SOLID FUEL BURNING STOVE
The solid fuel stove includes a combustion chamber having an air inlet and a gas outlet and two blowers driven simultaneously by a single motor. A first one of the two blowers is upstream of the air inlet and propels a comburent air flow in the combustion chamber. A second one of the two blowers is downstream of the gas outlet and draws an exhaust gas flow from the combustion chamber. Both blowers can advantageously be driven by a single motor.
The present application claims priority of U.S. Provisional Patent application No. 60/778,101, filed Mar. 2, 2006, and entitled “SOLID FUEL BURNING APPLIANCES”, the contents of which are hereby incorporated by reference.
FIELDThe present improvements generally relate to solid fuel burning stoves, and more particularly to improved solid fuel burning stoves having a first blower upstream from the combustion chamber and a second blower downstream from the combustion chamber.
BACKGROUNDSolid fuel stoves are in wide use. Some solid fuel stoves which are referred to as pellet stoves use a biomass fuel in the form of small pellets of about 6 mm in diameter and about 25 mm in length made from waste from wood processing industries. Other types of biomass fuels which are sometimes used include corn, olive pits and wheat, for example.
It is know that when designing solid fuel stoves, achieving a satisfactory efficiency in the use of the fuel and in the transfer of heat from the combustion chamber to the ambient atmosphere are important design considerations. Also, some fuels require a more precisely adjusted flow rate of comburent air to burn efficiently than other fuels which are easier to burn.
Although prior art solid fuel stoves were found satisfactory to a certain degree, there remains room for improvements, including improvements in the way to supply comburent air to the solid fuel in the combustion chamber, and to evacuate the exhaust gasses from the combustion chamber.
SUMMARYIn accordance with one aspect, there is provided a solid fuel stove comprising a combustion air circuit having an intake passageway, a combustion chamber and an exhaust passageway in successive gas flow communication, an intake blower positioned in the intake passageway to blow comburent air to the combustion chamber, an exhaust blower positioned in the exhaust passageway to evacuate exhaust gasses from the combustion chamber, and a blower motor drivingly connected to both the intake blower and the exhaust blower.
In accordance with an other aspect, there is provided a solid fuel stove comprising: a housing having a combustion chamber with an air inlet and a gas outlet; an intake blower propelling a comburent air flow in the combustion chamber through the air inlet; an exhaust blower drawing an exhaust gas flow from the combustion chamber through the gas outlet, the comburent air flow being one of inferior to and equal to the exhaust gas flow and the pressure maintained in the combustion chamber being one of a negative pressure and a void pressure, relative to an ambient pressure; and a single motor operatively connected to both the intake blower and the exhaust blower.
In accordance with an other aspect, there is provided a solid fuel burning stove comprising: a combustion air circuit having an intake passageway, a combustion chamber having an air inlet connected to the intake passageway and a gas outlet, and an exhaust passageway connected to the gas outlet; a burning pot positioned in the combustion air circuit, proximate the air inlet of the combustion chamber; an intake blower associated with the intake passageway; an exhaust blower associated with the exhaust passageway; and at least one intake bypass aperture predesigned through the combustion chamber and through which a limited flow rate of air is aspired when both the exhaust blower and the intake blower are in operation.
Further features and advantages of the present improvements will become apparent from the following detailed description, taken in combination with the appended figures, in which:
The stove 10 includes a hopper 28 adapted to contain a reserve solid fuel pellets (not shown). The hopper 28 is in the rear portion of the housing 12, whereas the combustion chamber 20 is in the front portion thereof. The hopper 28 communicates with the combustion chamber 20 through a solid fuel spout 36. A feeding system, or feeder 30 is included to feed the pellets from the hopper 28 to the burning pot 40, through the fuel spout 36. In this example, the feeder 30 includes an upwardly extending auger 32 which carries pellets from the bottom of the hopper 28 to a solid fuel outlet 34. The solid fuel outlet 34 communicates with the solid fuel spout 36, which extends into the combustion chamber 20 and is aligned with the burning pot 40. The solid fuel spout 36 has a solid fuel outlet 38 oriented in a manner that the pellets traveling therein fall into the burning pot 40 which is positioned inside the combustion chamber 20.
The burning pot 40 is mounted within a container 42 and has air apertures 43 (
The stove 10 generally includes two distinct air circuits: a combustion air circuit through which ambient air is supplied to the burning pot 40 and exhausted from the combustion chamber 20, and a heating air circuit through which ambient air is heated, to augment the amount of heat transfer between the combustion chamber 20 and the ambient atmosphere 21.
The combustion air circuit generally includes an intake passageway 45, the combustion chamber 20, and an exhaust passageway 47, all of which are in successive gas flow communication. The intake passageway 45 (visible in
In the illustrated example, the intake passageway 45 includes an optional intake duct 65, also referred to as combustion blower housing, which is used to connect the intake blower 46 to an external source of air, an intake blower cage 64, also referred to as combustion blower cage, an air inlet channel 48, and the container 42, all in successive gas flow communication. The intake blower cage 64 has an inlet connected to the intake duct 65, which is mounted inside the housing 12. The intake duct 65 has an air inlet 66. In alternate embodiments, the intake duct 65 can be omitted, in which case the combustion blower 46 can aspire the ambient air which has entered the housing 12 by the rear grid 26.
A shutter 85 (depicted in
In operation, comburent air 44 (schematized by the curved line with an arrow) is drawn into the intake passageway 45 of the combustion air circuit through the air inlet 66 by the intake blower 46. The intake blower 46 then propels the comburent air 44 towards the combustion chamber 20 successively through the air inlet channel 48, the container 42, and the air apertures 43, and through the burning pot 40. Following combustion in the burning pot 40, exhaust gasses flow upwardly in the combustion chamber 20.
Referring now to
In operation, exhaust gasses 52 (schematized by the curved line with an arrow) pass through a heat exchanger 54 located in the upper portion of the combustion chamber 20. Heat from the exhaust gasses 52 is transferred to air travelling in the heating air circuit, as will be described further below. Then, the exhaust gasses 52 exit through the combustion chamber gas outlet 56. The exhaust gases 52 are drawn from the combustion chamber 20 through the gas outlet 56, and through the exhaust gas channel 60 by the exhaust blower 58. The exhaust gases 52 flow from the gas outlet 56 towards the exhaust blower 58 through the exhaust gas channel 60, pass through the exhaust blower cage 70 and the exhaust duct 71, and exit from the housing 12 through the exhaust pipe 62 which extends through the rear grid 26. Typically, the exhaust pipe 62 will lead to a chimney (not shown).
The heating air circuit is optional, but can advantageously be used to help increase the amount of heat transfer between the combustion chamber and the ambient atmosphere 21. The heating air circuit includes a heat exchanger 54. In this case, the heat exchanger 54 is a cross-flow heat exchanger which has a plurality of heat-exchanging pipes 74 traversing the upper portion of the combustion chamber 20. The heating air circuit also has a heating air passageway (not shown) for channelling air drawn into the housing 12 through the grid 26 to a manifold 73 (
Referring both to
In this case, both the intake blower 46 and the exhaust blower 58 are located below the hopper 28, on opposite sides of the housing 12, and they are both driven by a common motor 76. Therefore, when energizing the motor 76, both blowers 46, 58 are simultaneously driven, and the flow rate of comburent air 44 through the burning pot 40 can be adjusted by varying the rotating speed of the motor 76. In this example, the operation of the solid fuel stove can be controlled with a controller interface 77 located on a side panel of the solid fuel stove 10, visible in
There are several advantages to using both an intake blower and an exhaust blower rather than only one, or only the other. For instance, using an intake blower can allow to maintain a supply of comburent air to maintain combustion when the door panel is open by a user. Also, combustion air circuits, and combustion chambers in particular, are typically air-tight and sealed when manufactured. However, with time and aging, some seals are known to fail, and fissures or gaps can appear. Using only an intake blower can lead to the creation of a positive pressure buildup (relative to ambient pressure) in the combustion chamber, which can result in leakage of exhaust gasses through these fissures or gaps. Alternately, using only an exhaust blower can lead to diminishing efficiency of the air flow into the burning pot due to air leakage into the combustion chamber through these fissures of gaps. When an exhaust blower having a greater blowing power than the intake blower is also used, a negative pressure can be maintained in the combustion chamber. This can advantageously result in ambient air entering the combustion chamber through the fissures or gaps, rather than exhaust gasses escaping the combustion chamber through these fissures of gaps.
A practical limitation which has thus far limited the public availability of stoves having both an intake blower and an exhaust blower is the fact that two blowers typically require two motors to operate. This increased manufacturing costs related to such stoves and posed a monetary barrier to the purchase of such stoves by some members of the public. Also, two blower motors typically result in a greater electrical energy consumption during operation than a single blower motor. Further, the power ratio between the exhaust blower and the intake blower, which contributes in maintaining a negative pressure in the combustion chamber, was dependent of the relative rotation speed of the two blower motors, and some factors such as uneven aging between the two blower motors could lead to a disbalance occurring between the relative rotation speed of the exhaust blower and the intake blower. This has been known to diminish the efficiency of the negative pressure maintained in the combustion chamber, and even in some cases, to cause a positive pressure to appear.
It has been found that using a single blower motor to drive both the intake blower and the exhaust blower allows to overcome at least some of the aforementioned drawbacks. For example, using a single blower motor can reduce manufacturing costs relatively to the required purchase of two blower motors. It can allow a lower energy consumption during operation of the stove because the energy required to drive one motor is typically lower than the energy required to drive two motors. Also, using a single blower motor drivingly connected to both the intake blower and the exhaust blower is one way to allow control of the relative rotation speeds of the intake blower and the exhaust blower. There is a reduced likelihood of a disbalance occurring between the two blowers since both blowers are similarly affected by a change of rotation speed of the blower motor. This allows adjusting only one motor to control combustion intensity, rather than having to maintain a specific ratio between the rotational speeds of two different blower motors. If it is desired to modify the relative flow rate generated by the intake blower and the exhaust blower, this can be achieved for example by the use of an appropriately positioned shutter in the intake passageway, to offer an adjustable restriction to gas flow in the passageway. Optionally, a shutter can be used in the exhaust passageway in certain applications.
In some cases, having a stove with both an intake blower and an exhaust blower can allow the flow rate of air supplied to the combustion chamber to be more precisely controlled, thus yielding a more complete combustion, a combustion generating an enhanced visual effect, or a combustion which is better suited to the particular type of solid fuel used. Thus, it can enable to burn a wider variety of solid fuels, such as biomass fuel like corn, olive pits, wheat, etc. which require a more precisely adjusted flow rate of comburent air.
The intensity of the negative pressure maintained in the combustion chamber, for a given blowing power difference between the exhaust blower and the combustion blower, can advantageously be controlled, or limited, by providing at least one predesigned intake bypass aperture 91 through the combustion chamber 20, allowing gas flow communication between the combustion chamber 20 and the ambient atmosphere 21, at some point between the combustion chamber air inlet 43a and the exhaust blower 58, typically through the combustion chamber 20.
The bypass aperture(s) are provided to allow some ambient air to enter the combustion chamber directly, thus bypassing the intake passageway 45 of the combustion air circuit. The bypass aperture(s) are predesigned, and can thus have a predetermined area to offer a predetermined amount of restriction to bypass flow therethrough. The greater the negative pressure is present in the combustion chamber 20, the greater the bypass flow rate through the bypass aperture(s) will be. In turn, the bypass flow rate will serve to limit the negative pressure differential (negative pressure) between the combustion chamber and the ambient atmosphere 21.
The predesigned intake bypass aperture(s) can be located at any point through the combustion chamber. However, it is advantageous to provide them below the window 22 in the door panel 18. When bypass apertures 91 are positioned below the window, the bypass flow rate of air 93 tends to curtain behind the window 22 and limit the exposure of the window 22 to exhaust gasses, which can prevent or diminish the appearance of soot deposits in the window 22.
In addition of providing the advantage of control of the flow rate of ambient air bypassing the intake passageway 45, the use of one or more predesigned bypass apertures can benefit in alleviating the drawbacks related to the appearance of gaps or fissures in the combustion chamber seals due to aging.
Hence, in the illustrated example, the exhaust blower 58 is arranged to generate a higher flow rate than the intake blower 46, because it additionally evacuates the bypass flow rate 93 of ambient air entering the combustion chamber 20 through the bypass intake apertures 91. The negative pressure (relative to ambient pressure) maintained in the combustion chamber 20 during operation is a function of the blowing power difference between the exhaust and intake blowers, and of the flow restriction caused by the configuration and size of the intake bypass apertures 91.
When two separate motors are used, the exhaust blower can be driven at an increased speed relative to the intake blower. This is also possible when using a single motor, by use of a transmission between the motor and at least one of the blowers. In either case, many other ways can also be used to provide a greater flow rate through the exhaust blower than through the intake blower 46. For example, it is possible to use a larger or more efficient fan or impeller in the exhaust blower 58 than in the intake blower 46. Alternately, it is possible to restrict the air flow through the intake blower 46, such as by designing a narrow throat section in the intake passageway, or with the use of a shutter to render the area of a portion of the intake passageway adjustable. These are only examples, and many other ways can also be used to achieve this. In the illustrated example, the air flow through the intake blower 46 is restricted by the intake apertures 43a.
In
Turning now to
The intake blower cage 164 is mounted to one side of the motor 176 and the exhaust blower cage 170 is mounted to the opposite side. The motor 176 includes a driving shaft 178 with a first end 180 and a second end (not shown) extending from opposite sides of the motor 176. The first end 180 is operatively connected to the impeller 181 of the exhaust blower 158 and the second opposite end is operatively connected to the impeller 183 of the intake blower 146. When the motor 176 is energized, the driving shaft 178 rotates and drives both blowers 146, 158, including their impellers 181, 183, to rotate about their rotation axis, creating an airflow in their respective cages 164, 170. During operation, the impellers 181, 183 create a flow rate through the exhaust cage outlets 173 and combustion cage outlet 169, respectively. A person skilled in the art will appreciate that the motor 176 can be either a constant speed motor or a variable speed motor.
Referring now also to
As discussed above, the flow rate generated by the exhaust blower 158 will tend to be greater than the flow rate generated by the intake blower 146, because the impeller 181 and cage 170 of the exhaust blower 158 are larger in size than the impeller 183 and cage 164 of the intake blower 146 in this example. For comparison purposes, in the example depicted in
Turning to
The use of many alternate blower assemblies are possible and the two examples given above are intended to be illustrative only. It will be understood that various types and sizes of impellers can be used in either blower.
Even if in the embodiment described above, the stove 10 is particularly suited to the combustion of solid fuel in pellet form, it is to be understood that the present improvements can be applied to stoves that are adapted to burn other types of solid fuel materials. In some cases, the solid fuel materials are fed to the combustion chamber manually, rather than with a feeding system or feeder.
As can be appreciated, the examples given are for illustrative purposes only. The configuration of the intake blower, exhaust blower and motor assembly can vary from the ones illustrated. The shutters, if any, for controlling the air flow in the combustion air network, can be mounted in any one or more of upstream and downstream of the intake blower, and upstream and downstream of the exhaust blower.
Further, the location of the different components, such as the grid, the hopper, the blowers, etc., in the stove 10 can greatly depart from that illustrated, and some components may also be omitted. Other solid fuel feeding mechanism can be used instead of the auger and the hopper. It will also be appreciated that the solid fuel feeding mechanism is selected as a function of the solid fuel used.
Therefore, the embodiments of the invention described above are intended to be exemplary only. The scope of the invention(s) is therefore intended to be determined solely by appreciation of the appended claims.
Claims
1. A solid fuel stove comprising a combustion air circuit having an intake passageway, a combustion chamber and an exhaust passageway in successive gas flow communication, an intake blower positioned in the intake passageway to blow comburent air to the combustion chamber, an exhaust blower positioned in the exhaust passageway to evacuate exhaust gasses from the combustion chamber, and a blower motor drivingly connected to both the intake blower and the exhaust blower.
2. The solid fuel stove of claim 1 further comprising at least one intake bypass aperture predesigned through the combustion chamber, and wherein the exhaust blower generates a greater flow rate than the intake blower when the blowers are in operation, thus maintaining a negative pressure in the combustion chamber and drawing ambient air into the combustion chamber through the at least one bypass aperture.
3. The solid fuel stove of claim 2 wherein the blower motor is directly connected to both the intake blower and the exhaust blower, to drive both blowers at the same rotation speed, and the exhaust blower has an impeller which is configured and disposed to generate a greater flow rate than the intake blower when both blowers are driven at the same rotation speed.
4. The solid fuel stove of claim 2 wherein the intake passageway defines a restricted area which limits the flow rate generated by the intake blower.
5. The solid fuel stove of claim 2 wherein the intake passageway includes a shutter allowing adjustment of the flow rate through the intake blower.
6. The solid fuel stove of claim 2 further comprising a door panel allowing access to the combustion chamber, the door panel having a window, and wherein a plurality of intake bypass apertures are located immediately below the window.
7. The solid fuel stove of claim 1 further comprising a burning pot positioned in the combustion air circuit, at an entrance to the combustion chamber, a solid fuel pellet reservoir having a pellet spout aligned with the burning pot, and a pellet feeder configured and adapted to carry pellets from the pellet reservoir to the pellet spout.
8. The solid fuel stove of claim 1 further comprising a heating air circuit having an inlet open to the ambient air, a heat exchanger traversing the combustion chamber, and an outlet, and a heating air blower for circulating ambient through the heating air circuit.
9. The solid fuel stove of claim 1 further comprising a blower motor rotation speed controller connected to the blower motor and allowing manual adjustment of the rotation speed of the blower motor by a user.
10. A solid fuel stove comprising:
- a housing having a combustion chamber with an air inlet and a gas outlet;
- an intake blower propelling a comburent air flow in the combustion chamber through the air inlet;
- an exhaust blower drawing an exhaust gas flow from the combustion chamber through the gas outlet, the comburent air flow being one of inferior to and equal to the exhaust gas flow and the pressure maintained in the combustion chamber being one of a negative pressure and a void pressure, relative to an ambient pressure; and
- a single motor operatively connected to both the intake blower and the exhaust blower.
11. A solid fuel stove as claimed in claim 10, wherein the motor comprises a driving shaft having two opposite ends, each opposite end simultaneously driving a respective one of the intake blower and the exhaust blower.
12. A solid fuel stove as claimed in claim 10, comprising an intake blower housing defining an intake blower chamber enclosing the intake blower and being in fluid communication with the air inlet of the combustion chamber, the intake blower housing having an air inlet in fluid communication with the combustion air chamber and restricting the air supply therein.
13. A solid fuel stove as claimed in claim 10, comprising at least one shutter for controlling at least one of the comburent air flow and the exhaust gas flow.
14. A solid fuel stove as claimed in claim 10, comprising a non hermetic door panel mounted to the housing and allowing access to the combustion chamber.
15. A solid fuel burning stove comprising:
- a combustion air circuit having an intake passageway, a combustion chamber having an air inlet connected to the intake passageway and a gas outlet, and an exhaust passageway connected to the gas outlet;
- a burning pot positioned in the combustion air circuit, proximate the air inlet of the combustion chamber;
- an intake blower associated with the intake passageway;
- an exhaust blower associated with the exhaust passageway;
- a blower motor drivingly connected to both the intake blower and the exhaust blower; and
- at least one intake bypass aperture predesigned through the combustion chamber and through which a limited flow rate of air is aspired when both the exhaust blower and the intake blower are in operation.
16. The solid fuel burning stove of claim 15 further comprising a door panel having a window, the door panel being openable to provide access to the combustion chamber, wherein the at least one predesigned intake bypass aperture is provided in the door panel, below the window.
17. The solid fuel burning stove of claim 15 wherein the motor is directly connected to both the intake blower and the exhaust blower, to drive both blowers at the same rotation speed, and the exhaust blower has an impeller which is configured and disposed to generate a greater flow rate than an impeller of the intake blower when both impellers are driven at the same angular speed.
18. The solid fuel burning stove of claim 15 wherein the intake passageway defines a restricted area which limits the flow rate generated by the intake blower.
19. The solid fuel burning stove of claim 15 wherein the intake passageway includes a shutter allowing adjustment of the flow rate through the intake blower.
20. The solid fuel burning stove of claim 15 further comprising a heating air circuit having an inlet, a heat exchanger extending through the combustion chamber, and an outlet.
Type: Application
Filed: Mar 1, 2007
Publication Date: Sep 6, 2007
Inventor: Pierre Pleau (Quebec)
Application Number: 11/680,728