# US 9,038,576 B2 · Ultra low NOx burner using distributed direct fuel injection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,038,576 B2 - Document ID: US9038576B2 - Status: Granted - Kind: B2 - Application number: 13/899,960 - Filed: 2013-05-22 - Published: 2014-11-27 - Granted: 2015-05-26 - Earliest claimed: 2013-05-22 - Assignees: Plum Combustion, Inc. - Applicants: Yedidia Neumeier; David S. Neff; Michael Pratte - Inventors: Yedidia Neumeier; David S. Neff; Michael Pratte - Web page: https://patentgrep.com/patent/US9038576B2 ## CPC - F23D 14/70: Baffles or like flow-disturbing devices - F23D 14/02: Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone - F24H 1/186: {using fluid fuel} - F24H 1/205: {with furnace tubes} - F23D 2203/1017: curved - F23D 2203/103: using screens - F23D: BURNERS - F24H: FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL (steam generation F22) ## Abstract A burner box includes a housing, a fuel tube and a porous heat dissipating surface. The housing is bounded by a sidewall and has a top and an opposite bottom that are each open so that the sidewall defines an open passage that allows unimpeded vertical airflow. The fuel tube extends into the passage and defines a plurality of spaced apart orifices that distribute fuel into the open passage. The fuel tube is at a distance from the top of the housing so that substantially all of the fuel is entrained by the combustion air before the fuel reaches the top. The heat dissipating surface is disposed across the top of the housing and supports a flame. The heat dissipating surface includes enough open area so that the fuel/air mixture passes through the porous heat dissipating surface unimpeded. The heat dissipating surface dissipates heat from the flame and prevents flashback. ## Claims ### Claim 1 A burner box, comprising: (a) a housing bounded by at least one sidewall, the housing having a top and an opposite bottom, the top and the bottom each open so that the sidewall defines an open passage that is configured to allow substantially unimpeded vertical convective airflow upwardly from the bottom so that 100% of all combustion air flows upwardly from the open bottom; and (b) a fuel tube extending into the passage defined by housing, the fuel tube having an inner cavity that is confined by a tube wall and that is in fluid communication with a fuel connection port outside of the housing, the tube wall defining a plurality of spaced apart orifices passing therethrough that are configured to distribute fuel received through the fuel connection into the open passage defined by the sidewall of the housing, the fuel tube disposed at a distance from the top of the housing so that substantially all of the fuel distributed from the fuel tube is entrained by the combustion air before the fuel reaches the top of the housing, thereby forming a substantially homogenous fuel/air mixture; and (c) a porous heat dissipating surface disposed across the top of the housing, the porous heat dissipating surface configured to support a flame resulting from combustion of the fuel/air mixture, the porous heat dissipating surface including enough open area so that the fuel/air mixture passes through the porous heat dissipating surface substantially unimpeded, the porous heat dissipating surface configured to dissipate heat from the flame and to prevent flashback of the flame into the housing, wherein the fuel tube comprises a straight tube that extends from a first side of the housing to an opposite second side of the housing and wherein the orifices are evenly spaced apart along two spaced apart rows that run the length of the tube. ### Claim 2 (depends on 1) The burner box of claim 1, wherein the fuel tube has a cross-sectional area and wherein the orifices subtend from 20% to 50% of the tube cross-sectional area. ### Claim 3 (depends on 1) The burner box of claim 1, wherein the porous heat dissipating surface comprises a metal mesh. ### Claim 4 (depends on 3) The burner box of claim 3, wherein the mesh is a low resistance mesh having at least a 65% open area. ### Claim 5 (depends on 3) The burner box of claim 3, wherein the mesh is a 24×24 mesh with a 0.0075 inch diameter wire. ### Claim 6 (depends on 3) The burner box of claim 3, further comprising at least one support that is configured to maintain the metal mesh with an upwardly curved shape. ### Claim 7 (depends on 1) The burner box of claim 1, wherein the housing has a rectangular plan shape with a first pair of walls that are separated by a first distance and a second pair of walls that are separated by a second distance, in which the first distance is greater than the second distance and wherein the tube has a length that is substantially the first distance. ### Claim 8 (depends on 7) The burner box of claim 7, wherein a first one of the first pair of walls comprise an opening passing therethrough through which the fuel tube extends, an end of the fuel tube affixed to a second one of the first pair of walls so as to hold the fuel tube in an alignment that results in fuel injection in a substantially upward direction. ### Claim 9 (depends on 1) The burner box of claim 1, further comprising a flame arrestor disposed adjacent to the bottom of the housing. ### Claim 10 (depends on 9) The burner box of claim 9, wherein the flame arrestor comprises a metal mesh. ### Claim 11 A water heater, comprising: (a) a water tank configured to hold water therein and having a bottom surface and defining a flue passing upwardly therethrough; (b) a combustion space surrounded by an outer wall and bound by the bottom surface of the water tank so that the combustion space is disposed beneath the bottom surface of the water tank, the combustion space in fluid communication with the flue, the combustion space having a bottom area configured to allow air to pass upwardly therethrough substantially unimpeded; (c) a burner box assembly disposed in the combustion space and including: (i) a housing bounded by at least one sidewall, the housing having a top and an opposite bottom, the top and the bottom each open so that the sidewall defines an open passage that is configured to allow substantially unimpeded vertical convective airflow upwardly from the bottom so that 100% of all combustion air flows upwardly from the open bottom; and (ii) a fuel tube extending into the passage defined by housing, the fuel tube having an inner cavity that is confined by a tube wall and that is in fluid communication with a fuel connection port outside of the housing, the tube wall defining a plurality of spaced apart orifices passing therethrough that are configured to distribute fuel received through the fuel connection into the open passage defined by the sidewall of the housing, the fuel tube disposed at a distance from the top of the housing so that substantially all of the fuel distributed from the fuel tube is entrained by the combustion air before the fuel reaches the top of the housing, thereby forming a substantially homogenous fuel/air mixture; and (iii) a porous heat dissipating surface disposed across the top of the housing, the porous heat dissipating surface configured to support a flame resulting from combustion of the fuel/air mixture, the porous heat dissipating surface including enough open area so that the fuel/air mixture passes through the porous heat dissipating surface substantially unimpeded, the porous heat dissipating surface configured to dissipate heat from the flame and to prevent flashback of the flame into the housing; and (d) a plenum disposed within the combustion space and around the burner box assembly, the plenum having at least one outer dimension configured to interfere with acoustic harmonics in the combustion space, wherein the burner box assembly is configured to support the flame so as to heat water in the water tank through the bottom surface of the water tank and the flue 14, wherein the fuel tube comprises a straight tube that extends from a first side of the housing to an opposite second side of the housing and wherein the orifices are evenly spaced apart along two spaced apart rows that run the length of the tube. ### Claim 12 (depends on 11) The water heater of claim 11, further comprising: (a) a base disposed under the burner box assembly that is configured to allow air to pass freely upwardly therethrough; and (b) a radiation shield plate configured to shield an area under the water heater from heat generated by the burner box assembly. ### Claim 13 (depends on 11) The water heater of claim 11, wherein the fuel tube has a cross-sectional area and wherein the orifices subtend from 20% to 50% of the tube cross-sectional area. ### Claim 14 (depends on 11) The water heater of claim 11, wherein the porous heat dissipating surface comprises a metal mesh. ### Claim 15 (depends on 14) The water heater of claim 14, wherein the mesh is a low resistance mesh having at least a 65% open area. ### Claim 16 (depends on 14) The water heater of claim 14, wherein the mesh is a 24×24 mesh with a 0.0075 inch diameter wire. ### Claim 17 (depends on 14) The water heater of claim 14, further comprising at least one support that is configured to maintain the metal mesh with an upwardly curved shape. ### Claim 18 (depends on 11) The water heater of claim 11, wherein the housing has a rectangular plan shape with a first pair of walls that are separated by a first distance and a second pair of walls that are separated by a second distance, in which the first distance is greater than the second distance and wherein the tube has a length that is substantially the first distance and wherein a first one of the first pair of walls comprise an opening passing therethrough through which the fuel tube extends, an end of the fuel tube affixed to a second one of the first pair of walls so as to hold the fuel tube in an alignment that results in fuel injection in a substantially upward direction. ### Claim 19 (depends on 11) The water heater of claim 11, further comprising a flame arrestor including a metal mesh disposed adjacent to the bottom of the housing. ### Claim 20 A burner box, comprising: (a) a housing bounded by at least one sidewall, the housing having a top and an opposite bottom, the top and the bottom each open so that the sidewall defines an open passage that is configured to allow substantially unimpeded vertical convective airflow upwardly from the bottom so that 100% of all combustion air flows upwardly from the open bottom; and (b) a fuel tube extending into the passage defined by housing, the fuel tube having an inner cavity that is confined by a tube wall and that is in fluid communication with a fuel connection port outside of the housing, the tube wall defining a plurality of spaced apart orifices passing therethrough that are configured to distribute fuel received through the fuel connection into the open passage defined by the sidewall of the housing, the fuel tube disposed at a distance from the top of the housing so that substantially all of the fuel distributed from the fuel tube is entrained by the combustion air before the fuel reaches the top of the housing, thereby forming a substantially homogenous fuel/air mixture; and (c) a porous heat dissipating surface disposed across the top of the housing, the porous heat dissipating surface configured to support a flame resulting from combustion of the fuel/air mixture, the porous heat dissipating surface including enough open area so that the fuel/air mixture passes through the porous heat dissipating surface substantially unimpeded, the porous heat dissipating surface configured to dissipate heat from the flame and to prevent flashback of the flame into the housing, wherein the housing has a rectangular plan shape with a first pair of walls that are separated by a first distance and a second pair of walls that are separated by a second distance, in which the first distance is greater than the second distance and wherein the tube has a length that is substantially the first distance, and wherein a first one of the first pair of walls comprise an opening passing therethrough through which the fuel tube extends, an end of the fuel tube affixed to a second one of the first pair of walls so as to hold the fuel tube in an alignment that results in fuel injection in a substantially upward direction. ### Claim 21 (depends on 20) The burner box of claim 20, wherein the fuel tube has a cross-sectional area and wherein the orifices subtend from 20% to 50% of the tube cross-sectional area. ### Claim 22 (depends on 20) The burner box of claim 20, wherein the porous heat dissipating surface comprises a metal mesh. ### Claim 23 (depends on 22) The burner box of claim 22, wherein the mesh is a 24×24 mesh with a 0.0075 inch diameter wire. ### Claim 24 (depends on 20) The burner box of claim 20, wherein the fuel tube is bent into a shape that is a selected one of circular or semicircular.