ANALYSIS OF THE IMPACT OF VALVE CHARACTERISTIC CURVE ON WATER HAMMER

There are various causes of water hammer, one of which is the control valve, a component found in most hydraulic systems. This paper examines the impact of inherent and installed control valve characteristics on hydraulic transient regimes. It is well known that guide vanes or nozzles are the primary flow control devices for hydro turbines, while the main turbine inlet valves are the secondary devices, and one of their tasks is to interrupt water supply to the turbine in case of failure of the primary regulators. Three typical inherent valve characteristic curves were selected and their installed characteristics were determined for two derivation pipeline diameters, after which three valve closure times were analyzed, starting from the nominal operating regime. Numerical analyses of unsteady flow regimes are used to obtain pressure distributions and max/min pressure envelopes during water hammer. In order to improve the system's characteristics in unsteady flow regimes, variable speed actuators were analyzed, new valve closing laws were designed, and possible performance improvements were quantified and proposed for practical engineering applications.