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In combustion , heat release parameter (or gas expansion parameter ) is a dimensionless parameter which measures the amount of heat released by the combustion process.[ 1] [ 2] It is defined as
q
=
T
a
d
−
T
u
T
u
{\displaystyle q={\frac {T_{ad}-T_{u}}{T_{u}}}}
where
In typical combustion process,
q
≈
3
−
8
{\displaystyle q\approx 3-8}
. For isobaric combustion, using ideal gas law , the parameter can be expressed in terms of density ,[ 3] i.e.,
q
=
T
a
d
−
T
u
T
u
=
ρ
u
−
ρ
a
d
ρ
u
.
{\displaystyle q={\frac {T_{ad}-T_{u}}{T_{u}}}={\frac {\rho _{u}-\rho _{ad}}{\rho _{u}}}.}
The ratio of burnt gas to unburnt gas temperature is
T
a
d
T
u
=
1
+
q
.
{\displaystyle {\frac {T_{ad}}{T_{u}}}=1+q.}
Gas expansion ratio
The gas expansion ratio is simply defined by
r
=
ρ
u
ρ
b
{\displaystyle r={\frac {\rho _{u}}{\rho _{b}}}}
which is related to
α
{\displaystyle \alpha }
by
r
=
1
+
q
.
{\displaystyle r=1+q.}
See also
References
^ Williams, Forman A. "Combustion theory." (1985).
^ Linan, Amable, and Forman Arthur Williams. "Fundamental aspects of combustion." (1993).
^ Clavin, P. (1985). Dynamic behavior of premixed flame fronts in laminar and turbulent flows. Progress in energy and combustion science, 11(1), 1-59.