JPH1089624A - Lean combustion burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lean combustion burner in which a good lean combustion having a wide combustion variable range (TDR) can be continued for a long period of time and a less amount of occurrence of NOx is found. SOLUTION: A lean combustion burner is formed by a porous member 7 for igniting lean mixture gas in it, a thermal insulating material 8 covering the outer circumference of the porous member 7 and forming a discharging hole 10 at its lower part, and a mixture gas flowing passage 11 arranged within the porous member 7 to cause its flowing sectional area A to be smaller than a combustion sectional area B of the porous member 7 and further having its extremity end positioned at least above the discharging hole 10. Lean mixture gas can be heated in sequence by combustion within the porous member 7, resulting in that a superior lean combustion can be attained, either a blowing-off or a back-fire of flame is positively prevented due to a difference in sectional areas so as to enable a wide TDR to be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lean burn bar which constitutes a heater for a fan heater or the like and a combustion section of a domestic water heater.
It is about na.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-180109, an unburned air-fuel mixture flows through a porous member to perform lean combustion on the other surface. Then, the exhaust gas is passed through the porous member again to recover heat, and the unburned air-fuel mixture is heated by the heat to obtain better combustion.

[0003]

In the prior art, however, high radiation conversion efficiency is achieved by performing surface combustion on the other surface of the porous member. Since the flow passage through which the air-fuel mixture flows has the same cross-sectional area, if the amount of combustion air is reduced in order to reduce the amount of combustion, the blown wind will also weaken, making combustion unstable and easily causing a flashback It is dangerous and cannot obtain a wide TDR (combustion variable range), and most of the combustion heat is released as radiant heat. The heat could not be heated.

[0004]

In order to solve the above-mentioned drawbacks, the present invention focuses on this point. In particular, the present invention comprises a porous member which burns a lean air-fuel mixture having an excessive amount of air, and a porous member. A heat insulating material that covers the outer periphery of the member and forms an exhaust hole at a lower portion, and is provided in the porous member, the flow cross-sectional area is smaller than the combustion cross-sectional area of the porous member, and the tip portion is at least above the exhaust hole And a mixed gas flow passage positioned.

[0005]

The fuel, which is a fuel, is sprayed into the vaporization pot 1 which constitutes the mixture supply means heated to a vaporizable temperature by the vaporization heater 2, and the combustion air which is at least twice the air-fuel ratio is supplied. Then, the mixture is premixed to form a lean mixture having an excessive amount of air.

[0006] The lean mixture is ejected into the porous member 7 from the mixture flow passage 11 communicating with the upper portion of the vaporization pot 1, and the outer periphery of the porous member 7 is covered with the heat insulating material 8. The air-fuel mixture circulates meandering toward the holes 10, during which time the lean mixture is well mixed by the random porous members 7, and the heat energy required for ignition is sufficiently obtained by heat conduction and radiant heat from the combustion site. The flame is retained in the straight pipe portion a in the porous member 7 in a random and fine mesh shape by the cooling by the unburned gas flow on the upstream side and the heat absorption to the porous member 7, and the stable lean combustion is performed. Is performed.

[0007] The combustion gas after the lean combustion is discharged to the exhaust hole 1.
The fuel gas flows out of the combustion tube 15 and rises inside the combustion tube 15 to be discharged to the outside of the apparatus to heat the room. Since this combustion gas is a lean burn and has an extremely low adiabatic flame temperature, the NOx value in the exhaust gas is low. Is a small household heater with a low effect of 1 to 20 ppm, which is the first realization of human-friendly heating by non-polluting combustion that has no effect on the environment.

In general, a lean air-fuel mixture having an excessive amount of air tends to lose heat energy and reactive groups required for sustaining combustion, and tends to become unstable. However, in the porous member 7, since the flow rate of the porous member 7 is suppressed to an appropriate level by an appropriate combustion cross-sectional area, it is possible to prevent the flame from being blown off at the time of burning with a large thermal power.

On the other hand, since the flow cross-sectional area of the mixed gas flow passage 11 is much smaller than the combustion cross-sectional area of the combustion portion in the porous member 7, the flow velocity in the mixed gas flow passage 11 is reduced due to the small thermal combustion, and the blowing amount is reduced. Even if it does, since it becomes faster than the inside of the porous member 7, there is no fear of flashback and it can be used with confidence.

[0010] Therefore, good combustion can be performed from large thermal combustion to small thermal combustion, and a wide TDR can be obtained despite lean combustion, which is optimal for household combustors.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment in which a lean burner according to the present invention is provided in a fan heater of a heater will be described. Reference numeral 1 denotes a vaporization pot made of aluminum die-cast in which a vaporization heater 2 is cast at an upper portion, and an ejection port 5 for blowing out combustion air from a combustion fan 3 through an air passage 4 communicates with one side thereof. The jet port 5 is provided with a nozzle 6 which communicates with an electromagnetic pump (not shown) and sprays fuel oil. The nozzle 6 forms a premixed gas of the vaporized gas and the combustion air, and constitutes a mixture supply device.

Reference numeral 7 denotes a cylindrical porous member provided so as to close the upper end opening of the vaporization pot 1, and is formed of a ceramic sintered body having a diameter of 90 φ, a height of 70 mm, and a porosity of 80%. The upper periphery is covered with a heat insulating material 8 made of an alumina-based heat-resistant material and a stainless steel material 9, and exhaust holes 10 for the combustion gas are formed all around the lower periphery.

Reference numeral 11 denotes a mixed gas flow passage which communicates the inside of the vaporization pot 1 with the porous member 7, and a heat insulating material 12 made of an alumina-based heat-resistant material while hollowing the lower portion inside the porous member 7 in an inverted concave shape.
A stainless steel cylinder 13 having a diameter of 20φ and a height of 50 mm is inserted to form a non-porous peripheral wall, and the upper end thereof is formed to protrude above the exhaust hole 10. It is supplied so as to form a meandering path in the porous member 7 and is burned lean in a straight pipe portion a in the porous member 7. The flow cross-sectional area A is about 314 mm ² and the inside of the porous member 7 is Combustion cross section B of the donut-shaped combustion part
A: B = 1: 16, which is much smaller than 000 mm ² .

The porous member 7, the heat insulating material 8 and the mixed gas flow path 11 constitute a lean burner 14 for satisfactorily burning a lean air-fuel mixture having an excessive amount of air. Since the adiabatic flame temperature of this type of fan heater is 1600 to 2200 ° C.
A flame at a temperature lower than 00 ° C. is obtained and the NOx value is 1 to 20
ppm.

Reference numeral 15 denotes a combustion cylinder which surrounds the lean burner 14 projecting above the partition plate 17 in the main body frame 16 and guides the generated combustion gas upward and discharges it from the upper end.

Numeral 18 denotes a convection fan provided on the rear side of the main body frame 16 behind the combustion cylinder 15, and the combustion gas discharged from the upper end of the combustion cylinder 15 is supplied to the hot air from an outlet 19 provided below the front surface of the main body frame 16 together with the room air. And the room is heated with hot air.

Reference numeral 20 denotes a heat shield plate which partitions a space between a partition frame 21 from the upper end of the combustion tube 15 to the outlet 19 into a hot air passage 22 through which the convection fan 18 blows air and a cooling passage 23 through which cooling air flows. is there.

Numeral 24 denotes a heating ring positioned so as to be opposed to the exhaust hole 10, which stands from the upper end of the vaporization pot 1, recovers heat from the combustion gas, and heats it back to the vaporization pot 1.

Reference numeral 25 denotes a packing material for sealing the lower portion of the combustion tube 15, reference numeral 26 denotes a fan cover of the convection fan 18, and reference numeral 27 denotes a burner cover of the vaporization pot 1.

Reference numeral 28 denotes an operation unit provided on the upper part of the main body frame 16, and 29 denotes a cartridge tank (not shown) for the main body frame 1.
A tank lid 30 for taking in and out of 6, a handle 30 and a lower plate 31 are provided.

Next, the operation of this embodiment will be described. When the vaporization heater 2 is energized and the vaporization pot 1 is heated to reach the vaporizable temperature, the combustion fan 3 starts to drive and the combustion air is supplied into the vaporization pot 1 and, after several tens of seconds, When the amount of air is stabilized, the fuel oil is sprayed from the nozzle 6 to become a vaporized gas, and a premixed air with the combustion air is formed.

However, the premixed gas at this time is at room temperature because the porous member 7 has not been heated yet and is at the ordinary theoretical air amount, and passes through the mixed gas flow passage 11 and the porous member 7 as it is. The gas is ignited by an appropriate igniting means (not shown) through the exhaust hole 10 to perform ordinary flame combustion.

The porous member 7 is gradually heated by the flame combustion, and after 1-2 minutes, the temperature of the porous member 7 becomes 10
When the temperature reaches 00 ° C. or higher, this is detected by a temperature sensor, a timer count from operation, ignition, or the like, and the amount of combustion air is increased to twice or more the normal air-fuel ratio.

As a result, a lean air-fuel mixture is formed in the vaporization pot 1, and is injected into the porous member 7 heated to a high temperature through the air-fuel mixture flow passage 11, thereby promoting the mixing of the lean air-fuel mixture. In addition, the temperature is rapidly increased and the lean combustion is favorably performed in the straight pipe portion a in the porous member 7.

Therefore, the combustion gas after the combustion is discharged to the exhaust hole 1
0, and is discharged from above the combustion tube 15 to the convection fan 18.
The air is blown as warm air from the outlet 19 to heat the room. However, since the heating is performed by lean combustion, the NOx value is 1 to 20 ppm, which is the normal NOx of this type of fan heater. The value is extremely low with respect to the value of 110 to 120 ppm, and it is possible to realize a heater with little effect on the environment and people and almost no pollution.

On the other hand, the mixed gas flow passage 11 and the porous member 7 having a porosity of 80% have different flow velocities, and the air ratio is 2.0, and the air temperature is 0 ° C. and the mixed gas flow is 2500 kcal / h at the maximum combustion amount. The exhaust hole 10 is 0.3 m / s (1.5 m / s when the expansion of combustion is included) for the passage 11 = 5 m / s, and the flow velocity of the porous member 7 is 3 to 5 times that of the mixed gas flow passage 11. Therefore, even if the amount of air blown by the large thermal combustion increases, good combustion is continued without blowing off the flame.

The cross-sectional area A of the mixed gas flow passage 11 and the cross-sectional area B of combustion in the porous member 7 are 1:16, so that the cross-sectional area A is much smaller. Therefore, the flow velocity of the mixture flow passage 11 is always high even if the blowing amount is reduced by the small thermal combustion, so that it is difficult for the flashback to occur. However, the area ratio of A: B is limited to 1: 4.5, and if it exceeds this, the balance of the flow velocity in the mixed gas flow passage 11 is lost and flashback occurs.

Therefore, good combustion is performed from a large thermal power to a small thermal power, and TDR =
A wide combustion range of 1: 5 or more can be obtained, and it is extremely easy to use.

Further, the outer periphery of the porous member 7 is almost completely covered with the heat insulating material 8.
, The combustion noise inside is not emitted to the outside and quiet combustion is realized.
Projecting above the exhaust hole 10 and having a non-porous peripheral wall, a meandering path of the air-fuel mixture toward the exhaust hole 10 is formed in the porous member 7.

By making the straight pipe portion a downstream of the meandering path as long as possible, a slight vertical movement of the combustion part (flame position) can be allowed. This is to permit an increase / decrease in the amount of combustion air (increase / decrease in air ratio), and it is possible to prevent a margin at the time of control of the amount of combustion and a danger due to a change in performance of the combustion fan 3 and other peripheral devices. Things.

Further, since the heating ring 24 is provided opposite to the exhaust hole 10, the heating ring 24 is reliably heated by the combustion gas, and a large amount of heat back to the vaporization pot 1 can be smoothly performed. The power supply of the vaporization heater 2 is almost stopped to save power.

Further, since the air-fuel mixture passage 11 is formed as a double layer of the heat shield 12 and the stainless steel cylinder 13, it is possible to prevent the air-fuel mixture passing through the air-fuel mixture passage 11 from being ignited by combustion heat. is there.

Although this embodiment has been described based on the application to a heater such as a fan heater using fuel oil as a fuel, the invention is not limited to this. For example, the combustion gas from the lean burner 14 may be used. By heating the heat exchanger in which a heat medium such as water flows inside, a household water heater may be used, and the fuel of the present invention can be sufficiently obtained not only with fuel oil but also with gas and the like. You can do it.

[0034]

In summary, the present invention relates to a porous member for burning a lean air-fuel mixture having an excessive amount of air therein, a heat insulating material covering an outer periphery of the porous member and forming an exhaust hole at a lower portion, and the porous member. Provided, the flow cross-sectional area is smaller than the combustion cross-sectional area of the porous member, and the mixed gas flow passage whose tip is located at least above the exhaust hole. Lean combustion is performed reliably,
Good combustion with little generation of NOx can be obtained, and a combustor that is friendly to the environment and people can be provided.

Further, since it is possible to reliably prevent the blow-out of the flame of the large thermal combustion and the flashback of the small thermal combustion, it is possible to obtain a wide TDR even with the lean combustion, and the use range is widened and the usability is extremely good. .

[Brief description of the drawings]

FIG. 1 is a perspective view of a heater equipped with a catalytic combustion device according to one embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is a sectional view of the main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vaporization pot 2 Vaporization heater 7 Porous member 8 Insulation material 10 Exhaust hole 11 Mixed gas flow path 14 Lean combustion burner 24 Heating ring A Flow cross-section B Burning cross-section

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsumi Moruga 7-7 Higashi Shinbo, Sanjo City, Niigata Prefecture (72) Inventor Kazuhiro Takeda 7-7 Higashi Shinbo, Sanjo City, Niigata Prefecture Corona Co., Ltd. (72) Inventor Masaki Takachi 7-7 Higashi Shinbo, Sanjo City, Niigata Prefecture

Claims (5)

[Claims] 1. A porous member that burns a lean mixture with an excess amount of air therein, a heat insulating material that covers an outer periphery of the porous member and forms an exhaust hole at a lower portion, and is provided in the porous member. A lean burn burner having a flow cross-sectional area smaller than a combustion cross-sectional area of the porous member, and comprising a mixed gas flow passage having a tip portion located at least above the exhaust hole. 2. The porous member is provided on a vaporization pot which includes a vaporization heater and forms a premixed gas of vaporized gas and combustion air inside, and communicates the interior of the vaporization pot with a mixed gas flow passage. 2. The burner according to claim 1, wherein a heating ring for heat recovery is opposed to the exhaust hole. 3. The burner according to claim 1, wherein the porous member is formed of a ceramic sintered body. 4. The burner according to claim 1, wherein the heat insulating material is made of an alumina-based heat-resistant material. 5. The burner according to claim 1, wherein the mixture flow passage has a non-porous peripheral wall.