An Improved Soave-Redlich-Kwong Equation of State

Combustion Theory and Modelling

Dupoirieux

2011

We first investigate a detailed high pressure flame model. Our model is based on thermodynamics of irreversible processes, statistical thermodynamics, and the kinetic theory of dense gases. We study thermodynamic properties, chemical production rates, transport fluxes, and establish that entropy production is nonnegative. We next investigate the structure of planar transcritical H 2 -O 2 -N 2 flames and perform a sensitivity analysis with respect to the model. Nonidealities in the equation of state and in the transport fluxes have a dramatic influence on the cold zone of the flame. Nonidealities in the chemical production rates-consistent with thermodynamics and important to insure positivity of entropy production-may also strongly influence flame structures at very high pressures. At sufficiently low temperatures, fresh mixtures of H 2 -O 2 -N 2 flames are found to be thermodynamically unstable in agreement with experimental results. We finally study the influence of various parameters associated with the initial reactants on the structure of transcritical planar H 2 -O 2 -N 2 flames as well as lean and rich extinction limits.

Section: Thermodynamics Coefficientsmentioning

confidence: 99%

Detailed modeling of planar transcritical H₂–O₂–N₂flames

Combustion Theory and Modelling

Dupoirieux

2011

“…Moreover, we also have lim T →+∞ α i (T ) = 0 since lim x→−∞ A(x) = −1 and the proof is complete. From physical considerations the coefficient α i = √ a i should be positive for small temperature and should be a decreasing function of temperature as pointed out by Ozokwelu and Erbar [49] and Grabovski and Daubert [50]. Moreover, the coefficient α i = √ a i should goes to zero as T → ∞ since we must recover the perfect gas equation of states for increasing temperatures.…”

Section: Thanks To the Properties Ofmentioning

confidence: 92%

“…From physical considerations the coefficient α i should be a decreasing function of the reduced temperatures T * i as pointed out by Ozokwelu and Erbar [49] and Grabovski and Daubert [50], and should converge to zero as T → ∞ in order to recover the perfect gas limit. Since the coefficient α i introduced by Soave does not satisfy such a property, it is first possible to truncate its temperature dependence in the form α i = 1 + s i (1 − T * i )…”

Section: B Parameters For the Srk Equation Of Statementioning

confidence: 98%

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Supercritical fluid thermodynamics from equations of state

Physica D: Nonlinear Phenomena

2012

Supercritical multicomponent fluid thermodynamics are often built from equations of state. We investigate mathematically such a construction of a Gibbsian thermodynamics compatible at low density with that of ideal gas mixtures starting from a pressure law. We further study the structure of chemical production rates obtained from nonequilibrium statistical thermodynamics. As a typical application, we consider the Soave-Redlich-Kwong cubic equation of state and investigate mathematically the corresponding thermodynamics. This thermodynamics is then used to study the stability of H2-O2-N2 mixtures at high pressure and low temperature as well as to illustrate the rôle of nonidealities in a transcritical H2-O2-N2 flame.

“…The function α i is such that α i (1) = 1 and, following Grabovski and Daubert [50] and Ozokwelu and Erbar [51], is a decreasing function of T * i . As discussed in [14], the original Soave determination [13] …”

Section: Thermodynamics Propertiesmentioning

confidence: 99%

Numerical simulation of transcritical strained laminar flames

2012

Combustion and Flame

We investigate reactive and non reactive strained flows associated with high pressure cryogenic rocket engines. A detailed high pressure fluid model based on thermodynamics of irreversible processes, statistical mechanics as well as kinetic theory of dense gases is used. This model insures the positivity of chemical entropy production and of molecular transport related entropy production. We first study the structure of a pseudo-vaporizing transcritical oxygen layer and the corresponding pseudo-vaporizing rates. We next investigate a mixing layer between cold hydrogen and oxygen and the dramatic influence of nonideal transport near thermodynamic instabilities. Diffusion and partially premixed H2-O2 transcritical flame structures are then studied as well as strain extinction limits and dilution extinction limits.