Gas-fired heaters with burners which operate without secondary air and have a substantially sealed combustion chamber

• US 6,019,069 A
• Filed: 09/18/1997
• Issued: 02/01/2000
• Est. Priority Date: 12/30/1991
• Status: Expired due to Fees

• Current Assignee: Bowin Technology Pty Limited
• Original Assignee: Bowin Technology Pty Limited
• Inventors: Joyce, John V.
• Primary Examiner(s): DORITY, CARROLL B
• Application Number:
  US08/932,880
• Time in Patent Office: 866 Days
• Field of Search: 431/328, 431/329, 122/14, 122/17, 122/19, 126/361, 126/90 R, 126/92 R, 126/110 D
• US Class Current: 122/18.31
• CPC Class Codes: F23C 5/00 Disposition of burners with respect to the combustion chamber or to one another; Mounting of burners in combustion apparatus F23C1/00, F23C15/00 take precedence
• CPC Class Codes: F23D 14/04 induction type, e.g. Bunsen burner
• CPC Class Codes: F23M 20/005 Noise absorbing means
• CPC Class Codes: F24H 1/205 with furnace tubes
• CPC Class Codes: F24H 3/0488 using fluid fuel
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]

Abstract

A gas-fired burner apparatus includes a porous combustion surface disposed in a combustion chamber substantially sealed to prevent entry of secondary air. A subatmospheric pressure is maintained in the combustion chamber by a natural or aspirated draft. The subatmospheric pressure cooperates with an aspirating flow of fuel to the burner apparatus to provide an increased flow of primary combustion air which reduces the combustion temperature and the emission of pollutants. Alternatively, the subatmospheric pressure may be used to achieve a given flow of primary combustion air with a reduced combustion surface area. Water heater and room heater applications of the burner apparatus are illustrated.

Claims

1. A gas-fired heater for providing substantially convective heat transfer, said heater including a housing having a burner apparatus mounted therein, said burner apparatus including air/fuel supply means for receiving a flow of gaseous fuel from a source thereof and operating in response to the flow of fuel to aspirate and combine a primary combustion air component therewith to form a combustible air/fuel mixture for delivery to a burner unit, said air component being greater than from about 110% to about 200% of that required for theoretically complete combustion, said burner unit including a porous combustion surface, a combustion chamber containing said combustion surface, said combustion chamber being substantially sealed to prevent the entrance of secondary air and including a discharge opening for products of combustion, said discharge opening being in fluid communication with the environment and being arranged to produce a subatmospheric pressure in said combustion chamber in response to the flow of the products of combustion into the environment, said subatmosphric pressure causing said air/fuel mixture to flow through said combustion surface at a rate which exceeds the flow rate that would exist if the combustion chamber was at atmospheric pressure, said housing including an air inlet and an air outlet for respectively taking in circulating air from a space to be temperature conditioned and for discharging the heated circulating air together with the products of combustion into the space to be temperature conditioned, said burner apparatus having said combustion chamber discharge opening in communication with said air outlet.

2. The heater of claim 1, wherein the area of the combustion surface is reduced for a given heat energy input and burner rating as compared with the area of the combustion surface required for the same heat energy input and burner rating if the combustion chamber was at atmospheric pressure.

3. The heater of claim 2, wherein the reduction in area of the combustion surface is by a factor of more than 3.

4. The heater of claim 1, wherein said air/fuel supply means comprises a duct having an inlet end for receiving said flow of fuel and aspirating said primary combustion air component from environmental air, and an outlet end for discharging said combustible air/fuel mixture in said burner apparatus.

5. The heater of claim 4, wherein said duct is a venturi.

6. A water heater including a tank defining a water chamber and having a burner apparatus mounted below said water chamber, said burner apparatus including air/fuel supply means for receiving a flow of gaseous fuel from a source thereof and operating in response to the flow of fuel to aspirate and combine a primary combustion air component therewith to form a combustible air/fuel mixture for delivery to a burner unit, said air component being from about 110% to about 200% of that required for theoretically complete combustion, said burner unit including a porous combustion surface, a combustion chamber containing said combustion surface, said combustion chamber and water chamber including a common wall portion therebetween, said combustion chamber being substantially sealed to prevent the entrance of secondary air and including a discharge opening for products of combustion, said discharge opening being in fluid communication with the environment and being arranged to produce a subatmospheric pressure in said combustion chamber in response to the flow of the products of combustion into the environment, said subatmospheric pressure causing said air/fuel mixture to flow through said combustion surface at a rate which exceeds the flow rate that would exist if the combustion chamber was at atmospheric pressure upon operation of said burner at a combustion temperature in the range of from about 600°

to about 900°

C., and a combustion loading in the range of from about 500 to 2000 Mjoules/m² hr.

7. The water heater of claim 6, wherein said common wall portion is a dome-shaped upwardly concave wall providing a lower end surface of said water chamber and an upper surface of said burner combustion chamber.

8. The water heater of claim 7, wherein the products of combustion flow in a substantially uninterrupted manner upwardly along said concave wall to said discharge opening and through said vent to establish said subatmospheric pressure in said combustion chamber without requiring powered mechanical flow producing devices.

9. A room heater including a housing having a burner apparatus mounted therein, said burner apparatus including air/fuel supply means for receiving a flow of gaseous fuel from a source thereof and operating in response to the flow of fuel to aspirate and combine a primary combustion air component therewith to form a combustible air/fuel mixture for delivery to a burner unit, said air component being from about 110% to about 200% of that required for theoretically complete combustion, said burner unit including a porous combustion surface, a combustion chamber containing said combustion surface, said combustion chamber being substantially sealed to prevent the entrance of secondary air and including a discharge opening for products of combustion, said discharge opening being in fluid communication with the environment and being arranged to produce a subatmospheric pressure in said combustion chamber in response to the flow of the products of combustion into the environment, said subatmospheric pressure causing said air/fuel mixture to flow through said combustion surface at a rate which exceeds the flow rate that would exist if the combustion chamber was at atmospheric pressure upon operation of said burner at a combustion temperature in the range of from about 600°

to about 900°

C., a combustion loading in the range of from about 500 to 2000 MJoules/m² hr, said housing including an air inlet and an air outlet for respectively taking in circulating air from a space to be temperature conditioned and for discharging the heated circulating air together with the products of combustion into the space to be temperature conditioned, said burner apparatus having said combustion chamber discharge opening in communication with said air outlet.

10. The room heater of claim 9, wherein said circulating air flows past said combustion chamber discharge opening and aspirates products of combustion from said combustion chamber into the flow of circulating air.

11. The room heater of claim 10, wherein said combustion chamber includes a wall and the room heater further includes a bypass air passage containing said flow of circulating air within said housing separated from said combustion chamber by said combustion chamber wall, a powered blower producing a substantial bypass flow of said circulating air from said air inlet through said bypass air passage to a bypass air passage discharge opening operating to provide a jet of circulating air flowing past said combustion chamber discharge opening to said room heater outlet, said jet of circulating air entraining by aspiration sufficient products of combustion from said combustion chamber to produce said subatmospheric pressure in said combustion chamber.

12. The room heater of claim 11, wherein said bypass wall provides a heat exchange surface between said combustion chamber and bypass air passage causing preliminary heating of said bypass air before it reaches said discharge nozzle.

13. A water heater comprising a tank defining a vertically extending generally cylindrical water chamber, a dome shaped upwardly concave wall forming the lower end of said water chamber and the upper surface of a combustion chamber, a flue stack extending vertically along the center of said water chamber open at its lower end to said combustion chamber through the central portion of said concave wall and at its upper end to the environment above said water chamber, a burner unit including a porous combustion surface, said porous combustion surface being located in said combustion chamber, an air duct open to said burner unit, and a supply of gaseous fuel connected to said air duct operating to induce an amount of primary air into said burner unit sufficient to establish a greater than stoichiometric mixture, said combustion chamber being substantially sealed except for said air duct and the lower end of said flue stack so that secondary air does not enter said combustion chamber, the combustion gases resulting from combustion of said gaseous fuel and primary air flowing in a substantially uninterrupted manner upwardly along said concave surface to said flue stack and through said flue stack to establish a subatmospheric pressure in said combustion chamber without requiring powered mechanical flow producing devices, said subatmospheric pressure causing a flow of gases through said combustion surface at a rate which exceeds the rate of flow that would exist if the combustion chamber were open to atmospheric pressure.

14. A water heater as set forth in claim 13, wherein said dome-shaped upwardly concave wall operates to funnel said combustion gases into said flue stack, said concave wall providing substantially convective heat exchange between said combustion gases and said water chamber.

15. A water heater as set forth in claim 13, wherein said combustion chamber provides a lower wall, and a layer of insulation is positioned along said lower wall to reduce noise during combustion and to reduce heat losses through said lower wall.

16. A water heater as set forth in claim 13, wherein said air duct operates to deliver to said burner unit at least about 120% of the amount of air required to cause complete combustion of said fuel.

17. A water heater as set forth in claim 13, wherein said combustion occurs at a temperature between 600°

C. and 900°

C.

18. A water heater as set forth in claim 13, wherein said air duct is a venturi.

19. A method of operating a gas-fired heater for providing substantially convective heat transfer, said heater comprising a housing including an air inlet, an air outlet and containing a burner apparatus having a fuel supply means for supplying a flow of gaseous fuel, aspirating and combining primary combustion air in an air duct means in response to said flow of fuel to form a combustible air/fuel mixture for delivery to a burner unit, said air component being from about 110% to about 200% of that required for theoretically complete combustion, passing said air/fuel mixture upwardly through a porous combustion surface of said burner unit and into a combustion chamber having a discharge opening for products of combustion, combusting said air/fuel mixture at or near said combustion surface in said combustion chamber at a combustion temperature in the range of from about 600°

C. to about 900°

C., substantially sealing said combustion chamber to prevent the entrance of secondary air and removing the products of combustion from said combustion chamber to produce a subatmospheric pressure in said combustion chamber, flowing said air/fuel mixture under the influence of said subatmospheric pressure through said combustion surface at a rate which exceeds the flow rate that would exist if the combustion chamber was at atmospheric pressure for a given heat energy input and burner rating to provide a combustion loading in the range of from about 500 to about 2000 Mjoules/m² hr, circulating air from a space to be temperature conditioned into said air inlet and heating said circulating air in said housing with heat transfer from said burner apparatus, and discharging said heated circulating air together with said products of combustion through said air outlet into said space to be temperature conditioned.

20. The method of claim 19, including the step of removing said products of combustion from said combustion chamber by aspirating and entraining said products of combustion in a flow of circulating air.