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

Numerical simulation of a syngas-fuelled engine
dV ⎛rc
−1⎞
⎛ ϕcosθ
⎞
= V
TDC
sinθ
1
dθ ⎜
2
⎟ +
2 2
⎝ ⎠ ⎜ 1 − ϕ sin θ ⎟
⎝
⎠
(6.6)
The mass fraction of each burned zone is defined as
mbi
,
xbi
,
= ( i = 1,..., n)
m
(6.7)
with the result for the total burned zone
x
b
m
= =∑ x
(6.8)
n
b
m i = 1
b,
i
tel-00623090, version 1 - 13 Sep 2011
The mass conservation equation is also applied to the cylinder charge, assuming zero
blow-by, providing
dm dm dm dm dm u b u bn ,
= + = + = 0
(6.9)
dθ dθ dθ dθ dθ
The previous relation has been derived assuming that the mass of each of the already
burned zones remains constant after its combustion: dm b,i /dθ = 0 (i=1,…, n-1), resulting
for the rate of change of mass of the total burned zone:
n
b
θ = ∑ i 1 b, i
θ =
b,
n
θ
(6.10)
=
dm d dm d dm d
Also, the perfect gas state equation is applied to each zone.
pV = m RT ( j = u, b − b )
(6.11)
j j j j 1 n
6.1.2 Chemical composition and thermodynamic properties
The unburned zone is considered to be a mixture of air and fuel, while also allowance
is made for the presence of residual gas trapped in the engine cylinder. The
composition and thermodynamic properties of the unburned mixture during
compression and combustion are determined from the values of pressure, temperature,
fuel–air equivalence ratio and residual gas mass fraction (Ferguson, 1986).
After the start of combustion and until the end of expansion at EVO, the combustion
products of each burned zone consist of a set of eleven chemical species: (1) CO 2 , (2)
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