Study of the simultaneous effects of secondary flow and sediment erosion in Francis turbines

Abstract

a b s t r a c tSediment erosion of the hydropower turbine components is one of the key challenges due to the constituent of hard particles in the rivers of Himalayas and Andes. In the case of Francis turbines, previous studies show that the erosion is mostly observed around stay vanes, guide vanes and runner blades. Depending upon the type of flow phenomena in particular regions and operating conditions, the sediment particles having certain geometric and material properties create distinct erosion patterns on those regions. The flow phenomena in Francis turbines are highly unsteady, especially around guide vanes and runner. The unsteadiness arises in the form of leakage through clearance gap, horseshoe vortex, rotorstator-interaction and turbulences supported by high velocity and acceleration. The erosion on the other hand deteriorates the surface morphology, aggravating the flow. Based on a thorough literature survey, this paper explains the simultaneous nature of the two effects, which in combined, contributes to more losses, vibrations, fatigue problems and failure of the turbine. It also discusses some of the research endeavors to minimize the combined effect by controlling either the erosion or the secondary flow in the turbine. This review paper emphasizes the need of understanding the relationship between the two phenomena and techniques of how the combined effect can be predicted as well as minimized.

A Review on Sediment Erosion Challenges in Hydraulic Turbines

“…However, due to the circumferential orientation of Figure 11. Cavitation and sediment erosion prone zones in Francis runner [5].…”

“…A detailed investigation of the eroded components of these turbines has shown that turbines erode depending upon the particular types of flow phenomena in particular regions. It has been explained that the secondary flow and sediment erosion in turbines are simultaneous in nature [5], which means that one phenomenon aggravates another. In most of the cases, the condition gets worse because of the cavitation induced after the surfaces are eroded.…”

Correlation Development for Erosive Wear Rate on Pelton Turbine Buckets

“…Because of sediment disintegration stream design changes, loss in effectiveness and vibration delivered, lastly breakdown of hydro turbine happen. Various research have been attempted to foresee the conduct and to decrease the impact of disintegration in hydro turbines, because of sediment [13][14][15][16][17][18][19][20].…”

Erosion Wear on Impeller of Double-Suction Centrifugal Pump due to Sediment Flow

“…However, due to the complexity of the structure of the double-suction centrifugal pump, the quantitative correlation of the mechanism of impeller blade wear is lack of systematic research. The morphology observation experiment method can locate the erosion wear form and damage degree of the blade surfaces after running for a period of time (Serrano et al 2018;Chitrakar et al 2016). Additionally, to optimize the design of doublesuction impeller and the pumping system, it is important to consider the influence of particles on the trajectories in the computational domain and identify the location and erosion rate density distribution on the impeller blades for sediment flows in pumps.…”