Numerical investigations on cluster characteristics in the supercritical water circulating fluidized bed riser

There are currently no reports about clusters in the supercritical water circulating fluidized bed (SCWCFB). Simulations were conducted to investigate the numbers, diameters, aspect ratios, circularity, and orientation angles of cluster in the riser of SCWCFB via two-fluid model across different flow velocities, solid circulation rates, pressures, and temperatures. The results show that cluster numbers are mainly between 10 and 80 per m². Clusters are more at the bottom but less at the top, and more near the wall but less at the center. Cluster diameters are mainly between 0.2 and 0.5 times the bed diameter. Clusters are large at the bottom but small at the top, and large at the center but small near the wall. Cluster aspect ratios are mainly between 0 and 1, indicating that most clusters have shorter width than their heights. Stream-like clusters are more likely to appear near the walls, and clusters at the center of the riser are more likely to be arch-shaped. Cluster circularity is mainly between 0.2 and 0.4, suggesting that the shapes of clusters are far from the roundness. The absolute values of cluster orientation angles are mainly between 75° and 90°, indicating that most clusters move in the vertical attitudes. High fluid velocities may facilitate cluster coalescence.