Effect of Air Vessel Configuration on Transient Pressure

Hydropneumatic tanks can effectively safeguard pressurized systems from water hammer. In this paper, the influences of the air vessel aspect ratio (R = height/diameter) and its form, whether cylindrical (vertical or horizontal) or spherical, on the transient pressures resulting from abnormal working events of pumps are examined. The primary objectives of this study are to identify the best vessel shape and to determine the optimal value of R while minimizing water hammer effects. The Bentley HAMMER software, which uses the method of characteristics to solve momentum and continuity equations for unsteady flow, is initially verified and subsequently utilized in this analysis. Three case studies are considered. The results show that under the same operating conditions, R insignificantly affects the maximum and minimum pressures. In addition, as R increases, the extreme pressure improves slightly. Furthermore, the hydraulic performances of cylindrical (whether horizontal or vertical) and spherical air vessels under transient conditions at the same volume are identical, and the small differences in the transient results can be attributed to the changing pressures of air/gas inside the vessel resulting from the variations in the cross-sectional area of the vessel.