GB2025600A - An ignition device for acetylene burners - Google Patents

Abstract

An ignition device for a burner 4 operating with acetylene, comprises a jet outlet 3 providing an ignition flame 2, characterised in that, a hole 7 in the supply pipe 1 is provided, so that air enters the pipe and mixes with the acetylene. <IMAGE>

Description

SPECIFICATION An ignition device for burners or the like operating with acetylene The invention relates to an ignition device for burners or the like operating with acetylene, with an ignition flame provided via a supply pipe.

Ignition devices of this kind for light signal appliances operating with acetylene, particularly for use at sea, are known. They have an appropriately shaped small pipe with an opening in which a small amount of acetylene gas is burned constantly as an open ignition flame, in the immediate vicinity of the main burner.

Whilst in gas burners for other types of gas, such as propane, hydrogen, town gas, etc., mixing devices are used in which the combustion gas flows out of a nozzle at a high speed, drawing air in by an injector effect, this air then being mixed with the combustion gas in a mixing pipe, ignition devices for acetylene operated with such a small through-put of gas that a flow speed which would allow the addition of air by an injector effect cannot be attained.

The mixing of acetylene with air can therefore only take place at the periphery of the flame, where there is no turbulent flow and the mixing effect is therefore slight. The combustion of the acetylene is therefore frequently incomplete and leads to the formation of soot, first on the ignition device itself and later spreading over the entire burner appliance.

The invention is based on the task of developing an ignition device of the kind described in the introduction in such a way that it operates without forming soot.

The invention lies in the provision of a hole in the supply pipe in the vicinity of the flame which makes possible the entry of the heated and rising surrounding air. In this way, primary air is added to the ignition flame, this being in a section of the flow lying before the combustion point, where mixing can proceed much better. It has been found that despite the small supply speed of the acetylene, the possibility exists of using thermals of rising heated gas for the primary air, and to ensure soot-free combustion at the ignition flame by this method.

It is advantageous if the hole has a horizontally disposed entry cross-section, and is formed by a cut in a vertically extending supply pipe wall and by a part of the wall which is at an angle to the axis of the pipe. With this design, a type of chimney is formed into which the air flowing upwards, drawn up by the rising gas which is heated in the vicinity of the ignition flame or the main flame, can enter and mix with the acetylene being supplied.

One solution which has proved particularly advantageous and simple consists in forming the hole between the lower edge of the vertically extending supply pipe wall and the upper edge of a part of the wall which is pressed inwards at an angle from the outer wall. This embodiment can be realised in a simple way on any pipe, and it has been found that the narrowing of the cross-section occasioned in this way has no effect on the flow of the acetylene for the acetylene supply, whilst an excellent mixing effect is obtained by the entering air.

One embodiment of the invention is shown in the accompanying drawing by way of example, and is explained in the following description.

In the Drawing a supply pipe 1 for an acetylene ignition flame 2 is shown, with a section of pipe which rises substantially vertically and is bent round into the horizontal at the top, having there an outlet hole 3 for the formation of the ignition flame 2. The ignition flame 2 is disposed in the immediate vicinity of the outlet cross-section of a main burner 4, where the main flame 6 forms when the supply is released through the main supply line 5. Acetylene burners like this are used, for example, for navigation signals, and have to send out light signals at specific intervals. This is achieved in that the supply of acetylene through the line 5 is released and shut off again at appropriate intervals.On the other hand, the ignition flame 2 burns continuously, so that when the supply of acetylene gas through the line 5 is released, ignition of the main flame 6 is guaranteed.

Whilst in known ignition flame devices soot is frequently formed since the ignition flame 2 can be supplied with the air required for combustion virtual ly only by mixing at the periphery of the flame, according to the invention a hole 7 in the supply pipe 1 is provided, which is formed between the lower edge 8 on the vertically extending section of the pipe wall of the supply pipe 1 and the upper edge 9 of the wall part 10 which is cut and separated at 8, being pressed inwards at an angle to the axis of the supply pipe 1. Air can therefore enter through the hole 7 in the direction of the arrow 11, and can mix with the supply of acetylene gas flowing in the vicinity of the curve and as far as the ignition flame 2. Improved combustion is obtained by this prior mixing with air, and the formation of soot is avoided.

The entry of air into the supply pipe 1 in the direction of the arrow 11 is effected in that the air heated by the ignition flame 2 or by the burning main flame 6 rises upwards due to its reduced density compared with the surrounding air, and thereby draws up new amounts of air from below, which also have a flow direction upwards from below. Similarly, air coming in contact with the supply pipe 1 is heated by the hot pipe and caused to rise. As the supply pipe 1 is always hot, while the main flame burns only intermittently, the heated air is thus constantly rising upwards. This rising air enters the hole 7 under a kind of chimney effect, and mixes with the acetylene. The construction form shown has proved particularly favourable, although the supply cross-section for the acetylene is some what reduced at the upper edge 9 of the pressed-in wall part 10. However, since the amount of acetylene supplied to the ignition flame 2 is small this does not have a decisive effect. However, it has been found that an excellent prior mixing of air with the acetylene takes place before the ignition flame is reached.

Naturally, it would also be conceivable to provide a part of the pipe wall which was appropriately bent outwards on the pipe 1, on the lower edge of which the inlet opening 7 would then lie. However, the construction example shown can be realised in a very simple way, since it is only necessary to make a horizontal cut in the supply pipe 1 and to press the wall part 10 inwards.

Claims (4)

1. An ignition device for burners or the like operating with acetylene, having a jet outlet to act as a burner for an ignition flame and fed by a supply pipe, characterised in that, in the vicinity of the outlet, a hole in the supply pipe is provided, which makes it possible for the heated and rising surrounding air to enter.

2. An ignition device according to Claim 1, characterised in that the hole has a horizontally disposed inlet cross-section.

3. An ignition device according to Claim 1 or 2, characterised in that the hole is formed by a cut in a vertically extending section of the supply pipe and by a wall part of the pipe which is at an angle to the axis of the pipe.

4. An ignition device according to Claim 3, characterised in that the hole is formed between the lower edge of the vertically extending wall of the supply pipe and the upper edge of the part of the wall which is pressed inwards at an angle from the external wall.