Experimental and simulation‐based investigations on throttle’s head loss coefficients of a surge tank

Abstract

For the different types of throttled surge tanks used in hydropower systems, it is important to comprehensively know the throttle's head loss characteristics for exact surge analysis and transient control. Herein, a general and complete experimental setup was designed to steadily reproduce the 12 typical flow regimes occurring at the surge tank and thus conduct comprehensive experimental research on throttle head loss coefficients. Furthermore, an extended mathematical model for the surge tank was derived by inputting experimental data on the throttle's head loss coefficients to surge analysis. Through experimental research, the throttle's head loss coefficients were determined by fitting formulae relative to the different flow regimes and discharge ratios; via a detailed case analysis, the differences in the head loss characteristics for different throttle types were accurately determined. It was demonstrated that the throttle's head loss coefficient varies with discharge ratio under different flow regimes and found that the experimentally obtained flow coefficients for different throttle types are more accurate and clearly reveal the difference of throttles’ head loss characteristics. The extended mathematical model for the throttled surge tank can provide more accurate simulation results and guidance for its engineering design and layout.

Holistic Design Approach of a Throttled Surge Tank: The Case of Refurbishment of Gondo High-Head Power Plant in Switzerland

“…Such investigation can highlight the variation of the head loss coefficient with the flow share: early studies conducted on T-sections [4,14] have provided experimental evidence that the head loss coefficient of a throttle k or C d value of an orifice is not constant throughout the flow ratio (flow in the branch pipe divided by the flow upstream of the T-section under dividing flow conditions; flow in the branch pipe divided by the flow downstream of the T-section for combining flow conditions). This issue has been also highlighted in a recent study through CFD modeling [15]. However, in the authors' opinion, and based on literature search, the effect of a varying throttle's head loss coefficient with the flow share on the conclusions of a 1D transient analysis has not been investigated so far.…”

Time‐ and frequency‐domain analyses of the hydraulic system using a discrete numerical scheme based on equivalent circuit modelling

“…Numerical simulation has long been recognized as one of the most efficient and economical techniques to predict the dynamic behavior and to reveal the stability of hydraulic systems including the hydraulic structures, 1 the pipelines 2 and the water passages in hydropower plants, 3 and so forth. The common numerical tools for the transient simulation or stability analysis of hydraulic systems can be categorized into frequency‐domain methods and time‐domain methods 4 .…”