Cutting CO₂ emissions is urgent, and renewable fuels like methanol and ethanol are getting increasing attention. This is especially true for heavy-duty transport, where switching to electric options isn’t straightforward. These fuels show real promise – but they also bring an unexpected challenge. Conventional fuel injectors, designed for diesel or petrol, don’t always behave well with such alternative fuels. Early tests revealed enhanced cavitation in the nozzle of the injectors: tiny vapour bubbles forming inside the injector caused by the pressure drops. Left unchecked, this can wear components faster than expected, shortening the injector’s lifespan.
Getting to grips with cavitation
To tackle this, the University of Luxembourg and PHINIA Inc., a global leader in automotive fuel systems, electrical systems and aftermarket solutions, launched the DIRECT2 project. Their approach combines digital simulations with hands-on experiments, covering pressure waves, cavitation, and thermal hydraulics. “It’s about seeing the invisible,” says Prof. Stephan Leyer.
The research began small. Venturi tubes and orifice channels let the team observe how bubbles form and evolve – even when using water as a stand-in for fuel. “Even the simplest experiments threw surprises,” Dr. Stefanitsis recalls. These early observations highlighted which injector designs could handle stress, and which fuel blends might be tricky over time.
From there, the team scaled up to full injector models, testing water–ethanol blends under realistic operating conditions. The results revealed how cavitation behaves in the real world and helped predict which designs will last. “We’ve learned a lot about how these fuels flow,” Dr. Stefanitsis notes, “but there’s still plenty to explore, including optimising injector designs and performing real injector measurements to verify our simulations.”
Looking inside with neutrons
Next on the agenda is neutron beam imaging, a technique that allows researchers to observe fluid flow inside metal injectors in real time. Unlike conventional cameras, neutrons can pass through metal and detect light elements like hydrogen, showing how cavitation bubbles and fuel move. The insights from this method are already guiding the design of injectors that are more durable and reliable.
Fueling a cleaner future
Methanol and ethanol are steadily proving their worth for heavy-duty transport – but getting them road-ready isn’t simple. DIRECT2 is tackling one of the trickiest challenges: injector wear. By combining simulations, experiments, and innovative imaging, the team is uncovering what really happens inside injectors and how to make them last. Step by step, their work is helping turn lab experiments into solutions that could soon hit Luxembourg’s roads, making transport cleaner, more efficient, and more sustainable.