NVision’s Contract Service Div. recently reverse engineered the complete core of a steam turbine for a major OEM in six weeks compared to the six months budgeted for the project. “Measuring the critical blade geometry accurately made it possible for the turbine manufacturer to perform simulations that helped to redesign the blades and diaphragms to substantially improve the energy efficiency of the hundreds of existing turbines,” said Steve Kersen, president, NVision.
Computational fluid dynamics (CFD) technology shows how flow affects the performance of turbine blades and quickly and inexpensively evaluates alternative geometries by determining their impact on energy efficiency. To run CFD simulation it is essential to have a CAD model that accurately depicts the as-built turbine geometry. Nearly all of the turbines that are prime candidates for design upgrades were designed without a CAD model so reverse engineering was an essential first step to improving the turbine blade design.
The turbine rotor in this application measures 11 ft in length and 6 ft in diameter. NVision technicians scanned all of the turbine components in three weeks using the NVision HandHeld Non-contact Scanner and touch probe at the OEM’s site and the MAXOS scanner in NVision’s Wixom, Michigan facility.
The MAXOS scanner can measure complex geometry even if it has a shiny surface without the need for spraying and it is unaffected by the limitations of ball radius compensation found with traditional coordinate measuring machines.
Next technicians used NVision software to convert the point clouds to STL file format. The STL model was converted to a fully parametric CAD model, which took another three weeks. NVision engineers edited the resulting CAD models by hand to correct machining inaccuracies in the as-built parts. The CAD models were then used by the turbine manufacturer as the basis for the CFD simulations used to design new blades and diaphragms with improved energy efficiency.