Patent Publication Number: US-7721726-B2

Title: Gas radiation burner

Description:
This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 10-2006-0000555 filed in Korea on Jan. 3, 2006 and Patent Application No. 10-2006-0011289 filed in Korea on Feb. 6, 2006, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a gas radiation burner. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for supplying a mixed gas uniformly and accelerating combustion of the gas. 
   2. Discussion of the Related Art 
   Generally, a gas radiation burner provided to a gas oven or range is a device for cooking in a manner of heating an object by radiant waves generated from a radiant body that is heated as a mixed gas burns. This mixed gas includes gas and air. 
   In particular, since a glass is placed over the gas radiation burner, the glass can prevent the flame from being externally exposed. Therefore, a fire can be prevented. In addition, the gas radiation burner facilitates cleaning to enhance its convenience for use. 
   An example of a gas radiation burner  10  according to a related art is explained in detail with reference to  FIG. 1  and  FIG. 2  as follows.  FIG. 1  is a schematic layout of a gas radiation burner according to a related art and  FIG. 2  is a cross-sectional diagram of the gas radiation burner along a cutting line II-II shown in  FIG. 1 . Referring to  FIG. 1  and  FIG. 2 , a gas radiation burner according to a related art mainly includes a mixing pipe  2 , a burner pot  4 , a burner mat  6 , a burner housing  8  and a glass  10 . 
   The mixing pipe  2  provides a space into which a gas fuel and air are introduced to be primarily mixed. In this case, the gas fuel is sprayed from a nozzle  1  that configures a gas supply member. In addition, the air is introduced into the mixing pipe  2  by a spray pressure of the gas fuel to be mixed therein. 
   A lower portion of the burner pot  4  is connected to the mixing pipe  2  to provide a space, into which the mixed gas supplied from the mixing pipe  2  is introduced therein. 
   The burner mat  6  is mounted on a mounting part  5  provided over the burner pot  2 . The burner mat  6  plays a role as a radiant body that generates radiant waves when the mixed gas introduced into the burner pot  4  burns. 
   The burner housing  8  plays a role as a body of the gas radiation burner. The burner pot  4  is locked to the burner housing  8 . An object to be heated is placed on the burner housing  8 . In this case, the burner housing  8  is provided with a circular opening  9  through which the radiant energy emitted from the burner mat  6  passes. 
   The glass  10  is placed on the burner housing  8 . The object to be heated is placed onto the glass  10 . Besides, an outlet  11  is provided within the burner housing  8 . Therefore, an exhaust gas produced from burning the mixed gas is discharged via the outlet  11 . 
   An operation of the above-configured gas radiation burner is explained as follows. First of all, a user puts an object to be heated onto the glass  10  and then activates the gas radiation burner. Subsequently, a gas fuel and air are introduced into the mixing pipe  2  respectively. The introduced gas fuel and air are supplied to the burner pot  5  and mixed together. The mixed gas is then sprayed via the burner mat  6 . 
   Simultaneously, the mixed gas is ignited by a prescribed ignition device (not shown in the drawings) and is then burnt on the burner mat  6 . As the mixed gas is burnt, the burner mat  6  is heated to emit radiant energy. Therefore, the object put on the glass  10  is heated by the generated radiant energy. In this case, an exhaust gas generated from the combustion of the mixed gas at about 500° C. or higher is discharged via the outlet  11  provided within the burner housing  8 . 
   However, the related art gas radiation burner has the following problems. 
   First of all, since the mixing pipe  2  of the conventional gas radiation burner is connected to the lower portion of the burner pot  4 , the entire gas radiation burner is thick and would be difficult to make the gas radiation burner structurally compact. 
   Secondly, in the related art gas radiation burner, since the gas and air are supplied via the mixing pipe  2  provided to one side of the gas radiation burner and are mixed with each other within the burner pot  4 , a mixed rate between the gas and air is deflectively and non-uniformly distributed within the burner pot  4 . Therefore, incomplete combustion takes place locally, whereby irregular combustion takes place on a surface of the burner mat  6 . The irregular surface combustion reduces combustion efficiency, increases the amount of a discharge gas, and lowers heat efficiency of the gas radiation burner. 
   Thirdly, the burner mat  6  is formed of a ceramic-based material in general. Since a temperature for sustaining durability is low due to properties of the ceramic-based material, the corresponding durability of the burner mat  6  is low. 
   Fourthly, the burner mat  6  has difficulty in generating a large amount of heat, thereby reducing efficiency. In particular, since it is better to keep a temperature of the ceramic-based burner mat  6  low to extend its life span due to the material properties of the burner mat  6 , it is difficult to raise the temperature over a prescribed temperature. Hence, it further limits the amount of heat generated on the burner mat  6 . 
   Fifthly, the ceramic-based burner mat  6  has low thermal conductivity due to the properties of the ceramic-based material. Since it takes longer to accumulate heat, radiant efficiency of the burner mat  6  is low. 
   Finally, since gas and air are mixed together in the burner pot  4  of the related art gas radiation burner, the burner pot  4  should be provided with a sufficient internal space to well mix the gas and air. Therefore, it is difficult to reduce the size of the burner pot  4 . In particular, if a height of the burner pot  4  is lowered, the flow resistance of the gas and air is increased within the burner pot  4 . Therefore, the gas and air cannot be well mixed together if a height of the burner pot  4  is lowered. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a gas radiation burner that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
   An object of the present invention is to provide a gas radiation burner, by which a well mixed gas is uniformly supplied to a burner pot of the gas radiation burner. 
   Another object of the present invention is to provide a gas radiation burner, by which combustion is accelerated on a surface of a burner mat. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a gas radiation burner includes a gas supply member for injecting a gas; at least one mixing pipe producing a mixed gas by sucking air together with the gas injected by the gas supply member, the at least one mixing pipe uniformly injecting the mixed gas; a burner pot having a lateral side opening connected to the at least one mixing pipe to accommodate the mixed gas supplied by the at least one mixing pipe; a burner mat provided over the burner pot to emit radiant heat generated by combustion of the mixed gas supplied by the burner pot; and a burner housing provided on the burner mat to provide a combustion room. 
   In another aspect of the present invention, a gas radiation burner includes a gas supply member for injecting a gas; at least one mixing pipe sucking to supply air together with the gas injected by the gas supply member; a burner pot accommodating to supply a mixed gas supplied by the at least one mixing pipe; a burner mat provided over the burner pot to emit radiant heat generated by combustion of the mixed gas supplied by the burner pot; a burner housing provided on the burner mat to provide a combustion room; and combustion accelerating means for accelerating the combustion on the burner mat. 
   In a further aspect of the present invention, a gas radiation burner includes a gas supply member for injecting a gas; at least one mixing pipe producing a mixed gas by sucking air together with the gas injected by the gas supply member, the at least one mixing pipe having a widening pipe shape to uniformly supply the mixed gas; a burner pot having a lateral side opening connected to the mixing pipe to accommodate the mixed gas; a burner mat provided over the burner pot to emit radiant heat generated by combustion of the mixed gas supplied by the burner pot; a burner housing provided on the burner mat to provide a combustion room; and combustion accelerating means for accelerating the combustion on the burner mat. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
       FIG. 1  is a schematic layout of a gas radiation burner according to a related art; 
       FIG. 2  is a cross-sectional diagram of the gas radiation burner along a cutting line II-II shown in  FIG. 1 ; 
       FIG. 3  is a perspective diagram of a gas oven or range provided with a gas radiation burner according to a preferred embodiment of the present invention; 
       FIG. 4  is a layout of a gas radiation burner according to a first preferred embodiment of the present invention; 
       FIG. 5  is a cross-sectional diagram along a cutting line V-V shown in  FIG. 4 ; 
       FIG. 6  is a cross-sectional diagram along a cutting line VI-VI shown in  FIG. 5 ; 
       FIG. 7  is a cross-sectional diagram of a gas radiation burner according to a modification of the first embodiment shown in  FIG. 4 , in which a connected state between a burner pot and a mixing pipe is shown; 
       FIG. 8  is a cross-sectional diagram of a gas radiation burner according to a second embodiment of the present invention, in which a connected state between a burner pot and a mixing pipe is shown; 
       FIG. 9  is a layout of a gas radiation burner according to a third preferred embodiment of the present invention; 
       FIG. 10  is a cross-sectional diagram along a cutting line X-X shown in  FIG. 9 ; 
       FIG. 11  is an enlarged diagram of a burner mat shown in  FIG. 10 ; 
       FIG. 12  is a layout of a gas radiation burner according to a fourth preferred embodiment of the present invention; and 
       FIG. 13  is a cross-sectional diagram along a cutting line XIII-XIII shown in  FIG. 12 . 
   

   DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
   First of all, a gas oven or range employing a gas radiation burner according to an embodiment of the present invention is explained with reference to  FIG. 3 . In addition,  FIG. 3  shows an example of a built-in type gas oven or range. Referring to  FIG. 3 , a gas oven or range includes a body  100 , an oven part  110 , a grill part  112  and a top burner part  114  including a plurality of gas radiation burners  130 . 
   The body  100  configures an exterior of the gas oven or range. The oven part  110  is provided to a lower part of the body  100  and configures a space for cooking food by convection using a plurality of heaters (not shown in the drawing) provided within the oven part  110 . The grill part  112  configures a space for cooking food such as fish, meat and the like using radiant heat. 
   A plurality of gas radiation burners  130  are provided to an upper part of the body  100  to cook food by heating a container accommodating the food therein. In addition, a glass ( 134  in  FIG. 5 ) formed of a ceramic-based material is provided to an opening over the corresponding gas radiation burner  130 . 
     FIG. 4  is a layout of a gas radiation burner according to a first preferred embodiment of the present invention adopted by the gas oven or range shown in  FIG. 3 .  FIG. 5  is a cross-sectional diagram along a cutting line V-V shown in  FIG. 4 . Referring to  FIG. 4  and  FIG. 5 , a gas radiation burner  130  includes a mixing pipe  135  into which air and a fuel gas injected via a gas supply pipe  137  and a nozzle  136  are introduced, a burner pot  131  supplied with a mixed gas from the mixing pipe  135 , a burner mat  131  emitting radiant heat by a combustion of the mixed gas supplied by the burner pot  131 , a burner housing  133  configuring a combustion room, and a glass  134  provided over the burner housing  133 . 
   The above-configured gas radiation burner  130  according to the first embodiment of the present invention differs from the related art gas radiation burner in a configuration of the mixing pipe  135 . In the following description, the mixing pipe  135  is mainly explained. 
   In accordance with this embodiment of the present invention, the mixing pipe  135  is connected to a lateral side of the burner pot  131  to supply the mixed gas into the burner pot  131 . Thus, the thickness of the gas radiation burner of this illustrated embodiment can be reduced remarkably, compared with the conventional structure in which a mixing pipe is connected to a lower portion of the burner pot. 
     FIG. 6  is a cross-sectional diagram along a cutting line VI-VI shown in  FIG. 5 , in which the mixing pipe  135  of the gas radiation burner according to the first embodiment of the present invention is shown in detail. Referring to  FIG. 6 , the mixing pipe  135  is provided to one lateral side of the burner pot  131 . The mixing pipe  135  is configured to have an exit side in a widening pipe shape. Namely, an exit side of the mixing pipe  135  is wider than an entrance side of the mixing pipe  135 . In particular, the extension lines  135 A extending from both sides of an exit of the mixing pipe  135  are configured to enclose a whole cross-section of the burner pot  131 . Therefore, the mixing pipe  135  is configured to come into contact with an outer circumference of the burner pot  131  having a circular cross-section. 
   Since the mixing pipe  135  is provided with a wide exit angle θ, it is very effective in securing a massive amount of combustion air. In addition, as shown in  FIG. 6 , the extension lines  135 A are tangent to the outer circumference of the burner pot  131  and the tangent points are at the two ends of the opening at the lateral side of the burner pot  131 . Since the mixing pipe  135  communicates with the burner pot  131  with a wide area, it is able to inject a mixed gas from a lateral side of the burner pot  131 . Therefore, the mixing pipe  131  is very advantageous in uniformly distributing mixed gas within the burner pot  131 . 
   A mesh  139  is provided to a connecting portion of the burner pot  131  connected to the mixing pipe  135  to recover a pressure by reducing a speed of the mixed gas injected from the mixing pipe  135 . The mesh  139  recovers the pressure by reducing the speed of the mixed gas into a prescribed level, thereby uniformly distributing the mixed gas within the burner pot  131  and enabling uniform surface combustion to proceed across the entire gas radiation burner. 
     FIG. 7  is a cross-sectional diagram of a gas radiation burner according to a modification of the first embodiment shown in  FIG. 4 , in which a connected state between a burner pot and a mixing pipe is shown. Referring to  FIG. 7 , a basic configuration of the present embodiment is equivalent to that of the first embodiment but differs from that of the first embodiment in that a pair of mixing pipes  165  are provided to both lateral sides of the burner pot  161  opposite to each other. 
   In the present embodiment, a pair of the mixing pipes  165  having wide exit angles, respectively, to provide sufficient air for combustion and to efficiently and uniformly mix the air and the gas. 
   As the mixed gas is injected on both lateral sides of the burner pot  161 , the mixing pipes  165  are very effective in uniformly distribute the mixed gas within the burner pot  161 . In particular, as the mixed gas are mingled by the injection pressure of the mixing pipe  165  and the mixed gas flow, the mixed gas can be evenly distributed within the burner pot  161 . Moreover, the mixed gas can be evenly injected on the burner mat  132 . 
   Meanwhile, in the gas radiation burner according to the first or modified embodiment of the present invention, the gas and the air are mixed in the mixing pipe and are then supplied to the burner pot. They can be evenly distributed even if an internal space of the burner pot is small. Therefore, the height and volume of the burner pot can be significantly reduced. Hence, it is able to configure a gas radiation burner having a compact size. It is also able to install the compact-sized gas radiation burner in a built-in type gas oven or range because of the feasibility in installation. 
   A gas radiation burner  140  according to a second preferred embodiment of the present invention is explained in detail with reference to  FIG. 8  as follows.  FIG. 8  is a cross-sectional diagram of a gas radiation burner according to a second embodiment of the present invention, in which a connected state between a burner pot and a mixing pipe is shown. A gas radiation burner  140  according to a third embodiment of the present invention differs from those of the aforesaid embodiments of the present invention in a configuration of a mixing pipe  145 . The differences will be explained hereinbelow. 
   Referring to  FIG. 8 , a mixing pipe  145  of a third embodiment of the present invention is bent by a prescribed angle, e.g., 90 degrees, to be connected to each lateral side of a burner pot  141 . Thus, if the mixing pipe  145  has a bent shape, a length of the mixing pipe  145  is increased so as to further mix the air and gas together within the corresponding mixing pipe  145 . Therefore, as the gas and air having been sufficiently mixed together within corresponding mixing pipe  145  are supplied to the burner pot  141 , it is able to prevent local flow deflection and non-uniformity of the mixed gas within the burner pot  141 . 
   Moreover, since the mixing pipe  15 , as shown in  FIG. 8 , is bent to be connected to the corresponding lateral side of the burner pot  141 , it is able to communicate with a large area of the burner pot  141 . Therefore, as the mixed gas is evenly injected on the large areas of the lateral sides of the burner pot  141 , it is advantageous in uniformly distribute the mixed gas within the burner pot  141 . 
   In particular, if the mixing pipe  145 , as shown in  FIG. 8 , is bent to be installed along the lateral side of the burner pot  141 , it is able to minimize a portion projected from the burner pot  141  while a length for mixing the gas and air along the internal space of the mixing pipe  145  is increased. Therefore, it is able to configure a compact size of a gas radiation burner by reducing an overall volume of the gas radiation burner. 
   Optionally, a direction adjusting member  143  can be provided to a connecting portion  148 , where the mixing pipe  145  is connected, of the burner pot  141 . In this case the direction adjusting member  143  guides a direction of the mixed gas injected from the mixing pipe  145  to evenly inject the mixed gas into the burner pot  141 . Optionally, a plurality of slots or slits  144  are provided to the direction adjusting member  143  so that the mixed gas can pass therethrough. 
   For instance, in order for the mixed gas to be injected at a wide injection angle from the mixing pipe  145 , a plurality of slits  144 , as shown in  FIG. 8 , are configured in a vertical direction to be externally widened from both ends of the mixing pipe  145 . 
     FIG. 9  is a layout of a gas radiation burner according to a third preferred embodiment of the present invention, and  FIG. 10  is a cross-sectional diagram along a cutting line X-X shown in  FIG. 9 . Comparing to the aforesaid embodiments of the present invention, the third embodiment of the present invention differs in having combustion accelerating means for accelerating combustion in a burner mat. The differences are explained hereinbelow. 
   Referring to  FIG. 9  and  FIG. 10 , a gas radiation burner  200  according to a third embodiment of the present invention includes a burner mat  230  provided with a catalyzing agent capable of reforming a mixed gas catalytically. The burner mat  230  provided with the catalyzing agent is explained in detail as follows. 
   First of all, the burner mat  230  provided with the catalyzing agent is an element for the catalytic reforming of a mixed gas introduced into a burner pot  220 . In particular, the burner mat  230  provided with a catalyzing agent such as Pt, Ni and the like raises an octane value by coming into contact with a mixed gas to reform mixed gas components. Thus, as the octane value of the mixed gas is raised by the catalyzing agent, combustion of the mixed gas is accelerated on a surface of the burner mat  230 . In this case, the catalyzing agent can be coated on the surface of the burner mat  230 . Alternatively, the burner mat  230  can be made of the catalyzing agent. 
   Besides, a plurality of belching holes  232 , as shown in  FIG. 11 , are provided to the burner mat  232  to enable a mixed gas to belch out of a lower side to an upper side. In this case, a diffusing portion  234  having an increasing end area is provided to each of the belching holes  232  to increase the belching efficiency of the mixed gas. 
   An operation of the above-configured gas radiation burner according to the third embodiment of the present invention is explained as follows. First of all, a mixed gas introduced into the burner pot  220  via the corresponding mixing pipe  210  belches out of the belching holes  232  of the burner mat  230 . 
   Simultaneously, the mixed gas is ignited by ignition means (not shown in the drawings) and is then burnt on a surface of the burner mat  230 . As the mixed gas is burnt to heat the burner mat  230 , the heated burner mat  230  emits radiant energy to cook an object to be heated. In this case, the mixed gas belching out of the belching holes  232  of the burner mat  230  are reformed to raise the octane value, whereby combustion of the mixed gas is accelerated on the surface of the burner mat  230 . 
   Therefore, as the combustion of the mixed gas on the surface of the burner mat  230  is accelerated, flames are stable on the burner mat  230  to improve combustion efficiency. As the combustion of the mixed gas is accelerated, the time for heating up the burner mat  230  is reduced. Therefore, it is able to quickly raise the temperature of the burner mat  230 . Hence, the thermal efficiency is raised. 
   As the combustion of the mixed gas is accelerated, it is able to reduce an amount of carbon monoxide produced from the combustion of the mixed gas. In addition, it is able to reduce environmental pollution by enhancing properties of an exhaust gas produced from the combustion of the mixed gas. 
     FIG. 12  is a layout of a gas radiation burner according to a fourth preferred embodiment of the present invention, and  FIG. 13  is a cross-sectional diagram along a cutting line XIII-XIII shown in  FIG. 12 . Referring to  FIG. 12  and  FIG. 13 , a gas radiation burner according to a fourth preferred embodiment of the present invention differs from those of the aforesaid embodiments of the present invention in further including a conduction member  310  accelerating combustion of a mixed gas. The conduction member  310  is explained in detail with reference to  FIG. 12  and  FIG. 13  as follows. 
   First of all, the conduction member  310  is provided over a burner mat  320  to have a shape corresponding to that of the burner mat  320 . In particular, the conduction member  310  is configured to have a circular disc shape corresponding to that of the burner mat  320  and is spaced apart from a top of the burner mat  320 . 
   Preferably, the conduction member  310  is made of a Ni—Cr alloy having high thermal conductivity. Since the burner mat  320  is normally formed of a ceramic-based material to have low thermal conductivity, radiant efficiency is low. Therefore, by using the conduction member  310  having high thermal conductivity, it is able to quickly heat up the conduction member  310  by the combustion occurring on a surface of the burner mat  320 . Accordingly, heat is transferred upward and downward, i.e., to an object to be heated and the burner mat  320 . Hence, it is able to accelerate the combustion of the mixed gas. It is also able to raise radiant efficiency by shortening a heating time of the burner mat  320 . 
   Meanwhile, it is preferable that a circular perforated portion  312  is provided to a center of the conduction member  310  to prevent overheating of the burner mat  320 . In particular, as the heat generated from the burner mat  320  is cut off, the conduction member  310  may still heat the burner mat  320  up, and the burner mat  320  can be overheated. To prevent the burner mat  320  from being overheated, the perforated portion  312  is provided to the center of the conduction member  310 . 
   Alternatively, the conduction member  310  can be provided outside a range of heating the burner mat  320 , which is not shown in the drawings. This is to prevent heating deviation of the burner mat  320 . In this case, the heating deviation may take place because a peripheral portion of the burner mat  320  in the vicinity of the conduction member  310  receives more heat from the conduction member  310  than another portion of the burner mat  320 , i.e., a central portion. 
   Alternatively, the conduction member can be configured with a wire shape instead of a plate shape, which is not shown in the drawings. In particular, the conduction member is formed of a heating wire including Ni—Cr alloy to have a length in a radial direction of the burner mat  320 . 
   An operation of the above-configured gas radiation burner according to the fourth embodiment of the present invention is explained as follows. First of all, a mixed gas introduced into the burner pot  220  via the mixing pipe  201  is belched via the burner mat  320 . Simultaneously, the mixed gas is ignited by ignition means (not shown in the drawings) to be burnt on a surface of the burner mat  320 . 
   In this case, since the conduction member  310  is provided over the burner mat  320 , the quick heating of the burner mat  320  accelerates the combustion of the mixed gas on the surface of the burner mat  320 , thereby forming flames on the burner mat  320  stably and enhancing combustion efficiency. As the combustion of the mixed gas is accelerated, the time to heat up the burner mat  320  is reduced, thereby increasing the radiant efficiency. As the combustion of the mixed gas is accelerated, it is able to reduce an amount of carbon monoxide produced from the combustion of the mixed gas. And, it is able to reduce environmental pollution by enhancing properties of an exhaust gas produced from the combustion of the mixed gas. 
   Accordingly, the present invention provides the following effects or advantages. 
   First of all, since the mixing pipe is connected to a lateral side of the burner pot, it is possible to reduce the thickness of the gas radiation burner and a compact structure of the gas radiation burner is practicable, as well. 
   Secondly, since air and gas flow within a mixing pipe to be mixed together, they can be sufficiently mixed to secure a sufficient amount of mixed air for combustion. 
   Thirdly, air and gas are mixed within a mixing pipe to be supplied to a burner pot and are then injected at a wide exit angle. Therefore, mixed gas distribution within the burner pot is even to enable stable and uniform surface combustion. Hence, combustion efficiency is raised and emitted radiant energy is increased. 
   Fourthly, it is able to reduce a size of a burner pot. As installation feasibility is enhanced, it is able to reduce an overall size of a gas radiation burner. Hence, it is able to install the gas radiation burner in various places such as a built-in type gas oven or range and the like. 
   Fifthly, as the combustion accelerating means accelerates combustion of a mixed gas, the time to heat up a burner mat is reduced. Hence, it is able to raise radiant efficiency. 
   Finally, as the combustion of a mixed gas is accelerated, an amount of carbon monoxide produced from the combustion of the mixed gas. Hence, it is able to reduce environmental pollution by reforming properties of an exhaust gas. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.