High turndown combustion system and method

A method of operating a combustion system to attain enhanced turndown operation, wherein the combustion system includes a blower, a mixing chamber, a burner, an air flow tube, a gas train, and an air inlet damper, wherein the blower is coupled between the mixing chamber and the burner, wherein the mixing chamber is coupled between the blower and each of the air flow tube and the gas train, wherein a first damper plate of the air inlet damper is positioned along the air flow tube, and wherein the first damper plate has an outer perimeter with a first edge portion that is complementary to an inner surface of the air flow tube and one or more additional edge portions that extend inwardly from the first edge portion and that define a first inwardly-extending cutout, the method comprising:

• at a first time:
• providing one or more first control signals at least indirectly from at least one control device so as to cause a blower to operate at a high speed, and to actuate the air inlet damper so that the first damper plate of the air inlet damper is rotated to an open position;
• and
• at a second time:
• providing one or more second control signals at least indirectly from the at least one control device so as to cause the blower to operate at a low speed, and to actuate the air inlet damper so that the first damper plate of the air inlet damper is rotated to a closed position, wherein, at the second time, at least some air continues to pass through the air flow tube past the first damper plate by way of the first inwardly-extending cutout defined by the one or more additional edge portions that extend inwardly from the first edge portion, so as to reach the mixing chamber.

A combustion system configured to achieve enhanced turndown operation, the combustion system comprising:

• an air flow tube;
• an air inlet damper positioned along the air flow tube;
• a gas train;
• a first gas valve positioned along the gas train;
• a mixing chamber coupled to the air flow tube and to the gas train;
• a burner;
• and
• a blower coupled between the mixing chamber and the burner;
• wherein a first flow of air via the air flow tube into the mixing chamber is governed at least in part by a first status of the air inlet damper and also at least in part by a speed of the blower,
• wherein a second flow of a gas via the gas train into the mixing chamber is governed at least in part by a second status of the first gas valve and also at least in part by the speed of the blower,
• wherein at least a first amount of the air and at least a second amount of the gas are mixed within the mixing chamber to form an air/gas mixture,
• wherein a third flow of the air/gas mixture from the mixing chamber to the burner is governed at least in part by the speed of the blower,
• wherein the air inlet damper includes a first damper plate having an outer perimeter with a first edge portion that is complementary to an inner surface of the air flow tube and one or more additional edge portions that define a first inwardly-extending cutout through which at least some of the air can pass even when the first status of the air inlet damper is a closed status in which the first damper plate is rotated so that the first edge portion is substantially adjacent to or in contact with the inner surface, and
• wherein the first damper plate further includes one or more further edge portions that define a second inwardly-extending cutout.

A method of operating a combustion system to attain enhanced turndown operation, wherein the combustion system includes a blower, a mixing chamber, a burner, an air flow tube, a gas train, and an air inlet damper, wherein the blower is coupled between the mixing chamber and the burner, wherein the mixing chamber is coupled between the blower and each of the air flow tube and the gas train, wherein a first damper plate of the air inlet damper is positioned along the air flow tube, and wherein the first damper plate has an outer perimeter with a first edge portion that is complementary to an inner surface of the air flow tube and one or more additional edge portions that define a first inwardly-extending cutout, the method comprising:

• at a first time:
• providing one or more first control signals at least indirectly from at least one control device so as to cause a blower to operate at a high speed, and to actuate the air inlet damper so that the first damper plate of the air inlet damper is rotated to an open position;
• and
• at a second time:
• providing one or more second control signals at least indirectly from the at least one control device so as to cause the blower to operate at a low speed, and to actuate the air inlet damper so that the first damper plate of the air inlet damper is rotated to a closed position, wherein, at the second time, at least some air continues to pass through the air flow tube past the first damper plate by way of the first inwardly-extending cutout so as to reach the mixing chamber,
• wherein the gas train includes each of a first gas train segment having a first gas valve and a second gas train segment having a second gas valve,
• wherein the first gas train segment is configured to have a first internal flow passageway with a first cross-section that is larger than a second cross-section of a second internal flow passageway of the second gas train segment,
• wherein, at the first time, first gas enters the mixing chamber from a first one of the first and second gas train segments of the gas train, and
• wherein, at the second time, second gas enters the mixing chamber from a second one of the first and second gas train segments of the gas train.