Cavitation Characteristics of S-Blade Used in Fully Reversible Pump-Turbine

Abstract

S-shaped blade profiles with double camber find use in fully reversible turbomachines that can extract power from tides. Though noncavitating characteristics of S-blades were determined in the past, yet characterizing cavitating flow was not carried out. This work, which is the first step in this direction, uses a two-pronged approach of experimental and numerical characterization of cavitating flow past these hydrofoils. Experimental results indicate that as the angle of attack increases in either positive or negative directions, cavitation inception number increases. Minimum cavitation effect is observed at 2 deg, which is zero lift angle of attack. For higher angles of attack (±6deg, ±4deg) and moderate or low cavitation number (σ/σi≤0.3), unsteady cloud cavitation was characterized through visual observation and from pressure fluctuation data. It was observed that for unsteady cavity shedding to take place is the length and thickness of the cavity should be more than 50% and 10% of the chord length, respectively. Predicting flow past this geometry is difficult and the problem may be compounded in many applications because of laminar-to-turbulence transition as well as due to the presence of cavitation. Present simulations indicate that the k-kL-ω transition model may be useful in predicting hydrodynamic performance of this type of geometry and for the range of Reynolds number considered in this paper. Hydrodynamic performance under cavitation indicates that pumping mode is more adversely affected by cavitation and, hence, a fully reversible turbomachine may not perform equally well in turbine and pump modes as expected from noncavitating results.

Numerical and experimental investigation on the development of cavitation in a centrifugal pump

“…For the purpose, various kinds of methods have been adopted to research the development of cavitation in hydraulic machineries, including numerical simulations and experimental investigations. [2][3][4][5][6][7][8] With the development of cavitation, Tsujimoto et al divided the process of cavitation into cavitation surge, rotating cavitation, and asymmetric cavitation, and explained the mechanisms of the phenomenon, as well as the characteristics of those instabilities caused by cavitation, based on two-dimensional stability analyses. [9][10][11] The most common method used to identify the presence of cavitation was based on the observations of the drop in head and 3% head drop from noncavitation was regarded as the critical cavitation.…”

“…For the purpose, various kinds of methods have been adopted to research the development of cavitation in hydraulic machineries, including numerical simulations and experimental investigations. 2–8…”

Dynamic analysis of a pumped-storage hydropower plant with random power load

“…In practical situations, it is difficult to regulate and control perfectly the dynamic characteristics of the PSHP because of the random power load [21][22][23][24][25]. In addition, the lack of the accurate model of the PSHP and the qualitative analysis of control parameters also make it hard to ensure the stable operation of the PSHP [26][27][28].…”

Fluid flow analysis of drooping phenomena in pump mode for a given guide vane setting of a pump-turbine model

“…Yin et al (2010) also carried out some similar work to predict the performance and flow pattern of a pump-turbine in pump mode, but this analysis was undertaken just in the vaned distributor at low flow rate. Other cavitation studies related to a pumpturbine in pump mode (Liu et al, 2013;Premkumar et al, 2014) investigated the relation between cavitation and pump mode.…”