A Method for Solving Certain Stiff Differential Equations.

Certain differential equations that arise when solving chemical kinetics problems which have widely differing time constants are analyzed by a method that implicitly separates the fast reacting components from the remaining components of the system. A method for determining equilibrium of the fast reacting components is provided, and these values provide the initial conditions for an associated system of differential equations that yields a first and second order solution of the original system. Computational experiments have shown that a suitably chosen method for solving the modified system may be superior to a direct solution with a stiff differential equation solver.