Measuring soot formation in a diesel engine is far from easy because the turbulent environment in the combustion cylinder means no two combustion cycles are the same. Furthermore, the measurements are difficult to reproduce as the pressure at which fuel is injected into the cylinder causes an extra source of turbulence.

Bas Bougie, a doctoral candidate at Radboud University Nijmegen created a glass cylinder with an engine so he could investigate soot formation and find ways to optimize diesel performance using laser light.

Laser Induced Incandescence (LII) can be used to investigate optimal engine conditions that reduce soot emission from the engine. LII can be deployed in different types of engines and with different fuels. Bougie carried out measurements during higher and lower loading of the engine and for two different fuel injection systems: a line pump system and a common rail system.

Neither the engine load nor the injection system was found to affect the primary particle size of the soot emitted. However, there are many other motor settings that can lead to an improvement in the combustion.

The results of the measurements can now be used to verify existing combustion models at Eindhoven University of Technology. Together with the STW users' committee (participants are: DAF, Eindhoven University of Technology, Delft University of Technology, the University of Twente, Cyclone Fluid dynamics, EP Controls BV, Paul Scherrer Institute (Villigen, Switzerland), Royal Netherlands Naval College, TNO and Shell), Eindhoven University of Technology will investigate further improvements to the measuring system with the ultimate objective of producing cleaner diesel engines.

Bougie's doctoral research was part of a program of the Institute for Molecules and Material (IMM) of the Radboud University Nijmegen and was performed in cooperation with the Paul Scherrer Institute in Switzerland.

Bas Bougie’s research was funded by Technology Foundation STW.