Today's dynamic wholesale power markets have made cycling of gas turbines and heat-recovery steam generators commonplace and placed a premium on plant flexibility. A properly designed duct burner system can enhance that flexibility. A duct burner's performance is sensitive both to its internal structure and the exhaust gas characteristics of the turbine it serves. Because modern, grid-style duct burners provide few provisions for tuning, making them suitable for a range of operating conditions is the job of the designer.