Velocity Measurements on Isothermal Sudden Expanding Swirling Flow in an Industrial Burner With Bluff-Body

This paper describes two-dimensional back-scatter laser-Doppler anemometer mesurements in confined isothermal and nonreactiog sudden expanding swirling air flow. A swirling air flow, with an inlet swirl number of 2.0 is generated by an axial vane swirl generator. The swirling f1ow enters a 0.4 m diameter, 4 m long cylindrical chamber via a sudden expansion quarrel. The confine ratio equals to 2.1. The blockage ratio of the bluff-body equals to 0.5. The Reynolds number of the air is 5.0 x 10^4. Simultaneously axial and · azimuthal, mean and fluctuating velocity measurements were made by using laser-Doppler anemometer (LOA) system. It is found that the maximum reverse-flow rate occurs at about 0.50 furnace diameter with 60% of the inlet mass flow recirculated. Some quantitative information, such as the size, shape and the intensity of the central recirculation zone, axial distribution of energy flux were provided.