JPS6130038Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a flame detection circuit for a combustor, and particularly relates to an improvement in its extinguishing detection means.

Conventionally, when this type of flame detection circuit is used in an oil gasification premixing type combustor, flame rectification is used to obtain a stable combustion state, and feedback control of combustion by flame current is performed. was. When a microcomputer or the like is used as a control device for this control, the response of the control circuit is fast, and the control amount becomes unstable unless the ripple component of the input signal to the control circuit is sufficiently removed. On the other hand, if the ripple component is removed, the time delay of the input signal becomes large, which delays the detection of the flame extinguishing state, which may cause a combustor accident. Furthermore, if the insulation between the electrodes that generate the flame current deteriorates, alternating current components will be mixed into the flame current, resulting in abnormal combustion control characteristics, so it is necessary to reliably detect the deterioration of the insulation between the electrodes.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and one embodiment of this invention will be explained below with reference to the drawings.

In the figure, 1 is a metallic burner body, 2 is an electrode provided near this burner body 1, 3 is a resistor RA connected to this electrode, and 4 is this resistor RA.
The resistor RB is connected in series with 3. This resistor RB4 includes a resistor RB ₁ 4a connected in series,
It is composed of a variable resistor VRB4b and a resistor RB ₂ 4c, and a capacitor CA5 and a constant voltage diode ZD6 are connected in parallel. Above resistor RB
A power source 7 for applying an alternating voltage is provided between the burner body 1 and the burner body 1 . This power source 7 is composed of an AC transformer 7a and a resistor R27b. 8 is an equivalent circuit of the flame generated in the burner body 1, which is equivalent to a resistor R38a and a rectifier 8b. 9 is capacitor C1, variable contact 4 of variable resistor VRB4b
d and the resistor RB ₂ 4c. 10
shows a combustion control circuit composed of resistor RA3, resistor RB4, power supply 7, and other elements. Note that a compensating element 11 consisting of a resistor and a diode is provided in parallel with the resistor RA3. A resistor RC 12 is composed of a resistor RC ₁ 12a and a resistor RC ₂ 12b, and a capacitor B13 is connected in parallel to the resistor RC12. 14 is a capacitor C2, which is connected in parallel to the resistor RC ₂ 12b. A fire extinguishing detection circuit 15 is provided independently of the combustion control circuit 10, including a resistor RB12, a capacitor CB13, and a capacitor C214.

In the above flame detection circuit, when a flame is generated in the burner body 1, the variable resistor VRB4b is
The voltage generated between the variable contact 4d and the resistor RB ₂ 4c
_V10 is smoothed by a capacitor C19, and the amount of fuel supplied to the burner body 1 is feedback-controlled. The output voltage of the combustion control circuit 10 in this case, that is, the voltage _V10 at the variable contact 4d, is plotted on the vertical axis, and the resistance value of the equivalent circuit 8 corresponding to the flame is plotted on the horizontal axis, as shown in FIG. has been done. The output voltage V ₁₀ of the combustion control circuit 10 is determined by the resistor RA3 and the compensation element 11 when the resistance value of the equivalent circuit 8 becomes low (that is, when the insulation between the burner body and the electrode deteriorates). compensation has been made. On the other hand, the voltage _V15 generated across the resistor RC12 of the extinguishing detection circuit 15 has a small extinguishing detection time constant due to the capacitor C214 having a smaller capacity than the capacitor C19. This extinguishing detection circuit 1
5, no compensation is made for the deterioration of the insulation between the burner body 1 and the electrode 2, and the capacitor CB
13 bypasses the alternating current component flowing through the circuit 15, so that when the insulation deteriorates, the output voltage _V15 drops rapidly as shown in FIG. By comparing the above output voltage V ₁₅ with the voltage of a predetermined extinguishing detection level and extinguishing the burner body 1 when the output voltage becomes low, the insulation between the burner body 1 and the electrode 2 deteriorates. It is possible to prevent abnormal combustion in combustion equipment.
In Fig. 2, the insulation resistance between the burner body 1 and the electrode 2 is changed under the condition that the flame current is constant, but when the insulation resistance value is from ∞ to 1MΩ, the combustion control voltage V ₁₀ is almost constant. If it becomes less than 1MΩ, it changes rapidly, but the extinguishing detection voltage V ₁₅
When the insulation resistance falls below 10 MΩ, it rapidly decreases with ripples. Therefore, the above insulation resistance decreases and the combustion control voltage decreases.
Before the feedback control of the burner body 1 by _V10 becomes abnormal, the burner body 1 can be extinguished by changing the extinguishing detection voltage _V15 .

As described above, according to this invention, in the flame detection circuit, a resistor RA connected to an electrode provided near the burner body, a resistor RB connected in series to this resistor RA, and a resistor RB connected to an electrode provided near the burner body. It consists of a power source that applies an alternating voltage between the capacitor CA, the resistor RB, and the burner body, which are installed in parallel, and a combustion control circuit that controls the fuel supply to the burner body, and is independent of this combustion control circuit. The resistor RC includes a resistor RC and a capacitor CB connected in parallel between the electrode and the power supply side of the resistor RB. The fuel supply control signal is obtained from the partial pressure of the combustion control circuit by the resistor RB, and the extinguishing detection signal for extinguishing the burner body is obtained from the partial pressure of the extinguishing detection circuit by the resistor RC. Before the insulation between the burner body and the electrodes deteriorates, the combustion control voltage from the combustion control circuit changes, and combustion control becomes abnormal, the burner body is combusted by the extinguishing detection voltage from the extinguishing detection circuit. This can improve the safety of the combustion device including the burner body.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of this invention, and Figure 2 is the combustion control voltage versus insulation resistance (horizontal axis) in the circuit of Figure 1 under constant flame current conditions.
FIG. 2 is a characteristic diagram of V ₁₀ and extinguishing detection voltage V ₁₅ . In the figure, 1 is the burner body, 2 is the electrode, 3 is the resistor RA, 4 is the resistor RB, and 5 is the capacitor.
CA, 7 is a power supply, 10 is a combustion control circuit, 12 is a resistor RC, 13 is a capacitor CB, and 15 is a fire extinguishing detection circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] An electrode provided near the burner body, a resistor RA connected to this electrode, a resistor RB connected in series to this resistor RA, a capacitor CA provided in parallel to this resistor RB, and the above resistor RB. A combustion control circuit that applies an AC voltage between the burner body and the burner body, and a combustion control circuit that controls the fuel supply to the burner body, and the power supply side of the electrode and the resistor RB independently of this combustion control circuit. A fire extinguishing detection circuit is equipped with a resistor RC and a capacitor CB connected in parallel to the burner body, and the fuel supply is controlled from the partial pressure of the combustion control circuit by the resistor RB. A flame detection circuit characterized in that it obtains a signal and also obtains an extinguishing detection signal for extinguishing the burner main body from the partial pressure of the extinguishing detection circuit by the resistor RC.