GB2208703A

GB2208703A - Fuel effect gas fires

Info

Publication number: GB2208703A
Application number: GB8719346A
Authority: GB
Inventors: David James Izzard
Original assignee: GRATE GLOW FIRES
Current assignee: GRATE GLOW FIRES
Priority date: 1987-08-14
Filing date: 1987-08-14
Publication date: 1989-04-12
Also published as: GB8719346D0

Abstract

Refractory material 14 to underlie simulated solid fuel element/s 12 of a simulated solid fuel effect gas fire 10 has forward-facing portions 16 and encourages substantially complete combustion of gaseous fuel 18 in a region 20 below said element/s 12 and in front of said portions 16, close to the surface of said portions with flames being drawn back towards said portions and incandescence of the material thereat, while the core 46 of the material stays relatively cold. The material 14 has air passage means 40 debouching at said surface and gaseous fuel passage means debouching just in front of said surface. Said portions 16 are substantially vertical, and zig-zag in plan view. The top of the material 14 slopes up towards the rear of the fire and has a stepped formation comprising a plurality of separate strata 50, 52, 54 located to one another by tube means 56, 58 having conical/flared portions. There is substantially lower combustion below the elements at the front and rear edges. The fire has user-operable means comprising an aeration shutter 70 to alter the primary air content of the gaseous fuel and comprises a heat-exchanger 76 to utilise heat from flue gases. <IMAGE>

Description

TITLE "Simulated Solid Fuel Effect Gas Fires" BACKGROUND TO THE INVENTION This invention relates to gas fires having the effect of fires burning solid fuel, e.g. coals or logs.

Gas fires throw a proportion of their heat into the room and the remainder escapes with the flue gases. In the case of previous decorative gas fires of the simulated solid fuel effect type, only some 20% of the heat produced is thrown into the room, though this can be increased to some 357o with use of a heat exchanger.

THE INVENTION The present inventor has realised that an important reason for this low efficiency is that a large part of the combustion occurs above the simulated solid fuel elements with a large amount of secondary air being drawn into the combustion at this level, with consequent scattering of heat in all directions and rapid cooling due to convection gases which carry a lot of this heat up the flue.

According to one aspect of the invention there is provided refractory material as claimed in claim 1.

According to another aspect of the invention there is provided a fire as claimed in claim 2.

By producing substantially complete combustion below the simulated solid fuel element or elements, in the void between the same and the refractory material, there is far less convection and the temperatures in the combustion region increase substantially which in itself improves the efficiency of radiation transfer of heat and reduces the heat available for convection to carry up the flue. Coupled with this, the provision of forward-facing portions of the refractory material at this region encourages the radiant heat to be thrown forward into the room rather than upwards into the flue. The combination of these features can produce an efficiency of heat transfer to the room of some 30% (compared with 20% for previous fires) or, with a heat exchanger, some 50% (compared with 35% for previous fires).

For natural gas, the gas combustion equation is:

CH4 + 202 (+ 8N2) ~~~3 CO2 + 2H20 (+ 8N2).

The second and third terms on the left represent air and this equation shows (by Avogadro's law) that one volume of gas requires ten volumes of air for its complete combustion. With the previous gas fires, a large proportion of this air was provided as secondary air drawn into the combustion above the simulated solid fuel elements. An efficient embodiment of the invention can produce a so-called "coke effect" in which a minimum amount of visible flames occurs above the elements. This uses an admixture of about 10% to 15% of primary air, 757. to 80% of secondary air below the of secondary air to produce flames elements and a mere 10% or so/above the elements, the latter being required for the decorative effect but in this case being mainly "blue" (also called "colourless") flames.A more decorative condition can be produced, a so-called "coal effect", in which a maximum amount of visible flames occurs above the elements. This uses an admixture of about 5% to 10% of primary air, 65% to 70% of of secondary air to produce luminous flames secondary air below the elements and 20% or so/above the elements.

In the previous fires, the combustion below the coals was some onethird to one-half of the gas, whereas embodiments of the invention are designed to produce some two-thirds or more of combustion in this region (which is meant herein by "substantially complete combustion"), preferably (as in the examples just given) some 80% (with coal effect) or 90% (with coke effect), the percentage combustion being taken as the amount of primary and secondary air available for combustion at a particular level.

The refractory material may be constructed (e.g. if it is in a single piece) or arranged (e.g. if it is in several pieces) for said region to be close to the surface of said portions. Or, the gas fire as a whole may be so constructed or arranged. For example, if the material or fire has air passage means and gaseous fuel passage means leading separately to said region, this can encourage said region to be close to the surface of said portions.

There is concomitant increase in the temperatures produced in the region and, thus, more efficient room heating.

The material or fire may be constructed or arranged to encourage flames to be drawn back towards said forward-facing portions. This can be the case when said air and gaseous fuel passage means are both arranged to debouch close to said surface. This also contributes to increase in temperatures in the region and efficiency.

Also, the material or fire may be constructed or arranged to encourage incandescence of the material at said portions while the core of the material stays relatively cold. This may be the case when said air passage means are arranged to debouch at said surface and said gaseous fuel passage means are arranged to debouch just in front of said surface. There can then be a substantial increase in the temperatures in the region and in the resulting efficiency.

Said air passage means may comprise channel means within said material. These may be surface channels which are turned into passages by the overlying elements or other parts of the fire.

Alternatively, these channel means may comprise duct means within said material. The gaseous fuel passage means may comprise channel means within said material. These channel means may be surface channels which are turned into passages by surfaces of external bodies such as the overlying elements or other parts of the fire.

Alternatively, these channel means may comprise duct means within said material.

It is considered that the maximum efficiency will occur with said surface of the forward-facing portions being substantially vertical, though design considerations may make it preferable that they should face partly upwards. A particularly efficient design is produced with said surface substantially vertical, and serrated in plan view, preferably being zig-zag in plan view.

The realism of the design may be enhanced by having at least part of said refractory material simulating one or more solid fuel elements, e.g. the top of the refractory material, possibly the centre of this top or the front and/or back edges of this top, e.g.

according to how much of this top will be visible.

An embodiment which combines at once being particularly efficient and realistic is one in which the material or fire is constructed or arranged for the top of said material to slope up towards the rear of the fire. In a particularly efficient form of this sloping top, it has a stepped formation that provides said forward-facing portions. The realism is improved if said stepped formation comprise at least three steps. Manufacture is facilitated if said material comprises a plurality of separate strata. These may be located together by any suitable locating means, e.g.

protuberances and co-operating notches. A particularly useful embodiment is provided if each stratum is located to the next by tube means providing duct means of the material.

Improved efficiency can be obtained if duct means of the material have flared and/or conical portions narrowing in the direction of flow. This can help gather together stray air and/or gaseous fuel. The realism may be improved if the material or fire is constructed or arranged to provide substantially lower combustion below the simulated solid fuel element or elements towards an edge region of the material or fire. This region may comprise the front and rear edges of the material or fire. Such lower combustion may, for example, be a coal effect condition where the centre of the fire has mainly a coke effect condition. A particularly useful feature is the provision of user-operable means to alter the primary air content of the gaseous fuel, which can for example enable the user to vary the degree of coal effect or coke effect throughout the fire.

Such user-operable means may neatly comprise a Venturi tube into an open mouth of which a gas injector debouches and a tube mounted reciprocably on the Venturi tube in the region of said mouth to operate as an aeration shutter0 As mentioned earlier, the efficiency can be greatly improved if the fire comprises a heat-exchanger to utilise heat from flue gases.

The amount of combustion and flame in different parts of the fire can be governed by the resistance of the relevant flow paths, e.g. the diameter of the various ducts and/or the lengths of the paths. The gaseous fuel including primary air can be led to the back of the fire and thence to the burner orifices below the refractory material, so that it travels a shorter distance forward to an orifice debouching into a taller duct and a greater distance forward when debouching into a shorter duct, to produce equivalent basic resistance at the different positions due to the feature of path length.

Reference will now be made by way of example to the accompanying drawings in which: Fig.l is a partly diagrammatic sectional view of a fire embodying the invention; and Fig.2 is a part plan section along the line II-II of Fig.l.

Referring to the drawings, a simulated solid fuel effect gas fire 10 has simulated solid fuel effect elements 12 and refractory material 14 underlying the latter with forward-facing portions 16, the fire 10 and material 14 being constructed and arranged to encourage substantially complete combustion of gaseous fuel (indicated by wavy arrows 18) in a region 20 below said elements 12 and in front of said portions 16.

A gas tap or other control device 22 supplies neat gas (indicated by double-headed arrows 24) to a gas injector 26 which debouches into a Venturi tube 28 where the gas 24 draws in primary air (indicated by plain arrows 30) which mixes with gas 24 in chamber 32 with the aid of baffle 34 to produce the gaseous fuel 18 which exits through orifices 36 in burner orifice plate 38.

Material 14 has air passage means 40 and gaseous fuel passage means 42 leading separately to said region of substantially complete combustion 20, the passage means 40,42 being both arranged to debouch close to the surface of said portions 16, in fact said air passage means 40 being arranged to debouch at said surface and said gaseous fuel passage means 42 being arranged to debouch just in front of said surface, as shown more clearly in Fig.2.

The air passage means 40 are made sufficiently wide to allow the required large quantities of air 30 to flow therethrough to produce the substantially complete combustion. By this construction and arrangement, said region 20 of substantially complete combustion is brought close to the surface of said portions 16, flames 44 are encouraged to be drawn back towards said forward-facing portions 16, and incandescence of the material 14 at said portions 16 is encouraged while the core 46, Fig.2, (behind portions 16) of the material 14 stays relatively cold.

As seen in Fig.l, said air passage means 40 and said gaseous fuel passage means 42 each comprise channel means within said material 14, said channel means comprising duct means within said material.

As seen in Figs.l and 2, the surface of the forward-facing portions 16 is substantially vertical, is serrated in plan view, in fact being zig-zag in plan view.

As indicated by dashed line 48 in Fig.2, the front part of said material 14 may be shaped and coloured to simulate further solid fuel elements such as 12.

The top (upper and forward surfaces) of said material 14 slopes generally up towards the rear of the fire 10, in fact having a stepped formation that provides said forward-facing portions 16 and comprises at least three steps, these being seen in Fig.l as respective separate strata 50,52 and 54, each stratum being located to the next by tube means 56,58 providing duct means (part of 42) of the material 14. As seen, the duct means 42 have conical (60) and flared (62) portions narrowing in the direction of flow (upwards).

While the slight combustion above elements 12 at the centre of the fire 10 produces substantially blue or colourless flames 64, less air is made available towards an edge region of the and material/fire (in fact towards the front and rear edges) so that there is substantially lower combustion below the elements 12 in this region and corresponding flames 66,68 are more luminous: the whole giving a more realistic effect.

So that the user can vary the total appearance of the fire to some degree, there are provided user-operable means 28,70,72,74 to alter the primary air content of the gaseous fuel 18. Said useroperable means comprise the Venturi tube 28, into the open inlet mouth of which gas injector 26 debouches and a tube 70 mounted reciprocably on the Venturi tube 28 in the region of said mouth to operate as an aeration shutter under the action of connecting rod 72 and operating knob 74.

The fire also comprises a heatnexchanger 76 to utilise heat from flue gases 80, in which air 30 entering at the bottom front of the fire below gas tap 22 passes to the back of the fire and then upwards where it splits into a forward stream 77 and a rear stream 78, the two streams being heated in their upward passage and coming together at the top of the fire where they debouch back into the room. The heat is provided by flue gases (indicated by double arrows 80) which pass into a downward channel 82 and then an upward channel 84 before being released into the flue.

The refractory material may be ceramic fibre block, such as that known under the trade name "Procal 50" made by Foseco, possibly with a high-temperature paint as a surface sealant to reduce tendency to break up under heat, or may be a hard ceramic casting having a rating of at least 14000C and preferably at least 2000 C.

Claims

CLAIMS 1. Refractory material to underlie simulated solid fuel element/s of a simulated solid fuel effect gas fire, the material having forward-facing portions and being constructed or arranged to encourage substantially complete combustion of gaseous fuel in a region below said element/s and in front of said portions. 2. A simulated solid fuel effect gas fire having simulated solid fuel effect element/s and refractory material underlying the latter with forward-facing portions, the fire being constructed or arranged to encourage substantially complete combustion of gaseous fuel in a region below said element/s and in front of said portions. 3. Material or a fire as claimed in either preceding claim, constructed or arranged for said region to be close to the surface of said portions. 4. Material or a fire as claimed in any preceding claim, constructed or arranged to encourage flames to be drawn back towards said forward-facing portions. 5. Material or a fire as claimed in any preceding claim, constructed or arranged to encourage incandescence of the material at said portions while the core of the material stays relatively cold. 6. Material or a fire as claimed ln any preceding claim, having air passage means and gaseous fuel passage means leading separately to said region. 7. Material or a fire as claimed in claim 6, in which said air and gaseous fuel passage means are both arranged to debouch close to said surface. 8. Material or a fire as claimed in claim 7, in which said air passage means are arranged to debouch at said surface and said gaseous fuel passage means are arranged to debouch just in front of said surface. 9. Material or a fire as claimed in any one of claims 6 to 8, in which said air passage means comprise channel means within said material. 10. Material or a fire as claimed in claim 9, in which said air passage channel means comprise duct means within said material. 11. Material or a fire as claimed in any one of claims 6 to 10, in which said gaseous fuel passage means comprise channel means within said material. 12. Material or a fire as claimed in claim 11, in which said gaseous fuel passage channel means comprise duct means within said material. 13. Material or a fire as claimed in any preceding claim, in which the surface of the forward-facing portions is substantially vertical. 14. Material or a fire as claimed in any preceding claim, in which the surface of the forward-facing portions is serrated in plan view. 15. Material or a fire as claimed in claim 14, in which said surface of the forward-facing portions is zig-zag in plan view. 16. Material or a fire as claimed in any preceding claim, in which at least part of said material simulates solid fuel element/s. 17. Material or a fire as claimed in any preceding claim, constructed or arranged for the top of said material to slope up towards the rear of the fire. 18. Material or a fire as claimed in claim 17, in which said top has a stepped formation that provides said forward-facing portions. 19. Material or a fire as claimed in claim 18, in which said stepped formation comprises at least three steps. 20. Material or a fire as claimed in any preceding claim, in which said material comprises a plurality of separate strata. 21. Material or a fire as claimed in claim 20, in which each stratum is located to the next by tube means providing duct means of the material. 22. Material or a fire as claimed in any preceding claim, in which duct means of the material have flared and/or conical portions narrowing in the direction of flow. 23. Material or a fire as claimed in any preceding claim, constructed or arranged to provide substantially lower combustion below simulated solid fuel element/s towards an edge region of the material or fire. 24. Material or a fire as claimed in claim 23, constructed or arranged to provide substantially lower combustion below simulated solid fuel element/s towards the front and rear edges of the material or fire. 25. Refractory material to underlie simulated solid fuel element/s of a simulated solid fuel effect gas fire, substantially according to any embodiment hereinbefore described. 26. Refractory material to underlie simulated solid fuel element/s of a simulated solid fuel effect gas fire, substantially according to any embodiment hereinbefore described with reference to and illustrated in the accompanying drawings. 27. A simulated solid fuel effect gas fire comprising refractory material as claimed in any preceding claim. 28. A fire as claimed in any one of claims 1 to 24 or 27, comprising user-operable means to alter the primary air content of the gaseous fuel. 29. A fire as claimed in claim 28, in which said user-operable means comprise a Venturi tube into an open mouth of which a gas injector debouches and a tube mounted reciprocably on the Venturi tube in the region of said mouth to operate as an aeration shutter. 30. A fire as claimed in any one of claims 1 to 24 or 27, 28, or 29, comprising a heat-exchanger to utilise heat from flue gases. 31. A simulated solid fuel effect gas fire substantially according to any embodiment hereinbefore described. 32. A simulated solid fuel effect gas fire substantially according to any embodiment hereinbefore described with reference to and illustrated in the accompanying drawings. AMENDED SET OF CLAIMS

1. Refractory material to be interposed between overlying simulated solid fuel element/s of a simulated solid fuel effect gas fire and burner forwardly-visible means of the fire, the material having external/forward-facing portions at at least two different distances behind the front of the material and being constructed or arranged to encourage substantially complete combustion of gaseous fuel in a region below said element/s and in front of said portions.

2. A simulated solid fuel effect gas fire having simulated solid fuel effect element/s, burner means and refractory material interposed between the element/s and burner means the material having ,rw rdly=vislblë~ ~ ---- - -- 0 /forward-facing portions at at least two different distances behind the front of the material, the fire being constructed or arranged to encourage substantially complete combustion of gaseous fuel in a region below said element/s and in front of said portions.

3. Material or a fire as claimed in either preceding claim, constructed or arranged for said region to be close to the surface of said portions.

4. Material or a fire as claimed in any preceding claim, constructed or arranged to encourage flames to be drawn back towards said forward facing portions.

5. Material or a fire as claimed in any preceding claim, constructed or arranged to encourage incandescence of the material at said portions while the core of the material stays relatively cold.

6. Material ot a fire as claimed in any preceding claim, the material having air passage means for guiding secondary air to said region.

7. Material or a fire as claimed in claim 6, in which said air passage means is adapted to guide air from the rear of the material.

8. Material or a fire as claimed in claim 6 or 7, in which said air passage means is adapted to guide air from the side of the material.

9. Material or a fire as claimed in any preceding claim, having air passage means and gaseous fuel passage means leading separately to said region.

10. Material or a fire as claimed in claim 9, in which said air and gaseous fuel passage means are both arranged to debouch close to said surface.

11. Material or a fire as claimed in claim 10, in which said air passage means are arranged to debouch at said surface and said gaseous fuel passage means are arranged to debouch just in front of said surface.

12. Material or a fire as claimed in any one of claims 9 to 11, in which said air passage means comprise channel means within said material.

13. Material or a fire as claimed in claim 12, in which said air passage channel means comprise duct means within said material.

14. Material or a fire as claimed in any one of claims 9 to 13, in which said gaseous fuel passage means comprise channel means within said material.

15. Material or a fire as claimed in claim 14, in which said gaseous fuel passage channel means comprise duct means within said material.

16. Material or a fire as claimed in any preceding claim, in which the surface of the forward-facing portions is substantially vertical.

17 Material or a fire as claimed in any preceding claim, in which the surface of the forward-facing portions is serrated in plan view.

18. Material or a fire as claimed in claim 17, in which said surface of the forward-facing portions is zig-zag in plan view.

19. Material or a fire as claimed in any preceding claim, in which at least part of said material simulates solid fuel elements

20. Material or a fire as claimed in any preceding claim, constructed or arranged for the top of said material to slope up towards the rear of the fire.

21. Material or a fire as claimed in claim 20, in which said top has a stepped formation that provides said forward-facing portions.

22. Material or a fire as claimed in claim 21, in which said stepped formation comprises at least three steps.

23. Material or a fire as claimed in any preceding claim, in which said material comprises a plurality of separate strata.

24. Material or a fire as claimed in claim 23, in which each stratum is located to the next by tube means providing duct means of the material.

25. Material or a fire as claimed in any preceding claim, in which the material is arranged substantially in a single mass.

26. Material or a fire as claimed in any preceding claim, in which duct means of the material have flared and/or conical portions narrowing in the direction of flow.

27. Material or a fire as claimed in any preceding claim, constructed or arranged to provide substantially lower combustion below simulated solid fuel element/s towards an edge region of the material or fire.

28.. Material or a fire as claimed in claim 27, constructed or arranged to provide substantially lower combustion below simulated solid fuel element/s towards the front and rear of the material or fire.

29. Refractory material to underlie simulated solid fuel element/s of a simulated solid fuel effect gas fire, substantially according to any embodiment hereinbefore described.

30. Refractory material to underlie simulated solid fuel element/s of a simulated solid fuel effect gas fire, substantially according to any embodiment hereinbefore described with reference to and illustrated in the accompanying drawings.

31. A simulated solid fuel effect gas fire comprising refractory material as claimed in any preceding claim,

32. A fire as claimed in any one of claims 1 to 28 or 31, comprising usereoperable means to alter the primary air content of the gaseous fuel.

33. A fire as claimed in claim 32, in which said user-operable means comprise a Venturi tube into an open mouth of which a gas injector debouches and a tube mounted reciprocably on the Venturi tube in the region of said mouth to operate as an aeration shutter.

34. A fire as claimed in any one of claims 1 to 28 or 31,32 or 33, comprising a heat-exchanger to utilise heat from flue gases.

35. A simulated solid fuel effect gas fire substantially according to any embodiment hereinbefore described.

36. A simulated solid fuel effect gas fire substantially according to any embodiment hereinbefore described with reference to and illustrated in the accompanying drawings.