Editor’s Note: This is the latest in a series of profiles provided by the Hydro Research Foundation that highlight potential future members of the hydroelectric power industry and their accomplishments.
The Hydro Research Foundation is actively supporting graduate students to conduct research related to conventional and pumped storage hydropower. These students are funded through the Department of Energy’s Water Power Program and industry partners through a two-year, $1 million grant.
Matthew Erdman will graduate later this summer from Penn State with a master’s in mechanical engineering.
Matt’s research focused on Modifications to the Runner Blade to Improve Off-Design Efficiencies in Hydraulic Turbines. He is actively seeking employment in the hydro industry.
There are numerous reasons that a hydraulic turbine may be run at conditions differing from its design point (the best efficiency point). When operated at these partial load conditions, the draft tube can have large amounts of residual swirl. This residual swirl has been linked to the formation of helical vortexes more commonly known as “vortex rope.”
The vortex rope is now known to be a significant contributor in the instabilities and as well as loss of efficiency that results during operation at off-design conditions. The residual swirl causes a significant head loss that is specifically relevant in reaction turbines (such as Francis turbines) which draw power directly from the pressure head.
It has recently been shown numerically that water jets on the trailing end of wicket gates can improve off-design efficiencies. This patented modification serves to improve the angle of attack of the fluid on the runner blades. The research project will investigate and determine if similar modifications to the runners themselves could limit or eliminate the residual swirl entering the draft tube when the turbine is operating at off-design conditions.
The research will numerically model, modify and analyze runner blades of the GAMM Francis turbine. ANSYS DesignModeler will be used for mesh generation, and ANSYS-FLUENT will the primary CFD solver. Analysis will primarily be done on a single runner with periodic boundary conditions. Experimental data provides boundary conditions directly at the entrance and exit of the runners.
These results will be extrapolated in both the upstream and downstream directions so that a full volume may be analyzed. Once a working model has been developed, the trailing end of the runner will be modified with a water jet with the goal of changing the residual swirl. After the residual swirl has been effectively changed using the water jet, a detailed analysis will be completed to determine if the residual swirl could be limited sufficiently to provide a noticeable increase of efficiency. The required power and size of the water jets under differing operating conditions will be determined.