Transforming turbomachinery, from energy to aerospace

Turbomachinery, which uses a system of rotors to transfer energy from a gas or fluid, plays an integral role in virtually all types of energy systems—from windmills to gas turbines. In aerospace in particular, turbomachinery is essential to flight. In fact, jet engines are among the most common gas turbines, functioning by pulling air in through a fan and using a compressor to increase the pressure of the air, which is then combined with fuel and ignited, generating a thrust for the aircraft. Like most industries, aerospace is today faced with demands to make systems more fuel efficient and sustainable, as well as most cost efficient. Jet engine design and functionality is one area where these gains can be made, and additive manufacturing can play a central role.

Additive manufacturing is unlocking many doors when it comes to improving the design and efficiency of turbomachinery systems. This has become clear thanks to groundbreaking work from the energy sector by Sweden-based Siemens Energy, which has used EOS powder bed fusion solutions to not only redesign gas turbine components for greater efficiency, but also to accelerate lead times and dramatically improve turbine repair processes.

Nearly a decade ago, Siemens successfully completed its first full load test (13,000 revolutions per minute at temperatures beyond 1,250°C) for 3D printed turbine blades at its facility in Lincoln, England. This breakthrough, which took lead times from two years down to two months, showed that AM was more than viable for developing and manufacturing turbine systems while circumventing previous hurdles, like costly tooling. At the time, while the tested turbine blades were a conventional design, Siemens was already investigating the potential of using AM to integrate smart design changes, like high-performance cooling channels.

“This is a breakthrough success for the use of additive manufacturing in the power generation field, which is one of the most challenging applications for this technology,” Willi Meixner, then CEO of the Siemens Power and Gas Division, said in 2017. “Additive Manufacturing is one of our main pillars in our digitalization strategy. The successful tests were the result of a dedicated international project team[…] In just 18 months they completed the entire chain from component design and AM material development to new methods for lifing simulations and quality controls. With our combined know-how in 3D printing, we will continue to drive the technological development and application in this field.”

Since those first tests in 2017, Siemens has continued to drive technological advancement in this field with increasingly sophisticated capabilities driven by EOS hardware. Today, the company operates production facilities in Finspång, Sweden and Worcester, UK where turbomachinery components are made in series using a fleet of nearly 50 EOS 3D printers.

Among the parts manufactured are turbine guide vanes, which were traditionally cast from a nickel-based superalloy. In total, roughly 100 guide vanes are used in a gas turbine’s two stages, and each must withstand temperatures reaching up to 1,800°C. EOS metal 3D printing—and the design freedom it affords—has enabled Siemens engineers to redesign the blades to integrate more effective cooling systems. This has had a couple benefits. For one, more efficient built-in cooling reduces the need for cooling air, bringing down fuel consumption. Second, more effective cooling as the turbine operates can actually help to extend the vanes’ performance and lifespan.

In line with this, metal AM is also being used by Siemens Energy to minimize maintenance costs, while making the most out of existing turbine infrastructure. That is, Siemens Energy provides long-term maintenance services to its customers for its turbomachinery systems and is increasingly integrating AM to not only reduce system downtimes but also to improve overall performance and extend turbine lifespans.

In a recent case study, for instance, EOS illustrates how its technology (specifically an adapted EOSINT M 280) is making it possible for Siemens Energy to repair a burner tip on a gas turbine.

The burner tip, where the ignition of the fuel and air mixture occurs, is the site of extreme heat, which translates to significant wear and tear. To account for this, Siemens Energy has established a prescribed operating period that indicates when the component should undergo repair. Traditionally, the repair process consisted of cutting out the old burner tip and welding on a prefabricated replacement. This operation, however, was found to be time consuming and complex, requiring a number of sub-processes and tests.

With metal AM, however, Siemens Energy has been able to streamline the repair process significantly by simply removing and replacing damaged areas of the burner, rather than the entire burner tip. The company realized that it could also bring older burner designs up to date during the repair process using EOS’ technology.

“In addition to improving its own repair process, Siemens can now offer its customers strategic advantages,” reads the case study. “Thanks to this new process, experts can make improvements to turbine technology by integrating the components into the repair process. In this way, operators can make use of the latest technology, even if their turbines have seen years of service.”

From EOS’ perspective, the AM company played a major role in facilitating this innovative turbomachinery repair application. Namely, EOS re-worked an existing EOSINT 3D printer at Siemens’ facility and equipped it with a significantly larger build area to accommodate the burner’s 800 mm size. This system update reportedly took under a year and has made a huge difference at Siemens Energy. “We have successfully pushed our technology into the repair arena. We’ve shown that we are capable of modifying our system quickly to meet customer-specific requirements. In this case the modifications to both hardware and software were significant. Everyone involved can look back with satisfaction, not only at the end result but also the route to achieving it,” added Stefan Oswald from EOS.

Ultimately, additive manufacturing is transforming development, production and repair workflows associated with gas turbines in the energy industry. The benefits realized in this segment—including greater fuel efficiency, faster lead times and greater repair capacity—can be translated seamlessly to aerospace and jet engines in particular, thus paving the way to a more sustainable and economical future for the industry.

This article was originally published in VoxelMatters’ VM Focus Aerospace AM eBook. Read or download the full eBook for free at this link.