Experimental Study of Transient Flow Regimes in a Model Hydroturbine Draft Tube

Abstract

Swirling flow with the formation of a precessing vortex core (PVC) in the draft tube model of a hydroturbine was studied. Experiments were performed on an aerodynamic setup under transient operating conditions of the hydroturbine. The turbine operating conditions were varied by continuously changing the flow rate at a constant runner speed. The transition from the partial load regime, when a precessing vortex core is formed, to the best efficiency point without a core is considered. Applied to this task, a comparison of the windowed Fourier transform with wavelet analysis is given. The dependence of the PVC lifetime in the transient regime correlates with the transient time. It is shown that the velocity profiles and the spectrum of pressure pulsations in transient regimes change quasistatically between part-load operation and the best efficiency point of the turbine. The phase-averaged velocity distributions in the transient regimes show that a transient regime is a sequence of quasisteady regimes.

Large-eddy simulations of a swirling flow in a model Francis turbine

“…Moving away from the optimal efficiency regime by decreasing the volumetric flow rate the size of this stagnant region increases [3] and may get to the runner area. Recent investigations are directed towards PVC suppressing in stationary [4] and transient flow regimes [5]. It is required to thoroughly investigate low-load flow regimes in the Francis turbine before expanding the range of permissible operating modes of hydraulic turbines by applying control techniques to suppress the PVC in the future.…”

Laboratory Modeling of an Axial Flow Micro Hydraulic Turbine

“…The experiments were carried out employing an automated experimental setup with air used as a working medium. This significantly reduced the difficulties in manufacturing experimental sections (problems with sealing joints, structural strength, and providing optical access) [24]. As shown in the technical reports [25,26] from the USBR group in the USA and in the USSR energy community handbook [27], results obtained with air and water test sections showed satisfactory correlation.…”

“…The cone length is H = 280 mm, the cone angle is 4 • . and providing optical access) [24]. As shown in the technical reports [25,26] from the USBR group in the USA and in the USSR energy community handbook [27], results obtained with air and water test sections showed satisfactory correlation.…”

Cavitation Noise Signal Classification of Hydroturbine Based on Improved Multi-Scale Symbol Dynamic Entropy

“…1 Hydroturbine is the key equipment of hydropower unit, and its health condition will directly affect the operation of the whole turbine system, so that it has become the key factor of the periodic overhaul of hydropower station. 2 Over the past years, the catastrophic accidents have happened in power industry around the world caused by the failure of key equipment. 3 Therefore, how to use the correct monitoring technology to ensure the safe and efficient operation of power equipment, prevent the failure of key equipment, and avoid the occurrence of major accidents have become one of the most important research topics in the power industry.…”