A combustion system for automatic, real-time control of a combustion process which can be applied with significant advantage to a wide range of furnaces, boilers and combustors. The system includes a burner body having a primary first fluid inlet end forming at least one primary first fluid inlet and a first fluid outlet end forming at least one first fluid outlet. An inner conduit is disposed within the burner body, forming a fluid flow region between the burner body and the inner conduit. The inner conduit has a second fluid inlet distal from the first fluid outlet and a second fluid outlet proximate the first fluid outlet. An internal adjustment device is provided for adjusting a flow cross-sectional area for a first fluid and/or a second fluid disposed within the burner body.