JPH0627565B2 - Thin film flame type combustion equipment using perforated plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion device for performing stratified combustion of a premixed fuel gas and combustion air in a thin film form.

[Prior Art] In Japanese Patent Application No. 63-38396, the applicant of the present invention has a flat plate-like shape which blocks a jet flow at a predetermined distance from a jet port of a burner which jets a premixed gas of fuel gas and air. Proposed a gas combustion device using a thin-film flame burner that arranges a shut-off plate and heads toward the shut-off plate in the laminar flow area of the jet flow and stratifies the premixture flowing along the shut-off plate into a thin-film flame. is doing.

This gas combustion device had the following features.

(A) By using the shield plate as a heated object, it can be easily applied to cooking, and by using the shield plate as a radiant heat source, it can be used for heating and heating.

(B) Since the combustion flame can be made thin and flat over a large area, the object to be heated can be heated uniformly.

(C) Since stable combustion can be performed even in a region where the excess air ratio is large, the combustion temperature is low and the generation of nitrogen oxides (NOx) due to heat is small.

(D) Since a flat and thin premixed flame can be formed in a large area close to the object to be heated, the thermal efficiency is high.

However, in this thin-film flame burner, the formation of the thin-film flame and the flow velocity of the premixed gas are maintained within a delicate balance range. Therefore, when the jet flow of the premixed gas has a non-uniform flow velocity in the thin film flame formation region, the thin film flame fluctuates and is not stable, resulting in deterioration of combustibility and deterioration of combustion efficiency.

In order to solve this problem, this patent payer
2-96054 proposes a structure in which a straightening plate having a mesh shape or a honeycomb shape is provided at the ejection port of a nozzle for ejecting a premixed gas.

Further, in the thin film flame burner, the amount of heat generation is determined by the size of the area of the main thin film flame, and the size of the thin film flame that can be obtained stably corresponds to the area of the nozzle ejection port of the burner. That is, the range in which the calorific value (combustion amount) can be increased or decreased is
The area is limited to a narrow range corresponding to the area of the nozzle ejection port. However, since it is difficult to form the area of the nozzle ejection port variably, the thin-film flame burner is not suitable for a combustion device that requires a wide range of increase / decrease in calorific value.

In order to solve this drawback, the applicant of the patent
No. 2-96053 proposes a thin-film flame-type gas combustion apparatus equipped with a burner having coaxially arranged multiple-structure nozzles.

[Problems to be Solved by the Invention] In any of the gas combustion devices using the above thin-film flame burner, a stable laminar flow is obtained at the premixed gas outlet,
A nozzle whose cross-sectional area gradually decreases toward the jet outlet is used. Therefore, there are the following drawbacks.

a) If the diameter of the nozzle outlet is too large, the jet flow will be disturbed and a uniform laminar flow will not be obtained. Therefore, a thin film flame having a very large area cannot be obtained, and a burner with a large heat generation amount is difficult to be formed.

b) The size of the nozzle itself increases in the axial direction, and the height of the gas combustion equipment increases.

c) Even when a nozzle with a straightening vane is used, there is a straightening effect before and after the ejection port, but the range in which the amount of heat generation can be increased or decreased does not expand.

d) The adoption of the multiple structure nozzle can expand the range in which the heat generation amount can be increased or decreased to some extent, but the expansion effect cannot be said to be sufficient and the structure is complicated.

An object of the present invention is to provide a combustion device capable of forming a thin-film all-premixed combustion flame excellent in flame stability in an extremely wide range of change in calorific value.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a jet flow at a position separated from a jet port of a burner for jetting a premixed gas of fuel gas and combustion air by a predetermined distance. In a thin-film flame-type combustion device that arranges a shut-off plate that shuts off and stratifies the premixed gas into a thin-film flame in the stagnation flow region of the jet flow, a large number of small holes are opened in a predetermined arrangement in the thickness direction. A porous plate is arranged at the jet outlet, and when the input is low, surface combustion is performed on the surface of the porous plate with the small holes of the porous plate as a flame port, and when the input is high, the small holes of the porous plate are provided. A structure was adopted in which the premixed gas was ejected more uniformly and stratified combustion was performed.

[Operation and Effect of the Invention] The thin-film flame combustion device of the present invention uniformly ejects a premixed gas of fuel gas and combustion air having a stoichiometric ratio or higher from each small hole of the perforated plate. The jet flow becomes a parallel flow near the perforated plate and progresses toward the blocking plate and is blocked by the blocking plate.

As a result, a premixed airflow is obtained in which the flow velocity in the vertical direction is gradually reduced between the surface of the perforated plate and the blocking plate and the flow is diverted along the blocking plate. When this premixed airflow is ignited, a thin-film fuel flame can be formed along the blocking plate on the surface where the flow velocity and the flame propagation velocity are in equilibrium.

The thin film flame is not generated by the balance due to the collision of the counter flows, but is formed by the cutoff of the premixed airflow by the stationary cutoff plate. Therefore, it is extremely stable and has a stable combustion range that is large even with respect to fluctuations in the ejection speed and fluctuations in the excess air ratio.

In addition, the thin-film flame burner has a pre-mixture that blows out from a large number of small holes dispersed in the perforated plate at a substantially uniform speed, so that the area between the block plate and the perforated plate is approximately the same. Therefore, it is possible to form a stable thin film flame up to an area having a diameter twice as large as that of the perforated plate (a large calorific value is obtained).

When the flow rate of the premixed gas is reduced, the thin film flame asymptotically approaches the surface of the perforated plate and eventually adheres to the surface of the perforated plate, and when the supply of preheating aerated gas is further reduced, many small flames adhered to each small hole. Become a group.

During this time, the displacement of the thin film flame, the increase and decrease of the area, and the transition to the small flame group are made stable and reversible.

As a result, the calorific value can be increased / decreased in a wider range as compared with the conventional thin-film flame burner using a nozzle.

Further, since the burner can be flattened, the height of the combustion equipment can be reduced as compared with the combustion equipment using the conventional thin film flame burner using the nozzle or the Bunsen burner.

[Embodiment] Next, the present invention will be described based on an embodiment shown in FIGS.

FIG. 1 shows a thin film flame type gas combustion apparatus (gas stove in this embodiment) according to the present invention, and 100 is a case thereof, in which a round hole 102 is provided in the center of a top plate 101, and the round hole 102 An annular juice tray 110 is fitted in the outer peripheral portion. The soup tray 110 is composed of a bottom plate portion 111, an outer peripheral cylinder portion 112, a brim-shaped eave portion 113 extending from the upper end thereof, and an inner peripheral cylinder portion 114 extending from the inner periphery of the bottom plate portion. In addition, a cylindrical upper partition wall 120 for partitioning the burner installation chamber and the inside of another case is erected below the soup tray 110, and the round hole 102 is provided in a case bottom plate 104 having a ventilation hole 103.
It is fixed coaxially with.

Reference numeral 1 denotes an all-premixed combustion (all primary air) burner using a perforated plate, which is vertically installed in the case 100 coaxially with the round hole 102. The burner 1 is formed by covering the upper surface of a cylindrical metal burner body 11 having a bottom and an open upper surface with a porous plate 2. Reference numeral 3 denotes a premixed gas supply device, which supplies the burner 1 with a premixed gas of fuel gas and combustion air. Reference numeral 4 denotes a circular glass blocking plate arranged above the burner 1 in parallel with the porous plate 2 (perpendicular to the axis of the burner), and its lower surface serves as a blocking surface 4A. A thin film flame burner is constituted by the burner, the blocking plate 4 and the premixed gas supply device 3.

The porous plate 2 has 3.0 to 6 circular small holes 22 with a diameter of 1.0 to 2.5 mm on the entire surface of the ceramic plate 21 mainly composed of cordierite and having excellent thermal shock resistance except the outer peripheral edge portion. .0
It is formed in a grid pattern with mm intervals.

In this embodiment, the upper end of the burner body 11 is widened to form the flange portion 12, and the tip of the flange portion 12 is extended in the axial direction to provide the large diameter cylindrical portion 13. The large-diameter cylindrical portion 13 has a heat-resistant metal ring 1 whose upper end is bent outward.
4 is externally fitted, and the perforated plate 2 has the flange-shaped portion 1
2 and is fitted into the large-diameter cylindrical portion 13.

The large-diameter cylindrical portion 13 has a ring-shaped flame holding plate portion 51 that is substantially flush with the upper surface of the porous plate and extends to the outer circumference of the upper surface, an upward edge portion 52 extended to the outer circumference, and the flame holding plate. Part 5
A flame holding plate 5 that extends to the inner periphery of the heat-resistant metal plate 1 and is composed of a pressing plate portion 53 that presses the upper surface of the outer peripheral edge portion of the porous plate 2 is attached to the heat resistant metal ring 14 by welding. The upper surface of the outer peripheral edge of the porous plate 2 is edged so that the upper surface of the flame holding plate 5 and the upper surface of the porous plate 2 are flat and continuous without any step. A narrow gap 5B is provided between the outer periphery of the flame holding plate 5 and the inner peripheral cylindrical portion 114 of the juice receiving tray 110.

The premixed gas supply device 3 has an upstream connected to a blower port of a blower and a downstream connected to a supply port of a fuel gas supply pipe 32 in a mixing pipe 31 connected to the burner body 11. The inside of the burner body 11 is a premixed air chamber.

The blocking plate 4 is composed of a circular heat-resistant glass plate 41 having a thickness of 3 to 12 mm and a diameter of 120 to 200 mm, a metal ring 42 wound around the outer periphery thereof, and legs 43 fixed to the metal ring 42 at three positions. Become. The blocking plate 4 is fixed by inserting the lower end of the leg 43 into a hole formed in the bottom plate portion 111 of the juice tray 110 so that the distance between the blocking surface 4A and the upper surface 2A of the perforated plate becomes a set value. Has been formed.

Next, the operation of the thin film flame type gas combustion equipment according to this embodiment will be described.

The fuel gas is mixed with the air forcibly supplied from the blower so that the air is somewhat in excess of the stoichiometric air-fuel ratio, and the mixing pipe 3
Mix at 1 and supply to premix chamber. At the same time, when an ignition device provided near the burner is operated, the premixed gas ejected from the small holes of the perforated plate is ignited.

[When heat generation amount is large] The small jets from the small holes 22 are faster than the flame propagation speed, and the small jets spread in the horizontal direction to widen the cross-sectional area of the basin and contact each other, and are almost parallel to each other. It becomes a large jet with a large area. The flow velocity of this large jet in the direction of the blocking surface gradually decreases,
It becomes zero at the blocking surface 4A. The large jet is deflected by the blocking plate 4, spreads radially along the blocking plate 4, and the flow velocity gradually decreases.

When ignited in this state, the flame propagation speed S of the premixed air,
A thin-film combustion flame is formed on the surface that is in balance with the flow velocity V of the large jet. In the thin film flame F, when the jet velocity of the small jet increases (the combustion amount increases), or the air-fuel ratio of the premixed air becomes lean (excessive combustion air), the flame propagation velocity S decreases. , F1 is displaced to the side of the blocking plate 4 and the area is increased, and in the opposite case, the area is displaced to the side of the porous plate 2 as F2 and the area is reduced. That is, as long as the flow velocity V of the large jet is V> S (flame propagation velocity), the flow velocity V of the large jet is between the porous plate 2 and the blocking surface 4A.
= S (flame propagation speed) always exists, so misfiring due to blowout is unlikely to occur.

As described above, in this combustion apparatus, even if the formation position and size of the thin film flame F are slightly changed in response to changes in the combustion amount, changes in the excess air ratio, or changes in the oxygen concentration in the air, combustion It is extremely stable itself.

Further, although the flame holding plate 5 is not an essential constituent element in the present invention, when the flame holding plate 5 is used, the outer peripheral edge of the thin film flame adheres to the surface 5A of the flame holding plate 5 as shown. This can improve the stability and combustibility of the thin film flame. That is,
In the case where the flame holding plate 5 is not provided, the thin film flame F has a premixed gas that diffuses into the outside at the outer peripheral edge of the thin film flame F and has a non-combustible air-fuel ratio that is leaner in fuel than the combustible air-fuel ratio, causing the outer peripheral edge to sway, or to a slight amount. The fuel gas is discharged unburned. The flame holding plate 5 eliminates such inconvenience.

In this embodiment, the flame holding plate 5 is cooled through the ventilation hole 103, the burner grounding chamber A, and the narrow gap 5B between the outer periphery of the flame holding plate 5 and the inner peripheral cylindrical portion 114 of the juice tray 110. An airflow (arrow K) is generated.

[When the calorific value is small] As shown in FIG. 2, a small flame f that adheres to each small hole and burns
The surface of the perforated plate 2 becomes red like the all-primary air infrared burner using a normal ceramic plate (perforated plate) having a large number of small holes.

The transition from this burner to a thin film flame burner is the combustion amount,
That is, it is performed reversibly and stably with a change in the supply amount of the premixed gas. As a result, the perforated plate 2 has a diameter of 65.
mm, the calorific value is 400 kcal / h to 400 kc
It can be changed up to al / h. The ratio of this maximum calorific value to the minimum calorific value (generally called the Derntown ratio) is
The value is sufficient to use this burner as a cooking heat source such as a stove, a heating heat source such as a stove, or a heating source such as a water heater.

Further, the thin-film flame F is stable in combustion even in a state where the air is sufficiently in excess of the stoichiometric air-fuel ratio. Therefore, combustion with an excessive amount of combustion air is possible and a large amount of heat is dissipated by radiation. Little oxide is generated.

Furthermore, since the thin film flame F capable of dissipating a large amount of heat due to radiation can be formed in a wide area in the vicinity of the blocking plate, when the blocking plate 4 is an object to be heated, high heating efficiency can be obtained.

The thin film flame F has a clear thin film shape when the jet flow is laminar, but the shape is slightly unclear in the transition region from laminar flow to turbulent flow, and becomes a thick layer with vortex in the turbulent flow region. Spread. Therefore, the combustion equipment using the thin film flame F of the present invention,
It has a sufficient effect only in the laminar region of premixed air.

The present invention includes the following modes in addition to the above embodiments.

A) The blocking plate 4 may be a porous body having some air permeability, such as a porous ceramic plate.

B) The blocking plate 4 may be arranged to be slightly inclined with respect to the axis, and may be a curved surface having a large radius of curvature or an obtuse conical surface.

C) The perforated plate 2 may be a regular polygon such as a square, or may be made of a heat-resistant metal.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a thin film flame type gas combustion device according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the combustion part thereof.
FIG. 3 is an overall perspective view showing the assembly of the burner portion, and FIG.
The figure is an overall perspective view. In the figure, 1 ... Thin film flame burner, 2 ... Perforated plate, 3 ...
Premixed air supply device, 4 ... shut-off plate, 4A ... shut-off surface,
5 ... Flame holding plate, F, F1, F2 ... Thin film flame, 22 ...
Pupa

Front page continuation (72) Inventor Yoshihiro Ishikawa 2-26, Fukuzumi-cho, Nakagawa-ku, Nagoya, Aichi Prefecture Rinnai Co., Ltd. (72) Inventor Junichi Kimura 507, Shintakamachi, Tokai-shi, Aichi Toho Gas Co., Ltd. Inside the Technical Research Institute (72) Inventor Shunichi Oshida 507 Shinhomachi, Tokai City, Aichi Prefecture 2 Toho Gas Co., Ltd.Comprehensive Technical Research Institute (72) Inventor Chihomi 507 Shinhomachi, Tokai City, Aichi Prefecture Toho Gas Co., Ltd. Corporate Research Laboratory (56) References Japanese Patent Laid-Open No. 1-310214 (JP, A) Actual Development Sho 53-56139 (JP, U)

Claims (1)

[Claims] 1. A position separated from a jet port of a burner for jetting a premixed mixture of fuel gas and combustion air by a predetermined distance,
In a thin-film flame combustion device that arranges a shut-off plate to shut off the jet flow and stratifies the premixture into a thin-film flame in the stagnation flow region of the jet flow, a large number of small holes were opened in the plate thickness direction in a predetermined arrangement. A thick perforated plate is installed at the jet outlet, and when the input is low, the small holes of the perforated plate are used as flame openings for surface combustion on the surface of the perforated plate, and when the input is high, the perforated plate is A thin-film flame-type combustion device that uniformly ejects premixed air from the small holes in the tank to perform stratified combustion.