Cooking gas oven

Abstract

To provide a cooking gas oven suitable for cooking food to be cooked in a short time with good thermal efficiency.SOLUTION: A cooking gas oven 100 comprises a hearth 81, an oven main body 13 that forms a furnace chamber 16 with an entrance on the hearth, and a burner 83 that generates flame 85 in the furnace chamber, and having food to be cook placed in a food-to-be-cooked region on an upper surface of the hearth inside the furnace chamber. The cooking gas oven further comprises an inner furnace chamber chimney main body 62 in which the upper end and lower end are open and having a lower opening 63 at the cylinder side lower part, and the inner furnace chamber chimney main body is disposed so that the flame generated by the burner is surrounded, the lower end is in contact with or is close to the hearth, and the lower opening faces the food-to-be-cooked region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas cooking oven that is suitable for baking food with good thermal efficiency in a short time. [Background technology]

[0002] Various stone ovens and cooking gas ovens have been devised for baking delicious pizzas. One example is a cooking gas oven with a double-layered upper chamber to form an exhaust space, allowing pizzas to be quickly baked at high temperatures and checked for doneness. The exhaust space is connected to a chimney, through which combustion gases are exhausted, and a burner is installed on the side of the hearth (Patent Document 1). Another example is a food oven that uses high-power blast combustion to heat the oven's baking section until it reaches a temperature suitable for baking food. After the oven temperature rises, the oven maintains the temperature and bakes the food using low-power red flame combustion. This results in excellent baking efficiency and fuel efficiency, making it ideal for baking foods such as pizza. In this food oven, combustion gases exit the oven through an inlet and are drawn into the chimney through a hood at the top of the front and then exhausted (Patent Document 2).

[0003] FIG. 11 is a front view of a conventional gas-fired cooking kiln 800, and FIG. 12 is a side view of the gas-fired cooking kiln 800. FIG. 13 is a cross-sectional view taken along the line B-B of FIG. 12. The gas-fired cooking kiln 800 includes a hearth 81 having a hearth opening 82, a kiln body 13 that forms a furnace chamber 16 having an inlet 11 on the hearth 81, a chimney 12, a burner 83, and a controller 21 that controls the burner 83. The lower end of the exhaust passage 14 of the chimney 12 is the exhaust port 18. The burner 83, which generates a flame 85, is located in the hearth opening 82. The burner 83 has multiple flame holes 84 from which a mixed gas of air and fuel is ejected. The flame holes 84 are located in the hearth opening 82 so that the bottom of the flame 85 is positioned at the top surface of the hearth 81. The temperature detection portion of the temperature sensor 22 is disposed at a predetermined position in the furnace chamber 16 (slightly above the hearth 81, away from the inlet 11 and the flame holes 84). The temperature detected by the temperature sensor 22 is called the furnace chamber temperature. The furnace chamber temperature is displayed near the controller 21.

[0004] As can be seen from Patent Documents 1 and 2, conventional gas cooking kilns have various combustion gas exhaust structures (e.g., exhaust port location, exhaust path, etc.). In the gas cooking kiln 800, the exhaust port 18 is located on the opposite side of the center of the furnace chamber 16 from the flame holes 84, and the inlet 11 is located approximately equidistant from the exhaust port 18 and the flame holes 84. As can be seen from Patent Documents 1 and 2 and the gas cooking kiln 800, various exhaust structures have been put into practical use. However, in all of these exhaust structures, the vertical and horizontal distances between the exhaust port and the food being cooked are large. Furthermore, during cooking, heat dissipation from the hearth is significant downward, and the vertical temperature gradient of the combustion gas above the hearth is large. Therefore, the exhaust structure does not significantly affect the temperature and flow of the combustion gas above the food being cooked. In other words, the exhaust structure does not significantly affect the degree of doneness of the food being cooked. On the other hand, strong convection near the inlet caused by the large temperature difference between the combustion gas inside the furnace chamber and the outside air cools the area near the inlet, thereby affecting the degree of doneness of the food being cooked near the inlet. Therefore, it is preferable that the positions of the burner holes, exhaust port, and inlet be determined taking into consideration the influence of convection near the inlet.

[0005] After the latter half of the preheating period of the cooking gas kiln 800, the hearth 81 and the food are heated primarily by infrared radiation from the flame 85 and the furnace wall of the kiln body 13, and by convective heat transfer from the combustion gas convection above the hearth 81. The intensity of infrared radiation is highly dependent on the temperature and distance of the heat source, as well as the area of ​​the heat source. The temperature of the flame 85 is much higher than the temperature of the furnace wall of the kiln body 13, and the distance between the food and the flame 85 is smaller than the distance between the food and the furnace wall of the kiln body 13. Therefore, even though the area of ​​the flame 85 is smaller than the area of ​​the furnace wall of the kiln body 13, the hearth 81 and the food are primarily heated by infrared radiation from the flame 85. Furthermore, the outer edge of the food, which is perpendicular to the direction of infrared radiation, receives the most infrared radiation. Therefore, the outer edge of the food, which is closest to the flame 85, is prone to overcooking.

[0006] The solid and dashed arrows in Figure 13 indicate the main flow of combustion gas within the furnace chamber 16 during a substantially steady state (a state in which the flow and temperature of combustion gas within the furnace chamber 16 change little over time) after the latter half of preheating. The solid arrows indicate the flow of combustion gas generated and exhausted by combustion. External air and fuel are taken in by the burner 83, and the air-fuel mixture is ejected from the flame holes 84, where it burns, generating a flame 85. The high-temperature combustion gas generated by combustion rises, accumulates at the top of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then descends. The combustion gas descending near the exhaust port 18 is drawn into the exhaust port 18 and exhausted due to the chimney effect. Note that due to heat dissipation from the kiln body 13 to the outside air, there is a large temperature gradient in the perpendicular direction of the combustion gas near the furnace wall of the kiln body 13.

[0007] The dashed arrows indicate the convection of combustion gas circulating within the furnace chamber 16. As the high-temperature combustion gas generated by combustion rises, the combustion gas surrounding the combustion area where the flame 85 is generated is drawn into the combustion area. The drawn-in combustion gas mixes with the high-temperature combustion gas generated by combustion and rises, stagnates at the top of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then descends. The combustion gas descending near the inlet 11 is caught up in the convection generated at the inlet 11. The combustion gas descending away from the exhaust port 18 and the inlet 11 descends to the vicinity of the hearth 81, flows toward the hearth opening 82 where the surface temperature of the hearth 81 is high, and is then drawn into the combustion area. This convection of combustion gas generated by the flame 85 and circulating within the furnace chamber 16 is called furnace chamber convection. The reason why the surface temperature of the hearth 81 is higher closer to the hearth opening 82 is that (1) the hearth 81 is generally more strongly irradiated with infrared rays from the flame 85 and the furnace wall of the kiln body 13 the closer it is to the hearth opening 82. In other words, the increase in the surface temperature of the hearth 81 due to infrared irradiation is generally greater the closer it is to the hearth opening 82. (2) Since the speed of convection within the furnace chamber above the hearth 81 is greater closer to the hearth opening 82, the increase in the surface temperature of the hearth 81 due to convective heat transfer between the hearth 81 and the convection within the furnace chamber is greater the closer it is to the hearth opening 82. Due to (1) and (2), the surface temperature of the hearth 81 is higher closer to the hearth opening 82.

[0008] The vertical cross section of the flame 85 is elongated as shown in Figure 13. For the sake of diagrammatic explanation, in Figure 13, the flame 85 is divided into three parts, designated from bottom to top as Flame A, Flame B, and Flame C. Flames A, B, and C are assumed to generate furnace chamber convection A, furnace chamber convection B, and furnace chamber convection C, respectively, and each of these flows in a layered manner above the hearth 81. The reason the furnace chamber convection flows in a layered manner is that the downward heat radiation from the hearth 81 creates a large vertical temperature gradient in the combustion gas above the hearth 81, forming a temperature layer similar to thermal stratification in the lower center of the furnace chamber 16. Because furnace chamber convection A is in contact with the hearth 81, it heats the hearth 81 through convective heat transfer between the hearth 81 and the furnace chamber convection A. However, because furnace chamber convection B and furnace chamber convection C are not in contact with the hearth 81, they heat the hearth 81 via furnace chamber convection A. On the other hand, the internal convection currents B and C are heated by the flames B and C, rise, and heat the upper part of the furnace wall of the kiln body 13. In other words, the internal convection currents B and C mainly heat the furnace wall of the kiln body 13 at the upper part of the furnace chamber 16, and do not heat the hearth 81 very much.

[0009] 14 is a cross-sectional view taken along the line AA in FIG. 11 (viewed from above at a cross section near the center of flame A slightly above hearth 81). In FIG. 14, the temperature sensor 22 and exhaust port 18 are shown by dashed lines because they are located above the cross section. The convection current A indicated by the dashed arrow flows over the hearth 81 in the direction of flame A, with a width approximately equal to that of flame A, and the closer it is to flame A, the faster it flows. Because the speed of the convection current A is particularly high above the hearth 81 near flame A, the hearth 81 near flame A is likely to be excessively heated by convective heat transfer with the convection current A.

[0010] Figure 15 shows a cross-sectional view of Figure 12 taken along the line B-B when food 26 is placed in food area 27 on the hearth 81 of cooking gas oven 800. When the furnace chamber temperature is appropriate for cooking and food 26 is placed in food area 27, the combustion gas directly above food 26 is cooled by food 26, keeping the temperature of the combustion gas low and approximately constant. Therefore, the flow of combustion gas directly above food 26 (the lowest layer of convection A within the furnace chamber) temporarily stops. Immediately thereafter, the viscosity of the combustion gas causes the lowest layer of convection A within the furnace chamber to begin flowing, initiating convective heat transfer between food 26 and convective heat transfer within the furnace chamber. Therefore, the surface of food 26 is more strongly cooked by convective heat transfer, depending on the width of flame A, the closer it is to flame A, and the outer edge of the food closest to flame A is more likely to be overcooked. The outer edge of the food closest to flame A is also more likely to be overcooked by infrared radiation. The backside of the food 26 is cooked by the hearth 81, which is heated by infrared radiation and convective heat transfer with the convection in the oven chamber. Therefore, when the food 26 is cooked in the gas cooking oven 800, the outer edge of the food 26 is likely to be overcooked by the infrared radiation and convective heat transfer.

[0011] The energy generated by combustion is approximately equal to the sum of the infrared energy and the heat transferred to the convection within the furnace chamber. The flame 85 radiates infrared rays in all directions. Most of the infrared rays irradiate and overheat the furnace wall of the kiln body 13 above the furnace chamber 16. Some of the infrared rays directly irradiate the hearth 81 and the food 26. Furthermore, the heat generated by combustion is transferred to the convection within the furnace chamber A, the convection within the furnace chamber B, and the convection within the furnace chamber C. However, the heat transferred to the convection within the furnace chamber B and the convection within the furnace chamber C is mainly used to overheat the furnace wall of the kiln body 13 above the furnace chamber 16, while only the heat transferred to the convection within the furnace chamber A is used to heat the hearth 81 or roast the food 26. Therefore, the furnace wall of the kiln body 13 above the furnace chamber 16 is overheated and the heat is wasted and radiated to the outside, resulting in low thermal efficiency of the gas cooking kiln 800.

[0012] In a wood-fired stone oven, when the temperature inside the hearth is appropriate for roasting food, embers from the firewood are widely distributed around the area of ​​the food being cooked on the hearth, and the firewood burns on top of the embers. The convection of combustion gases circulating inside the hearth consists of the convection of combustion gases generated by the embers and circulating inside the hearth (called ember convection inside the hearth) and the convection of combustion gases generated by the firewood flames and circulating inside the hearth (called wood-fired flame convection inside the hearth). Because the embers are widely distributed around the area of ​​the food being cooked on the hearth, the heat of the embers is strong slightly above the hearth, and the convection inside the hearth flows slightly above the hearth, the hearth and food being heated in a broad, parallel manner, and the outer edges of the hearth and food being cooked near the embers are less likely to be overheated. Because the firewood flames are located above the hearth and have a relatively weak heat output, convection within the wood-fired furnace chamber is relatively weak, and the infrared rays from the firewood flames are also weak, making it difficult for the furnace walls of the oven body at the top of the furnace chamber to be overheated. Therefore, the thermal efficiency of a stone oven is usually higher than that of the gas cooking oven 800. Furthermore, food cooked in a stone oven is cooked parallel to the width of the embers, making it difficult for the outer edges of the food to be overcooked, so the cooking doneness of food cooked in a stone oven is much better than that of food cooked in the gas cooking oven 800. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-235436 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-159940 Summary of the Invention [Problem to be solved by the invention]

[0014] In conventional gas-fired cooking kilns, the burner flame is elongated, so most of the heat from combustion is used to heat the upper part of the kiln through convection within the furnace chamber, and only a portion of the heat is used to heat the hearth and to roast the food. Furthermore, most of the infrared energy emitted from the flame is used to heat the upper part of the kiln, and only a portion of that energy is used to heat the hearth and to roast the food. Therefore, the thermal efficiency of conventional gas-fired cooking kilns is low. Furthermore, the outer edges of the food close to the flame are prone to overcooking due to the convective heat transfer caused by infrared radiation from the flame and convection within the furnace chamber.

[0015] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a gas cooking oven which has high thermal efficiency, can roast food in a short time, and also roasts food to a good degree. [Means for solving the problem]

[0016] In order to solve the above problems, the cooking gas kiln of the present invention comprises a hearth, a kiln body forming a furnace chamber having an entrance on the hearth, and a burner that generates a flame within the furnace chamber, and the food to be cooked is placed in the food to be cooked area on the upper surface of the hearth within the furnace chamber, and further comprises a cylindrical furnace chamber chimney body that is open at the top and bottom ends and has a lower opening at the bottom of the side of the tube, and the furnace chamber chimney body surrounds the flame generated by the burner, and is positioned so that its lower end is in contact with or close to the hearth, and its lower opening faces the food to be cooked area.

[0017] In the gas cooking oven of the present invention, the chimney body inside the furnace chamber preferably has a light passing portion on the side surface of the tube above the lower opening through which light passes.

[0018] The gas-fired cooking oven of the present invention preferably further comprises an extension passage forming member, one end of which has an extension passage inlet opening substantially horizontally toward the food-to-be-cooked area and the other end of which communicates with the lower opening. The extension passage inlet is preferably located above the hearth.

[0019] Preferably, the cooking gas oven of the present invention further comprises a flow rate adjusting member disposed in the extension passage for adjusting the speed of the combustion gas drawn into the extension passage inlet across the width.

[0020] In addition, it is preferable that the cooking gas kiln of the present invention has a flow rate adjusting body that comprises a pair of side partition plates arranged approximately parallel to both sides of the extension passage, and a pair of central partition plates, one of which is arranged so as to approach one of the pair of side partition plates from the center of the extension passage entrance toward the lower opening, and the other of which is arranged so as to approach the other of the pair of side partition plates from the center of the extension passage entrance toward the lower opening. [Effects of the Invention]

[0021] In a gas-fired cooking kiln according to the present invention, the furnace chamber chimney body is disposed within the furnace chamber of the cooking kiln. When combustion occurs in the furnace chamber chimney passage formed by the furnace chamber chimney body, the combustion gases heated to a high temperature rise through the furnace chamber chimney passage. As the combustion gases rise, they are drawn into the lower opening, generating a convection current of combustion gases circulating within the furnace chamber (called chimney convection). The chimney convection flows above the hearth, which is intensely heated by convective heat transfer with the chimney convection. Furthermore, infrared energy is converted into heat in the furnace chamber chimney body, heating the rising combustion gases and increasing the speed of the chimney convection. The increased speed further heats the hearth through convective heat transfer between the hearth and the chimney convection. Therefore, in a gas-fired cooking kiln, the heat of combustion and infrared energy generate chimney convection, which heats the hearth through convective heat transfer and roasts the food being cooked. Therefore, the thermal efficiency of gas cooking ovens is extremely high.

[0022] Furthermore, while the chimney body inside the furnace chamber is usually opaque, the light from the flame passes through the light passage and illuminates the food, allowing the food to be observed as it cooks. By locating the extension passage inlet, through which combustion gases are drawn, near the food, the speed of the chimney convection above the food can be increased, allowing the food to be thoroughly cooked through convective heat transfer with the chimney convection. By locating the extension passage inlet above the hearth, excessive overcooking of the outer edges of the food can be reduced. A chimney chamber equipped with a furnace chamber chimney body, an extension passage forming member, and a flow rate adjusting member adjusts the width of the chimney convection above the hearth to the width of the food, maintaining a roughly constant speed in the width direction and cooking the food in a parallel pattern, resulting in a good cooking result. The flow rate adjusting member can be easily constructed using a pair of side partitions and a pair of center partitions. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 2 is a perspective view showing one embodiment of the furnace chamber chimney body of the present invention. [Figure 2] FIG. 2 is an end view of the cooking gas kiln of the present invention, in which the chimney body is disposed in the furnace chamber. [Figure 3] 3 is a cross-sectional view of the gas cooking oven shown in FIG. 2, taken from above, at a section slightly above the hearth. [Figure 4] FIG. 10 is a perspective view showing another embodiment of the furnace chamber chimney body. [Figure 5] FIG. 10 is an end view of the cooking gas kiln of the present invention, in which the chimney body is arranged in the furnace chamber according to another embodiment. [Figure 6] FIG. 6 is a cross-sectional view of the gas cooking oven shown in FIG. 5, taken from above, at a section slightly above the hearth. [Figure 7] FIG. 1 is a perspective view showing one embodiment of a furnace chamber chimney having a furnace chamber chimney main body, an extension passage forming body, and a flow velocity adjusting body. [Figure 8] FIG. 2 is an end view of the cooking gas kiln of the present invention with the chimney arranged in the furnace chamber. [Figure 9] 1 is a cross-sectional view of a section slightly above the hearth of a gas cooking kiln in which a chimney is located inside the furnace chamber, viewed from above. [Figure 10]FIG. 10 is a cross-sectional view of another example of a gas cooking kiln with a chimney arranged in the furnace chamber, taken from above, showing a section slightly above the hearth. [Figure 11] FIG. 1 is a front view showing an example of a conventional gas cooking oven. [Figure 12] FIG. 12 is a side view of the cooking gas oven of FIG. [Figure 13] FIG. 13 is a BB end view of FIG. 12. [Figure 14] 12 is a cross-sectional view taken along the line AA in FIG. 11. [Figure 15] 13 is a BB end view of FIG. 12 when an object to be cooked is placed thereon. DETAILED DESCRIPTION OF THE INVENTION

[0024] The cooking gas kiln of the present invention will be described below based on various embodiments with reference to the drawings. FIG. 1 is a perspective view showing one embodiment of a furnace chamber chimney body arranged in a cooking gas kiln of the present invention. The furnace chamber chimney body 62 is cylindrical, forms a furnace chamber chimney passage 64, and has a lower opening 63 at the bottom of the side of the tube. The lower end and upper end opening 65 of the furnace chamber chimney body 62 are vertically open. FIG. 2 is a cross-sectional view of a cooking gas kiln 100 in which the furnace chamber chimney body 62 is arranged so that it surrounds a flame 85, the lower end of the furnace chamber chimney body 62 is in contact with a hearth 81, and the lower opening 63 faces the food area 27 (see FIG. 3). To generate the flame 85 in the furnace chamber chimney passage 64, a flame port 84 must be located near the bottom of the furnace chamber 16, but a hearth opening 82 is not necessarily required. Furthermore, since combustion gas can be exhausted through an inlet 11, a chimney 12 is not necessarily required.

[0025] The arrows in Figure 2 show the flow of combustion gas when the cooking gas kiln 100 is in a substantially steady state after the latter half of preheating. Solid arrows indicate the flow of combustion gas generated and exhausted by combustion. External air and fuel are drawn into the burner 83, and the air-fuel mixture is ejected from the flame holes 84, generating a flame 85 in the furnace chamber chimney passage 64. The high-temperature combustion gas generated by combustion in the furnace chamber chimney passage 64 is much hotter than the combustion gas outside the furnace chamber chimney main body 62. Therefore, the high-temperature combustion gas rises up the furnace chamber chimney passage 64 due to the chimney effect, accumulates at the top of the furnace chamber 16, and is cooled by the furnace wall of the kiln main body 13 before descending. The combustion gas descending near the exhaust port 18 is drawn into the exhaust port 18 and exhausted due to the chimney effect. Note that much of the infrared radiation emitted from the flame 85 irradiates the furnace chamber chimney main body 62 and is converted into heat. The heat heats the combustion gases rising through the chimney passage 64 inside the furnace chamber, increasing the rate at which the combustion gases rise.

[0026] The dashed arrows indicate the convection of combustion gas circulating within the furnace chamber 16. As the high-temperature combustion gas rises in the furnace chamber chimney passage 64, the combustion gas above the hearth 81 is drawn into the lower opening 63. The drawn-in combustion gas mixes with the high-temperature combustion gas generated by combustion and rises, stagnates at the top of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then descends. Combustion gas descending near the inlet 11 is caught up in the convection generated at the inlet 11. Combustion gas descending away from the exhaust port 18 and inlet 11 descends to the vicinity of the hearth 81, flows toward the lower opening 63, where the surface temperature of the hearth 81 is higher, and is then drawn into the lower opening 63. This convection of combustion gas circulating within the furnace chamber 16 is called the first chimney convection. The reason why the surface temperature of the hearth 81 is higher closer to the lower opening 63 is that (1) the rise in the surface temperature of the hearth 81 due to irradiation of infrared rays from the furnace wall of the kiln body 13 is generally greater closer to the lower opening 63. Note that infrared rays from the flame 85 are blocked by the chimney body 62 inside the furnace chamber, so the hearth 85 is not irradiated. (2) The speed of the first chimney convection above the hearth 81 is greater closer to the lower opening 63, so the rise in the surface temperature of the hearth 81 is greater closer to the lower opening 63 due to convective heat transfer between the hearth 81 and the first chimney convection. Due to (1) and (2), the surface temperature of the hearth 81 is higher closer to the lower opening 63. Therefore, the first chimney convection heats the hearth 81 through convective heat transfer with the hearth 81, particularly strongly heating the hearth 81 near the lower opening 63. When the lower end of the furnace chamber chimney body 62 is close to the hearth 81, it is preferable that the distance between the lower end of the furnace chamber chimney body 62 and the hearth 81 is sufficiently narrow. In addition, it is preferable that the gap at the hearth opening 82 is closed with a member.

[0027] FIG. 3 is a top-down cross-sectional view of a section just above the hearth 81 of the gas cooking oven 100. The dashed arrow indicates the first chimney convection just above the hearth 81. The first chimney convection flows over the hearth 81 toward the lower opening 63, with a width roughly equal to the width of the lower opening 63, and its velocity increases as it approaches the lower opening 63. Therefore, the hearth 81 is heated in a broad, parallel fashion by convective heat transfer with the first chimney convection. Furthermore, when food is placed in the food area 27, the surface of the food is baked in a broad, parallel fashion by convective heat transfer with the first chimney convection. Therefore, the chimney body 62 within the furnace chamber generates a first chimney convection by the heat from combustion and the infrared energy from the flame 85. The surface of the food is baked in a broad, parallel fashion by convective heat transfer with the first chimney convection, and the backside of the food is baked by the hearth 81, which is heated in a broad, parallel fashion by convective heat transfer with the first chimney convection.

[0028] The flow of the first chimney convection above the hearth 81 is similar to the flow of the furnace chamber convection A above the hearth 81 of the cooking gas kiln 800. However, the cooking gas kiln 100 does not have combustion gas convection corresponding to the furnace chamber convection B and furnace chamber convection C, which overheat the furnace wall of the kiln body 13 and wastefully release heat. Furthermore, while the cooking gas kiln 800 uses most of the infrared energy to heat the furnace wall of the kiln body 13, the cooking gas kiln 100 uses the infrared energy to heat the hearth 81 and the food being cooked. Therefore, the thermal efficiency of the cooking gas kiln 100 is much higher than that of the cooking gas kiln 800. Furthermore, while the cooking gas kiln 800 is prone to overcooking the outer edge of the food being cooked near the flame 85, the cooking gas kiln 100 does not experience such overcooking due to infrared rays. Furthermore, since the first chimney convection flows directly above the hearth 81, the hearth 81 near the lower opening 63 is excessively heated by convection heat transfer, which can easily cause the outer edges of the food to be cooked to be overcooked.

[0029] The flow of the first chimney convection above the hearth 81 is similar to the flow of the first chimney convection above the hearth in a stone oven. However, the cooking gas kiln 100 does not have combustion gas convection corresponding to the wood-fired furnace convection, which overheats the upper part of the kiln body and wastes heat. Therefore, the cooking gas kiln 100 has higher thermal efficiency than a stone oven. Furthermore, in a stone oven, food is baked in a wide, parallel pattern due to convective heat transfer with the convection within the furnace chamber, and the convection within the furnace chamber flows slightly above the hearth, making excessive overcooking due to convective heat transfer less likely. On the other hand, in the cooking gas kiln 100, food is baked in a wide, parallel pattern due to convective heat transfer with the first chimney convection, but because the first chimney convection flows directly above the hearth 81, excessive overcooking due to convective heat transfer is likely to occur. The speed of the first chimney convection increases as the temperature difference between the temperature of the combustion gas around the furnace chamber chimney body 62 and the average temperature of the combustion gas in the furnace chamber chimney passage 64 increases, so it is preferable that the furnace chamber chimney body 62 include a highly insulating material or layer. Furthermore, it is preferable that the furnace chamber chimney body 62 have a material or structure that efficiently transmits infrared energy from the flame 85 to the combustion gas.

[0030] FIG. 4 is a perspective view showing another embodiment of the furnace chamber chimney body. The furnace chamber chimney body 32 is cylindrical, forms a furnace chamber chimney passage 34, and has a lower opening 33 at the bottom of the tube side. The lower end of the furnace chamber chimney body 32 opens vertically, and the upper opening 35 opens approximately horizontally. The shape of the upper opening 35 is equal to the cross-sectional shape of the vertical portion of the furnace chamber chimney passage 34. FIG. 5 is a cross-sectional view of a cooking gas kiln 200 equipped with the furnace chamber chimney body 32. The cooking gas kiln 200 uses a burner 23 with a lower heat output and fewer flame holes than the burner 83. The cross-sectional area of ​​the furnace chamber chimney body 32 is smaller than that of the furnace chamber chimney body 62. The furnace chamber chimney body 32 surrounds the flame 25, its lower end contacts the hearth 15, and the lower opening 33 faces the food area 27. The flame 25 is generated in the furnace chamber chimney passage 34. It is preferable that the gap at the hearth opening 17 is closed with a member.

[0031] The arrows in Figure 5 show the flow of combustion gas when the cooking gas oven 200 is in a substantially steady state after the latter half of preheating. The solid arrows indicate the flow of combustion gas generated and exhausted by combustion. External air and fuel are drawn into the burner 23 and combusted in the furnace chamber chimney 34. The high-temperature combustion gases generated by combustion ascend through the furnace chamber chimney 34. Because the upper opening 35 is approximately horizontal, the rising high-temperature combustion gases change direction slightly horizontally and flow from the upper opening 35 toward the center of the furnace chamber 16. The extremely high-temperature combustion gases rising near the tip of the flame 25 mix with the surrounding combustion gases as they change direction slightly horizontally. When they exit the furnace chamber chimney 34 through the upper opening 35, they are further mixed with the surrounding combustion gases, significantly reducing the temperature of the extremely high-temperature combustion gases. The temperature of the combustion gas coming out of the upper end opening 35 is higher than that of the surrounding combustion gas, so it rises, accumulates in the upper part of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then falls. The combustion gas that falls near the exhaust port 18 is drawn into the exhaust port 18 and exhausted.

[0032] The dashed arrows indicate the convection of combustion gas circulating within the furnace chamber 16. As the high-temperature combustion gas rises through the furnace chamber chimney passage 34, the combustion gas above the hearth 15 is drawn into the lower opening 33. This drawn-in combustion gas mixes with the high-temperature combustion gas generated by combustion and rises through the furnace chamber chimney passage 34. The rising combustion gas changes direction slightly horizontally and exits through the upper opening 35 toward the center of the furnace chamber 16, then rises again, stagnates at the top of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then descends. Combustion gas descending near the inlet 11 is caught up in the convection current occurring at the inlet 11. Combustion gas descending away from the exhaust port 18 and inlet 11 descends to the vicinity of the hearth 15, flows toward the lower opening 33, where the surface temperature of the hearth 15 is higher, and is then drawn into the lower opening 33. This convection of the combustion gas circulating within the furnace chamber 16 is called secondary chimney convection.

[0033] Figure 6 is a top-down cross-sectional view of a section just above the hearth 15 of a gas cooking oven 200. The dashed arrow indicates the secondary chimney convection just above the hearth 15. The velocity of the secondary chimney convection near the lower opening 33 above the hearth 15 increases the closer to the lower opening 33, is greatest at the center of the lower opening 33, and exhibits a radial pattern that decreases toward the edges. Therefore, the hearth 15 is heated radially by convective heat transfer between the hearth 15 and the secondary chimney convection at a rate similar to that of the secondary chimney convection. Furthermore, because the secondary chimney convection flows directly above the hearth 15, the hearth 15 near the lower opening 33 is likely to be overheated by convective heat transfer.

[0034] Because the gas cooking oven 100 has a burner 83 with excessive heat, it is difficult to build an optimal gas cooking oven. Therefore, we build an optimal gas cooking oven based on a furnace chamber chimney body 32 that is compatible with a burner 23 with appropriate heat, in which the food is cooked with maximum thermal efficiency, the food is cooked well, and the cooking progress can be seen during cooking. To achieve this, the first requirement is to specify the shape of the furnace chamber chimney body 32 that provides the highest thermal efficiency, the second requirement is to specify a means for achieving good cooking progress, and the third requirement is to specify a means for illuminating the food.

[0035] First requirement: Shape of the chimney body 32 inside the furnace chamber The thermal efficiency of the gas cooking oven 200 depends on the shape of the furnace chamber chimney body 32. When the heating power of the burner 23 is constant, if the speed of the second chimney convection increases in response to a change in the shape of the furnace chamber chimney body 32, more low-temperature combustion gas from the bottom of the furnace chamber 16 is drawn in, and as a result, higher-temperature combustion gas flows into the bottom of the furnace chamber 16, raising the temperature of the combustion gas at the bottom of the furnace chamber 16. At the same time, the high-temperature combustion gas generated by combustion mixes with the more low-temperature combustion gas drawn in from the bottom of the furnace chamber 16, lowering the temperature of the combustion gas ascending the furnace chamber chimney passage 34 and the temperature of the combustion gas at the top of the furnace chamber 16. Because the furnace chamber temperature fluctuates in conjunction with the temperature of the combustion gas at the bottom of the furnace chamber 16, an increase in the speed of the second chimney convection increases the furnace chamber temperature and lowers the temperature of the combustion gas at the top of the furnace chamber 16. Furthermore, when the speed of the second chimney convection decreases, the furnace chamber temperature decreases and the temperature of the combustion gas at the top of the furnace chamber 16 increases. This means that the furnace chamber temperature is highest when the speed of the second chimney convection is maximum. Since the thermal efficiency is highest when the furnace chamber temperature is highest for a given heating power, the shape of the furnace chamber chimney body 32 that results in the highest furnace chamber temperature is the optimal shape for the furnace chamber chimney body 32.

[0036] The cross section of the chimney body 32 inside the furnace chamber is a rectangle, and the length of the short side of the rectangle is the width and the length of the long side is the height. First, the maximum width and maximum height of the horizontal cross section of the flame 25 are measured, and these measurements are the maximum width and maximum height of the flame, respectively. (1) Optimum length of chimney body 32 inside the furnace chamber The longer the furnace chamber chimney main body 32, the greater the chimney effect, so the optimum main body length is the length of the furnace chamber chimney main body 32 that results in a predetermined distance between the furnace chamber chimney main body 32 and the furnace wall of the kiln main body 13. Here, the predetermined distance is, for example, about 1 cm, and means a distance that allows the furnace chamber chimney main body 32 to be installed even if there are manufacturing or installation errors in the kiln main body 13 and the furnace chamber chimney main body 32.

[0037] (2) Optimal width and vertical width of the chimney body 32 in the furnace chamber If the cross-sectional area of ​​the furnace chamber chimney body 32 (assuming the aspect ratio is appropriate) is too small, combustion is hindered, the heat generated by combustion is reduced, and the speed of the second chimney convection through the lower opening 33 is slowed. On the other hand, if the cross-sectional area of ​​the furnace chamber chimney body 32 is too large, convection of combustion gas occurs in the furnace chamber chimney passage 34, slowing the speed of the second chimney convection through the lower opening 33. The optimal body width and optimal body length are intermediate and can be determined through experimentation. For example, three to five different widths and lengths of the furnace chamber chimney body 32 are fabricated, and the optimal size of the furnace chamber chimney body corresponding to the highest furnace temperature is determined through experimentation. In other words, the optimal body width and optimal body length refer to the optimal size of the furnace chamber chimney body 32 that maximizes the chimney effect when a flame 25 is generated within the furnace chamber chimney body 32.

[0038] First, a furnace chamber chimney body is created whose length is the optimal body length, whose width is the maximum flame width, whose vertical width is the maximum flame vertical width, whose lower opening width is the maximum flame vertical width, whose lower opening height is half of the maximum flame width, whose upper opening width is the maximum flame vertical width, and whose upper opening height is the maximum flame width.Further, a plurality of furnace chamber chimney bodies are created whose length is the optimal body length, whose width is a width different from the maximum flame width, whose vertical width is a vertical width different from the maximum flame vertical width, whose lower opening and upper opening widths are the vertical width of the furnace chamber chimney body to be created, whose lower opening height is half the width of the furnace chamber chimney body to be created, and whose upper opening height is the width of the furnace chamber chimney body to be created.

[0039] The cooking gas kiln 200 with the furnace chamber chimney body 32 removed is preheated, and the furnace chamber temperature is adjusted by adjusting the injection amount to a predetermined temperature (e.g., 50°C) lower than the furnace chamber temperature during a specified cooking session. The injection amount and furnace chamber temperature when the furnace chamber temperature reaches a state where the change over time is very small (quasi-steady state) are recorded as the first injection amount and the conventional furnace chamber temperature, respectively. Next, the cooking gas kiln 200 with one of the prepared furnace chamber chimney bodies installed is preheated, and the furnace chamber temperature when the first injection amount is used for the quasi-steady state is recorded. Similarly, the furnace chamber temperatures when the first injection amount is used for the other prepared furnace chamber chimney bodies are recorded. The width and length of the furnace chamber chimney body corresponding to the maximum value of the recorded furnace chamber temperatures are the optimal body width and length of the furnace chamber chimney body 32, respectively. Note that the increase in furnace chamber temperature from the conventional furnace chamber temperature indicates an improvement in the thermal efficiency of the cooking gas kiln 200 using the furnace chamber chimney body 32.

[0040] (3) Width and height of the lower opening 33 The width of the lower opening 33 is the optimum body vertical width, and the height of the lower opening 33 is the optimum body horizontal width.

[0041] (4) Width and height of the top opening 35 The width of the upper end opening 35 is the optimum vertical width of the main body, and the height of the upper end opening 35 is the optimum horizontal width of the main body.

[0042] Second requirement: doneness To properly brown the food, it is necessary to brown the food primarily through convective heat transfer in a short time, brown the food evenly across a wide periphery, and prevent the food from overcooking at its outer edge. To achieve this, the width of the second chimney convection must be expanded to the width of the food, and the speed of the second chimney convection must be kept approximately constant around the food's periphery. Furthermore, to prevent excessive overcooking due to convective heat transfer at the food's outer edge, the second chimney convection must be directed slightly above the hearth 15. Note that if the width of the lower opening 33 is equal to the width of the food, there is no need to change the width of the second chimney convection. Furthermore, if the width of the lower opening 33 is larger than the width of the food, it is preferable to reduce the width of the second chimney convection.

[0043] Third requirement: lighting of food In order to observe the doneness of the food being cooked, it is necessary to illuminate the food with the light of the flame 25.

[0044] FIG. 7 is a perspective view showing one embodiment of a furnace chamber chimney satisfying the above requirements. The furnace chamber chimney 41 comprises a furnace chamber chimney main body 42, an extension passage forming member 51, and a flow rate adjusting member 55. The length of the furnace chamber chimney main body 42 is the optimal main body length, the width is the optimal main body width, and the height is the optimal main body vertical width. The width of the lower opening 43 is the optimal main body vertical width, and the height of the lower opening 43 is the optimal main body horizontal width. The width of the upper opening 45 is the optimal main body vertical width, and the height of the upper opening 45 is the optimal main body horizontal width. A light passage 46 necessary for illuminating food to be cooked is formed in the center of the side surface of the furnace chamber chimney main body 42 between the lower opening 43 and the upper opening 45. The light passage 46 may be one or more holes formed in the furnace chamber chimney main body 42, but the holes are preferably covered with transparent heat-resistant glass or the like.

[0045] The extension passage forming member 51 has an extension passage inlet 52 at one end that opens substantially horizontally, and the other end that communicates with the lower opening 43. The width of the extension passage inlet 52 is a predetermined inlet width (e.g., the width of the food being cooked), and its height is a predetermined inlet height (e.g., 1 cm). The extension passage inlet 52 is located at a predetermined height (e.g., 2 cm) above the hearth 15. The outer angle between the side of the extension passage forming member 51 and the surface of the lower opening 43 is a predetermined angle (e.g., 40 degrees). The extension passage forming member 51 extends the chimney passage 44 within the furnace chamber, and by locating the extension passage inlet 52 near the food being cooked, the speed of convection of combustion gases above the food being cooked is increased, allowing the food to be cooked more intensely through convective heat transfer. Locating the extension passage inlet 52 above the hearth reduces the risk of the outer edges of the food being cooked being overcooked. Furthermore, when the width of the lower opening 43 is equal to the width of the food to be cooked, the width of the extension passage entrance 52 is equal to the width of the lower opening 43, and when the width of the lower opening 43 is larger than the width of the food to be cooked, it is preferable that the width of the extension passage entrance 52 is smaller than the width of the lower opening 43.

[0046] A flow velocity adjusting member 55, which adjusts the velocity of combustion gas within the extension passage 53, is disposed in the extension passage 53 to uniformly grill the outer periphery of the food. The flow velocity adjusting member 55 includes a pair of side partition plates 56 and a pair of central partition plates 57. The pair of side partition plates 56 are disposed substantially parallel to both side surfaces of the extension passage forming member 51. One of the pair of central partition plates 57 is disposed so as to approach one of the pair of side partition plates 56 from the center of the extension passage inlet 52 toward the lower opening 43, and the other of the pair of central partition plates 57 is disposed so as to approach the other of the pair of side partition plates 56 from the center of the extension passage inlet 52 toward the lower opening 43. By adjusting the distance between the pair of side partition plates 56 and the side surfaces of the extension passage forming member 51 or by adjusting the length or interior angle of the pair of central partition plates 57, the velocity of combustion gas drawn into both ends of the extension passage inlet 52 is made greater than the velocity of combustion gas drawn into the center of the extension passage inlet 52.

[0047] The extension passage forming body 51 and the flow rate adjusting body 55 are highly flexible structures. It is preferable to create a plurality of extension passage forming bodies and flow rate adjusting bodies of different shapes, grill the food on each of the extension passage forming bodies and flow rate adjusting bodies, evaluate the degree of grilling, and select the extension passage forming body and flow rate adjusting body that correspond to the best degree of grilling as the optimal extension passage forming body and flow rate adjusting body.

[0048] FIG. 8 is a cross-sectional view of a gas-fired cooking kiln 300 equipped with a furnace chamber chimney 41. The gas-fired cooking kiln 300 replaces the furnace chamber chimney main body 32 of the gas-fired cooking kiln 200 with the furnace chamber chimney 41. For clarity, the flow rate adjuster 55 is omitted from FIG. 8 . The solid arrows indicate the flow of exhausted combustion gas generated by the combustion of the external air-fuel mixture during the substantially steady state after the latter half of preheating. The flow of this combustion gas is almost identical to the solid arrows in FIG. 5 . The dashed arrows indicate the third chimney convection current circulating within the furnace chamber 16, generated by the furnace chamber chimney 41. As the high-temperature combustion gas rises in the furnace chamber chimney passage 44, the combustion gas near the extension passage inlet 52 is drawn into the extension passage inlet 52. The drawn-in combustion gas passes through the extension passage 53, mixes with the high-temperature combustion gas from the chimney passage 44 inside the furnace chamber, rises, then changes direction slightly horizontally and flows from the upper end opening 45 toward the center of the furnace chamber 16, then rises again, stagnates at the top of the furnace chamber 16, is cooled by the furnace wall of the kiln body 13, and then falls. Combustion gas that descends away from the exhaust port 18 and inlet 11 falls to near the hearth 15. Because the surface temperature of the hearth 15 is higher closer to the extension passage inlet 52, the combustion gas that descends to near the hearth 15 flows toward the extension passage inlet 52 and is drawn into it. Because the extension passage inlet 52 is located slightly above the hearth 15, the third chimney convection drawn into the extension passage inlet 52 flows slightly above the hearth 15.

[0049] Figure 9 is a top-down horizontal cross-sectional view of the gas-fired cooking oven 300, taken near the vertical center of the extension passage inlet 52. The food area 28 is smaller than the food area 27 due to the placement of the chimney 41 inside the furnace chamber. The dashed arrows indicate the convection flow in the third chimney slightly above the hearth 15 during a substantially steady state after the latter half of preheating. The velocity of the third chimney convection flow drawn into the extension passage inlet 52 at the center is slower than that at both ends of the inlet due to the flow rate regulator 55. Furthermore, the velocity of the third chimney convection flow decreases the further away from the extension passage inlet 52. This ensures that the outer edges of the food facing the extension passage inlet 52 are cooked relatively evenly. Furthermore, because the third chimney convection flow flows slightly above the hearth 15, the food is less likely to be overcooked at its outer edges. Therefore, in the cooking gas oven 300, the food is cooked efficiently in a short time mainly by convection heat transfer, and the wide outer periphery of the food is cooked almost evenly, making it difficult for the outer edge of the food to be overcooked. In other words, in the cooking gas oven 300, the food is cooked well in a short time, just like in a stone oven.

[0050] Therefore, based on the furnace chamber chimney main body 32, a cooking gas kiln 300 can be constructed in which food is cooked to a good degree in a short time, as if cooked in a stone oven, and has higher thermal efficiency than a stone oven. Furthermore, based on the furnace chamber chimney main body 62, a light passage is first formed in the furnace chamber chimney main body 62, and an extension passage forming body communicating with the lower opening 63 and a flow rate adjusting body matching the extension passage formed by the extension passage forming body are created, thereby constructing a furnace chamber chimney. Then, by placing this furnace chamber chimney in a cooking gas kiln 800, a cooking gas kiln can be constructed in which food is cooked to a good degree in a short time, as if cooked in a stone oven, and has higher thermal efficiency than a stone oven. Furthermore, a contact avoidance plate is provided between the upper end opening 65 and the kiln main body 13 to prevent the extremely high-temperature combustion gas rising near the tip of the flame 85 from coming into contact with the furnace wall of the kiln main body 13. The contact avoidance plate allows the rising extremely hot combustion gases to mix with the surrounding combustion gases, significantly reducing their temperature, thereby further increasing the thermal efficiency of the gas cooking oven.

[0051] In the gas cooking oven 300, as shown in Figure 9, one end of the extension passage inlet 52 is close to the inlet 11, so strong convection occurs near the inlet 11, which lowers the temperature of the combustion gas, particularly near the inlet 11 at the bottom of the furnace chamber 16, causing the food to be cooked weakly near the inlet 11. In other words, the food is cooked moderately near the extension passage inlet 52, weakly on the opposite side, and most weakly near the inlet 11. Because the food is not cooked asymmetrically, it is difficult to cook the food evenly evenly when cooking it again.

[0052] Figure 10 is a cross-sectional view similar to Figure 9 of a cooking gas kiln 400 according to another embodiment. In this figure, the temperature sensor 75 and exhaust port 76 located above the hearth 71 are indicated by dashed lines. The cooking gas kiln 400 is similar to the cooking gas kiln 300, except that the inlet 11 is fixed, while the hearth opening 17, burner 23, furnace chamber chimney 41, exhaust port 76, and chimney 12 are rotated 90 degrees counterclockwise around the center of the furnace chamber. Therefore, the flow of combustion gas generated by the combustion of a mixture of external air and fuel and exhausted in the cooking gas kiln 400 is almost identical to the flow of combustion gas in the cooking gas kiln 300 rotated 90 degrees counterclockwise around the center of the furnace chamber. In addition, in the cooking gas oven 400, the convection of combustion gas circulating within the furnace chamber (fourth chimney convection) generated by the furnace chamber chimney 41 is almost the same as the third chimney convection rotated 90 degrees counterclockwise around the center of the furnace chamber 16. However, the flow of the fourth chimney convection near the exhaust port 76 and the inlet 72 is different from the flow of the third chimney convection.

[0053] The dashed arrows in Figure 10 indicate the convection currents in the fourth chimney just above the hearth 71 during a substantially steady state after the latter half of preheating. The dashed arrows are essentially the same as the dashed arrows in Figure 9 rotated 90 degrees counterclockwise around the center of the furnace chamber. In the cooking gas kiln 400, the strong convection currents near the inlet 72 are symmetrical in front view with respect to the convection currents in the fourth chimney toward the extension passage inlet 52. The cooking gas kiln 400 is symmetrical, and if the food to be cooked is a thin, disc-shaped object placed symmetrically on the hearth 71 as viewed from the front, the food will be cooked symmetrically. By rotating the food 180 degrees and cooking it again, the entire food will be cooked evenly. [Explanation of symbols]

[0054] 11 Entrance 12 Chimney 13 Kiln body 14 Exhaust passage 15 Hearth 16 Furnace room 17 Hearth opening 18 Exhaust port 21 Controller 22 Temperature sensor 23 Burner 24 Flame hole 25 Flame 26 Cooked items 27,28 Cooking area 41 Furnace chamber chimney 32, 42, 62 Chimney body inside furnace chamber 33, 43, 63 Lower opening 34, 44, 64 Chimney passage in furnace chamber 35,45,65 Top opening 46 Light passage section 51 Extension passage forming body 52 Extension passage entrance 53 Extension passage 55 Flow rate adjustment body 56 Pair of side dividers 57 Pair of center dividers 71 Hearth 72 Entrance 73 Kiln body 74 Cooked food area 75 Temperature Sensor 76 Exhaust port 77 Hearth opening 81 Hearth 82 Hearth opening 83 Burner 84 Flame hole 85 Flame 100,200,300,400,800 Gas cooking oven

Claims

1. The hearth and a kiln body forming a furnace chamber having an inlet on the hearth; a burner that generates a flame in the furnace chamber, A cooking gas kiln in which the food to be cooked is placed in an area of ​​the food to be cooked on the upper surface of the hearth in the furnace chamber, The furnace chamber chimney body further includes a cylindrical furnace chamber chimney body having an upper end and a lower end open and a lower opening at a lower part of the side surface of the chimney body, The chimney body within the furnace chamber surrounds the flame generated by the burner, and is positioned so that its lower end is in contact with or close to the hearth and its lower opening faces the area of ​​the food to be cooked.

2. 2. The cooking gas stove according to claim 1, wherein the chimney body in the furnace chamber has a light passing portion on a side surface of the chimney above the lower opening through which light passes.

3. 3. A cooking gas oven as claimed in claim 1, further comprising an extension passage forming body that forms an extension passage, one end of which is an extension passage inlet that opens substantially horizontally toward the area to be cooked and the other end of which is connected to the lower opening.

4. 4. The gas cooking oven according to claim 3, wherein the extension passage inlet is located above the hearth.

5. 4. The gas cooking oven according to claim 3, further comprising a flow rate adjusting member disposed in the extension passage for adjusting the velocity of the combustion gas drawn into the extension passage inlet in the width direction.

6. 6. The cooking gas kiln according to claim 5, wherein the flow rate adjusting body comprises a pair of side partition plates arranged substantially parallel to both sides of the extension passage, and a pair of central partition plates, one of which is arranged so as to approach one of the pair of side partition plates from the center of the extension passage inlet toward the lower opening, and the other of which is arranged so as to approach the other of the pair of side partition plates from the center of the extension passage inlet toward the lower opening.

Images