Modulating burner

Patent metadata

Field	Value
Publication number	US-9464805-B2
Application number	US-201313742460-A
Country	US
Kind code	B2
Filing date	Jan 16, 2013
Priority date	Jan 16, 2013
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

A modulating burner apparatus includes a variable speed blower feeding a multi-chamber burner having first and second burner chambers. A manifold system communicates the blower with the burner, and a flow control valve member is located between the blower and the second chamber of the burner. The flow control valve is configured to provide fuel and air mixture from the blower to only the first burner chamber at lower blower speeds of the blower and to both the first and second burner chambers at higher blower speeds of the blower.

First claim

What is claimed is:

1. A modulating burner apparatus, comprising:
one and only one source of pressurized pre-mixed fuel and air mixture, the source including at least one variable speed blower;
a multi-chamber burner configured to burn the pre-mixed fuel and air mixture, the burner including at least a first burner chamber and a second burner chamber; and
a flow control valve including a valve member movable between a closed position restricting flow of fuel and air mixture to the second burner chamber, and an open position allowing flow of fuel and air mixture to the second burner chamber, the flow control valve further including a biasing spring biasing the valve member toward the closed position, such that fuel and air mixture is permitted to flow from the one and only one source to the first burner chamber at lower blower speeds of the blower and to both the first and second burner chambers at higher blower speeds of the blower, wherein the valve member includes multiple flapper valve elements.

2. The apparatus of claim 1 , wherein:
the at least one variable speed blower includes one and only one blower.

3. The apparatus of claim 1 , wherein:
the at least one variable speed blower includes multiple blowers supplying a common source, the common source being the one and only one source.

4. The apparatus of claim 1 , further comprising:
a spring pre-load adjuster configured to adjust an opening force required to move the valve member from the closed position.

5. The apparatus of claim 1 , wherein:
the multi-chamber burner includes an interior wall at least partially separating the first burner chamber and the second burner chamber.

6. The apparatus of claim 1 , wherein:
the blower is a centrifugal blower having a blower output versus blower speed curve for a given flow restriction downstream of the blower; and
the first burner chamber defines a higher flow restriction and the first and second burner chambers together define a lower flow restriction, so that at the lower blower speeds when fuel and air mixture is provided to only the first burner chamber the blower output follows a first curve corresponding to the higher flow restriction, and at the higher blower speeds when fuel and air mixture is provided to both the first and second burner chambers the blower output follows a second curve corresponding to the lower flow restriction.

7. The apparatus of claim 6 , wherein:
an energy input to the burner can be continuously modulated over a lower input range modulation curve corresponding to operation of only the first burner chamber, and the energy input to the burner can be continuously modulated over a higher input range modulation curve corresponding to operation of both the first and second burner chambers together, there being an intermediate modulation curve between the lower and higher input range modulation curves, the intermediate modulation curve being steeper than the lower and higher input range modulation curves.

8. The apparatus of claim 6 , wherein:
the apparatus has an overall modulation range equal to a maximum energy input to the first and second burner chambers operating together at a maximum blower speed divided by a minimum energy input to the first burner chamber operating alone at a minimum blower speed, the overall modulation range being at least 16 to 1.

9. The apparatus of claim 8 , wherein the overall modulation range is at least 25 to 1.

10. The apparatus of claim 1 , further comprising:
a mixing chamber upstream of the blower, the mixing chamber configured to at least partially pre-mix the fuel and air mixture prior to the fuel and air mixture entering an inlet of the blower.

11. The apparatus of claim 1 , wherein:
an energy input to the burner can be continuously modulated over a lower input range modulation curve corresponding to operation of only the first burner chamber, and the energy input to the burner can be continuously modulated over a higher input range modulation curve corresponding to operation of both the first and second burner chambers together, there being an intermediate modulation curve between the lower and higher input range modulation curves, the intermediate modulation curve being steeper than the lower and higher input range modulation curves.

12. The apparatus of claim 1 , further comprising:
a heat exchanger having a water side and a hot gas side, the burner being arranged so that hot combustion gases from the burner flow through the hot gas side of the heat exchanger to heat water flowing through the water side.

13. The apparatus of claim 12 , wherein:
the heat exchanger is a fire tube heat exchanger including a plurality of fire tubes through which the hot combustion gases flow, the fire tubes being surrounded by a water chamber defining the water side of the heat exchanger.

14. The apparatus of claim 1 , wherein:
the valve member is oriented to open in a downstream direction to allow flow of the fuel and air mixture in the downstream direction into the second burner chamber at the higher blower speeds.

15. The apparatus of claim 1 , wherein:
the multiple flapper valve elements include two flapper valve elements oriented such that both flapper valve elements pivot in a downstream direction from a horizontal orientation in the closed position to a vertical orientation in the open position of the valve member.

16. The apparatus of claim 1 , wherein:
the multiple flapper valve elements include two flapper valve elements arranged such that both flapper valve elements pivot in opposite rotational directions as the valve member moves from the closed position to the open position.

17. A method of modulating energy input to a multi-stage burner, the method comprising:
(a) modulating blower speed of a variable speed blower within a lower speed range to modulate energy input to a first stage of the burner within a lower burner input range while a second stage of the burner is inoperative;
(b) opening a valve and flowing fuel and air mixture in a downstream direction past the valve into the second stage of the burner, wherein the valve includes two flapper valve elements, and the opening of the valve includes pivoting both flapper valve elements in the downstream direction in opposite rotational directions; and
(c) modulating blower speed of the variable speed blower within a higher speed range to modulate energy input to the combined first and second stages of the burner within a higher burner input range.

18. The method of claim 17 , wherein:
in step (b), the two flapper valve elements are a spring biased toward a closed position, and the valve opens as a result of outlet pressure from the blower acting on the two flapper valve elements valve and overcoming the biasing force from the spring.

19. The method of claim 17 , wherein:
during step (b), blower speed increases through a transition speed range separating the lower speed range from the higher speed range.

20. The method of claim 17 , wherein:
a highest end of the higher burner input range divided by a lowest end of the lower burner input range defines an overall turndown ratio of at least 16 to 1.

21. The method of claim 20 , wherein the overall turndown ratio is at least 25 to 1.

22. The method of claim 17 , wherein:
in step (a), the blower speed is continuously modulated within the lower speed range; and
in step (c), the blower speed is continuously modulated within the higher speed range.

23. The method of

Assignees

• Smith Corp A O
• Lochinvar Llc

Inventors

• Smelcer Jim C

Classifications

• F23N2235/06

  at the air intake · CPC title

• F23N2237/10

  High or low fire · CPC title

• F23N2233/08

  with variable speed · CPC title

• F24D11/002

  water heating system · CPC title

• F24H1/287

  with the fire tubes arranged in line with the combustion chamber · CPC title