Natural convection wick type kerosene stove

Abstract

This invention provides a natural convection type wick-type kerosene stove that reliably burns kerosene vapor generated from the wick even during low-burning periods such as ignition and extinguishing, thereby reducing the release of unburned kerosene vapor into the room and preventing unpleasant irritating odors, while also enabling continuous and stable combustion. [Solution] The present invention provides a natural convection wick-type kerosene stove 1 comprising, in order from the inside out, a cylindrical inner flame tube 31, a cylindrical outer flame tube 32, and a cylindrical outer cylinder 33, and a wick 34 is placed in the annular space formed between the inner flame tube 31 and the outer flame tube 32 to form a combustion space C. A mixing promotion section M consisting of a plurality of protrusions is formed on the surface of the outer flame tube 32, and the plurality of protrusions are inclined protrusions M1 to M5 that are inclined with respect to the horizontal plane, and a plurality of inclined protrusions M1 to M5 are arranged in parallel in the circumferential direction of the outer flame tube 32.

Description

Technical Field

[0001] The present invention relates to a natural convection wick type kerosene stove, and particularly to a technique that can surely burn kerosene vapor generated from a wick even during weak combustion such as ignition and extinguishing, reduce the emission of unburned kerosene vapor into the room, prevent an unpleasant irritating odor, and enable continuous and stable combustion.

Background Art

[0002] Conventional natural convection wick type kerosene stoves include a cylindrical inner flame cylinder, a cylindrical outer flame cylinder, and a cylindrical outer cylinder in order from the inside. A wick is arranged in an annular space formed between the inner flame cylinder and the outer flame cylinder and functions as a combustion chamber. The wick is installed so as to be vertically movable near the bottom of the combustion chamber, and its lower end is impregnated with kerosene stored in a kerosene tank. At the time of ignition, the wick is raised so as to be located upward and projected into the combustion chamber, and ignition is performed with a match, a lighter, or an ignition heater (not shown) to start combustion.

[0003] When the wick is lit, an upward airflow of combustion gas is generated in the combustion chamber as the kerosene burns. Combustion air flows into the combustion chamber by natural convection through a plurality of ventilation holes formed on the entire peripheral surfaces of the inner flame cylinder and the outer flame cylinder, penetrates the kerosene impregnated in the wick, and further burns the kerosene. As the kerosene burns, the temperature of the combustion chamber gradually rises, and the kerosene impregnated in the wick evaporates into the combustion chamber as kerosene vapor. The kerosene vapor evaporated from the wick is burned by the combustion air flowing in through the ventilation holes. As the kerosene vapor burns, the temperature in the combustion chamber further rises, the flow rate of the combustion air flowing in through the ventilation holes and the amount of kerosene vapor evaporated from the wick increase, and the combustion of the kerosene vapor gradually becomes more active, and the combustion becomes stable after a certain period of time.

[0004] During the process from ignition to combustion stabilization, as the combustion of the generated kerosene vapor gradually becomes more active, the velocity of the rising airflow of combustion gases passing through the combustion chamber increases before the temperature inside the combustion chamber has risen sufficiently. As a result, unburned kerosene vapor is released from the combustion tube into the room until combustion stabilizes. This is also due to the uneven concentration of suspended kerosene vapor in the inner flame tube, outer flame tube, and the narrow area between them.

[0005] In other words, when ignited, the kerosene vapor emitted from the wick, which is approximately 2.5 mm thick, exhibits irregularities in the amount and direction of emission depending on the wick tip shape, wick side, height, material, and processing. As a result, kerosene vapor particles float unevenly in the combustion chamber space, which is approximately 14 mm wide and 100 mm long, especially from the bottom to the middle of the chamber. After ignition, most of these particles receive oxygen from the air holes provided on the sides of the outer and inner flame tubes, and undergo an oxidation-reduction reaction (combustion) from diffusion combustion to premixed combustion, increasing the combustion speed and rising airflow speed, causing the premixed flame to rise.

[0006] However, because the kerosene vapor particles suspended on the sides of the outer and inner flame tubes, as well as in the intermediate section between them, have an uneven concentration distribution, some of the unburned vapor is pulled by the rising airflow of the premixed flame and combustion gases during the process leading to premixed combustion, and is released above the exhaust port of the combustion tube, which is the cause of the unpleasant pungent odor.

[0007] On the other hand, during fire extinguishing, as the wick descends, the combustion transitions from premixed combustion to diffusion combustion. This gradually reduces the amount of kerosene vapor particles suspended in the combustion chamber, and the fire is finally extinguished after about 4 to 5 minutes. However, during this time, kerosene vapor particles continue to be emitted from the wick, which is heated to a high temperature. The emission of these unburned kerosene vapor particles is particularly noticeable during fire extinguishing and is a cause of the unpleasant, pungent odor.

[0008] Thus, the release of unburned kerosene vapor into the room is the cause of an unpleasant pungent odor. Specifically, the main exhaust components generated during combustion in a natural convection wick-type kerosene stove include (1) carbon dioxide, (2) carbon monoxide, (3) water vapor, (4) nitrogen dioxide, (5) unburned hydrocarbons, (6) sulfur oxides, and (7) particulate matter. The unpleasant pungent odor generated during combustion is a complex odor derived from a combination of these components, and among these, (5) unburned hydrocarbons are particularly associated with unpleasant odors. Unburned hydrocarbons are a general term for various components, but among them, four highly volatile substances have been identified as the cause of unpleasant odors generated during ignition, and six highly volatile substances have been identified as the cause of unpleasant odors generated during extinguishing.

[0009] The autoignition points of these odor-causing components range from approximately 207°C to 480°C during ignition and from approximately 207°C to 505°C during extinguishing. On the other hand, kerosene has an ignition point of approximately 250°C and a flash point of approximately 40°C, meaning that it generates heat of over 250°C immediately upon ignition, and the temperature inside the combustion chamber rises to approximately 800°C in the short time elapsed by the oxidation-reduction reaction. Therefore, if all of these components can be burned inside the combustion chamber, it is possible to eliminate the source of the unpleasant odor.

[0010] In conventional natural convection wick-type kerosene stoves, a secondary combustion chamber has been installed above the combustion cylinder to completely burn the unburned hydrocarbons that cause such pungent odors. This chamber is then used for re-combustion or catalytic combustion to achieve complete combustion of the unburned kerosene vapors. However, installing a secondary combustion chamber above the combustion cylinder increases the overall height of the stove and complicates the overall structure of the device, which is undesirable.

[0011] On the other hand, as a method to achieve complete combustion within the combustion chamber without providing a separate secondary combustion chamber and to suppress the emission of unburned vapors, a technique has been proposed in which a swirling flow is imparted to the flow of combustion gases and combustion air inside the combustion chamber in order to balance the combustion speed of kerosene with the rising airflow speed, thereby keeping the kerosene vapor in the combustion chamber for as long as possible, while simultaneously rapidly transitioning from diffusion combustion to premixed combustion (Patent Document 1).

[0012] According to the technology described in Patent Document 1, in order to impart a swirling flow to the combustion air, spiral protrusions are formed on the circumferential surface of the outer flame tube, thereby promoting the retention of kerosene vapor and its mixing with the combustion air. However, simply forming spiral protrusions is insufficient in terms of mixing with the combustion air, although it is possible to retain unburned kerosene vapor in the combustion tube, and the problem of unburned kerosene vapor being released from the combustion tube still persists. Furthermore, if spiral protrusions are formed over the entire circumferential surface of the outer flame tube, the swirling flow becomes too strong, causing the flame to extend upwards due to the swirling, and the flame to fly out from the red-hot net at the top of the combustion tube, preventing proper heat transfer to the red-hot net and thus impairing the effectiveness of the stove. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 58-064411 [Overview of the project] [Problems that the invention aims to solve]

[0014] This invention has been made in view of the above problems, and aims to provide a natural convection type wick kerosene stove that can reliably burn kerosene vapor generated from the wick even during low combustion, such as when ignition or extinguishing, thereby reducing the release of unburned kerosene vapor into the room and preventing unpleasant irritating odors, while also enabling continuous and stable combustion. [Means for solving the problem]

[0015] As a result of diligent research, the inventors of the present invention discovered that by arranging multiple outwardly projecting inclined protrusions in a circumferential direction on the surface of the outer flame tube, kerosene vapor can be swirled within the combustion chamber and efficiently mixed with combustion air, thereby suppressing the emission of unburned kerosene vapor, leading to the present invention.

[0016] The present invention provides the following solutions.

[0017] The first characteristic of the natural convection wick type kerosene stove is a natural convection wick type kerosene stove which comprises, from the inside out, a cylindrical inner flame tube, a cylindrical outer flame tube, and a cylindrical outer cylinder, and a wick is placed in the annular space formed between the inner flame tube and the outer flame tube to form a combustion space. A mixing promotion section consisting of multiple protrusions is formed on the surface of the outer flame tube, and the multiple protrusions are inclined protrusions that are inclined with respect to the horizontal plane, and multiple inclined protrusions are arranged in parallel in the circumferential direction of the outer flame tube.

[0018] According to the invention relating to the first feature, since multiple inclined protrusions are arranged in a circumferential direction and are inclined with respect to the horizontal plane, a swirling flow of combustion air and unburned kerosene vapor is generated at multiple locations in the circumferential direction at the same height. As a result of the generation of the swirling flow, the upward velocity of the combustion air and unburned kerosene vapor is reduced, and in the region above the upper end of the inclined protrusions, the swirling flows mix with each other and rise through the combustion space over time while swirling, thus suppressing the release of unburned kerosene vapor. Furthermore, since the swirling flows formed at multiple locations by the multiple inclined protrusions mix with each other, mixing is promoted more effectively than when a single swirling flow is formed or when rising airflows are mixed, allowing for more reliable combustion of unburned kerosene vapor.

[0019] The natural convection wick type oil stove relating to the second feature is a natural convection wick type oil stove relating to the first feature, wherein the multiple inclined protrusions are arranged side by side with a predetermined interval between them in the width direction.

[0020] According to the invention related to the second feature, since the adjacent inclined protrusions are arranged at a predetermined interval in the width direction, a swirling flow along the angle at which the inclined protrusions incline with respect to the horizontal plane collides with an upward flow flowing between the inclined protrusions. Therefore, compared with the case where only a plurality of swirling flows are simply formed, the mixing of unburned kerosene vapor and combustion air can be promoted by the collision between the swirling flow and the upward flow, and the unburned kerosene vapor can be burned more reliably.

[0021] The natural convection type wick type kerosene stove according to the third feature is the natural convection type wick type kerosene stove according to the first feature, wherein a plurality of inclined protrusions are provided in multiple stages in the height direction.

[0022] According to the invention related to the third feature, since the inclined protrusions are formed in multiple stages in the height direction, a swirling flow can be formed in the combustion air rising between the outer cylinder and the outer flame cylinder multiple times, and the unburned kerosene vapor that could not be burned by a single swirling flow can be surely burned.

[0023] The natural convection type wick type kerosene stove according to the fourth feature is the natural convection type wick type kerosene stove according to the third feature, wherein the multiple-stage inclined protrusions are formed by a combination of a lower stage with a large angle with respect to the horizontal plane and an upper stage with a small angle with respect to the horizontal plane.

[0024] According to the invention related to the fourth feature, first, inclined protrusions with an inclination angle close to the upward flow, that is, inclined protrusions with a large inclination angle with respect to the horizontal plane, are arranged in the lower stage to surely generate swirling, and then, inclined protrusions with a small inclination angle are arranged to generate a swirling flow at a desired angle. By arranging the two-stage inclined protrusions with different angles in this way, a swirling flow at a desired angle can be surely generated, the combustion field can be kept in a uniform state, the retention and mixing of combustion vapor can be promoted, and the dissipation of unburned kerosene vapor can be suppressed.

[0025] The natural convection wick type kerosene stove according to the fifth feature is the natural convection wick type kerosene stove according to the fourth feature, and two sets of combinations of the upper inclined projections and the lower inclined projections are provided in the height direction.

[0026] According to the invention according to the fifth feature, even when combustion progresses and the combustion gas becomes high temperature, the swirling flow generated by the combination of the lower inclined projections can be further developed by the combination of the upper inclined projections. It is possible to surely impart a swirling flow to the high-temperature combustion gas with a large rising speed, ensure the residence time, promote the mixing of the combustion gas and the combustion air, and surely burn the unburned kerosene vapor.

[0027] The natural convection wick type kerosene stove according to the sixth feature is the natural convection wick type kerosene stove according to any one of the first to fifth features, and a plurality of inclined projections project outward from the surface of the outer flame cylinder.

[0028] According to the invention according to the sixth feature, since all of the plurality of inclined projections project outward from the surface of the outer flame cylinder, it is possible to form a swirling flow and promote mixing while securing an appropriate amount of combustion air without narrowing the volume of the combustion space.

[0029] The natural convection wick type kerosene stove according to the seventh feature is the natural convection wick type kerosene stove according to any one of the first to fifth features, and as a mixing promotion part, an annular rectifying groove continuous in the circumferential direction is further provided above the inclined projection.

[0030] According to the invention according to the seventh feature, since an annular rectifying groove continuous in the circumferential direction is provided above the inclined projection, the combustion gas is temporarily held inside the annular rectifying groove to promote the mixing of the unburned kerosene vapor and the combustion air. At the same time, it is possible to rectify the flow velocity distribution of the combustion gas discharged from the combustion space so as to be uniform in the circumferential direction, and the unburned kerosene vapor can be completely burned.

Effects of the Invention

[0031] According to the present invention, even during low combustion periods such as ignition and extinguishing, it is possible to provide a natural convection type wick kerosene stove that reliably burns the kerosene vapor generated from the wick, reducing the release of unburned kerosene vapor into the room and preventing unpleasant irritating odors, while also enabling continuous and stable combustion. [Brief explanation of the drawing]

[0032] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration of the natural convection wick type oil stove 1 according to this embodiment. [Figure 2] Figure 2 is a schematic diagram showing the combustion heating element 30 of the natural convection wick type oil stove 1 according to this embodiment. [Figure 3] Figure 3 is a magnified view of the mixing promotion section M of the combustion heating element 30. [Figure 4] Figure 4 is a partially enlarged cross-sectional view of the mixing promotion section M of the combustion heating element 30. [Modes for carrying out the invention]

[0033] The following describes embodiments for carrying out the present invention with reference to the figures. However, this is merely an example, and the technical scope of the present invention is not limited thereto.

[0034] [Overall configuration of the natural convection wick-type kerosene stove 1] The overall configuration of the natural convection wick type oil stove 1 according to this embodiment will be explained using Figure 1.

[0035] As shown in Figure 1, the natural convection wick-type kerosene stove 1 of this embodiment comprises a wick raising / lowering device 10, a kerosene tank 20, a combustion heating element 30, a red-hot net 40, a protective fence / support 50, and a top plate 60.

[0036] In the present invention, the natural convection wick-type kerosene stove 1 has a wick 34 attached to a wick raising / lowering device 10, the lower part of which is impregnated with kerosene fuel stored in a kerosene tank 20, and the kerosene reaches the tip of the wick 34 by capillary action, igniting the fuel impregnated in the wick 34 and causing combustion inside the combustion heating element 30. The red-hot net 40 is installed at the upper end of the combustion heating element 30 and is a dome-shaped mesh member made of iron-chromium, which glows red and emits radiant heat in conjunction with combustion in the combustion heating element 30. The protective fence and support posts 50 are a fence and multiple support posts that protect the combustion heating element 30 and the red-hot net 40. The top plate 50 is made of a metal plate that covers the red-hot net 40 from above.

[0037] [Detailed structure of combustion heating element 30] Next, the detailed structure of the combustion heating element 30 of the natural convection wick type oil stove 1 according to this embodiment will be described using Figures 2 to 4. Figure 2 is a schematic diagram showing the combustion heating element 30 of the natural convection wick type oil stove according to this embodiment, Figure 3 is a partially enlarged view of the mixing promotion section M of the combustion heating element 30, and Figure 4 is a partially enlarged cross-sectional view of the mixing promotion section M of the combustion heating element 30.

[0038] The combustion heating element 30 comprises, from the inside out, a cylindrical inner flame tube 31, an outer flame tube 32 which is larger in diameter than the inner flame tube 31 and has a cylindrical shape, and an outer cylinder 33 which is larger in diameter than the outer flame tube 32 and has a cylindrical shape, arranged around a vertical axis. A wick 34 is placed in the annular space formed between the inner flame tube 31 and the outer flame tube 32, and a combustion space 35 is formed in the annular cross-section space between the inner flame tube 31 and the outer flame tube 32. The combustion space 35, which has an annular cross-section, is approximately 14 mm wide and approximately 100 mm high. Multiple ventilation holes 31a are regularly formed on the entire surface of the inner flame tube 31 in both the height and circumferential directions, and combustion air flows in from the inside of the inner flame tube 31 towards the combustion space 35. Furthermore, multiple ventilation holes 32a are regularly formed on the entire surface of the outer flame tube 32 in both the height and circumferential directions, allowing combustion air to flow from the region between the outer flame tube 32 and the outer cylinder 33 into the combustion space 35. The inner flame tube 31 and outer flame tube 32, which are equipped with multiple regularly formed ventilation holes 31a and 32a, are formed, for example, by processing perforated metal into a cylindrical shape. The outer cylinder 33 does not have ventilation holes on its circumferential surface, but an annular outer cylinder air inlet 33a is formed between the lower end of the cylindrically formed outer cylinder 33 and the lower end of the cylindrically formed outer flame tube 32.

[0039] The mixing promotion section M consists of a plurality of protrusions formed to project outward from the surface of the outer flame tube 32, and is intended to decelerate the vertically upward flow velocity of the rising airflow of unburned kerosene vapor and promote mixing with combustion air. The plurality of protrusions forming the mixing promotion section M include a plurality of inclined protrusions M1, M2, M3, M4, and M5 that are inclined in the same direction with respect to the horizontal plane, and each of the inclined protrusions M1 to M5 is arranged in parallel in the circumferential direction of the outer flame tube 32. The mixing promotion section M further includes an annular flow straightening groove M6 that runs horizontally around the circumferential surface of the outer flame tube 32 above the uppermost inclined protrusion M5 of the plurality of inclined protrusions. The inclined protrusions M1 to M5 and the annular flow straightening groove M6 are all formed to project outward from the surface of the outer flame tube 32, that is, toward the outer tube 33.

[0040] The inclined projection M1 is the lowest of the multiple inclined projections M1 to M5, and multiple projections are arranged side by side in the circumferential direction at the same height on the circumferential surface of the outer flame tube 32. Each inclined projection M1 has an elongated oval shape with curved ends, and the elongated oval-shaped projection is formed to be inclined at a first angle θ1 with respect to the horizontal plane. Multiple inclined projections M1 are arranged so that the ends of adjacent inclined projections M1 are separated by a predetermined first interval g1 in the circumferential direction. In this embodiment, the inclined projection M1 is formed with a projection height of approximately 1 mm and a length of approximately 10 mm. The projection height and length of this inclined projection are the same for the following inclined projections M2 to M5.

[0041] The inclined projections M2 are located directly above the lowest inclined projection M1, and multiple inclined projections are arranged side by side in the circumferential direction at the same height on the circumferential surface of the outer flame tube 32. Each inclined projection M2 has an elongated oval shape with curved ends, and the elongated oval-shaped projection is formed to be inclined with respect to the horizontal plane at a second angle θ2 that is smaller than the first angle θ1. Multiple inclined projections M2 are arranged so that the ends of adjacent inclined projections M2 are separated by a predetermined second interval g2 in the circumferential direction. The second angle θ2, which is the inclination angle of the inclined projection M2 with respect to the horizontal plane, is set to be smaller than the first angle θ1, which is the inclination angle of the inclined projection M1 with respect to the horizontal plane. In other words, the inclined projections M2 are formed at an angle closer to horizontal than the inclined projection M1.

[0042] Furthermore, the inclined protrusions M1 and M2 are positioned such that the height distance h12 between the lower end of inclined protrusion M2 and the upper end of inclined protrusion M1 is smaller than the height distance h23 between the upper end of inclined protrusion M2 and the lower end of inclined protrusion M3. As a result, inclined protrusions M1 and M2 function as a combination of an inclined protrusion with a lower section having a large angle to the horizontal plane and an upper section having a small angle to the horizontal plane.

[0043] The inclined projections M3 are located a predetermined distance above the inclined projection M2, and multiple inclined projections are arranged side by side in the circumferential direction at the same height on the circumferential surface of the outer flame tube 32. Each inclined projection M3 has an elongated oval shape with curved ends, and the elongated oval-shaped projection is formed to be inclined at a third angle θ3 with respect to the horizontal plane. Multiple inclined projections M3 are arranged so that the ends of adjacent inclined projections M3 are separated by a predetermined third interval g3 in the circumferential direction. The third angle θ3, which is the inclination angle of the inclined projection M3 with respect to the horizontal plane, is set to be smaller than the first angle θ1, which is the inclination angle of the inclined projection M1 with respect to the horizontal plane. In other words, the inclined projections M3 are formed at an angle closer to horizontal than the inclined projection M1.

[0044] Furthermore, as described above, the inclined protrusions M2 and M3 are positioned such that the height distance h23 between the upper end of inclined protrusion M2 and the lower end of inclined protrusion M3 is greater than the height distance h12 between the upper end of inclined protrusion M1 and the lower end of inclined protrusion M2.

[0045] The inclined projections M4 are located directly above the inclined projections M3, and multiple inclined projections are arranged side by side in the circumferential direction at the same height on the circumferential surface of the outer flame tube 32. Each inclined projection M4 has an elongated oval shape with curved ends, and the elongated oval-shaped projection is formed to be inclined at a fourth angle θ4 with respect to the horizontal plane. Multiple inclined projections M4 are arranged such that the ends of adjacent inclined projections M4 are separated by a predetermined fourth interval g4 in the circumferential direction. The fourth angle θ4, which is the inclination angle of the inclined projection M4 with respect to the horizontal plane, is set to be smaller than the third angle θ3, which is the inclination angle of the inclined projection M3 with respect to the horizontal plane. In other words, the inclined projections M4 are formed at an angle closer to horizontal than the inclined projections M3.

[0046] Furthermore, the inclined protrusions M3 and M4 are positioned such that the height distance h34 between the lower end of inclined protrusion M4 and the upper end of inclined protrusion M3 is smaller than the height distance h23 between the upper end of inclined protrusion M2 and the lower end of inclined protrusion M3. Similarly, the distance h34 is positioned so that it is smaller than the height distance h45 between the upper end of inclined protrusion M4 and the lower end of inclined protrusion M5. As a result, inclined protrusions M3 and M4 function as inclined protrusions that combine a lower section with a large angle to the horizontal plane and an upper section with a small angle to the horizontal plane.

[0047] Furthermore, since h23 is greater than the height distance h12, and h23 is greater than h34, two sets of inclined protrusions are provided in the height direction: an upper inclined protrusion with a small angle to the horizontal plane and a lower inclined protrusion with a large angle to the horizontal plane, resulting in the combination of inclined protrusion M1 and inclined protrusion M2, and an inclined protrusion M3 and inclined protrusion M4.

[0048] Each inclined projection M5 is positioned such that its lower end is located a predetermined distance h45 above the upper end of an inclined projection M4, and multiple inclined projections are arranged side by side in the circumferential direction at the same height on the circumferential surface of the outer flame tube 32. Each inclined projection M4 has an elongated oval shape with curved ends, and the elongated oval-shaped projection is formed to be inclined at a fifth angle θ5 with respect to the horizontal plane. Multiple inclined projections M5 are arranged such that the ends of adjacent inclined projections M5 are separated by a predetermined fifth interval g5 in the circumferential direction.

[0049] The annular flow straightening groove M6 is a single protrusion with a semi-elliptical cross-section, formed around the outer flame tube 32 at a predetermined height. The size of the annular flow straightening groove M6 is set to a protrusion height of 2-4 mm and a width of 5-8 mm to match the shape, dimensions, and type of combustion heating element 30. Furthermore, the annular flow straightening groove M6 is positioned such that its lower end is located a predetermined distance h56 above the upper end of the uppermost inclined projection M5.

[0050] Next, we will explain the function of the inclined projections M1 to M5.

[0051] In this embodiment, multiple inclined protrusions M1 to M5, each having a predetermined width and length, are arranged in the circumferential direction. By arranging multiple inclined protrusions with a predetermined width and length in the circumferential direction, swirling flows are formed at multiple locations in the circumferential direction, and stagnation and mixing are appropriately balanced to burn unburned kerosene vapor.

[0052] In other words, the combustion air flowing in from the outer cylinder air inlet 33a and circulating between the outer cylinder 33 and the outer flame tube 32 forms a swirling flow along the slope of the inclined projection M1. At this time, since there are multiple inclined projections M1 arranged in parallel in the circumferential direction, swirling flows are generated at multiple points in the circumferential direction at the same height. As a result of the generation of swirling flows, the upward velocity of the combustion air is reduced, and the swirling flows mix with each other in the region where the inclined projection M1 is formed, that is, in the region above the upper end of the inclined projection M1. Here, since there are multiple vent holes 32a formed all over the circumferential surface of the outer flame tube 32, a portion of the combustion air swirling between the outer cylinder 33 and the outer flame tube 32 flows into the combustion space 35 through the vent holes 32a while swirling, and mixes with the unburned kerosene vapor rising from the wick 34, causing the unburned kerosene vapor to burn. At this time, the combustion air mixed with the unburned kerosene vapor forms a swirling flow, so a swirling flow is also generated in the mixed flow of combustion air and unburned kerosene vapor. As it rises through the combustion space 35 over time while swirling, the release of unburned kerosene vapor is suppressed. Furthermore, because the swirling flows formed at multiple locations by the multiple inclined protrusions M1 mix with each other, mixing is promoted more effectively than when a single swirling flow is formed or when rising airflows mix, allowing for more reliable combustion of the unburned kerosene vapor. Thus, the mechanism by which the multiple inclined protrusions arranged in the circumferential direction ensure reliable combustion of unburned kerosene vapor is the same not only for inclined protrusion M1 but also for inclined protrusions M2 to M5.

[0053] Furthermore, since adjacent inclined protrusions are arranged with their ends in the width direction spaced at predetermined intervals g1 to g5 in the width direction, the swirling flow along the angle at which the inclined protrusions are inclined with respect to the horizontal plane collides with the upward flow flowing between the inclined protrusions. As a result, the collision of the swirling flow and the upward flow promotes the mixing of unburned kerosene vapor with combustion air, compared to the case where only multiple swirling flows are formed, and thus ensures more reliable combustion of the unburned kerosene vapor.

[0054] Furthermore, since the inclined protrusions M1 to M5 are formed in multiple stages, a swirling flow can be created multiple times in the combustion air rising between the outer cylinder 33 and the outer flame cylinder 32, ensuring that unburned kerosene vapor that could not be burned by a single swirling flow is reliably burned.

[0055] Furthermore, by positioning an inclined protrusion M2 with a smaller angle of inclination relative to the horizontal plane than the inclined protrusion M1 located at the lowest level, the combined effect of inclined protrusions M1 and M2 can be achieved. In other words, when imparting a swirling flow to an updraft, if one attempts to impart a swirling flow at an angle close to horizontal from the beginning, a clean swirling flow will not be formed. The flow that collides with the inclined protrusions will flow to both sides in the width direction, and these flows will collide with each other, resulting in only irregular turbulence and an uneven concentration of unburned kerosene vapor. Therefore, first, an inclined protrusion M1 with an angle of inclination close to that of an updraft, that is, a large angle of inclination relative to the horizontal plane, is placed at the lower level to reliably generate a swirling flow, and then an inclined protrusion M2 with a smaller angle of inclination is placed to generate a swirling flow at the desired angle. By arranging two levels of inclined protrusions with different angles in this way, a swirling flow at the desired angle can be reliably generated, maintaining a uniform combustion field, promoting the retention and mixing of combustion vapors, and suppressing the emission of unburned kerosene vapor.

[0056] This is also true for the combination of inclined protrusions M3 and M4. In other words, as described above, the combination of inclined protrusions M1 and M2 can reliably form a swirling flow. However, in the flow further up from inclined protrusion M2, although some swirling flow remains, as the temperature rises due to the progress of combustion, the updraft becomes dominant over the swirling flow, and there is a risk that kerosene vapor will be released unburned. Therefore, in order to form a swirling flow again, first, inclined protrusion M3 with a large inclination angle close to that of the updraft is placed to reliably generate a swirling flow, and then inclined protrusion M4 with a small inclination angle is placed to generate a swirling flow at the desired angle. By placing two stages of inclined protrusions with different angles in this way, a swirling flow at the desired angle can be reliably generated, maintaining a uniform combustion field, promoting the retention and mixing of combustion vapors, and suppressing the release of unburned kerosene vapor.

[0057] Furthermore, by arranging two sets of inclined protrusions, one with a small inclination angle and the other with a large inclination angle, at a predetermined distance apart in the height direction, unburned kerosene vapor can be reliably burned even under various combustion conditions.

[0058] In other words, if combustion progresses and the upward velocity increases, if only the combination of the lowest inclined protrusion M1 and its inclined protrusion M2 is present, the upward flow will become dominant and the swirling flow will not develop. As a result, the fuel will be discharged from the combustion space 35 without sufficient residence time and mixing, and there is a risk of releasing unburned kerosene vapor.

[0059] Therefore, in this embodiment, an inclined projection M3 with a large angle of inclination with respect to the horizontal plane is provided at a predetermined height distance h23 away from the inclined projection M2, and an inclined projection M4 with a small angle of inclination with respect to the horizontal plane is provided at a height distance h34 away from the inclined projection M3. This allows the swirling flow generated by the combination of inclined projections M1 and M2 to be further developed, ensuring that a swirling flow is reliably imparted to high-temperature combustion gases with high rising velocity, thereby securing residence time, and promoting the mixing of combustion gases and combustion air to reliably burn unburned kerosene vapors.

[0060] Furthermore, the mixing promotion unit M includes an inclined projection M5 whose lower end is positioned a predetermined distance h45 above the upper end of the inclined projection M4. The inclined projection M5 is provided to further decelerate the rising airflow, thereby imparting a swirling flow again to the combustion gas that is rising due to the high temperature in the upper part of the combustion space 35, and ensuring that the combustion gas has time to remain in the combustion space 35.

[0061] Furthermore, the mixing promotion section M includes an annular flow straightening groove M6 with a semicircular cross-section, positioned such that the lower end of the groove is located a predetermined distance h56 above the upper end of the inclined projection M5. Unlike the inclined projections M1 to M5, the annular flow straightening groove M6 is formed to encircle the circumferential surface of the outer flame tube 32 at the same height. In other words, the annular flow straightening groove M6 does not impart a swirling flow to the combustion gas, but rather temporarily holds the combustion gas inside the groove to promote mixing of unburned kerosene vapor and combustion air, and straightens the flow so that the velocity distribution of the combustion gas discharged from the combustion space 35 becomes uniform in the circumferential direction. If there were no annular flow straightening groove M6 and the inclined projection M5 were the uppermost stage of the mixing promotion section M, the combustion gas would be discharged from the combustion space 35 while maintaining a swirling flow. In that case, the combustion gas discharged from the combustion space 35 would contract towards the center, forming a long, narrow flame, which could cause the flame to fly out of the red-hot net 40. In this embodiment, by providing the annularly formed annular flow straightening groove M6 at the uppermost stage of the mixing promotion section M6, the swirling flow formed by the inclined protrusions M1 to M5 can be released and converted into an upward flow with a uniform flow velocity distribution in the circumferential direction, thereby suppressing flames from flying out of the red-hot net 40 and enabling complete combustion of unburned kerosene vapor.

[0062] Furthermore, the multiple inclined protrusions M1 to M5 and the annular straightening groove M6 all protrude outward from the surface of the outer flame tube 32. Therefore, it is possible to influence the flow of combustion air and combustion gases without narrowing the volume of the combustion space 35 formed between the outer flame tube 32 and the inner flame tube 31. In other words, if the inclined protrusions M1 to M5 and the annular straightening groove M6 were formed inward from the surface of the outer flame tube 32, the volume of the combustion space 35 would be reduced, and sufficient space for kerosene vapor to burn would not be secured, resulting in an insufficient amount of air and causing incomplete combustion. In this embodiment, since the multiple inclined protrusions M1 to M5 and the annular straightening groove M6 all protrude outward from the surface of the outer flame tube 32, it is possible to form a swirling flow and promote mixing without narrowing the volume of the combustion space 35.

[0063] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. In this embodiment, the inclined protrusions M1 to M5 are oval-shaped with curved ends, but they may also be rectangular without curves. Furthermore, the protruding height of the inclined protrusions M1 to M5 is set to approximately 1 mm and the length to approximately 20 mm, but these are not limited to these, and may be appropriately changed considering the overall size of the combustion heating element 30 and the required combustion performance. In addition, the inclined protrusions M1 to M5 do not necessarily need to be formed in five stages, and can be effective even as a single stage.

[0064] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Furthermore, the effects described in the embodiments of the present invention are merely a list of the most preferred effects arising from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0065] Furthermore, the embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those comprising all the configurations described. [Industrial applicability]

[0066] The natural convection wick-type kerosene stove of this invention can be applied to various types of kerosene stoves. [Explanation of Symbols]

[0067] 1. Natural convection type wick oil stove 10 core vertical device 20 kerosene tanks 30 Combustion heating element 31 Inner Flame Canister 32 Outer flame tube 33 Outer cylinder M Mixing promotion part M1~M5 Slanted protrusion M6 Annular Flow Rectifier Groove 34 wick 40 Red-hot net 50 Protective fence / post 60 Top plate

Claims

1. In a natural convection wick type oil stove comprising, from the inside out, a cylindrical inner flame tube, a cylindrical outer flame tube, and a cylindrical outer cylinder, and in which a wick is placed in the annular space formed between the inner flame tube and the outer flame tube to form a combustion space, A mixing promotion section consisting of multiple protrusions is formed on the surface of the outer flame tube. The aforementioned plurality of protrusions are inclined protrusions that are provided at an angle to the horizontal plane, and the plurality of these inclined protrusions are arranged in parallel in the circumferential direction of the outer flame tube. Natural convection type wick-type kerosene stove.

2. The aforementioned plurality of inclined protrusions are arranged side by side with a predetermined interval in the width direction. A natural convection type wick-type oil stove as described in claim 1.

3. The aforementioned inclined protrusions are arranged in multiple stages in the height direction. A natural convection type wick-type oil stove as described in claim 1.

4. The aforementioned multi-stage inclined projection is formed by a combination of a lower stage with a large angle to the horizontal plane and an upper stage with a small angle to the horizontal plane. A natural convection type wick-type oil stove as described in claim 3.

5. Two sets of the combination of the upper inclined projection and the lower inclined projection are provided in the height direction. A natural convection type wick oil stove as described in claim 4.

6. The plurality of inclined protrusions project outward from the surface of the outer flame tube. A natural convection type wick-type oil stove according to any one of claims 1 to 5.

7. As the mixing promotion section, an annular flow straightening groove continuous in the circumferential direction is provided above the inclined projection. A natural convection type wick-type oil stove according to any one of claims 1 to 5.

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