Bryan John Lewis

Major historical developments in the design of water wheels and Francis hydroturbines

The first record of water wheels dates back to ancient Greece. Over the next several centuries the technology spread all over the world. The process of arriving at the design of the modern Francis runner lasted from 1848 to approximately 1920. Though the modern Francis runner has little resemblance to the original turbines designed by James B. Francis in 1848, it became know as the Francis turbine around 1920, in honor of his many contributions to hydraulic engineering analysis and design. The modern Francis turbine is the most widely used turbine design today, particularly for medium head and large flow rate situations, and can achieve over 95% efficiency.

Wicket gate trailing-edge blowing: A method for improving off-design hydroturbine performance by adjusting the runner inlet swirl angle

At their best efficiency point (BEP), hydroturbines operate at very high efficiency. However, with the ever-increasing penetration of alternative electricity generation, it has become common to operate hydroturbines at off-design conditions in order to maintain stability in the electric power grid. This paper demonstrates a method for improving hydroturbine performance during off-design operation by injecting water through slots at the trailing edges of the wicket gates. The injected water causes a change in bulk flow direction at the inlet of the runner. This change in flow angle from the wicket gate trailing-edge jets provides the capability of independently varying the flow rate and swirl angle through the runner, which in current designs are both determined by the wicket gate opening angle. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation.

Unsteady Computational Fluid Dynamic Analysis of the Behavior of Guide Vane Trailing‐Edge Injection and Its Effects on Downstream Rotor Performance in a Francis Hydroturbine

A unique guide vane design, which includes trailing-edge jets, is presented for a mixed-flow Francis hydroturbine. The water injection causes a change in bulk flow direction at the inlet of the rotor. When properly tuned, altering the flow angle results in a significant improvement in turbine efficiency during off-design operation. Unsteady CFD simulations show nearly 1% improvement in overall turbine efficiency with the use of injection. This revolutionary concept also has the ability to reduce the intensity of the rotor–stator interactions (RSI) by compensating for the momentum deficit of the wicket gate wakes. This technology may be equally applied to other turbomachinery devices with problematic rotor–stator flow misalignments.