Etude de la combustion de gaz de synthèse issus d'un processus de ...

COMBUSTION STUDY OF MIXTURES RESULTING FROM A GASIFICATION
PROCESS OF FOREST BIOMASS
Abstract
tel-00623090, version 1 - 13 Sep 2011
Syngas is being recognized as a viable energy source worldwide, particularly for
stationary power generation. In the current work, three typical syngas compositions
have been considered as representative of the syngas resultant from forest biomass
gasification, and the possibility of using it in internal combustion engines is studied.
First, laminar burning velocities have been determined from schlieren flame images at
normal temperature and pressure, over a range of equivalence ratios within the
flammability limits. The study of the effects of flame stretch rate is performed through
the determination of Karlovitz and Markstein numbers. Second, because of the gaps in
the fundamental understand of syngas combustion characteristics, especially at
elevated pressures that are relevant to practical combustors, constant volume spherical
expanding flames were employed to measure the laminar burning velocity for
pressures ranges up to 20 bar. This information on laminar burning velocity of syngasair
flames is then applied in a multi-zone heat transfer simulation code of the wall-flame
interaction in order to predict the quenching distance of typical syngas-air flames.
Engine-like turbulent conditions were experimentally reproduced in a rapid
compression machine (RCM) when working on two strokes mode simulating a single
cycle of an internal combustion engine. Stationary power applications usually use
natural gas as fuel, thus a methane-air mixture is also included in this work as a
reference fuel for comparison with the typical syngas compositions under study. Single
compression tests were also performed in the RCM operating with and without
combustion in order to identify different parameters related with its operation, namely
the heat transfer to the walls. A simulation code for the power cycle of syngas-fuelled
engines has been developed. Model validation has been carried on over detailed
experimental data available in literature for hydrogen and methane. An attempt to
adapt the model to the RCM is made by changing several aspects of the model namely
the in-cylinder volume function and burning rate model. Conclusion could e drawn that
the adapted code is able to reproduce the in-cylinder pressure. The validated model is
then applied to a syngas-fuelled engine in order determine its performance. Conclusion
can be drawn that typical syngas compositions besides its lower heat values and
burning velocities can be used on SI engines even at elevated rotation speeds.
Keywords: Gasification – Syngas - Combustion – Burning velocity – Rapid
compression machine - Multi-zone modeling.