Computation of chemical equilibria

Couto

Volume 2: Simple and Combined Cycles; Advanced Energy Systems and Renewables (Wind, Solar and Geothermal); Energy Water Nexus;

2014

The present study addresses SYNGAS combustion in static chamber, using both experimental and numerical approaches, in order to derive the quenching distance and heat flux in laminar syngas-air flames. Three typical mixtures of H2, CO, CH4, CO2 and N2 are considered as representative of the syngas coming from wood gasification, and its laminar combustion will be performed in a static spherical vessel. A two dimensional CFD model is used and validated under experimental runs. The classical Woschni model based on the hypotheses of forced convection and the Rivère model based on kinetic theory of gases are included in the CFD approach. The paper considers two different approaches for chemical reactions: the use of eight reactions and the multizone model. Temperature and pressure analysis is also being carried out. The numerical results are in good agreement with experimental ones. This study could be very useful in predicting the physical conditions of the quenching distance where the measurement is not possible such as in engines and the possibility of using this model in internal combustion engines.

Section: Flame Propagationmentioning

confidence: 99%

Syngas Combustion Analysis Using an Experimental and Numerical Approach

Couto

Volume 2: Simple and Combined Cycles; Advanced Energy Systems and Renewables (Wind, Solar and Geothermal); Energy Water Nexus;

2014

“…The knowledge of composition of detonation products is essential to estimate the detonation pressure from equation of state;1–8 hence precise determination of CEC becomes essential. Numerous methods have been reported to determine CEC 9–16. In the first study the Lagrange's multiplier or the equilibrium constants are used by Brinkley,9, 10 particularly suited for hand calculations.…”

Section: Introductionmentioning

confidence: 99%

“…This can be circumvented by a judicious choice of starting values or by an adjustment of a sequence of the “basic” components 12. An exponentially decaying iterative formulation with a weight, to be decided by trial and error, exists to determine CEC 15. However, there are many complicated cases in which methods presented in refs 9–15.…”

Section: Introductionmentioning

confidence: 99%

“…An exponentially decaying iterative formulation with a weight, to be decided by trial and error, exists to determine CEC 15. However, there are many complicated cases in which methods presented in refs 9–15. may fail 16.…”

Section: Introductionmentioning

confidence: 99%

“…The process of conditional backtracking and adaptive set of refining factors for Newton–Raphson steps are employed to resolve the problem. The mathematical formulation proposed by Heuze et al (J Chem Phys 1985, 83, 4734) has been solved using proposed computational method, instead of empirical iterative formulation, as proposed by them. Results for the same numerical example, used by Heuze et al (J Chem Phys 1985, 83, 4734) and White et al (J Chem Phys 1958, 28, 751) are presented in addition to decomposition of Cyclotrimethylenetrinitramine for fixed temperature and pressure.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Globally convergent computation of chemical equilibrium composition

2007

We report the Newton-Raphson based globally convergent computational method for determination of chemical equilibrium composition. In the computation of chemical equilibrium composition, an appearance of nonpositive value of number of moles of any component leads to discrepancy. The process of conditional backtracking and adaptive set of refining factors for Newton-Raphson steps are employed to resolve the problem. The mathematical formulation proposed by Heuze et al. (J Chem Phys 1985, 83, 4734) has been solved using proposed computational method, instead of empirical iterative formulation, as proposed by them. Results for the same numerical example, used by Heuze et al. (J Chem Phys 1985, 83, 4734) and White et al. (J Chem Phys 1958, 28, 751) are presented in addition to decomposition of Cyclotrimethylenetrinitramine for fixed temperature and pressure. It is observed that the proposed method is efficient and globally convergent. An even noteworthy finding is that the set of refining factors can be chosen from the range 0.1 to eta, where eta may be greater than one depending on how smoothly system of nonlinear equations is dependant on corresponding variable. Related analysis and results are discussed.

Strategies for solving the chemical equilibrium problem and an efficient microcomputer‐based algorithm

Smith

Missen

1988

Can J Chem Eng

General strategies for solving the problem of computing the equilibrium composition of a multiphase, multispecies, chemically reacting system are discussed. An efficient new algorithm is presented based on these strategies, together with a microcomputer‐based implementation. Numerical examples show the algorithm's utility, and its advantages over other recently proposed methods in terns of a number of criteria, including speed and certainty of convergence. The range of problem types within the capability of the new algorithm, and its limitations are discussed.