Courtesy of Dr. David Wood at the University of Calgary, Schulich School of Engineering
A student at the University of Calgary in the Schulich School of Engineering contacted Rapid3D requesting a scan be completed of a model turbine test rig. The group at UofC was interested in addressing the issue of wind turbine blade erosion and its effect on power output. The test rig is being used to develop a laser scanning system to monitor blade shape which can change significantly due to erosion. Because of this, the student was particularly interested in the outer surface of the individual turbine blades and wanted to bring that surface into Solidworks for further testing, design modifications, and analysis.
The blades were each just over 1m in length, with the maximum chord length around 20cm. The blades were removed from the motor driver and brought to Rapid3D for scanning.
We decided to scan the blades with the MetraSCAN, simply due to the size of the blades. We scanned at a reasonably high resolution of 0.600mm measurement spacing, so we could accurately and precisely capture the geometry of the thin edges of the blades. The first side of the blades were scanned, then flipped, so the backside of the blades could be scanned as well. The scans were merged based on overlapping geometry in VXelements to produce a final mesh.
Once merged, Rapid3D and the University of Calgary decided that the best format for these blades that was cost-effective and still informative was to produce an auto surface of the turbine blades. An auto surface is like a shrink-wrapped surface to the mesh data. The auto surface can be produced in a generic CAD format, such as a .STEP or .IGES file, which can then be brought into CAD programs like Solidworks. First, we aligned the blades based on the motor mounting points.
Then, we used the “Add Surface” “Auto Surface” tool in VXmodel. We adjusted the number of individual patches to be created, as well as the number of control points per patch. The higher the control points per patch, the more likely we are to capture the true geometry of the scan.
The final model was delivered to the student at the Schulich School of Engineering for each blade The test rig is being used to develop the laser system which will then be tested in a wind farm. This technology promises to be a quantum leap from the current practice of flying drones through a wind farm to take photographs of blades which are then assessed visually by a technician.