JPH0362973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present 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 flame by bringing an electrode into direct contact with the flame and utilizing the conductivity of the flame.
There is an optical method that detects ultraviolet rays emitted from flames. 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 of the ignition burner body 1 of the flame contact electrode 4 located at the tip of the flame detector body 3 to detect the presence or absence of a flame. When the fire is extinguished, the resistance between the ignition burner 1 and the flame contact electrode 4 is approximately 500MΩ or more, but if there is a flame F, the resistance is approximately 2MΩ due to the conductivity of this flame, indicating that the flame is present. can be confirmed. However, when a combustion device such as a boiler is cold, an unburned area B called a black zone or oil zone occurs between the oil-using ignition burner body 1 and the flame F, as shown in FIG. 2, mainly during startup. Since this unburned portion B has a relatively high electrical resistance value, the detected resistance value in the flame detector amplifier 6 exceeds 40 MΩ despite the presence of the flame F. Normally, the flame detector amplifier 6 has a four-stage selector switch of 5, 10, 20, and 40 MΩ, which allows the sensitivity to be adjusted, but if an unburned part B occurs, flame detection is impossible. It is. 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 provides a flame detection device that detects the presence or absence of a flame by measuring the electrical resistance of a space where the flame exists, in which the top of an impeller having a conical cross section is connected to the end of an oil burner, and The burner is characterized by the provision of a flame grounding electrode whose tip is further extended and comes into contact with the flame periphery while avoiding the unburned part, and a flame contacting electrode which is located apart from the burner body and whose tip comes into contact with the flame periphery. This is a flame detection device.

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

In FIGS. 3 and 4, the flame ground electrode 5
One end is connected to the impeller 2 by a strong fixing means such as welding, and the other end is arranged so as to extend from the outer periphery of the burner impeller so as to contact the outer periphery of the flame F formed by the ignition burner 1. In this case, for example, when starting a cold boiler in a state where the combustion air temperature is about 50° C. or lower, an unburned portion B may be formed as shown in FIG. 4. The area in which this unburned portion B is normally formed is approximately 50 to 70 mm in radius around the tip of the ignition burner 1. Therefore, in order for the tip of the flame grounding electrode 5 to be always located in the flame F, the flame grounding electrode 5 must be connected from the tip 1a of the ignition burner 1 to the flame grounding electrode
The distance L to the tip of 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 still another embodiment in which the flame ground electrode 5 is formed and arranged separately from the ignition burner body 1 and the flame ground electrode 5 and the ignition burner body 1 are electrically connected, or the flame ground electrode 5 is formed and arranged separately from the ignition burner body 1, or the flame ground electrode 4 and the flame ground electrode 5 are directly connected.

In the above embodiment, since there is a risk that both the flame grounding electrode 5 and the flame contacting electrode 4 will be burnt out if they are placed in a flame, the materials for forming these are SiC, SUS, Ti.
Use heat-resistant materials such as

FIG. 6 shows the structure of a burner section provided with the flame detection device described above. Combustion air A is pressurized by a forced draft fan 20, heated in an air preheater 21, reaches a wind box 23, is given a swirling force in an air register 13, and flows into a 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, the main burner 8
Supply fuel and ignite.

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.

In addition, by combining with an automatic control device for a combustion device and arranging the electrodes so as to avoid the burner axis, deterioration of the electrodes can be prevented and highly accurate automatic control can be performed.

[Brief explanation of drawings]

1 and 2 are side views of an ignition burner having a conventional flame detection device, FIGS. 3 and 4 are side views of a burner having a flame detection device according to an embodiment of the present invention, and FIG. FIG. 6 is a side view of a burner showing a modification of the burner shown in FIGS. 3 and 4, and FIG. 6 is an overall view of a burner device equipped with a flame detection device according to an embodiment of the present invention. 1... Ignition burner body, 2... Impeller, 4...
...Flame contact electrode, 5...Flame grounding electrode.

Claims (1)

[Scope of Claims] 1. In a flame detection device that detects the presence or absence of a flame by measuring the electrical resistance of a space where the flame exists, the top of an impeller having a conical cross section is connected to the end of an oil burner, and the impeller A flame grounding electrode that extends from near the outer periphery and whose tip touches the flame periphery while avoiding unburned parts, and a flame contact electrode that is located apart from the burner body and whose tip comes into contact with the flame periphery. A flame detection device featuring: 2. The flame detection device according to claim 1, wherein the flame ground electrode is connected to an impeller, and its end portion extends in the direction of the burner axis by 50 to 150 mm from the outer periphery of the impeller.