For centuries, a streamlined prow was believed to be the only practical shape for the front section of a boat hull. That changed when World War I naval architect, David Watson Taylor, invented the bulbous bow. That nose-shaped design allows the water to flow perfectly around the boat almost without any bow waves. A new shape therefore allowed a previously unimagined increase in efficiency. Energy converter service provider Euro-K experienced something similar with the construction of optimized burner geometry for gases and liquids when they turned to using Additive Manufacturing (AM) technology provided by EOS.  With expertise in the field of small energy converters, Euro-K has a portfolio that ranges from advice on energy technology issues, including process analysis and optimization, to project planning, simulation, testing and production.A recent think-outside-the-prow-type challenge for the company was to develop and manufacture a multi-fuel burner—capable of using gaseous or liquid fuels—for the micro-gas turbines of a plant builder.

A micro burner in action. Euro-K provides burner design, expertise in additive manufacturing, and also access to test rig technology such as pictured here. (Source: Faculty of Combustion Engines and Aircraft Propulsion, Prof. H. P. Berg, BTU Cottbus - Senftenberg)

The Gas vs. Liquid Fuel Challenge

During the combustion of gaseous and liquid fuels, various methods are used to prepare the fuel and form the fuel / air mixture. Whereas the mixture formation with gaseous fuels can be achieved using relatively simple mechanisms, it always represents a challenge with liquid fuels.The reason? Liquid fuels need to be mixed in a suitable manner with the combustion air. But before this can take place, the surface area of the liquid fuel must be greatly increased. This is generally done by spraying it in a very fine spray using pneumatic, mechanical or pressure differential principles.This means that the availability of burners that support the use of gaseous as well as liquid fuels of all compositions is greatly limited. Euro-K decided to look for a novel solution to this dilemma and set about developing an optimized burner geometry that would allow different types and formats of fuel to be used without having to change the burner. The burner’s volume also needed to be reduced to a minimum.

Industrial Laser Sintering Provides Geometric Freedom

The production technology to match these needs for flexibility, minimized size and integral functionality was quickly located: Additive Manufacturing. With this process, a laser builds the product layer by layer from a fine metal powder. Euro-K benefited from the design freedom that this solution offered. Unlike conventional production methods, the limits to manufacturability, such as those experienced with machining or the flow properties of cooling cast materials, were virtually non-existent. EOS technology is also able to produce small batch sizes cost-effectively, allowing assembly costs to be reduced by 20%. Euro-K moved quickly to an AM solution, having already established a considerable level of expertise in the past through a number of projects.Managing Partner Sebastian Kießling explains: “We not only have a successful history in the design of efficient burners for various fuels, but we also have considerable expertise in Additive Manufacturing. For these customers we have designed a burner that allows fuels in various physical states to be used and which also demonstrates a low component volume.” In addition to experience and equipment— the project team used an EOS M 290 system—Euro-K was able to use its own test rig and simulation technology. This made it possible to start product development from an already high level of maturity.For the design work, the project team used CAD software that allowed the data to be transferred quickly and easily to the EOS system following definition of the final shape and size of the burner. As a material, the team chose EOS NickelAlloy IN718, a heat and corrosion-resistant nickel alloy that has excellent tensile strength, resilience, creep resistance and fracture resistance at temperatures up to 700° C. With this material and production technology, the engineers created the perfect burner   ready for use in the micro-gas turbines of the plant builder.

Results that Burn Brightly

A micro burner in action. Euro-K provides burner design, expertise in additive manufacturing, and also access to test rig technology such as pictured here. (Source: Faculty of Combustion Engines and Aircraft Propulsion, Prof. H. P. Berg, BTU Cottbus - Senftenberg) The new burner is able to use gaseous and liquid fuels equally effectively. The optimized geometry also allows the use of liquid fuels that are classified as difficult to burn, such as fuel oils that are created from the distillation of alcohol. The burner’s innovative design allowed that the size of the combustion chamber to be reduced by 20%. There was another advantage for the end users: up to now, the plant operator had to choose and commit to the type and format of the fuel used. It was therefore difficult to offset the fluctuating prices of different fuels, since switching to a different one was generally impossible or only possible with costly and time-intensive conversions of the micro-gas turbines. The new burner design now brings a heightened degree of flexibility for users.Frieder Neumann, Deputy Head of Micro-Gas Turbine Development at Bilfinger in Berlin, confirmed these advantages: “The actual combustion process has been optimized, we are able to guarantee our customers the freedom of choice in terms of fuel, and switching to other fuels after the plant has been purchased can be easily arranged. We are absolutely delighted by our partner’s expertise in design and production, as well as by the EOS technology that makes it possible.” Thus in energy—as in shipbuilding—it can sometimes be worth making waves by rethinking established practices.