Design, manufacture and testing of energy-converting micro gas turbines that optimise the combustion of fuels is the specialism of German firm Euro-K, based in Berlin and Cottbus.
The company has been steadily increasing the effectiveness of systems, concentrating on innovative burner geometry to raise combustion efficiency and lower exhaust gas emissions. In pursuit of these goals, it harnesses the versatility of metal additive manufacturing (AM) technology from EOS.
Whereas the formation of a combustible fuel/air mixture is relatively straightforward with gaseous fuels, liquid fuels present a challenge, as the surface area must be greatly increased. This is generally done by projecting it in a very fine spray using pneumatic, mechanical or pressure differential principles. Consequently, the availability of burners that support the use of liquid as well as gaseous fuels is limited.
Euro-K set out to produce a compact micro-burner that can handle both types of fuel efficiently. Its design freedom was greatly enhanced using AM, with which it has long been familiar, avoiding the constraints of conventional metalcutting and the uneven cooling of castings. The technology is able to produce small batch sizes economically and allows burner assembly costs to be reduced by 20%.
One of the processes the company uses is an EOS M 290 metal AM system. For the design work, CAD software is used that allows data to be transferred quickly and easily to the EOS system following definition of the final shape and size of the burner.
To create the optimal burner for use in the micro gas turbines of one of its customers, a Berlin-based plant builder, the Euro-K project team chose EOS NickelAlloy IN718. It is a heat- and corrosion-resistant material that has excellent tensile strength, resilience, and resistance to creep and fracture at temperatures up to 700°C.
The new burner is able to use gaseous and liquid fuels equally effectively. Optimised geometry also allows the use of liquid fuel oils that are classified as difficult to burn, such as those distilled of alcohol. Another positive effect is that the burner’s innovative design allows the size of the combustion chamber to be reduced by 20%.
There is an additional advantage for end users. Until now, a plant operator had to select the type and grade of fuel to be used, so it was impractical to take advantage of fluctuating market prices. The new burner design changes that by introducing flexibility of purchase.
Frieder Neumann, Deputy Head of Micro-Gas Turbine Development at Euro-K customer, Bilfinger, Berlin, confirmed: “As the combustion process has been optimised, we are able to guarantee our customers freedom of choice in terms of fuel and switching to other fuels after the plant has been purchased can be easily arranged."