Ultra-short laser pulses can be used to generate micro-patterns on the piston rings in vehicle engines to reduce their friction and ultimately the fuel consumption of the vehicle. (Image Fraunhofer IWS)
Engineers at the Fraunhofer Institute For Materials and Beam Technology IWS in Dresden, Germany, are working on using ultrafast lasers to produce microstructures on the components of vehicular combustion engines in order to reduce their friction, enabling the overall fuel consumption of the vehicle to be lowered by more than 10 per cent.
When the pistons in a car engine move up and down several thousand times a minute, they rub against the inner wall of the cylinder. This friction slows them down, wastes kinetic energy and ultimately fuel as well. In addition, small material losses and deformations damage the engine over time.
The IWS engineers are therefore using 500 femtosecond ultrafast laser pulses to generate fine structures – small holes spanning a few micrometres – on the piston rings of engines in order to reduce their friction. Such rings enclose the pistons like a seal to keep lubricating oil away from the combustion chamber. While invisible to the eye, under a microscope the structured holes look like drainage channels, or fishbones.
These bone patterns have two functions, according to Dr Udo Klotzbach of Fraunhofer IWS: ‘On the one hand, they reduce the areas that can rub against the cylinder wall at all. On the other hand, the channels direct the engine oil to the areas where the greatest frictional losses normally occur. In a sense, if we stick to the fishbone [analogy], its spine is the channel through which new oil flows when needed.’
The microstructures cause a protective oil film to float between the ring and the inner wall of the cylinder at all times when the engine is running, therefore reducing the friction within the system.
Klotzbach estimates that if selected individual parts in combustion engines were treated with this process, cars could consume several per cent less gasoline or diesel. ‘If we also use it to machine plain bearings, rolling bearings and other moving vehicle parts and calculate this for the entire car, we can even achieve savings in the double-digit percentage range,’ he added.
Similar friction problems arise in many other mechanical systems, for example in locomotives or milling machines. Even modern electric cars waste part of their battery charge through friction in the electric motor and other moving parts. According to Fraunhofer IWS, forecasts indicate that such friction and the associated wear consume around 2-7 per cent of Germany's economic output each year. Microstructures could therefore significantly reduce these frictional losses – and the associated expenditure – all while making the components of the systems last approximately 30 per cent longer on average, according to Klotzbach.
The Fraunhofer engineers have developed the new process to allow it to be used in mass production, and are now testing it together with partners from the automotive industry. IWS scientists are also exploring other applications for their micro fishbones, for example in mechanical engineering and for sports equipment.
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