Liquid heaters and vaporizers – Stand boiler – And condition responsive feature
Reexamination Certificate
2001-07-12
2002-07-23
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Stand boiler
And condition responsive feature
C122S017100
Reexamination Certificate
active
06422178
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly provides a gas-fired water heater with a combustion chamber having incorporated therein a specially designed louvered flame arrestor plate through which combustion air is operatively flowed into the chamber.
Gas-fired residential and commercial water heaters are generally formed to include a vertical cylindrical water storage tank with a gas burner disposed in a combustion chamber below the tank. The burner is supplied with a fuel gas through a gas supply line, and combustion air through one or more air inlet openings providing communication between ambient air and the interior of the combustion chamber.
In order to permit the flow of combustion air into the combustion chamber, while at the same time prevent the outflow of flames from the combustion chamber, various proposals have been made to provide the combustion chamber with an exterior wall portion having a spaced series of flame quenching openings formed therein, such openings being configured to permit the ingress of combustion air into the combustion chamber, while at the same time preventing the passage of combustion chamber flames outwardly through these openings. Accordingly, in the event that extraneous flammable vapors enter the combustion chamber with combustion air inwardly traversing these flame quenching openings, flames resulting from ignition of the incoming flammable vapor will be contained within the combustion chamber. An example of one previously proposed perforated flame arrestor plate structure used in this manner as an exterior wall portion of a gas-fired water heater combustion chamber is illustrated and described in U.S. Pat. No. 5,941,200 to Boros et al.
While perforated flame quenching arrestor plates of this general type are generally well suited for their intended purpose, arrestor plates of conventional constructions and configurations have certain known limitations and disadvantages. For example, they can be difficult to design in a manner providing uniform combustion air inlet flow over their entire perforated area, may be susceptible to uneven temperature distributions along their surfaces, and may also be prone to becoming partially clogged with lint and other airborne debris, thereby requiring periodic cleaning during the operational lifetime of their associated water heater.
In view of these limitations it would be desirable to provide a fuel-fired heating appliance, such as a water heater, having an improved perforated combustion chamber flame arrestor plate that eliminates or at least substantially alleviates the above-mentioned limitations and disadvantages of conventionally configured flame arrestor plates. It is to this goal that the present invention is primarily directed.
SUMMARY OF THE INVENTION
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a specially designed flame arrestor plate is illustratively incorporated in a fuel-fired heating apparatus which is representatively a gas-fired water heater, but could be a variety of other types of fuel-fired heating apparatus such as, for example, a furnace or boiler. The fuel-fired heating apparatus comprises a combustion chamber thermally communicatable with a fluid to be heated, and a burner operatively disposed within the combustion chamber. The flame arrestor plate structure has a generally planar body, representatively of a suitable metal material, and illustratively defines a bottom wall portion of the combustion chamber. The body has a series of louvered openings therein which are configured as flame quenching openings that permit combustion air to flow therethrough into the combustion chamber and substantially preclude flame passage outwardly therethrough from the combustion chamber.
In a preferred embodiment of the flame arrestor plate structure, each of the louvered openings is bordered by a bounding portion of the body including first and second spaced apart body wall segments, with each louvered opening having an inlet on a first side of the body, and an outlet disposed on a second side of the body and having an area substantially smaller than the area of the inlet. The first body wall segment is angled relative to the plane of the body and has a generally planar side surface and a first corner edge that partially bound the louvered opening, the second body wall segment has a generally planar end surface and a second corner edge that partially bound the louvered opening, and the first and second corner edges extend along the outlet in a spaced apart parallel relationship. Representatively, each louvered opening is elongated in a direction parallel to its associated first and second corner edges.
According to a first operational feature of the flame arrestor plate, each of the bounding portions of the body is operative to create counter-rotating vortices in combustion air exiting its associated louvered opening and entering the combustion chamber. According to a second operational feature of the flame arrestor plate, each bounding portion is operative to create in combustion air flowing through its associated louvered opening into the combustion chamber a laminar flow area (i.e., with a Reynold's number less than or equal to about 2100) extending along the generally planar side surface of the first body wall segment, a turbulent flow area (i.e., with a Reynold's number greater than about 4000) extending along the generally planar end surface of the second body wall segment, and a transitional flow area (i.e., with a Reynold's number of from about 2100 to about 4000) disposed between the laminar flow area and the turbulent flow area. According to a third operational feature of the flame arrestor plate, each bounding portion is operative to create at least two directional changes in combustion air inwardly traversing its associated louvered opening.
The turbulence created in air discharged from the louvered openings into the combustion chamber substantially facilitates the prevention of clogging of the openings with lint or other particulate matter entrained in the incoming combustion air. This prevention of lint/particulate clogging of the louvered inlet openings is preferably augmented by positioning the first and second corner edges of each opening in a spaced apart, parallel relationship with the edges being separated, in a direction parallel to the plane of the plate body, by a small gap which permits particulates within the combustion chamber to fall vertically through the openings during non-firing periods of the fuel-fired heating appliance.
According to a fourth operational feature of the flame arrestor plate, the configuration of the louvered openings creates a pressure in combustion air exiting the openings into the combustion chamber which is substantially lower than combustion air entering the openings. This facilitates desirably even combustion air inflow, at both normal and above normal firing rates, across the perforated area of the plate body to accordingly provide a substantially uniform temperature along the plate body and an even pattern of foreign material (such as lint) distribution along the unperforated bottom side surface area of the plate body.
In addition to the above-mentioned particulate fall-through gap, various other configurational features are also illustratively incorporated into the flame arrestor plate, in a preferred embodiment thereof. Such configurational features include at each louvered opening (1) the outward sloping of the generally planar end surface of the first body wall segment away from the second body wall segment at an acute angle relative to a reference plane transverse to the plane of the plate body; (2) the provision of each of the louvered openings with a ratio of interior surface area to outlet opening area which is greater than about 120; and (3) the configuring of each louvered opening in a manner such that it has a total flow volume defined by a
Kidd Larry D.
Lannes Eric M.
Taylor Mark A.
Konneker & Smith P.C.
The Water Heater Industry Joint Research and Development Consort
Wilson Gregory
LandOfFree
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