US 12,467,624 B2
Premixing apparatus
Katsuya Noritake, Aichi (JP); and Takuya Miura, Aichi (JP)
Assigned to RINNAI CORPORATION, Aichi (JP)
Filed by RINNAI CORPORATION, Aichi (JP)
Filed on Nov. 30, 2022, as Appl. No. 18/060,229.
Claims priority of application No. 2022-022682 (JP), filed on Feb. 17, 2022.
Prior Publication US 2023/0258330 A1, Aug. 17, 2023
Int. Cl. F23D 14/02 (2006.01); C10K 3/06 (2006.01); C10L 3/00 (2006.01)
CPC F23D 14/02 (2013.01) [C10K 3/06 (2013.01); C10L 3/003 (2013.01); C10L 2290/06 (2013.01); C10L 2290/145 (2013.01); C10L 2290/24 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A premixing apparatus that mixes a fuel gas with air and supplies an air-fuel mixture to a burner through a fan, comprising:
an air supply passage on an upper side of the fan;
a gas supply passage of which a downstream end is connected to a gas suction part that is arranged in the air supply passage;
a main valve, a zero governor that regulates a secondary gas pressure to an atmospheric pressure, and a variable throttle valve, which are interposed in the gas supply passage, from an upstream side downward in sequence;
a flame rod that is exposed in flames of the burner; and
a controller,
wherein the controller is configured to carry out a first control that regulates an opening degree of the variable throttle valve so that an excess air ratio of the air-fuel mixture, which is indexed based on a flame current that is detected by the flame rod, becomes a predetermined value,
wherein:
the controller is configured to carry out a second control that, when a combustion suspension command is given and a post-purge operation in which the fan is driven in a state where the main valve is closed is performed, if the flame rod does not detect any of flame currents, the opening degree of the variable throttle valve will be held at an opening degree just before the combustion suspension command is given, and if the flame rod detects the flame current, decision that an open trouble of the main valve occurs will be made and the opening degree of the variable throttle valve will be tightened till a minimum opening-degree that is set so that the burner is extinguished,
wherein the air supply passage is provided with a butterfly valve that switches a flow resistance of the air supply passage so that, when a required combustion amount is equal to or smaller than a predetermined value, air in an amount corresponding to the required combustion amount is supplied without causing a rotational speed of the fan to decrease to a lower-limit rotational speed or slower.