JP2001065816A - Combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a pilot flame (a flame produced by primary combustion) formed at the downstream side of a catalytic combustion portion from being blown down or becoming unstable caused by supplied secondary air, in the case where the secondary air is supplied to the downstream side of the catalytic combustion portion. SOLUTION: A catalytic combustion portion 4 by itself forms a recessed portion 20 of substantially conical shape at the downstream side of the catalytic combustion portion 4. A deflection flow guide 9a is disposed at a secondary air diffusing port 9 to cause a swirling flow from the secondary air diffusing port 9 to and inside a combustion chamber 6 to further cause a reverse flow at the center of the combustion chamber 6. The reverse flow stabilizes a holding flame space in the recessed portion 20, thereby stabilizing a starting flame formed in the recessed portion 20. Accordingly, the starting flame in the recessed portion 20 is prevented from being blown off or becoming unstable caused by secondary air, despite the increase of the secondary air supplied to the downstream side of the catalytic combustion portion 4 or lowering of the temperature of the secondary air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus equipped with an energizing heating element that generates heat when energized.

[0002]

BACKGROUND OF THE INVENTION The present applicant has filed an application for a combustion apparatus equipped with an electric heating element (Japanese Patent Application No. 11-80594, this technique is not a well-known technique). The combustion device disclosed in this application specification supplies a premixed air upstream of an energized heating element that generates heat when energized, and also supplies combustion air to a downstream side of the energized heating element. The current-carrying heating element had a substantially cylindrical and disk shape having a honeycomb shape.

[0003]

SUMMARY OF THE INVENTION An electric heating element is substantially cylindrical,
In the case of a disk-shaped one, the surface of the downstream end of the energizing heating element becomes flat. For this reason, 2 supplied to the downstream of the energization heating element
The flame (primary combustion flame of fuel and primary air) formed on the downstream side of the current-carrying heating element is blown off or cooled by the airflow of the secondary air, so that the blowout easily occurs. This is because the flame formed downstream of the energized heating element tends to be blown out or become unstable due to an increase in the amount of secondary air supplied due to an increase in the amount of combustion. Become.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the extinguishing of a flame formed downstream of an energizing heating element without using a special flame holding means. In providing the equipment.

[0005]

[Means for Solving the Problems] [Claim 1] By providing a concave portion on the downstream side of a current-carrying heating element and generating a flow of fluid toward the concave portion, a flame in the concave portion (primary combustion). Flame) stabilizes. In other words, the secondary air flow directly supplied to the downstream side of the energizing heating element prevents the pilot flame formed downstream of the energizing heating element from being blown out or becoming unstable. The problem that the flame in the concave portion is cooled and blown out by the air directly supplied to the downstream side of the body or becomes unstable is avoided.
This is because even if the amount of combustion increases and the amount of secondary air supplied directly to the downstream side of the heating element increases, the secondary air stabilizes the inside of the concave portion and the seed flame by the primary combustion holds the flame. Is done. Thus, the flame formed downstream of the energized heating element is always stabilized, an increase in emission is prevented, and clean combustion is always possible. In addition, since the flame holding of the pilot flame is performed by the recess of the energizing heating element itself, it is not necessary to use a special flame holding means for flame holding, and a combustion device having a flame holding function can be provided at low cost.

[0006] The concave portion can be easily formed on the downstream side of the current-carrying heating element by shifting the honeycomb layer.

[Means of Claim 3] By the high-temperature heating section provided on the downstream side of the energizing heating element, the downstream side of the energizing heating element can be ignited.

According to a fourth aspect of the present invention, a swirl flow is generated in the combustion chamber by the swirl flow generating means, so that a reverse flow toward the heating element is generated in the center of the combustion chamber, and the reverse flow of the combustion flows toward the recess. A flame stabilizing combustion stream is produced. In addition, the swirling flow generated in the combustion chamber improves the mixing property between the unburned gas containing the fuel from the primary combustion and the secondary air, thereby increasing the combustion efficiency. In addition, a part of the exhaust gas is returned to the side of the current-carrying heating element and mixed with the unburned gas due to the backflow toward the current-carrying heating element, so that rapid combustion is suppressed and exhaust emission can be reduced. Further, since the secondary combustion is swirled, the combustion length required for the secondary combustion can be reduced, and the size of the combustion device can be reduced.

[Means of claim 5] The secondary air blown toward the recess by the pushing flow generating means generates a flame holding airflow toward the recess.

The electric heating element which generates heat when energized receives a catalyst on its surface.
When energized, the action of the catalyst can be enhanced, and the action of the catalyst in the initial stage of starting the engine can be enhanced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described using two embodiments and modifications. First Embodiment FIGS. 1 to 3 show a first embodiment. First, a catalytic combustion device will be described with reference to FIG. In addition,
The upper side in the embodiment indicates the upper side in FIG. 1, and the lower side indicates the lower side in FIG.

The catalytic combustion device shown in this embodiment employs a double-pipe structure.
And an outer cylinder 2 that covers the lower outer side of the outer cylinder. Note that the inner cylinder 1 is a cylinder that internally mixes fuel and air and burns fuel, and the outer cylinder 2 is a cylinder that forms an air passage 3 with the inner cylinder 1.

The inner cylinder 1 is a substantially bottomed cylindrical body made of a heat-resistant metal (such as stainless steel), and a catalytic combustion section 4 (corresponding to an electric heating element) is mounted at an intermediate portion thereof. The lower side (fuel supply side) of the catalytic combustion section 4 is a premixing cylinder 1a forming a premixing chamber 5 for mixing fuel and air, and the upper side (combustion gas discharge side) of the catalytic combustion section 4 is catalytic combustion. A combustion cylinder 1b that forms a combustion chamber 6 that burns fuel that has passed through the section 4.

In the lower central portion of the premix cylinder 1a, the vaporized fuel supplied from the carburetor 7 and the air (primary air) flowing through the air passage 3 are supplied to the premix chamber 5 in the premix cylinder 1a. A gas mixture introduction hole 8 for guiding is formed. A secondary air outlet 9 for allowing air (secondary air) supplied through the air passage 3 to flow into the combustion chamber 6 in the combustion cylinder 1b is provided in the combustion cylinder 1b on the side closer to the catalytic combustion section 4. A plurality is formed. The secondary air outlet 9 will be described later.

The amount of air supplied to the premixing chamber 5 from the air / fuel mixture introducing hole 8 is larger than the amount of fuel supplied to the premixing chamber 5 by the air-fuel ratio (the stoichiometric air-fuel ratio). The amount of air supplied from the secondary air outlet 9 to the combustion chamber 6 is adjusted to be a low air-fuel ratio (low air-fuel ratio). (Fuel ratio).

A liquid fuel (for example, light oil or the like) sent from a fuel tank 10 by a fuel pump 11 (corresponding to a fuel supply means) is supplied to the outer cylinder 2 facing the air-fuel mixture introducing hole 8.
A vaporizer 7 for vaporizing and supplying the mixture to the mixture introduction hole 8 is mounted. An air passage 3 is provided at the lower end of the outer cylinder 2.
An air pump 12 (corresponding to air supply means) for supplying air to the inside is connected.

The catalytic combustion section 4 includes a catalyst (a noble metal such as Pt, Pd, Rn, Ni, C, etc.) for accelerating a partial oxidation reaction on a surface of a substantially honeycomb-shaped current-carrying heating element having a large number of through holes 4a.
u or a metal such as alumina or zirconia). Note that a partial oxidation reaction is possible even when an oxide layer such as alumina for forming an insulating layer is used as it is.

On the downstream side of the catalytic combustion section 4, there is formed a substantially conical recess 20 which is recessed toward the center. The specific structure of the catalytic combustion unit 4 is as shown in FIGS.
For example, a flat plate 13 (for example, having a thickness of 50 μm) that generates heat by a current-carrying resistance made of a Fe—Cr—Al ferrite stainless steel
A thin insulating layer made of alumina or the like provided on the surface of a honeycomb layer 15 composed of a corrugated sheet 14 (for example, 50 μm thick) and carrying a catalyst such as Pt or Pd for promoting ignition combustion and partial oxidation reaction on the surface. And the plurality of honeycomb layers 15
Is welded to the center electrode 16 and spirally wound to form a substantially conical shape. Alternatively, after a plurality of honeycomb layers 15 are wound in a substantially disc shape around the center electrode 16, the center electrode 16 is slid in the upstream axial direction relative to the outer electrode 19 to form a conical shape. is there. As a result, in the catalytic combustion section 4, a creation surface 15a formed for each winding layer of the honeycomb layer 15 is formed, and a flame holding space is formed inside the recess 20. In addition, since the honeycomb layers 15 are stacked while being shifted from each other, it is not necessary to use a special flame holding means for flame holding, and the honeycomb structure can be provided at low cost.

The center electrode 16 at the center of the catalytic combustion section 4 is connected to a power supply terminal 18 guided to the outside of the inner cylinder 1 and the outer cylinder 2 via an insulating bush 17. Is grounded to the inner cylinder 1 via the outer electrode 19, and when a voltage is applied to the center electrode 16 via the outer electrode 19, the catalytic combustion unit 4 is energized and generates heat.

As shown in FIG. 3, a high-temperature heating section 21 is partially provided on the downstream side of the honeycomb layer 15 constituting the catalytic combustion section 4. The high-temperature heating section 21 quickly reaches a temperature (for example, 700 to 800 ° C.) or more suitable for ignition by energization. The high-temperature heating section 21 is formed by slitting a flat plate 13 constituting the honeycomb layer 15 by punching.
Are formed. By providing the slit portion 23 in the flat plate 13 in this manner, the current flowing through the flat plate 13 flows intensively to the high-temperature heating portion 21, and the high-temperature heating portion 21 is formed by the axial length L 1 of the high-temperature heating portion 21. 21 are set. In addition, the high-temperature heating part 2
Reference numeral 1 denotes an appropriate number and set at an appropriate interval in the winding direction of the flat plate 13. For example, the high-temperature heating portions 21 are arranged at equal intervals for each honeycomb layer 15 and provided so as to be capable of multipoint ignition. It is. In addition, the high-temperature heating section 21 is also arranged at the corner of the step of each winding layer of the honeycomb layer 15. The high-temperature heat-generating portion 21 at the corner has no member in contact with the inside, and the temperature quickly rises. Therefore, the time required for the high-temperature heat generating portion 21 at the corner to rise to a temperature suitable for ignition is reduced, and
The temperature rises to a level suitable for ignition with less power.

Here, a secondary air outlet 9 for supplying secondary air to the downstream side of the catalytic combustion section 4 has a flame holding head toward the recess 20 by the secondary air flow for combustion supplied to the combustion chamber 6. Means for pushing a flame holding fluid for generating a combustion flow for use. The flame-holding fluid pushing means in this embodiment is a deflected flow guide 9 a attached inside the secondary air outlet 9, and serves to supply the secondary air supplied from the secondary air outlet 9 into the combustion chamber 6. The swirling flow is generated in the combustion chamber 6 in the tangential direction.

When a swirling flow is generated in the combustion chamber 6,
A backflow toward the catalytic combustion section 4 is generated in a central portion in the combustion chamber 6, and the combustion flow due to the backflow generates a combustion flow for flame holding toward the recess 20. In addition, the swirling flow generated in the combustion chamber 6 causes the unburned gas containing fuel from the primary combustion and
The mixing property with the secondary air is improved, and the combustion efficiency can be increased. On the other hand, a part of the exhaust gas is returned to the catalytic combustion unit 4 side and mixed with the unburned gas by the backflow toward the catalytic combustion unit 4, so that rapid combustion is suppressed and the exhaust emission can be reduced. Furthermore, since the secondary combustion turns, the combustion cylinder 1
b can be shortened and the size of the combustion device can be reduced.

The operation of this embodiment will be described. When an operation switch (not shown) is turned on, electric power is supplied to the power supply terminal 18 by a control device (not shown), and electricity is supplied through the path of the center electrode 16 → the catalytic combustion section 4 → the outer electrode 19 → the inner cylinder 1. When a voltage is applied to the center electrode 16, the catalytic combustion unit 4
Generates heat to raise the temperature to partially oxidize the fuel, and the high-temperature heat generating sections 21 provided on the downstream side of the catalytic combustion section 4 generate heat prior to the ignition temperature or higher.

When the time when the high-temperature heat generating portion 21 generates heat above the ignition temperature is reached, the control device energizes the fuel pump 11 and the air pump 12 to start supplying fuel and combustion air. Here, the fuel pump 11 and the air pump 12
May be provided to operate at a low speed suitable for ignition and to increase the speed after ignition.

The liquid fuel is sent from the fuel tank 10 to the carburetor 7 by the fuel pump 11. The vaporizer 7 has, for example, a built-in electrothermal evaporator, and the fuel vaporized by the vaporizer 7 is sent to the premixing chamber 5 through the mixture inlet hole 8. The combustion air is supplied into the air passage 3 by the air pump 12, sent to the premixing chamber 5 from the mixture introduction hole 8, and supplied to the combustion chamber 6 from the secondary air outlet 9. The ratio of the amount of air sent from the mixture air inlet 8 to the premixing chamber 5 and the amount of air supplied from the secondary air outlet 9 into the combustion chamber 6 is set, for example, to 1: 2. And
The amount of air supplied into the inner cylinder 1 from the mixture air inlet 8 and the secondary air outlet 9 is such that the air-fuel ratio of the fuel supplied to the premixing chamber 5 is 17.5 to 29.2 (1.2 ≦ Excess air ratio ≤
2).

The ratio of fuel and primary air supplied to the premixing chamber 5 is determined by the air-fuel ratio being the stoichiometric air-fuel ratio (the weight ratio of air to fuel is 1).
4.6) The following fuel excess (excess air ratio ≦ 1), and this mixture flows into the catalytic combustion section 4 after being mixed in the premixing chamber 5. Since the catalytic combustion unit 4 receives heat and generates heat at or above the catalytic reaction start temperature, the fuel in the air-fuel mixture passing through the catalytic combustion unit 4 undergoes a catalytic reaction at a relatively low temperature (300 ° C. or higher), resulting in gasification. Denatures to fuel (CO, H2, light component fuel, etc.). The gasified fuel is supplied to the secondary air outlet 9
To form a flammable air-fuel mixture. At this time, the plurality of high-temperature heating portions 21 arranged at the corners of the spirally arranged honeycomb layer 15 quickly generate heat above the ignition temperature, so that the gasified fuel contained in the combustible air-fuel mixture has a high temperature. The multi-point ignition occurs by touching the heat generating portion 21, the flame is immediately diffused and the combustion is started, and the fuel is completely burned in the downstream combustion chamber 6. At the time of steady combustion, since the combustion heat in the combustion chamber 6 is received by the catalytic combustion unit 4, even if the energization of the catalytic combustion unit 4 is stopped, the catalytic combustion unit 4 is maintained at the catalyst activation temperature or higher, and the self-sustained stable combustion is performed. To continue.

Here, the air-fuel mixture passing through the catalytic combustion section 4 generates gasified fuel by the catalytic reaction as described above, and touches the high-temperature heating section 21 to ignite. The flame (fire type) of the primary combustion shifts to a flame holding state in the flame holding space in the recess 20. Due to the shift to steady operation, the amount of combustion increases,
When the amount of air supplied from the secondary air outlet 9 into the combustion chamber 6 increases, a high-speed swirling flow is formed in the combustion chamber 6 by the action of the deflected flow guide 9a. As a result, a backflow toward the catalytic combustion section 4 is generated in the central portion of the combustion chamber 6, and a combustion flow for flame holding toward the recess 20 is generated by the combustion flow due to the backflow.

As a result, the amount of the secondary air supplied from the secondary air outlet 9 increases, and even if the flow rate of the secondary air flow is higher than the combustion speed and the secondary air is at a low temperature, the flame holding is performed. The fire in the space does not directly interfere with the secondary air, but mixes with the circulating flow of relatively slow combustion gas formed in the center of the swirling flow. Since this circulation flow increases almost in proportion to the combustion amount (fuel supply amount), the fire within the flame holding space maintains a stabilized state. Further, as a synergistic effect, heat is stored in the flame holding space by the stabilized radiant heat of the flame holding, and the pilot flame in the flame holding space is further stabilized.

The high-temperature combustion gas which has been completely burned in the combustion chamber 6 heats a heat medium such as engine cooling water via a heat exchanger (not shown) and is discharged to the outside as exhaust gas. On the other hand, the high-temperature heat medium liquid heated by the combustion gas is sent to a heater core of an indoor air conditioner by a water pump (not shown). Then, the air passing through the heater core is heated and blown into the room, thereby heating the vehicle interior.

[Effects of the Embodiment] In this embodiment, a recess 20 is provided on the downstream side of the catalytic combustion section 4 and the recess 2
The flow of the fluid toward zero stabilizes the flame in the recess 20 (flame due to primary combustion). Thereby, by the flow of the secondary air directly supplied to the downstream side of the catalytic combustion unit 4,
The problem that the pilot flame formed on the downstream side of the catalytic combustion unit 4 is blown out or becomes unstable is avoided, and the air directly supplied to the downstream side of the catalytic combustion unit 4 reduces the recess 20.
The problem that the flame inside is cooled and blown out or becomes unstable is avoided. This is because even when the amount of combustion increases and the amount of secondary air supplied directly to the downstream side of the catalytic combustion section 4 increases, the secondary air stabilizes the inside of the concave portion 20 and the pilot flame due to the primary combustion generates Flame is kept. Thus, the flame formed downstream of the catalytic combustion section 4 is always stable, the emission of the catalytic combustion device is prevented from increasing, and clean combustion is always possible. Further, since the flame holding of the pilot flame is performed by the concave portion 20 of the heating element itself, there is no need to use a special flame holding means for flame holding, and a combustion device having a flame holding function can be provided at low cost.

Further, as described above, the catalytic combustion section 4
In this case, since low-temperature combustion is performed due to insufficient air supply, overheating of the catalyst is prevented, and stable catalytic combustion can be performed over a long period of time. Further, since the catalytic combustion unit 4 requires only one stage and adopts a simple configuration in which the unburned fuel activated in the catalytic combustion unit 4 is completely burned, the size of the catalytic combustion device can be reduced. , And cost reduction becomes possible.

[Second Embodiment] FIG. 4 is a perspective view showing the honeycomb layer 15 before winding. In the second embodiment, the high-temperature heating sections 24 and 25 are provided on both the upstream side and the downstream side of the catalytic combustion section 4.
Is provided. The high-temperature heating section 24 on the upstream side quickly reaches the activation temperature of the catalyst (for example, 300 ° C. or more) prior to the other parts in the initial stage of energization, and the high-temperature heating section 25 provided on the downstream side In the initial stage of the energization start, the ignition temperature (for example, 700 to 800 ° C. or higher) is quickly reached prior to other portions.

The high-temperature heating sections 24 and 25 are formed by forming punched holes 26 in the flat plate 13 constituting the honeycomb layer 15. By providing the punched holes 26 in the flat plate 13 in this way, the current flowing through the flat plate 13
The temperature of the upstream high-temperature heating section 24 is set by the axial length L2, and the temperature of the downstream high-temperature heating section 25 is set by the axial length L3.

With this arrangement, the mixture passing through the high-temperature heating section 24 on the upstream side rapidly causes a catalytic reaction at the initial stage of energization. As a result, the entire catalyst in the catalytic combustion section 4 is warmed by the heat of the catalytic reaction, so that the gasification reaction and heat generation of the air-fuel mixture passing through the catalytic combustion section 4 proceed at an accelerated rate, enabling instant ignition even with low power. Become. Further, by shortening the ignition time, the time to reach full combustion can be shortened, and clean combustion can be realized in a short time.

[Modification] In the above embodiment, an example is shown in which the center of the catalytic combustion section 4 is protruded upstream in a substantially conical shape, and a substantially conical recess 20 is formed downstream of the catalytic combustion section 4. However, a stepped recess 20 such as one step or plural steps may be formed on the downstream side of the catalytic combustion section 4. In the above-described embodiment, an example in which the swirling flow is generated in the combustion chamber 6 to form the flow of the fluid toward the recess 20 has been described. For example, the secondary air blown out from the secondary air outlet 9 is
It is also possible to provide a flame-holding fluid pushing means for directing the fluid toward the recess 20 by a secondary air flow blown out from the secondary air outlet 9.

In the above embodiment, an example was shown in which the liquid fuel was vaporized using the vaporizer 7 and then catalytically burned.
It may be provided to supply gas fuel or the like to the premixing chamber 5 or to supply fuel atomized by the fuel injection device into the premixing chamber 5. In the above-described embodiment, an example in which the catalytic combustion device is used for a heating device of an automobile has been described, but the present invention may be applied to other combustion devices such as a home heating device, a hot water supply device, a dryer, and an industrial burner. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a catalytic combustion device (first embodiment).

FIG. 2 is a sectional view showing a catalytic combustion section (first embodiment).

FIG. 3 is a perspective view showing a honeycomb layer before winding (first embodiment)
Embodiment).

FIG. 4 is a perspective view showing a honeycomb layer before winding (second embodiment).
Embodiment).

[Explanation of symbols]

4 Catalytic Combustion Section (Electrified Heating Element) 4a Through Hole 5 Premixing Chamber 6 Combustion Chamber 9 Secondary Air Blow Out Port 9a Deflected Flow Guide (Flame Holding Fluid Pushing Means, Swirling Flow Generating Means) 11 Fuel Pump (Fuel Supply Means) Reference Signs List 12 air pump (air supply means) 13 flat plate 14 corrugated plate (other member) 15 honeycomb layer 20 concave portion 21 high-temperature heating section 25 high-temperature heating section

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23D 14/74 F23D 14/74 H (72) Inventor Akira Ito 1-1-1 Showacho, Kariya-shi, Aichi Stock F term in company Denso (reference) 3K017 AA02 AB01 AB05 AB07 AC02 AD10 AF01 AG07 BA02 BB01 BB04 BB07 BC10 BD02 BE10 BE11 BG01 3K065 QB01 QB11 TA15 TB08 TD04 TE05 TG01 TK02 TK04 TK06 TP08

Claims (6)

[Claims] An electric heating element having a honeycomb shape having a large number of through holes through which a fluid flows and generating heat when energized, a fuel supply means for supplying fuel to a premixing chamber upstream of the electric heating element, Air supply means for supplying air to a combustion chamber downstream of the premixing chamber and the energized heating element, wherein a recess is provided by the energized heating element downstream of the energized heating element. And a flame stabilizing fluid push for generating a flame stabilizing air flow or a combustion flow toward the recess by the combustion secondary air flow supplied to the combustion chamber downstream of the energizing heating element by the air supply means. A combustion device comprising means. 2. The combustion device according to claim 1, wherein the energizing heating element is provided by stacking a honeycomb layer formed by combining a flat plate and a corrugated plate, and the honeycomb layers are staggered and stacked to form the energizing heating element. A combustion device characterized in that a recess is provided on the downstream side of the body. 3. The combustion apparatus according to claim 1, further comprising a high-temperature heat-generating portion that is locally heated to a high temperature downstream of the current-carrying heating element. 4. The combustion apparatus according to claim 1, wherein said flame-holding fluid pushing means is provided at an outlet for supplying secondary air for combustion into said combustion chamber by said air supply means. A combustion device provided, which is a swirl flow generating means for generating a swirl flow in the combustion chamber. 5. The combustion apparatus according to claim 1, wherein said flame-holding fluid pushing means is connected to an outlet for supplying secondary air for combustion into said combustion chamber by said air supply means. A combustion device provided as a push-flow generating means for blowing secondary air toward the recess. 6. The combustion apparatus according to claim 1, wherein the energizing heating element is provided with a catalyst supported on a surface thereof.