EMPI - Reactive Fluids

Combustion reactions in many practical applications occur under elevated pressures, such as in internal combustion engines, gas turbines in power plants and aircraft engines. These systems are typically complex and often unsteady, making it challenging to attribute observed effects to specific causes. A stationary high-pressure burner offers significant advantages for systematically studying such combustion processes, as individual parameters can be varied while keeping other conditions constant. Our facility focuses on investigating soot formation in premixed flames as a function of pressure and studying the pressure dependence of non-intrusive laser diagnostic measurement methods, such as laser-induced incandescence (LII), laser-induced fluorescence (LIF), and highly sensitive absorption measurements such as cavity ringdown spectroscopy (CRDS). The burner is designed for operating pressures up to 40 bar.

The burner features three concentric rotationally symmetric porous metal plates through which fuel/air mixtures of different compositions flow. The central inner burner generates the detectable sooting flame. The central flame is surrounded by an outer burner ring, which stabilizes the central flame with minimal interference. An additional sheath flow around the outer burner supplies inert gases or air to keep hot combustion gases away from the burner walls, preventing window contamination. Optical access is provided via four side windows. For time-resolved LII measurements, a pulsed Nd:YAG laser is used, with the LII signal detected by fast photomultipliers during the cooling phase of the particles heated by the laser pulse.

Our research aims to understand the mechanisms of soot nucleation and growth under high-pressure conditions. This includes examining the balance between soot formation and oxidation and exploring how soot particle sizes and volume fractions depend on pressure. The insight gained from these studies is crucial for developing reliable chemistry mechanisms and more efficient and cleaner combustion systems. The continued development of our high-pressure burner and diagnostic methods enhances our ability to study complex combustion phenomena and contribute to the advancement of combustion science and technology.