Aeroprobe probes used in DOE’s renewable energy research
DOE’s National Renewable Energy Laboratory (NREL) tested a 10-meter diameter research wind turbine in the world’s largest wind tunnel, NASA’s 24.4 by 36.6 meter (80’ by 120’) wind tunnel. This tunnel is part of the National Full-Scale Aerodynamics Complex (NFAC) at the NASA Ames Research Center in Moffett Field, (Silicon Valley) California and is primarily used for determining low- and medium-speed aerodynamic characteristics of full-scale aircraft and rotorcraft. The tunnel is powered by six 18,000-hp fans that produce test section wind velocities up to 50 m/s (115 mph).
The five 7-hole probes by Aeroprobe were installed on one of the turbine blades to measure the flow magnitude and direction, as seen by the blade.
The NREL "Unsteady Aerodynamics" research wind turbine was extensively instrumented to measure structural loads and aerodynamic responses of a rotating airfoil. Five 7-hole probes were fabricated by Aeroprobe and installed on one of the blades, as shown in the figure below. The probes were installed on special booms mounted on the blade leading edge and rotate with the blade. The probes provide measurements on the flow magnitude and direction, as seen by the blade. The turbine was tested in the tunnel in a 2-bladed, fixed-pitch (stall-controlled) configuration. It operated at constant RPM with the rotor oriented upwind or downwind of the tower, and the hub in either rigid or damped-teetered configurations. An extensive range of pitch angles, pitch motions, yaw positions, and wind velocities were planned. NREL researchers focused wind tunnel test objectives to meet recommendations of an international science panel of wind turbine aerodynamics experts.
The five 7-hole probes by Aeroprobe were installed on one of the turbine blades to measure the flow magnitude and direction, as seen by the blade.
The NREL research turbine has been field-tested in various configurations since 1989 at National Wind Technology Center (NWTC) located near Boulder, Colorado. It has been operated in outdoor atmospheric turbulent wind conditions up to 31 m/s (70 mph), and has been exposed to winds above 65 m/s (145 mph) with the rotor parked. The figure below illustrates one of those test, during which, amongst else, probe data were acquired and flow visualization was performed. The probes can be seen installed at the leading edge of the top (black) blade.
Test data have been made available to the research community through International Energy Agency Annex XIV and Annex XVIII. Reports summarizing results of the atmospheric turbine tests have demonstrated the extremely complex dynamic nature of the typical wind turbine operating environment. Highly turbulent wind and sheared inflow conditions are major factors that contribute to the complexity. Testing in a controlled, wind tunnel environment will eliminate these factors, and resulting data will provide information from which a significant portion of the complex inflow-induced operating environment is removed. This will enable researchers to isolate and characterize specific dynamic stall responses and 3-D rotational effects under benign steady-state operating conditions. Resulting data are needed to improve and validate enhanced engineering models for designing and analyzing advanced wind energy machines.
