RATE-CONTROLLED CONSTRAINED-EQUILIBRIUM METHOD USING CONSTRAINT POTENTIALS

A method called rate-controlled constrained equilibrium has been devel oped. It is based on the assumption that complex chemical systems evol ve through a sequence of quasiequilibrium states determined by the ins tantaneous values of internal constraints on the system's composition. These constraints are imposed by slow rate-limiting reactions. The te chnique involves direct integration of the rate equations for the cons traint potentials (Lagrange multipliers conjugate to the constraints). The method has been tested for stoichiometric mixtures of hydrogen an d air in an adiabatic constant-volume chamber for a range of initial p ressures between 0.01 and 1000 atm and initial temperatures between 90 0 and 1500 K. The state of the system was determined by imposing const raints on the total number of moles, the moles of active valence and t he moles of free oxygen. The rate equations for constraint potentials were integrated in conjunction with conservation equations for a const ant volume and energy mixture. The results were in good agreement with those obtained by integration of a full set of nine rate equations ov er a wide range of temperature and pressure.