For steady-state problems, the 0-D homogeneous systems described in Homogeneous 0-D Reactor Models
employ Reaction Design’s
numerical solver,
Twopnt, to determine a solution to the set of algebraic
equations governing these Reactor Models. Twopnt solves the
system of algebraic
equations by first applying a damped modified Newton
algorithm to the set of nonlinear algebraic equations represented by the steady-state versions of
Equation 8–1
, Equation 8–9
, Equation 8–19
, Equation 8–20
, Equation 8–21
, Equation 8–147
, and Equation 8–141
. However, in the event that the
Newton algorithm fails to converge during the iteration, the solution estimate will
automatically be conditioned by integration of the time-dependent version of the equations
over a fixed number of time steps. This time-stepping
procedure provides a new starting estimate for the Newton
algorithm that is closer to the steady-state solution, increasing the likelihood of
convergence for the Newton method. After time-stepping,
the Newton algorithm tries again for convergence and, if this fails,
Twopnt takes additional time steps on the transient solution to further
improve the initial iterate. Ultimately, the Newton
iteration converges on the steady-state solution.