### Tech Briefs

Analysis of a Hydraulic Turbine

Much effort is being made to develop efficient and cost-effective renewable energy solutions (see Ref.). In conventional hydropower, as well as in the more recent quest to harness the energy from waves and tides, well designed turbomachinery is essential. We feature the analysis of a new hydraulic turbine design to power a generator providing between 1.0 and 1.2 kW for remote dwellings not connected to an electrical supply grid. The analysis was performed by SIM&TEC S.A. using ADINA.

In the analysis, the turbine was modeled to determine its characteristic curves of torque and power vs. rotational speed. The figures are provided to give an idea of the general trend of the results, but do not include numerical data due to client confidentiality requirements. The movie above shows the calculated flow through the rotating turbine.

Figure 1 shows the geometry of the turbine. The finite element mesh used is shown in Figures 2 and 3.

Figure 1 Schematic of the turbine, two views

Figure 2 Finite element model used: fixed and rotating fluid mesh

Figure 3 Finite element model used: turbine

In the fluid model, a rotating mesh (shown in red in Figure 2) attached to the blades was defined and a separate fixed mesh (green in Figure 2) was also defined, with a sliding surface between these two meshes. The rotating turbine is shown in the movie above.

Band plots from the analysis results are shown in Figures 4 to 6.

Figure 5 Relative tangential velocity band plot

Figure 6 Turbulence intensity band plot

To investigate the effect of river flow turbulence on the results, different values of free flow turbulence intensity (It) were considered. The numerical results were obtained modeling the flow with two different turbulence models: the standard k-ε model and the SST (Shear Stress Transport) model that combines the k-ε model in the free flow and the k-ω model close to the walls. As shown in the Figures 7 to 9, both sets of results are almost coincident.

Figure 7 Turbine power vs. rotational speed for different values of turbulence intensity (It) in the entry flow

Figure 8 Turbine torque vs. rotational speed for different values of turbulence intensity (It) in the entry flow

Figure 9 Turbine power coefficient for different values of turbulence intensity (It) in the entry flow

The powerful modeling capabilities available when using ADINA in CFD and FSI make ADINA the preferred analysis tool for a wide range of industrial problems in these areas.

Reference

• C. Deilmann & K.J. Bathe, "A holistic method to design an optimized energy scenario and quantitatively evaluate promising technologies for implementation", International Journal of Green Energy, 6:1-21, 2009.

Keywords:
Turbine, rotating mesh, turbulence, k-ε model, k-ω model, SST model, CFD, green power, turbomachinery

Courtesy of SIM&TEC S.A.