Emissions are the main driving force behind technical development in the commercial vehicle segment too. “In particular, there’s a need to reduce nitrogen oxide emissions from diesel engines”, reports Tom George, project manager at IAV. “To do this, we need to improve the mixture of diesel and air in the combustion chamber.” This is why IAV’s experts have designed a piston with a new type of geometry. The star-shaped piston recess has undercuts to extend spray length which optimizes combustion and results in minimal NOx and soot emissions.
Besides lower emissions, the trend for commercial vehicle engines is also moving towards higher pressure levels in the combustion chamber which increases specific power output. To cope with loads of up to 300 bar, IAV’s designers have provided the new piston with a honeycomb structure which is light in weight and extremely strong at the same time. And finally, on the inside it has an innovative cooling system which uses sodium as coolant among others and keeps thermal load within the specified limits.
The innovative piston made it necessary to use 3D printing, also known as “additive manufacturing”. “Normally, pistons are forged or cast from steel”, George says. “However, this production method would not have given us the emission-reducing and lightweight geometry.” But additive manufacturing not only provides the designers with new design freedoms – the new method also significantly shortens the time from the finished CAD model to the first prototype in stainless steel: “It only takes two weeks from CAD model to prototype”, George reports. “Forging would have required much more patience.” On top of this, 3D printing delivers volume production quality in the first prototype.
The new production method is also suitable for the passenger car segment. “We can, of course, use pistons from the 3D printer here as well”, George says. “As the first demonstrator, however, we have designed the cylinder head for a single-cylinder engine with a cooling circuit that also has a honeycomb structure.” Besides being stronger and stiffer as well as lower in weight, it also scores with higher manufacturing precision as well as far less work at the mechanical post-machining stage.
The new components are being presented to initial IAV customers. For volume production, however, 3D printing is still too expensive: “But it’s ideal for prototypes”, George says. “Apart from this, costs in the field of additive manufacturing have fallen dramatically in the last five years which, in the medium term, could make 3D printing conceivable for mass production as well.”