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Laser research projects to increase fuel efficiency of ships and aircraft

A number of ongoing European research projects are using laser technology to structure and clean the surfaces of ships and aircraft in order to improve their fuel efficiency.

In the three-year ‘MultiFlex’ project, for example, scientists are using the world's first 'dot matrix' laser to create hydrophobic, anti-fouling metal and plastic surfaces. These could soon replace toxic ship paints and varnishes that are used to stop algae or barnacles sticking to hulls, reducing maintenance costs, fuel consumption and CO2 emissions.

Through harnessing a 1kW ultrafast laser and beam-splitting optics, the researchers can split a single high-energy pulse into a grid of 64 beamlets, each of which can be turned on, off, positioned, and tuned individually. The grid can be used to etch microscopic ‘spike’ structures onto sheet metal or plastic at a fast rate, creating a rough surface that reduces drag to inhibit the growth of bacteria, algae or even barnacles. The structures imitate the incredibly efficient skin of sharks, which is covered in millions of tiny protruding scales that reduce drag, making them highly efficient swimmers.

‘Existing ultrafast lasers are known for their precise ablation and cutting results. Unfortunately, processing large parts with such lasers can take weeks,’ said Dr Johannes Finger, coordinator of MultiFlex. ‘Our system will ablate more than 150mm³ in one minute, therefore making it hundreds of times faster than existing technologies.’

A grid of beamlets can be produced using an ultrafast laser and beamsplitting optics to increase the throughput of ultrafast laser processing. (Image: Fraunhofer ILT)

The MultiFlex partners consist of Fraunhofer ILT, RWTH Aachen University, Amplitude Systèmes, Lasea, and AA OptoElectronic.

In a separate multi-year research project ‘FoulLas’, scientists from the Laser Zentrum Hannover, Laserline and Fraunhofer IFAM are looking to develop a laser cleaning process that can be used underwater to gently and efficiently remove vegetation build-up from ship hulls. This will be done in an environmentally friendly way without damaging underlying paint-based antifouling and corrosion protection coatings.

Lasers can be used to gently remove vegetation build up on ship hulls. (Image: Fraunhofer IFAM)

Vegetation build-up on ship hulls is a major problem for the maritime industry, as it increases flow resistance and thereby the fuel consumption and CO2 emissions of ships. The laser process under development will damage the vegetation cells in such a way that, ideally, the water flow washes away the remaining material. Compared to standard mechanical cleaning processes, it should be possible to clean ships more efficiently and more gently with a laser, and thus to keep the flow resistance low.

A blue laser from Laserline will be tested for cleaning vegetation from ship hulls within the FoulLas project. (Image: Laserline)

The project partners are working with diode lasers in both the blue and infrared wavelengths, provided by Laserline. The setup that will deliver the laser beam underwater to the ship hull is still currently under development, Laser Systems Europe was told.

De-icing aircraft

Targeting fuel efficiency increases in aviation rather than maritime, the ‘Laser4Fun’ project is looking to use lasers to prevent and remove ice build-up on aircraft.

Ice on aircraft surfaces can be hazardous. It increases drag and fuel consumption, disrupts aerodynamic flows, compromises sensors, and decreases lift – which impairs the aircraft’s ability to fly safely.

Snow and ice therefore have to be cleared from aircraft before they take off. Currently this task falls to special vehicles that spray chemical agents onto all vulnerable surfaces. However, while these antifreezes prevent ice from forming, fluids of this type are both expensive and harmful to the environment. Moreover, a substantial amount – 400 to 600 litres – is needed to de-ice a single plane.

An demonstrator airfoil structured with a water-repellent surface. (Image: Airbus)

Airborne aircraft also have to be protected against ice build-up. In most cases, ice protection systems such as heating elements are facilitated on board to do the job. The great drawback of these however is that they increase fuel consumption.

Researchers at Fraunhofer IWS, Airbus and TU Dresden have therefore developed a direct laser interference patterning (DLIP) process, using ultrafast lasers, which enables complex, microscopic surface structures to be created on wing profiles in a single step. These surfaces decrease ice accumulation and accelerate de-icing.

Airbus was able to demonstrate that ice growth on the functionalised surface is self-limiting. In fact, the ice falls off after a certain amount of time without requiring added surface heating.

Additional experiments also showed that it took 70 seconds for the ice on an unstructured airfoil to melt at 60W of applied heat, while the ice on a structured airfoil receded completely after just five seconds using the same amount of applied heat. The DLIP technology accelerated the process by more than 90 per cent.

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