US Patent 10119701 Furnace combustion system and method

A furnace system includes a burner assembly configured to generate combustion products within a primary combustion zone comprising one or more burners. The furnace system includes a panel disposed downstream of the burner assembly along a flow path for the combustion products, where the panel includes at least one panel opening. The furnace system also includes a secondary combustion air gap defined by one or more spacers disposed between the burner assembly and the panel, such that a secondary combustion zone is established between the burner assembly and the panel and/or downstream of the panel. The secondary combustion air gap is downstream from and external the burner assembly.