Swirling-flow burner

A swirling-flow burner comprising:

• an outer, peripheral burner tube;
• a central oxidizer supply tube concentric with and spaced from the burner tube, defining an outer annular fuel gas channel between the tubes, the oxidizer supply tube and the fuel gas channel having separate inlet ends and separate outlet ends;
• a fuel gas injector connected to the outlet end of the fuel gas channel, said fuel gas injector having a wall with a U-shaped cross sectional inner surface around a common axis of the burner tube and the injector and having a circular outlet end around the common axis, said U-shaped cross sectional inner surface narrowing toward said circular outlet end, for providing an unobstructed flow of fuel injected toward the common axis of the fuel gas injector;
• a central oxidizer injector connected to the outlet end of the central oxidizer supply tube, said oxidizer injector having a wall with a U-shaped cross sectional surface coaxial with and spaced from said fuel gas injector, said oxidizer injector having a circular and sharp-edged outlet end around the common axis, the sharp edge being formed by inner and outer surfaces of the oxidizer injector meeting to form a tip, the sharp edge having a tip angle of between 15.degree. and 60.degree. between the inner and outer surfaces, taken at the tip, which outlet end of the oxidizer injector is recessed from the outlet end of the fuel gas injector, said cross sectional surface narrowing toward said circular outlet end of said oxidizer injector;
• a cylindrical bluff-body coaxially arranged within the oxidizer injection chamber, the bluff-body having a domeshaped upstream end and a tapered downstream end;
• and
• a swirler installed on the bluff-body between its upstream end and its downstream end, the swirler having static swirler blades extending to the surface of the oxidizer injector;
• whereby oxidizer supplied to the oxidizer injector is injected into a downstream combustion zone in a swirling flow by means of the bluff-body and the swirler, which oxidizer flow is directed around the common axis of the injectors and the combustion zone after having passed through the oxidizer injector;
• the oxidizer is mixed in a high temperature inner region of the combustion zone with fuel gas being supplied to the fuel gas injector and injected into the combustion zone in an inwardly flow direction towards the common axis of the combustion zone after having passed through the fuel gas injector;
• and
• combustion products in a low temperature outer region of the combustion zone having an external, recirculation flow direction.