JPS599013B2 - liquid fuel combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid fuel combustion apparatus that preheats and premixes vaporized liquid fuel and combustion air and burns the mixture.

Such liquid fuel combustion devices are often used, for example, as a heat source for hot water boilers.

Combustion heat generated from the combustion chamber is used to preheat the combustion air and vaporize the liquid fuel, and the preheated combustion air and vaporized fuel are mixed at an air-fuel ratio μ (amount of combustion air/theoretical). By premixing and burning so that the amount of air (air amount) is about 1.4 or more, ideal combustion with extremely low generation of soot, CONOX, etc. can be achieved.

However, in conventional liquid fuel combustion devices of this type, the air-fuel mixture is ignited directly by spark discharge, so the temperature of the air-fuel mixture may change depending on the operating conditions of the combustion device (e.g., outside temperature, etc.), or the combustion air may be ignited. This has the disadvantage that ignition delays can easily occur due to changes in the capacity of the blower for supplying air, and this causes the air-fuel mixture filling the combustion chamber to ignite explosively, causing harm to the combustion device.

Figure 1 is a characteristic diagram showing the relationship between mixture temperature and ignition delay when a μ-1.4 mixture is ignited by spark discharge. In the figure, the horizontal axis is the mixture temperature and the vertical axis is the ignition delay time. shows.

FIG. 2 is a characteristic diagram showing the relationship between the air-fuel ratio μ and the ignition delay time using the air-fuel mixture temperature as a parameter, in which the horizontal axis shows the air-fuel ratio μ and the vertical axis shows the ignition delay time.

In FIG. 1 and FIG. 2, the spark discharge energy of the ignition device is the same.

As is well known, if the spark discharge energy is increased, the ignition delay time will be somewhat reduced.

However, in a practical design, the spark discharge energy is at most several tens of kcal/hr, and an increase in spark discharge energy of that degree not only does not significantly improve ignition delay; A high-voltage ignition truss capable of supplying spark discharge energy of .

On the other hand, as shown in Figures 1 and 2, if the spark discharge energy is kept constant, then the air-fuel ratio μ can be decreased.
Alternatively, the ignition delay time can be reduced by increasing the temperature of the air-fuel mixture.

In particular, if μ is set to about 0.9 as shown in FIG. 2, the ignition delay time can be sufficiently reduced even for a relatively low temperature air-fuel mixture.

This invention was made in view of the above points, and has a simple configuration in which a pilot flame is formed by spark discharge, and the main mixture is ignited by this pilot flame. High energy of flame (e.g. 1000 to several thousand kcal/hr)
As a result, a sufficiently short ignition delay time can be obtained without being affected by changes in air-fuel mixture temperature or air-fuel ratio.

A spark discharge device is used to ignite the pilot flame, and the ignition delay time is made sufficiently short by supplying a pilot air-fuel mixture with a sufficiently low air-fuel ratio to the pilot flame port.

The present invention will be described in detail below with reference to examples.

FIG. 3 is a perspective view showing the main parts of a liquid fuel combustion device which is an embodiment of the present invention, FIG. 4 is a cross-sectional view taken along plane 3 shown in FIG. FIG. 6 is an enlarged sectional view of the portion shown in FIG. 4 surrounded by a dashed line and marked with the symbol ■.

In FIGS. 3 to 6, reference numeral 1 denotes a combustion chamber, in which a main air-fuel mixture consisting of a gas obtained by vaporizing liquid fuel such as kerosene and combustion air is combusted.

Reference numeral 2 denotes a combustion cylinder which forms a combustion chamber and at the same time forms a mixing chamber which will be described later.

Reference numeral 3 denotes an air supply hole for introducing combustion air into a mixing chamber 12, which will be described later, by an appropriate blowing means (not shown in the drawings).

4 is a liquid fuel supply pipe, 5 is an atomizer that atomizes the liquid fuel supplied from this liquid fuel supply pipe 4, 6 is an insulator, 7 is an electrode conductor, 8 is a pilot combustion cylinder main body, and 9 is this pilot. This is a pipe tangent mixture supply hole provided on the side surface of the combustion cylinder main body part 8.

Further, reference numeral 10 denotes a pilot flame port through which a pilot air-fuel mixture supplied to the pitant combustion tube main body 8 can be combusted within the combustion chamber 1.

Reference numeral 11 denotes a partition member which transmits a portion of the heat generated in the combustion chamber 1 to the mixing chamber 12 and, in the case of a conventional design, incorporates electric heating means (not shown in the drawings).

12 is a mixing chamber for preheating and premixing the combustion air introduced from the air supply hole 3 and the liquid fuel atomized by the atomizer 5; 13 is a combustion plate provided at the base of the combustion chamber 1; 14 is this combustion plate 13 is a main flame port provided, 15 is a mixture outlet hole provided at the end of the mixing chamber 12 for guiding the main mixture to the rectifying chamber 16, and 17 is a rectifying cover forming the rectifying chamber 16. It is.

In the structure as explained above, the pilot flame port 10
Let A1 be the cross-sectional area of the pilot air-fuel mixture supply hole 9, and A2 be the cross-sectional area of the pilot air-fuel mixture supply hole 9.The pilot flame is stabilized by designing so that (Al/A2)>1, that is, blowing out of the pilot flame and flashback are prevented. It is necessary to prevent this from happening.

Since the flow rate of the pilot mixture is approximately proportional to the square root of the differential pressure of fluid pressure loss between the mixing chamber 12 and the combustion chamber 1, in the embodiments shown in FIGS. 3 to 6, if the partition member 11 is provided with small holes, If the design is such that the air-fuel mixture injected from the mixing chamber 12 into the combustion chamber through this small hole is ignited to form a pilot flame, the flow velocity of the air-fuel mixture ejected from the above-mentioned small hole will be several m/s and stable. Unable to form a flame.

Further, the air-fuel ratio of the pilot air-fuel mixture is designed to be smaller than the air-fuel ratio of the main air-fuel mixture.

In the embodiments shown in FIGS. 3 to 6, appropriate pilot mixture can be achieved by appropriately designing the relative position between the pilot combustion cylinder body 8 and the atomizer 5 and the distance between the pilot mixture supply hole 9 and the partition member 11. It is possible to obtain the air-fuel ratio of

That is, the vaporized fuel sprayed from the sprayer 5 onto the partition member 11 flows along the surface of the partition member 11 and gradually mixes with air, so the closer it is to the sprayer 5 and the closer it is to the surface of the partition member 11, the more the air-fuel mixture becomes. This is because the air-fuel ratio is low.

The air-fuel ratio μ of the pilot mixture is normally designed to be about 0.9.

A typical operation of the liquid fuel combustion device having the structure as described above will be described below.

The partition member 11 is preheated to an appropriate temperature (for example, about 200° C.) by the above-mentioned electric heating means (not shown in the drawings).

This temperature is suitable for the liquid fuel sprayed from the sprayer 5 and colliding with the partition member 11 to be vaporized by heat exchange.

Next, combustion air is blown from the air supply hole 3 so that the air-fuel ratio μ becomes a predetermined value, for example, about 1.4, in accordance with the amount of liquid fuel supplied, and also from the electrode 7 and part of the pilot flame nozzle 10. A spark discharge is formed between the

Thereafter, when the liquid fuel is force-fed to the liquid fuel supply pipe 4, it is sprayed from the atomizer 5 toward the heated partition member 11 and vaporized.

The liquid fuel vaporized in this way is supplied from the air supply hole 3 and mixed with preheated combustion air in the mixing chamber 12, and is further heated to become a main mixture that flows toward the mixture outlet hole 15. go.

In the above process, a part of the mixture passes through the pilot mixture supply hole 9 of the pilot combustion tube main body 8 provided near the atomizer 5, and then first from the pilot flame port 10 into the combustion chamber 1.
The pilot mixture is ignited by a spark discharge to form a pilot flame.

Since the air-fuel ratio μ of this pilot air-fuel mixture is about 0.9 as described above, ignition by spark discharge is easy.

On the other hand, the main mixture that has reached the rectifier chamber 16 via the mixture outlet hole 15 is sufficiently mixed and has an air-fuel ratio μ of approximately 1.4, and is further preheated to a desired temperature (for example, about 150°C). The mixture reaches the combustion chamber 1 through the main flame port 14, is easily ignited by the pilot flame without causing explosive ignition, and starts continuous combustion.

FIG. 7 is a characteristic diagram showing the time change of the air-fuel ratio μ in the transient state at the time of ignition of the device shown in the embodiment explained in FIGS. 3 to 6, where the horizontal axis represents time t and the vertical axis represents the air-fuel ratio μ
represents.

In FIG. 7, t1 is the liquid fuel supply start time, t2 is the time when the air-fuel mixture reaches the combustion chamber 1 from the pilot air-fuel mixture supply hole 9, and t
3 is the time when the main mixture reaches combustion chamber 1, solid line A is the air-fuel ratio of the main mixture in combustion chamber 1, solid line B is the air-fuel ratio of the pilot mixture in the combustion chamber, and dotted line L is the flammable limit air-fuel ratio of the mixture. , the intersection point b between the dotted line L and the solid line B indicates the time t' when ignition is possible by spark discharge, and the intersection a between the dotted line L and the solid line A is the time t" when the main mixture can be ignited by the pilot flame.

In this way, the ignition of the liquid fuel combustion device according to the present invention is
First, a pilot flame is formed in the combustion chamber 1 by spark discharge, and then a main air-fuel mixture flows into the combustion chamber 1.

Since the main air-fuel mixture is ignited by the pilot flame as soon as it enters the flammable range, ignition is carried out extremely smoothly.

Further, when the air-fuel ratio of the pilot air-fuel mixture is 1.0 or less, for example 0.9, the ignition energy can be minimized, so the capacity of the high-pressure transformer for ignition can be reduced to make it more compact.

FIG. 8 shows the air-fuel ratio μ with the temperature of the main mixture as a parameter in the embodiment explained in FIGS. 3 to 6.
FIG. 2 is a characteristic diagram showing the relationship between ignition delay time and ignition delay time, where the horizontal axis represents the air-fuel ratio μ and the vertical axis represents the delay time.

As can be easily seen by comparing this Fig. 8 and the above-mentioned Fig. 2, according to this invention, the main mixture temperature is approximately 70°
There is no ignition delay even when the air-fuel ratio μ of the main air-fuel mixture changes from 1.0 to about 22, which is the flammable limit of liquid fuel, even when the air-fuel ratio μ changes significantly from ~150℃, and furthermore, compared to conventional combustion devices. It is also possible to provide a combustion device capable of reliable and safe ignition.

In the embodiment shown in FIGS. 3 to 6, an electrode conductor 7 constituting one electrode is provided on the central axis of the pilot combustion tube main body 8, and a pilot flame nozzle 10 of the pilot combustion tube main body 8 is provided with an electrode conductor 7. However, the structure of the spark discharge device used in this invention is not limited to the above-described embodiment, and any electrode structure can be used to perform spark discharge through the pilot mixture. Needless to say, similar effects can be obtained if possible.

Further, in the above-described embodiment, the pilot combustion cylinder main body 8 is provided near the atomizer 5, but for example, a stagnation part for vaporized fuel such as a depression is provided on the mixing chamber 12 side of the partition member 11, and a stagnation part for vaporized fuel is provided downstream of this stagnation part. A pilot air-fuel mixture with a desired air-fuel ratio can also be obtained by a design such as providing the pilot combustion cylinder main body 8.

Furthermore, it is possible to provide a plurality of pilot air-fuel mixture supply holes 9 in the pilot combustion cylinder main body 8, and to obtain a desired air-fuel ratio by changing the relative positions of the plurality of pilot air-fuel mixture supply holes 9 with respect to the mixing chamber 12. Not even.

However, even in this case, the cross-sectional area A of the pilot flame port 10
1, the total cross-sectional area of the pilot mixture supply hole 9 A2
It is necessary to keep it small.

In addition, in this invention, the shapes of the combustion tube 2, the mixing chamber 12, etc., the air supply hole 3, the atomizer 5, the pilot combustion tube main body part 8
It goes without saying that the arrangement etc. are not limited to those of the embodiments shown in FIGS. 3 to 6.

As explained above, this invention includes providing a pilot mixture supply hole 9 in a predetermined part of the mixing chamber 12 for guiding the mixture from a predetermined part of the mixing chamber 12 to the pilot burner port 10 before the main burner port. The air-fuel ratio at the pilot flame port 10 is set to a value suitable for ignition, and the cross-sectional area of the pilot mixture supply hole is appropriately set within a value smaller than the cross-sectional area of the pilot flame port 10. Since the pilot flame can be maintained stably and the pilot flame is formed by spark discharge, it has the effect of shortening the ignition delay time and ensuring safe ignition.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing the relationship between air-fuel mixture temperature and ignition delay when igniting by spark discharge, Fig. 2 is a characteristic diagram showing the relationship between air-fuel ratio and ignition delay when ignition is carried out by spark discharge, and Fig. 3 is a perspective view showing the main parts of a liquid fuel combustion device which is an embodiment of the present invention, FIG. 4 is a cross-sectional view taken along plane 3 shown in FIG. 3, and FIG. A sectional view showing the cut surface according to ■, Figure 6 is shown in Figure 4 with the symbol ■
FIG. 7 is a characteristic diagram showing the change in air-fuel ratio over time in an apparatus according to an embodiment of the present invention, and FIG. 8 is an enlarged sectional view of the portion indicated by . FIG. In the figure, 1 is a combustion chamber, 3 is an air supply hole, 4 is a liquid fuel supply pipe, 5 is a sprayer, 7 is a conductor for the electrode of the spark discharge device, 8 is a pilot combustion cylinder main body, and 9 is a pilot mixture supply element. L10 is a pilot burner, 12 is a mixing chamber, and 14 is a main burner. Note that the same reference numerals in each figure indicate the same parts.

Claims (1)

[Scope of Claims] 1. A fuel cell system that vaporizes and mixes combustion air and liquid fuel, having an atomizer that atomizes liquid fuel supplied from a liquid fuel supply pipe and an air supply hole that introduces combustion air using a blowing means. a mixing chamber for obtaining an air-fuel mixture; a combustion chamber having a main flame port to which the air-fuel mixture is supplied from the mixing chamber through a main air-fuel mixture outlet; and a combustion chamber provided in the combustion chamber for igniting the air-fuel mixture from the main flame port; a pilot flame port provided in the mixing chamber, a mixture bypass provided so as to be able to supply the mixture from the mixing chamber to the pilot flame port before the main flame port, and supplying the mixture from the mixing chamber to the mixture bypass. A liquid fuel combustion device comprising: a spark discharge device for igniting the air-fuel mixture from the pilot air-fuel mixture supplying the pilot air-fuel mixture and having a cross-sectional area smaller than the cross-sectional area of the pilot burner port. 2. Claim 1, characterized in that a partition member is provided between the mixing chamber and the combustion chamber so that a part of the heat generated in the combustion chamber heats the air-fuel mixture in the mixing chamber. liquid fuel combustion equipment. 3. The liquid fuel combustion apparatus according to claim 2, wherein the partition member provided between the mixing chamber and the combustion chamber is provided with electric heating means. 4. The air-fuel mixture bypass is formed by the cylinder space of the cylindrical pilot combustion cylinder main body, and one end of the pilot combustion cylinder main body opens into the combustion chamber to form the pipe tant flame port, and 2. The liquid fuel combustion apparatus according to claim 1, wherein the air supply hole is provided in a portion of the pilot combustion cylinder main body that is inside the mixing chamber. 5. The spark discharge device is characterized in that it has one electrode parallel to the axis of the cylinder in the cylinder internal space of the pilot combustion cylinder main body, and the other electrode made of a conductive member forming the cylinder of the pilot combustion cylinder main body. A liquid fuel combustion device according to claim 4. 6. The liquid fuel combustion device according to claim 1 or 4, wherein the air-fuel mixture bypass is provided with a plurality of pilot air-fuel mixture supply holes. 7. The pilot air-fuel mixture supply hole provided in the air-fuel mixture bypass is provided at a position where an air-fuel mixture having an air-fuel ratio lower than the air-fuel ratio of the air-fuel mixture led to the main burner port is introduced into the pilot burner port. A liquid fuel combustion device according to claim 1, 4, or 6.