DE20112299U1 - Ionization electrode - Google Patents

Description

BUDERUS HEATING TECHNOLOGY GMBH

G 1525 TE-P Z

Description

ionization electrode

The innovation concerns an ionization electrode for flame monitoring according to the preamble of claim 1.

An ionization electrode is used to monitor the presence of a flame in a burner. A current flows along a monitoring path between the electrode wire and a ground potential on the mixing device or flame holder when the fuel/air mixture is ionized. The flame signals are evaluated by an automatic burner control system.

Known ionization electrodes consist of a solid wire, which is enclosed in parts, particularly for fastening, by an electrically insulating body. The ground potential on the mixing device of the burner is usually formed by the aperture for distributing the combustion air. Just like the required ignition electrodes, the flame monitoring device is attached to it with a holder. In addition to temperature resistance, ionization electrodes must also be corrosion-resistant in order to ensure safe operation over a long period of time. For this purpose, an ionization electrode for a burner with a combustion chamber is known from DE 198 17 966 A1, which is provided with a cavity for the passage of coolant.

Particularly in oil blower burners with a blue flame, the ionization current can sometimes be very low because the electrode wire of the ionization electrode is located relatively close to the orifice plate. In this area, the fuel/air mixture is only slightly ionized because the flame only begins at a distance in front of the orifice plate.

The innovation is therefore based on the task of improving flame monitoring and ionization current measurement in a burner, especially gas and oil blower burners.

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According to the innovation, this was solved with the features of claim 1. Advantageous further developments can be found in the subclaims.

The ionization electrode is characterized in that the electrode wire extends into the flame area with an ionized fuel/air mixture and a ground electrode forms the associated ground potential for the monitoring section in this area.

The ground electrode has a channel for the supply of combustion air. This begins upstream of the mixing device and ends in at least one outflow opening in the front area adjacent to the monitoring section. The outflow opening is preferably mounted on the outer surface of the ground electrode. It points away from the center of the flame so that the escaping air flow is essentially directed in the direction of the surrounding burner tube.

In an alternative embodiment, the ground electrode can also have two parallel channels for the supply and discharge of combustion air. One channel begins upstream of the mixing device and runs into the front area adjacent to the monitoring section. There, after a diversion, it merges into the second channel, which preferably opens out again in the area of the mixing device.
Basically, the ground electrode is attached to the holder together with the electrode wire and the electrically insulating body.

The innovation optimizes flame monitoring and ionization current measurement in a burner, particularly gas and oil blower burners. Compared to conventional designs, this results in a higher ionization current yield because the monitoring section that is decisive for the ionization current measurement is located in the direct area of the flame. This is where the most strongly ionized fuel/air mixture is present.
The ground electrode is cooled by a small portion of the combustion air that is diverted before the aperture through the channel for the supply of combustion air. This creates a temperature difference between the electrode wire and the ground electrode, which also has a positive effect on the level of the ionization current. In addition, the cooling air emerging from at least one opening cools the burner tube locally. Here too, the temperature difference between the burner tube and the electrode wire near the monitoring section leads to a higher ionization current.

20.07.2001 /G1525

The drawing shows an example of the innovation. It shows:

Fig. 1: The mixing device of an oil blower burner in a perspective view and

Fig. 2: an ionization electrode with an electrode wire and a ground electrode in section.

The mixing device of an oil blower burner essentially consists of a baffle 1 for distributing the combustion air as it exits into a burner tube 2. The ionization electrode for flame monitoring is attached to the baffle 1 using a holder 3. This consists of an electrode wire 4 with an electrically insulating body 5 and an associated ground electrode 6. The monitoring section 7 between the electrode wire 4 and the ground electrode 6 is used to measure the ionization current.

Inside the ground electrode 6 there is a channel 8 for the passage of combustion air. The channel 8 begins upstream of the aperture 1 and opens into outflow openings 9 on the jacket surface in the front area adjacent to the monitoring section 7. These point away from the center of the flame and distribute the escaping air flow towards the wall of the burner tube 2.

20.07.2001 /G1525

Claims (6)

1. Ionization electrode for flame monitoring in a burner, in particular a gas or oil blower burner, consisting of an electrode wire for measuring ionization current on a monitoring path against an associated ground potential, an electrically insulating body enclosing the electrode wire in partial areas, and a holder for fastening the arrangement in the area of the mixing device of the burner, in particular on a baffle for distributing the combustion air, characterized in that the electrode wire ( 4 ) extends into the flame area with an ionized fuel/air mixture and a ground electrode ( 6 ) forms the associated ground potential for the monitoring path ( 7 ) in this area. 2. Ionization electrode according to claim 1, characterized in that the ground electrode ( 6 ) has a channel ( 8 ) for the supply of combustion air, which begins upstream of the mixing device and opens into at least one outflow opening ( 9 ) in the front area adjacent to the monitoring section ( 7 ). 3. Ionization electrode according to one of claims 1 or 2, characterized in that the at least one outflow opening ( 9 ) is arranged in the front region adjacent to the monitoring section ( 7 ), preferably on the outer surface of the ground electrode ( 6 ). 4. Ionization electrode according to one of claims 1 to 3, characterized in that the at least one outflow opening ( 9 ) in the ground electrode ( 6 ) points away from the center of the flame, preferably in the direction of a surrounding burner tube ( 2 ). 5. Ionization electrode according to claim 1, characterized in that the ground electrode ( 6 ) has two parallel channels ( 8 ) for the supply and discharge of combustion air, wherein one channel ( 8 ) begins upstream of the mixing device and runs into the front area adjacent to the monitoring section ( 7 ), and there, after a deflection, merges into the second channel, which preferably opens out again in the area of the mixing device. 6. Ionization electrode according to one of claims 1 to 5, characterized in that the ground electrode ( 6 ) is attached to the holder ( 3 ) together with the electrode wire ( 4 ) and the electrically insulating body ( 5 ).