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

Numerical simulation of a syngas-fuelled engine
literature data and in addition with the rapid compression machine results obtained in
this work. For this propose some adaptations to the engine-like code are needed and
are shown in advance.
6.1 Thermodynamic model
The basis for multi-zone models is formed by consideration of conservation of mass
and energy. In the following, the equations for the cylinder pressure and temperature(s)
are derived. This will show where additional information, in the form of sub-models, is
necessary in order to close these equations.
tel-00623090, version 1 - 13 Sep 2011
Before conservation of energy is written down for the cylinder volume, from inlet valve
closing (IVC) time to exhaust valve opening (EVO) time (i.e. the power cycle), some
assumptions are generally adopted to simplify the equations. During compression and
expansion, pressure is invariably assumed uniform throughout the cylinder; with fixed
unburned and burned gas regions in chemical equilibrium. During flame propagation,
burned and unburned zones are assumed to be separated by an infinitely thin flame
front, with no heat exchange between the two zones. All gases are considered ideal
gases; possible invalidity of the ideal gas law at high pressures is countered by the
associated high temperatures under engine combustion conditions. As the model is
zero-dimensional in nature, it does not account for any geometrical considerations of
the flame front position during combustion. As an example, figure 6.1 shows a
schematic, only of qualitative nature, of the combustion chamber.
V b1
V b2
V u
V b4
V b3
V b4
V u
Figure 6.1– Schematic of the combustion chamber with four burned zones.
This is the most frequently used approach for engine combustion models, where the
flame area is a spherical flame front truncated by the cylinder walls and the piston,
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