A small turbine injector has to deliver a precise amount of fuel through tiny openings as a fine mist.
Metal powder-bed fusion can build walls and internal passages, but printed surfaces are not perfectly smooth.
Fabian Hampp and colleagues at the University of Stuttgart and the German Aerospace Center aim to produce an additively manufactured injector for compact gas turbines and a wide range of fuels.
The reason to care about mixing
The university says soot and nitrogen oxides from carbon-containing fuels form mainly when fuel and air are not mixed well enough.
That is why an injection system aims for a fine fuel mist and a homogeneous mixture.
Surface condition becomes a design issue when a small opening has to meter that mist.
How the printed structure is made
In conventional metal powder-bed fusion, a thin powder layer is spread and selectively melted by a laser.
After solidification, the platform drops and the sequence repeats, building walls, cavities and connecting channels.
Those printed surfaces are not completely smooth, the researchers note.
What the team actually reported
They designed an injector that works despite printed roughness and miniaturized a principle used in aircraft turbines.
The team reports very clean combustion processes in the laboratory.
The nozzle design is described as accommodating fuels with different properties, including hydrogen, natural gas and kerosene.
Do not confuse lab results with deployment
Testing so far has been limited to laboratory conditions.
The team plans to optimize the manufacturing process and nozzle geometry before prototype trials with several fuels under real-world conditions.
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