JPH0435646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a premix type liquid fuel combustion device in which vaporized gas of liquid fuel such as kerosene and air are mixed in advance.

[Conventional technology]

Conventionally, the vaporized gas of liquid fuel such as kerosene supplied by a pump etc. is premixed with air,
Subsequently, premixed liquid fuel combustion devices with blue flame combustion have been developed. This type of burner has the characteristics of forming a Bunsen flame in the same way as gas fuel, expelling soot, and containing few harmful components such as carbon monoxide, so it has recently become widely used in heaters and the like.

By the way, since the supply of fuel oil by the pump is performed independently from the supply of combustion air by the blower, the flame rays need to be adjusted in order to cope with changes in pressure loss in the air passage due to dust clogging, etc., and changes over time in the amount of fuel oil supplied by the pump. The ion current inside the pump is detected, and feedback control is performed on the pump drive circuit and fan rotation speed so that the ion current value reaches its maximum value.

FIG. 1 is an explanatory diagram showing the burner configuration in the above-mentioned general liquid fuel combustion device. In the figure, 1 is a combustion air supply hole that blows out combustion air supplied by a blower (not shown) at high speed. I'm starting to let them do it. 2 is a liquid fuel supply pipe such as kerosene, the tip of which is shaped like a fine needle, and is connected to the fuel tank 4.
It serves to atomize the oil supplied via the pump 3 and supply it into the mixing chamber 5. The mixing chamber 5 is made of a material with good thermal conductivity, such as aluminum, and is surrounded by a vaporization wall 6 into which a preheater 7 is cast, and has an aperture plate 8, a rectifying plate 9, and a flame port plate 10 at the top.
have. Reference numeral 11 denotes an ion electrode that detects the flame 12, and together with the control circuit device 13, detects the combustion flame. Note that this control circuit device 13 also serves as a drive device for the pump 3.

Next, the operation will be explained. After the vaporization wall 6 is heated to a predetermined temperature by the heater 7 in advance, combustion air is supplied to the supply hole 1 by a blower (not shown).
is supplied into the mixing chamber 5. At the same time, a predetermined amount of fuel oil is supplied from the supply pipe 2 via the pump 3. The supplied fuel oil is atomized when passing through the supply pipe 2, and the atomization is further promoted by the air flow jetted from the above-mentioned supply hole 1, and the preheated vaporization wall 6
It vaporizes instantaneously at the top and mixes with the combustion air.

Thereafter, this premixture is further mixed while passing through the diaphragm plate 8, and after the flow velocity distribution is made uniform by the rectifier plate 9, it is ignited by an ignition device (not shown) on the flame port plate 10, resulting in a stable flame 12. is formed thereon, and after ignition, heat is recovered from the flame 12 to the vaporization wall 6, so no heater input is required. Further, the rectified waveform of the ion current If is observed by the ion _electrode 11, and the flame 12 is constantly monitored, and if the flame 12 should go out, the control circuit device 13 safely stops the combustion.

By the way, the ion current value I _f due to the flame 12 mentioned above has a typical input as shown in Fig. 2.
At 3000 to 1000 Kcal/hr, the distribution has a peak at approximately μ=0.8 to 0.9. After the ignition is detected, the pump drive frequency is adjusted by the control circuit device 13.
The amount of fuel oil supplied is determined so that I _f is maximized. The control at this time is shown in the flowchart of FIG. In other words, the ion current If several tens of seconds after ignition
is stored in the control circuit 13 and set as a comparison value If ₀ .
Increase the fuel pump drive frequency (hereinafter simply referred to as fuel pump frequency) by a small amount Δf, compare the ion current value If at that time with If ₀ (k = If - If ₀ ), and if the difference k is larger than the predetermined value e, The ion current value If at that time is set as a new comparison value If ₀ , and the fuel pump frequency is further increased by Δf. Thereafter, this operation is repeated, and when the ion current approaches the maximum value, the difference k becomes smaller than the predetermined value e, so the fuel supply amount according to the fuel pump frequency at this time is determined as the fuel supply amount at which If becomes the maximum. Δf of fuel pump frequency
When If becomes smaller than If ₀ due to an increase in If, that is, the difference k becomes smaller than -e, the decrease of Δf is repeated until the absolute value of the difference k becomes smaller than the predetermined value e. In addition, the amount of air blown can be changed depending on the blower voltage, damper device in the air path, etc.
By detecting I _f and matching the fuel oil supply amount to the heater value, stable combustion amount adjustment is possible.

[Problem that the invention seeks to solve]

Since the burner configuration in a conventional liquid fuel combustion device is configured as described above, combustion must always be performed at an air-fuel ratio μ corresponding to the peak value of the ion current, and the air-fuel ratio μ cannot be selected to an arbitrary value. I couldn't do it.

Specifically, μ = 0.7 to increase Bunsen flame stability, and μ = 0.7 to reduce nitrogen oxides (NOX).
It is effective to set the value to 1.3 to 1.5, but this could not be achieved using conventional means.

This invention was made to solve the above problems, and aims to provide a liquid fuel combustion device in which μ can be set to an arbitrary value.

[Means for solving problems]

In other words, in the combustion device according to the present invention, the ion current value I _f is detected in the same way as the conventional device, and once this I _f
After the combustion state is set to an air-fuel ratio μ at which the peak value μ is reached, the control circuit device attempts to adjust the amount of fuel supplied to a predetermined μ.

[Effect]

In the case of this invention, at the time of ignition, I _f is controlled to reach a peak to achieve peak μ combustion, and then the pump drive circuit changes the supply amount of fuel oil to a predetermined amount to perform set μ combustion. Then, I _f is monitored and if it changes, peak μ combustion is performed again and the air-fuel ratio is reset. Further, input changes are made to return to peak μ combustion, and input is adjusted while stable combustion is being achieved.By doing this, it becomes possible to improve the stability of burner characteristics and to set an arbitrary air-fuel ratio.

〔Example〕

In the case of this invention, the ignition and ion current value I _f
The operation until combustion is achieved at μ at which μ reaches its peak value (peak μ combustion) is the same as in the conventional example. When this stable peak μ combustion is confirmed, the air-fuel ratio μ at that time is found to be 0.8 to 0.9 as shown in FIG. supply amount,
The air-fuel ratio (0.8
~0.9) and the desired air-fuel ratio (setting μ combustion). For example, in order to achieve μ = 0.7, which is a highly stable burner performance, the air-fuel ratio during peak μ combustion must be reduced to 0.7/(0.8~0.9)≈0.9~0.8 times, or 10~20%. To do this, all you have to do is increase the fuel supply amount by 10 to 20% without changing the air flow rate. This operation is repeated at regular intervals or every time the combustion amount is adjusted. That is, in the latter case, when changing the air flow rate to change the fuel amount, peak μ combustion is performed again. That is, when the air blowing amount changes, the fuel supply amount is adjusted so that the ion current value If always shows the peak value as described above. Then, when it is confirmed that there is no change in the amount of air blown by the fact that the change in the ion current value If has decreased, etc., the process shifts to the set μ combustion in the same manner as described above. A time chart of changes in the amount of air blown and the amount of fuel oil at this time is shown in Fig. 3.

This method is particularly effective when the air-fuel ratio is high. In other words, when aiming for low NOx and performing combustion with μ = approximately 1.4, after performing the peak μ combustion as described above, the air-fuel ratio μ at this time is determined to be 0.85, and the air-fuel ratio μ is increased by 65% ( 1.4/0.85), i.e. I _f when the fuel supply amount is reduced by 65% and the set μ combustion is reached.
is temporarily stored in the control circuit device 13. Compare I _f during the subsequent steady combustion with the above memorized I _f ,
If a fluctuation occurs, peak μ combustion is performed again to reset the air-fuel ratio.

As described above, by constantly monitoring I _f and detecting fluctuations in the air-fuel ratio, reliability can be improved even in unstable high air-fuel ratio combustion. In addition, when changing the combustion amount, as mentioned above, once the peak μ
Reliability can be further improved by varying the amount of combustion at an air-fuel ratio that allows highly stable combustion to be achieved.

The above describes the case in which the present invention is applied to a Bunsen flame stabilized on a flame port plate. It can also be widely applied to cases where combustion is performed while mixing air with air.

〔Effect of the invention〕

As described above, according to the present invention, a single-peaked signal such as an ion current value is detected from a flame, and after peak μ combustion is performed at the time of ignition, combustion is performed to shift to a predetermined air-fuel ratio. Therefore, it is possible to obtain a combustion device that can perform combustion at any air-fuel ratio while improving ignitability, ability to follow changes over time, and reliability against changes in combustion amount.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing the configuration of a burner in a general liquid fuel combustion apparatus in which the present invention is implemented, and FIG. 2 is a typical measurement example of the ion current in the burner configuration shown in FIG. FIG. 3 is a time chart showing changes over time in the air flow rate and fuel oil amount according to the present invention, and FIG. 4 is a flow chart showing peak μ combustion control. In the figure, 1 is an air supply port, 2 is a liquid fuel supply pipe, 5 is a vaporization chamber, 10 is a flame port plate, 11 is an ion electrode, 12 is a flame, and 13 is a control circuit device.

Claims (1)

[Claims] 1. A liquid fuel supply pipe and a combustion air supply port are opened into a vaporization chamber, and an ion electrode is provided for detecting an output signal value of a flame generated at a flame port plate after passing through the vaporization chamber. In this system, the air-fuel ratio is controlled by changing the fuel supply amount without changing the combustion air supply amount so that the output signal value at the ion electrode has an extreme value during ignition and input changes, and during steady combustion, this 1. A liquid fuel combustion device comprising a control circuit device for controlling the amount of fuel supplied so as to achieve a desired air-fuel ratio proportional to the air-fuel ratio. 2. The liquid fuel combustion device according to claim 1, wherein when the output signal value at the ion electrode changes during steady combustion, the air-fuel ratio is re-controlled to the point where the signal value has an extreme value.