Researchers studying how bubbles in biodiesel help engine efficiency

By studying how bubbles form in a drop of biodiesel, researchers at the University of Gothenburg can help future engines get the most energy out of the fuel.

In an internal combustion engine, the fuel is distributed in small droplets in injection valves to maximise combustion.

In the engine, the fuel droplets are pressurised to turn into gas and burn. When gas is formed, bubbles form inside the droplets and it is these that the researchers at the University of Gothenburg have studied using femtosecond lasers.

Researchers are trying to understand how and when the bubbles form in the fuel droplets. In the long term, this knowledge could lead to the development of a more efficient engine that burns more fuel than today, resulting in less environmentally harmful emissions.

Studying bubble formation in engine injection valves is difficult because of their structure, with narrow channels in metal bodies. But with the latest technology, physicists can set up an experiment in the lab that allows them to study the process in a millimetre-sized drop of biodiesel. First, a fuel droplet is levitated, i.e. trapped in the air, using a standing sound wave.

The results, published have provided significant insights into the phenomenon of bubble formation that are not only useful in the development of more efficient fuels and combustion engines.