Abstract
Hydraulic turbines are usually required to operate in a wide range. The operation at off-design conditions not only reduces the unit efficiency, but also significantly deteriorates the dynamic stability of the turbines. In order to develop a turbine runner with good performances under multi operation conditions, a comprehensive hydraulic improvement has been done of a Francis turbine runner with a multipoint and multi-objective optimization design system. Compared with the initial runner, the runner generated from this method has a satisfactory improvement. In detail, unit efficiencies of the preferred runner are increased by 0.91%, 0.47% and 0.37%, respectively, under the rated head, a high head and the maximum head. The lowest pressure at blade surface is improved by 376.2 kPa under the rated head. CFD calculations are conducted to analyze the flow conditions inside of the preferred runner. In addition, runners with different main design inputs, namely blade lean, blade loading and blade meridional shape are furtherly investigated to reveal their relationship with runner’s internal flow and outer performances. In summary, this optimization system supplies satisfactory results and convincing recommendations to determine the design inputs for low-head Francis turbine runners.
Highlights
Hydropower is known as a well-developed and cost-competitive renewable energy technology.In line with the current energy development, i.e., growing proportion of photovoltaic and wind power, hydropower is assumed to become increasingly important
The efficiency is reduced because the hydraulic losses become higher, and the dynamic stability of the turbines is weakened significantly [4], it is necessary for the design strategies to be improved to satisfy the new requirements
With the increasing unit efficiency η, the minimum pressure pmin on the blade surface decreases, which means increasing unit efficiency η, the minimum pressure pmin on the blade surface decreases, which means that the cavitation performance deteriorates
Summary
In line with the current energy development, i.e., growing proportion of photovoltaic and wind power, hydropower is assumed to become increasingly important. On one hand, it produces renewable energy, on the other hand, it is utilized to satisfy the energy storage requirements associated to the new renewable energy sources [1,2]. Hydraulic the turbines, responding to fast and elastic grid fluctuations, are often forced to operate under the off-design conditions. In such conditions, the efficiency is reduced because the hydraulic losses become higher, and the dynamic stability of the turbines is weakened significantly [4], it is necessary for the design strategies to be improved to satisfy the new requirements
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