Detonation combustor, rotation detonation rocket engine, and hybrid rocket system

Abstract

This detonation combustor comprises a combustor cylinder, an oxidant supply unit for supplying an oxidant into the combustor cylinder, and a fuel supply unit for supplying fuel into the combustor cylinder. The detonation combustor burns a mixed gas of fuel and oxidant as a result of a detonation wave passing through the mixed gas. At least a portion of an inner wall surface of the combustor cylinder in the vicinity of the oxidant supply unit and the fuel supply unit is covered with solid fuel.

Description

Detonation combustor, rotary detonation rocket engine and hybrid rocket system

[0001] The present disclosure relates to detonation combustors, rotary detonation rocket engines, and hybrid rocket systems.

[0002] BACKGROUND ART Rotating detonation engines (also referred to as RDEs or rotating detonation combustors) have been proposed as compact, high-thrust combustion devices that can replace existing gas turbine engines and rocket engines (see, for example, Patent Document 1).

[0003] Patent Publication No. 2017-142044

[0004] The greatest challenge in combustion engineering is determining how much energy can be extracted and converted into work from a given combination of fuel and oxidizer—that is, how to improve combustion efficiency. In a rotary detonation engine, a self-propelled detonation wave, accompanied by a shock wave, propagates at hypersonic speeds (approximately Mach number 5 or greater) and rotates around an annular flow path, burning the fuel. This allows the premixed air-fuel mixture (a mixture of combustible gaseous fuel and an oxidizer such as air) filled in the tube to combust over an extremely short time and distance. In this way, detonation engines theoretically achieve the highest thermal efficiency of any existing combustion cycle.

[0005] These detonation engines have the advantage of being able to achieve high thermal efficiency compared to conventional combustion cycles, with high combustion completeness in both time and space. Rotary detonation engines, in particular, are well suited to generating high thrust densities because they maintain detonation continuously within the combustor.

[0006] The type of rotary detonation engine currently being primarily studied is the double cylindrical combustor (annular type) disclosed in Patent Document 1. This is a combustor volume formed in the gap between two cylinders, an inner cylinder and an outer cylinder, and is structured so that detonation waves propagate in the circumferential direction.

[0007] In response to this, a type of rotary detonation engine called a hollow-type combustor has been studied in recent years. This has a single-cylinder structure in which the inner cylinder has been removed from the double-cylinder combustor, and has the advantage of being more compact.

[0008] On the other hand, detonation engines have the problem that the temperature of the combustion gases burned by the detonation wave is very high. For example, ２ H ４ -O ２ The temperature of the premixed fuel reaches approximately 4000 K during combustion. This means that the heat load on the inner wall of the combustor is very large. Therefore, thermal protection of the inner wall of the combustor is a major practical issue.

[0009] Methods proposed to reduce the heat load on the combustor inner wall include the "fluid heat exchange method," which involves cooling the inner wall of the outer tube by flowing a coolant such as water through a hollow chamber installed on the side of the outer tube, and the "film cooling method," which involves injecting unburned fuel fluid onto the inner wall of the outer tube to form an insulating layer, thereby preventing the detonation wave from directly contacting the inner wall. However, the fluid heat exchange method has the disadvantage of requiring pumps and flow paths to push the cooling water, which makes the cooling structure complex and hinders the miniaturization of the combustor. Another disadvantage of the film cooling method is that it releases unburned fuel, which reduces combustion efficiency.

[0010] The technology disclosed herein has been developed in light of these circumstances, and its purpose is to reduce the thermal load on the inner wall of a small rotating detonation type combustor without reducing the combustion efficiency and propulsion efficiency.

[0011] In order to solve the above problems, a detonation combustor according to one aspect of the present invention includes a combustor tube, an oxidizer supply unit for supplying an oxidizer into the combustor tube, and a fuel supply unit for supplying fuel into the combustor tube. This detonation combustor burns a mixed gas of fuel and oxidizer by a detonation wave passing through the mixed gas, and at least a portion of the inner wall surface of the combustor tube near the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

[0012] Another aspect of the present invention is also a detonation combustor. The detonation combustor includes a combustor outer casing, a combustor inner casing that forms a double-cylinder structure with the combustor outer casing, an oxidizer supply unit for supplying an oxidizer into the double-cylinder structure, and a fuel supply unit for supplying fuel into the double-cylinder structure. The detonation combustor burns a mixed gas of fuel and oxidizer by a detonation wave passing through the mixed gas, and at least a portion of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing near the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

[0013] In some embodiments of the detonation combustor, the solid fuel may be a polymer.

[0014] Yet another aspect of the present invention is a rotary detonation rocket engine comprising a combustor tube, an oxidizer supply section for supplying oxidizer into the combustor tube, and a fuel supply section for supplying fuel into the combustor tube. The rotary detonation rocket engine burns fuel and oxidizer as a detonation wave passes through a mixed gas of fuel and oxidizer, and at least a portion of the inner wall surface of the combustor tube near the oxidizer supply section and the fuel supply section is covered with solid fuel.

[0015] Yet another aspect of the present invention is also a rotary detonation rocket engine. This rotary detonation rocket engine includes a combustor outer casing, a combustor inner casing that forms a double-cylinder structure with the combustor outer casing, an oxidizer supply unit for supplying oxidizer into the double-cylinder structure, and a fuel supply unit for supplying fuel into the double-cylinder structure. This rotary detonation rocket engine burns a mixed gas of fuel and oxidizer when a detonation wave passes through it, and at least a portion of the wall surface of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing near the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

[0016] In some embodiments of the rotary detonation rocket engine, the solid fuel may be a polymer.

[0017] Yet another aspect of the present invention is a hybrid rocket system comprising a combustor tube, an oxidizer supply unit for supplying oxidizer into the combustor tube, and solid fuel covering at least a portion of the inner wall surface of the combustor tube near the oxidizer supply unit. The oxidizer supplied into the combustor tube is ignited to form a flame on the surface of the solid fuel, and the solid fuel is decomposed or melted, generating fuel gas, which is then combusted by a detonation wave passing through the generated fuel gas.

[0018] Yet another embodiment of the present invention is also a hybrid rocket system. This hybrid rocket system includes a combustor outer casing, a combustor inner casing that forms a double-cylinder structure with the combustor outer casing, an oxidizer supply unit for supplying oxidizer into the double-cylinder structure, and solid fuel that covers at least a portion of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing near the oxidizer supply unit. The oxidizer supplied inside the double-cylinder structure is ignited to form a flame on the surface of the solid fuel, and a detonation wave passes through the fuel gas generated by the decomposition or melting of the solid fuel, causing combustion.

[0019] In some embodiments of the hybrid rocket system, the solid fuel may be a polymer.

[0020] Any combination of the above components, and conversion of the present disclosure into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present disclosure.

[0021] According to the present disclosure, in a small rotating detonation type combustor, the thermal load on the inner wall of the combustor can be reduced.

[0022] Fig. 2 is a schematic diagram showing the operation of a single-cylindrical rotating detonation combustor. Fig. 3 is a schematic cross-sectional view of a small combustor according to Example 1 of the first embodiment. Fig. 4 is an enlarged view of the part surrounded by the dashed line in Fig. 2. Fig. 5 is a schematic cross-sectional view of a small combustor according to Example 2 of the first embodiment. Fig. 6 is a schematic diagram of a general hybrid rocket system. Fig. 7 is a schematic cross-sectional view of a hybrid rocket system according to a third embodiment.

[0023] Preferred embodiments will be described below with reference to the drawings. The same or equivalent components, parts, and processes shown in each drawing will be designated by the same reference numerals, and redundant descriptions will be omitted where appropriate. Furthermore, the embodiments are merely examples and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0024] In addition, the dimensions (thickness, length, width, etc.) of each member shown in the drawings may be enlarged or reduced as appropriate for ease of understanding. Furthermore, the dimensions of multiple members do not necessarily represent the relative size of each other, and even if a member A is depicted as being thicker than another member B in the drawings, member A may actually be thinner than member B.

[0025] [Principle of Detonation Engine] Figure 1 is a schematic diagram showing the operation of a single-cylinder rotating detonation combustor. This combustor is single-cylinder type, and combustible gaseous fuel and an oxidizer such as air are supplied axially from the left end of the figure to form a mixture. The combusted mixture generates a detonation wave near the left end of the single cylinder, which propagates extremely rapidly in the circumferential direction of the single cylinder. Within the single cylinder, an oblique shock wave propagates from left to right, and combustion gas is released from the right end along the pressure gradient between the high-pressure combustion gas and the low-pressure external pressure. A combustible gas layer exists in front of the detonation wave, and a combustion gas layer exists behind the detonation wave. A detonation wave exists near the gaseous fuel and oxidizer supply area (combustion region) within the single cylinder, and this area becomes extremely hot.

[0026] [First embodiment] (Example 1) Single-cylindrical small-sized combustor FIG. 2 is a schematic cross-sectional view of a small-sized combustor 1 according to Example 1 of the first embodiment, more specifically, a cross-sectional view taken along a plane including the generatrix and central axis of the small-sized combustor 1. The small-sized combustor 1 has a single-cylindrical structure equipped with a combustor outer casing 10. Hereinafter, the z-axis is defined as the direction of the central axis of the combustor outer casing 10, and the R-axis is defined as the radial direction of the bottom surface of the combustor outer casing 10. The small-sized combustor 1 includes an oxidizer supply unit 11 and a fuel supply unit 12. At least a portion of the inner wall 20 of the combustor outer casing 10 near the oxidizer supply unit 11 and the fuel supply unit 12 is covered with a solid fuel 13. A combustion gas discharge unit 21 is provided at one end of the combustor outer casing 10 (opposite the oxidizer supply unit 11 and the fuel supply unit 12).

[0027] In this specification, the terms "cylinder," "single cylinder," and "double cylinder" do not necessarily refer to a cylinder whose cross section perpendicular to the axis is a perfect circle (i.e., in the strict sense), but also include, for example, an "approximately cylinder" or "approximately single cylinder" whose bottom surface is close to a circle.

[0028] Combustor liner 10 may be a metal or alloy such as, but not limited to, copper, stainless steel, or inconel.

[0029] The oxidant supplied from the oxidant supply unit 11 may be a gas such as pure oxygen or air, but is not limited to these.

[0030] The fuel supplied from the fuel supply unit 12 may be a gas such as hydrocarbon or hydrogen, but is not limited to these.

[0031] The solid fuel 13 covering at least a portion of the inner wall 20 of the combustor casing 10 near the oxidizer supply section 11 and the fuel supply section 12 may be a polymer such as hydroxyl-terminated polybutadiene, polyethylene, polypropylene, paraffin wax, acrylic, etc., but is not limited to these.

[0032] The solid fuel 13 may have any shape, pattern, or distribution as long as it covers at least a portion of the inner wall 20 of the combustor outer casing 10 near the oxidizer supply unit 11 and the fuel supply unit 12. For example, the solid fuel 13 may be arranged in a plurality of annular regions along the circumference of the inner wall 20 of the combustor outer casing 10, or may be arranged in a plurality of spots. Alternatively, the solid fuel 13 may cover the entire inner wall 20 of the combustor outer casing 10 near the oxidizer supply unit 11 and the fuel supply unit 12, or may even cover the entire inner wall 20.

[0033] Fuel supplied from the fuel supply unit 12 is supplied into the inside of the combustor outer casing 10. The supplied fuel is mixed with the oxidizer supplied from the oxidizer supply unit 11. The mixed gas is combusted when a detonation wave passes through the mixed gas. The detonation wave propagates circumferentially inside the combustor outer casing 10. Because the downstream side of the detonation wave is at high temperature and high pressure, the mixed gas automatically combusts as the detonation wave passes. A mixed gas layer exists as a combustible gas layer in the portion upstream of the detonation wave (in other words, the portion not reached by the rotating detonation wave). On the other hand, a combustion gas layer exists in the portion downstream of the detonation wave.

[0034] At this time, the solid fuel 13 covering at least a part of the inner wall 20 of the combustor outer casing 10 near the oxidizer supply section 11 and the fuel supply section 12 is combusted by the passage of the detonation wave. The resulting endothermic reaction accompanying the sublimation and thermal decomposition of the solid fuel 13 reduces the thermal load on the inner wall 20.

[0035] FIG. 3 is an enlarged view of the area surrounded by the dashed line in FIG. 2 (i.e., the vicinity of the oxidizer supply section 11 and the fuel supply section 12). In FIG. 3, arrows indicate the flow of material and heat. The propellant flows in the z-axis direction within the combustor outer casing 10 toward the combustion gas discharge section 21. Heat due to detonation generated within the combustor outer casing 10 flows outward in the radial direction R (i.e., toward the inner wall 20). On the other hand, heat absorption due to sublimation or pyrolysis of the solid fuel 13 is indicated by arrows pointing in the opposite direction to the heat inflow to the inner wall 20 due to detonation. As a result, the difference between the heat inflow due to detonation and the heat absorption due to sublimation or pyrolysis of the solid fuel 13 is the actual heat inflow to the inner wall 20. From FIG. 3, it can be seen that the endothermic reaction accompanying the sublimation or pyrolysis of the solid fuel 13 reduces the thermal load on the inner wall 20.

[0036] When the small-scale combustor 1 is operated for a certain period of time and the solid fuel 13 is burned out, the small-scale combustor 1 can no longer be operated. However, even in this case, the small-scale combustor 1 can be reused by refilling it with solid fuel 13. In addition, the operating time of the small-scale combustor 1 can be controlled by adjusting the amount of solid fuel 13 charged.

[0037] As described above, according to this embodiment, in a small single-cylindrical combustor, the thermal load on the inner wall of the combustor can be reduced.

[0038] (Example 2) Double-Cylinder Small Combustor Figure 4 is a schematic cross-sectional view of a small-sized combustor 2 according to Example 2 of the first embodiment, more specifically, a cross-sectional view taken along a plane including the generatrix and central axis of the small-sized combustor 2. The small-sized combustor 2 has a double-cylindrical structure including a combustor inner casing 14 in addition to the single-cylindrical combustor outer casing 10 of Figure 2. The small-sized combustor 2 includes an oxidizer supply unit 11 that supplies an oxidizer and a fuel supply unit 12 that supplies fuel to the space between the combustor outer casing 10 and the combustor inner casing 14. At least a portion of the wall surface of either or both of the inner wall 20 of the combustor outer casing 10 and the combustor inner casing 14 near the oxidizer supply unit 11 and the fuel supply unit 12 is covered with solid fuel 13. A combustion gas discharge unit 21 is provided at one end of the space between the combustor outer casing 10 and the combustor inner casing 14 (the opposite side from the oxidizer supply unit 11 and the fuel supply unit 12).

[0039] The combustor liner 14, like the combustor liner 10, may be made of a metal or alloy such as, but not limited to, copper, stainless steel, or inconel.

[0040] According to this embodiment, in a double-cylinder type small combustor, the thermal load on the inner wall of the combustor can be reduced.

[0041] Second Embodiment The technology of the present disclosure can be applied to a rotary detonation rocket engine. Similar to the small combustor of the first embodiment, the rotary detonation rocket engine according to the second embodiment can be described using FIG. 2 . The rotary detonation rocket engine of the second embodiment has a single-cylinder structure. This rotary detonation rocket engine includes an oxidizer supply unit 11 and a fuel supply unit 12. At least a portion of the inner wall 20 of the combustor outer casing 10 near the oxidizer supply unit 11 and the fuel supply unit 12 is covered with solid fuel 13. A combustion gas discharge unit 21 is provided at one end of the combustor outer casing 10 (the opposite side from the oxidizer supply unit 11 and the fuel supply unit 12).

[0042] The operating principle of the rotary detonation rocket engine according to this embodiment is basically the same as that of the small combustor according to the first embodiment.

[0043] As with the first embodiment, the rotary detonation rocket engine according to this embodiment may be a double-cylinder rotary detonation rocket engine including a combustor inner casing 14 in addition to the combustor outer casing 10. In this case, the oxidizer supply unit 11 and the fuel supply unit 12 are provided at positions to supply oxidizer and fuel to the space between the combustor outer casing 10 and the combustor inner casing 14. In this case, at least a portion of the wall surface of either or both of the combustor outer casing 10 and the inner wall 20 of the combustor inner casing 14 near the oxidizer supply unit 11 and the fuel supply unit 12 is covered with solid fuel 13.

[0044] According to this embodiment, in a rotary detonation rocket engine, the thermal load on the inner wall of the combustor can be reduced.

[0045] [Third embodiment] The technology disclosed herein can also be applied to a hybrid rocket system. A hybrid rocket system is a rocket engine system that uses two different types of propellants. Figure 5 is a schematic diagram of a typical hybrid rocket system. This rocket system generates combustion by supplying a liquid oxidizer to a combustion chamber containing solid fuel, and propels itself forward by ejecting the resulting gas.

[0046] Compared to conventional solid fuel rockets and liquid fuel rockets, hybrid rocket systems have the following advantages: - low risk of explosion and safety; - easy starting / stopping / restarting, and good controllability since output can be adjusted simply by changing the amount of oxidizer supplied; and - low cost. On the other hand, hybrid rocket systems have the disadvantage that the fuel regression rate (gas acceleration of solid fuel) is low, making it difficult to increase thrust. This is the biggest engineering challenge in putting hybrid rocket systems into practical use. The third embodiment of the present disclosure is intended to solve these challenges.

[0047] 6 is a schematic cross-sectional view of a hybrid rocket system 3 according to a third embodiment. The hybrid rocket system 3 has a single-cylinder structure. This rotary detonation rocket engine includes an oxidizer supply unit 11 and a solid fuel 13. At least a portion of the inner wall 20 of the combustor casing 10 near the oxidizer supply unit 11 is covered with the solid fuel 13. A combustion gas discharge unit 21 is provided at one end of the combustor casing 10 (the opposite side to the oxidizer supply unit 11).

[0048] When oxidizer is supplied from the oxidizer supply unit 11 into the inside of the combustor casing 10 and ignited, a flame is formed on the surface of the solid fuel. At this time, the solid fuel 13 decomposes or melts due to the extremely high heat of detonation, generating fuel gas. The fuel gas is burned as the detonation wave passes through the mixed gas. The detonation wave propagates circumferentially inside the combustor casing 10. This solves the disadvantage of conventional hybrid rocket systems, which is the low fuel regression rate caused by the low combustion speed.

[0049] Furthermore, similarly to the first or second embodiment, the heat load on the inner wall 20 is reduced by the endothermic reaction caused by the sublimation or thermal decomposition of the solid fuel 13 .

[0050] As with the first embodiment, the hybrid rocket system according to this embodiment may be a double-cylindrical hybrid rocket system including a combustor inner casing 14 in addition to the combustor outer casing 10. In this case, the oxidizer supply unit 11 is provided at a position where it supplies oxidizer to the space between the combustor outer casing 10 and the combustor inner casing 14. In this case, at least a portion of the wall surface of either or both of the combustor outer casing 10 and the inner wall 20 of the combustor inner casing 14 near the oxidizer supply unit 11 is covered with solid fuel 13.

[0051] According to this embodiment, a hybrid rocket system can be realized that has a high fuel regression rate and reduces the thermal load on the inner wall of the combustor.

[0052] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and treatment processes, and that such modifications are also within the scope of the present invention.

[0053] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present disclosure. A new embodiment resulting from the combination has the combined effects of the combined embodiments and modifications.

[0054] When understanding the abstract technical ideas of the embodiments, the technical ideas should not be interpreted as being limited to the contents of the embodiments. The above-described embodiments and variations are merely illustrative examples, and many design modifications, such as changes, additions, and deletions of components, are possible. In the embodiments, the contents in which such design modifications are possible are emphasized by adding the notation "embodiment." However, design modifications are also permitted even in contents without such notation.

[0055] The compact combustor of the present disclosure can be widely used in fields where a compact, high-thrust combustion device is required, such as space rockets, gas turbine engines, and incinerators.

[0056] 1. Small combustor, 2. Small combustor, 3. Hybrid rocket system, 10. Combustor outer casing, 11. Oxidizer supply section, 12. Fuel supply section, 13. Solid fuel, 14. Combustor inner casing, 20. Inner wall, 21. Combustion gas discharge section.

Claims

1. A detonation combustor comprising a combustor tube, an oxidizer supply unit for supplying an oxidizer into the combustor tube, and a fuel supply unit for supplying fuel into the combustor tube, wherein a detonation wave passes through a mixed gas of the fuel and the oxidizer, causing combustion, and wherein at least a portion of the inner wall surface of the combustor tube in the vicinity of the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

2. A detonation combustor comprising: a combustor outer casing; a combustor inner casing that forms a double-cylinder structure with the combustor outer casing; an oxidizer supply unit for supplying oxidizer into the double-cylinder structure; and a fuel supply unit for supplying fuel into the double-cylinder structure, wherein a mixed gas of the fuel and the oxidizer is combusted by a detonation wave passing through the mixed gas; and wherein at least a portion of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing near the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

3. A detonation combustor according to claim 1 or 2, wherein the solid fuel is a polymer.

4. A rotary detonation rocket engine comprising a combustor tube, an oxidizer supply section for supplying oxidizer into the combustor tube, and a fuel supply section for supplying fuel into the combustor tube, wherein a detonation wave passes through a mixed gas of the fuel and the oxidizer to cause combustion, and wherein at least a portion of the inner wall surface of the combustor tube in the vicinity of the oxidizer supply section and the fuel supply section is covered with solid fuel.

5. A rotary detonation rocket engine comprising: a combustor outer casing; a combustor inner casing that forms a double-cylinder structure with the combustor outer casing; an oxidizer supply unit for supplying oxidizer into the double-cylinder structure; and a fuel supply unit for supplying fuel into the double-cylinder structure, wherein a detonation wave passes through a mixed gas of the fuel and the oxidizer to cause combustion, and wherein at least a portion of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing in the vicinity of the oxidizer supply unit and the fuel supply unit is covered with solid fuel.

6. A rotary detonation rocket engine according to claim 4 or 5, characterized in that the solid fuel is a polymer.

7. A hybrid rocket system comprising a combustion tube, an oxidizer supply unit for supplying oxidizer into the combustion tube, and solid fuel covering at least a portion of the inner wall surface of the combustion tube near the oxidizer supply unit, wherein the oxidizer supplied inside the combustion tube is ignited to form a flame on the surface of the solid fuel, and the solid fuel is decomposed or melted to generate fuel gas, which is then combusted by a detonation wave passing through the fuel gas.

8. A hybrid rocket system comprising: a combustor outer casing; a combustor inner casing that forms a double-cylinder structure with the combustor outer casing; an oxidizer supply unit for supplying oxidizer into the double-cylinder structure; and solid fuel that covers at least a portion of at least one of the inner wall surface of the combustor outer casing and the outer wall surface of the combustor inner casing near the oxidizer supply unit, wherein the oxidizer supplied inside the double-cylinder structure is ignited to form a flame on the surface of the solid fuel, and a detonation wave passes through the fuel gas generated by the decomposition or melting of the solid fuel, causing combustion.

9. A hybrid rocket system according to claim 7 or 8, characterized in that the solid fuel is a polymer.

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