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Energies 2017, 10(6), 787; doi:10.3390/en10060787

Optimization of the Runner for Extremely Low Head Bidirectional Tidal Bulb Turbine

1
State Key Laboratory of Hydroscience and Engineering & Department of Thermal Engineering, Tsinghua University, Beijing 100084, China
2
Huaneng Clean Energy Research Institute, Beijing 102209, China
3
China Water Resources Beifang Investigation, Design & Research CO. LTD, Tianjin 300222, China
*
Author to whom correspondence should be addressed.
Academic Editor: Aristides Kiprakis
Received: 28 March 2017 / Revised: 19 May 2017 / Accepted: 2 June 2017 / Published: 7 June 2017
(This article belongs to the Special Issue Marine Energy)
View Full-Text   |   Download PDF [5013 KB, uploaded 7 June 2017]   |  

Abstract

This paper presents a multi-objective optimization procedure for bidirectional bulb turbine runners which is completed using ANSYS Workbench. The optimization procedure is able to check many more geometries with less manual work. In the procedure, the initial blade shape is parameterized, the inlet and outlet angles (β1, β2), as well as the starting and ending wrap angles (θ1, θ2) for the five sections of the blade profile, are selected as design variables, and the optimization target is set to obtain the maximum of the overall efficiency for the ebb and flood turbine modes. For the flow analysis, the ANSYS CFX code, with a SST (Shear Stress Transport) k-ω turbulence model, has been used to evaluate the efficiency of the turbine. An efficient response surface model relating the design parameters and the objective functions is obtained. The optimization strategy was used to optimize a model bulb turbine runner. Model tests were carried out to validate the final designs and the design procedure. For the four-bladed turbine, the efficiency improvement is 5.5% in the ebb operation direction, and 2.9% in the flood operation direction, as well as 4.3% and 4.5% for the three-bladed turbine. Numerical simulations were then performed to analyze the pressure pulsation in the pressure and suction sides of the blade for the prototype turbine with optimal four-bladed and three-bladed runners. The results show that the runner rotational frequency (fn) is the dominant frequency of the pressure pulsations in the blades for ebb and flood turbine modes, and the gravitational effect, rather than rotor-stator interaction (RSI), plays an important role in a low head horizontal axial turbine. The amplitudes of the pressure pulsations on the blade side facing the guide vanes varies little with the water head. However, the amplitudes of the pressure pulsations on the blade side facing the diffusion tube linearly increase with the water head. These results could provide valuable insight for reducing the pressure amplitudes in the bidirectional bulb turbine. View Full-Text
Keywords: tidal energy; numerical simulation; optimization; bidirectional; bulb turbine tidal energy; numerical simulation; optimization; bidirectional; bulb turbine
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MDPI and ACS Style

Luo, Y.; Liu, X.; Wang, Z.; Xiao, Y.; He, C.; Zhang, Y. Optimization of the Runner for Extremely Low Head Bidirectional Tidal Bulb Turbine. Energies 2017, 10, 787.

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