Towards Lean Combustion: The Influence of Rich-Lean Strategies and The Problem of Thermoacoustics

May 10 2017 04:00 PM - May 10 2017 05:00 PM

Prof. Edgar C. Fernandes from the University of Lisbon gave a seminar titled 'Towards Lean Combustion: The Influence of Rich-Lean Strategies and The Problem of Thermoacoustics' on 10 May 2017.

The seminar, hosted by Prof. Deanna Lacoste of CCRC evaluated different technological ideas used in an effort to burn gaseous fuels under lean conditions such as detached impinging lean flames and attached stratified global lean flames.

Impinging gaseous jet flame is of relevance in a variety of engineering and industrial applications, such as drying, heating processes, polymer treatment, metal cutting and domestic burners. The present work analyzed impinging lean disc flames (lifted from the burner and anchored on the plate), stabilized by a Helmholtz burner. In this case, the lean flames were prone to thermoacoustic oscillations and found to oscillate with either one single frequency (f ) or two simultaneous frequencies (f, 2f) controlled by different regions of the flame.
On the other hand, if a lean flame is to be attached to a burner then stratified flames (either on equivalence ratio or velocity ratio) have been previously demonstrated to present different behavior than their equivalent homogenous flames. NOx and CO emissions were experimentally measured in order to characterize the influence of equivalence ratio gradients and velocity gradients on the reduction of these emissions. Results show that both strategies have a positive effect on the extension of the flammability limits, preventing the lift-off of peripheral flames (responsible for thermoacoustic oscillations). Consequently, CO emissions present low values for a wider operability range.

Edgar C. Fernandes is an Assistant Professor in the Center IN+ - Lab. of Themofluids and Energy Systems, Dept. Mech. Engineering
Instituto Superior Técnico, University of Lisbon, Portugal.