Advanced Manufacturing for Gas Turbines
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Ceramic cores are used during investment casting to form the internal cooling passages within the turbine airfoil, ultimately forming an array of pins and standing ribs on the inner wall of the casting, creating an engineered surface to control air turbulence and improve cooling efficiency.
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When an advanced manufacturing (AM) process is considered for application to produce a part or subsystem, it typically is evaluated for performance and cost. For example, can the AM process produce the part at a lower cost, with better performance, and be delivered on schedule? Will the new part fit seamlessly into the existing supply chain or assembly process? Cost, performance, schedule and assembly are the criteria that must be considered when a “traditionally” manufactured part is replaced by a new part from an AM process. The magnitude of the criteria, and the trade-offs between them, must be established to evaluate the efficacy of the overall AM process. If the AM process improves all of those factors, then the decision is clear.

For Mikro Systems Inc., this was exactly the case. Using its patented process, TOMO-Lithographic-Molding (TOMO), advanced ceramic cores could be fabricated quicker and cheaper allowing revolutionary performance improvements for gas turbine air foils.
Mikro, a high-technology manufacturing company in Charlottesville, VA, has customers that include international high-technology companies, and government and academic institutions. It has applied TOMO and developed a unique ceramic core casting technology that uses precision, three-dimensional, lithographically-derived tooling that permits the intricate design and casting of enhanced heat transfer features for gas turbine blades.

The Mikro approach allows new internal cooling features that are not possible with current casting processes. The replacement core casting technology is intended to seamlessly integrate with established casting processes used by industry, minimizing new capital investment requirements and quickly revolutionizing the ability to enhance existing and future turbines with new blade designs.

Mikro’s technology addresses the need for rapid, cost-effective manufacturing of advanced turbine blades that will improve the performance and reduce the cost of electricity produced by gas turbine power plants. While facilitating significantly better cooling performance, production lead time can be improved by 70 percent and development costs reduced by as much as 50 percent when compared with conventional core casting manufacturing processes. Tooling costs are also significantly reduced.

Much of the work by Mikro Systems was supported by the DOE Small Business Innovation (SBIR) program. The development and evaluation of advanced cooling features was also supported by NETL, Purdue University and Siemens Energy. Through successful development and validation of TOMO, Siemens signed a commercial license agreement with Mikro, and in 2013 opened a manufacturing facility in Charlottesville, for commercial production of ceramic cores for current products and gas turbines.