JPS596341B2 - liquid fuel burner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid fuel burner that vaporizes and burns liquid fuel such as kerosene.

In general, in so-called premix combustion, in which fuel and combustion air are mixed in advance and combusted, the ratio between the amount of air and the amount of combustion, that is, the excess air ratio, is kept approximately constant in order to always maintain stable combustion. It is desirable to keep the

Furthermore, when the load on the combustor fluctuates, it is naturally necessary to control the amount of heat generated by the combustor in response, and usually intermittent control of the combustor is performed.

However, intermittent control causes temperature ripples in the load, and the combustor is frequently started and stopped, reducing the reliability of the equipment.

Proportional control is used to solve these problems, but if only the fuel supply amount is increased or decreased in response to load fluctuations, the excess air ratio changes, potentially causing flame blow-off, incomplete combustion, and even sooting. There is.

Therefore, this invention maintains the excess air rate constant.
The present invention provides a liquid fuel combustor that can control the amount of heat generated by the combustor in response to load fluctuations.

Next, an embodiment of the liquid fuel combustor of the present invention will be described with reference to the drawings. FIG. 1 is a diagram mainly showing a circuit diagram applied to the embodiment. 1 is a burner, and 2 is a flame emitted from this burner 1.

Horn Murorado 3 is inserted into Flame 2,
This flame rod 3 is used to detect flame current.

The frame rod 3 is connected to the positive pole of a DC power source 4, and a variable resistor 5 is connected between the negative pole of the DC power source 4 and the burner 1.

This variable resistor 5 is used to set the gate voltage of a programmable uni-junction transistor (hereinafter referred to as PUT) 6, and a movable terminal of the variable resistor 5 is connected to the gate of PUT6.

This causes the flame 2-burner 1 to flow from the flare rod 3.
When a flame current flows through the closed circuit of - variable resistor 5 - DC power source 4 - frame rod 3, a voltage is generated across the variable resistor 5.

The variable resistor 5 has a resistance value rl due to the movable terminal.
Therefore, due to the voltage generated across the variable resistor 5, r2 is applied to the gate of PUT6.
A voltage proportional to 'r, +r2 is applied.

Figure 2 shows the flame current characteristics with respect to the combustion amount at a certain amount of air (constant).If point A is the point of ideal excess air ratio, then the combustion amount will increase from this point If there is a large amount (the excess air ratio becomes small), the flame current increases, and if it is small (the excess air ratio becomes large), it decreases.

That is, since the flame current increases or decreases due to a change in the combustion state, the gate voltage of the PUT 6 increases or decreases.

Since the circuit shown in FIG. 1 is a relaxation oscillation circuit of PUT 6, the oscillation frequency is determined by the value of its gate voltage.

When the gate voltage and the anode voltage of the PUT 6 substantially match, the anode and cathode of the PUT 6 become conductive.

The anode of this PUT 6 is connected to the connection point between the capacitor 7 and the resistor 8, and both ends of the series circuit of the capacitor 7 and the resistor 8 are connected to both poles of the DC power supply 11.

Therefore, when PUT6 is non-conductive, capacitor 7 is charged with a time constant determined by the resistance value R3 of resistor 8 and the capacitance C1 of capacitor 7, and when PUT6 is conductive, the charge of capacitor 7 is passed through PUT6. It is something that is discharged.

Now, as mentioned above, when the anode voltage and gate voltage of PUT 6 almost match, conduction occurs between the anode and cathode, so this anode voltage can be relaxed by charging and discharging the capacitor 7 and resistor 8. By PUT
The period for the gate voltage of 6 is determined.

On the other hand, 9 is a drive circuit, and this drive circuit 9 is a PUT
It is also connected to the cathode of 6 and the negative electrode of DC power source 4,110.

An electromagnetic pump 10 is connected to the output side of this drive circuit 9.

The electromagnetic pump 10 is for supplying liquid fuel such as kerosene to the burner 1.

Further, 12 is a blower for sending combustion air to the burner 1, and the combustion air from this blower 12 is sent to a blow pipe 13.
Air is blown to burner 1 through the

A damper 14 is provided at a predetermined location on the blower pipe 130, so that the amount of air blown to the burner 1 can be adjusted.

This adjustment of the air flow rate is performed by the operating frame 14a. The operating frame 14a is mechanically connected to the movable terminal of the variable resistor 5. By operating the movable terminal of the variable resistor 5, the variable resistor 5 can be adjusted. 5 resistance value r1. In the relationship of r2, when the value of r14° becomes smaller, the damper 14
is designed to reduce the amount of air blown to burner 1.

Now, as described above, when the PUT 6 becomes conductive, the drive circuit 9 is activated and the electromagnetic pump 10 is driven, whereby liquid fuel such as kerosene is supplied to the burner 1 and combustion is performed.

At this time, as described above, the operating frame 14a of the damper 14 is operated in conjunction with the movable terminal of the variable resistor 5, so that the optimum amount of combustion air is sent from the blower 12 to the burner 1 via the damper 14. It will be done.

Figure 3 shows the combustion amount-flame current characteristics when the amount of combustion air is changed.
2. This shows that the air volume decreases in the order of Q3.

Therefore, if the combustion amount is kept constant and the airflow is increased, the flame current will decrease (transfers from point A to point B in the figure).
.

Conversely, when the air volume is reduced, the flame current increases (transfers from point A to point C in the diagram).

Now, in this Fig. 3, if we assume that point A is a point in an ideal combustion state, when the amount of air decreases and the excess air ratio becomes small, the flame current increases, PUT
The gate voltage of 6 becomes high, and the oscillation frequency becomes low.

Therefore, the flame current returns to the original set value, and the operation is performed so that the ideal excess air ratio is always maintained.

Conversely, when the amount of air increases and the excess air ratio becomes thicker, the flame current decreases, the gate voltage of PUT 6 increases, and the oscillation frequency increases.

Therefore, the flame current returns to its original value, and the ideal excess air ratio is always maintained.

Utilizing the above characteristics, the amount of air can be changed by opening and closing the damper 14 to correspond to the load of the combustion machine.

When the amount of air supplied to the burner 1 is increased or decreased, the amount of combustion changes along the dashed line m in FIG.

That is, the wiping operation point is initially operated at point A with an air amount of Q2, and the wiping operation point at which the air amount is increased to Ql shifts to Sl.

Conversely, if the air amount is reduced in Q3, the shift will be made to T.

In other words, this is determined by the sensitivity of this control system.

Ideally, if the sensitivity is infinite, the flame current will not change even if the operating point moves.

Change in combustion amount Note that the sensitivity can be expressed as −□.

In reality, the sensitivity is finite and changes as shown by the dashed line m by the change in flame current.

In this case, the excess air ratio decreases as the transition from 5-A-T progresses.

However, when the amount of air decreases and the excess air ratio becomes small, the combustion speed increases, which makes flashback more likely to occur, and the temperature at the flame opening of the burner 1 becomes abnormally high.

Therefore, the present invention attempts to control the excess air ratio so that it does not become small even when the air amount becomes small, and attempts to operate as shown by the dashed dotted line in Fig. 3. As described above, when the value of r1/)/ becomes smaller by operating the movable terminal of the variable resistor 5, the damper 14 works to reduce the amount of air blown to the burner 1.

As a result, PUT6
The gate voltage increases, the oscillation frequency decreases, and the liquid fuel flow rate decreases.

In other words, the excess air ratio becomes more favorable than when r14 is fixed.

In this way, as shown in Figure 3, by reducing the amount of air from Q1 to Q3, the operating point shifts from S' to 7 along the dashed line m', and the load on the combustor decreases. This prevents abnormally high temperatures at the flame opening to the burner 1 when the combustion amount is reduced.

Furthermore, if the combustion amount is decreased while the resistance value of the variable resistor 5 is fixed, the heat exchange efficiency increases and dew condensation occurs inside the heat exchanger (not shown). As the air excess rate increases during combustion, the heat exchange efficiency decreases, resulting in a higher dew point and less chance of condensation.

As detailed above, according to the present invention, a damper that controls the amount of air blown to the burner of a combustion machine and a movable terminal of a variable resistor that increases or decreases the input signal value of an oscillation circuit whose input voltage changes according to the flame current. When the damper increases the amount of air blown, the setting value of the input signal of the oscillation circuit is changed to the resistance value of the variable resistor so that the fuel flow rate increases, and conversely, when the damper decreases the amount of air blown, the oscillation circuit changes the resistance value of the variable resistor so that the fuel flow rate increases. Since the resistance value of the variable resistor is changed so that the set value of the input signal of the circuit is changed to reduce the flow rate of fuel, even if the load on the combustor is reduced and the amount of combustion is reduced, the abnormally high temperature at the flame nozzle will be maintained. In addition to being able to control the calorific value of the combustor in response to load fluctuations while keeping the excess air ratio constant, it also has the effect of reducing the possibility of dew condensation. It is.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an embodiment of the liquid fuel combustor of the present invention, mainly based on the electric circuit, and Fig. 2 shows the flame current characteristics with respect to the combustion amount when the amount of air is constant in the same liquid fuel combustor. The figure shown in FIG. 3 is a diagram showing the combustion amount versus flame current characteristic when the air amount is changed in the liquid fuel combustor same as above. 1...burner, 2...flame, 3...
... Frame rod, 4, 11 ... DC power supply, 5 ... Variable resistor, 6 ... Programmable uni-junction transistor, 1 ...
... Capacitor, 8... Resistor, 9...
・Drive circuit, 10... Electromagnetic pump, 12...
...Blower, 13...Blow pipe, 14...
··damper.

Claims (1)

[Claims] 1. In a vaporizing liquid fuel combustor that has a combustion control device that detects flame current generated in a combustion flame and uses it as an input signal to an oscillation circuit, and drives a fuel pump using the output of this oscillation circuit, A damper is provided to control the amount of combustion air blown, and a movable terminal of a variable resistor that increases or decreases the input signal value of the oscillation circuit is configured to be linked with an operating frame of the damper, and the damper controls the amount of air blown. When the damper operates to increase the flow rate of the fuel, the set value of the input signal changes the resistance value of the variable resistor so as to increase the flow rate of the fuel, and when the damper operates to decrease the air flow rate, the set value of the input signal changes A liquid fuel burner characterized in that the resistance value of the variable resistor is varied so that a set value decreases the flow rate of the fuel.