U.S. patent application number 15/845686 was filed with the patent office on 2018-06-21 for performance of a gas-fired appliance by use of fuel injection technology.
The applicant listed for this patent is A. O. SMITH CORPORATION. Invention is credited to Billy A. Batey, Benjamin J. Bolton, Jim C. Smelcer.
Application Number | 20180172316 15/845686 |
Document ID | / |
Family ID | 62556291 |
Filed Date | 2018-06-21 |
United States Patent
Application |
20180172316 |
Kind Code |
A1 |
Smelcer; Jim C. ; et
al. |
June 21, 2018 |
PERFORMANCE OF A GAS-FIRED APPLIANCE BY USE OF FUEL INJECTION
TECHNOLOGY
Abstract
A water heater including a tank configured to hold a fluid, a
burner configured to manipulate a temperature of the fluid within
the tank, one or more sensors configured to sense one or more
characteristics of the burner, a fuel injector position upstream of
the burner, and a controller. The controller includes an electronic
processor and a memory. The controller is configured to receive one
or more signal from the one or more sensors corresponding to the
one or more characteristics, and control the fuel injector based on
the one or more signals.
Inventors: |
Smelcer; Jim C.; (Hermitage,
TN) ; Bolton; Benjamin J.; (Elm Grove, WI) ;
Batey; Billy A.; (Watertown, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
A. O. SMITH CORPORATION |
Milwaukee |
WI |
US |
|
|
Family ID: |
62556291 |
Appl. No.: |
15/845686 |
Filed: |
December 18, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62436936 |
Dec 20, 2016 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24H 1/186 20130101;
F23N 5/187 20130101; F23N 2239/04 20200101; F23N 1/045 20130101;
F24H 9/2035 20130101; F23N 1/025 20130101; F23N 1/022 20130101;
F24H 9/1836 20130101; F23N 5/184 20130101; F23N 2241/04 20200101;
F23D 14/02 20130101 |
International
Class: |
F24H 9/20 20060101
F24H009/20; F24H 1/18 20060101 F24H001/18; F24H 9/18 20060101
F24H009/18; F23N 1/02 20060101 F23N001/02 |
Claims
1. A water heater comprising: a tank configured to hold a fluid; a
burner configured to manipulate a temperature of the fluid within
the tank; one or more sensors configured to sense one or more
characteristics of the burner; a fuel injector positioned upstream
of the burner; and a controller having an electronic processor and
a memory, the controller configured to receive one or more signals
from the one or more sensors corresponding to the one or more
characteristics, and control the fuel injector based on the one or
more signals.
2. The water heater of claim 1, wherein the controller controls the
fuel injector in order to maintain a substantially constant
air/fuel ratio in the combustion chamber.
3. The water heater of claim 1, wherein the controller controls the
fuel injector using a pulse-width modulated signal.
4. The water heater of claim 1, further comprising a fuel injector
array.
5. The water heater of claim 4, wherein the controller is further
configured to control the first and second fuel injectors in order
to maintain a substantially constant air/fuel ratio in the
combustion chamber.
6. The water heater of claim 1, wherein the one or more sensors
include at least one from a group consisting of an air mass flow
sensor, an oxygen sensor, and an air/fuel ratio sensor.
7. The water heater of claim 1, further comprising a blower.
8. The water heater of claim 7, wherein the blower is configured to
provide an air/fuel mixture to the burner.
9. A method of operating a water heater, the method comprising:
manipulating, via a burner, a temperature of a fluid; sensing, via
a sensor, a characteristics of the burner; injecting, via a fuel
injector, a fuel upstream the burner; supplying, via a blower, an
air/fuel mixture to the burner; and controlling, via a controller,
the fuel injector based on the characteristic.
10. The method of claim 9, further comprising controlling, via the
controller, a blower to provide an air/fuel mixture to the
burner.
11. The method of claim 9, wherein the step of controlling the fuel
injector includes controlling an opening time and a closing time of
the fuel injector.
12. The method of claim 9, wherein the characteristics includes at
least one selected from the group consisting of an air flow, an
oxygen level, and an air/fuel ratio.
13. A gas-fired appliance comprising: a burner configured to
manipulate a temperature of the fluid within the tank; a fuel
injector configured to inject fuel upstream of the combustion
chamber; a blower configured to provide an air/fuel mixture to the
burner; a sensor configured to sense a characteristic of the
burner; and a controller having an electronic processor and a
memory, the controller configured to receive a signal from the
sensor corresponding to characteristic of the burner, and control
the fuel injector and the blower based on the signal.
14. The gas-fired appliance of claim 13, wherein the burner is
configured to manipulate a temperature of a fluid.
15. The gas-fired appliance of claim 14, wherein the fluid is
contained within a tank.
16. The gas-fired appliance of claim 13, wherein the controller
controls the fuel injector and the blower in order to maintain a
substantially constant air/fuel ratio in the combustion
chamber.
17. The gas-fired appliance of claim 13, wherein the controller
controls the fuel injector using a pulse-width modulated
signal.
18. The gas-fired appliance of claim 13, further comprising a fuel
injector array.
19. The gas-fired appliance of claim 18, wherein the controller is
further configured to control the first and second fuel injectors
in order to maintain a substantially constant air/fuel ratio in the
combustion chamber.
20. The gas-fired appliance of claim 13, wherein the one or more
sensors include at least one from a group consisting of an air mass
flow sensor, an oxygen sensor, and an air/fuel ratio sensor.
Description
RELATED APPLICATIONS
[0001] The application claims priority to U.S. Provisional Patent
Application 62/436,936, filed Dec. 20, 2016, the entire contents of
which are hereby incorporated.
FIELD
[0002] Embodiments relate to gas-fired appliances (such as but not
limited to, water heaters) including fuel injection systems.
SUMMARY
[0003] Gas-fired appliances may incorporate gas trains designed for
gaseous fuel flow control. The gas flow control may be a pneumatic
device, relying on an inlet gas supply pressure and a pressure
differential across the regulator diaphragm within the gas control
to closely regulate a preset gas flow into the burner. In addition,
certain gas trains may include pneumatic devices that allow the gas
flow to vary with respect to the speed of a blower providing
combustion air to the burner such that the quantity of air mixed
with the quantity of gas remains constant (i.e., a constant
air/fuel ratio). However, these gas trains do not compensate for
internal and external influences that the appliance may experience.
In such cases, the appliance may not operate at peak performance,
or may not operate until manual adjustments are made to the system
components. For example, environmental changes from the effect of
high altitude, increased vent length, prevailing wind conditions
impacting the vent termination, subzero outside combustion air
temperature, and/or transient changes in gas properties can have an
adverse effect on the ability of traditional pneumatic controls to
provide the desired constant air/fuel ratio to the burner.
[0004] Additionally, typical gas-fired fuel appliances designed for
multiple fuel applications include costly redundant gas trains on
board to handle each specific fuel source. Accordingly, there is
usually a requirement for the appliance to be manually converted
with components and adjustment procedures for a specific alternate
fuel before operating the appliance.
[0005] One embodiment provides a water heater including a tank
configured to hold a fluid, a burner configured to manipulate a
temperature of the fluid within the tank, one or more sensors
configured to sense one or more characteristics of the burner, a
fuel injector (or fuel injector array) positioned upstream of the
burner, and a controller. The controller includes an electronic
processor and a memory. The controller is configured to receive one
or more signals from the one or more sensors corresponding to the
one or more characteristics, and control the opening sequence of
the fuel injector (or fuel injector array) based on the one or more
signals.
[0006] Another embodiment provides a method of operating a water
heater. The method includes manipulating, via a burner, a
temperature of a fluid and sensing, via a sensor, the
characteristics of the burner. The method further includes
injecting, via a fuel injector array, a fuel upstream the burner
and supplying, via a blower, an air/fuel mixture to the burner. The
method further includes controlling, via a controller, the fuel
injector based on the characteristic.
[0007] Another embodiment provides a gas-fired appliance including
a burner configured to manipulate a temperature of the fluid within
the tank, a fuel injector (or fuel injector array) configured to
inject fuel upstream of the combustion chamber, a blower configured
to provide an air/fuel mixture to the burner, a sensor configured
to sense a characteristic of the burner, and a controller having an
electronic processor and a memory. The controller is configured to
receive a signal from the sensor corresponding to characteristic of
the burner, and control the fuel injector and the blower based on
the signal.
[0008] Another embodiment provides a gas-fired appliance including
electronic fuel injection controls that are customized specifically
for operation of a gas-fired appliance. The gas-fired appliance
also includes an electronic control unit that receives inputs from
pre-combustion and post-combustion sensing devices, and controls an
amount of gaseous fuel that is injected upstream of a burner to
maintain a relatively constant air/fuel ratio at the burner. In
some embodiments, the gaseous fuel is injected via multiple fuel
injectors (array) located upstream of the burner to mix the gaseous
fuel with the combustion air before the mixture is delivered to the
burner. The electronic control unit may control the opening and
closing time of each fuel injector within the array. In some
embodiments, the opening and closing time is recalculated on a real
time basis to provide a precise and steady stream of gas and air
mixture to the burner.
[0009] In some embodiments, the gas-fired appliance includes
onboard intelligence that, should the effects of altitude start to
reduce the input (for example, as a result of normal density
changes of air and fuel), respond in concert with an air mass flow
sensor to speed up the blower and seek to maintain full input
status rather than operate in a derated state. Traditionally,
gas-fired appliances today are not equipped to make this
adjustment. With this on-board intelligence, the customer does not
need to automatically purchase an oversized appliance to receive
the desired input rate. Therefore, adjusting the speed of the
blower in response to environmental conditions (and to maintain a
constant air/fuel ratio), reduces costs and maintains the desired
output of the gas-fired appliance.
[0010] Another embodiment provides a gas-fired appliance including
a water inlet configured to receive water from an external source,
and a water outlet that delivers the heated water to a storage tank
or to a direct use outlet. The gas-fired appliance also includes a
combustion air supply, a gas supply line that provides gaseous
fuel, and a plurality of fuel injectors (or a fuel injector array)
coupled to the gas supply line such that each injector receives an
independent gaseous fuel supply. The fuel injectors are configured
to inject gaseous fuel in a sequential pattern into a common gas
supply line to be mixed with combustion air and then delivered to
the burner. The gas-fired appliance also includes a combustion air
supply system coupled to the fuel injector (or fuel injector array)
upstream of the burner. Additionally, the gas-fired appliance
includes a blower coupled to the common manifold assembly to
receive the mix of gaseous fuel and air, an air mass flow sensor
positioned in the combustion air stream of the inlet side of the
blower, and a burner coupled to the blower. The burner receives the
mix of gaseous fuel and air from the blower and burns the mix of
gaseous fuel and air to generate products of combustion. The
gas-fired appliance further includes a heat exchanger coupled to
the burner configured to extract heat from the products of
combustion, a flue outlet configured to vent the products of
combustion, an oxygen sensor mounted on the flue outlet, and an
electronic control unit. The electronic control unit is
electrically and/or communicatively coupled to the fuel injectors,
the air mass flow sensor, and the oxygen sensor. The electronic
control unit is configured to receive output signals from the air
mass flow sensor and the oxygen sensor, control the fuel injectors
in sequence based on the output signals from the air mass flow
sensor and the oxygen sensor, and control a speed of the blower
also based on the output signals from the air mass flow sensor and
the oxygen sensor, and in synchronization with the control of the
fuel injectors.
[0011] In some embodiments, an air/fuel ratio sensor replaces the
oxygen sensor in the gas-fired appliance. In such embodiments, the
air/fuel ratio sensor measures the combined total air/fuel ratio
based on the oxygen content in the flue gases. The electronic
control unit receives the air/fuel ratio from the air/fuel ratio
sensor. In contrast, when the gas-fired appliance includes an
oxygen sensor, the electronic control unit computes the air/fuel
ratio based on the output of the air mass flow sensor and the
oxygen sensor.
[0012] Another embodiment provides a gas-fired appliance including
a water inlet configured to receive water from an external source,
a combustion chamber, and a heat exchanger. The combustion chamber
includes a fuel injector (or fuel injector array) and a burner. The
fuel injector (or fuel injector array) is configured to provide
gaseous fuel to the burner. The burner is operable to burn a
mixture of air and gaseous fuel received from the fuel injector to
generate products of combustion. The heat exchanger is configured
to receive the products of combustion and transfer heat from the
products of combustion to the water from the water inlet. The
appliance also includes an electronic processor coupled to the fuel
injector (or fuel injector array) and the burner. The electronic
processor is operable to send an activation signal to the fuel
injector to control a fuel/air ratio of the mixture of air and
gaseous fuel.
[0013] Yet another embodiment provides a method of operating a gas
appliance. The method includes determining, by an electronic
processor, a target fuel/air ratio for operation of the water
heater, and sending, by the electronic processor, an activation
signal to a fuel injector (or fuel injector array) of the water
heater based on the target fuel/air ratio. The method also includes
providing, by the fuel injector (or fuel injector array) opening
sequence, gaseous fuel to a burner of the appliance when the fuel
injector (or fuel injector array) is activated, and generating, by
the burner, products of combustion by burning a mixture of air and
the gaseous fuel. The method further includes receiving, at the
heat exchanger, the products of combustion, and transferring, by
the heat exchanger, heat from the products of combustion to water
received from a water inlet of the appliance.
[0014] Other aspects of the application will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic diagram of an exemplary gas-fired
appliance according to some embodiments of the application.
[0016] FIG. 2 is a schematic diagram of an exemplary fuel injector
system as shown installed within a gas inlet train of the gas-fired
appliance of FIG. 1 according to some embodiments of the
application.
[0017] FIG. 3 is a flowchart illustrating a method of operation of
a fuel injector of FIG. 2 within any multiple set of fuel injectors
used for a particular input according to some embodiments of the
application.
[0018] FIG. 4 is a block diagram of a control circuit for the
gas-fired appliance of FIG. 1 according to some embodiments of the
application.
[0019] FIGS. 5A & 5B are flowcharts illustrating a method of
operation of the gas-fired appliance of FIG. 1 according to some
embodiments of the application.
[0020] FIG. 6 is a flowchart illustrating a method of sending an
activation signal to a fuel injector (or fuel injector array) of
the gas-fired appliance of FIG. 1.
DETAILED DESCRIPTION
[0021] Before any embodiments of the application are explained in
detail, it is to be understood that the application is not limited
in its application to the details of construction and the
arrangement of components set forth in the following description or
illustrated in the aforementioned drawings. The application is
capable of other embodiments and of being practiced or of being
carried out in various ways. Also, it is to be understood that the
phraseology and terminology used herein is for the purpose of
description and should not be regarded as limiting. The use of
"including," "comprising," or "having" and variations thereof
herein is meant to encompass the items listed thereafter and
equivalents thereof as well as additional items. Unless specified
or limited otherwise, the terms "mounted," "connected,"
"supported," and "coupled" and variations thereof are used broadly
and encompass both direct and indirect mountings, connections,
supports, and couplings. Further, "connected" and "coupled" are not
restricted to physical or mechanical connections or couplings.
[0022] FIG. 1 is a schematic diagram of a gas-fired appliance 100
according to some embodiments of the application. In the
illustrated embodiment, appliance 100 is a storage-type gas-fired
water heater 100, however, in other embodiments, the appliance 100
may be any appliance operable to heat a medium, for example but not
limited to a gas-fired furnace, a gas-fired boiler, and/or a
tankless gas-fired water heater. In the illustrated embodiment, the
appliance 100 includes an enclosed water tank 105, a shell 110
surrounding the water tank 105, and foam insulation 115 filling an
annular space between the water tank 105 and the shell 110. The
water tank 105 may be made of ferrous metal and lined internally
with a glass-like porcelain enamel to protect the metal from
corrosion. In other embodiments, the water tank 105 may be made of
other materials, such as plastic.
[0023] A water inlet line 120 and a water outlet line 125 are in
fluid communication with the water tank 105. In the illustrated
embodiment, the water inlet line 120 is in fluid communication with
the water tank 105 at a bottom portion of the water tank 105, while
the water outlet line 125 is in fluid communication with the water
tank 105 at a top portion of the appliance 100. In other
embodiments, the water inlet line 120 may be at a bottom portion of
the appliance 100, while the water outlet line 125 may be at the
top portion of the appliance 100. In yet another embodiment, the
water inlet line 120 may be the top portion of the appliance 100,
while the water outlet line 125 may be at the bottom portion of the
appliance 100. The inlet line 120 includes an inlet opening 130 for
adding cold water to the water tank 105, and the outlet line 125
includes an outlet opening 135 for withdrawing hot water from the
water tank 105 for delivery to a user.
[0024] The appliance 100 also includes a premix assembly 140, an
exhaust structure 142, an air mass flow sensor 143, an oxygen
sensor 145, an inlet temperature sensor 146, an outlet temperature
sensor 147, a heat exchanger temperature sensor 148, an upper
storage tank temperature sensor 149, and a lower storage tank
temperature sensor 150. The appliance 100 analyzes the measurements
from one or more of the sensors 143-150 to monitor and control the
operation of the appliance 100. In the illustrated embodiment, the
premix assembly 140 is supported by and positioned above the water
tank 105. In other embodiments, the premix assembly 140 is
positioned under the water tank 105 and supports the water tank
105. The appliance 100 also includes a heat exchanger 155 in fluid
communication with the premix assembly 140 and the exhaust
structure 142.
[0025] The premix assembly 140 includes an air intake vent pipe
160, a gas inlet manifold assembly 165, a plurality of fuel
injectors 170a-d, a plurality of common gas lines 172a-d, a blower
175, an ignition device 180, a burner 185, and a flame sensor 190.
In some embodiments, the premix assembly 140 is surrounded by a
high temperature insulation to retain the heat from the hot
products of combustion. The air intake vent pipe 160 is in fluid
communication with the blower 175. Operation of the blower 175
draws air for combustion through the air intake vent pipe 160. The
gas inlet manifold assembly 165 is in fluid communication with an
external fuel source such as, for example, a natural gas source.
Each fuel injector 170 is in fluid communication with the gas inlet
manifold assembly 165 to receive the fuel and provide the gaseous
fuel toward the blower 175 upon demand (e.g., in response to an
activation signal from an electronic control unit 405 (FIG. 4)). As
illustrated, in some embodiments, the plurality of fuel injectors
170a-d are located at various positioned spaced from each other.
Although illustrated as a plurality of fuel injectors 170, in other
embodiments, there may be a single fuel injector 170.
[0026] FIG. 2 illustrates a schematic diagram of an exemplary fuel
injector 170. The fuel injector 170 includes an inlet 200 and an
outlet opening 203. The fuel injector 170 also includes an
electrical connector 205, a solenoid 210, a pintle spring 215, a
plunger 220, a valve 225, and a nozzle 230. The solenoid 210 is
electrically coupled to the electrical connector 205. The solenoid
210 is magnetically coupled to the pintle spring 215. The pintle
spring 215 is connected to the plunger 220, which is in turn
connected to the valve 225. The pintle spring 215 retracts and
extends based on the activation of the solenoid 210. The plunger
220 is also slidably movable between a first position in which the
plunger 220 is closer to the outlet opening 203 and a second
position in which the plunger 220 is closer to the inlet 200. Since
the valve 225 is physically connected to the plunger 220, the valve
225 also selectively moves toward the inlet 200 and toward the
outlet opening 203 in response to movement of the plunger 220. The
valve 225 is in an open position when the valve 225 is closer to
the inlet 200, and is in a closed position when the valve 225 is
closer to the outlet opening 203. The inlet 200 is in fluid
communication with the outlet opening 203 of the fuel injector 170
through the nozzle 230 when the valve 225 is open. When the valve
225 is closed, the inlet 200 is not in fluid communication with the
outlet opening 203.
[0027] In contrast to fuel injectors used in other industries such
as the automotive industry, the fuel injectors 170a-d shown in
FIGS. 1-2, comply with different requirements. In some embodiments,
each fuel injector 170 may be located in the gas/air inlet stream
and is designed to withstand temperatures of up to approximately
160.degree. F. Additionally, in some embodiments, each fuel
injector 170 controls the flow of gaseous fuels (for example,
methane, propane, propane air, and the like). Furthermore, in some
embodiments, each fuel injector 170, because of its position in the
gas-fired appliance, withstands a pressure of approximately
0.253-0.361 psi, unless a fuel pump is used, and approximately
0.072-0.361 psi of negative pressure (for example, when positioned
in a premix application). In some embodiments, each fuel injector
170 operates on approximately 24 VAC and requires a relatively low
current (for example, when compared to the current required for the
fuel injector 170 under different applications). In some
embodiments, however, the volumetric flow rate is substantially
higher for the same energy input of liquid to gaseous fuel
sources.
[0028] FIG. 3 is a flowchart illustrating a method 300 of operation
of the fuel injector 170 according to some embodiments. The fuel
injector 170 receives gaseous fuel through the inlet 200 (block
305). The fuel injector 170 then receives an activation signal,
from a control circuit 400 (FIG. 4), through the electrical
connector 205 (block 310). More details regarding the activation
signal from the control circuit 400 are discussed below with
respect to FIG. 6. The solenoid 210 becomes activated due to the
received activation signal (block 315). Since the solenoid 210 is
magnetically coupled to the pintle spring 215, activation of the
solenoid 210 causes retraction of the pintle spring 215 (block
320). As the pintle spring retracts, the plunger 220 moves toward
the inlet 200 thus opening the valve 225 (block 325). In
particular, the plunger 220 overcomes the preload force of the
pintle spring 215, and the plunger 220 moves toward the inlet 200
lifting from an injector seat. When the valve 225 is open, the fuel
injector 170 allow gaseous fuel to pass through the outlet opening
203 (block 330). Specifically, pressure from the gaseous fuel
supply forces gaseous fuel through the outlet opening 203. The fuel
injector 170 remains open while activated. When the fuel injector
170 becomes deactivated, the plunger 220 moves back toward the
outlet opening 203, on the injector seat, thereby inhibiting any
gaseous fuel to pass through the fuel injector 170.
[0029] Referring back to FIG. 1, the blower 175 includes an inlet
side and an outlet side. The blower 175 receives the ambient air
from the air intake vent pipe 160 and the gaseous fuel from the
fuel injector 170 at the inlet side. The blower 175 then provides
an air/fuel mixture to the burner 185 at the outlet side of the
blower 175. In the illustrated embodiment, the blower 175 includes
a variable speed blower, however in other embodiments, the blower
175 may be a single speed blower.
[0030] The ignition device 180 is electrically activated to ignite
the gas/air mixture at the burner surface. The flame sensor 190 is
positioned outside (for example, external to) the surface of the
burner 185, and proximate to (for example, next to) the ignition
device 180. The flame sensor 190 detects a signal indicating
whether a flame is present. In one example, the flame sensor 190
detects a direct current generated by the electronic control unit
405 (FIG. 4) (or another separate device). When a flame is present,
the conductive ionized combustion gases from the flame conduct the
current such that it is detected by the flame sensor 190. When the
flame is not present, the current is unable to find a path to the
flame sensor 190. The electronic control unit 405 (FIG. 4)
determines that a flame is present when the current detected by the
flame sensor 190 is above a threshold level.
[0031] After the ignition device 180 ignites the flame, the
combustion process begins to generate hot products of combustion.
The oxygen sensor 145 (or the air/fuel ratio sensor in some
embodiments) and air mass flow sensor 143 generate and transmit
data to the electronic control unit indicative of an air/fuel ratio
of the combustible air/fuel mixture. An inadequate air/fuel ratio
of the combustible air/fuel mixture may affect, for example, an
efficiency of the water heater and/or the ability of the water
heater to rapidly heat water. In other words, the air/fuel ratio
may affect the heat generated per amount of fuel used to generate
the heat. As described in more detail below, the electronic control
unit 405 (FIG. 4) adjusts the operation of the appliance 100, for
example, of the fuel injectors 170 in particular, to reach various
target air/fuel ratios and maintain the fuel at an optimum
relationship with other performance characteristics. The target
air/fuel ratios may change to, for example, achieve peak thermal
efficiency, meet lowest emissions regulations, provide immunity to
burner noise or resonance, exhibit lower burner surface
temperatures, extend burner life, among other goals.
[0032] The hot products of combustion flow through the heat
exchanger 155 toward the exhaust structure 142. As the products of
combustion flow through the heat exchanger 155, heat is transferred
from the products of combustion to the heat exchanger wall and to
the water surrounding the heat exchanger 155. In the illustrated
embodiment, the hot products of combustion flow downward through a
first portion of the heat exchanger 155, upward through a second
portion of the heat exchanger 155, and downward again through a
third portion of the heat exchanger 155. In other embodiments, the
hot products of combustion may flow downward through the entirety
of the heat exchanger 155. In yet other embodiments (for example,
when the premix assembly 140 is positioned under the water tank
105), the hot products of combustion flow upward through the heat
exchanger 155. In such embodiments, the exhaust structure 142 may
be positioned at an upper portion of the appliance 100. Although
illustrated as having a substantially helical shape, in other
embodiments, the heat exchanger 155 may take other forms or shapes,
for example but not limited to, a substantially straight shape.
[0033] The air mass flow sensor 143 is positioned within the air
intake pipe 160, upstream of the blower 175 and the point where
gaseous fuel from the fuel injectors 170 is introduced into the air
stream. The air mass flow sensor 143 detects a mass flow rate of
air flowing into the blower 175. The air mass flow sensor 143 may
help determine, for example, how much combustible air mixture is
provided to the burner 185.
[0034] The oxygen sensor 145 is coupled to the exhaust structure
142. The oxygen sensor 145 detects excess oxygen levels within the
products of combustion generated by the burner 185. In some
embodiments, the oxygen sensor 145 may be replaced by an air/fuel
ratio sensor 144 that generates an output signal indicative of the
air/fuel ratio. A measure of the excess oxygen level may also be
determined from the output of the air/fuel ratio sensor 144.
[0035] The inlet temperature sensor 146 is positioned at the water
inlet line 120 and measures a temperature of the water entering the
appliance 100. The outlet temperature sensor 147 is positioned at
the water outlet line 125 and measures a temperature of the water
leaving the appliance 100 (for example, to be provided to a user).
The heat exchanger temperature sensor 148 is positioned within the
heat exchanger 155 toward the exit of the heat exchanger 155. The
heat exchanger temperature sensor 148 measures a temperature of the
products of combustion exiting the heat exchanger 155 (also
referred to as the flue gas temperature). The upper tank
temperature sensor 149 is positioned in an upper portion of the
water tank 105 and measures an average water temperature within an
upper volume of the tank 105 (for example, an average water
temperature for the upper one-third of the water tank 105). The
lower tank temperature sensor 150 is positioned in a lower portion
of the water tank 105 and measures an average water temperature
within the lower volume of the water tank 105 (for example, an
average water temperature for the lower one-third of the water tank
105). In other embodiments, the appliance 100 may include more or
less sensors, and the sensors may be positioned elsewhere with
respect to the appliance 100.
[0036] The operation of the plurality of fuel injectors 170a-d, as
well as the other components of the appliance 100 are controlled by
a control circuit 400 (FIG. 4). FIG. 4 illustrates a block diagram
of the control circuit 400. The control circuit 400 includes an
electronic control unit 405 (for example, an electronic processor),
a power regulator 410, a set of input/output devices 415, and a
memory 420. The control circuit 400 is coupled to the premix
assembly 140 to control the plurality of fuel injectors 170a-d, the
blower 175, and the ignition device 180. The control circuit 400 is
also coupled to the sensors 143-150 of the appliance 100 to receive
measurements of different operational parameters of the appliance
100 and adjust operation of the appliance 100 accordingly.
[0037] The control circuit 400 receives power from a power source
430 (for example, an alternating current (AC) power source or a
direct current (DC) power source). In one embodiment, the power
source 430 provides 120 VAC at a frequency of approximately 50 Hz
to approximately 60 Hz. In another embodiment, the power source 430
provides approximately 220 VAC at a frequency of approximately 50
Hz to approximately 60 Hz. In yet another embodiment, the power
source 430 provides a DC voltage (for example, approximately 12
VDC). The power regulator 410 receives the power from the AC power
source 430 and converts the power from the power source 430 to a
nominal voltage (e.g., a nominal DC voltage). The power regulator
410 provides the nominal voltage to the control circuit 400 (e.g.,
the electronic control unit 405, the input/output devices 415, and
the like).
[0038] The input/output devices 415 output information to the user
regarding operation of the appliance 100 and may also receive one
or more inputs from the user. In some embodiments, the input/output
devices 415 may include a user interface for the appliance 100. The
input/output devices 415 may include a combination of digital and
analog input or output devices required to achieve control and
monitoring for the appliance 100. For example, the input/output
devices 415 may include a touch screen, a speaker, buttons, and the
like, to output information and/or receive user inputs regarding
the operation of the appliance 100 (for example, a temperature set
point at which water is to be delivered from the water tank 105).
The electronic control unit 405 controls the input/output devices
415 to output information to the user in the form of, for example,
graphics, alarm sounds, and/or other known outputs. The
input/output devices 415 are operably coupled to the electronic
control unit 405 to control temperature settings of the appliance
100. For example, using the input/output devices 415, a user may
set one or more temperature set points for the appliance 100.
[0039] The input/output devices 415 may also be configured to
display conditions or data associated with the appliance 100 in
real-time or substantially real-time. For example, but not limited
to, the input/output devices 415 may be configured to display
characteristics of the burner 185 (e.g., whether the burner is
activated or malfunctioning), temperature of the water, and/or
other conditions of the appliance 100. In some embodiments, the
input/output devices 415 may also generate alarms regarding the
operation of the appliance 100.
[0040] The input/output devices 415 may be mounted on the shell of
the appliance 100, remotely from the appliance 100, in the same
room (e.g., on a wall), in another room in the building, or even
outside of the building. The input/output devices 415 may provide
an interface between the electronic control unit 405 and a user
interface that includes a 2-wire bus system, a 4-wire bus system,
and/or a wireless signal.
[0041] The memory 420 stores one or more algorithms and/or programs
used to control the plurality of fuel injectors 170a-d, the blower
175, the burner 185, and/or other components of the appliance 100.
In particular, the memory 420 may store firing algorithms for
specifying the time of activation for each of the fuel injectors
170. The memory 420 may also store operational data of the water
heater (e.g., when the burner 185 has been activated, historical
data, usage patterns, and the like) to help control the appliance
100.
[0042] The electronic control unit 405 is coupled to the power
regulator 410, the input/output devices 415, the memory 420, the
fuel injectors 170a-d, the blower 175, the ignition device 180, the
flame sensor 190, the air mass flow sensor 143, the oxygen sensor
145, the inlet temperature sensor 146, the outlet temperature
sensor 147, the heat exchanger temperature sensor 148, the upper
tank temperature sensor 149, and the lower tank temperature sensor
150. As discussed above, in some embodiments, the electronic
control unit 405 may be coupled to the air/fuel ratio sensor 144
instead of the oxygen sensor 145. In other words, the electronic
control unit 405 may determine the air/fuel ratio of the combustion
gases based on the output signals from the air mass flow sensor 143
and the oxygen sensor 145, or from the air/fuel ratio sensor 144
directly.
[0043] The electronic control unit 405 receives the output signals
from each of the sensors 143-150. In particular, the electronic
control unit 405 controls operation of the burner 185 based on the
inlet temperature, a desired or target outlet temperature, an upper
temperature (for example, the water temperature detected by the
upper tank temperature sensor 149), and a lower temperature (for
example, the water temperature detected by the lower tank
temperature sensor 150). For example, the electronic control unit
405 monitors the upper temperature and the lower temperature to
determine when to activate the burner 185. By analyzing the upper
temperature, the electronic control unit 405 determines a
difference between the target outlet temperature and the upper
temperature. When the difference exceeds a difference threshold,
the electronic control unit 405 sends an activation signal to the
burner 185 such that water can be heated. By analyzing the lower
temperature, the electronic control unit 405 ensures that the lower
temperature is at a temperature capable of preventing or inhibiting
condensation to form within the water tank 105. Additionally, the
electronic control unit 405 may use the lower temperature to
estimate an average tank temperature and energy necessary to bring
the water to a user-defined water setpoint (for example, the target
outlet temperature).
[0044] The electronic control unit 405 accesses the memory 420 to
retrieve information relevant to the operation of the appliance
100. For example, the electronic control unit 405 may retrieve
information regarding the usage patterns for the appliance 100, the
previous activations of the burner 185, firing algorithms for the
fuel injectors 170, and the like. The electronic control unit 405
uses the information retrieved from the memory 420 to control the
fuel injector 170. The electronic control unit 405 also outputs
control signals to the blower 175 and the ignition device to light
the burner 185. The fuel injector 170, the blower 175, and the
burner 185 then operate according to the control signals.
[0045] FIGS. 5A & 5B are flowcharts illustrating a method 500
of operating the appliance 100. First, the electronic control unit
405 receives the output signals from the sensors 143-150 (block
505). The electronic control unit 405 then calculates an average
temperature of the stored water based on the temperature sensors of
the gas-fired appliance (block 510). In particular, the electronic
control unit 405 calculated the average temperature for the stored
water based on the inputs received from the upper tank temperature
sensor 149, the lower tank temperature sensor 150, the inlet water
temperature sensor 146, and the outlet water temperature sensor
147. The electronic control unit 405 then determines whether the
average water temperature is below a predetermined setpoint
temperature (block 515). The electronic control unit 405 accesses
the predetermined setpoint temperature from the memory 420. When
the electronic control unit 405 determines that the average water
temperature is not below the predetermined setpoint temperature,
the electronic control unit 405 continues to receive the inputs
from the sensors 143-150 (block 505). On the other hand, when the
electronic control unit 405 determines that the average water
temperature is below the predetermined setpoint temperature, the
electronic control unit 405 generates a demand signal (block 520).
The demand signal indicates that heat is necessary to raise the
average temperature of the water to the predetermined setpoint
temperature.
[0046] The electronic control unit 405 then operates the blower 175
at a pre-purge speed (block 522) to purge the combustion chamber of
any unburnt gases that may be present from a previous heating cycle
or from a failed ignition attempt. The electronic control unit 405
activates the ignition device 180 (block 525) to readily generate a
flame, and sends activation signals to the fuel injectors 170
(block 527). In some embodiments, the electronic control unit 405
activates the ignition device 180 and sends the activation signals
to the fuel injectors 170 simultaneously such that a flame can be
readily generated upon the air/fuel mixture reaching the burner
185.
[0047] Each fuel injector 170 receives the activation signal and
provides gaseous fuel to the blower 175 (block 530). The fuel
injectors 170 provide gaseous fuel to the blower 175 based on the
activation signal from the electronic control unit 405. For
example, in some embodiments, the electronic control unit 405 may
utilize a pulse-width-modulation signal to control the fuel
injectors 170. In such embodiments, each fuel injector 170
activates and deactivates the solenoid 210 based on the frequency
of the pulse-width-modulation signal from the electronic control
unit 405. In other embodiments, however, the electronic control
unit 405 provides a continuous activation signal to each fuel
injector 170 such that each fuel injector 170 opens the valve 225
for a duration of the continuous activation signal. Thereby, the
fuel injectors 170 provide a constant output of gaseous fuel for
the duration of the continuous activation signal. As described
below with respect to FIG. 6, the fuel injectors 170 may be
activated based on a particular firing algorithm.
[0048] After the fuel injectors 170 provide the gaseous fuel, the
electronic control unit 405 determines whether a flame is present
at the burner 185 through the flame sensor 190 (block 532). When
the electronic control unit 405 determines that a flame is not
present, the electronic control unit 405 generates a fault alert to
the user (block 533). In some embodiments, the electronic control
unit 405 deactivates and reactivates the ignition device 180 and
the fuel injectors 170 to attempt to generate a flame again. In
other embodiments, the electronic control unit 405 simply
deactivates the ignition device 180 and the fuel injectors 170.
When the electronic control unit 405 determines that a flame is
present, the electronic control unit 405 controls the blower 175 to
operate at an ignition speed (block 534). The burner 185 then burns
the fuel/air mixture received from the blower 175 and generates
products of combustion (block 535). The heat exchanger 155 receives
the products of combustion (block 540) as the products of
combustion flow toward the exhaust structure 142. The heat
exchanger 155 then transfers heat from the products of combustion
therein to the water surrounding the heat exchanger 155 (block
545), thereby heating the water inside the water tank 105.
[0049] During operation of the water heater 100, as described in
more detail below, the electronic control unit 405 receives the
output signals from the sensors 146-150, and adjusts the operation
of the fuel injectors 170 and/or the blower 175 accordingly. The
electronic control unit 405 continues to compare the temperature of
the water with the setpoint temperature and deactivates the fuel
injectors 170 and the burner when the temperature of the water
reaches the setpoint temperature. The blower 175 may then operate
at a post-surge speed and deactivate.
[0050] In some embodiments, before the activation signal is sent to
each of the fuel injectors 170a-d, and/or the ignition device 180,
the electronic control unit 405 determines whether any faults exist
in the water heating system. When faults are detected by the
electronic control unit 405, a message is output to a user, for
example, via the input/output devices 415 (similar to, for example,
the alert generated when no flame is detected in block 533). In
some embodiments, operation of the water heater 100 ceases while
faults are detected. When the electronic control unit 405 does not
detect any faults, the electronic control unit 405 sends the
activation signal to the fuel injectors 170.
[0051] FIG. 6 is a flowchart illustrating a method 600 of sending
an activation signal to the fuel injectors 170a-d, as discussed
with respect to block 525 of FIGS. 5A & 5B. The method 600 is
triggered by the generation of the demand signal by the electronic
control unit 405. After the electronic control unit 405 generates
the demand signal, the electronic control unit 405 determines a
target air/fuel ratio for operating the appliance 100 (block 605).
As discussed above, the air/fuel ratio determines the efficiency at
which fuel is utilized and an efficiency at which water is heated.
The electronic control unit 405 determines the target air/fuel
ratio for operation based on the output signals from the oxygen
sensor 145, the air mass flow sensor 143, the air/fuel ratio sensor
144, or a combination thereof. The amount of free oxygen present in
the products of combustion is used to determine the amount of
excess air in the fuel/air mixture. The electronic control unit 405
may compare the amount of excess oxygen (as measured, for example,
by the oxygen sensor 145) to an ideal amount of oxygen in the
products of combustion, and may determine the target air/fuel ratio
accordingly. Specifically, when the amount of oxygen determined by
the electronic control unit 405 (e.g., based on the output signals
from one or more of the oxygen sensor 145, the air mass flow sensor
143, or the air/fuel ratio sensor 144) is outside predetermined
limits or thresholds (for example, as specified by the electronic
control unit 405), a different air/fuel ratio is calculated.
[0052] The electronic control unit 405 may access a firing
algorithm for the fuel injectors 170a-d from the memory 420 (block
610). The firing algorithm determines how and when each fuel
injector is to be opened based on feedback inputs from the air mass
flow sensor 143 (or air/fuel ratio sensor 144), the oxygen sensor
145, the temperature sensors 146-150, the flame sensor 190, and
other safety limiting devices sometimes used in the application of
a gas-fired appliance to control the rated input of the burner in
addition to maintaining a constant air/fuel ratio entering the
burner 185. The electronic control unit 405 then calculates a time
of activation for each fuel injector 170 (block 615). The time of
activation is based on, for example, the firing algorithm used by
the electronic control unit 405. The electronic control unit 405
then sends the activation signal to each fuel injector 170 based on
the calculated time of activation (block 620).
[0053] Although the blocks for the flowcharts above have been
described as being performed serially, in some embodiments, the
blocks may be performed in a different order and two or more blocks
may be carried out in parallel to, for example, expedite the
control process.
[0054] In some embodiments, the gas-fired appliance 100 includes
the air mass flow sensor 143 and the oxygen sensor 145, or the
air/fuel ratio sensor 144 without including the plurality of the
fuel injectors 170. In such embodiments, the electronic control
unit 405 controls a valve (or a plurality of valves) of a gas train
system based on the outputs from the air mass flow sensor 143
combined with the outputs from the oxygen sensor 145, or from the
output of the air/fuel ratio sensor 144, instead of controlling the
fuel injectors 170. The electronic control unit 405, however, may
perform similar control algorithms (e.g., logic) as described above
in FIGS. 5-6, but may send activation signal(s) to a valve instead
of a fuel injector 170. The control of the gas-fired appliance 100
based on these sensors 143-145 may increase the operation
efficiency of the gas-fired appliance 100.
[0055] The use of fuel injectors 170, however, significantly
improves (e.g. increase the speed of) the response time to the
control signals from the electronic control unit 405 to maintain a
more constant air/fuel relationship to the burner 185 in contrast
to appliances that do not include fuel injectors. For example, when
external influences (such as, but not limited to, changes in
pressure) may cause changes that affect the air/fuel ratio, in
embodiments illustrated in the application, the electronic control
unit 405 may correct the air/fuel ratio by controlling the fuel
flow though the injectors 170. The fuel injectors 170 are
configured to respond, for example, on the order of milliseconds to
correct the air/fuel ratio through direct control of the fuel flow.
In contrast, pressure driven controls may not be able to respond as
quickly or precisely, if at all, and may instead result in extended
periods of time during which the appliance continues to operate
with an inadequate air/fuel ratio.
[0056] Additionally, using the fuel injectors 170 allows the
operating range of the blower speeds to increase the burner
turndown range (allowing for maximum output to minimum input of the
burner in Btu/Hr (British thermal units per hour)). Increasing the
burner turndown range when operating a heating boiler allows the
boiler to match the load as long as possible without cycling the
burner 185 off. For example, an appliance that does not include
fuel injectors typically has a modulation range limited by the
ability of the blower to provide a minimum stable negative pressure
signal to the regulator of a gas valve. This minimum stable
negative pressure signal typically corresponds to the minimum
blower speed of approximately 1250 RPM (revolutions per minute). On
the other hand, the appliance 100 including the fuel injectors 170
is independent of the negative pressure signal, and therefore the
minimum blower speed (i.e., the minimum input) is specific only to
the requirements for lubrication of the bearing system of the
blower 175 as specified by the manufacturer of the blower 175. The
minimum blower speed in an appliance 100 with fuel injectors 170
may be, for example, 500 RPM, thereby expanding the range of
modulation of the burner 185. The appliance 100 is then able to
operate for longer periods of time without cycling during moderate
and light heating load periods.
[0057] Additionally, the electronic control unit 405 determines the
target air/fuel ratio based on the sensor output signals. By
analyzing the sensor output signals, the electronic control unit
405 can adjust to changing operating conditions of the appliance
100 without requiring additional instructions or manual
adjustments. In particular, the electronic control unit 405 may
directly or indirectly sense different changes in operating
conditions and adjust the target air/fuel ratio as necessary. For
example, operating a gas-fired appliance in higher altitudes
differs from operating the gas-fired appliance in lower altitudes
since the concentration of oxygen in the air decreases as the
altitude increases. The electronic control unit 405, however,
receives an output signal from the air mass flow sensor 143 and the
oxygen sensor 145 (or, alternatively, from the air/fuel ratio
sensor 144) and determines that the air/fuel ratio is too low (for
example, the air/fuel mixture burnt by the burner 185 is too rich).
The electronic control unit 405 can then adjust the activation
signal sent to each fuel injector 170 such that the fuel injectors
170 provide a decreased amount of gaseous fuel to the burner
185.
[0058] Analogously, the electronic control unit 405 may detect
different external conditions that affect the quality of
combustion. For example, the electronic control unit 405 may detect
when a vent length (for example, a length of a vent from an end of
the heat exchanger 155 to the exhaust structure 142) is excessively
long, when sidewall wind conditions increase backpressure to the
blower 175 due to high winds, or when fuel constituency changes. In
some embodiments, the electronic control unit 405 receives inputs
from the oxygen sensor 145, the air mass flow sensor 143 (or,
alternatively, from the air/fuel ratio sensor 144) to detect when
the amount of excess air is not within a predetermined range. When
the amount of excess air is outside the predetermined range, the
electronic control unit 405 adjusts the activation sequencing of
the fuel injectors 170 to reestablish the air/fuel ratio to the
target air/fuel ratio.
[0059] Such precise monitoring of the operating conditions, and
particularly of the air/fuel ratio, enables the appliance 100 to
operate more efficiently. Additionally, including fuel injectors
170 in the appliance 100, due to the small nature of the valve 225,
allows for stricter, more precise control of the amount of gaseous
fuel provided to the burner 185. Therefore, including fuel
injectors in the appliance 100 to provide gaseous fuel to the
blower 175 increases the efficiency of the appliance 100 and
provides greater adaptability to changing operating conditions.
[0060] Thus, the application provides, among other things, a system
and method for operating gas appliance using fuel injection
technology. Various features and advantages of the application are
set forth in the following claims.
* * * * *