Effect of the Connection Types of Air Vessels on the Water Hammer Protection in the Water Delivery Systems

Abstract Air vessels are essential components in long-distance water delivery systems designed to mitigate transient pressure fluctuations. However, oversizing these devices leads to significant installation complexities and high capital costs. This study systematically examines the rational decomposition methodology for an air vessel using comprehensive hydraulic modeling. A long-distance water delivery analysis framework was developed using the method of characteristics, incorporating both air vessel dynamics and pipeline hydraulics. Two distinct connection modes for the air vessel are proposed: both in series and parallel within the main pipe. Through comparative case studies of practical engineering projects, we assessed various decomposition strategies against established protection criteria. The results indicate that: (1) the disassembly of the air vessel must follow this principle: it requires maintaining hydraulic equivalence by preserving the height, initial water–air ratio, and total cross-sectional area, while ensuring that the specifications of the total throttle orifices in the postdisassembly air vessels match those of the predisassembly vessels; (2) when following the principle, the quantity of postdisassembly air vessels and their volume distribution show negligible impact on water hammer protection; and (3) both the connection mode and the distance between air vessels have a slight impact on the protection. This research provides essential guidelines for disassembling the air vessel in water delivery systems and offers theoretical support for engineering applications.