimental error, uniform at about 40 mu m in the vert ical profile normal to the axis of the exhaust pipe, 34.5mm upstream o f the exit. Coal particle velocities in the near-exit region are direc ted towards the exit, closely following the gas-phase velocities. Both these observations imply that particle retention efficiency due to st reamline curvature is low and extrapolation suggests that there will b e even less at large scales.