A New Dimension For Industry: How 3D Printing Is Doing Its Part To Reduce Greenhouse Emissions

3D printing may still seem a bit like science fiction, but in truth, it's all around us - in luxury vehicles, jet engines and customized implants used to rebuild skulls and bones.

And now the technology is moving deeper into the hot belly of industry - inside power plants, where it's helping utilities generate more electricity and reduce emissions. 'It's a total disruptor,' says Guy Deleonardo, executive product manager for gas turbines at GE Power's Gas Power Systems business. GE Power has already shipped more than 9,000 3D-printed components for use in gas turbines to customers the world.

Deleonardo says that in the past, it took GE up to a decade to move the efficiency of a turbine up a single percentage point. But with 3D printing at the company's disposal, the time can now be counted in just years. That's because the technology enables designers to quickly manufacture prototypes, test them, tweak their design and hit print again.

When they are happy with the result, 3D printing also allows them to mass-produce the final parts with efficiency-boosting shapes that are too complex or expensive to make with traditional manufacturing methods.

One example are 3D-printed fuel nozzles for GE's latest HA-class gas turbines. A French power plant with an HA turbine earned a spot in 'Guinness World Records' in 2016 as the most efficient combined-cycle power station, clocking in at 62.2 percent efficiency.

But even before the news about the record came out, GE engineers were already beginning to make prototypes of a new 3D-printed nozzle that allowed them to push up efficiency to 64 percent this fall.

The engineers had to reach temperatures in excess of 3,000 degrees Fahrenheit to achieve efficiency this high. The design of the new nozzle mixes fuel and air in such a way that it also allows them to do this and also maintain low nitrogen oxides emissions at the same time. This combination was an important breakthrough. The team is now using it to bring efficiency of the HA turbines even higher - to 65 percent.

Engineers considered several options when designing the new nozzle, but they quickly settled on using additive manufacturing methods like 3D printing. The same part manufactured in a machine shop would have many thousands of brazed joints. The actual 3D-printed part they developed has no need for such joints. 'That's very exciting to engineers, as each of those joints creates [an opportunity for] a potential leak and decreased reliability,' Deleonardo says.

This zero-joint design enabled them to achieve shorter, hotter flames and faster combustion. The hotter, shorter combustion cycle means power plants need less fuel and produce fewer emissions, saving both money and the environment. Moving from 63 percent to 64 percent efficiency saves a large gas-fired power plant about $50 million in fuel costs over its life cycle.

3D printers produce parts layer by layer, directly from a computer file. GE Power uses a cobalt-chrome alloy in the nozzle, and the powdered metal used for printing must meet exact specifications. Deleonardo's team also has to keep an eye on more than 150 process parameters to make sure that the nozzle will survive in the harsh environment inside the gas turbines for as long as planned. 'It's all about chemistry and particle size of the metal powder,' Deleonardo says.

In 2016, GE acquired a majority stake in Arcam, which makes 3D printers as well as printing powders, providing the company with new, valuable know-how. 'With companies like Arcam, which make printers, powder and also provide 3D-printing expertise, we have a complete offering,' says Mohammad Ehteshami, who runs GE Additive.

As with all 3D-printed parts, the ability to quickly boost production and incorporate new designs is another huge benefit because iterating the design and building more nozzles simply requires more printers. Additive manufacturing also cuts costs by making the supply chain simpler, compared with traditional production methods like casting and machining.

GE Aviation already prints fuel nozzles for jet engines that carry passengers, and Deleonardo sees continued growth of 3D-printed part capability in the future. He expects advancements in available materials, the speed of production, part durability and the physical size of what we can print, allowing for greater efficiencies - and fewer emissions for a healthier environment. 'Additive opens the design space to areas that we have yet to explore,' he says. 'Engineers don't have to follow the rules, just their imaginations.'