Abstract
Hydraulic instability is a complex factor causing the vibration of hydro-turbine generator shafting system (HGSS), and the mechanism is the uneven distribution of flow along the circumference. The common reasons for this phenomenon include the inconsistency of the blade exit flow angle, the relay stroke and the guide vane opening. This paper mainly focuses on the research of the hydraulic instability caused by the inconsistency of the blade exit flow angle. Firstly, based on the Kutta-Joukowski theorem, the hydraulic unbalance force model is firstly presented. Then, considering the chain reaction among the hydraulic, mechanical and electrical instability, a combined nonlinear mathematical model of the HGSS is established. Finally, by using numerical simulation, the dynamic characteristics of the HGSS with the changing of the deviation of the blade exit flow angle, the blade exit diameter and the guide vane opening angle are analyzed. Moreover, it is found that the hydraulic instability determines the overall changing trend of the shafting dynamic behaviors. In addition, some stable ranges of the HGSS are distinguished. But above all, these results can efficiently provide a reference for the design and manufacture of hydro-turbine blades and the operation of hydropower stations.
Highlights
Hydraulic power as a kind of renewable, clean and economical energy has been well developed worldwide [1,2,3]
Paish [1] illustrated that hydraulic power on a small scale, or micro-hydro, is one of the most cost-effective energy technologies to be considered as the main prospect for future hydro developments in Europe due to micro-hydro being one of the most environmentally benign energy technologies available
Modesto et al [3] presented the state of the art of hydraulic power generation in drinking and irrigation water networks through an extensive review and how hydraulic power can be applied in water distribution networks where energy recovery is not the main objective
Summary
Hydraulic power as a kind of renewable, clean and economical energy has been well developed worldwide [1,2,3]. Energies 2018, 11, 2862 example, in the end of 2015, the installed capacity of the hydropower stations has reached 320.03 GW These changes will bring an increasing possibility of unstable vibration of the hydro-turbine generator shafting system (HGSS) caused by hydraulic, mechanical and electrical instability [15,16,17,18,19]. In order to investigate the effects of electrical and mechanical unstable factors, scholars have proposed a large amount of nonlinear mathematical models [20,21,22,23,24,25,26,27,28,29,30,31].
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