GB2156507A - Gas burner arrangement - Google Patents

Abstract

A gas burner 1 comprises a T-shaped chamber 2 having a gas inlet 4 and exit ports 3, the chamber walls being of ceramic fibre material. A gas injector 5 adjacent the end of inlet 4 entrains air by virtue of the venturi effect. The chamber may have an internal baffle (35, Fig. 6 not shown), and may be integral with a base 20 above which are provided refractory bodies to give a fire with a solid fuel effect. <IMAGE>

Description

SPECIFICATION Gas burner arrangement This invention relates to a gas burner arrangement and more particularly to an arrangement for use in solid fuel effect open gas fires and other gas applicances.

Such fires have been proposed in which a base member is provided for supporting a quantity of refractory bodies, shaped and coloured to represent solid fuel. Gas is fed to a refractory particulate material and the gas issuing therefrom is ignited and burns around the bodies with a generally luminous flame.

The combustion of gas in such a fire is relatively inefficient due to the use of neat gas.

In order to increase the combustion efficiency of these fires, it has further been proposed to inset an air duct into the fire to lead air to some of the spaces between the refractory bodies (secondary aeration) so that at least part of the gas burns with a non luminous flame.

A problem with pre-aerating (primary aeration) existing burners is back-ignition of the gas through the exit ports of the burner to the injector. This occurs due to the back pressure caused by the refractory particulate material.

This imposes a relatively low upper limit on the maximum area of the exit ports which in turn restricts the amount of air/gas mixture available for a suitable visual effect.

The present invention seeks to provide an improved gas burner arrangement. The present invention also seeks to provide a burner arrangement which will enable the gas to burn with a mainly non-luminous flame so as to increase the heat radiation from the refractory bodies and to effectively use the reradiated heat to heat the surface of the burner to provide additional useful radiant heat while minimising the deposit of carbon and carbon like materials, which is a problem with luminous flames. The invention also seeks to overcome or reduce the disadvantages of existing gas burner arrangements and to increase the efficiency of such burners.

According to a first aspect of the present invention there is provided a gas burner comprising a chamber with a gas inlet and a plurality of gas outlets, the chamber walls being of ceramic fibre material.

According to a second aspect of the present invention there is provided a gas burner comprising a chamber with a gas inlet and a plurality of gas outlets, the chamber walls being of such a material and having such a thickness that the outside of the chamber can be at such a high temperature that it glows while the interior is at such a relatively low temperature that back-ignition of gas does not occur.

In a preferred arrangement the burner chamber is tubular and has an air inlet aperture and a gas injector located inside or outside the burner at a predetermined distance from the air inlet aperture and directed to inject gas into the air stream from or to the inlet aperture.

Preferably the air inlet from the air inlet aperture to the burner is formed to produce a venturi effect, the gas injected acting to draw in with it ambient air. Alternatively the air inlet from the air inlet aperture to the burner may be formed as a parallel passage and the gas injected may also entrain ambient air.

Suitably the burner may comprise a tubular chamber element having a Formation with the air inlet, the wall of the chamber opposite to the air inlet being provided with a plurality of exit ports or jets for the gas/air mixture.

Further additional exit jets can be provided through the wall of the chamber above the said plurality of exit jets.

A baffle may be located opposite the air inlet to the burner around which the air/gas mixture must travel before exiting through the jets. This will minimise the formation of luminous flames on the exterior of the chamber in association with the exit jets closest to the air inlet. Alternatively those exit jets closest to the air inlet may be smaller in area to minimise the above mentioned luminous flames.

Preferred embodiments of the present invention will now be described, by way of example, with reference to the drawings, of which: Figure 1 shows, diagrammatically, a form of separate burner arrangement according to a first embodiment of the invention; Figure 2 is a section taken on the burner arrangement of Figure 1; Figure 3 is a diagrammatic perspective view of the burner arrangementof Figures land 2 mounted on a heat reflective base member; Figure 4 shows, diagrammatically a burner arrangement in accordance with a second embodiment of the present invention provided in a base plate; Figure 5 is a diagrammatic view of a burner arrangement similar to that shown in Figures 1 and 2 but with additional exit ports; Figure 6 is a cross sectional view similar to figure 2 showing a modified inner construction of the burner arrangement;; Figure 7 is a view similar to Figure 6 but showing a still further inner construction of the burner arrangement; Figure 8 is a perspective view of a further form of burner arrangement; Figure 9 is a view similar to Figure 8 but showing an additional support element; Figure 10 is a sectional actual view showing the interior of the burner arrangements shown in Figures 8 and 9.

Figure 11 is a front view of a burner arrangement in accordance with a final embodiment of the present invention; and Figure 1 2 is a side view of the burner arrangement of Fig.1 1.

Referring firstly to Figures 1 and 2 there is shown a burner arrangement 1 suitable for use in a solid fuel effect gas fire. The burner comprises a "T" shaped arrangement having the head of the "T" in the form of a generally closed cylinder or chamber 2 having a row of output ports 3 along its face remote from the stem of the "T".

At least the cylinder 2 of the burner is made entirely of heat-insulating and heat-resistent ceramic fibre material, which enables a very high temperature difference to be established across a relatively small thickness of the material. The material is manufactured by blowing an alumino-silicate substance or clay at a high temperature to form fibres, which are then compressed by a vacuum method at ambient temperature, with a binder. The grade of the material is designated by the maximum temperature which it will bear before the material breaks down. The preferred grades for the burners of the present invention are 1 200'C to 1 600 C especially 1400"C.

With a suitable thickness of the ceramic fibre material, heat conduction between the outer and inner surfaces of the head 2 can be minimised, thus permitting the use of exit ports of suitably larger area whilst preventing back-ignition of the air/gas mixture.

Relatively large exit ports 3 can be provided, for example, 1 mm or more in diameter, in the case of circular ports, or 0.5 x 10 mm or larger in the case of slot type ports which has notbeen possible in the past with pre-aerated burners formed from steel or cast iron. With the possibility of larger ports, a better visual burning effect can be achieved since a sufficiently large amount of mixture can pass from the tube 2 to burn behind and between the refractory bodies provided.

In addition the outside of the burner in particular the upper part adjacent the refractory bodies, may be at such a high temperature that it glows from the reradiated heat from the refractory bodies. This provides an enhanced resemblance to a solid fuel fire.

Utilising refractory bodies made from similar ceramic fibre material suitably shaped to reradiate the heat produced between the outer surface of the burner and the under surface of the refractory bodies produces higher temperatures than would normally be the case when burning gas. The additional heat in turn produces additional useful radiant heat available to help heat a room.

The stem 4 of the burner provides an inlet for a gas/air mixture which is fed into the head 2, issuing from the ports 3 thereof for combustion.

In order to obtain the correct gas/air mixture, the gas is fed through an injector nozzle 5 which may be a multi aperture nozzle which is located at a predetermined distance from the aperture 6 of the gas/air inlet 4. The inlet 4 itself is in this embodiment tapered from the relatively large aperture 6 to the considerably smaller aperture 7 into the head 2. This configuration provides a venturi effect when the jet of gas is turned on, the gas then sucking in with it or entraining a quantity of air in the gap between the nozzle 5 and the aperture 6. Thus a suitable gas/air mixture is produced. By suitable selection of the distance between the nozzle 5 and the aperture 6, the amount of so entrained can be controlled.

To minimise back ignition still further and to assist in cross lighting, a number of smaller ports can be situated around and/or between the larger ports as will be described in connection with Figure 4.

Figure 3 shows an arrangement in which the burner 1 is mounted on a base plate 10.

This base plate 10 is also constructed of heat resistant material of low heat conductivity. By suitable selection of the material used, a reradiation effect can be achieved whereby the heat from the underside of the refractory bodies which is produced by the combustion of the gases can be reradiated by the base plate and burner surface thus providing additional efficiency, radiant heat and enhanced visual effect.

Figure 4 shows a burner arrangement produced from ceramic fibre material as a one or more piece, vacuum-formed or hand made construction. In this construction, a shaped base member 20 is provided having a stepped outline on which refractory bodies (not shown) can be positioned to produce the open fire effect. The "T" shaped burner 1 is formed integrally with the base member 20 so that the outlet ports 3 open directly through the base member.

In the arrangement shown here,the larger ports 3 are surrounded by a number of smaller ports 21 which have the object of minimising back ignition and assisting cross lighting.

It should also be appreciated, that in addition to the previously described advantages, the thickness of the walls provide a sound deadening effect on the noise produced by the moving gas in the air inlet such noise being further reduced by the smooth inner construction of the air inlet and burner.

Figure 5 shows a form of burner similar to that shown in Figures 1 and 2. However, in this case, an additional line of ports 31 are provided, located above the original ports 3 which enhance the visual effect.

Alternative cross sections to that shown in Figure 2 are shown in Figures 6 and 7. In Figure 6, a slightly different arrangement of the venturi effect is provided with two narrow portions 32 and 33. A baffle 35 is located opposite to the air inlet, at least in the area adjacent thereto, so that the air/gas mixture has to pass around the baffle, this minimises the formation of luminous flames adjacent to and at the exterior of the ports 3. On the other hand, a basically parallel sided inlet can be used as shown in Figure 7.

Figure 8 shows a modified form of the arrangement shown in Figure 4. In this form the burner arrangement comprises a base portion 40 projecting forwardly and a burner portion proper 41 being hollow as shown in Figure 1 0. Both portions 40,41 are of ceramic fibre material.

Instead of the circular ports 3 in the previous embodiments, slit ports 43 are provided in a line along the front of the burner 41 and further slit ports 44 are located in the upper part of the burner arrangement.

In order to support the refractory material (not shown) above the burner ports 43 and 44, a support plate 45 (Figure 9) may be provided which also allows additional secondary air to be available for combustion around the ports 44 and prevents the refractory bodies from interfering with the combustion process around the ports 44. The additional secondary air can be provided through slots in the side and front of the support plate 45.

The interior of the arrangements of Figures 8 and 9 is shown in Figure 10. Here can be seen the interior chamber 46 of the burner into which projects the air and gas mixture inlet 47. The gas jet 48 is situated to the rear and in this case projects into the venturi port 50 of the air inlet passage 51.

Figures 11 and 1 2 show a further burner arrangement in which the venturi port 60 is located beneath the burner chamber 61 and the air-gas mixture enters the chamber via a stem 65 and an upward-facing port 63 of a manifold 62. The burner has a gas injector nozzle 68 and exit ports 67. The walls of at least the chamber 61 and preferably of the entire unit are of ceramic fibre material.

Typical operating pressures of the abovedescribed burners are 8" Water Gauge for natural gas and up to 14" Water Gauge for LPG (Propane). With the radiant bodies, e.g.

"coals", present the outer surface of the burners may reach a temperature of 1 200'C with the inner surface being at around 450'C, i.e. well below the temperature at which gas breaks down (cracks) e.g. around 700to.

Typical thicknesses of the ceramic fibre wall lie in the range 1 /4" to 1" (0.635cm to 2.54cm).

An advantage of the above described arrangements is that back-ignition is reduced or prevented whilst at the same time permitting larger exit ports than heretofore possible. All burning of gas takes place outside of the burner. Cracking of the gas does not occur within the chamber. In addition the outside of the burner arrangements, at least adjacent the refractory bodies, may glow to provide an improved solid fuel effect. Moreover the need for particulate material within the burner (e.g.

for heat insulating purposes) is avoided. The burners can use natural gas, manufactured town gas and liquid petroleum gas all with a reduced carbon content in the combustion products.

The ceramic fibre material used in the above-described embodiments may be replaced by any other suitable material which is suitably heat-resistant and heat-insulating such that the outside of the chamber can be at such a high temperature that it glows, while the interior is at such a relatively low temperature that back-ignition of the gas does not occur even when using larger exit ports.

Various further modifications may be made to the above described embodiments without departing from the scope of the invention. For example, where a log effect fire is to be produced, the logs themselves may be constructed in the form of burners with suitably positioned outlet parts. A number of burners may be used as desired instead of the single burner described. The gas jet may, if desired, be situated entirely within the burner instead of at a spacing (Figures 1 to 4) or partially within (Figure 10). If the working fire is required to be seen from both sides an additional burner chamber can be situated in an "H" formation with the existing burner and venturi.

If desired the burner may have a secondary air supply (secondary aeration). The secondary air outlet means is preferably located below some or all of the exit ports outside of the burner. The air outlet means may be an aperture defined by walls of ceramic fibre which are of integral construction with the walls of the burner chamber.

Claims (17)

1. Agas burner comprising a chamber with a gas inlet and a plurality of gas outlets, the chamber walls being of ceramic fibre material.

2. A burner according to Claim 1, wherein the gas inlet comprises a tube, gas injection means being provided outside the tube and directed thereat.

3. A burner according to Claim 2, wherein the gas inlet tube provides a venturi effect whereby injected gas entrains air with it.

4. A burner according to Claim 1, wherein gas injection means extend partially into the gas inlet providing a venturi effect, whereby injected gas entrains air with it.

5. A burner according to any preceding Claim, wherein the chamber is generally Tshaped, the stem of the T comprising the gas inlet and said gas outlets being provided at the cross member of the T.

6. A burner according to Claim 5, wherein baffle means is provided within the chamber between the gas inlet and the gas outlets.

7. A burner according to Claim 5 or 6, wherein a plurality of smaller outlets is provided adjacent said first-mentioned outlets.

8. A burner according to any preceding Claim, wherein the chamber is mounted on a heat-reflective base member.

9. A burner according to any of Claims 1 to 7, wherein the burner is formed integrally with a base member, said gas outlets extending through the base member.

1 0. A burner according to Claim 9, wherein an apertured support plate is provided on the base member.

11. A burner according to any preceding Claim, wherein the grade of the ceramic fibre material lies within the range 1200"C to 1600"C.

1 2. A gas burner substantially as herein described with reference to Figs. 1 and 2, Fig.

3, Fig.4, Fig.5, Fig. 6, Fig. 7, Figs. 8 and 10, Figs. 9 and 10, or Figs. 11 and 12 of the accompanying drawings.

1 3. An open gas fire comprising a gas burner according to any preceding claim.

14. A solid fuel effect open gas fire comprising a gas burner according to any of Claims 8 to 10 wherein a plurality of refractory bodies are provided above the base member.

1 5. A gas fire according to Claim 1 4, wherein the refractory bodies are also of ceramic fibre material.

1 6. A gas burner comprising a chamber with a gas inlet and a plurality of gas outlets, the chamber walls being of such a material and having such a thickness that the outside of the chamber can be of such a high temperature that it glows while the interior is at such a relatively low temperature that back-ignition of gas does not occur.

17. As an independent invention, the additional feature of any of Claims 2 to 11.