Burner with adjustable end cap and method of operating same

A boiler system comprising:

• a boiler housing having a generally cylindrical shape and extending between first and second walls to provide a generally cylindrical space;
• a fire tube positioned near a bottom of the generally cylindrical boiler housing and extending longitudinally from a first wall of the cylindrical boiler housing to a fire tube end wall,
• a burner having a generally cylindrical burner housing and an end plate, the burner housing defining a generally cylindrical chamber;
• wherein the fire tube provides a combustion chamber where combustion of an air-fuel mixture is accomplished using the burner, the burner extending into the fire tube;
• wherein the end plate of the burner is adjustable between a minimum gap position corresponding to and providing a minimum gap generally located between an end of the cylindrical burner housing and a surface of the end plate facing the end of the cylindrical burner housing, and a predefined position corresponding to and providing a gap between the end of the cylindrical burner housing and the surface of the end plate facing the end of the cylindrical burner housing, such that the gap of the predefined position is larger than the minimum gap, so as to adjust a flame that extends from within the burner housing into the fire tube;
• wherein the burner comprises at least two exits for combustible gases, a first exit being formed in at least one of the minimum gap and the gap of the predefined position, the first exit comprising a series of discharge openings arranged in circumferentially spaced-apart relation to one another around the circumference of the burner, the series of discharge openings being defined by a downstream end of the burner housing, the end plate, and a set of discharge plate spacers.