Transient performance of catalytic combustors for gas turbine applications

Abstract

The transient response of a monolith catalytic combustor to changes in operating conditions and monolith design parameters has been examined on the basis of a mathematical model. The model considers both catalytic and gas phase reactions and allows for axial conduction of heat in the solid substrate. The transient response time is shown to be determined primarily by the thermal inertia of the monolith with metallic monoliths, having lower thermal inertia, offering superior performance to ceramics. Improved performance is also favoured by a square cell geometry rather than triangular or sinusoidal geometry because of the better heat and mass transfer characteristics of the square cell geometry. Higher inlet temperatures, operating pressures and lower gas velocities are shown to result in faster response times. A step decrease in inlet gas temperature may result in catalyst overheating when either the catalytic (solid phase) or the homogeneous (gas phase) reactions are dominant.