JPH0616291Y2 - Combustion device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a combustion device, and more particularly to a premix combustion device for premixing vaporized gas of liquid fuel such as kerosene and air. is there.

[Prior Art] Conventionally, a naturalization combustor has been developed in which vaporized gas of a liquid fuel such as kerosene supplied by a pump or the like is premixed with air and then burned with blue flame. This type of burner has the characteristics of forming a Bunsen flame similar to that of gas fuel, expelling soot, and having less harmful components such as carbon monoxide (CO), so it has become widely used in heaters and the like. Came. In this combustor, kerosene is supplied by a pump and combustion air is supplied by a blower independently. In addition, in order to cope with changes in pressure loss in the air passage due to dust, etc. and changes over time in the amount of kerosene supplied by the pump, the ion current in the flame is detected and the ion current value takes a maximum value.
Feedback control is performed on the pump drive circuit and blower rotation speed.

FIG. 4 is a configuration diagram showing a combustion device disclosed in, for example, Japanese Utility Model Laid-Open No. 62-81843. In the figure, (1) is an air hole for supplying combustion air, and jets combustion air supplied by a blower (not shown) at high speed. (2) is a fuel kerosene supply pipe, the tip of which is a thin needle shape, and roughly atomizes the kerosene supplied from the fuel tank (4) via the fuel pump (3), Feed to the mixing chamber (5). The mixing chamber (5) is made of a material with good thermal conductivity such as aluminum, is surrounded by a vaporization wall (6) cast in the preheater (7), and has a throttle hole (8), a current plate (9), and an upper part. And a flame hole plate (10). Reference numeral (11) is an ion electrode for detecting the flame (12), and combustion is detected by the detection circuit (13). Reference numeral (14) is a control circuit for controlling the amount of fuel supplied according to the combustion state detected by the detection circuit (13), and also serves as a drive device for the fuel pump (3).

Next, the operation will be described.

After heating the vaporization wall (6) to a predetermined temperature by the heater (7) in advance, combustion air is supplied by the blower (not shown) to the supply hole (1).
Is supplied into the mixing chamber (5). Fuel pumps at the same time (3)
A predetermined amount of fuel is supplied from the supply pipe (2) via the. The kerosene supply is roughly atomized when passing through the supply pipe (2), and further atomization is promoted by the air flow ejected from the air hole (1), and the gas is instantaneously vaporized on the preheated vaporization wall (6). And mix with combustion air. The premixed air is further mixed while passing through the throttle hole (8), the flow velocity distribution is made uniform by the straightening vane (9), and then ignited by the ignition device (not shown) on the flame hole plate (10), Forms a stable flame (12). After ignition, the vaporization wall (6) recovers heat from the flame and the heater input becomes unnecessary. Also, the rectified waveform of the ion current If is observed by the ion electrode (11),
Always monitor the flame, and if it goes out, control circuit (14)
To stop combustion safely.

An example of the ion current average value If by the burner is shown in FIG. 5 (a). In the figure, the horizontal axis is the air ratio μ and the vertical axis is the ion current.
If is shown as a relative value. Input as shown: 3000Kcal / h
r (curve), input: 2000Kcal / hr (curve), input: 10
At 00 Kcal / hr (curve), there is a distribution with a peak at approximately μ = 0.8 to 0.9. After detection of ignition, the control circuit (14) adjusts the pump driving frequency to control the kerosene supply amount so that the ion current If becomes maximum. Hereinafter, this control is referred to as peak μ combustion control. Further, the combustion amount can be adjusted stably by changing the blower amount by the blower voltage or the damper device in the air passage and detecting If and adjusting the kerosene supply amount to the peak value.

The peak μ combustion control will be described with reference to FIG. 5 (b). Fifth
Figure (b) shows the fuel supply amount Qf when the combustion air amount is constant.
Shows the ion current If to the peak μ combustion control, as shown in the figure, by adding ΔQf modulation to the fuel supply amount Qf, detecting the If value for each modulation, and if peaks as shown by the arrow. Qf is to be moved. Note that ΔQf is set to about 10% of Qf in terms of control reliability.

[Problems to be solved by the invention] Since the conventional combustion device is configured as described above, the operation of constantly searching for the peak value of the ion current is repeated,
There has been a problem that the flame constantly fluctuates in response to changes in the air-fuel ratio.

The present invention was made in order to solve the above problems, and an object thereof is to obtain a combustion device which maintains a stable combustion by fixing the combustion state at an air ratio μ showing the extreme value of the ion current If. And

[Means for Solving the Problem] A combustion device according to the present invention is provided with at least one of a supply amount varying means for fuel and combustion air, a means for detecting ion current in a flame, and a means for outputting from this detecting means. If the control means controls the supply amount varying means so that the ion current signal has a maximum value, the control means considers it stable if the rate of change of the ion current signal is within the set value, and then stabilizes it. The supply amount varying means is controlled so as to burn with the drive signal of.

[Operation] The control means in the present invention considers that the ion current signal is stable when the rate of change of the ion current signal is within the set value, and controls the supply amount varying means so that the combustion is performed by the drive signal at the time of stabilization after stabilization. The combustion state is fixed at the air ratio μ showing the extreme value of the current If, and stable combustion can be maintained.

[Example] The operation until the ignition and the combustion at the peak value of μ are realized (peak μ combustion) is the same as that of the conventional example. Further, in this example, in order to confirm the stable peak μ combustion, The rate of change from the previous detection value is calculated for each detection of the ion current If, and the combustion state is settled.

The basic operation of the peak μ combustion control is to search the If peak value by adding the modulation of the change amount ΔQf to the fuel supply amount Qf and checking the increase / decrease of If. It just repeats the control operation in the vicinity. Therefore, If for ΔQf in one control operation (one step)
The change rate ΔIf of Δ becomes significantly smaller near the peak value than when it deviates from the peak value. Utilizing this characteristic,
If the two conditions that ΔIf by control is sufficiently small and such a state is maintained for a certain period are satisfied,
This is regarded as settling (stable state).

FIG. 1 shows a control flow chart until the settling is determined according to the embodiment of the present invention. After ignition (block (20)) as in the conventional case, peak μ control (block (21)) is performed. ΔIf in this control is the set value, in this case 0.10
(10%) is judged (block (22)),
If it is larger than 0.1, the peak μ control (block (21)) is repeated. If it is smaller than 0.1, the duration is judged (block (23)), and the duration ST is a predetermined value, for example 20.
If it is above, it is regarded as settling (block (24)). Duration ST
If it is 20 times or less, the peak μ control (block (21)) is repeated. In this way, ΔIf by control is smaller than the set value,
If two conditions such that such a state is maintained for a certain period are satisfied, it is regarded as settling. The value of ΔIf in the settling judgment, that is, | (If-If ₀ ) / If ₀ | (I
f ₀ ; If before one step, If; If at current step) and duration
It has been confirmed from the aspects of control reliability and responsiveness that ST is preferably about 10% and about 20 times, respectively.

When the settling of the peak μ combustion is confirmed, the kerosene supply amount is held by the control circuit (14) to increase the stability of combustion (flame), and if ₀ at this time is temporarily set to the control circuit (14). Remember. If during subsequent steady combustion and If stored in the above
₀ is compared, and if a significant variation occurs, the peak μ
Control combustion and reset air ratio μ. FIG. 2 shows a control flowchart for resetting the air ratio μ according to the embodiment of the present invention. Settling is performed according to the above (block (24)) and If at the time of settling is set to If ₀ (block (25)). If during the subsequent steady combustion is monitored (block (26)), If is compared with If ₀ stored above (block (27)). This comparison is based on the value of ΔIf, that is, | (If-I
f ₀ ) / If ₀ | (If ₀ ; If, If one step before, If; If at current step)
Is set value, for example larger or smaller than 0.1 is determined. When ΔIf is larger than 0.1 and significant fluctuation occurs, peak μ combustion control (block (21)) and settling (block (24)) are performed again to reset the air ratio μ. As a concrete value of the significant fluctuation, if is stored in consideration of the fluctuation component of If itself, fluctuation of the combustion air amount from the blower, etc.
It is desirable to set it to approximately ± 10% or more of the ₀ value. That is, when the value is smaller than this value, there is a problem that the peak μ combustion shifts again although it is not an abnormality due to the above variation.

In the above, the If change rate ΔIf during μ control is set to be approximately 10% or less as the settling determination condition, but the present invention is not limited to this. For example, as shown in FIG. 3, during settling, the changes in the fuel supply amount Qf and the ion current If have patterns of 3 steps and 2 steps, respectively. Good.

[Advantages of the Invention] As described above, according to the present invention, the supply amount varying means for at least one of the fuel and the combustion air, the ion current detecting means in the flame, and the ions output from the detecting means. In a device provided with a control means for controlling the supply amount varying means so that the current signal has a maximum value, the control means considers the ion current signal to be stable when the rate of change is within a set value, and after stabilization, it stabilizes. By controlling the supply amount varying means so as to burn with the drive signal, it is possible to secure an appropriate air ratio and stabilize the flame during steady combustion, and to improve reliability and comfort. There is an effect that can be obtained.

[Brief description of drawings]

FIG. 1 is a control flow chart showing stability determination control of a control means for a combustion apparatus according to an embodiment of the present invention, and FIG. 2 shows an air ratio reset control of the control means for a combustion apparatus according to an embodiment of the present invention. FIG. 3 is a control flow chart showing the change pattern of the ion current signal If and the combustion supply amount Qf at the time of combustion settling with respect to the elapsed time, and FIG. 4 shows a combustion apparatus according to a conventional example and an embodiment of the present invention. Diagram,
FIG. 5 (a) is a graph showing the relationship between the air ratio μ and the ion current If, and FIG. 5 (b) is a graph showing the relationship between the fuel supply amount Qf and the ion current If during peak μ combustion control. (1) …… Air supply hole, (2) …… Fuel supply pipe, (3) …… Fuel pump, (11) …… Ion electrode, (12) …… Flame, (13)…
… Detection circuit, (14) …… Control circuit.

Claims (1)

[Scope of utility model registration request] 1. A supply amount varying means for at least one of fuel and combustion air, a means for detecting an ion current in a flame, and an ion current signal output from the detecting means so that the supply becomes maximum. In the one provided with a control means for controlling the quantity varying means, the control means considers the ion current signal as stable if the rate of change of the ion current signal is within a set value, and after stabilization, burns with a drive signal at the stable time. A combustion device characterized by controlling a supply amount varying means.