Prof. William H. Green
MIT Dept. of Chemical Engineering

Many energy systems involve reacting flows where essentially all of the many
different chemical species in the fuel are reacting at once, and where the
coupling between the chemistry and mass and heat transport is crucial. It is
usually impossible to solve the pde's that describe these systems, because
they are stiff, highly nonlinear, and involve a huge number of state
variables. Hence, reduced models are invariably used in practice, usually
without any guarantee that the reduced model solution is faithful to the
original (unsolvable) full model. Some of the model-reduction approaches
used in the reacting flow community will be briefly reviewed, with comments
about their successes and failures. Unsolved problems, such as rigorous
error control and methods for handling the boundaries between reduced
submodels involving different equations and state variables, will be
outlined, and some preliminary work towards their solution will be outlined.