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Alden Research Laboratory, Inc. (ARL,) and Northern Research and Engineering Corporation (NREC) conducted a research program to develop a turbine runner which will minimize fish injury and mortality at hydroelectric projects. ARL/NREC have developed a runner shape which minimizes the number of blade leading edges, reduces the pressure versus time and the velocity versus distance gradients within the runner, minimizes or eliminates the clearance between the runner and runner housing, and maximizes the size of the flow passages, all with minimal penalty on turbine efficiency.An existing pump impeller provided the starting point for developing the fish tolerant turbine runner. The Hidrostal pump is a single bladed combined screw/centrifugal pump which has been proven to transport fish with minimal injury. The focus of the ARLNREC research project was to develop a new runner geometry which is effective in downstream fish passage and hydroelectric power generation. A flow of 1,000 cfs and a head in the range of 75 ft to 100 ft were selected for conceptual design of the new runner.Conceptual design of the new runner began with a re-evaluation of studies which have been previously conducted to identifj probable sources of injury to fish passing through hydraulic turbines. Criteria relative to hydraulic characteristics which are favorable for fish passage were prepared based on a reassessment of the available information. Important criteria used to develop the new runner design included low pressure change rates, minimum absolute pressures, and minimum shear. Other criteria which are reflected in the runner design are a minimum number of blades (only two), mimimum total length of leading edges, and large flow passages.Flow characteristics of the new runner were analysed using two-dimensional and three-dimensional Computational Fluid Dynamic (CFD) models. The basic runner geometry was initially selected using the two-dimensional model. The three-dimensional model was used to investigate the flow characteristics in detail through the entire runner and to refine the design by eliminating potential problem areas at the leading and trailing edges. Results of the analyses indicated that the runner has characteristics which should provide safe fish passage with an overall power efficiency of approximately 90%.The size of the new runner, which is larger than conventional turbine runners with the same design flow and head, will provide engineering, fabrication, and installation challenges related to the turbine components and the civil works. A small reduction in the overall efficiency would reduce the size of the runner considerably, would simpliQ the turbine manufacturing operations, and would allow installation of the new turbine at more hydroelectric sites.

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