Numerical estimation of prototype hydraulic efficiency in a low head power station based on gross head conditions

摘要

Low-head hydraulic power units typically have a short intake pipe or no that structure. For this reason, the upstream and downstream flows in reservoirs could influence the internal flow characteristics in the turbine, which sometimes increase the flow non-uniformity and the local hydraulic losses. Meanwhile, the efficiency estimation methods for prototype turbines still have a limitation for determining the unit discharge, which is generally predicted by using a Winter-Kennedy method. This paper proposes a hydraulic performance estimating method focusing on low-head turbine units, which is conducted by using CFD analysis and based on site test results. A bulb type turbine unit was adopted as a research object, which is operating in a low-head run-of-the-river power station. The flow behaviors in turbine were simulated based on two water levels under single unit operation, with two reservoir modeling. The simulation results agreed well with test ones for the turbine power as well as the relative discharge curve. The prototype efficiency in operation was estimated at the same time. In addition, this paper analyzed the relationship between the gross head and net head, and introduced the concept of plant hydraulic efficiency, as regards the flow interaction between the turbine unit, intake and tailrace. (c) 2020 Elsevier Ltd. All rights reserved.