GB2120771A - Surface combustion type burner - Google Patents
Surface combustion type burner Download PDFInfo
- Publication number
- GB2120771A GB2120771A GB08214296A GB8214296A GB2120771A GB 2120771 A GB2120771 A GB 2120771A GB 08214296 A GB08214296 A GB 08214296A GB 8214296 A GB8214296 A GB 8214296A GB 2120771 A GB2120771 A GB 2120771A
- Authority
- GB
- United Kingdom
- Prior art keywords
- burner
- netting
- perforated metal
- metal base
- metallic netting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/12—Radiant burners
- F23D14/14—Radiant burners using screens or perforated plates
- F23D14/145—Radiant burners using screens or perforated plates combustion being stabilised at a screen or a perforated plate
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/10—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium
- F24H1/12—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium in which the water is kept separate from the heating medium
- F24H1/14—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium in which the water is kept separate from the heating medium by tubes, e.g. bent in serpentine form
- F24H1/145—Continuous-flow heaters, i.e. heaters in which heat is generated only while the water is flowing, e.g. with direct contact of the water with the heating medium in which the water is kept separate from the heating medium by tubes, e.g. bent in serpentine form using fluid fuel
Abstract
A surface combustion type burner having an air supply which comprises entirely primary air has metallic netting (1) defining a combustion surface (2). Upstream of, supporting and contacting the metallic netting, over substantially the entire upstream surface of the metallic netting, is a punched or perforated metal base (5) which has an open or void perforation ratio smaller than that of the metallic netting. <IMAGE>
Description
SPECIFICATION
Surface combustion type burner
This invention relates to an improved surface combustion type burner having a single-stage air supply which is entirely primary air, equipped with metallic netting defining the combustion surface. The invention is more particularly directed to such burners suitable for high combustion loads.
Conventional burners of the surface combustion type utilise various different ways of providing the combustion surface. Such combustion surfaces may be a formed ceramic product, metallic netting and so forth, each having respective advantages and disadvantages. It is apparent, however, that those utilizing metallic netting are, in practice, more favorable than those utilizing the formed ceramic product, in view of lower material cost and better productivity owing to easy forming operation. Included in such conventional burners utilizing metallic netting, there indeed are different structures, for example structures which use the netting in a single layer, or in two or more overlapping layers, but they have all been used in burners for rather low combustion loads.The reason for such restriction in use of such a type of burner is that the higher the combustion load the more marked becomes the problems associated with higher noxious NOx content in the exhaust, and the higher the tendency for backfiring owing to excessive burner heating. The more excess primary air which is supplied with the intention of thereby solving such problems, the higher becomes the tendency of the flame to lift, thus resulting in a higher noxious CO exhaust content. Consequently, such burners have conventionally been restricted to use in low combustion load ranges with a restricted supply of air.
This invention has as its object to provide a surface combustion type burner substantially without the drawbacks of the conventional structures as mentioned hereinabove, and which is particularly suited for high combustion loads, thus substantially eliminating the drawbacks while affecting as little as possible the advantages of the surface combustion type burners using metallic netting for the combustion surface.
To attain the object, the surface combustion type burner, having a single-stage air supply which constitutes entirely primary air, equipped with metallic netting having front and rear surfaces, with the front surface defining the combustion surface, is characterised in that, in close supporting contact behind the metallic netting, substantially all over the entire rear surface thereof, there is disposed a punched or perforated metal base which has an open or void perforation ratio smaller than that of the said metallic netting.
Since the perforated metal base having the void perforation ratio smaller than that of the metallic netting is disposed in close supporting contact behind the netting, a suitable combustible gas/air mixture pressure in a mixture chamber behind the perforated metal base can thereby be sustained. This enables the combustible gas/air mixture to widely spread out within the mixture chamber and ultimately to supply the gas generally uniformly all over the combustion surface composed of the metal netting. Also advantageous is the fact that the perforated metal base of rather small void perforation ratio causes the mixture to flow at quite a high speed through each perforation thereof, which will effectively prevent the backfire phonomenon.The generally uniformly supplied combustible gas/air mixture then undergoes abrupt flow speed retardation and laterally spreading dispersion, while passing through the metallic netting, therefore causing a stable flame, even on the solid non-perforated area of the perforated metal base, with a small amount of combustion per unit area and therefore small flame height, to thus substantially retain the advantageous feature generally of surface combustion type burners, namely that of providing generally uniform heating all over the combustion area.Furthermore, since the combustible gas/air mixture undergoes sufficient laterally spreading dispersion and provides the flame, all over the burner area, the flame being small in height as mentioned above, which provides sufficient flame-sustaining effect for the high-speed jet of the combustible gas/air mixture immediately it comes out of each of the perforations of the perforated metal base; lift of the flame is unlikely to occur, even when the burner is used under high combustion loads with an excessive mixing ratio of primary air with the intention of thereby reducing the noxious NOx content of the exhaust, which results in addition in the reduction of another noxious exhaust content, namely the CO content, as effectively as possible.Still further, since the perforated metal base possesses excellent thermal conductivity and has a larger heat capacity than that of the metal netting, any possible tendency for temporary and localized abnormal heating of the metal netting is effectively suppressed, since such thermal un-uniformity in the metal netting is rapidly conducted to the perforated metal base where it is rapidly made uniformly constant, thus to positively prevent the phenomenon of backfire owing to such hotspots or localized abnormal high temperature, and therefore to guarantee relatively stable combustion.While this burner provides, as above, substantially ideal combustion which is almost optimal as a surface combustion type burner, all over the practical range from low to high combustion loads; it is quite simple in structure with the addition only of the perforated metal base to a conventional burner using the metal netting, and high productivity can therefore be realized in its manufacture, without detracting from the advantage of such conventional burners which use only the metal netting, namely the low material cost and ease of manufacture.
In this respect, it may be suspected that the favorable result as above is achieved simply by the perforated metal base without any substantial synergistic effect of the metal netting and the perforated metal base as used in combination. However, various experiments carried out by the inventors have attested that the burner embodying this invention is indeed far more favorable than a burner which has no metal netting and has the combustion surface provided directly by the perforated metal base, with respect to backfire and CO content of the exhaust. This clearly shows that the said result is actually realized by the synergistic effect of the metal netting and the perforated metal base Detailed results of such experiments are shown later in this specification.
In order that the invention may be more readily understood, various embodiments of the surface combustion type burner according to this invention will now be described with reference to the accompanying drawings, wherein:
Figure 1 is a schematic longitudinal sectional view of one embodiment of the burner;
Figure 2 is an enlarged view of a portion of the burner shown in Fig. 1;
Figure 3 is a graphical representation of test results showing the practical permissible upper limit of excess mixing ratio of primary air for a range of combustion loads, with respect to a burner embodying this invention and a burner without metal netting;;
Figure 4 is a graphical representation of test results showing the practical permissible maximum combustion loads, with respect to a burner embodying this invention having the perforated metal base of the respectively selected various void perforation ratios;
Figure 5 is a partial sectional view, similar to the lefthand end portion of Fig. 1, but showing a modified embodiment;
Figure 6 is a sectional view, similar in general to Fig. 1, but showing another modified embodiment; and
Figures 7 and 8 are similar sectional views of respective further embodiments, both adapted for incorporation in instantaneous water heating assemblies.
Referring first to the embodiment of the surface combustion type burner of this invention shown in Figs. 1 and 2, designated at 1 is a tubular metallic netting having a front, downstream or outer surface and a rear, upstream or inner surface, with the front surface defining the combustion surface 2. One longitudinal end of the tubular metallic netting 1 is closed up by an imperforate tubular cap 3, while the other end is connected to, and is in open communication with, a burner body structural portion 4 serving as a supply duct for a gaseous fuel as well as the air. In close supporting contact behind the metallic netting 1, substantially all over the entire rear or inner surface thereof, there is disposed a punched or perforated metal base 5, correspondingly tubular in shape, which has an open or void perforation ratio smaller than that of the said metallic netting 1.The longitudinal ends of the metal base 5 are securely fixed, respectively, to the cap 3 and the burner body structural portion 4, both ends being fitted in appropriate mating parts. Designated at 6 is a pipe securely fixed to the burner body structural portion 4 for supplying therethrough fuel gas into the space within the burner body structure portion 4. A zero-ballance type pressure regulator 7 is incorporated in this pipe 6, and at a tip end of the pipe 6 there is provided a fuel nozzle 8. To the burner body structural portion 4 there is securely fixed a fan 9, in free communication with the space within the portion 4 so as to forcibly supply the burner primary air thereinto.A regulatoractuating pressure-conducting tube 10 is provided in communication with the space within the burner body structural portion 4 in a position downstream of the fan 9, for applying the pressure to the zero-ballance type pressure regulator 7. The regulator 7 is thus operable to automatically regulate the fuel supply in response to the pressure, so that the amount of fuel is always varied substantially in the required or good proportion to the burner primary air regardless of any possible variation by manoeuvering, i.e. speed variations, of the fan 9.
Thus, when the fan 9 is arbitrarily operated to supply the burner primary air into the space or chamber within the burner body structural portion 4, then the amount of fuel gas supplied is always substantially in proper proportion to the amount of such air as actually supplied, and the resultant gas/air mixture is caused to spout through the metallic netting 1, and thereupon to burn at the combustion surface 2. While this occurs, since the perforated metal base 5 of rather small void perforation ratio is provided in supporting contact behind or beneath the metallic netting 1, the gas/air mixture is properly held within the tubular metal base 5 under an appropriately sustained pressure and is accordingly spread out or dispersed therein, effectively, widely enough to thus be ultimately supplied generally uniformly all over the area of the netting.
Such gas/air mixture undergoes, while passing through the metallic netting 1, abrupt retardation in its speed of flow and laterally spreading dispersion along the netting 1.
Therefore a stable flame results, even on the solid non-perforated area of the perforated metal base 5, and a small amount of combustion per unit area and therefore small flame height results, to thus provide generally uniform heating all over the combustion surface area. Furthermore, since such a widely spread flame having a small height provides sufficient flame-sustaining effect for the high-speed jet of the gas/air mixture immediately upon coming out of each of the perforations of the perforated metal base 5; lift of the flame is unlikely to occur, even when the burner is used under high combustion loads with such excessive mixing ratio of primary air with the intention of thereby abating the noxious exhaust NOx content, as would inevitably cause considerable lift of the flame in the case of conventional burners, thus also resulting in the reduction of another noxious exhaust CO content as effectively as possible.Still further, since the perforated metal base 5 possesses excellent thermal conductivity and has a larger heat capacity than that of the metallic netting 1, any possible tendency for temporary or localized abnormal heating of the metallic netting 1 is effectively suppressed, since such irregular heat is rapidly conducted to the perforated metal base 5 and is there rapidly rendered uniformly constant, thus positively preventing the phenomenon of backfire owing to such spotwise or localized abnormal high temperature.
In attestation of the merit of the burners embodying this invention, the results will now be given of experiments done by the inventors, referring to Fig. 3. In this Figure, upper limiting lines, as actually prescribed by the occurrence of substantial lift of the flame, for keeping up the exhaust content condition of CO/CO2'0.01 when natural gas was used as the fuel, are shown as the curves in accordance with the given co-ordinates which indicate the combustion load on a given abscissa and excessive air ratio, with respect to the stoicheometric air volume, on a given ordinate. Thus the region immediately above the curves is the region off the said condition, with the value of CO/CO2 therefore being slightly over 0.01 in that region.Curve A represents the results obtained with the burner embodying this invention equipped with the perforated metal base 5 in close supporting contact behind the metallic netting 1.
Curve B is an equivalent curve obtained with a reference burner equipped only with the perforated metal base 5, without combined use of any metallic netting 1. From these results of the experiments, it is apparent that, of the two burners, the one embodying this invention gives a lower CO content in the exhaust when supplied with excess air with the intention of thereby abating NOx exhaust content, the difference becoming more pronounced as the combustion load increases. It is thus demonstrated that this favorable function achieved by synergistic effect of the metallic netting 1 and the perforated metal base 5 as used in combination and is thus the peculiar merit of this invention.
It will be understood that the shape of the combustion surface 2 may arbitrarily be selected from various possibilities, and it may for instance be cylindrical, prismatic or planar.
Further modifications in the structure are also possible, and for instance, either one or both of the perforated metal base 5 and the metallic netting 1 may be formed as multiple overlapping layers. In either case, it should be noted that if and when a gap occurs between the metallic netting 1 and the perforated metal base 5 as they are heated, owing to the larger thermal expansion of the other netting 1 relative to that of the inner base 5, then harmful flaming combustion may occur in such a gap. It is therefore highly desirable, for preventing the latter, to provide the metallic netting 1 and the perforated metal base 5 in such manner as to always retain their mutual close contact, even when they are heated to quite high temperature range.More particularly, it is therefore preferable to construct the perforated metal base 5 from a material having a larger coefficient of thermal expansion than that of the metal of the netting 1, and to construct both the metallic netting 1 and the perforated metal base 5 in cylindrical or tubular shape. By way of example, a typical and practical combination of the specific materials, in terminology as prescribed in JIS, namely
Japanese Industrial Standard, is ferro-chrome heat-resisting steel of FCH2 or the like for the netting 1, and nickel-chrome heat-resisting steel of SUS304 or the like for the mating perforated metal base 5.
The inventors also made various further experiments to investigate how the CO and NOx contents of the exhaust are affected by the shapes of the metallic netting 1 and the perforated metal base 5. Revealed from the results as favorable were those using the metallic netting 1 made of wires of 0.25-0.5 mm diameter in 20-40 mesh, most preferably of 0.3-0.4 mm diameter in 25-35 mesh, and the perforated metal base 5 with 1-2 mm diameter perforations of 3-20% void perforation ratio, most preferably with a ratio of 5-1 5%. The optimal range of the excess mixing ratio of primary air in the gas/air mixture was then revealed as 1.2-1.7 for natural gas and 1.6-2.1 for manufactured gas.Shown in Fig. 4 are the results of a partial series among such experiments, made under the conditon of an excess primary air mixing ratio of 1.5, using a natural gas as the fuel and the metallic netting 1 of 0.35 mm diameter wires in 32 mesh as well as the perforated metal base 5 with 1.0-2.0 mm diameter perforations, in a graphical representation with the combustion load on the ordinate and with the void perforation ratio of the perforated metal base 5 on the abscissa. The curve C is an upper limiting line, as actually prescribed by occurrence of substantial lift of the flame, for the exhaust content condition of
CO/CO2 = 0.01, and curve D is another entirely different limiting line for 10 mm flame length. It is apparent from the results shown here that the void perforation ratio of the perforated metal base 5 should preferably be not less than 5%.In addition thereto, it is further revealed from another partial series among the experiments, that the said ratio should preferably be not over 1556 to achieve proper operation without the occurrence of the phenomenon of backfire. All in all, it is thus found that a ratio in the range of 5-15% provides the most preferable results.
The surface combustion type burner embodying this invention may be applicable in many fields. For instance it may be used in instantaneous water heating assemblies, warm air blowers, and various boilers, such as boilers for baths and the like. However there is no limitation whatsoever in the field of application.
There will now be described the modified embodiments shown in Figs. 5-8, wherein the parts identical to those in Figs. 1 and 2 are designated by the same reference numerals. The description of such parts need not be repeated.
The embodiment shown in Fig. 5 differs from that of Fig. 1 only in that both ends of the metallic netting 1 are not fitted on outer rims of the cap 3 and the burner body structural portion 4, respectively, as shown in Fig. 1.
Instead, they are securely fixed in longitudinal end-to-end abutment against the cap 3 and the burner body structural portion 4, respectively. This modification is based on the fact, when the ends of the metallic netting 1 are fitted over the outer rims as in Fig. 1, there is a tendency for the gas/air mixture at such fitted ends to flow out along the overall facial surface of the netting 1 and form thereat long flames which may lead to increased CO exhaust content. A flame which is generally uniform over all the combustion surface 2 may be expected by fixing the netting 1 in longitudinal end-to-end abutment against the cap 3 and portion 4, thus enabling the CO exhaust content to be further effectively reduced.
Another embodiment is shown in Fig. 6, wherein, in a power source circuit for the fan 9, there is provided a manoeuvering or speed control mechanism 1 2 for adjustably setting the fan 9 rotational speed of the fan 9, thereby to make it possible to arbitrarily adjust or regulate the output heating rate of this burner and to reasonably save the power for driving the fan 9. In the burner body structural portion 4 downstream of the fan 9 there are disposed an orifice 1 3 and a plate 14 with multiple perforations, and longitudinally intermediately therebetween there is disposed the fuel nozzle 8.Thus, the burner air as supplied from the fan 9 and the fuel from the nozzle 8 may be mixed sufficiently enough by the cooperative function of the orifice 1 3 and the perforated plate 14, to then be supplied towards the combustion surface 2. The regulator-actuating pressure-conducting tube 10 is, in this embodiment, provided in communication with the space within the burner body structural portion 4 between the orifice 1 3 and the fan 9. Thus, the mixing ratio of the fuel gas and the burner primary air may always be retained within a set range, regardless of any inadvertent plugging of the metallic netting 1, perforated metal base 5 and perforated plate 14 as well as any alteration of the speed of the fan 9.Preferably, the range corresponding to that mentioned hereinabove is employed, which is optimal for abating CO and NOx exhaust contents, namely an excess primary air mixing ratio range of 1.2-1.7 for natural gas, and 1.6-2.1 for manufactured gas.
It is thus possible with the burner of Fig. 6, thanks to the flow-path restricting function of the orifice 1 3 and the regulating function of the zero-balance type pressure regulator 7, to positively retain in a set range the mixing ratio of the fuel and air as supplied towards the combustion surface 2, without regard to any inadvertent plugging of the metallic netting 1 defining the combustion surface 2 and of other parts may occur and without regard to alterations which may be caused in the amount of the burner air as supplied by the fan 9, therefore providing with certainty the optimal surface combustion, for long periods of time, without causing any substantial lift of the flame, backfire or incomplete combustion.
Furthermore, the orifice 1 3 causes substantial turbulance in the gas/air mixture flow, thereby to produce thorough mixing, this contributing to further enhance and guarantee stable combustion. Still further, the manoeuvering or speed control mechanism 1 2 provides quite convenient means for easily changing the rotational speed of the fan 9 at any time to thereby adjust the heating output of the burner positively and exactly as desired, by means of a reasonably simple structure, and provides economy in operation by virtue of the saving in power required to drive the fan 9.
Still another embodiment is shown in Fig.
7, which has a burner body structure portion 4' constructed as a double-wall unit having an open-top box-like shape, and the fan 9 is connected to the space within the double-wall, in free communication therewith. The opentop interior space provided by the box-like portion 4' serves as a combustion chamber 1 5. The metallic netting 1 and the perforated metal base 5 are securely bolted to the burner body structural portion 4', thus to fixedly lie in the combustion chamber 1 5. Designated at 1 6 is an orifice for the air flow, and provided
in association therewith is a sleeve 1 7 which
receives the fuel nozzle 8.This sleeve 1 7 is
securely bolted to the burner body structural
portion 4' via the intermediary of a lid 18, in such a manner that the tip or inner end of the sleeve 1 7 is located close to the orifice 1 6.
The orifice 1 6 itself is securely fixed to an
open-ended flow distributor tube 1 9 made of
a perforated solid material or a permeable
porous material having a cylindrical shape.
This flow distributor tube 1 9 is in turn securely supported so as to lie within the metallic netting 1 and the perforated metal base 5 substantially coaxially therewith, with its outer peripheral surface 20 spaced a suitable distance apart therefrom. Thus, some portion of the combustible gas/air mixture which is supplied to one end of this flow distributor tube 1 9 flows permeatingly through the perforations or pores to the outer peripheral surface 20, radially outwardly of the tube 19, while the remaining portion of the gas/air mixture flows directly to the other end of the tube 19, longitudinally thereof, and may then flow radially outwardly and flow back in a reverse longitudinal direction, as illustrated by arrows, to any portion of the outer peripheral surface 20.Additionally, a finned water pipe 21 is disposed immediately above the combustion chamber 1 5 so that cold water supplied from the water pipe inlet side 21 a may be heated, therein, the hot water being taken out from the water pipe outlet side 21 b.
It is thus possible with the burner of Fig.
7, thanks to the function of the flow distributor tube 19, to introduce the gas/air mixture to the outer peripheral surface 20 of the flow distributor tube 1 9 through the two different paths. The gas/air mixture will pass radially outwardly through the wall perforations or pores in the tube 19, and will also flow longitudinally, reversing its direction of longitudinal flow where it flows radially outwardly around at the tip or end of the tube 1 9. This makes the gas/air mixture supply to the outer peripheral portion 20 uniform enough and therefore ultimately provides quite uniform a temperature all over the combustion surface 2. It also effectively restrains any serious burning damage of the combustion-surfacebuilding material owing to spotwise or localized heating to abnormal high temperatures thereof.Furthermore, what is needed to make up this embodiment of burner is no more than a relatively simple modification, namely the incorporation of a tube of perforated solid material or permeable porous material, and this burner is therefore advantageous in view also of the material and manufacturing costs.
Still further, constructing the burner body structural portion 4' as a box-like shape, with the interior space serving as the combustion chamber 15, has the advantage also of effectively utilizing the heat in the combustion chamber 1 5 to preheat the burner primary air
as supplied from the fan 9 through the burner
body structural portion 4'. Furthermore, there
is a possibility of further enhancing the unifor
mity of the gas supply, apart from the use of the flow distributor tube 1 9 of simple uniform void perforation ratio or of permeable porosity over its entire surface, by particularly modify
ing the spacial distribution of such void perforation ratio or permeable porosity. This may
be achieved, for instance, by making the ratio or porosity smaller at progressive points, i.e.
points progressively further from the gas inlet, in due accordance with the flow condition of the combustible gas/air mixture.
Yet another embodiment is shown in Fig. 8, wherein use of the flow distributor tube 1 9 of
Fig. 7, having the gas-permeable wall, is replaced by an open-end flow distributor tube
19' made of normal solid material, thus having the gas-impermeable wall, disposed as clearly seen from Fig. 8. However, as is selfevident to those skilled in the art, the burner of Fig. 8 could possibly use the flow distributor tube 1 9 of gas-permeable material. As an important feature, this embodiment has a flame-sustainer metallic netting 22, wrapped in the form of a ring of about 20 mm width along radially outwardly of, and around, the combustion-surface 2- defining tubular netting 1 near an end portion thereof which is connected to and supported by the burner body structural portion 4.The netting 22 is coarser than the netting 1, and more particularly is preferably 15-20 mesh and made of 0.35 mm diameter wires. A casing 23 is provided to define the combustion chamber 1 5 therein, with a burnt gas exhaust discharge outlet 24 formed in a bottom portion of the casing 23.
Designated at 25 and 26 are finned water pipes disposed in the lower portion of the combustion chamber 1 5. More particularly, an outlet end water pipe portion 25 is disposed upstream of an inlet end water pipe portion 26, with respect to the flow of the burnt gas. An intermediate water pipe portion 27 interconnects the inlet and outlet end portions 25 and 26, being helically wrapped around the wall of the casing 23 in close contact thereto at the portion thereof corresponding to the effective combustion chamber 1 5. In this way, this whole assembly forms an instantaneous water heating assembly for heating up water supplied from the water pipe inlet side 26a, the hot water being taken out from the water pipe outlet side 25b.Designated further at 28 is an ignition plug, and at 29 a flame detector, to provide for easy ignition of the combustible gas/air mixture and for immediate automatic cut-off of the fuel supply in response to flame failure, respectively.
Provision of the flame-sustaining metallic netting 22 as illustrated in the burner of Fig.
8 further contributes to the effective preven tion of the lift of the flame, even with quite an excessive supply of air. This enables by the use of such an excessive air supply, ultimately the effective reduction of CO and NOX exhaust contents, on the basis which will now be described. Namely, the inventors noted that when burners having no such flame-sustainer metallic netting 22 are used under considerable combustion loads and high excessive primary air ratio, there is then a tendency for lift of the flame to occur in a portion of the combustion surface 2 near the end portion where it is supported by and connected to the burner body structural portion 4.An investigation revealed, as the cause, that the temperature of the connection end portion is so low in such case, owing to heat conduction from the metallic netting 1 to the burner body structural portion 4, as to fail to sustain there stable ignition of the gas. Various experiments were then made to find out how to prevent such failure, and these confirmed that the provision of the flame-sustainer metallic netting 22 as described hereinabove serves effectively to prevent such lift of the flame, apparently because heat conduction from the flame-sustainer metallic netting 22 to the burner body structural portion 4 is hindered by the presence of the metallic netting 1 interposed therebetween. However, the flame-sustainer metallic netting 22 is intensively heated, on the one hand directly by the high-temperature tip or end portion of the flame created through the metallic netting 1, and on the other hand by radiant heat from the portion of the metallic netting 1 by virtue of stable-flame combustion, and is thus stably maintained at a sufficiently high temperature to sustain spontaneous ignition of the gas.
Claims (11)
1. A surface combustion type burner having, in operation, a single-stage air supply which is entirely primary air, equipped with metallic netting having front and rear surfaces, with the front surface defining a combustion surface, wherein, in close supporting contact behind the metallic netting, substantially all over the entire rear surface thereof, there is disposed a punched or perforated metal base which has an open or void perforation ratio smaller than that of the said metallic netting.
2. The burner claimed in claim 1, wherein the void perforation ratio of the perforated metal base is in the range of 5-15%.
3. The burner claimed in claim 1 or 2, further comprising a flow distributor tube of permeable porous material, having an outer peripheral surface spaced from the perforated metal base on the side of the rear side thereof in such a manner that, in operation, when a combustible gas/air mixture is supplied to one end of this flow distributor tube, a portion of the gas/air mixture permeatingly flows through the porous material to the outer peripheral surface radially outwardly of the tube, while the remaining portion of the gas/air mixture flows directly to the other end of the tube longitudinally thereof, whereafter it may flow radially and flow back in a reverse longitudinal direction to any portion of the outer peripheral surface.
4. The burner claimed in claim 3, wherein the flow distributor tube is made of punched or perforated metal.
5. The burner claimed in claim 3 or 4, wherein the metallic netting and the perforated metal base are both of tubular form, and the flow distributor tube is disposed substantially centrally of such tubular netting and base.
6. The burner claimed in claim 5, including a burner body structural portion, a flamesustainer metallic netting disposed as a ringlike wrapping around and radially outwardly of the tubular metallic netting near an end portion thereof supportingly connected to the burner body structural portion.
7. A surface combustion type burner substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.
8. A surface combustion type burner substantially as hereinbefore described with reference to Fig. 5 of the accompanying drawings.
9. A surface combustion type burner substantially as hereinbefore described with reference to Fig. 6 of the accompanying drawings.
10. A surface combustion type burner substantially as hereinbefore described with reference to Fig. 7 of the accompanying drawings.
11. A surface combustion type burner substantially as herein before described with reference to Fig. 8 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08214296A GB2120771B (en) | 1982-05-17 | 1982-05-17 | Surface combustion type burner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08214296A GB2120771B (en) | 1982-05-17 | 1982-05-17 | Surface combustion type burner |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2120771A true GB2120771A (en) | 1983-12-07 |
| GB2120771B GB2120771B (en) | 1985-08-29 |
Family
ID=10530402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08214296A Expired GB2120771B (en) | 1982-05-17 | 1982-05-17 | Surface combustion type burner |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2120771B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2214629A (en) * | 1988-01-27 | 1989-09-06 | Burco Dean Appliances Ltd | Gas burner assembly |
| GB2237104A (en) * | 1989-10-20 | 1991-04-24 | Bowin Designs Pty Ltd | Gas burner |
| AU635780B2 (en) * | 1989-10-20 | 1993-04-01 | Bowin Technology Pty Limited | Gas burner |
| WO2016003300A1 (en) * | 2014-07-02 | 2016-01-07 | Aic Spółka Akcyjna | Combustion chamber for a gas-fired heat exchanger |
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| GB953568A (en) * | 1961-08-17 | 1964-03-25 | Caloric Appliance Corp | Improvements in or relating to radiant heaters |
| GB980441A (en) * | 1960-03-30 | 1965-01-13 | Getz Bros & Co Inc | Infra-red heaters |
| GB982376A (en) * | 1961-12-14 | 1965-02-03 | Dravo Corp | Improvements in or relating to a gas burner |
| GB1029774A (en) * | 1962-12-11 | 1966-05-18 | Hupp Corp | Infrared burner and method of producing infrared radiation |
| GB1038616A (en) * | 1962-04-28 | 1966-08-10 | Giuseppe Longhi | Gas burner |
-
1982
- 1982-05-17 GB GB08214296A patent/GB2120771B/en not_active Expired
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB857100A (en) * | 1957-05-07 | 1960-12-29 | Bourguignonne Mec Smb | Apparatus for the emission of infra-red radiation |
| GB905529A (en) * | 1957-12-24 | 1962-09-12 | Financ Et Ind Pour La Fabricat | Improvements in or relating to infra-red radiating apparatus |
| GB980441A (en) * | 1960-03-30 | 1965-01-13 | Getz Bros & Co Inc | Infra-red heaters |
| GB953568A (en) * | 1961-08-17 | 1964-03-25 | Caloric Appliance Corp | Improvements in or relating to radiant heaters |
| GB982376A (en) * | 1961-12-14 | 1965-02-03 | Dravo Corp | Improvements in or relating to a gas burner |
| GB1038616A (en) * | 1962-04-28 | 1966-08-10 | Giuseppe Longhi | Gas burner |
| GB1029774A (en) * | 1962-12-11 | 1966-05-18 | Hupp Corp | Infrared burner and method of producing infrared radiation |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2214629A (en) * | 1988-01-27 | 1989-09-06 | Burco Dean Appliances Ltd | Gas burner assembly |
| GB2214629B (en) * | 1988-01-27 | 1991-09-04 | Burco Dean Appliances Ltd | Gas burner assemblies |
| GB2237104A (en) * | 1989-10-20 | 1991-04-24 | Bowin Designs Pty Ltd | Gas burner |
| AU635780B2 (en) * | 1989-10-20 | 1993-04-01 | Bowin Technology Pty Limited | Gas burner |
| GB2237104B (en) * | 1989-10-20 | 1993-07-21 | Bowin Designs Pty Ltd | Gas burner |
| WO2016003300A1 (en) * | 2014-07-02 | 2016-01-07 | Aic Spółka Akcyjna | Combustion chamber for a gas-fired heat exchanger |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2120771B (en) | 1985-08-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19920517 |