Ignition device for hybrid rocket and hybrid rocket

Abstract

To provide an ignition device capable of re-ignition and uniformly burning solid fuel.SOLUTION: A device for igniting a solid fuel includes a first member made of a conductive material and having a through-hole inside, a second member made of a conductive material and having a through-hole inside, a third member provided between the first member and the second member and having a through-hole inside and made of an insulating material for insulating the first member and the second member from each other, and a shape of the third member is formed such that an outer thickness is larger than an inner thickness. By making an inner insulation distance of the third member smaller than an outer insulation distance of the third member, when a voltage is applied between the first member and the second member, a discharge phenomenon is generated between the first member and the peripheral edge portion of the through hole inside the second member.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to an ignition device for a hybrid rocket and a hybrid rocket using the ignition device, and in particular to an ignition device that uses arc discharge. [Background technology]

[0002] For example, Patent Document 1, entitled "Restartable Ignition Device, System, and Method Therefor," discloses a technology in which an insulator such as ABS resin is placed between two electrodes, and when a voltage is applied between the electrodes, a potential field is provided along the inner surface of the insulator such as ABS resin, and a local arc discharge is generated due to the effect of the electric field on the insulator such as ABS resin.

[0003] FIG. 1 illustrates the configuration of Patent Document 1. FIG. 1 shows how a housing made of an insulator such as ABS resin is configured to have minute protrusions formed thereon, and then a notch is provided in a part of the insulator at a position approximately equal to the two electrodes, and how an arc discharge occurs in the gap between the notches. A cutout is an uneven area in an insulator, and is often called a void because it is a space that does not have any intentionally created structure. This technology allows for Joule heating and thermal decomposition of the inner surface of an insulator such as ABS resin, enabling restartable ignition of a hybrid rocket system.

[0004] Furthermore, Patent Document 2, "Arc Igniter for Micro-Nano Satellites," discloses a technology in which an insulator such as a polymer is placed between two electrodes, and when a voltage is applied to the electrodes, an electrical breakdown occurs in a part (conductive path) between the two electrodes when the voltage applied to the electrodes exceeds a threshold, generating a high-temperature arc discharge. FIG. 2 illustrates the configuration of Patent Document 2. FIG. 2 shows that a conductive path is provided in a part of a housing made of an insulator such as a polymer at a position approximately equal to the two electrodes, and discharge occurs in a gap in the insulator near the conductive path.

[0005] According to this technology, arc discharge exposes an insulator such as a polymer to high temperatures, generating hydrocarbon vapor, and an initial flame is formed by flowing an oxidizer. As the solid fuel portion propagates downstream, it is continuously pyrolyzed and combusted, and re-ignition is possible by turning on / off the ignition or oxidizer. In addition, paragraph 0008 of Patent Document 2 states, "The present invention adopts the ignition principle of polymer low-pressure breakdown, and compared to other ignition methods, minimizes the instantaneous power consumption at ignition to 3W, making it suitable for micro-nano satellite platforms with limited total power supply power."

[0006] As such, Patent Document 1 and Patent Document 2 have in common the fact that they are both configured by inserting an electrode into an insulator, and that a local arc discharge is generated in a part of the insulator by applying a high voltage to the electrode. Furthermore, both Patent Document 1 and Patent Document 2 have in common the fact that they generate local arc discharges in a part of the insulator, rather than between electrodes, by forming an uneven area by providing a minute protrusion (not shown) in a part of the insulator and then forming a cutout portion (void) (Patent Document 1) or by providing a conductive path (Patent Document 2).

[0007] Therefore, according to the techniques of Patent Documents 1 and 2, it is possible to discharge at a relatively low voltage of about several hundred volts, and it is possible to reduce power consumption during this discharge. 3(a) to 3(c) are diagrams that schematically represent the discharge phenomenon of Patent Document 1 or Patent Document 2, and each show a conceptual diagram, an equivalent circuit, and an image of the required voltage. Figure 3(a) shows how a void or other uneven portion is formed in a part of an insulator such as ABS resin, causing partial discharge in that portion. Figure 3(b) shows the equivalent circuit of Figure 3(a). Figure 3(b) shows that the equivalent circuit has capacitance configured in parallel between the electrodes.

[0008] Furthermore, if there is a void or the like (uneven area), it can be seen that the equivalent circuit is one in which the capacitance of the void or the like (uneven area) is arranged in series with part of the capacitance configured in parallel. Figure 3(c) is a diagram showing the voltage and current of partial discharges in voids and dielectric breakdown between electrodes. Figure 3(c) suggests that by utilizing partial discharges in voids, it is possible to ignite with a relatively low voltage of several hundred volts, a small current, and therefore low power consumption. Patent Document 1 and Patent Document 2 also share the same features, such as providing a portion equivalent to a void, such as providing a cutout in a part of the insulator, and the ability to ignite with low power consumption, and it appears that they utilize the mechanism shown in Figure 3.

[0009] However, in the technologies described in Patent Documents 1 and 2, the location where the discharge occurs is limited to one location, and moreover, when viewed in terms of its position relative to the cylindrically-shaped solid fuel, it is limited to one location away from the center, which causes the combustion and retreat of the solid fuel to not progress evenly, resulting in an uneven distribution of energy. This situation is illustrated in Figure 4. Figure 4(a) shows the state immediately after the start of ignition (combustion), and Figure 4(b) shows the state after multiple ignitions (combustions) where the solid fuel has burned to a certain extent and retreated.

[0010] 4, it is shown that an initial flame 720 generated by ignition by discharge and a reaction with the introduced oxidizer 710 flows into the combustion port 500, and due to the combustion promotion effect of the introduced oxidizer 710, boundary layer combustion (731, 732) occurs near the surface of the solid fuel 400. It can be seen that the boundary layer combustion (731, 732) gradually burns the solid fuel 400 while causing the solid fuel 400 to retreat.

[0011] Here, in the conventional technology, the discharge point 20 of the ignition device 100 is limited to one location away from the center of the combustion port 500, so the location where the initial flame 720 occurs is biased, and even if the oxidizer 710 is introduced, the boundary layer combustion (731, 732) is biased. More specifically, compared to the boundary layer combustion 731 closer to the initial flame 720 caused by ignition, the boundary layer combustion 732 farther away becomes weaker, and if re-ignition is repeated, there is a disadvantage that the combustion and regression of the solid fuel 400 also becomes uneven (see the instructions in Comment 4-1).

[0012] Furthermore, unstable combustion also had the disadvantage of affecting the ability to consistently generate a constant thrust. To prevent such imbalance, other methods were required, such as generating a swirl in the flame to cause vortex-like combustion inside the combustion port 500, but these methods often did not work well.

[0013] Therefore, a technology was devised to burn the solid fuel evenly by making the solid fuel of a hybrid rocket engine itself a conductive solid fuel, embedding electrodes in the conductive solid fuel, and directly heating the solid fuel, as in Patent Document 3, "Conductive solid fuel, ignition device...rocket combustion system." The technology of Patent Document 3 is shown in FIG.

[0014] Figure 5 shows a structure in which, by embedding electrodes in conductive solid fuel, an electrical path is generated inside the conductive solid fuel when a voltage is applied to the electrodes, and the heat generated in the electrical path is used to heat and vaporize the conductive solid fuel, thereby generating gasified fuel in the through-holes. With this structure, an oxidizer is injected onto the generated gasified fuel, generating combustion gas through a chemical reaction, making it possible to burn the solid fuel stably and causing the solid fuel to burn and retreat evenly. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] US Patent Application Publication No. 2015 / 0322892 [Patent Document 2] Chinese Patent Application Publication No. 114718765 [Patent Document 3] International Publication No. 2023 / 074532 Summary of the Invention [Problem to be solved by the invention]

[0016] However, when using the technology of Patent Document 3, although it is possible to burn and retreat the solid fuel evenly, it has the disadvantage that it consumes a lot of power and requires a relatively large battery because it employs a mechanism to heat the conductive solid fuel, making it difficult to install on a small rocket. Furthermore, because the electrodes are embedded in the solid fuel, there is the inconvenience that, although rare, as the solid fuel burns and retreats, the electrodes may remain exposed in the through-holes (corresponding to the combustion ports 500).

[0017] This is shown in Figure 6. Figure 6 shows that in rare cases, problems may occur, such as impeding the smooth flow of oxidizer and flame (see the portion indicated by Comment 6-1) or the remaining electrode falling into the through-hole (see the portion indicated by Comment 6-2), damaging the nozzle.

[0018] Therefore, the present invention aims to provide an ignition device that overcomes the disadvantages of Patent Documents 1 and 2 (such as the difficulty of uniformly burning and retreating the solid fuel) and also overcomes the disadvantages of Patent Document 3 (high power consumption and adverse effects caused by remaining electrodes).

[0019] More specifically, regarding the disadvantage of Patent Document 3, namely the high power consumption, the present invention aims to provide an ignition device that consumes less power by utilizing a high-voltage discharge phenomenon rather than a heat generation phenomenon. In addition, to address the drawbacks of the rare case of electrodes remaining as described in Patent Document 3, and the inconveniences of Patent Documents 1 and 2 (such as the difficulty of uniformly burning and retreating the solid fuel), the objective is to provide an ignition device that enables uniform burning and retreating of the solid fuel and can stably exert a constant thrust. [Means for solving the problem]

[0020] In order to achieve the above object, the first invention is: 1. An apparatus for igniting solid fuel, comprising: a first member made of a conductive material and having a through hole therein; a second member made of a conductive material and having a through hole therein; a third member provided between the first member and the second member, having a through hole therein, and made of an insulating material for insulating the first member from the second member; The third member is shaped so that the outer thickness is greater than the inner thickness, and the inner insulation distance is made smaller than the outer insulation distance of the third member, When a voltage is applied between the first member and the second member, The method is characterized in that a discharge phenomenon occurs between the first member and the periphery of the through hole inside the second member.

[0021] The second invention is: In the ignition device according to the first aspect of the present invention, When a voltage is applied between the first member and the second member, A discharge phenomenon is generated between the first member and a peripheral portion of the through hole inside the second member, and By generating a discharge phenomenon between the first member and the periphery of the through hole inside the second member in a discharge area over the entire periphery of the through hole due to multiple discharges, The second member and the third member and / or the first member are retracted evenly from the inside.

[0022] The third invention is In the ignition device according to the second aspect of the present invention, The three-dimensional shape of the first member is characterized in that the thickness increases from the inside to the outside.

[0023] The fourth invention is In the ignition device according to any one of the first to third aspects of the present invention, The second member is plate-shaped, and the inner shape is One or a combination of circular, polygonal, star, and fractal shapes; When a voltage is applied between the first member and the second member, The method is characterized in that a discharge phenomenon occurs between the first member and the periphery of the through hole inside the second member.

[0024] The fifth invention is In the ignition device according to any one of the first to third aspects of the present invention, The shape of the second member is A shape in which a plurality of protrusions appear on the periphery of the inner through-hole, such as a lattice shape, a spider web shape, a honeycomb shape, a spiral shape, a combination of triangles, a combination of a plurality of small diameter holes, or any other shape, When a voltage is applied between the first member and the second member, The method is characterized in that a discharge phenomenon occurs between the first member and any one of the plurality of protrusions on the periphery of the through hole inside the second member.

[0025] The sixth invention is In the ignition device according to any one of the first to third aspects of the present invention, The conductive material used for the second member is characterized by including at least one of a conductive polymer, graphite, carbon fiber, metal powder, and metal fiber.

[0026] The seventh invention is In the ignition device according to any one of the first to third aspects of the present invention, When a conductive polymer is used as the conductive material used for the second member, The physical properties of the conductive polymer are as follows: It is characterized by a volume resistivity of 30 to 115 Ω·cm when layered using 3D printing.

[0027] The eighth invention is In the ignition device according to any one of the first to third aspects of the present invention, When a conductive polymer is used as the conductive material used for the second member, The insulating material of the third member is HDPE.

[0028] The ninth invention is In the ignition device according to the fourth aspect of the present invention, When HDPE is used as the insulating material of the third member of the ignition device, When an oxidizer is injected toward the through hole inside the ignition device and the oxidizer is ignited and burned by a discharge phenomenon caused by applying a voltage between the first member and the second member, The present invention is characterized in that at least the second member of the first and second members made of the conductive material retracts together with the third member.

[0029] The tenth invention is In the ignition device according to the fifth aspect of the present invention, When HDPE is used as the insulating material of the third member of the ignition device, When an oxidizer is injected toward the through hole inside the ignition device and the oxidizer is ignited and burned by a discharge phenomenon caused by applying a voltage between the first member and the second member, The present invention is characterized in that at least the second member of the first and second members made of the conductive material retracts together with the third member.

[0030] The eleventh invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to any one of the first to third aspects of the present invention is provided. It is a hybrid rocket characterized by:

[0031] The twelfth invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to any one of the first to third aspects of the present invention is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retreats together with the third member, The regression rate is substantially the same as the regression rate of the solid fuel.

[0032] The thirteenth invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to the fourth aspect of the present invention is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retreats together with the third member, the regression speed of the second member and the third member is substantially the same as the regression speed of the solid fuel; It is a hybrid rocket characterized by:

[0033] The fourteenth invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to the fifth aspect of the present invention is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member, and the regression speed of the second member and the third member is substantially the same as the regression speed of the solid fuel; It is a hybrid rocket characterized by:

[0034] The fifteenth invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to the sixth aspect of the present invention is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retreats together with the third member, the regression speed of the second member and the third member is substantially the same as the regression speed of the solid fuel; It is a hybrid rocket characterized by:

[0035] The sixteenth invention is In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to the seventh aspect of the present invention is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retreats together with the third member, the regression speed of the second member and the third member is substantially the same as the regression speed of the solid fuel; It is a hybrid rocket characterized by: [Effects of the Invention]

[0036] According to the present invention, an ignition device can be provided that uses an ignition method that utilizes the discharge phenomenon caused by arc discharge, thereby significantly reducing power consumption compared to heating methods. Furthermore, by using a structure that generates arc discharges successively around the entire periphery of the through hole inside the ignition device, it is possible to make the ignition device itself retreat evenly from the inside, and also to make the solid fuel retreat evenly from the inside. Furthermore, it enables stable output even after multiple ignitions.

[0037] Figure 7 shows a schematic diagram of the retreat state when the ignition device of the present invention is used. Figure 7(a) shows the state immediately after the start of ignition (combustion), and Figure 7(b) shows the state after multiple ignitions (combustions) have occurred, when the solid fuel has burned to a certain extent and retreated. FIG. 7 shows that an initial flame 720 generated by ignition by discharge and reaction with the injected oxidizer 710 flows into the combustion port 500, and the combustion-promoting effect of the injected oxidizer 710 causes boundary layer combustion (731, 732) to occur near the surface of the solid fuel 400.

[0038] The boundary layer combustion (731, 732) gradually burns the solid fuel 400 while causing the solid fuel 400 to retreat. In the prior art (Patent Documents 1 and 2), the discharge point 20 of the ignition device 100 is limited to one location away from the center of the combustion port 500, which causes a bias in the location where the initial flame 720 is generated, and even when the oxidizer 710 is introduced, a bias occurs in the boundary layer combustion (731, 732).

[0039] On the other hand, in the case of the ignition device of the present invention, the discharge location extends over the entire discharge area, which is the entire inner periphery of the ignition device. Therefore, the initial flame 720 caused by ignition is also generated over the entire circumference inside the combustion port 500 of the solid fuel 400, and the subsequent boundary layer combustions 731 and 732 can also be generated evenly over the entire circumference. This allows the solid fuel to be retracted evenly from the inside (see the instructions in Comment 7-2), enabling stable power control.

[0040] In Figure 7, only two marks (star-shaped marks) indicating the discharge points are shown on the left and right sides, but this is done only for the sake of simplicity of illustration; discharge points can be generated one after another all around the periphery of the through-hole inside the ignition device.

[0041] FIG. 8 shows a comparison table with the present invention, including the above Patent Documents 1 to 3 as well as other conventional technologies (catalytic ignition, gas torch ignition, laser ignition, nichrome wire heating, and glow plug system). For example, Technology A's catalytic ignition uses polyethylene or similar as fuel and hydrogen peroxide as the oxidizer. MnO2-Al2O3 (a mixture of manganese dioxide and alumina) is used as a catalyst, and hydrogen peroxide is sprayed onto the surface, causing the hydrogen peroxide to self-heating decompose and mix with the fuel, automatically igniting the mixture. This catalytic ignition method is extremely advantageous in terms of weight reduction, as it does not require the installation of special equipment as an ignition device. However, it has the drawback of only being applicable when the oxidizer is hydrogen peroxide. For example, if nitrous oxide could be used, a pressure pump would be unnecessary due to its self-pressurization, whereas hydrogen peroxide requires a pressure pump, which is an inconvenience.

[0042] Additionally, the gas torch ignition method of Technology D uses acrylic resin (methyl methacrylate, PMMA) as fuel and gaseous oxygen (GOX) as the oxidizer. Ignition with a gas torch using a spark plug ensures reliable ignition, but the use of methane leaves safety concerns.

[0043] In Technology E's laser ignition method, a laser is irradiated onto the ABS resin, applying high energy locally to gasify the ABS resin, which is then ignited by spraying an oxidizer onto it. Although it consumes around 10W of power, it has the disadvantage of requiring accessories such as a laser generator, heat sink, and lens, which makes the system more complex and increases its weight.

[0044] The heating method of Technology F uses HDPE as the fuel and nitrous oxide (N2O) as the oxidizer, along with nichrome wire and gaseous oxygen (GOX). Nitrous oxide contains a high amount of nitrogen molecules, making it much more difficult to ignite than oxygen. While ignition can be ensured by heating the nichrome wire and using gaseous oxygen, the required power is around 100-200W. Furthermore, the need for oxygen to assist ignition in addition to the oxidizer has the disadvantage of making the system more complex and increasing its weight.

[0045] Furthermore, Technique B (Patent Document 1), Technique C (Patent Document 2), and Technique H (Patent Document 3) also have the above-mentioned inconveniences. As described above, it can be said that there has not yet been a small, safe, and energy-efficient ignition device that can be applied to the propulsion systems of small spacecraft. On the other hand, the ignition device of the present invention has no particular disadvantages, and has the advantages of low power consumption, being able to be made smaller, and being able to burn and retreat the solid fuel evenly from the inside. [Brief explanation of the drawings]

[0046] [Figure 1] FIG. 1 is a diagram showing an example of a conventional technique (Patent Document 1). [Figure 2] FIG. 1 is a diagram showing an example of the prior art (Patent Document 2). [Figure 3] FIG. 1 is a diagram showing an example of an equivalent circuit etc. of the prior art (Patent Documents 1 and 2). [Figure 4] FIG. 1 is a diagram showing an example of an ignition device and a combustion problem according to the prior art (Patent Documents 1 and 2). [Figure 5] FIG. 1 is a diagram showing an example of the prior art (Patent Document 3). [Figure 6] FIG. 1 is a diagram showing an example of an ignition device and combustion problem of the prior art (Patent Document 3). [Figure 7] FIG. 10 is a diagram illustrating an example of the effect of the present invention. [Figure 8] 1 is a comparison table between the prior art and the present invention. [Figure 9] FIG. 1 is a diagram illustrating an example of the overall configuration of a hybrid rocket. [Figure 10] FIG. 1 is a diagram showing an example of the configuration of the vicinity of an ignition device of a hybrid rocket. [Figure 11] 11A and 11B are diagrams showing an example of a method for applying current to conductive members (first and second members), where Fig. 11A shows an example of soldering a cable, and Fig. 11B shows an example of applying current using a metal plate or the like. [Figure 12] 12A and 12B are diagrams showing an example of a typical example of an ignition device, in which FIG. 12A is a perspective view and FIG. 12B is a front view. [Figure 13] 13A and 13B are diagrams showing an example of a modified ignition device in which the shape is modified to be substantially cylindrical, in which FIG. 13A is a perspective view and FIG. 13B is a cross-sectional view taken along the line BB. [Figure 14] 14A and 14B are cross-sectional views of a typical example of an ignition device, in which FIG. 14A is a perspective view of a cross section taken along line AA, and FIG. 14B is a cross-sectional view taken along line BB. [Figure 15] 15A and 15B are diagrams showing an example of a modification in which the shape of a step portion is modified based on a typical example of an ignition device, where FIG. 15A is a perspective view of a cross section taken along line AA, and FIG. 15B is a cross section taken along line BB. [Figure 16]16A and 16B are diagrams showing an example of a modified example in which the thickness of the first member near the peripheral portion of the through hole is modified based on a typical example of an ignition device, where FIG. 16A is a perspective view of the AA cross section, and FIG. 16B is a BB cross section. [Figure 17] 17A and 17B are diagrams showing an example of a modified example in which the shape of the inclined portion of the first member is modified based on a typical example of an ignition device, where FIG. 17A is a perspective view of the cross section taken along line AA, and FIG. 17B is a cross section taken along line BB. [Figure 18] FIG. 14 is a cross-sectional view taken along line BB of a typical example of the ignition device (FIGS. 12 and 14), showing the dimensions of each part. [Figure 19] FIG. 16 is a cross-sectional view taken along line BB of the ignition device of the embodiment of FIG. 15, showing the dimensions of each part. [Figure 20] FIG. 17 is a cross-sectional view taken along line BB of the ignition device of the embodiment of FIG. 16, showing the dimensions of each part. [Figure 21] FIG. 18 is a cross-sectional view taken along line BB of the ignition device of the embodiment of FIG. 17, showing the dimensions of each part. [Figure 22] FIG. 15 is an exploded view of a typical example of an ignition device (FIGS. 12 and 14). [Figure 23] FIG. 10 is a diagram showing that there is a degree of freedom in the combination of the first member, the second member, and the third member that constitute the ignition device, and is a diagram showing an example of some modified examples. [Figure 24] 15 is a diagram showing an example of a second member in the typical example of the ignition device (FIGS. 12 and 14). FIG. [Figure 25] FIG. 10 is a diagram showing a modified example of the second member, showing an example of an embodiment in which the outer periphery has a quadrangular shape. [Figure 26] FIG. 10 is a diagram showing a modified example of the second member, showing an example of an embodiment in which the outer periphery has an octagonal shape. [Figure 27] FIG. 10 is a diagram showing a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made up of a lattice-shaped member, and has a through-hole that is a circular hole cut out from the inside of the member, with protrusions appearing on the periphery of the through-hole. [Figure 28]FIG. 28 is a diagram showing a modified example of the second member of the embodiment of FIG. 27, showing an example of an embodiment in which the outer periphery has a rectangular shape. [Figure 29] FIG. 28 is a diagram showing a modified example of the second member of the embodiment of FIG. 27, showing an example of an embodiment in which the outer periphery has an octagonal shape. [Figure 30] FIG. 10 is a diagram showing a modified example of the second member, in which the part that burns and retreats due to discharge and ignition is made up of a radial or spider web-shaped member, has a through hole that is hollowed out in a circular shape on the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through hole. [Figure 31] This is a diagram showing a modified example of the second member, in which the part that burns and retreats due to discharge and ignition is made of a honeycomb-shaped member, has a through hole that is a circular hole cut out from the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through hole. [Figure 32] FIG. 10 is a diagram showing a modified example of the second member, in which the part that burns and retreats due to discharge and ignition is made up of a spiral member, has a through hole that is a circular hole cut out from the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through hole. [Figure 33] FIG. 10 is a diagram showing a modified example of the second member, in which the part that burns and retreats due to discharge and ignition is made up of a triangular lattice-shaped member, and has a through-hole that is a circular hole cut out from the inside of the member, with protrusions appearing on the periphery of the through-hole. [Figure 34] FIG. 10 is a diagram showing a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is composed of a plurality of small-diameter circular holes, and the member has a through-hole that is a circular hole cut out from the inside, with protrusions appearing on the periphery of the through-hole. [Figure 35] This figure shows modified examples of the peripheral portion of the through hole of the second member in the embodiment of Figure 24, and shows that there is a degree of freedom in the shape and configuration of the peripheral portion of the inner through hole, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares and octagons, stars, fractals, etc. [Figure 36]27A and 27B are diagrams showing modified examples of the peripheral portion of the through hole of the second member, and show that there is a degree of freedom in the shape and configuration of the peripheral portion of the inner through hole, and that various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares, pentagons, and octagons, and star shapes. [Figure 37] This is an AA cross-sectional view showing that when a plate-shaped second member is used, the outer thickness of the third member of the ignition device is configured to be thicker than the inner thickness, thereby generating discharge around the periphery of the through hole on the inner side of each member. [Figure 38] This is an AA cross-sectional view showing that when an embodiment having a protrusion on the inside of the second member is used, by configuring the outer thickness of the third member of the ignition device to be thicker than the inner thickness, discharge occurs around the periphery of the through hole on the inside of each member. [Figure 39] This is a plan view showing that when a plate-shaped second member is used, multiple ignitions cause discharges to progress sequentially around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the third member and / or the first member also retreat in the same way as the second member, but are not shown in the figure. [Figure 40] This is a plan view showing that when a grid-shaped projection is used among the projections provided on the inside of the second member, multiple ignitions cause discharges to progress sequentially around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the third member and / or the first member also retreat in the same way as the second member, but are not shown in the figure. [Figure 41] This is a plan view showing that when a spider web-shaped protrusion is used among the protrusions provided on the inside of the second member, multiple ignitions cause discharge to progress sequentially around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the third member and / or the first member also retreat in the same way as the second member, but are not shown in the figure. [Figure 42]14 to 16, and the second member has a plate-like shape as in FIG. 24 and FIG. 35, or has a protrusion on the inside as in FIG. 27, FIG. 30 to FIG. 34, and FIG. 36. This is a cross-sectional view taken along the line B-B showing how each member retracts due to multiple ignitions. [Figure 43] 36 is a diagram showing how each member retreats due to discharge when the second member has a plate-like shape as in FIGS. 24 and 35. FIG. [Figure 44] 37 is a diagram showing how each member retreats due to discharge when the second member has a shape with protrusions on the inside as shown in FIGS. 27, 30 to 34, and 36. FIG. [Figure 45] FIG. 10 is a BB cross-sectional view showing how each member retreats due to multiple ignitions when a first member having an inner thickness close to that of a third member is used. [Figure 46] FIG. 10 is a diagram showing an example of characteristics when a conductive polymer is used as the conductive material. [Figure 47] FIG. 10 is a table showing examples of materials for the third member. [Figure 48] FIG. 1 is a diagram showing an example of a system configuration for a combustion experiment. [Figure 49] FIG. 1 is a diagram showing an example of an ignition sequence for a combustion experiment. [Figure 50] FIG. 10 is a diagram showing an example of the results of a combustion experiment, showing values ​​of pressure sensors before and after the throttling valve. [Figure 51] FIG. 10 is a diagram showing an example of the transition of the pressure inside the chamber in a combustion experiment. [Figure 52] FIG. 10 is a diagram showing an example of the results of a combustion experiment, illustrating the retraction of each part of the ignition device and the hybrid rocket.

[0047] <Terminology> ◇A hybrid rocket is a rocket that is constructed in such a way that an oxidizer is injected by an injector, ignited by an ignition device, and the resulting high-temperature flame ignites solid fuel, which is then ejected from a nozzle.It is called a hybrid rocket because it combines different types of phases, namely, liquid oxidizer and solid fuel. Liquid oxygen or nitrous oxide is used as an oxidizer, and since the oxidizer is not flammable, and the solid fuel is often made of resin material printed using a 3D printer, which is also relatively non-flammable, the system is considered safe.

[0048] ◇Boundary layer combustion is the process in which gasified solid fuel mixes with an oxidizer and burns within the turbulent boundary layer on the surface of the solid fuel.Boundary layer combustion is a complex process involving the interaction of various phenomena, such as chemical reactions, phase changes of substances, and the transport of substances and heat. However, it is known that it is difficult to sufficiently mix the oxidizer with the fuel gasified from the solid fuel, and it is also difficult to maintain a constant mixture ratio considering that the flow of the oxidizer is turbulent. As a result, it is difficult to maintain a constant mixture ratio, and as a result, it is difficult to burn the solid fuel evenly.

[0049] ◇Re-ignition is the process of stopping combustion once and then restarting it. By configuring the re-ignition, it is possible to perform the following process: ignition - combustion - combustion interruption - re-ignition - combustion. A launch vehicle only needs to be ignited once at launch and does not need to be reignited. However, reignition is essential for kick motors used in space for purposes such as orbital transfer to a non-intersecting orbit (such as Hohmann transfer), orbital insertion into an orbit around another celestial body, or landing on a gravitational celestial body.

[0050] ◇Arc discharge is the most advanced type of gas discharge, and is a type of discharge that is maintained by the emission of thermoelectrons from a high-temperature cathode. In atmospheric arc discharge, the discharge path is arc-shaped, so it is also called arc discharge or simply arc. When the gas pressure is high and the current is large, at several amperes or more, the discharge almost always becomes an arc discharge. Even when the gas pressure is low and the current is relatively low, at several hundred milliamperes, the discharge can still occur if the cathode is prone to becoming hot or if the cathode is coated with a thermionic emission material (which makes it easy to emit thermions). The voltage is relatively low, ranging from several tens to several hundred volts, but a large current flows. The electrodes are connected by a bright, flame-like positive column, where an equal number of electrons and positive ions form plasma. The temperature of the arc generally exceeds 1000°C, and can reach 3500°C. Part of the electrode material also evaporates, becoming the light source of the spectrum.

[0051] *The "Discharge Area" is the general term for the discharge points on the periphery of the through-hole inside the first and second members. There are not just one but multiple discharge points, and because discharges occur one after another all around the periphery of the through-hole inside the first and second members, we have decided to call the discharge points all around the periphery of the through-hole "Discharge Area." This is intended to clarify the features of the present invention and to make clear the differences from the prior art, whereas in prior art the discharge location is often limited to one location in a small area.

[0052] The edge effect in discharge phenomena refers to the phenomenon where, when there are sharp or uneven parts, the electric field strength is greater at the convex parts, causing discharge to concentrate at these parts. *Anode means positive pole, and cathode means negative pole. In the combustion experiments of the present invention, the first member was the anode (positive pole) and the second member was the cathode (negative pole), but this is not limited to this and the reverse connection is also acceptable. In the case of arc discharge, the amount of heat generated on the cathode side is often greater, and if the second member is the cathode (negative pole), the second member tends to have a faster retreat speed.

[0053] ◇Recession of a component means that the periphery of the inner through-hole of the first component, second component, third component, etc. burns due to discharge (ignition), gradually spreading toward the outside (periphery) of the component. ◇Similarly, the retreat of solid fuel means that the inner wall (combustion port) of the solid fuel is burned by the discharge (ignition), causing it to gradually spread toward the outside (periphery) of the solid fuel.

[0054] ◇The retreat speed of a component directly means the speed at which the component retreats, but it also includes the meaning of the amount or rate at which the component retreats due to one or more discharges (ignitions). It also refers to the rate at which the radius of the through-hole inside the component increases as the component or solid fuel burns due to multiple discharges (ignitions), and the radius gradually increases from the center of the component to the outside.

[0055] ◇The component retreating evenly means that multiple ignitions cause discharges to occur successively around the entire periphery of the through-hole inside the component, causing the periphery of the through-hole to retreat a predetermined distance around one circumference at approximately the same distance from the center, and then to retreat a predetermined distance around the next circumference, repeating this step. In other words, it is like cutting out the periphery of a through-hole inside a component with a circle of a certain radius. After cutting out the entire circumference, you can also explain this as a method of retreating by repeating this step of cutting out the periphery of the through-hole with a circle of a larger radius.

[0056] Furthermore, if we call the even retreat of the peripheral portion of the through-hole inside the component, as described above, by one revolution at a time, "even retreat per revolution," then the following "recession that can be evaluated as having occurred evenly as a result of repeated discharges (ignitions) as a whole" would also be included in "the component retreating evenly." In other words, although a portion of the peripheral edge of the through hole inside the member recedes (not every full circumference of the peripheral edge of the through hole inside the member), by repeating the discharge (ignition) multiple times, the expansion of the through hole inside the member eventually converges into an approximately circular shape, resulting in an even receding. DETAILED DESCRIPTION OF THE INVENTION

[0057] Hereinafter, examples of the present invention will be described. The configurations, drawings, and tables in the description are merely examples, and can be applied to other shapes and configurations.

[0058] 1. About Hybrid Rockets 1-1. Overall structure First, the overall configuration of the hybrid rocket will be explained using FIG. As shown in Figure 9, the hybrid rocket is composed of an oxidizer tank (not shown), an oxidizer port 700, an ignition device 100, a case 200, a heat insulating material 300, a solid fuel 400, a combustion port 500 inside the solid fuel, and an injection nozzle 800.

[0059] FIG. 9 also shows that the oxidizer discharged from an oxidizer tank (not shown) is introduced into the ignition device 100 of the rocket body through an oxidizer port 700. Electric power is supplied to the ignition device 100 via voltage application ports 600 and 610, and ignitions are successively performed by discharge all around the discharge area 140 provided on the periphery of the through-hole inside the ignition device 100.

[0060] 1-2. Structure around the ignition device of the hybrid rocket Next, the structure and function of the hybrid rocket's ignition device will be explained using Figure 10. FIG. 10 is a diagram showing an example of the structure in the vicinity of the ignition device of a hybrid rocket. 10 shows that the ignition device 100 is configured such that a first member 110 and a second member 120 made of a conductive material sandwich a third member 130 made of an insulating material from above and below. Note that the first member 110 and the second member 120 are painted gray to indicate that they are made of a conductive material (the same applies below).

[0061] Furthermore, the voltage application ports 600, 610 may have holes formed therein for passing cables, metal plates, etc. for applying a voltage to the ignition device 100 (the holes are not shown). Here, the two ports, voltage application port 600 and voltage application port 610, are provided to correspond to the anode or cathode, respectively, and are connected to a first member 110 and a second member 120 made of a conductive material.

[0062] In addition to this, ventilation ports for introducing ventilation gas supplied from a purge tank (see Figure 48) to exhaust exhaust gas after combustion are also provided as appropriate, but are not shown in the figure. Furthermore, unlike the prior art, the present invention is characterized in that it does not have so-called electrodes per se, but rather the first member 110 and the second member 120, which are made of conductive material, serve as electrodes and as discharge sites.

[0063] When a predetermined voltage is applied to the first member 110 and the second member 120, which are made of a conductive material, the presence of the third member 130, which is made of an insulating material, allows the discharge location that occurs between the first member 110 and the second member 120 to be limited to a discharge area 140 on the periphery 150 of the through hole inside the ignition device 110. The discharge can be an arc discharge. High-temperature sparks generated by ignition from the arc discharge generate an initial flame 720 in which the third member made of an insulating material such as resin and the second member and / or the first member are burned.

[0064] When an oxidizer 710 is introduced simultaneously with or before or after ignition, an initial flame 720 moves downstream of the combustion port and spreads to the surface of the solid fuel 400, generating boundary layer combustion 731, 732 on the surface of the solid fuel 400 and promoting combustion of the solid fuel 400. As described above, the boundary layer combustion 731, 732 is composed of a complex process in which various phenomena, such as chemical reactions, phase changes of substances, and transport of substances and heat, are interrelated. It is known that it is difficult to burn solid fuel evenly because it is difficult to thoroughly mix the oxidizer with the gasified solid fuel and to maintain a uniform distribution of the burning rate.

[0065] Therefore, in the present invention, the discharge points generated inside the ignition device 100 can be generated successively around the entire inner circumference (discharge area), thereby making it possible to burn and retreat the solid fuel 400 evenly from the inside (the inner wall of the combustion port 500).

[0066] 1-3. Regarding the conduction of electricity to conductive materials in the ignition device Next, a configuration for applying a voltage to the first member 110 and the second member 120 of the ignition device 100, which are made of a conductive material, will be described with reference to FIG. FIG. 11 is a diagram showing an example of a method for applying electricity to the conductive members (first member and second member). FIG. 11(a) is a diagram showing an example of soldering a cable, and FIG. 11(b) is a diagram showing an example of using a metal plate to pass electricity.

[0067] Voltage application cables 601, 611 are laid through two ports, voltage application port 600 and voltage application port 610, and are connected to first member 110 and second member 120, which are made of a conductive material, respectively. The connections may be made by any means, such as soldering or embedding, as long as they can ensure electrical continuity. 11(b), the cables 601 and 611 may be connected via voltage application metal plates 602 and 612 that come into surface contact with the first member 110. Also, the cables 610 and 611 themselves may be made of metal plates.

[0068] 2. Ignition device configuration 2-1. Typical examples Next, a typical example of the ignition device of the present invention will be described with reference to FIG. FIG. 12 shows an example of a typical example of the ignition device 100, where FIG. 12(a) is a perspective view and FIG. 12(b) is a front view. First, FIG. 12(a) shows that the ignition device 100 is configured such that a first member 110 and a second member 120 made of a conductive material sandwich a third member 130 made of an insulating material.

[0069] In addition, a through hole is formed inside each member, and it is shown that the through hole 112 of the first member 110, the through hole 122 of the second member 120, and the through hole 132 of the third member 130 are each provided with approximately the same diameter (coaxially). Here, the inner periphery of the through hole 112 of the first member 110 is defined as the peripheral edge 115, the inner periphery of the through hole 122 of the second member 120 as the peripheral edge 125, and the inner periphery of the through hole 132 of the third member 130 as the peripheral edge 135.

[0070] Furthermore, if necessary, an inclined portion 116 may be provided on the upper surface of the first member 110, which may be shaped to facilitate the generation of a swirl in the flow of the oxidant or the efficient introduction of gas for discharging the exhaust gas after combustion. Furthermore, if necessary, a wiring groove 101 for passing a voltage application cable for applying a voltage to the second member 120 can be provided.

[0071] Note that, because a high voltage is applied to the cable for applying voltage to the second member 120, care must be taken with the arrangement and configuration of the wiring groove 101 to prevent inadvertent discharge due to proximity to the first member 110. For example, it is effective to remove part of the top surface 102 of the first member 110 around the wiring groove 101 and replace it with an insulating material, thereby ensuring a sufficient insulating distance from the cable for applying voltage to the second member 120.

[0072] FIG. 12(b) is a front view of the ignition device 100. Comparing this with the thickness of the peripheral portion 135 of the through hole 132 on the inside of the third member 130 in Figure 12(a) shows that by making the outside thickness of the third member 130 made of an insulating material thicker than the inside, the insulation distance between the first member 110 and the second member 120 is greater on the outside than on the inside. This prevents discharge from occurring outside the ignition device, and allows discharge to occur inside near the periphery of the through hole.

[0073] 2-2. Cylindrical configuration example Next, a modified example of the columnar shape of the first member 110 will be described with reference to FIG. 13A and 13B are diagrams showing an example of a modified ignition device 100 in which the configuration is modified to a substantially cylindrical shape, with FIG. 13A being a perspective view and FIG. 13B being a BB cross-sectional view. In the typical example of FIG. 12, an inclined portion 116 is provided, but in FIG. 13, no inclined portion is provided and the shape is modified to be flat. As shown in Figure 13(b), by providing a step portion 133 in the third member 130 and making the outer thickness of the third member 130 made of an insulating material thicker than the inner thickness, discharge does not occur outside the ignition device, but can occur near the periphery of the inner through hole.

[0074] 2-3. Cross-section of a typical example of an ignition device Next, the cross-sectional structure of a typical example of the ignition device 100 will be described with reference to FIG. 14A and 14B are cross-sectional views of a typical example of the ignition device 100, where FIG. 14A is a perspective view of the AA cross section, and FIG. 14B is a cross-sectional view of the BB cross section. As shown in Figures 14(a) and (b), by providing a step portion 133 in the third member 130 and making the thickness of the outer side 139 thicker than the thickness of the inner through-hole periphery 135 of the third member 130 made of an insulating material, discharge does not occur outside the ignition device, and discharge and ignition can be achieved between the inner through-hole periphery 115 of the first member 110 and the inner through-hole periphery 125 of the second member 120.

[0075] Furthermore, the discharge does not have to be limited to one location on the periphery of the through-hole, but can be generated sequentially in a discharge area 140 around the entire periphery of the through-hole. Therefore, when the ignition device of the present invention is used in a hybrid rocket, boundary layer combustion 731, 732 can be generated evenly around the entire circumference of combustion port 500, and solid fuel 400 can be burned and retreated evenly, as shown in FIG.

[0076] Furthermore, as shown by the inclined portion 116 in FIG. 14, in the typical example of the ignition device 100, the first member 110 has a tapered structure in which the thickness gradually decreases toward the inside. This structure generates a gas flow from the outside to the inside when an oxidizer or gas for discharging post-combustion gas is injected from above in the figure, and contributes to efficient introduction or discharge of gas through the swirl effect, etc. Furthermore, by making the thickness of the first member 110 increase as it goes outward, it contributes to adjusting the retreat speed of each of the first to third members when igniting and burning by discharge (details will be described later).

[0077] 2-4. Cross-sectional view of a modified ignition device (shape of the step portion) Next, an example in which the shape of the step portion is modified based on the typical example of the ignition device 100 will be described with reference to FIG. Figure 15 shows an example of a modified example in which the shape of the step portion 133 is modified based on a typical example of the ignition device 100, where Figure 15(a) is a perspective view of the AA cross section and Figure 15(b) is a BB cross section.

[0078] According to Figures 15(a) and (b), the insulating distance on the outside can be increased relative to the inside by replacing the step portion 133 of the third member made of an insulating material with a stepped step and making it have a tapered or curved shape in which the thickness changes. As described above, the typical example of the ignition device 100 is merely one example, and various configurations are possible as long as the outer insulation distance is ensured to be greater than the inner insulation distance.

[0079] 2-5. Cross-sectional view of a modified example of the ignition device (thickness of the peripheral portion of the through-hole of the first member) Next, an example in which the thickness of the first member near the periphery of the through-hole on the inside is modified based on the typical example of the ignition device 100 will be described with reference to FIG. Figure 16 shows an example of a modified example in which the thickness of the peripheral portion of the through hole of the first member is modified based on a typical example of the ignition device 100, where Figure 16(a) is an oblique cross-sectional view taken along line AA, and Figure 16(b) is a cross-sectional view taken along line BB.

[0080] 16(a) and 16(b) show that the inner thickness of the first member 110 is configured to be thicker at the deformed portion 117. In this way, the first member 110 can have a variety of configurations, and as long as it is possible to ensure that the outer insulation distance is greater than the inner insulation distance, various configurations can be used.

[0081] 2-6. Cross-sectional view of a modified example of the ignition device (inner thickness of the first member) Next, an example in which the shape of the inclined portion of the first member 110 is modified will be described with reference to FIG. Figure 17 shows an example of a modified example in which the shape of the inclined portion of the first member 110 is modified based on a typical example of the ignition device 100, where Figure 17(a) is a perspective view of the AA cross section and Figure 17(b) is a BB cross section.

[0082] 17(a) and 17(b) show that the thickness of the first member 110 is made thinner at the deformed portion 117. As shown in FIG. In this way, the first member 110 can have a variety of configurations, and as long as it is possible to ensure that the outer insulation distance is greater than the inner insulation distance, various configurations can be used.

[0083] As shown in FIG. 17(b), by adjusting the thickness of the first member 110 to be the same as or slightly thicker than the thickness of the second member 120, it is possible to adjust the retraction speed of the first member 110 upon discharge and ignition to be approximately equal to or slightly slower than the retraction speeds of the second member 120 to the third member 130 (details will be described later).

[0084] 2-7. Ignition device dimensions Next, the dimensions of each part of the ignition device 100 will be described with reference to FIGS. Fig. 18 is a B-B cross-sectional view of a typical example of the ignition device (Figs. 12 and 14), showing the dimensions of each part. Similarly, Figs. 19 to 21 are B-B cross-sectional views of the ignition devices of the embodiments of Figs. 15 to 17, respectively, showing the dimensions of each part. All of these figures show the dimensions of a typical example of the ignition device 100 and a modified version of the typical example, and since the dimensions are basically indicated by the same reference numerals, all of them will be described together.

[0085] First, the outer diameter of the ignition device 100 is represented by IG-L1, the inner diameter by IG-L2, and the thickness by IG-T1. The inner thickness of the first member 110 is expressed as P1-T1, the outer thickness as P1-T2, the thickness of the second member 120 as P2-T1, the inner thickness of the third member 130 as P3-T1, and the outer thickness as P3-T2. The width of the thick outer portion of the third member 130 is represented by P3-L1, and the width of the portion where the thickness decreases toward the inside to the periphery of the through-hole is represented by P3-L2.

[0086] Furthermore, the insulation distance between the first member 110 and the second member 120 on the inside is the same as the thickness P3-T1 of the inside of the third member 130, and is therefore expressed as GAPin. Similarly, the insulation distance between the first member 110 and the second member 120 on the outside is the same as the thickness P3-T2 of the outside of the third member 130, and is therefore expressed as GAPout.

[0087] As described above, by ensuring a sufficient outer thickness of the third member 130 made of an insulating material, the outer insulation distance (GAPout) between the first member 110 and the second member 120 can be ensured to be greater than the inner insulation distance (GAPin) near the periphery of the through hole. As a result, discharge does not occur outside the ignition device, but can occur inside near the periphery of the through hole.

[0088] The actual dimensions of each part can be freely set depending on the size of the hybrid rocket, the burning time, the size of the solid fuel depending on the application, etc. For example, if the total length of the hybrid rocket is about 50 to 400 mm, the diameter of the hybrid rocket can be set to about 25 to 200 mm, and the diameter of the solid fuel can be set to about 20 to 180 mm.

[0089] In this case, the outer diameter IG-L1 of the ignition device 100 can be set to about 20 to 180 mm, the inner diameter IG-L2 to about 5 to 40 mm, and the thickness IG-T1 to about 5 to 30 mm. The inner thickness P1-T1 of the first member 110 can be set to 3 to 25 mm, the outer thickness P1-T2 to 1 to 5 mm, and the thickness P2-T1 of the second member 120 to about 0.5 to 3 mm.

[0090] The inner thickness P3-T1 of the third member 130 can be set to about 1 to 3 mm, and the outer thickness P3-T2 can be set to about 4 to 25 mm. Furthermore, the width P3-L1 of the thick outer portion of the third member 130 can be set to 3 to 10 mm, and the width P3-L2 of the portion where the thickness decreases inward to the periphery of the through hole can be set to approximately 5 to 50 mm.

[0091] In the combustion experiments described below, the outer diameter IG-L1 of the ignition device 100 was set to about 90 mm to 145 mm. The thickness P2-T1 of the second member 120 was set to approximately 1 mm, the inner thickness P1-T1 of the first member 110 was set to approximately 11 mm, and the outer thickness P1-T2 was set to approximately 2 mm. The inner thickness P3-T1 (GAPin) of the third member 130 was set to approximately 2 mm, and the outer thickness P3-T2 (GAPout) was set to approximately 11 mm.

[0092] If the thickness of the inside of the third member 130 is too thin, discharge will occur in undesirable locations, such as near the middle between the through hole and the outside of the third member, rather than near the periphery of the through hole, so it is preferable that the thickness be at least about 1 mm to 3 mm. The width P3-L1 of the thick outer portion of the third member 130 was set to about 7 mm, and the width P3-L2 of the portion where the thickness decreases inward to the periphery of the through-hole was set to about 20 mm.

[0093] 2-8. Exploded view of the ignition device Next, the combination of the first member 110 to the third member 130 will be described with reference to an exploded view of the ignition device 100 (FIG. 22). FIG. 22 is an exploded view of a typical example of the ignition device 100 (FIGS. 12 and 14). FIG. 22 shows that the first member 110 and the second member 120 are configured to sandwich the third member 130 . Modified examples of the first member 110 are shown in Figures 13 and 15 to 17, modified examples of the second member 120 are shown in Figures 24 to 36, and modified examples of the third member 130 are shown in Figures 15 to 17, but these modified examples can also be used by combining the respective members, as in Figure 22.

[0094] In each member, peripheral portions 115, 125, 135 of the through holes are provided on the inside, and these come together to form a discharge area 140 on the inside. In addition, in order to generate a discharge, a voltage needs to be applied to the first member 110 and the second member 120, and a booster that boosts the voltage supplied from a power supply is connected to the first member 110 and the second member 120.

[0095] 12 to 17 and the cross-sectional views of FIGS. 18 to 22, the shape and structure of first member 110 are not limited to these, and any shape and structure may be used for other parts as long as the structure allows discharge to occur between periphery 115 of the inner through-hole and periphery 125 of the inner through-hole of second member 120. More specifically, when viewed in plan view, it is also possible to adopt a configuration similar to that of second member 120, as shown in FIGS. 24 to 36, for example.

[0096] Furthermore, the shape and structure of the third member 130 are shown in (b) of Figures 12 to 17 and the cross-sectional views of Figures 18 to 22, but it is sufficient that the third member 130 has a predetermined shape and structure to ensure insulation between the first member 110 and the second member 120, and other parts can have any shape and structure. More specifically, it is sufficient that the insulating distance securing portion 136 of the third member has a predetermined thickness, so that discharge does not occur in areas other than the periphery of the inner through-hole, and that the thickness of the outside 139 of the third member is greater than the thickness of the periphery 135 of the inner through-hole, and that other areas can have any shape.

[0097] 2-9. Examples of combinations of the first to third members that make up the ignition device Next, the combination patterns of the first member 100, the second member 120, and the third member 130 that constitute the ignition device 100 will be described with reference to FIG. FIG. 23 is a diagram showing that there is a degree of freedom in the combination of the first member 110, the second member 120, and the third member 130 that constitute the ignition device 100, and is a diagram showing an example of some modified examples. 23(a) shows a typical example in which a first member 110, a second member 120, and a third member 130 are combined. In this case, discharge is generated at the periphery (not shown) of the through-holes provided inside the first member 110 and the second member 120.

[0098] 23(b) shows an example in which two sets, one above the other, are provided, each combining a first member 110, a second member 120, and a third member 130. In this example, the second member 120 is shared between set A and set B. In this case, a voltage is applied between the first member 110 and the second member 120 of set A and / or set B. Then, a discharge is generated at the periphery (not shown) of the through-hole provided inside the first member 110 and the second member 120 of set A and / or set B (the discharge location is on the inside and is therefore not shown).

[0099] Figure 23(c) shows an example in which two sets of a first member 110, a second member 120, and a third member 130 are combined and provided one above the other, and is an example in which the second member 120 is prepared separately as set A and set B. In this case, a voltage is applied between the first member 110 and the second member 120 of set A and / or set B. Then, a discharge is generated at the periphery (not shown) of the through-hole provided inside the first member 110 and the second member 120 of set A and / or set B (the discharge location is on the inside and is therefore not shown). Although not shown, a plurality of sets of ignition devices, such as set C and set D, may be provided.

[0100] 3. Configuration of the second member 3-1. Example of the second member being plate-shaped When the second member 120 is plate-shaped, its outer shape pattern will be described with reference to FIGS. FIG. 24 is a diagram showing an example of the second member in the typical example of the ignition device 100 (FIGS. 12 and 14). FIG. 25 is a diagram showing a modified example of the second member 120, and is a diagram showing an example of an embodiment in which the outer periphery has a rectangular shape.

[0101] FIG. 26 is a diagram showing a modified example of the second member 120, and is a diagram showing an example of an embodiment in which the outer periphery has an octagonal shape. As shown in FIGS. 24 to 26, the outer shape of the second member 120 can take various shapes. Although the first member 110 and the third member 130 are not shown, their outer shapes can take various forms, similar to the second member 120 in FIGS.

[0102] 3-2. Example of a configuration in which multiple protrusions appear on the periphery of the through-hole on the inside of the second member Next, an example of an embodiment in which a plurality of protrusions appear on the periphery of the through-hole inside the second member 120 will be described. In order to make the protrusions appear on the inside of the member, it is preferable to provide a portion consisting of a plurality of lines, such as a lattice-like portion, and hollow out the inside of that portion. Furthermore, shapes made up of a plurality of lines may be lattice-like, spider web-like, honeycomb-like, spiral-like, or the like. Hereinafter, several patterns will be described with reference to FIGS.

[0103] (1) Example when the second member is lattice-shaped Figures 27 to 29 are diagrams showing modified examples of the second member, and are diagrams showing an example of an embodiment in which the part that burns and retreats due to discharge and ignition is made up of a lattice-shaped member, has a through-hole that is a circular hole cut out from the inside of the member, and has protrusions on the periphery of the through-hole. According to FIG. 27, the area extending from the outside to a certain extent inward is configured in a grid-like shape, and further inward there is shown a circular cutout shape. In this case, it can be seen that a protruding portion (protruding portion 126) is formed on the periphery 125 of the inner through-hole.

[0104] As will be described in more detail later, by providing the protrusion 126, it is possible to utilize the edge effect during discharge to generate a discharge phenomenon between the peripheral portion 115 of the through hole 113 on the inside of the first member 110 and the protrusion 126 formed on the peripheral portion 125 of the through hole 122 on the inside of the second member 120, and ultimately to generate a discharge phenomenon successively around the entire circumference of the peripheral portion 125 of the through hole 122.

[0105] FIG. 28 is a diagram showing a modified example of the second member of the embodiment of FIG. 27, and is a diagram showing an example of an embodiment in which the outer periphery has a rectangular shape. FIG. 29 is a diagram showing a modified example of the second member of the embodiment of FIG. 27, and is a diagram showing an example of an embodiment in which the outer periphery has an octagonal shape. In this way, various external shapes can be adopted.

[0106] (2) Example of the second member being spider web-shaped FIG. 30 shows a modified example of the second member 120, in which the part that burns and retreats due to discharge and ignition is made up of radial or spider web-like members, has a circular through-hole cut out from the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through-hole. In this case as well, it can be seen that a protruding portion (protruding portion 126) is formed on the periphery 125 of the inner through-hole 122. In this embodiment, various external shapes can be adopted, and therefore illustrations thereof are omitted.

[0107] (3) Modified example when composed of multiple lines In order to make the protrusions appear on the inside of the component, it is preferable to provide a section made up of multiple lines, such as a grid or spider web, and hollow out the inside of that section, but various other configurations can also be adopted. Each aspect will be described below with reference to FIGS.

[0108] First, FIG. 31 shows a modified example of the second member 120, in which the portion that burns and retreats due to discharge and ignition is made of a honeycomb-shaped member, has a circular through-hole cut out from the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through-hole. In this case as well, a protrusion 126 is formed on the periphery 125 of the inner through-hole 122, which is suitable for inducing a discharge phenomenon using the edge effect.

[0109] FIG. 32 shows a modified example of the second member 120, in which the portion that burns and retreats due to discharge and ignition is made up of a spiral member, has a circular through-hole cut out from the inside of the member, and has a protrusion on the periphery of the through-hole. In this case as well, a protrusion 126 is formed on the periphery 125 of the inner through-hole 122, which is suitable for inducing a discharge phenomenon using the edge effect.

[0110] FIG. 33 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made up of a triangular lattice-shaped member, has a circular through-hole cut out from the inside of the member, and shows an example of an embodiment in which a protrusion appears on the periphery of the through-hole. In this case as well, a protrusion 126 is formed on the periphery 125 of the inner through-hole 122, which is suitable for inducing a discharge phenomenon using the edge effect.

[0111] (4) Other examples The above has described an example in which a portion made up of a plurality of lines is provided and the inside of the portion is hollowed out to form the protrusion 126, but various other embodiments can also be adopted. Alternatively, as a means for forming a protruding shape on the periphery of the inner through-hole, for example, an embodiment as shown in FIG. 34 can be considered.

[0112] FIG. 34 shows a modified example of the second member, in which the portion that burns and retreats due to discharge and ignition is made up of a plurality of small-diameter circular holes, and the member has a through-hole that is a circular hole cut out from the inside, with protrusions appearing on the periphery of the through-hole. In this case as well, a protrusion 126 is formed on the periphery 125 of the inner through-hole 122, which is suitable for inducing a discharge phenomenon using the edge effect. Although not shown, it is also possible to provide a plurality of polygonal small holes including triangular and rectangular small holes, or a plurality of star-shaped small holes.

[0113] 3-3. Regarding the pattern of the periphery of the inner through-hole (1) Modification of the peripheral edge of the through hole when the second member is in a plate-like form Next, a modified example of the periphery of the through-hole when the second member is in a plate-like form will be described with reference to FIG. Figure 35 is a diagram showing a modified example of the peripheral portion of the through hole of the second member in the embodiment of Figure 24, and shows that there is a degree of freedom in the configuration of the peripheral portion of the inner through hole, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares and octagons, stars, fractals, etc.

[0114] In short, the idea is that it is sufficient that there is at least one through hole on the inside and the thickness of the third member made of insulating material is configured to be thicker on the outside, so that a discharge phenomenon can occur around the periphery of the inner through hole. Although the embodiment shown in FIG. 35 has been described with a circular outer shape as an example, the outer shape can take various shapes as shown in FIGS.

[0115] (2) Modification of the periphery of the through hole when the second member is lattice-shaped Next, a modified example of the periphery of the through-hole when the second member has a lattice shape will be described with reference to FIG. Figure 36 is a diagram showing a modified example of the peripheral portion of the through hole of the second member in the embodiment of Figure 27, and shows that there is a degree of freedom in the configuration of the peripheral portion of the inner through hole, and various configurations can be adopted, such as multiple small-diameter circles, polygons such as squares, pentagons, and octagons, and stars. In Figure 36, an example of a lattice-shaped second member is shown, but similarly, in various embodiments in which protrusions appear on the inside (Figures 27 to 34), the shape of the peripheral edge of the inner through hole can take various shapes.

[0116] 4. Discharge area 4-1. Discharge area when the second member is plate-shaped Next, the significance of the discharge location and discharge area when the second member is in a plate-like form (such as in FIG. 24) will be described with reference to FIG. Figure 37 is a cross-sectional view taken along the line AA, showing that when a plate-shaped second member is used, the third member of the ignition device is configured so that the thickness of the outer side 139 is greater than the thickness of the inner side, causing discharge to occur around the periphery of the through-hole on the inner side of each member. Here, the up and down arrows indicate the discharge locations.

[0117] According to Figure 37, since the insulation distance (GAPout) on the outside 139 of the third member is larger than the insulation distance (GAPin) on the inside, discharge does not occur on the outside (see the instructions in Comment 37-1), but occurs between the peripheral portion 115 of the through hole 112 on the inside of the first member 110 and the peripheral portion 125 of the through hole 122 on the inside of the second member 120.

[0118] Furthermore, the discharge point (up and down arrows) is not one location, but rather indicates that discharges occur successively in the discharge area (Discharge Area) 140 around the entire periphery of the through hole due to repeated charging and discharging of the electric charge by the igniter during the time the current is applied. The order in which the discharges occur is random, and as a result, discharges occur one after another in the discharge area 140 around the entire periphery of the through-hole.

[0119] 4-2. In the case where a protrusion is provided on the inside of the second member Next, the significance of the discharge location and discharge area in the case where the second member has a protrusion on the inside (such as in FIG. 27) will be described with reference to FIG. Figure 38 is a cross-sectional view taken along the line AA showing that when a configuration is used in which a protrusion is provided on the inside of the second member, by configuring the thickness of the outside 139 of the third member of the ignition device to be thicker than the thickness of the inside, discharge occurs around the periphery of the through hole on the inside of each member.

[0120] FIG. 38 shows that, similar to FIG. 37, the insulation distance (GAPout) on the outside 139 of the third member is greater than the insulation distance (GAPin) on the inside, causing discharge to occur inside the member. It is also shown that due to the edge effect in the discharge phenomenon, discharge occurs between the inner protrusion 126 of the second member and the edge of the periphery 115 of the through-hole 113 of the first member. Furthermore, it is shown that the discharge locations (up and down arrows) are not one location, but occur successively in a discharge area 140 around the entire periphery of the through-hole.

[0121] 5. Discharge (ignition) and combustion progress in the discharge area around the entire inner periphery of the component 5-1. When the second member is plate-shaped Next, the progress of discharge (ignition) and combustion in the discharge area around the entire inner periphery of the member will be described with reference to FIG. 39 is a plan view showing that when a plate-shaped second member is used, multiple ignitions cause successive discharges around the entire periphery of the inner through-hole, causing the first and third members to retreat evenly from the inside. Note that the first and third members also retreat in the same way as the second member, but are not shown in the figures.

[0122] According to Figure 39, discharge (ignition) and combustion progress in the discharge area around the entire inner periphery of the member for the first discharge (ignition) (t1), second discharge (t2), etc., and as the discharge (ignition) and combustion progress, by the nth discharge (ignition) (tn), the peripheral portion 125 of the through hole 122 on the inner side of the second member 120 is shown to retreat evenly. In this way, the discharge (ignition) points move one after another, and discharge (ignition) can be generated along the entire inner circumference of the component, so boundary layer combustion can also occur evenly around the entire circumference, allowing the solid fuel to burn and retreat evenly.

[0123] Depending on conditions such as the thickness of each component and the flow of the oxidizer, some parts may retreat earlier than other parts, but even in this case, by performing multiple discharges (ignitions), it is possible to eventually make the solid fuel retreat evenly around the entire circumference of the through hole inside the component. Therefore, even if the solid fuel retreats partially, it is possible to burn and retreat evenly.

[0124] 5-2. In the case where a protrusion is provided on the inside of the second member When a configuration is used in which a protrusion is provided on the inside of the second member, the manner in which discharge (ignition) and combustion progress in the discharge area around the entire inside of the member will be explained using Figures 40 and 41. Figure 40 is a plan view showing that when a grid-shaped projection is used as an example of a configuration in which the second member has a projection on the inside, multiple ignitions cause discharges to occur successively around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the first member or the third member also retreats in the same way, but this is not shown in the figure. The first member or the third member also retreats in the same way, but this is not shown in the figure.

[0125] 41 is a plan view showing that when a spider web-shaped projection is used among the projections provided on the inside of the second member, multiple ignitions cause discharges to progress sequentially around the entire periphery of the inner through-hole, causing the second member to retreat evenly from the inside. Note that the first member and third member also retreat in the same way as the second member, but are not shown in the figure.

[0126] As described above, according to the present invention, it is understood that discharge (ignition) and combustion progress successively in the discharge area around the entire periphery of the inner surface of the member, with the first discharge (ignition) (t1), the second discharge (t2), etc. It is also understood that once discharge (ignition) and combustion have progressed to a certain extent, by the nth discharge (tn), it is possible to evenly retract the periphery 125 of the through-hole 122 inside the second member 120. In this way, the discharge (ignition) points move one after another, and discharge (ignition) can be generated all around, so boundary layer combustion can also occur evenly all around, allowing the solid fuel to burn and retreat evenly.

[0127] 6. Regarding discharge in the discharge area when the first member is in the form of Fig. 14 and the second member is in the form of Fig. 24 (the form in which the inside is composed of a continuous line or surface)

[0128] 6-1.B-B cross section showing how each component recedes due to discharge (ignition) In Chapter 5, we used a plan view from above to show how the parts retreat evenly from the inside due to discharge (ignition), but in this section we will use a B-B cross-sectional view from the side to show how the parts retreat evenly from the inside due to discharge (ignition).

[0129] Figure 42 is a B-B cross-sectional view showing how each component retracts due to multiple ignitions when the ignition device has an outer shape as shown in Figures 14 to 16, when the second component has a plate-like shape as shown in Figures 24 and 35, or when the second component has a protrusion on the inside as shown in Figures 27, 30 to 34, and 36. Figure 42 shows that the first discharge (ignition) (t1), the second discharge (t2), etc., discharge (ignition) and combustion occur one after another in the discharge area around the entire inner periphery of the component, and as the discharge (ignition) and combustion progress, each component retreats (after t1, t2, etc.).

[0130] Here, for example, at t1, since the third member 130 is formed of an insulating material, even if a voltage is applied to the first member 110 and the second member 120, no discharge occurs inside the third member (see the instructions in Comment 42-1), but a discharge occurs near the edge portion of the periphery of the through hole inside the first member 110 and the second member 120 (in a gas or in a vacuum in the case of outer space). Then, a spark is generated by the discharge (ignition), and in combination with the oxidizer 710, the first member 110, the second member 120, and the third member 130 are combusted, generating an initial flame (not shown).

[0131] Because the initial flame has more momentum the further downstream it is in relation to the direction of oxidizer flow, the third member 130 and the second member 120 tend to retreat slightly more than the first member 110. The word "tends to" is used because the regression speed of each component varies depending on the thickness and material of the first component 110, the third component 130, and the second component 120, and also varies depending on the flow rate and velocity of the oxidizer.

[0132] Furthermore, in the case of arc discharge, the cathode side tends to have a higher temperature than the anode side (the cathode side retreats faster), so the retreat speed can be adjusted depending on whether the first member 110 or the second member 120 is used as the cathode. In FIG. 42, an example is shown in which the first member 110 is configured to be thicker than the other members, so the retraction speeds of the third member 130 and second member 120 are slightly faster.

[0133] 6-2. Mechanism for generating discharge around the entire periphery of the through-hole Next, the mechanism by which discharge is generated all around the periphery of the through-hole and the member is uniformly retracted will be described with reference to FIGS. 6-2-1. Discharge phenomenon in the discharge area when the second member has a plate-like shape as shown in Figures 24 and 35 For example, if the thickness of the second member 120 is made thinner than the thickness of the first member 110, the second member will move back more easily, and the retraction speed of the second member 120 will tend to be slightly faster. This is shown in Figure 43. FIG. 43(a) is a diagram showing the state of each part before discharge (t0), with the left side being a cross-sectional view taken along line AA and the right side being a cross-sectional view taken along line BB. FIG. 43(b) is a diagram showing the state of each part after the first discharge has finished (after t1), with the left side being a cross-sectional view taken along line AA and the right side being a cross-sectional view taken along line BB.

[0134] The first discharge refers to the occurrence of one or more arc discharges, including multiple single discharges. This occurs when the igniter's ON / OFF switch (described below) is turned ON, causing a single discharge to occur, and during the specified time that the igniter is ON, multiple cycles of charge ⇒ discharge ⇒ charge ⇒ discharge... are repeated.

[0135] Figure 43(c) is a diagram showing that when the discharge has progressed to a certain extent (nth discharge), if the retreat speed of the second member 120 is faster than the retreat speed of the first member 110, the shortest distance (GAPtn-vertical) between the second member 120 and the first member 110 is shorter than the distance (GAPtn-edge) between the edge of the peripheral portion 115 of the through hole 112 of the first member 110 and the edge of the peripheral portion 125 of the through hole 122 of the second member 120.

[0136] As shown in Figures 43(a) and (b), if we define the insulation distance inside the first member 110 and the second member 120 before discharge (ignition) (t0) as GAPt0 and the insulation distance after the first discharge (ignition) (after t1) as GAPt1, it can be seen that GAPt1 > GAPt0. In such a case, the area where discharge has occurred will remain in a state where discharge is less likely to occur than the area where discharge has not yet occurred (while the discharge is suspended from advancing further outward from the area where discharge has already occurred 119, 129), and discharge will continue all around the inner area where discharge has not yet occurred, allowing for uniform retreat. See Figures 39 to 41.

[0137] This is an effect not found in the prior art, and we have decided to call this discharge area around the entire periphery of the inner through hole the "Discharge Area 140" to express the difference from the prior art. As a result, the ignition device of the present invention makes it possible to ignite the entire periphery of the through hole, generating an initial flame all around, and ultimately generating boundary layer combustion all around the solid fuel, making it possible to evenly retreat the solid fuel from the inside (see Figure 7). At the same time, there is also the advantage that the output can be made uniform.

[0138] Next, the mechanism by which discharge due to the edge effect occurs in preference to discharge at a location with a shorter insulation distance will be explained further using Figure 43(c). Here, the edge effect in the discharge phenomenon refers to a phenomenon in which, when there are sharp or uneven parts, the electric field strength is high at the convex parts, and discharge is concentrated at these parts.

[0139] The peripheries (edge ​​portions) of the through holes on the inside of the first member 110 and the second member 120 are each sharp or convex, and therefore susceptible to the edge effect caused by the discharge phenomenon. As shown in Figure 43(c), if the retreat speed of the first member 110 is slower than the retreat speed of the second member 120, the shortest gap (GAPtn-vertical) between the first member 110 and the second member 120 will be a distance equal to the thickness of the third member 130.

[0140] On the other hand, the gap (GAPtn-edge) between the edge portion of the periphery of the innermost through hole of the first member 120 and the edge portion of the innermost protrusion of the second member has the relationship (GAPtn-vertical)<(GAPtn-edge), and (GAPtn-edge) tends to be slightly larger.

[0141] In this case, when a voltage is applied between the first member 110 and the second member 120, it appears at first glance that a discharge occurs in the shortest distance (GAPtn-vertical) (between Inside1 and Edge2). However, as described above, due to the edge effect of the discharge phenomenon, the electric field strength is greater in the (GAPtn-edge) portion than in the shortest distance (GAPtn-vertical) portion, so a discharge occurs in the (GAPtn-edge) portion (between Edge1 and Edge2) despite the relatively large insulation distance. As a result, there is no bias in the locations where discharge occurs, and some parts do not retreat toward the outside 119, 129, and after discharge occurs around the entire periphery of the inner through-hole, the (component) can be retreated evenly toward the outside in sequence.

[0142] Depending on conditions such as the thickness of each component and the flow of the oxidizer, some parts may retreat earlier than other parts, but even in this case, by performing multiple discharges (ignitions), it is possible to eventually cause the solid fuel to retreat evenly around the entire periphery of the through-hole. Therefore, even in such cases, it is possible to burn and retreat the solid fuel evenly.

[0143] Furthermore, depending on conditions such as the thickness of each component and the flow of the oxidizer, it is possible that the first component does not retreat and only the second component 120 and the third component 130 retreat. In this case, the relationship GAPtn-edge >> GAPtn-vertical holds in Figure 43(c), and discharge occurs mainly between the edge portion (Edge2) of the periphery of the through-hole on the inside of the second component and the plane (Inside1) of the first component directly above, i.e., GAPtn-vertical.

[0144] Even in such a case, as shown in FIG. 7, the location where discharge (ignition) occurs and initial flame 720 is generated remains directly above the solid fuel, and there is no effect on the subsequent occurrence of boundary layer combustion of the solid fuel. Then, by repeating the discharge (ignition), the discharge eventually progresses over the entire circumference of the second member, so that the solid fuel can be burned and retreated evenly.

[0145] 6-2-2. Regarding discharge in the discharge area when the second member has a structure with gaps, such as a grid or line combination shape, or a combination of many small circles, triangles, or diamonds, as shown in Figures 27, 30 to 34, and 36, and has protrusions on the inside

[0146] For example, if the thickness of second member 120 is thinner than that of first member 110, or if the shape of second member 120 is a structure with gaps rather than a surface, such as a lattice shape or a combination of lines, for example, as shown in Figures 27 to 34 and 36, the second member tends to retreat more easily, and the retreat speed of second member 120 tends to be slightly faster. This state is shown in Figure 44.

[0147] Figures 44(a) and (b) show that if a discharge occurs at protrusion 1 (126-1), the insulation distance (GAPt1) between the edge of the periphery of the through hole in the first member 110 and protrusion 1 (126-1) at the periphery of the through hole in the second member will be larger than the insulation distance (GAPt0) between protrusions 2 to n (126-2 to 126-n) where no discharge has yet occurred and the edge of the periphery of the through hole in the first member 110.

[0148] As a result, discharges occur randomly one after another between the protrusions 2 to n (126-2 to 126-n) where discharge has not yet occurred and the edge of the peripheral portion of the through hole of the first member 110, and the second member 120 retreats evenly from the inside toward the outside 129. In other words, the recession does not progress outward in some areas, but rather discharges occur one after another until discharge is completed around the entire periphery of the inner through-hole, and once one circumference of discharge is completed, discharge begins on the outer circumference, so that the recession proceeds evenly from the inside to the outside.

[0149] As shown in Figures 44(a) and (b), if the insulation distance inside the first member 110 and the second member 120 before (t0) the discharge (ignition) is GAPt0 and the insulation distance after (after t1) the first discharge (ignition) is GAPt1, it can be seen that GAPt1 > GAPt0.

[0150] In such a case, the area where discharge has occurred will remain less susceptible to discharge than areas where discharge has not yet occurred, and discharge will continue all around the inner area where discharge has not yet occurred. This makes it possible to ignite the entire periphery of the through hole, generating an initial flame all around, and ultimately causing boundary layer combustion to occur all around the solid fuel, making it possible to cause the solid fuel to retreat evenly (see Figures 40 and 41).

[0151] Figure 44(c) shows that when the discharge has progressed to a certain extent (nth discharge), if the retreat speed of the second member 120 is slightly faster than the retreat speed of the first member 110, the shortest distance (GAPtn-vertical) between the second member 120 and the first member 110 becomes slightly shorter than the distance (GAPtn-edge) between the edge of the peripheral portion 115 of the through hole 113 of the first member 110 and the edge of the "protrusion portion 126-1 to n" of the peripheral portion 125 of the through hole 122 of the second member 120.

[0152] In this case, when a voltage is applied between the first member 110 and the second member 120, it appears at first glance that a discharge occurs in the part with the shortest distance (GAPtn-vertical) (between Inside1 and Edge2). However, as described above, due to the edge effect of the discharge phenomenon, the electric field strength is greater in the part with the shortest distance (GAPtn-edge) than in the part with the shortest distance (GAPtn-vertical), so a discharge occurs in the part with the shortest distance (GAPtn-edge) (between Edge1 and Edge2) despite the large insulation distance.

[0153] In particular, since a protrusion is formed on the periphery of the inner through-hole of the second member 120, the edge effect is enhanced compared to the plate-shaped case, and therefore discharge can be reliably generated between the protrusion 126 (Edge 2) of the inner through-hole of the second member 120 and the periphery (Edge 1) of the inner through-hole of the first member 110. As a result, there is no bias in the locations where discharge occurs, and some parts do not retreat partially outward, and after discharge occurs around the entire periphery of the inner through-hole, the (component) can be retreated evenly toward the outside in sequence.

[0154] 6-2-3. When the inner thickness of the first member is close to the thickness of the second or third member, how each member recedes due to discharge (ignition) as seen from the B-B cross section.

[0155] Next, using Figure 45, we will explain how each component retracts when a first component 110 having an inner thickness close to the thickness of the third component 130 is used, as in Figures 17 and 21, and a second component 120 such as that in Figures 24 to 36 is used. FIG. 45 is a BB cross-sectional view showing how the first member, whose inner thickness is close to that of the third member, moves backward due to multiple ignitions.

[0156] Figure 45 shows that the first discharge (ignition) (t1), second discharge (t2), etc., discharge (ignition) and combustion progress in the discharge area around the entire inner periphery of the component, and each component retreats (after t1, t2, etc.). Furthermore, it can be seen that FIG. 45 shows that the difference in retraction speed between the first member 110 and the second member 120 to the third member 130 is smaller than in the case of FIG. This is because, as shown in FIG. 45, when the thickness of the first member 110 is close to the thickness of the second member 120 or the third member 130, the first member 110 can be burned in the same way as the other members, and the difference between the retreat speed of the first member 110 and the retreat speed of the other members can be reduced.

[0157] In this case as well, the relationship GAPt1>GAPt0 holds true, as in the explanation of FIGS. 43 and 44 (not shown). In other words, in the area where discharge has occurred, it will remain difficult for discharge to occur compared to areas where discharge has not yet occurred (while the discharge will not spread further outward from the area where discharge has already occurred). Therefore, discharge continues all around the circumference at the more inner locations where discharge has not yet occurred, causing the electrode to retreat evenly. ⇒See Figures 39 to 41.

[0158] 7. Physical properties of the conductive materials of the first and second components Next, the physical properties of the first member 110 and the second member 120 made of a conductive material will be described. The conductive material used for the first member 110 and the second member 120 is preferably a material that burns and retreats due to discharge (ignition) (see FIG. 7). On the other hand, in order to function as a substitute for an electrode, it is required to have conductivity within a moderate range of resistance value. Furthermore, since the device is placed in a high-temperature environment, it is desirable that the device has a certain level of heat resistance.

[0159] Conductive materials generally refer to materials with a surface electrical resistance of 10^3 to 10^5 Ωm or less in volume resistivity. In the case of plastics and resins, the electrical resistance can be reduced by kneading in powdered conductive substances such as carbon or coating the surface with a material that allows electricity to pass through easily, allowing them to be used as conductive materials. In the present invention, materials in which powdered conductive substances such as carbon are kneaded into plastic or resin, as well as conductive polymers or intrinsically conducting polymers (ICPs), etc. can be used. Conductive polymers are polymeric compounds with high electrical conductivity. Typical examples include polyacetylene and polythiophenes.

[0160] The physical properties of the conductive polymer used in the experiment are shown in FIG. FIG. 46 is a diagram showing an example of characteristics when a conductive polymer is used as the conductive material. In Figure 46, PLA is an abbreviation for Poly-Lactic Acid, which refers to a resin material called polylactic acid. It can be made from plant-derived plastic materials such as starch found in corn and potatoes.

[0161] Here, it is desirable that the conductive material used for the first member 110 and the second member 120 is a material that burns and retreats due to discharge (ignition), so PLA is used as the base material, but this is not limited to this and other resin materials can be used as the base as long as they are flammable. It is also desirable to include a conductive material such as carbon (carbon-based material) to give the material electrical conductivity with a volume resistivity of 30 to 115 (Ω·cm). Furthermore, it was confirmed that the melting point is approximately 155°C, making it suitable for use in high-temperature environments. Other physical properties are as shown in FIG. 46, and therefore will not be described here.

[0162] The first member 110 and the second member 120 may be formed by layering using a 3D printer, or by creating a mold and pouring raw materials into it, for example. The volume resistivity when 3D printed using a 3D printer differs when viewed in the XY layer direction (horizontal direction) and when viewed in the Z layer direction (vertical direction), and the values ​​are as shown in Figure 46.

[0163] 8. Physical properties of the insulating material of the third component The third member 130, which is made of an insulating material, is a member for insulating the first member 110 and the second member 120. By adjusting the thickness and material of the third member 130, it is possible to cause discharge at a desired location (such as the periphery of the inner through-hole) and to prevent discharge from occurring at locations other than the desired location (such as a location closer to the outer side 129 than the periphery of the through-hole) (see the portion indicated by Comment 42-1 in FIG. 42).

[0164] Here, "a portion in a direction approaching the outer side of the periphery of the through-hole" means a portion in a direction away from the center of the member and approaching the outer side (129, etc.) of the member. Furthermore, when a voltage is applied between the first member 110 and the second member 120 and the first member 110 and / or the second member 120 combusts due to discharge (ignition), the third member 130 also combusts and desirably retreats together (see the explanation of Figure 7, Figure 10, etc.).

[0165] Moreover, it is desirable that the third member 130 retreats together with the solid fuel 400 as it retreats (see the description of FIG. 7, FIG. 10, etc.). In order to achieve this effect, the third member 130 can be made of a material as shown in FIG. As shown in Figure 47, materials that can be used include, for example, HDPE (high density polyethylene), ABS (ABS resin), TPU (thermoplastic polyurethane elastomer), POM (polyacetal resin), PMMA (acrylic resin), and PC (polycarbonate). Both have a volume resistivity exceeding 10 to the 14th power (Ω·cm) and a dielectric breakdown strength exceeding 14 (KV / mm), demonstrating sufficient insulating performance. Other physical property values ​​are as shown in FIG. 47, and therefore description thereof will be omitted.

[0166] However, since it is used in the ignition device of a hybrid rocket, it will be exposed to a high-temperature environment due to discharge (ignition) and combustion, so it is desirable to determine the material of the third member 130 from the perspective of a certain degree of heat resistance and appropriate arc resistance.

[0167] Here, the arc resistance refers to the time from when tracking occurs until the arc is extinguished. More specifically, when an arc is generated on the surface of a resin, the high temperature causes the resin to decompose and carbonize. This phenomenon first occurs near the electrodes, and eventually the carbide becomes a conductive path between the electrodes (called arc tracking), causing the arc discharge to disappear. Arc resistance refers to the time it takes for this tracking to occur and the arc to disappear.

[0168] In the present invention, when the first member 110 and / or the second member 120 burns due to discharge (ignition), it is desirable that the third member 130 also burns and retreats together, so materials such as HDPE (high density polyethylene) and ABS (ABS resin), which have a good balance between a moderate range of melting point and a moderate range of arc resistance, are suitable.

[0169] 9. Combustion Experiment 9-1.System Configuration Next, the configuration of a combustion experiment system for measuring the performance of the ignition device of the present invention will be described with reference to FIG. FIG. 48 is a diagram showing an example of a system configuration for a combustion experiment. A booster is connected to the ignition device 100 so that a predetermined voltage can be applied. The power supply is provided with an ON / OFF switch so that the voltage application to the ignition device 100 can be turned ON / OFF manually or by a sequencer or the like.

[0170] The oxidizer tank stores oxidizers such as nitrous oxide and liquid oxygen. Nitrous oxide can be self-pressurized, so there is no need for a pressure pump. By controlling each valve with a control device, the oxidizer pressure can be controlled with the main valve, and the oxidizer can be precisely switched on and off with the throttling valve. A purge tank is a tank for storing gas to discharge exhaust gases after combustion.

[0171] 9-2. Ignition sequence for combustion experiments Next, the ignition sequence of the combustion experiment of the ignition device of the present invention will be described with reference to FIG. In Figure 49, the igniter (Arc Ignitor) refers to the entire combination of the power supply, booster, and ON / OFF switch in Figure 48, and refers to a device that controls the ON / OFF of discharge (ignition) by applying voltage to the ignition device.

[0172] In Figure 49(a), the main valve is left open starting from 0 seconds on the time axis. In addition, the oxidizer throttle valve is set to open only one rotation between 0 and 10 seconds. This mode is called "Throttling Slow mode" because the throttle valve opens slowly, and is indicated by "*1" in Figure 49.

[0173] After that, I try to open it for nine rotations within 10 to 20 seconds. This mode is called "Throttling Fast mode" because it opens the throttle valve quickly, and is indicated by "*2" in Figure 49. For this reason, it will be fully open from 20 seconds onwards. The igniter is turned on for only 0 to 10 seconds. While the voltage application is turned on, discharge (ignition) occurs multiple times as appropriate.

[0174] In Figure 49(b), the oxidizer throttling valve is opened by only one rotation between 0 and 10 seconds (*1 Throttling Slow mode). After that, it is shown that it is opened for nine rotations from 10 to 20 seconds (※2 Throttling Fast mode), and then it is left fully open from 20 seconds onwards (up to this point it is the same as Figure 49(a)).

[0175] On the other hand, the igniter is turned on for only 0 to 5 seconds. In this way, if the solid fuel is already burning with a flame, the burning state can be maintained even if the igniter is turned off. When the igniter is turned on for a certain period of time, one discharge (ignition) occurs when the charge is sufficiently charged, and once one discharge (ignition) is completed, the next charge begins, causing a second discharge (ignition), and thereafter, multiple discharges (ignitions) and charges are repeated while the igniter is turned on.

[0176] As described above, the ON / OFF of the solid fuel combustion can be controlled by turning the throttle valve and / or igniter ON / OFF. In the following description, the experimental results of the ignition device of the present invention will be shown as data obtained when ignition and combustion are performed according to the sequence shown in FIG. 49(a).

[0177] 9-3. Combustion experiment data Next, the pressure data before and after the throttle valve when ignition and combustion are performed in the sequence of FIG. 49(a) will be explained using FIG. 50 is a diagram showing an example of the results of a combustion experiment, showing the values ​​of pressure sensors P (Pressure sensors) before and after the throttle valve. Nitrous oxide (liquid) was used as the oxidizing agent.

[0178] Throttling long slow corresponds to a state in which the throttle valve is slowly opened by one rotation between 0 and 10 seconds, at which the oxidizer pressure is approximately 2.8 MPa and the flow rate is approximately 24 g / s. Fast throttling corresponds to a state in which the throttle valve is quickly opened nine times in 10 to 20 seconds, with an oxidizer pressure of approximately 4.5 MPa and a flow rate of approximately 40 g / s. Full Open corresponds to the throttle valve being fully open, and the difference in pressure before and after the throttle valve indicates the pressure loss caused by the throttle valve.

[0179] 9-4. Changes in chamber pressure Next, the transition of the pressure inside the chamber will be explained using FIG. FIG. 51 shows an example of the transition of the pressure inside the chamber in a combustion experiment. Here, chamber 90 refers to the space immediately after passing through the oxidizer inlet of the hybrid rocket, as shown in Figure 48, and the pressure inside the chamber can be measured by the value of pressure sensor P (pressure sensor) immediately after the throttling valve. According to Figure 51, when the throttle valve is in the long slow position (when the throttle valve is opened only one full rotation), the pressure inside the chamber is in a negative pressure state.

[0180] Additionally, when throttling fast (throttling valve is opened 9 times), the pressure inside the chamber gradually increases and continues to rise until the main valve is closed, reaching approximately 0.15 MPa. According to Figure 51, in this experiment, the main valve was closed and nitrogen purging started when a flame was seen from the combustor nozzle, so the measurement ended while the pressure inside the chamber was still rising (at the point marked "Main Valve shutdown"). When the pressure inside the chamber is measured until it is saturated, the pressure is approximately 0.3 MPa.

[0181] 9-5. Combustion experiment results Finally, how the second member 120 and the solid fuel 400 retreated as a result of the combustion experiment of the present invention will be described with reference to FIG. FIG. 52 is a diagram showing an example of the results of a combustion experiment, illustrating the retreat of each part of the ignition device and hybrid rocket after multiple discharges (ignitions). The third member 130 is retracted in substantially the same manner as the second member 120, and is therefore not shown in the drawings.

[0182] FIG. 52(a) is a diagram showing the state of the second member before combustion. FIG. 52(b) is a diagram showing the state in which the second member 120 and the solid fuel 400 retreat after multiple ignitions have been performed. FIG. 52(c) shows the retreat of the solid fuel after multiple ignitions. FIG. 52(d) is a diagram showing the retreat of the solid fuel after multiple ignitions, as viewed from a slightly oblique direction.

[0183] Comparing Figures 52(a) and (b) reveals that the second member 120 is uniformly recessed from the inside all around. 52(c) and (d), it can be seen that the solid fuel 400 or the combustion port 500, like the second member 120, is uniformly recessed from the inside.

[0184] 10.Summary As described above, according to the present invention, by adopting an ignition method that utilizes the discharge phenomenon caused by arc discharge, it is possible to provide an ignition device that consumes significantly less power than a heating method. Furthermore, by using a structure that generates arc discharges successively around the entire periphery of the through hole inside the ignition device, it is possible to make the ignition device itself retreat evenly from the inside, and also to make the solid fuel retreat evenly from the inside. Furthermore, it enables stable output even after multiple ignitions. [Industrial Applicability]

[0185] The ignition device of the present invention is suitable as an ignition device for hybrid rockets, but can also be used as an ignition device for other types of rockets. Furthermore, it can be used in a variety of applications, not just rockets, such as those requiring multiple solid fuel combustions. [Explanation of symbols]

[0186] 1 Hybrid rocket 20 Discharge point 90 Chambers 100 Ignition system 101 Wiring groove 110 First member 112 through hole of first member 115 Peripheral edge of through hole of first member 116 Inclined portion of first member (optional) 117 Deformed part of the first member 119 Outside (outer periphery) of first member 120 Second member 122 through hole of second member 125 Peripheral edge of through hole of second member 126 Protrusions (multiple) 129 Outside (periphery) of second member 130 Third member 132 Through hole of third member 133 Step 135 Peripheral portion of through hole of third member 139 Outside (periphery) of third member 140 Discharge Area 200 cases 300 Insulation 400 solid fuel 500 Combustion Port 600 Voltage application port 601 Voltage application cable 602 Voltage application sheet metal 610 Voltage application port 611 Voltage application cable 612 Voltage application sheet metal 700 Oxidizer Port 710 Oxidizing Agents 720 Initial flame (pilot flame) 731 Boundary Layer Combustion 732 Boundary Layer Combustion 800 nozzles 810 Nozzle insulation

Claims

1. 1. An apparatus for igniting solid fuel, comprising: a first member made of a conductive material and having a through hole therein; a second member made of a conductive material and having a through hole therein; a third member provided between the first member and the second member, having a through hole therein, and made of an insulating material for insulating the first member from the second member; The third member is shaped so that the outer thickness is greater than the inner thickness, and the inner insulation distance is made smaller than the outer insulation distance of the third member, When a voltage is applied between the first member and the second member, generating a discharge phenomenon between the first member and a periphery of the through hole inside the second member; An ignition device characterized by:

2. 2. The ignition device according to claim 1, When a voltage is applied between the first member and the second member, A discharge phenomenon is generated between the first member and a peripheral portion of the through hole inside the second member, and By generating a discharge phenomenon between the first member and the periphery of the through hole inside the second member in a discharge area over the entire periphery of the through hole due to multiple discharges, uniformly retracting the second member, the third member, or / and the first member from the inside; An ignition device characterized by:

3. 3. The ignition device according to claim 2, The three-dimensional shape of the first member is a shape in which the thickness increases from the inside to the outside. An ignition device characterized by:

4. The ignition device according to any one of claims 1 to 3, The second member is plate-shaped, and the shape of the periphery of the inner through hole is One or a combination of circular, polygonal, star, and fractal shapes; When a voltage is applied between the first member and the second member, generating a discharge phenomenon between the first member and a peripheral portion of the through hole inside the second member; An ignition device characterized by:

5. The ignition device according to any one of claims 1 to 3, The shape of the second member is A shape in which a plurality of protrusions appear on the periphery of the inner through-hole, such as a lattice shape, a spider web shape, a honeycomb shape, a spiral shape, a combination of triangles, a combination of a plurality of small diameter holes, or any other shape, When a voltage is applied between the first member and the second member, generating a discharge phenomenon between the first member and any one of the plurality of protrusions on the periphery of the through hole inside the second member; An ignition device characterized by:

6. The ignition device according to any one of claims 1 to 3, The conductive material used for the second member includes at least one of a conductive polymer, graphite, carbon fiber, metal powder, and metal fiber; An ignition device characterized by:

7. The ignition device according to any one of claims 1 to 3, When a conductive polymer is used as the conductive material used for the second member, The physical properties of the conductive polymer are as follows: When formed by 3D printing, the volume resistivity is 30 to 115 Ω cm. An ignition device characterized by:

8. The ignition device according to any one of claims 1 to 3, When a conductive polymer is used as the conductive material used for the second member, HDPE is used as the insulating material of the third member; An ignition device characterized by:

9. 5. The ignition device according to claim 4, When HDPE is used as the insulating material of the third member of the ignition device, When an oxidizer is injected toward the through hole inside the ignition device and the oxidizer is ignited and burned by a discharge phenomenon caused by applying a voltage between the first member and the second member, At least the second member of the first and second members made of the conductive material retracts together with the third member; An ignition device characterized by:

10. 6. The ignition device according to claim 5, When HDPE is used as the insulating material of the third member of the ignition device, When an oxidizer is injected toward the through hole inside the ignition device and the oxidizer is ignited and burned by a discharge phenomenon caused by applying a voltage between the first member and the second member, At least the second member of the first and second members made of the conductive material retracts together with the third member; An ignition device characterized by:

11. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to any one of claims 1 to 3 is provided. A hybrid rocket characterized by:

12. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to any one of claims 1 to 3 is provided, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member, the regression rate is substantially the same as the regression rate of the solid fuel; A hybrid rocket characterized by:

13. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to claim 4, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member, the retreat speed of the second member and the third member is substantially the same as the retreat speed of the solid fuel; A hybrid rocket characterized by:

14. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to claim 5, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member; and the retreat speed of the second member and the third member is substantially the same as the retreat speed of the solid fuel; A hybrid rocket characterized by:

15. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to claim 6, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member, the retreat speed of the second member and the third member is substantially the same as the retreat speed of the solid fuel; A hybrid rocket characterized by:

16. In a hybrid rocket equipped with an oxidizer port for injecting oxidizer and solid fuel, The ignition device according to claim 7, When the third member of the ignition device is made of the same material as the solid fuel, When an oxidizer is injected from the oxidizer port toward the through-hole inside the ignition device, and a discharge phenomenon occurs when a voltage is applied between the first member and the second member, the oxidizer is ignited and the solid fuel is burned, At least the second member of the first and second members made of the conductive material retracts together with the third member, the retreat speed of the second member and the third member is substantially the same as the retreat speed of the solid fuel; A hybrid rocket characterized by:

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