Benefits of air admission systems for the flexible operation of Francis runners

In addressing increased demand for flexible operation, Francis runners are exposed to various operating conditions beyond their traditional operating range. In response to these hydraulic and structural requirements, equipment needs to be designed for long-time, part-load operation. In this paper, the benefits of flexible runners are discussed, and different uses and possible business cases are reported. Air admission systems are one solution to the new operating condition demands experienced during part load for both existing and new designs. The options for, and characteristics of, different air admission systems are discussed.