JPS58190619A - Flame sensor - Google Patents

Abstract

PURPOSE:To enable the correct sensing of the presence or absence of a flame by a method wherein a flame ground electrode with its one end being contacted to the main body of a burner is formed and arranged, and only an electric resistance of the flame is sensed except the non-combustion part even if the non-combustion part is produced. CONSTITUTION:One end of a flame ground electrode 5 is connected to an impeller 2 by strong fixing means such as welding etc., the other end is arranged to be positioned in the flame F formed by the ignition burner 1. In this case, it is sometimes found that the non-combustion part B is formed, so that the distance L is defined to cause the extremity end of the flame ground electrode 5 to be always positioned in the flame F. Presence or absence of the flame is sensed by detecting an air resistance between the flame electrode 4 and the flame ground electrode 5. If a presence of the flame F is acknowledged, the fuel is supplied to the main burner 8 and ignited. Thereby, irrespective of a presence or absence of the non-combustion part of the fuel, it is possible to detect correctly the presence or absence of the flame.

Description

[Detailed description of the invention] This invention relates to a flame detector with improved detection accuracy.

Flame detectors for burners such as ignition burners use a direct detection method that detects the flame by bringing an electrode into direct contact with the flame and utilizing the conductivity of the flame, and an optical method that detects ultraviolet rays etc. emitted from the flame. There is a method. Among these methods, the optical method does not require a flame contact electrode, but it requires a complicated electrical circuit, which is difficult to adjust, and also has problems such as detecting the flame of another burner while extinguishing a burner and emitting a false signal. be.

Figure 1 shows a direct flame detector. The principle of a direct flame detector is to detect the presence or absence of a flame by utilizing the fact that the resistance value between the burner body and the electrode in contact with the flame is greatly reduced when there is flame due to the conductivity of the flame. It is something to detect. That is, in the figure, the flame detector amplifier 6 detects the resistance between the flame contact electrode 4 located at the tip of the flame detector body 3 and the ignition burner body 1, and detects the presence or absence of a flame. During extinguishing, the resistance between the ignition burner 1 and the flame contact electrode 4 is approximately 500 MΩ or more, but the flame F
If there is a flame, the resistance will be approximately 2MΩ due to the conductivity of this flame.
This confirms that flame F is present. However, if the combustion equipment such as a boiler is cold, the second
As shown in the figure, an unburned area B called a black zone or oil zone is generated between the ignition burner body 1 and the flame F. Since this unburned portion B has a relatively high electrical resistance value, the detected resistance value in the flame detector amplifier 6 exceeds 40 Mfl even though the flame F is present. Usually frame detector amplifier 6 has 5°10,2
There is a four-stage selector switch of 0 and 4oMf'2,
Although the sensitivity can be adjusted, if an unburned part B occurs, flame detection is impossible. In particular, recently, an automatic combustion method has been implemented in which a flame detector detects flames and automatically stops the fuel supply if no flame is detected, so there is a demand for flame detectors with high detection accuracy. There is.

An object of the present invention is to provide a flame detector that always accurately detects the presence or absence of flame regardless of the presence or absence of unburned parts.

In short, this invention is configured to form and arrange a flame grounding electrode with one end in contact with the burner body side, and to detect only the electrical resistance value of the flame, avoiding the unburned part even if an unburned part occurs. .

Embodiments of the present invention will be described below based on the drawings.

3 and 4, one end of the flame ground electrode 5 is connected to the impeller 2 by strong fixing means such as welding,
The other end is placed in the flame F formed by the ignition burner 1.

In this case, for example, when starting the boiler cold when the combustion air temperature is about 50'C or less, the unburned part B
may be formed. Normally, this unburned part B is formed within a radius of about 50 mm centered on the tip of the ignition burner 1.
It is about 70mm.

Therefore, in order for the tip of the flame ground electrode 5 to be always located in the flame F, the distance from the tip 1a of the ignition burner 1 to the tip of the flame ground electrode 5 is preferably about 50 to 150 mm. However, it is not preferable to make the length of the flame grounding electrode 5 longer than necessary because it may cause burnout of the electrode.

FIG. 5 shows a modification of the one shown in FIGS. 3 and 4, in which the flame ground electrode 5 is directly connected to the ignition burner 1.

FIG. 6 shows yet another embodiment in which the flame ground electrode 5 is formed and arranged separately from the ignition burner body 1.
and the ignition burner body 1 are electrically connected, or the flame contact electrode 4 and the flame ground electrode 5 are directly connected.

In the above embodiments, the flame grounding electrode 5 and the flame contacting electrode 4 are made of Sin, since there is a risk of them being burnt out if they are placed in a flame.

Use heat-resistant materials such as SUS and T1.

FIG. 7 shows the structure of a burner section provided with the flame detection device described above. Combustion air A is pressurized by the forced draft fan 20 and heated in the air preheater 21 before reaching the wind box 23, and then given a swirling force in the air register 13 and flowing into the furnace 24. On the other hand, in the ignition burner 1, a pulse igniter 7 electrically generates a spark and ignites it. The presence or absence of a flame is detected by detecting the electrical resistance value between the flame contact electrode 4 and the flame ground electrode 5 in a flame detector amplifier 6. If the presence of flame F is confirmed, fuel is supplied to the main burner 8 and ignited.

By carrying out the present invention, the ignition state of the burner can be detected reliably and there will be no error in burner operation.

Furthermore, by combining it with an automatic control device for a combustion device, it becomes possible to perform highly accurate automatic control.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are side views of an ignition burner having a conventional flame detection device, and FIGS. 3 and 4 are side views of a burner having a flame detection device according to the present invention. 5 and 6 are side views of a burner that is a modification of the burner shown in FIGS. 3 and 4, and FIG. 7 is an overall view of a burner device equipped with a flame detection device according to the present invention. l... Ignition burner body 2... Impeller 4... Flame contact electrode 5... Flame ground electrode Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a device that detects the presence or absence of a flame by detecting the electrical resistance value of a space where the flame should exist, one electrode is used as a flame contact electrode, and the other electrode is used to avoid unburned parts. 1. A flame detection device, characterized in that the flame grounding electrode is arranged at the flame grounding electrode, and the electric resistance value between the flame contact electrode and the flame grounding electrode is detected directly or indirectly through the burner body. 2. The flame detection device according to claim 1, wherein one end of the flame ground electrode is installed on the side of the burner body including the impeller. 3. The flame detection device according to claim 1, wherein the flame grounding electrode is formed and arranged separately from the burner body so that the end of the electrode is located within the flame. 4. The flame detection device according to claim 2 or 3, wherein the distance from the burner tip to the flame ground electrode tip is between about 50 and about 150 mm.