Abstract: A porous silicon carbide insert is located in the burner and defines the burner head. This provides a larger area for the flame to attach to the burner head since the porous insert causes the gas/air mixture to flow from the entire burner head. A more stable flame results and the flame is unable to travel back into the burner venturi through the insert.

Abstract: A porous, ceramic member defines both the burner and baffle. Gaseous fuel is supplied under pressure into a chamber and flows through the ceramic member and, in flowing, causes the aspiration of atmospheric air into the flowing gaseous fuel. The air-fuel mixture is ignited a short distance downstream of the chamber and the flame flows through the ceramic member and emerges from the ceramic member within the heat exchanger. The air mixing with the gaseous fuel causes turbulence and mixing of the gas and cools the flame prior to its reaching temperatures associated with the generation of thermal NO.sub.x.

Abstract: A baffle is located in a recessed location relative to the inlet of a heat exchanger tube and facing the burner. The baffle is made of high temperature ceramic foam and has a plurality of flutes which define the flow path. In passing through the baffle, the velocity of the flame pattern is increased which reduces the noise level. The baffle also reduces NO.sub.x as a result of heat transfer to the baffle.

Abstract: A spiral, perforate ceramic baffle is placed into a heat exchanger in facing relationship with the burner and in an overhung relationship to the heat exchanger. A primary air/fuel mixture in the flame from the burner passes into the baffle drawing secondary air into the overhung portion of the baffle cooling the burner flame. Turbulence of the burner flame pattern in the baffle changes heat exchanger harmonic resonance and reduces burner noise.