Steam generator

Claim 1

A steam generator, comprising: a water flow pipe having a water inlet and a steam outlet for generating steam in said flow pipe, said flow pipe forming an enclosure structure defining a combustion space; a burner arranged in said combustion space for heating water in said flow pipe by the emission of exhaust gases; an inner housing surrounding said enclosure structure defining therewith an inner chamber provided with an exhaust gas outlet for passing exhaust gases from said burner through said inner chamber and into said exhaust gas outlet; an intermediate housing surrounding said inner housing defining therewith an intermediate chamber through which combustion air is supplied to said burner; an outermost housing surrounding said intermediate housing defining therewith an outer chamber provided with an aspiration opening; a blower, having a suction side and an outlet side, wherein the suction side is connected to the outer chamber and the pressure side to the intermediate chamber, forcing combustion air flowing from the aspiration opening through the outer chamber to the suction side of the blower, and from the pressure side of the blower into and through the intermediate chamber to the burner, thus generating exhaust gases which are directed through the combustion space into and through the inner chamber to the exhaust gas outlet; whereby the combustion air is preheated in two temperature drop stages in that the exhaust gases in the inner chamber will pre-heat the combustion air flow in the intermediate chamber, and the pre-heated combustion air in the intermediate chamber will pre-heat the fresh incoming combustion air in the outer chamber.