Biodiesel Breakthrough: Study Reveals How Bubbles Impact Engine Efficiency

Researchers at the University of Gothenburg are investigating the formation of bubbles in biodiesel droplets, a key factor in optimizing combustion efficiency in internal combustion engines. By understanding this process, future engines could maximize energy extraction from biodiesel, resulting in lower emissions and better fuel efficiency.

Biodiesel is a renewable and biodegradable fuel produced domestically from vegetable oils, animal fats, or recycled restaurant grease. It fulfills both the biomass-based diesel and overall advanced biofuel requirements of the Renewable Fuel Standard. It is important to note that renewable diesel differs from biodiesel.

In its pure, unblended form, biodiesel is often called B100 or neat biodiesel. Like petroleum diesel, biodiesel is used to fuel compression-ignition engines.

In internal combustion engines, fuel is injected in small droplets to maximize combustion. These droplets are pressurized to turn into gas, and during this process, bubbles form inside the droplets. The team, led by Dr. Yogeshwar Nath Mishra and Professor Dag Hanstorp, used femtosecond lasers to study these bubbles.

"The bubbles have a significant impact on the atomisation of biodiesel in engines. Therefore, our research is very important to address fundamental questions about the efficiency of the biodiesel engine," said Dr. Mishra.

Understanding how and when bubbles form in fuel droplets could lead to the development of more efficient engines that burn fuel more completely, resulting in fewer environmentally harmful emissions.

Dr. Mishra observed:

"Research on biodiesel is crucial in our transition from fossil fuels to combat climate change. In engines, bubbling affects fuel combustion and contributes to the formation of larger droplets that do not evaporate and burn completely, leading to increased emissions.”

Studying bubble formation within engine injection valves is challenging due to their complex structure. However, the researchers employed cutting-edge techniques to overcome this obstacle. They used a standing sound wave to levitate a millimeter-sized biodiesel droplet in the air.

The findings, published in Nature Scientific Reports, offer significant insights into bubble formation, which are not only applicable to developing more efficient fuels and combustion engines but also have broader industrial implications.

"Bubble formation is important in industries such as chemical engineering for example carbonated drinks, ultrasonic imaging, boiling processes for heat transfer and processes such as gas release from water bodies and cloud formation. But what we have achieved is basic research. There is still a lot of development to be done before it can be used," said Hanstorp.