Hydrodynamic regimes and characteristics of air-sand flow were studied in a cone-shape swirling fluidized bed for two types of air entry, or swirl generator: through a four-nozzle system (tangential entry) and using an annular-spiral airdistributor (axial entry). Quartz sand of four particle sizes, 180-300, 300-500, 500-600 and 850-1180 mu m, was used as the bed material in experimental tests on a cold model of a conical swirling fluidized bed combustor. During each test run, the pressure drop across the bed (Delta p) was measured versus superficial velocity at the lower bed basis (u) for three static bed heights (20,30 and 40 cm). Four regimes were found in the bed behavior for both swirl generators. The Delta p-u diagrams were compared between tangential and axial airentries for different operating conditions. Mathematical models for predicting major hydrodynamic characteristics, the minimum fluidization velocity (u(mf)) and corresponding pressure drop across the bed (Delta p(mf)), were empirically developed. The dimensionless dependency of Delta p/Delta p(mf) on u/u(mf) showed the apparent common trends and similarity for most of the test trials. For the two air injection systems, a Nomograph for assessment of Delta p at any arbitrary superficial velocity and bed height was proposed as well. (C) 2009 Elsevier Ltd. All rights reserved.