Catalytic afterburners with not fully developed flow: modelling and experimental performances

Catalytic afterburners using short monoliths take advantage of the enhancement of the transfer coefficients in not fully developed flow. The correlations for Nu and Sh in laminar flow in the entrance region of a monolith available from the literature are evaluated and compared with experimental data. A one-dimensional model is proposed and solved using the orthogonal collocation method under stationary and transient conditions.

The calculated results were compared with experimental data for the combustion of lean benzene—air mixtures in a short monolith.

The model is able to describe the behaviour of the afterburner satisfactorily if local Nu and Sh values for simultaneously developing velocity, temperature and concentration profiles are employed. If the light-off occurs part way along the monolith channels, a new thermal entrance should be considered.