JPS62245018A - Combustion device - Google Patents

Abstract

PURPOSE:To prevent incomplete combustion and back fire from developing by a method wherein combustion conditions in a main burner or a full primary combustion burner are detected and controlled with a pilot burner to burn highly concentrated premixed gas and a flame rod. CONSTITUTION:Because combustion air is divided and fed by an air feed pipe 27 in an air chamber 26, the excess air ratio lambda of premixed gas formed in a vaporizing chamber 4 is set to be 1.0 or less. The premixed gas and a part of the combustion air from the air chamber 26 mix with each other in a mixing chamber 10 so as to turn to comparatively lean mixture having the excess air ratio lambda of 1.0 or more in order to jet in a full primary combustion burner head 8. On the other hand, a part of the mixture from the vaporizing chamber 4 is led through a premixed gas extracting port 31, which is protrusively open to a mixture passage 28, to a pilot burner 30. Because the pilot burner 30 burns under the condition of low excess air ratio, ion current, obtained by inserting a flame rod in the flame produced on the pilot burner and applying electric voltage across the flame and the rod, shows the maximum value when the excess air ratio lambda of the mixture of the pilot burner is about 0.8-0.9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to combustion control means for a full-fire combustion burner that mixes and burns fuel and combustion air.

BACKGROUND OF THE INVENTION A conventional combustion apparatus of this type was constructed as shown in FIG. A mixing plate 3, which also serves as a burner head holder, is disposed at the upper opening of the vaporizing cylinder 2 in which the heater 1 is embedded, and a vaporizing chamber 4 is defined inside the vaporizing cylinder 2. Furthermore, a burner head 8 is disposed above the mixing plate 3, and is composed of a straightening tube 6 having a large number of small holes 5, and a combustion tube 7 made of a wire mesh bag provided outside the straightening tube 6. A mixing chamber 10 is formed inside by the cap 9 that closes the upper end of the 11■■-■■訃□-1■--1-
is divided. Further, on the outside of the combustion tube 7 and the vaporization tube 2, a glass tube 12 through which radiant heat passes through the exhaust passage 11 and an exhaust tube 14 having an exhaust port 13 are provided. Note that the upper end of the exhaust passage 11 is connected to the exhaust cap 1.
It is blocked by 5. On the other hand, an air supply nozzle 16 and a fuel supply nozzle 17 are opened in the side wall of the vaporization cylinder 2, and each nozzle is connected to a fan 20 and a pump 21 via an air supply pipe 18 and a fuel supply pipe 19 (for example, Publication No. 188718/1983). In addition, 22
23 is an oil tank, and 23 is a flame rod that detects the combustion state.

In the above configuration, when the vaporization cylinder 2 is heated to a predetermined temperature by the heater 1, the fan 20 supplies combustion air into the vaporization chamber 4 via the air supply pipe 18 and the air supply nozzle 16,
The pump 21 supplies fuel from the oil tank 22 to the vaporization chamber 4 via the fuel supply pipe 19 and the fuel supply nozzle 17 . The fuel that has entered the vaporization chamber 4 is vaporized on the heated inner wall of the vaporization cylinder and mixed with combustion air to form a premixture with an excess air ratio of 1.0 or more. The premixture flows into the mixing chamber 10 via the mixing plate 3, where it is mixed evenly and then ejected from the small hole 5 of the rectifying tube 6, and is ignited by an igniter (not shown) to the combustion tube. Burns on the surface of 7. Since the combustion tube 7 has a relatively large area, the combustion here is a low-load combustion, and the red heat of the combustion tube 7 accompanying combustion is dissipated through the glass tube 12, so the combustion flame temperature becomes low. Low NOx combustion is performed. The exhaust gas generated by combustion passes through the exhaust passage 11 and is discharged from the exhaust port 13, but at this time, the vaporization tube 2 is heated and heat is recovered.

Problems to be Solved by the Invention However, in the above configuration, the frame rod 2
The problem is that it is difficult to detect combustion using a and to control the air-fuel ratio using it.

Next, the reason will be explained. The characteristics of the flame rod current value when a constant voltage is applied to the frame rod 23 to change the air excess ratio of the premixture in the above configuration are described in the fourth example.
As shown in the figure. As shown in the figure, the flame rod current reaches its maximum at the point where the excess air ratio λ of the mixture is 1.0, that is, the amount of combustion air in the premixture is equal to the theoretical amount of air. Here, since the burner performs full-fire combustion in which secondary air is not supplied to the combustion surface, if the excess air ratio λ of the premixture is less than 1.0, incomplete combustion will occur due to lack of air. Put it away. Furthermore, the excess air ratio λ of the premixture is 1.0
Even if the temperature is above 1.0, the red heat, that is, the temperature, of the combustion tube 7 becomes the highest, so there is a risk that the combustion tube 7 and the straightening tube 6 will overheat and cause backfire. For this reason, in the combustion apparatus having the above configuration, the practical range of use of the premixture with excess air is above point A in Fig. 4, and the threshold value at the ionic current If of the flame rod (0 ~0
7 line), combustion will be stopped by a control circuit (not shown).

However, if the excess air ratio λ of the air-fuel mixture is set at point B in the figure, the ionic current 1 (will become I13, but this current value rB will similarly occur at B' on the low excess air ratio side, Judgment based on simple current value indicates B on the incomplete combustion side.
Since the excess air ratio of '' cannot be detected, it was necessary to also determine the slope of the current value with respect to the excess air ratio. In addition, it is fine if the current value characteristics of the frame rod do not always change as shown by the solid line in the figure, but if the current value characteristics change as shown by the broken line in the figure due to aging or uneven installation of the frame rod, the air Threshold 0 to 0 across the excess rate range
', and there was a problem in that it was not possible to detect the flashback region or incomplete combustion region. Furthermore, if no voltage is applied due to a failure in the voltage application circuit, etc. to the frame rod, the frame rod current value will of course be zero, but the current value judgment section will determine that the current value is below the threshold value O ~ 0'. Because of this, there was a risk that it would be judged as normal.

Means for Solving the Problems In order to solve the above problems, the combustion apparatus of the present invention includes a vaporization chamber to which one of the combustion air dividedly supplied from the fan is supplied to generate a highly concentrated premixture. , an air chamber to which the other combustion air is supplied, and a mixing chamber which receives and mixes the mixture and combustion air from the vaporization chamber and the air chamber to produce a mixture with an excess air ratio of 1.0 or more. In addition, there is a pilot burner that extracts and burns a part of the premixture generated in the vaporization chamber, a flame rod that detects the combustion state of the pilot burner, and a pump or fan that controls the output of the flame rod to reach its maximum value. A control circuit unit for adjusting at least one side is provided.

Effects With the above-described configuration, the present invention detects and controls the combustion state in the primary combustion burner, which is the main burner, by the pilot burner and flame rod that burn a high-concentration premixture. This makes it easier to detect and prevent incomplete combustion and flashback.

EXAMPLE Hereinafter, an example of the present invention will be explained using FIGS. 1 and 2. Incidentally, in FIG. 1, the same parts as those in the conventional example shown in FIG. 3 are given the same numbers, and explanations thereof will be omitted. An air chamber 26 partitioned by an air chamber main body 24 and a partition plate 25 is provided between the vaporization chamber 4 and the mixing chamber 10, and the air chamber 26 and the air supply pipe 18 are connected by an air supply pipe 27. There is. Further, a mixture passage 28 from the vaporization chamber 4 to the mixing chamber 10 is arranged to pass through the air chamber 26, and an air outlet 29 is opened at the connection part with the mixture passage 28 in the upper part of the air chamber 26. are doing. On the other hand, a premixture outlet 31 to the pilot burner 30 protrudes from the mixture road 28, and a premixture outlet 31 protrudes from the mixture road 28.
It opens diagonally on the side. An electrode of the frame rod 23 faces above the pilot burner 30. The ion current H detected by the frame rod 23 is input to the peak detection section 33 of the control circuit 32, and the adjustment section 34 adjusts the fan 20 so that the ion current I (maximizes) based on the signal from the peak detection section 3a.

In the above configuration, when the vaporization tube 2 is heated to a predetermined temperature by the heater 1, the fan 20 and the pump 21 are activated to supply combustion air and fuel to the vaporization chamber 4. At this time, since the combustion air is dividedly supplied from the air supply pipe 18 to the air chamber 26 via the air supply pipe 27, the fuel vaporized in the vaporization chamber 4 and the combustion air supplied to the vaporization chamber 4 via the air supply nozzle 16 are combined. The excess air ratio λ of the premixture formed in the vaporization chamber 4 is set to 1.0μ or less. The premixture formed in the vaporization chamber 4 is uniformly mixed while passing through the mixture passage 28 and flows out into the mixing chamber 10, and the combustion air from the air pipe 27 flows into the air chamber 26 and the air outlet 29. It flows out into the mixing chamber 10 through the. The premixture from the vaporization chamber 4 that has entered the mixing chamber 10 and a portion of the combustion air from the air chamber 26 are mixed in the mixing chamber 10 to form a relatively lean mixture with an excess air ratio of 1.0 or more. This becomes a problem and is ejected into the post-combustion burner head 8. On the other hand, the vaporization chamber 4 is homogenized in the mixture passage 28.
A part of the mixture is led to the pilot burner 30 through the premixture outlet 31 that protrudes into the mixture road 28, and is ignited by an igniter (not shown) to burn. Ignition of the full-combustion burner 8, which is a burner, is performed by the flame of the pilot burner 30. At this time, the pilot burner 30 burns with a low excess air ratio, so the ionic current obtained by inserting the flame rod 23 into the flame and applying voltage is as shown in Figure 2 (8) for the pilot burner alone. It exhibits the characteristics shown in . In FIG. 2 (8), the vertical axis is the ion current value of the flame rod, and the horizontal axis is the excess air ratio λ of the premixture supplied to the pilot burner 30, that is, the premixture formed in the vaporization chamber 4. This shows the ion current value characteristics, and as can be seen from the figure, the excess air ratio λ is 0.8 to 0.
．． The ionic current reaches its maximum value at about 9. If this characteristic is plotted on the horizontal axis with the excess air ratio λ in the primary combustion burner 8, which is the main burner, changing in conjunction with the pilot burner 30, it will become as shown by the solid line in FIG. 2(B). In this case, if the fan 20 is adjusted to adjust the amount of air so that the ion current If reaches its maximum value, combustion will always be maintained at a constant excess air ratio (point 0 in the figure), which will affect the main burner. This is the excess air ratio that will result in optimal combustion.

Note that the broken line in Figure 2 (B) conceptually shows the ionic current characteristics when the flame rod is inserted into the flame of the primary combustion burner, which is the main burner, as in the conventional example. be.

Effects of the Invention As is clear from the above explanation, the combustion apparatus of the present invention divides combustion air into a vaporization chamber that forms a rich mixture of combustion air and vaporized fuel on one side and sends it to a mixing chamber. An air chamber that supplies combustion air to the mixing chamber to form an air-fuel mixture to be combusted in the primary combustion burner head, a pilot burner that takes out and burns the air-fuel mixture formed in the vaporization chamber, and a pilot. Equipped with a detection means to detect the combustion state of the burner, it is possible to easily detect the excess air ratio of the main combustion burner as the excess air ratio of the Pyro 7 burner, so that the ion current can be maximized. By adjusting so that the main burner can maintain an optimal combustion state.

Ignition of the full combustion burner can also be carried out extremely easily by first igniting the pilot burner that burns a rich air-fuel mixture, and then igniting the main burner using the flame of the pilot burner.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a combustion device showing one embodiment of the present invention;
Figures 2 (3) and (B) are characteristic diagrams showing the ion current characteristics of the flame rod inserted into the flame of the pilot burner of the same device, Figure 3 is a longitudinal cross-sectional view showing a conventional combustion device, and Figure 4
The figure is a characteristic diagram showing the ionic current characteristics of a flame rod 7 in a conventional example. 2... vaporizer cylinder, 4... vaporizer chamber, 8...
... Full combustion burner head, 10 ... Mixing chamber, 18 ... Air supply pipe, 20 ... Fan, 21 ... Pump, 23.・Group・Frame rod, 26... Air chamber, 27... Self... Air pipe,
28...Mixture passage, 3o...Pilot burner, 32...Control circuit section, 33...
...Peak detection section, 34...Adjustment section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 = ! 110 pieces

Claims (4)

[Claims] (1) A pump that supplies fuel, a fan that supplies combustion air through an air supply pipe, an air supply pipe that is connected to the air supply pipe and branches the combustion air, and one of the divided combustion air and mixes the fuel. The air excess ratio is 1 between the premixture from the vaporization chamber and the combustion air from the air chamber.
．． A mixing chamber that forms a premixture of 0 or more, an all-primary combustion burner head that burns the premixture from the mixing chamber, and a pilot burner that takes out and burns a part of the premixture formed in the vaporization chamber. , a detection means for detecting the combustion state of the pilot burner, and a control circuit section for driving and controlling the pump and the fan, and the control circuit section controls the operation of the pump or the fan so that the output of the detection means is maximized. A combustion device configured to include an adjustment section that adjusts at least one side, and a peak detection section. (2) The vaporization chamber is divided inside the bottomed cylindrical vaporization cylinder, and an air chamber is connected to the top of the vaporization chamber, and a mixing chamber is connected to the top of the vaporization chamber. The combustion device according to claim 1, further comprising a mixture passage for guiding the mixture. (3) The combustion device according to claim 1, wherein the premixture concentration formed in the vaporization chamber is set to have an excess air ratio of 1.0 or less. (4) The combustion device according to claim 1, wherein the detection means is a flame rod.