1. Field of the Invention
This invention relates to an apparatus and method for sensing undesired flammable vapors at or near gaseous fuel-fired burners such as may be used for gas-fired appliances, for example residential gas-fired water heaters.
2. Description of Prior Art
Safety issues are important considerations in the design, manufacture and operation of gaseous fuel-fired burners, such as found in gas-fired appliances. This is especially true for appliances operated in a residential environment. Such appliances include residential gas-fired water heaters, gas-fired clothes dryers, furnaces, etc.
One safety issue involves a potential danger which arises when burners are exposed to flammable vapors in the ambient atmosphere external to the appliance. Such flammable vapors can cause uncontrolled propagation of flames and/or possible explosions.
An object of this invention is to provide a burner for a gas-fired appliance, capable of detecting and responding to the presence of undesired flammable vapors at, near or in the vicinity of the burner. One goal would be to turn down and/or completely shut off a gaseous fuel supply to the burner, to prevent an undesired propagation of flame and/or an explosion.
Another object of this invention is to provide a flammable vapor sensing burner which has a high degree of sensitivity to respond to even very low concentrations of detected flammable vapor.
Still another object of this invention is to provide a burner having a simplified construction with low cost, long life expectancy and enhanced durability of construction and reliability of operation.
These and other objects of this invention will become apparent in light of the present specification, the claims and the drawings.
The apparatus of this invention includes a pilot burner that operates with a main burner of a gas-fired appliance, for sensing flammable vapor present in an atmosphere ambient to the gas-fired appliance.
A first fuel gas transporting member communicates with and is connectable to a source of fuel gas. As used throughout this specification and in the claims, the phrase in communication with is intended to relate to two spaces or voids fluidically connected with or communicating with each other. The source of fuel gas may be configured for providing fuel gas, through a second fuel gas transporting member, to a main burner of the gas-fired appliance.
At least one mixer member preferably mixes fuel gas received by the first fuel gas transporting member, with air taken from the atmosphere external and ambient to the appliance, which air may contain an undesired level or amount of flammable vapor. A fuel gas-air transporting member may be operably connected to the mixer member or another suitable means for mixing fuel gas. The fuel gas-air transporting member preferably is configured for receiving the mixed fuel gas and air which may contain flammable vapor, and transporting the mixed fuel gas and air to a combustion chamber within the gas-fired appliance.
A primary pilot flame holder may be operably positionable within the combustion chamber of a gas-fired appliance. The primary pilot flame holder is preferably in communication with or operably connected to the fuel gas-air transporting member.
At least one secondary air shield preferably operates with the primary pilot flame holder, for substantially precluding access of secondary air which may be present within the combustion chamber of a gas-fired appliance, to a flame established on the primary pilot flame holder.
An igniter or another suitable ignition means is positioned near and operably associated with the at least one secondary air shield, for facilitating ignition of a main burner of a gas-fired appliance.
At least one sensor detects a change in a characteristic of a primary pilot flame established on or held by the primary pilot flame holder, such change resulting from a presence of and/or a change in an amount of, flammable vapor in the air of the atmosphere ambient to the gas-fired appliance.
The at least one sensor is sufficiently sensitive to detect a change corresponding to preselected relative amount of flammable vapor present in the air of the atmosphere ambient to the gas-fired appliance.
A controller preferably is in electrical communication with or operably associated with the at least one sensor for detecting a change in a characteristic of a flame, for controlling the operation of the source of fuel gas for a gas-fired appliance, in response to the presence of and/or the change in the amount of flammable vapor in the air of the atmosphere ambient to the gas-fired appliance. Upon demand, the controller can cease or halt the supply of fuel gas to the gas-fired appliance, for example when the at least one sensor detects a change corresponding to a threshold amount or a predetermined amount of flammable vapor in the air ambient to the gas-fired appliance.
In a preferred embodiment of this invention, the at least one mixer member for mixing fuel gas with air taken from the atmosphere external and ambient to the gas-fired appliance, which air may contain undesired flammable vapor, comprises a mixer tube positioned substantially adjacent to but spaced apart from an outlet of the first fuel gas transporting member. An inlet of the mixer tube is preferably positioned to receive a fuel gas jet from the gas nozzle. The outlet of the first fuel gas transporting member and the mixer tube are preferably operably positioned substantially external to a gas-fired appliance, so that air from the atmosphere ambient to the gas-fired appliance is entrained with the fuel gas jet from the outlet of the first fuel gas transporting member, and transported into the inlet of the mixer tube.
The at least one secondary air shield may comprise a secondary air shield, operably positioned substantially about the primary pilot flame holder, so as to substantially preclude access by secondary air within the combustion chamber of the gas-fired appliance to a pilot flame held by the primary pilot flame holder, so that any flame is substantially unaffected by any such secondary air.
The at least one sensor for detecting a change in a characteristic of a flame held by the primary pilot flame holder may comprise a thermocouple operably disposed proximate to the primary pilot flame holder for sensing the temperature at, near or in the immediate vicinity of the primary flame holder, and for providing a signal representative of the temperature which has been sensed.
In one embodiment of this invention, the controller which operates the source of fuel, in response to the presence of flammable vapor in the air ambient to the gas-fired appliance may comprise a gas valve connected directly to the thermocouple, so that as the thermocouple cools the gas valve closes.
In an alternative embodiment of this invention, the controller for controlling the operation of the source of fuel, in response to the presence of flammable vapor in the air ambient to the gas-fired appliance may comprise means for comparing the signal representative of the temperature in the immediate vicinity of the primary pilot flame holder. The means for comparing may be operably configured to compare the signal provided by the thermocouple to a predetermined range of values representative of acceptable conditions for the flame established on or held by the primary pilot flame holder. The source of fuel gas can be controlled to cease or halt the flow of fuel gas to the main burner and pilot burner when the signal provided by the thermocouple departs from a predetermined range of values representative of or corresponding to acceptable conditions for the flame held by the primary pilot flame holder.
In an alternative embodiment of this invention, in response to the presence of flammable vapor in the air ambient to the gas-fired appliance the controller may further comprise means for determining the rate of change over time of the temperature at, near or in the immediate vicinity of the primary flame holder. The determined rate of change over time of the temperature can be compared to a preselected value for the rate of change. Means may also be provided for reducing or stopping flow of the fuel gas to the main burner and/or the pilot burner when the rate of change over time of the temperature is both negative and exceeds a predetermined absolute value.
In a preferred embodiment of this invention, the at least one secondary air shield is a vertically oriented, substantially hollow cylindrical member having a primary pilot flame holder disposed at a lower end and a substantially open upper end opposite the lower end. The at least one secondary air shield can be positioned proximate the main burner flame holder of the gas-fired appliance. The means, operably associated with the at least one secondary air shield, for igniting the main burner of the gas-fired appliance comprises a secondary pilot flame holder surface, operably disposed about the substantially open upper end of the substantially hollow cylindrical member, for establishing a secondary pilot flame and for igniting fuel gas migrating from a main burner flame holder, toward establishing a main burner flame.
In another preferred embodiment of this invention, the at least one secondary air shield is a horizontally oriented, substantially hollow cylindrical member, having a primary pilot flame holder disposed at one end and a substantially closed end opposite the one end. The at least one secondary air shield can be positioned proximate the main burner flame holder of the gas-fired appliance. The means, operably associated with the at least one secondary air shield, for igniting the main burner of the gas-fired appliance may comprise a secondary pilot flame holder aperture, operably disposed in an upwardly facing region of a cylindrical side portion of the substantially hollow cylindrical member, for igniting fuel gas migrating from a main burner flame holder, toward establishing a main burner flame.
In still another preferred embodiment of this invention, the at least one secondary air shield is a substantially hollow, cylindrical member, having a primary pilot flame holder positioned at one end. The at least one secondary air shield can be positioned proximate the main burner flame holder of the gas-fired appliance. The means, operably associated with the at least one secondary air shield member, for igniting the main burner of the gas-fired appliance comprises at least one flash tube member, operably associated with or in communication with the substantially hollow cylindrical member, for receiving fuel gas from a main burner flame holder and for conducting the fuel gas toward a primary pilot flame held by the primary pilot flame holder, toward igniting the fuel gas from the main burner flame holder and thus establishing the main burner flame.
This invention also relates to a method for sensing flammable vapor present in the atmosphere ambient to the gas-fired appliance, and for controlling operation of the gas-fired appliance in response to a presence of or an undesired level of a flammable vapor.
A first fuel gas transporting member is connected to or communicates with a source of fuel gas. The source of fuel gas can be configured to provide fuel gas through a second fuel gas transporting member, to the main burner of the gas-fired appliance. Fuel gas received by the first fuel gas transporting member is mixed, using least one mixer member, with air taken from the atmosphere external and ambient to the appliance, which air may contain flammable vapor.
The mixed fuel gas and air is transported or flows to a combustion chamber within the gas-fired appliance, such as through a fuel gas-air transporting member. A primary pilot flame holder operably positionable within the combustion chamber of the gas-fired appliance is connected to or communicates with the fuel gas-air transporting member.
At least one secondary air shield is used to substantially preclude access of secondary air which may be present within the combustion chamber of the gas-fired appliance to the flame established on or held by the primary pilot flame holder.
At least one sensor is used to detect a change in a characteristic of a flame held by the primary pilot flame holder, such change resulting from the presence of and/or the change in the amount of flammable vapor in the air from the atmosphere ambient to the gas-fired appliance. The change corresponds to a preselected relative amount of flammable vapor present in the air from the atmosphere ambient to the gas-fired appliance.
A controller is used to control the operation of the source of fuel gas for a gas-fired appliance, in response to the presence of and/or the change in the amount of flammable vapor in the air from the atmosphere ambient to the gas-fired appliance. The supply of the fuel gas to the gas-fired appliance is ceased or halted when the at least one sensor detects a change corresponding to a predetermined amount of flammable vapor in the air ambient to the gas-fired appliance.
In one preferred embodiment, a mixer tube is positioned substantially adjacent to but also spaced apart from an outlet of the first fuel gas transporting member. An inlet of the mixer tube can be positioned to receive the fuel gas jet from the gas nozzle.
The outlet of the first fuel gas transporting member and the mixer tube is preferably positioned substantially external to the gas-fired appliance, so that air from the atmosphere ambient to the gas-fired appliance is entrained with the fuel gas jet from the outlet of the first fuel gas transporting member, and directed or transported into the inlet of the mixer tube.
A secondary air shield can be positioned substantially about the primary pilot flame holder, so as to substantially preclude access of secondary air within the combustion chamber of the gas-fired appliance to the pilot flame established on or held by the primary pilot flame holder, so that the pilot flame is substantially unaffected by any such secondary air.
A thermocouple can be positioned proximate to the primary pilot flame holder for sensing the temperature at, near or in the immediate vicinity of the primary pilot flame holder, and for providing a signal representative of the temperature of the immediate vicinity of the primary pilot flame holder.
The thermocouple can be connected directly to a gas valve, so that as the thermocouple cools and reaches a certain level the gas valve then closes.
The signal representative of the temperature at, near or in the immediate vicinity of the primary pilot flame holder is preferably compared to a predetermined range of values representative of or corresponding to acceptable conditions for the flame held by the primary pilot flame holder.
The source of the fuel gas ceases or halts fuel gas flow to the main burner and/or the pilot burner when the signal provided by the thermocouple departs from or is different than the predetermined range of values.
The rate of change overtime of the temperature at, near or in the immediate vicinity of the primary flame holder is determined and compared to a preselected value for the rate of change over time, of the temperature.
The source of the fuel gas then ceases or halts fuel gas flow to the main burner and/or the pilot burner preferably when the rate of change over time of the temperature is both negative and exceeds a predetermined absolute value.