GB2526600A

GB2526600A - Fuel burner ignition system

Info

Publication number: GB2526600A
Application number: GB1409540.0A
Authority: GB
Inventors: Matthew Statham
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-05-29
Filing date: 2014-05-29
Publication date: 2015-12-02
Also published as: GB201409540D0; WO2015181543A1

Abstract

An ignition system (18, fig 1) of a domestic fuel (wood) burning stove 10 comprises a combustion zone 34, an access area 32 on at least one side of the combustion zone for accessing materials within the combustion zone, a fan 70 outside the combustion zone, a flow guide 50 (conduit) conveying air from the fan to the combustion zone and an in-line heater 82 within the flow guide. The flow guide directs the flow of air heated by the inline heater into the combustion zone in a direction FD away from, or parallel to, the access area. The flow guide may be within a side wall 24 of the stove, in particular within thermal insulating lining 38 with the heater within the insulating lining. The fan may be a centrifugal fan comprising an impeller 71 driven by a motor 78 and is located on a rear surface 26 of the stove. The ignition system may be attached to the back of the stove and mounted on glass fibre thermal insulation layer 58 and separated from a metal back plate 60 by feet 62 providing an air gap therebetween. The back plate may have cooling fins thereon.

Description

Fuel burner ignition system The present invention is concerned with a fuel burning stove ignition system. More specifically, the present invention is concerned with a fuel burner ignition system for a domestic fireplace or fuel burning stove, in particular for a wood burning stove.

By "stove" we mean a device which is positioned within a hying space such as a living room or kitchen, and designed to directly heat that space through heat transfer to its surroundings. Domestic wood burning stoves are popular household installations. They are generally supplied as standalone units, beneficially require little effort to install (the only significant change to the property being the provision of a passage for a flue pipe) and provide heat from a burning fuel in order to heat a room.

They are also rdatively inexpensive and easy to repair and/or replace. Domestic stoves of this type may also be suitable for burning other fuels, such as coal.

Modern fuel burning stoves generally comprise a metal body on legs. or other support structure, thc body dcfining a combustion chambcr or firebox. Thc combustion chamber is typically at least partially lined with a material having a high tolerance to heat, and a low thermal conductivity, such as vermiculite. Refractory ceramic materials are commoffly used and all such materials are referred to in the trade as "firebrick". The firebrick will line the lower region of the combustion chamber hut may not line the upper region, so as to encourage conduction of heat into the space in which the stove is located.

In most domestic fuel burning stoves, an openable door is provided with a glass window in order to provide access and visibility to the fire therein. Adjustable vents are provided for die user to control lim flow of air liirough the combustion chamber (and thereby the burn rate), and an ash collection tray is provided below a grate in the combustion chamber floor. A vcnt may bc provided just above the glass window to encourage a stream of air to flow over the inside of the window, and thereby avoid the build-up of soot.

Extending upwardly from the top of combustion chamber (from a sidewall or the top wall itself) and in fluid communication therewith, there is provided a flue exiting the property through the rooi or a wall. The flue acts to transport the hot exhaust gases from the combustion chamber, the resulting low pressure drawing fresh air in through S a series of adjustable vents in the body which keeps the fire oxygenated.

In operation. light, fast-burning combustible materials are first placed within the combustion chamber and lit. These materials comprise a combination of firelighters, paper and/or kindling. The initial stage of lighting usually requires the addition of a lot of fast-burning material in order to heat the flue gases and establish a flow of air though the vents, through the combustion chamber and to the flue. Once the fire from the kindling material is established, and the flue temperaturc has risen. largcr lumps of slow-burning combustible fuel such as firewood can be introduced.

The use of a significant amount of fast-burning material to heat die combustion chamber and flue produces a lot of smoke, which is unpleasant for neighbours and passers-by. Chemical firelighters are unpleasant to use, and can he dangerous ii not handled correctly. In addition, lighting the lire requires the user's attention for a significant period of time before it is established.

It is an aim of the present invention to overcome or at least mitigate the above problems.

According to a first aspect of thc present invention thcre is providcd a domestic fuel burner comprising: a combustion zone; an access area on at least one side of the conibustion zone for accessing materials within the combustion zone; air flow creation means outside the combustion zone; a flow guide for conveying air from the air flow creation means to the combustion zone; an in-line heater disposed within the flow guide; wherein the flow guide is configured to direct the flow of air heated by the in-line heater into the combustion zone in a direction away from, or parallel to, the access area.

S Advantageously this provides a safe means of directly lighting logs and other materials without the use of kindling I paper etc. It also ensures that the flow of hot air cannot cause injury when or if the user approaches the access area, for example by opening the stove door.

Preferably the flow guide defines a flow path and an outlet, which flow path is configured to direct the flow of air heated by the in-line heater into the combustion zone in a direction away from, or parallel to, the access area.

The use of a specific flow path allows the flow of air to be placed in any desired I 5 location in the burner.

Preferably the flow guide comprises an endosed flow conduit defined in a structure of the domestic fuel burner, preferably a side wall as this aflows for the fan to he p'aced at the rear of the burner. Preferably the structnre comprises a thermally insulative lining of the fuel burner. This insulates the flow path, retaining the heat for combustion.

Preferably the in-line heater is at least partially disposed within the layer of thermally insulative lining. This ensures that the very hot element is not accessible by the user, not does it cause "hot spots" on the outside of the unit.

Preferably the flow guide defines a flow path which changes the direction of the flow from the fan to the combustion zone. This means that air can be routed from the rear of the unit to the front, and redirected to the rear of the combustion chamber. In other words, the Ian can be located on a rearwardly facing surface of the burner, opposite the access area, the flow path guiding the flow of air initially towards the access area before changing the direction of the flow prior to the flow entering the combustion zone.

According to a second aspect of the invention there is provided a fuel burner compnsing: a combustion zone; S a layer of thermally insulative material bordering the combustion zone: a fan outside the combustion zone; an flow guide for conveying air from the fan to the combustion zone, the flow guide at least partially passing through the layer of thermally insulative material; an in-line heater disposed within the flow guide; wherein the in-line heater is at least partially disposed within the layer of thermally insulative material.

Advantageously, this both retains the heat of the element of the in-line heater, reducing losses and allowing as much heat as possible to be retained in the air flow.

and also avoids "hot spots" on the outside of the unit, which may he dangerous.

Preferably (he in-Hue heater is lufly contained witFin the thermally insulative material.

Preferably the how guide comprises a conduit defined witFin the thermally insulative material, having an inlet end and an outlet end, in which the in-line heater is spaced from the inlet end and the outlet end.

Preferably the flow guide has a cross section which reduces downstream of the in-line heater. This accelerates the flow ready for impingement on the fueL According to a third aspect of the invention there is provided a fuel burner comprising: a combustion zone; a rotodynarnic pump outside the combustion zone; a flow guide for conveying air from the fan to the combustion tone; an in-line heater disposed within the flow guide.

The use of a rotodynarnic pump, preferably a fan with a rotating impeller. has several advantages over other types of pump-e.g. fixed displacement diaphragm pumps. Fans are quiet, which is advantageous in a domestic environment. Fans are also open-inasmuch as flow can pass through a fan when the impeller is stationary, for example in the event of a pressure difference across the Ian. This is useful for a burner, because the fan can be used as an extra vent, the opening of which can be controlled by a shutter or valve. Fans also offer a high flow rate compared to e.g. fixed displacement pumps such as diaphragm pumps. Preferably the fan flow rate is set at a value above 4 x lO m3Is. The applicant has demonstrated that such a flow rate provides enough thermal energy to initiate combustion, whist directly warming the flue to encourage a convective air flow to be established in a short about of time (typically 3-5 minutes). Rotordynamic pumps such as fans are well suited to such a flow rate in the available space (particularly compared to fixed displacement pumps).

This value is at least five times the flow rate available with an equivalent size diaphragm pump.

Preferably the rotodynamic pump is a centrifugal fan.

Preferably the fan has an ifflet and an inlet closure mechanism configured to at least partially close the inlet. This allows the Ian to he used as a vent. Preferably the inlet closure mechanism is configured to fully close the inlet-this is desirable when the fire is established so the user can use the standard vents on the front face of the burner.

Preferably the fan is mounted to an exterior surface of the fuel burner such that an axis of rotation of the impeller intersects the combustion zone. This means the fan sits against a wall of the burner, and can be made quite large without significantly increasing the size of the burner.

Preferably the flow guide defines a reduction in cross sectional area configured to accelerate the flow of air. This makes the heat transfer to the fuel more effective.

A fuel burner ignition system and fuel burning comprising such a system will now he described with reference to the accompanying drawings in which:-FIGURE 1 is a front perspective view of a fuel burning stove comprising an ignition system in accordance with the present. invention; FIGURES 2 and 3 are alternate rear perspective view of the fuel burning stove of S Figure 1: FIGURE 4 is a front view of the fuel burning stove of Figure 1; FIGURE 4A is a section view of the wood burning stove of Figure 1 through section A-A as shown in Figure 4; FIGURE 5 is a rear view of the wood burning stove of Figure 1 with a rear cover removed; FIGURE 5A is a section view of the wood burning stove of Figure 1 through section A-A as shown in Figure 5; and FIGURE 6 is a perspective view of a part of the wood burning stove of Figure 1.

Referring to the figures, a fuel burning stove 10 comprises a body 12 supported by legs 14, 16. An ignition system 18 is provided which is partly visible from the views of Figure 2 and Figure 3, although it extends into the body 12 as will be described below.

The body 12 comprises a box-like metallic outer frame 13 having a horizontal top panel 20, left and right vertical side panels 22, 24, a vertical back panel 26, a horizontal bottom panel 28 and a vertical front panel 30. The front panel 30 defines an aperture 32 configured to receive an openable closure (not shown). The aperture 32 defines a notional aperture plane AP (Fig 4A), which is perpendicular to the direction D in which materials are placed into the stove 10 through the aperture 32.

The frame 13 is constructed from a sheet metal material.

The back wall 26 defines two apertures-a flue aperture 46 visible in Figures 2, 3 and 5 for attachment of a flue (not shown), and an ignition aperture 48 visible in Figure 4A for use by the ignition system 18. Various variably openable vents are provided in the body. which can be manually controlled by the user, but are not shown.

The inner surfaces of the frame panels 20, 22, 24, 26, 28, 30 are each lined with a layer of firebrick. Referring to Figure 4a. a left side panel firebriek layer 36, right side panel firebrick layer 38, and back panel firebrick layer 40 can be seen in cross-section.

It will be noted that part of the entire inner surface of the frame 13 is lined with a firebrick layer. The lower part of the frame 13 is lined with firebrick such that the upper part can conduct heat away more easily.

As shown in Figure 4A. the left side panel firebrick layer 36 and back panel firebrick layer 40 are of constant thickness. The right side panel firebrick layer 38 is of a different construction, having a front portion 42 which tapers outwardly to a thicker rear portion 44 which meets the back panel 26 of the body 12. The right side panel lirebrick layer also defines a flow guide in the form of a conduit 50, which at an inlet end is in communication with the ignition aperture 48, and at an outlet end is in communication with the combustion chamber 34. The conduit 50 defines a flow path FP shown in dashed line.

Moving from the inlet end, the flow conduit defines a generally cylindrical portion 51 which merges into a nozzle 52 extending from, and in fluid communication with, the flow conduit 50. Through the portion 51 and nozzle 52, the flow path FP is in a direction towards the front of the burner 10 (and towards the aperture plane AP). A shoulder 54 is defined between the cylindrical portion 51 and the nozzle 52. In fluid communication with the smaller end of the nozzle 52, there is provided a curved flow portion 56 which redirects the flow path FP and turns it through about 135 degrees towards the hack of the burner 10-i.e. to angle of about 15 degrees away from the aperture plane AP, having a component in the same direction as D. This is the exit flow direction FD. The curved flow portion 56 uses a curved path configured to change the direction of the flow.

The ignition system 18 compnses a thermal insulation layer 58, which is attached to the exterior of the back panel 26. The thermal insulation layer is constructed from a 10mm thick glass libre mat with a metal haekplace. An ignition system hack-plate 60 is mounted to the exterior of the back panel by a series of feet 62 which extend through the thermal insulation layer 58 (see Figure SA). As such, the back-plate 60 is offset from the thermal insulation layer 58 to provide an air gap therebetween. The back-plate is constructed from metal and has a series of cooling fins thereon to distribute heat from the components of the ignition system 18 mounted thereon. The back-plate 60 has a manifold aperture 61 defined therein.

A flow gasket 64 spans the air gap between the thermal insulation layer 58 and the back-plate 60. The gasket 64 defines a central orifice 66 therein in fluid communication with the ignition aperture 48 and the manifold aperture 61.

The ignition system 18 (with reference to Figure 6) comprises a power and control system 68 mounted to the back-plate 60 which comprises the necessary power electronics and control electronics in order to control the rest ol the ignition system 1 8 as will he described below. The system 68 is configured to he connection to domestic AC power (ranging from AC 110 -250V, 50 -60Hz). Next to the control and electronics system 68 and also mounted to the back-plate 60 there is provided a centrifugal fan 70. The fan 70 is driven by a fan motor 78 mounted concentrically therewith. The fan 70 has an inlet region 72 facing rearwardly of the burner 10. The fan 70 has a movcahle cover plate 74 which can he rotated about a cover plate axis X to open or close the inlet 72 of the fan 70. The cover plate 74 comprises a cover plate lever 75 extending radially therefrom arranged to be driven about the axis X by a link 77 which in turn is driven by a crank 79 rotated by a motor 76. The cover plate 74 can therefore be rotated between open and closed positions by the motor 76.

The motor 76 is conuigured to he continuously variable between the open and dosed positions of the cover plate 74 to enable use as a variable cross section inlet.

The centrifugal fan 70 having an impeller 71 is configured to induce an airflow into an outlet manifold 80 as shown in Figure 4A which is in fluid communication with the manifold aperture 61 to pass fluid through the gasket 64, through the ignition aperture 48 and into the flow conduit 50.

The ignition system 18 comprises an inline air heater assembly 82. The inline air S heater assembly 82 is an off the shelf component containing an electric hcating element configured to heat the air passing therethrough. Referring to Figure 4a, the inline heater assembly 82 is positioned within the flow conduit 50 in abutment with the shoulder 54. The air heater assembly 82 is surrounded (apart from its inlet and outlet) by the right side panel firebrick layer 38. The air heater assembly 82 is also completely contained within, and spaced apart from, the panels of the frame 13.

The power and control system 68 is configured to selectively control the motor 76 controlling the cover plate 74, the motor 78 dnving the fan 70 and the inline air heater assembly 82. The power and control system 68 comprises a button 84 for starting a stored, predetermined, timed sequence of operation of these components as will he described below. The opening of the fan inlet 72 can be independently controlled to allow for variable venting of the lire in the combustion chamber when established.

Primary slow-burning fuel (such as large lumps of firewood or coal) is placed within the combustion chamber 34 when the system is cold, preferably in the path of the ignition system flow direction FD from the outlet of the curved flow portion 56 of the conduit 50. The user closes the door (not shown) in the aperture 32 and starts the ignition process by depressing the start button 84. In response, the power and control system 68 opens the cover plate 74 by driving the motor 76. At the same time the power and control system 68 starts the centrifugal fan 70 by driving the fan motor 78.

The power and control system 68 also activates the heater assembly 82 to heat the air flowing therethrough.

As such. hot air is impinged upon the combustion materials within the combustion chamber 34 which (depending upon the condition of the materiais) will light. This typically takes a few minutes with dry firewood. After a predetermined amount of time has elapsed, the power and control system 68 deactivates the heater 82 and fan 70. At this stage it is desirable to keep the inlet 72 open in order to supply an increased flow of air to the combustion materials such that a fire can be established.

After a second predetermined amount. of time, the motor 76 is driven o close the inlet 72 such that the control of the flow of air can he undertaken by the user hy opening and closing any other vents present on the body 12 (not shown). It will be noted that S it can be disadvantageous to allow too much air to enter the combustion chamber as the fire may burn too hot and inefficiently.

As shown in Figure 4a, the direction PD is towards the rear of the enclosure 34. This is important as it is possible that the user may open the door in the aperture 32 to stoke or otherwise introduce more material into the enclosure 34 whilst the ignition system is engaged. Should the direction ED he towards the aperture 32, then this would result a stream of extremely hot air being projected towards the user. For obvious reasons, this is a safety concern and would be undesirable.

Variations laB within the scope of the present invention.

The direction FD can he varied. Referring to Figure 4A, flow directions ED' and ED" are shown. ED' is parallel to the aperture plane AP (hut not towards it) and would he a useful choice if the flow outlet was near the back of the chamber 34. PD" is at 90 degrees away from the aperture plane AP (the same direction as D) and is preferred, but may be difficult to achieve because the conduit will usually be in the sidewall. In reality, a flow direction PD will be chosen between 0 (PD') and 90 (PD") degrees away from the aperture to direct the flow towards the likely position of the combustion materials. Evidently the flow guide can also be placed in the opposite sidewall of the chamber. It is important that FD is not chosen so as to project the flow of hot air towards the aperture 32 (i.e. in a direction having any component towards AP and in the opposite direction to D).

The starting of the ignition system 18 may he by any appropriate means. for example by remote control rather than the switch 82. The opening 72 may also he remote controlled when the fire is established to allow for user-controlled venting.

The sequence of operation may be modified such that after a first period of time, only the heater is deactivated, and the fan continues to run (either at the same, or at a lower speed) to act as a bellows' to supp'y the lire with oxygen during establishment.

The stove 10 may be any known shape and known stoves may have curved bodies which are cylindrical or ellipsical in cross-section. Under such circumstances, the terms "front", "hack", "left" and right" still apply to sections of the stove body and frame, as the skilled addressee would understand.

The present invention is also suitable for open fires, having one or more closed sides and one or more open sides. In this case, the flow direction FD is always towards a closed side, or specifically away from all open sides.

The present invention is applicable for all types of fuel burning stove and is not limited to wood burners, for examp'e other domestic fuels are available.

The flue aperture 46 may he positioned on one of the side wall panels, or the top panel of the body 12.

Claims

Claims 1. A domestic fuel burning stove comprising: a combustion zone: an acccss area on at least onc side of the combustion zone for accessing materials within the combustion tone; a Ian outside the combustion zone; a flow guide for conveying air from thc fan to the combustion zone; an in-line heater disposed within the flow guide; wherein the flow guide is configured to direct the flow of air heated by the in-line heater into the combustion zone in a direction away from, or parallel to, the access area.
2. A domestic fuel burning stove according to claim 1, in which the flow guide defines a flow path and an outlet, which flow path is configured to direct the flow of air heated by the in-line heater into the combustion zone in a direction away from, or parallel to. the access area.
3. A domestic fuel burning stove according to claim I or 2, in which the flow guide comprises an enclosed flow conduit defined in a structure of the domestic fuel burner.
4. A domestic fuel burning stove according to claim 3. in which the structure is a side wall.
5. A domestic fuel burning stove according to claim 3 or 4, in which the structure comprises a thermally insulalive lining of the fuel burner.
6. A domestic fuel burning stove according to claim 5, in which the in-line heater is at least partially disposed within the layer of thermally insulative lining.
7. A domestic fuel burning stove according to any preceding claim, in which the flow guide defines a flow path which changes the direction of the flow from the fan to the combustion tone.
8. A domestic fuel burning stove according to claim 7, in which the fan is located on a rearwardly facing surface of the burner, opposite the access area, and in which the flow path guides the flow of air initially towards the access area before changing the direction of the flow prior to the flow entering the combustion zone.
9. A fuel burning stove comprising: a combustion zone: a layer of thermally insulativc material bordering the combustion zone; a fan outside the combustion zone; an flow guide for conveying air from the fan to the combustion zone, the flow guide at least partially passing through the layer of thermally insulative materiah an in-line heater disposed within the flow guide; wherein the in-line heater is at least partially disposed within the layer of thermally insulative material.
10. A fuel burning stove according to claim 9, in which the in-line heater is fully contained within the thermally insulative material.
11. A fud burning stove according to claim 9 or 10. in which the flow guide comprises a conduit defined within the thermally insulativc material, having an inlet end and an outlet end, in which the in-line heater is spaced from the inlet end and the outlet end.
12. A fuel burning stove according to any of claims 9 to 11, in which the flow guide has a cross section which reduces downstream of the in-line heater.
13. A fnel burning stove comprising: a combustion zone; a fan outside the combustion zone; a flow guide for conveying air from the fan to the combustion zone; an in-line heater disposed within the flow guide; wherein the Ian comprises a rotating impeller.
14. A fuel burning stove according to claim 13. in which the fan is capable of acting as an open vent when deactivated.
15. A fuel burning stove according to claim 14, in which the fan is a centrifugal fan.
16. A fuel burning stove according to any of claims 13 to 15. in which the fan has an inlet and an inlet dosurc mechanism configured to at kast partia'ly close the inlet.
17. A fuel burning stove according to claim 16, in which the inlet closure mechanism is configured to fully close the inlet.
18. A fuel burning stove according to any of claims 13 to 17. in which thc fan is mounted to an exterior surface oI the fuel burner such that an axis of rotation oI the impeller intersects the combustion zone.
19. A fuel burning stove according to any of claims 13 to 18, in which the flow guide defines a reduction in cross sectional area configured to accelerate the flow of air.
20. A fuel burning stove substantially as described herein, with reference to, or in accordance with, the accompanying drawings.