GB2121948A

GB2121948A - Gas burner

Info

Publication number: GB2121948A
Application number: GB08300042A
Authority: GB
Inventors: John Valdemar Holbek; Mats Molander
Original assignee: Jens Villadsens Fabriker AS
Current assignee: Jens Villadsens Fabriker AS
Priority date: 1982-06-17
Filing date: 1983-01-04
Publication date: 1984-01-04
Also published as: GB2121948B; DE3248221A1; DK147804B; DK273482A; DK147804C; GB8300042D0

Abstract

A burner for gas heating, comprising a feeding chamber with two sets of gas outflow openings 10 and 11, 12 each opening of one set 10 having a cross-sectional area above 3 mm<2>, and each opening of the other set 11, 12 having a cross- sectional area below 3 mm<2>, the total cross-sectional area of the relatively small gas outflow openings amounting to less than 25% of the total gas outflow area. The burner provides a stable and rectilinear flame front. <IMAGE>

Description

SPECIFICATION Gas burner The invention relates to a burner for gas heating, which burner comprises a feeding chamber which is in direct communication with a number of outflow openings for a mixture of fuel and air, said openings being placed side by side (these openings will in the following be referred to as gas outflow openings). The invention relates particularly to a burner for the gas heating of the bituminous binder of a bitumen coated covering material, such as bitumen felt, before this is laid on a supporting surface.

Lamellar burners, whereby is to be understood gas burners, the gas outflow opening of which is subdivided by means of a grid into a number of closely adjacent separate gas outflow passages, are well known for indoor use. Such lamellar burners produce a rectilinear flame front which is situated at a constant distance from the openings of the gas outflow passages.

It has been attempted to utilize these favourable properties of a lamellar burner in the heating of the underside of bitumen felt rolls in connection with the laying of bitumen felt on a roof surface, viz. by replacing the row of separate gas burners mounted on a common holding bar, as normally used for this purpose, by one elongated lameller burner. It has been found, however, that the flame obtained by means of such a lamellar burner is very sensitive to varying gas pressure and to gusts of wind and hard wind, and the burner is therefore not suitable for use in connection with gas bottles and for outdoor use.

It is the object of the invention to provide a gas burner by means of which a stable flame having a rectilinear flame front can be produced.

With the object in view, the burner according to the invention comprises a feeding chamber which is in direct communication with a number of gas outflow openings placed side by side, said gas outflow opening consisting of two different sets of such openings, each opening of one set having a cross-sectional area above 3 mm2, each opening of the other set having a cross-sectional area below 3 mm2, the total cross-sectional area of the relatively small gas outflow openings amounting to less than 25% of the total gas outflow area.

The invention is based on the recognition that when the cross-sectional area of the gas outflow openings is increased in order to obtain a suitably high development of heat, the above mentioned sensitivity to varying gas pressure and to gusts of wind and hard wind is increased, but this sensitivity can be reduced or entirely eliminated by simultaneously providing a suitable number of gas outflow openings having a relatively small crosssectional area.

Thus it has been found that the flames formed by means of the relatively small gas outflow openings are much more stable than the flames formed at the relatively large openings and that the former act as supporting flames, which in the case of extinction of the larger flames continuously re-ignite the outflowing gas.

Owing to the increased flame stability obtained by the burner according to the invention, the possibilites of control particularly at low gas supply rates are substantially increased as compared with the known burners.

A further advantage of the burner according to the invention is that it has a substantially lower noise level than the known burners. The latter normally has a noise level of 85-90 db-A, whereas the noise level of the burner according to the invention is normally below 60 db-A.

A preferred embodiment of the burner according to the invention comprises an elongated distributing chamber with relatively large gas outflow openings arranged in a row that extends in the longitudinal direction of the distributing chamber and is parallel to a row of relatively small gas outflow openings.

With this construction of the burner a long and stable flame front can be produced. This is especially of great importance when the burner according to the invention is to be used for the heating of bitumen felt rolls. In this case the burner can be placed at such a distance from the bitumen felt roll that the development of heat is concentrated in an elongated zone lying close to the surface of the bitumen felt roll and extending across the full width thereof. Thereby a substantially improved fuel economy is achieved, as has been proved in practical tests in which the gas consumption was determined when using a known burner arrangement comprising six separate burners per meter, and when using a burner according to the invention, for the heating of the underside of a length of bitumen felt.In the former case where the length of the flames varied and the flames flickered away from the zone in which it was desired to concentrate the heating, the gas consumption was about 1 8 kg/h, while in the latter case the gas consumption was 6 kg/h.

Owing to the fact that the burner according to the invention produces a stable and stationary flame front, the fire risk, when using the burner according to the invention, is also substantially smaller than when using the known burners where the flames formed in the separate burners are liable to be bent at the occurrence of hard wind or gusts of wind, and may be directed away from the zone in which heating is desired.

A particularly stable flame having a rectilinear flame front can be obtained by arranging a row of relatively small gas outflow openings on each side of and parallel to the rowbf relatively large gas outflow openings. The relatively large gas outflow openings are e.g. in the form of circular holes having a diameter of about 4 mm, bored in a plate extending from one end to the other of the elongated distributing chamber. The row or rows of relatively small gas outflow openings are preferably formed by mounting a wave-shaped plate in which the wave tops are parallel to the gas flow direction between two closely adjacent plane plates, this construction being stable and cheap to produce.

In order to prevent the back-flashing of flames with the result that the combustion will take place in the feeding or distributing chamber, it is preferable to provide at this location a net through which the mixture of fuel and air is forced to pass before reaching the relatively large gas outflow openings.

In another preferred embodiment of the burner according to the invention, the feeding chamber is constructed in the form of a flat funnel, the means for supplying the mixture of fuel and air being arranged at the tip of the funnel, and the gas outflow openings being arranged at the opposed end face. When using such a feeding chamber a particularly uniform distribution of the combustible mixture over the gas outflow openings is obtained, and thereby also a particularly uniform flame front.The means for supplying the mixture of fuel and air preferably consists of a central fuel pipe having an outflow opening in the form of a nozzle, and a conical hood surrounding said fuel pipe and provided at its rear end with air intake openings, said hood having a conical shape such that air is sucked into the feeding chamber as a consequence of the ejector effect produced by the ejection of fuel through the fuel nozzle.

By this concentric arrangement of the fuel pipe and the hood with air intake openings a particularly good mixing of fuel and air is obtained.

In practice the area of the relatively somali gas outflow openings preferably amounts to between 1 and 10% of the total gas outflow area.

The invention will now be further described with reference to the drawings, in which Fig. 1 shows a vertical section through a preferred embodiment of a burner according to the invention, Fig. 2 shows a front view of the burner opening of the burner according to Fig. 1, Fig. 3 shows diagrammatically a vertical section through an apparatus for the laying of bitumen felt, comprising a burner according to the invention, Fig. 4 shows a vertical section through another preferred embodiment of the burner according to the invention, and Fig. 5 shows the burner according to Fig. 4 in plan view.

The burner shown in Fig. 1 and Fig. 2 comprises a gas feeding chamber 1, to which a combustible gas mixture can be supplied through a supply pipe 2. The gas feeding chamber is subdivided into two enclosures 3 and 4 by means of a partition 5 constructed with flow passages 6 in the zone adjacent the inner wall of the gas feeding chamber. The gas feeding chamber has a gas flow outlet 7, in which a net 8 is mounted, and in front of that an insert consisting of a central plate 9 with a set of holes 10 having a diameter of about 4 mm. On each side of the said plate and parallel thereto is arranged a wave-shaped plate 11 which is enclosed between a plate 12 2 and the inner wall of the gas flow outlet, thereby to form two rows of small gas outlet passages 14.

Owing to the presence of the partition 5 and the passages 6 provided therein differences in the rate of supply of the gas mixture to the portion 3 of the feeding chamber lying behind the partition will be equalized, whereby the influx of combustible gas mixture to the gas flow outlet can be maintained substantially constant. The outflow of gas will take place both through the holes 10 in the plate 9 and through the passages formed between the wave-shaped plates 11 and the plates 12 and the inner wall 13 of the gas flow outlet. The last named passages have a crosssectional area below 3 mm2.

The net 8 serves to prevent back-flashing of flames to the feeding chamber 1.

The apparatus shown in Fig. 3 comprises a frame 20 which at one end supports a shaft 21 which is passed through the central hole of a bitumen felt roll 22. A handling bar 23 is attached to the other end of the frame 20. Also mounted on the frame 20 is a burner 24 according to the invention. This burner has an air supply pipe 25 with holes 26 and a gas supply pipe 27 mounted in the pipe 25 and terminating in a gas nozzle 28. The pressure relief taking place when the gas supplied to the nozzle 28 flows out through that nozzle will produce a vacuum in the air supply pipe 25, whereby air is sucked in through the holes 26.

The burner shown in Fig. 4 and Fig. 5 comprises a flat funnel-shaped feeding chamber 31 having a gas outlet 32 in which two sets of gas outflow openings are provided in the same manner as shown in Fig. 1 and Fig. 2.

A hood forming a passage 33 having a circular cross section and being open at both ends is connected to the top end of the funnel-shaped feeding chamber 31. In the central axis of this passage is mounted a fuel pipe 34 which terminates in a nozzle 35 located at the ingress to the passage 33. The fuel pipe 34 is held in position in the passage 33 by means of a strap which is attached to the rear end of the passage 33 and carries a screw nipple 36 through which the fuel pipe 34 extends.

When fuel under pressure flows through the fuel pipe 34, the ejector effect thereby produced will cause air to be sucked into the feeding chamber 31 through the rear end of the passage 33. The sucked-in air is thoroughly mixed with the fuel in the feeding chamber before the mixture thus obtained reaches the gas outlet 32.

Claims

1. Burner for gas heating, comprising a feeding chamber which is in direct communication with a number of gas outflow openings placed side by side, said gas outflow openings consisting of two different sets of such openings, each opening of one set having a cross-sectional area above 3 mm2, each opening of the other set having a cross-sectional area below 3 mm2, the total crosssectional area of the relatively small gas outflow openings amounting to less than 25% of the total gas outflow area.

2. Burner as in claim 1, in which said feeding chamber has an elongated cross section, and said relatively large gas outflow openings are arranged in a row which is parallel to the longitudinal direction of said chamber and to a row of said relatively small gas outflow openings.

3. Burner as in claim 2, in which a row of said relatively small gas outflow openings is arranged on each side of said row of relatively large gas outflow openings.

4. A movable gas burner for the heating of roofing felt rolls in connection with the application of roofing felt to roof surfaces substantially as hereinbefore described with reference to the accompanying drawings.

4. Burner as in claim 1, in which said relatively large gas outflow openings are holes with circular cross section.

5. Burner as in claim 1, in which said relatively small gas outflow openings are constituted by the interspaces between a wave-shaped plate and two parallel plane members enclosing same.

6. A burner for gas heating, substantially as hereinbefore, described with reference to and as shown in the accompanying drawings.

New claims or amendments to claims filed on 26 July 1983 Superseded claims 1-6 New or amended claims: CLAIMS

1. A movable gas burner for the heating of roofing felt rolls in connection with the application of roofing felt to roof surfaces, said gas burner comprising a feeding chamber and a plurality of gas outflow openings discharging in use essentially horizontal gas streams and provided in an elongated horizontal gas discharge outlet of said feeding chamber, said gas outflow openings comprising at least one row of substantially circular gas outflow openings having a crosssectional area of greater than 3 mm2 and at least one row of closely spaced gas outflow openings having a cross-sectional area of less than 3 mm2, the two rows of gas outflow openings being substantially parallel and extending substantially longitudinally of the gas discharge outlet of said feeding chamber, the total cross-sectional area of the relatively small gas outflow openings amounting to between 1 and 10% of the total gas discharge area.

2. A burner according to claim 1, in which a row of said relatively small gas outflow openings is arranged on each side of said row of relatively large gas outflow openings.

3. A burner according to claim 1, in which said relatively small gas outflow openings are constituted by the interspaces between a waveshaped plate and two substantially parallel plane members enclosing same.