The energy release from an aluminum dust explosion is related to the degree of turbulence and the local concentration distribution at a given nominal concentration. In the present work the combined effects of turbulence and concentration on aluminum dust/air explosions in a 20 L spherical test vessel were examined using ultrasonic sensors. The relationship between the dust concentration and the ultrasonic attenuation coefficient was established, and real-time online measurements of aluminum dust concentrations were performed. The data show that the turbulent kinetic energy increases sharply during the initial stage of injection and then decreases gradually over time, while the concentration and uniformity of suspended dust gradually increase as the turbulence decreases. Explosion energy data were obtained at various dust concentrations and demonstrate that concentrations from 700 to 900 g/m(3) are optimal. (C) 2020 Elsevier B.V. All rights reserved.