Experimental Analysis of Cavitation Phenomena on Kaplan Turbine Blades Using Flow Visualization

Abstract

In this study, a comparison of two different Kaplan turbine runners with differently shaped turbine blades was performed. The two turbines differed in the selection of the hydrofoil, the main hydrofoil parameters of which had been modified including, the position of maximum thickness and curvature and the inlet edge radius. Both turbines (unmodified and modified hydrofoils) were tested on a rig designed for low pressure model turbine acceptance tests. The effect of blade shape on cavitation inception, development, and intensity was demonstrated using computer aided visualization. Visualization was performed on the suction side of Kaplan runner blade where the shape of the blade determines cavitation inception and development. The modified Kaplan turbine reduced the cavitation phenomena, and as a result, both turbine performance and output increased for the selected operating points. This demonstrates that choosing the right turbine blade shape is key for optimal turbine performance.

Analysis of Bulb Turbine Hydrofoil Cavitation

“…The unmodified hydrofoil in a region from the leading edge to the location of the maximum thickness is very sensitive to the optimum angle of attack due to its sharp leading edge. Away from the optimum attack angle, the unmodified hydrofoil has disadvantageous cavitation characteristics in comparison with the modified one [6]. Contemporary water turbines often operate away from the best efficiency points due to the introduction of renewable energy sources and environmental changes.…”

“…Although all hydraulic turbine types are constantly improved, the gains in efficiency are in the per mille range and the cavitation in hydraulic turbines remains an In this study, we focus on a range of volumetric flows, which appear on a bulb turbine at a 25° blade angle (Figure 2). Here cavitation frequently occurs at approximately 15% higher volumetric flows than at the best efficiency point [6]. The 25° blade angle was chosen because it lies in the middle of the angle interval usually agreed between the producers and customers of bulb turbines.…”

“…The situation in the bulb turbines is therefore very complex and the flow properties around individual hydrofoils cannot be directly correlated around the bulb turbine runner blades. Nevertheless, we will assume [6] that bulb runner cavitation can be related to the cavitation analysis of a single hydrofoil in the water tunnel.…”

Study of Turbulence Model for Performance and Flow Field Prediction of Pico Hydro Types Propeller Turbine

“…Byeon and Kim [11] explained that propeller turbine with 4 number of blades is more effective than 3 and 5 number of blades. Podnar et al, [12] compared two different hydrofoils and proposed a method to determine cavitation in propeller turbine using computer aided visualization. In addition, Podnar et al, [12] suggest to be more selective in determining blade profile, because it affects the formation of cavitation (reducing efficiency).…”

“…Podnar et al, [12] compared two different hydrofoils and proposed a method to determine cavitation in propeller turbine using computer aided visualization. In addition, Podnar et al, [12] suggest to be more selective in determining blade profile, because it affects the formation of cavitation (reducing efficiency). Simpson and Williamson [13] developed the manufacture method of pico scale hydropower propeller turbine for remote areas.…”