PhD defense by Annalisa DI STAZIO.
Location: ICARE – 1C avenue de la recherche scientifique – campus CNRS Orléans
Title : Experimental characterization of the combustion dynamics at micro-scale.
Discipline : Energetics, Thermal, Combustion
Nowadays with the demand for high efficiency systems, there is growing development and application of micro electro-mechanical systems (MEMS devices) which may generate more energy than the modern batteries. In this context, a new experimental device has been developed. It consists of a micro tubular reactor with a controlled external temperature profile. The high gas temperature allows auto-ignition of the mixture and the flame stabilization in reactors with inner diameter smaller than the ordinary quenching diameter. The temperature profile along the tube is measured continuously using an infrared camera while an EMCCD camera is used to collect the CH emission from the flame. The present experimental study on fuel/air mixtures reacting in narrow channels has been undertaken to provide detailed information on flame combustion at micro-scale. Three kinds of flame behavior were observed:
(i) bright and stable flames under high flow velocity, (ii) flames with repetitive extinction and ignition (FREI) in the middle flow rate range, and (iii) weak flames at low flow rates. The presence of oscillating transitional
regimes was also investigated and a detailed analysis of the unstable regimes (determination of frequencies and characteristic times) was carried out. Three fuels were used, namely methane, ethylene, and acetylene.
The effect of different parameters was investigated: inlet velocity, equivalence ratio, and reactor size. Numerical simulations were also conducted to study the ignition characteristics of unstable flames.
Keywords: Micro-combustion, Flame stabilization, FREI, Oscillating Flames, Weak flames, Methane, Ethylene, Acetylene, Flame Ignition.