Cooling device for nozzle of rocket engine and regeneration cooling system for hybrid rocket engine

Abstract

To provide a cooling device for a nozzle suitable for a hybrid engine by considering positional relation between a combustion chamber or a nozzle and a cooling channel and attaining a balanced state between a temperature rise and cooling performance of a coolant, and a regeneration cooling system.SOLUTION: By combining a first member 100 in which a helical groove part is provided in each channel on a part or the whole of an inner peripheral surface with a second member 200 having a shape in which an outer peripheral surface thereof is approximately flush with an inner peripheral surface of the first member 100 and including a nozzle-shaped hollow part for forming a nozzle part 280 on the inner side, a hole part corresponding to the shape of the helical groove part is formed, so as to form a helical cooling channel 135. The helical cooling channel 135 is formed at a position leaving a predetermined distance from a throat part 290 of the nozzle part formed on the inner side of the second member 200. This structure prevents the coolant flowing in the helical cooling channel 135 from being heated excessively, and exhibits a predetermined cooling function to suppress erosion of the nozzle.SELECTED DRAWING: Figure 16

Description

Technical Field

[0001] The present invention relates to the cooling of a nozzle of a rocket engine, and more particularly to the regenerative cooling of a nozzle of a hybrid rocket engine.

Background Art

[0002] As forms of rocket engines, in addition to solid-fuel rockets and liquid-fuel rockets, hybrid rockets that combine the advantages of both are known. Since the combustion gas of a rocket engine becomes particularly high-temperature and high-pressure when passing through the nozzle of the combustion chamber, it is required to cool it in order to prevent damage and erosion of the combustion chamber or nozzle.

[0003] On the other hand, adding a dedicated cooling device for cooling not only becomes a factor inhibiting the weight reduction of the rocket propulsion system, but also causes the disadvantage of increasing costs. Therefore, a means called regenerative cooling, in which the fuel or the like of a rocket engine is used for cooling the combustion chamber or nozzle, has come to be adopted.

[0004] For example, Patent Document 1, "Combustion Chamber Liner with Spiral Cooling Channels", discloses a technique related to a combustion chamber liner that uses a spiral cooling chamber for regenerative cooling of a combustion chamber during operation.

[0005] However, in the technique described in Patent Document 1, although spiral cooling channels are used, they are composed of 50 or more channels, and there is a disadvantage that the cooling performance is not improved so much compared with the axial straight cooling channels. This is because the coolant passes through the cooling channels without resistance, and sufficient heat exchange with the combustion chamber or nozzle is not performed (see FIG. 1).

[0006] As a corresponding technique, there is the technique of Patent Document 2. Patent Document 2, "Methane Engine for Rocket Propulsion," discloses a technique for performing regenerative cooling by supplying a propulsion fuel to a combustion chamber and a nozzle.

[0007] According to the technique of Patent Document 2, since the number of channels in the cooling channel is as small as 1, the pressure loss is large, and since the coolant tends to flow slowly through the cooling channel, sufficient heat exchange can be performed, and an effect of high cooling performance can be expected.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the technique disclosed in Patent Document 2, since a cooling channel having a spiral structure is formed over the entire length of the nozzle, the coolant passing through the cooling channel is excessively heated, and depending on the coolant used, an explosive phenomenon may occur in the cooling channel, and there is a risk of damaging the cooling channel or the combustion chamber (see Figure 2). In addition, as a problem common to Patent Document 1 and Patent Document 2, since the cooling channel is provided along the nozzle shape that is thin and constricted in the center (without taking a distance from the nozzle where the temperature becomes very high), there is also a problem that it is directly affected by the temperature rise of the combustion chamber or the nozzle.

[0010] In addition, the technique of Patent Document 1 assumes a nozzle made of a metal such as copper, and in Patent Document 2 as well, due to the adoption of a liquid fuel system, it is assumed that a metal nozzle is used. Therefore, for example, a nozzle made of a metallic material with a thermal conductivity exceeding 200 W / (m·K), such as copper, directly transfers the heat of the high-temperature combustion gas at 2500 to 3000 degrees inside the nozzle to the coolant flowing through the cooling channel, which has been a factor accelerating the temperature rise of the coolant.

[0011] Thus, in the technologies of Patent Document 1 and Patent Document 2, the consideration regarding the positional relationship between the combustion chamber or nozzle and the cooling channel, and the thermal conductivity of the nozzle material was insufficient. Also, the technologies of Patent Document 1 and Patent Document 2 were for the purpose of regenerative cooling of nozzles for solid fuel rockets, liquid fuel rockets, etc., and did not present solutions to the problems specific to hybrid rocket engines. Therefore, first, the problems specific to hybrid rocket engines will be described below.

[0012] Since a hybrid rocket carries a solid fuel and a liquid oxidizer, there is no risk of explosion and it can be operated safely because the fuel and the oxidizer do not naturally mix. Generally, oxygen, hydrogen peroxide, etc. are used as the oxidizer of a hybrid rocket, and hydrocarbon-based polymers such as polyethylene, polypropylene, and acrylic resin can be used as the solid fuel, and it can be manufactured at a lower cost compared to solid fuel rockets, etc.

[0013] Also, depending on the combination of the oxidizer and these solid fuels, it is known that a propulsion force 10% or higher than that of the solid propellant used in solid fuel rockets can be obtained, and it can be used as a high-performance rocket engine. Also, by controlling the flow rate of the oxidizer, the engine output can be adjusted, and stopping and re-ignition are possible, and it can be used as a highly functional rocket engine. Thus, hybrid rockets are excellent in terms of safety, high propulsion force, combustion interruption / re-ignition / thrust control, etc.

[0014] During the operation of the engine, high-pressure gas or liquid oxidizer pressurized by a pump is blown into the combustion chamber filled with solid fuel, ignited by a separately prepared ignition device, and a flame is formed on the surface of the solid fuel. The solid fuel decomposes or melts and vaporizes due to heat. At the same time, the oxidizer also becomes an oxidizing gas due to heat, and these gases convect or diffuse to maintain the flame.

[0015] However, ultimately, combustion is maintained by the phenomenon of boundary layer combustion occurring in the boundary layer several millimeters from the surface of the solid fuel. Therefore, different from the combustion where the flame and fuel are at a distance of several tens of micrometers like in solid propellants or liquid propellants, the heat supply to the fuel is not necessarily sufficient. Therefore, the research team of the present invention considered whether high heat could be supplied to the fuel by using nitrous oxide, which becomes a mixed gas with a higher oxygen partial pressure than the atmosphere when thermally decomposed, instead of relatively safe liquid oxygen or hydrogen peroxide as the oxidizer.

[0016] Note that nitrous oxide (N2O) has a high vapor pressure at room temperature (about 50 bar), so it can be discharged from the tank without using the usually required complex pumps and pressurization systems, which has the merit of self-pressurization and reducing the weight and simplifying the design of the entire propulsion system. On the other hand, when using liquid nitrous oxide, it was found that if a helical cooling channel is configured along the shape of the nozzle, the nitrous oxide will cause a rapid temperature change due to the combustion temperature in the nozzle, resulting in an explosive phenomenon and posing a risk of destroying the cooling channel and the nozzle. This is because nitrous oxide (N2O) has a critical temperature close to room temperature at 36.5 °C, and there is a certain possibility of reaching the critical temperature due to the temperature rise caused by heat exchange with the nozzle.

[0017] Also, since oxygen does not reach the critical state whether in the liquid state or the gaseous state, With the cooling function, there was no problem even if not much countermeasure was taken for the superheat of the coolant. However, when the combustion efficiency was increased by using nitrous oxide, it was found that there were problems such as the nozzle melting due to heat and the erosion of the nozzle progressing rapidly.

[0018] Therefore, in the present invention, a cooling device for a rocket engine (hereinafter referred to as a "cooling device for nozzle" or simply "cooling device") that suppresses the erosion of the nozzle by using a helical cooling channel and has high safety without explosive phenomena even when nitrous oxide is used as an oxidizer of a hybrid rocket engine, and a regenerative cooling system are provided.

[0019] Further, in the present invention, in consideration of the positional relationship between the combustion chamber or nozzle and the cooling channel, a balance is achieved between the temperature rise of the coolant and the cooling performance, and a cooling device for a nozzle suitable for a hybrid engine and a regenerative cooling system are provided. In addition, while providing cooling channels for each channel, attention is also paid to the number of channels of the cooling channels, and the purpose is to achieve a balance between the temperature rise of the coolant and the cooling performance.

Means for Solving the Problems

[0020] In order to achieve the above object, a first invention is A cooling device having a coolant inlet and a coolant outlet for cooling a nozzle of a rocket engine, A member having a cylindrical or tapered shape on the inner peripheral surface of the member, A first member provided with helical groove portions for each of the channels with the number of channels I (I = 1 to n (n is an integer of 1 or more)) on a part or all of the inner peripheral surface of the member, A member having a cylindrical or tapered outer shape of the member, The shape of the outer peripheral surface of the member is substantially the same as the shape of the inner peripheral surface of the first member, When the member is fitted to the inner peripheral surface of the first member, the outer peripheral surface of the member has a shape such that it is substantially flush with the inner peripheral surface of the first member, The inside of the member is provided with a nozzle-shaped cavity for forming a nozzle portion of a rocket engine, a second member that secures a predetermined distance (ds) between the throat portion of the nozzle portion of the member and the outer peripheral surface of the member, means for forming a helical cooling channel between the inner peripheral surface of the first member and the outer peripheral surface of the second member by combining the first member and the second member, a helical groove portion provided on the inner peripheral surface of the first member, by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, the helical cooling channel is formed, and the helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, means for preventing the coolant flowing through the helical cooling channel from being excessively heated when the combustion gas of the rocket engine passes through the nozzle portion and for exerting a predetermined cooling function, characterized by.

[0021] A second invention is In the cooling device for a rocket engine nozzle according to the first invention, In the first member, a part of the inner peripheral surface of the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, When the helical cooling channel is formed by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, in addition to forming the helical cooling channel at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, making the effective width (hw) of the helical cooling channel shorter than the total length of the nozzle portion, characterized by.

[0022] A third invention is In the cooling device for a rocket engine nozzle according to the second invention, By using a predetermined heat conductive material containing graphite as the material of the second member, When the combustion gas of the rocket engine passes through the nozzle portion, the heat received by the nozzle portion of the second member is transmitted through the predetermined heat conductive material to the coolant flowing through the helical cooling channel, The heat exchange function of the coolant exerts a predetermined cooling function on the nozzle portion, and The helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, By using the predetermined heat conductive material, it has a function of gradually reducing the temperature according to the distance from the nozzle portion which is the heat source, When the combustion gas of the rocket engine passes through the nozzle portion, preventing the coolant flowing through the helical cooling channel from being overheated, It is characterized by the above.

[0023] The fourth invention is In the cooling device for a rocket engine nozzle according to any one of the second or third inventions, When nitrous oxide is used as the coolant flowing through the helical cooling channel, In order to prevent the phenomenon that the nitrous oxide as the coolant is rapidly heated by the combustion gas of the rocket engine and an explosive phenomenon occurs, and the helical cooling channel or the nozzle portion is destroyed, In addition to forming the helical cooling channel at a position having a predetermined distance ds from the throat portion of the nozzle portion formed inside the second member, Making the effective length of the helical cooling channel shorter than the total length of the nozzle portion, It is characterized by the above.

[0024] The fifth invention is In the cooling device for a rocket engine nozzle according to any one of the second or third inventions, a predetermined distance (ds) provided between the helical cooling channel and the throat portion of the nozzle portion is two times or more the diameter (nsd) of the throat portion of the nozzle portion, and an effective width (hw) of the helical cooling channel is 1 / 3 to 1 / 2 of the total length (nzl) of the second member, characterized by.

[0025] A sixth invention is In the cooling device for a rocket engine nozzle according to any one of the second or third inventions, in the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member, when forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, a turning angle α of the helical groove portion is 2 to 10 degrees, characterized by.

[0026] A seventh invention is In the cooling device for a rocket engine nozzle according to any one of the second or third inventions, in the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member, when forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, the number of channels I of the helical groove portion is 2 to 8, characterized by.

[0027] An eighth invention is In the cooling device for a rocket engine nozzle according to the seventh invention, in the first member, on a part of the inner peripheral surface of the first member, while providing an introduction zone for introducing a coolant to the cooling channel, By providing a recovery zone for recovering the coolant whose temperature has risen after passing through the cooling channel, even when the number of channels I of the cooling channel is as small as 2 to 8, the introduction and recovery of the coolant into the cooling channel can be smoothly performed. It is characterized by the above.

[0028] The ninth invention is a regenerative cooling system for regeneratively cooling a nozzle portion of a hybrid rocket engine, comprising an oxidizer in a liquid phase state, an oxidizer storage portion for storing the oxidizer in a liquid phase state, an oxidizer injection portion for injecting the oxidizer, a solid fuel portion serving as a propellant of the rocket, an ignition portion for causing a combustion reaction between the oxidizer and the solid fuel, a nozzle portion for accelerating the combustion gas generated by the combustion of the solid fuel to supersonic speed, and a cooling channel for using the oxidizer for cooling the nozzle portion. As a member for regenerative cooling, a member having a cylindrical or tapered shape on the inner peripheral surface of the member, a first member provided with helical groove portions for each of the channels having the number of channels I (I = 1 to n, where n is an integer of 1 or more) on a part or all of the inner peripheral surface of the member, As a member including the nozzle portion to be regeneratively cooled, a member having a cylindrical or tapered outer shape of the member, the shape of the outer peripheral surface of the member is substantially the same as the shape of the inner peripheral surface of the first member, when the member is fitted to the inner peripheral surface of the first member, the outer peripheral surface of the member has a shape such that it is substantially flush with the inner peripheral surface of the first member, the member is provided with a nozzle-shaped cavity for forming a nozzle portion of the rocket engine inside, a second member having a predetermined distance (ds) secured between the throat portion of the nozzle portion of the member and the outer peripheral surface of the member, means for forming a helical cooling channel between the inner peripheral surface of the first member and the outer peripheral surface of the second member by combining the first member and the second member, the helical groove portion provided on the inner peripheral surface of the first member, By forming a hole corresponding to the shape of the helical groove portion between the outer peripheral surface of the second member, the helical cooling channel is formed, and since the helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, when the combustion gas of the rocket engine passes through the nozzle portion, there is provided means for preventing the coolant flowing through the helical cooling channel from being excessively heated and for exerting a predetermined cooling function, a piping portion for the cooling channel for guiding the oxidizer from the oxidizer storage portion to the cooling channel and functioning as an oxidizer, and a piping portion for the oxidizer for refluxing the oxidizer that has passed through the cooling channel to the oxidizer injection portion and functioning as an oxidizer, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

[0029] The tenth invention is In the regenerative cooling system for a hybrid rocket engine according to the ninth invention, In the first member, a part of the inner peripheral surface of the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, When the helical cooling channel is formed by forming a hole corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, in addition to forming the helical cooling channel at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, making the effective width (hw) of the helical cooling channel shorter than the total length of the nozzle portion, Characterized by the above.

[0030] The eleventh invention is In the regenerative cooling system for a hybrid rocket engine according to the tenth invention, By using a predetermined heat-conductive material containing graphite as the material of the second member, when the combustion gas of the rocket engine passes through the nozzle portion, the heat received by the nozzle portion of the second member is transmitted through the predetermined heat-conductive material to the coolant flowing through the helical cooling channel, and by the heat exchange function of the coolant, a predetermined cooling function for the nozzle portion is exerted, the helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, by using the predetermined heat-conductive material, a function of gradually decreasing the temperature according to the distance from the nozzle portion as the heat source is provided, and when the combustion gas of the rocket engine passes through the nozzle portion, it is possible to prevent the coolant flowing through the helical cooling channel from being excessively heated. It is characterized by the above.

[0031] The twelfth invention is in the regenerative cooling system for a hybrid rocket engine according to the tenth invention, when nitrous oxide is used as the coolant flowing through the helical cooling channel, in order to prevent the phenomenon that the nitrous oxide as the coolant is rapidly heated by the combustion gas of the rocket engine and an explosive phenomenon occurs, and the helical cooling channel or the nozzle portion is destroyed, in addition to forming the helical cooling channel at a position having a predetermined distance ds from the nozzle portion formed inside the second member, the effective length of the helical cooling channel is made shorter than the total length of the nozzle portion. It is characterized by the above.

[0032] The thirteenth invention is in the regenerative cooling system for a hybrid rocket engine according to the tenth invention, A predetermined distance (ds) provided between the helical cooling channel and the throat portion of the nozzle portion is two or more times the diameter nzd of the second member, The effective width (hw) of the helical cooling channel is 1 / 3 to 1 / 2 of the diameter (nsd) of the throat portion of the nozzle portion, characterized by the above.

[0033] The 14th invention is In the regenerative cooling system for a hybrid rocket engine described in the 10th invention, In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member, When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, The turning angle α of the helical groove portion is 2 to 10 degrees, characterized by the above.

[0034] The 15th invention is In the regenerative cooling system for a hybrid rocket engine described in the 10th invention, In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member, When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member, The number of channels of the helical groove portion is 2 to 8, characterized by the above.

[0035] The 16th invention is In the regenerative cooling system for a hybrid rocket engine described in the 15th invention, In the first member, on a part of the inner peripheral surface of the first member, An introduction zone for introducing a coolant into the cooling channel is provided, and By providing a recovery zone for recovering the coolant whose temperature has risen after passing through the cooling channel, even when the number of channels I of the cooling channel is as small as 2 to 8, the introduction and recovery of the coolant into the cooling channel can be smoothly performed. It is characterized by the above.

[0036] The 17th invention is In the regenerative cooling system for a hybrid rocket engine described in the 9th to 16th inventions, A phase change orifice is arranged in the piping section for the cooling channel from the oxidizer storage section to the cooling channel, and the oxidizer stored in the liquid phase state in the oxidizer storage section is changed to the gaseous state and then delivered to the helical cooling channel. It is characterized by the above.

Effect of the Invention

[0037] According to the present invention, even when nitrous oxide is used as the oxidizer of the hybrid rocket engine, it is possible to provide a cooling system with high safety without explosive phenomena. In addition, according to the present invention, it is possible to suppress nozzle erosion while achieving a balance between cooling performance and the temperature rise of the coolant.

Brief Description of the Drawings

[0038]

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[0039] <Explanation of Terms> ◇A nozzle is a structure placed immediately after the combustion chamber of a rocket engine and has the function of discharging combustion gas from the rocket. By having a predetermined shape on its inner peripheral surface, the nozzle can increase the pressure in the combustion chamber or raise the injection speed of the discharged combustion gas. For example, a nozzle shaped like an hourglass, which is a tube that narrows in the middle like a De Laval nozzle, is known to be able to accelerate combustion gas to supersonic speeds. ◇The nozzle part refers to the part of the inner peripheral surface of the nozzle. In the case of a metal nozzle, it often has the same shape as the nozzle, so the nozzle and the nozzle part are substantially the same. On the other hand, in the case of a graphite nozzle, the nozzle is cylindrical or tapered, and a cavity is provided on the inner peripheral surface, and it often functions as a nozzle by having a predetermined shape. In that case, the line on the inner peripheral surface is defined as the nozzle part. ◇The throat part refers to the narrowest part of the nozzle part. It has the effect of increasing the pressure in the combustion chamber and, by narrowing the diameter, increasing the flow rate of the injected combustion gas and improving the thrust. The diameter of the throat part relative to the inlet and outlet of the nozzle part is an important parameter that determines the thrust of the rocket engine. Also, it is the part that is exposed to the highest temperature and pressure in the nozzle part. If this part is eroded and the diameter expands, it will also cause the thrust to decay. Therefore, suppressing the erosion of the throat part is one of the important issues.

[0040] ◇Self-pressurization means being pressurized only by discharging from the tank without using the usually required complex pumps or pressurization systems. Nitrous oxide (N2O) can utilize self-pressurization because of its high vapor pressure at room temperature (about 50 bar). ◇An oxidizer plays the role of burning fuel in the oxygen-free space of the universe. It is used in all of liquid fuel rockets, solid fuel rockets, and hybrid rockets. The use of liquid oxygen (LO2), liquid nitrous oxide (N2O), etc. has been attempted. ◇A hybrid rocket engine refers to a rocket engine that uses a solid fuel and a liquid oxidizer. ◇Regenerative cooling refers to a cooling method that utilizes the latent heat of vaporization. It is used in rocket engines, refrigerators, and air conditioning systems. In the case of liquid fuel rocket engines, it means using fuel for cooling. In the case of hybrid rocket engines, it means using oxidizer for cooling.

[0041] ◇Helical means a spiral shape. A synonym is "spiral". Both "spiral" and "helical" are translated as "helix", but "spiral" can be distinguished as a vortex shape with a central point, and "helical" as a coil shape. ◇A cooling channel refers to a pipe through which a coolant passes. The pipe can be formed not only by a pipe but also by combining a curved or flat surface with a groove as in the present invention. ◇A helical cooling channel refers to a structure formed as a cooling channel for passing a coolant by providing a helical groove on the inner peripheral surface of an outer first member and making the inner peripheral surface of the outer first member (the same surface as the helical convex portion) flush with the outer peripheral surface of an inner second member.

[0042] ◇An introduction zone refers to a belt-shaped space that serves to pool the coolant once and introduce the coolant to the inlets of individual cooling channels. Structurally, it is composed of a space formed by providing a groove on the inside of the outer first member and making the inner peripheral surface of the first member (excluding the groove) flush with the outer peripheral surface of the inner second member. Unlike the helical cooling channel, the introduction zone has an annular structure without twist. Also, in order to pool the coolant once and introduce the coolant to the inlets of individual cooling channels, it is desirable that the width is longer than the width of the helical groove that generates the cooling channel. ◇A recovery zone refers to a belt-shaped space for recovering the heated coolant after it has served its purpose from the outlets of individual cooling channels. Since the structure is the same as that of the introduction zone, the description is omitted.

[0043] ◇The Nusselt number (Nu) refers to the dimensionless value representing the ratio of heat conduction to heat transfer of a convecting fluid. If there is no convection, Nu = 1. The Nusselt number is used to evaluate the heat transfer performance (such as heat dissipation performance) due to convection. The larger the Nusselt number, the higher the heat transport effect due to convection. ◇Cavitation refers to the state in which a liquid is vaporized by an orifice. ◇O2 means oxygen. ◇LO2 means liquid oxygen. ◇N2O means nitrous oxide. ◇LN2O means liquid nitrous oxide. ◇HDPE is the abbreviation of High - density polyethylene and means high - density polyethylene. It is used for the solid fuel of a hybrid rocket engine. ◇The equivalence ratio refers to the ratio (om / fm) of the mass flow rate of the oxidizer om to the mass flow rate of the fuel fm.

Embodiments for Carrying out the Invention

[0044] Hereinafter, embodiments of the present invention will be described. Note that the configurations, figures, and tables in the description are merely illustrative and can also be applied to other shapes and configurations.

[0045] 1. Regarding the configurations of the first member and the second member 1 - 1. Overview The cooling device for a rocket engine nozzle of the present invention is roughly composed of two parts: a first member arranged on the outside and a second member arranged on the inside. Hereinafter, first, with reference to FIGS. 2 to 7, the configuration of the first member of the cooling device for a rocket engine nozzle of the present invention will be described. Next, with reference to FIGS. 8 to 10, the configuration of the second member will be described.

[0046] 1 - 2. Configuration of the first member 1 - 2 - 1. Configuration of the first member (plan view) (FIG. 3) FIG. 3 is a diagram showing an example of the configuration of the first member of the present invention, and is a plan view (viewed from above) of the first member. The first member is roughly composed of a cylindrical body portion 101 and a disk-shaped flange portion 102. The flange portion 102 is a flange for connecting to the hybrid rocket engine main body. An inlet 110 and an outlet 170 for supplying and discharging a coolant (also serving as an oxidizer) are provided on the outer peripheral surface of the body portion 101. According to the figure, the positional relationship between the inlet 110 and the outlet 170 is arranged at a position shifted by 90 degrees, but they may be provided in the same direction. For example, it can be freely set according to the convenience of the routing of the coolant piping.

[0047] Also, the inlet and the outlet may be replaced with the reverse positional relationship. Therefore, in the figures after FIG. 3, it is expressed as an inlet (or outlet), or an outlet (or inlet). Also, in FIG. 3, the number of inlets 110 is set to 1 and the number of outlets 170 is set to 2, but either can be freely set to 1 or 2, etc. The dimensions of each part can be freely determined according to the size and output of the rocket. As an example, when the total length including the hybrid rocket engine main body is about 30 cm, the diameter (D1Dd) of the body portion of the first member is about 5 cm, the length (L1) of the body portion of the first member is about 6 cm, the diameter (D1Fd) of the flange portion of the first member is about 9 cm, and the thickness (D2) of the flange portion of the first member can be about 5 mm.

[0048] 1-2-2. Configuration of the First Member (Front View) (FIG. 4) FIG. 4 is a diagram showing an example of the configuration of the first member of the present invention, and is a front view of the first member. Note that the back view is substantially the same, so the description is omitted. The positional relationship and number of the inlet 110 and the outlet 170 are the same as those described in FIG. 3, so the description thereof is omitted.

[0049] 1-2-3. Configuration of the First Member (Perspective View of Cross-Section B-B) (FIG. 5) FIG. 5 is a view showing an example of the configuration of the first member of the present invention, and is a perspective view of a cross-section B-B. As shown in FIG. 5, the inner peripheral surface of the first member can adopt a substantially cylindrical configuration, but a configuration in which the inner diameter changes in a tapered shape as described later may also be adopted. Further, the inlet 110 for supplying the coolant is shown to be a hole penetrating from the outer peripheral surface to the inner peripheral surface of the first member. Further, the outlet 170 for discharging the coolant is a hole penetrating from the inner peripheral surface to the outer peripheral surface of the first member, although part of it is hidden.

[0050] What is characteristic in FIG. 5 is that the helical groove portion 130 and the helical convex portion (fin) 140 are provided. The helical groove portion 130 can be formed by cutting with respect to the inner peripheral surface 160 of the first member, and can also be formed using a high-precision 3D printer. The helical convex portion (fin) 140 is on the same surface as the inner peripheral surface 160 of the first member, and is formed secondarily when forming the helical groove portion 130.

[0051] The front opening 105 is an opening for inserting the second member described later. Further, the rear opening 104 is an opening for exhausting the combustion gas from the injection port of the nozzle provided inside the second member, and is set to a size larger than the diameter of the nozzle of the second member. In FIG. 5, the shape of the rear opening 104 is drawn as a quadrilateral, but it is not limited to this shape, and polygons such as triangles and pentagons, or circles, ellipses, etc. can be freely selected.

[0052] The thick arrows in Fig. 5 indicate the flow of the coolant. The thick white arrows indicate the coolant in a cooled state, and the thick gray arrows indicate the coolant in a warmed state due to heat exchange during the cooling of the nozzle. Note that, as will be described later, in order for the coolant to flow, the groove formed on the inner peripheral surface of the first member alone is not sufficient, and it is necessary to form a cooling channel by fitting the outer peripheral surface of the second member, which will be described later, with the groove of the first member. Therefore, it should be noted that the following description includes an explanation of the flow of the coolant when the cooling channel is formed.

[0053] The thick white arrow indicates the state in which the coolant supplied from the inlet 110 once enters the introduction zone 120 and then flows into the helical groove 130 (cooling channel) from the cooling channel inlet 132 through the introduction zone 120. Thereafter, the coolant in the warmed state after cooling the nozzle flows from the helical groove 130 (precisely, the cooling channel described later) into the recovery zone 150 and is discharged from the outlet 170 to the outside of the first member. Also, the introduction zone and the recovery zone may be replaced with an inverse positional relationship. This is the same as the fact that the inlet and the outlet may be replaced with an inverse positional relationship. For this reason, in the figures after Fig. 5, the introduction zone (or the recovery zone), or the recovery zone (or the introduction zone) is expressed.

[0054] Note that although the details regarding the concept of the number of channels will be described later, in Fig. 5, the description of the cooling channel inlet (CH2) indicates that the cooling channel is configured for each channel. The number of channels n can be appropriately set as an integer of 1 or more, but as will be described later, it is preferable to select a numerical value within a predetermined range from the viewpoints of cooling performance and prevention of overheating of the coolant.

[0055] 1-2-4. Configuration of the First Member (Cross-Sectional View B-B) (Fig. 6) Fig. 6 is a view showing an example of the configuration of the first member of the present invention and is a cross-sectional view B-B. Since the configuration of each part is the same as that in Fig. 5, the description of overlapping parts will be omitted. The dimensions of each part can be freely determined according to the size and output of the rocket. As an example, when the total length of the first member is about 60 mm, the diameters C1 and C2 of the coolant inlet 110 and outlet 170 can be set to about 5 mm. Also, as an example, the width (K1) of the introduction zone 120 and the width (K2) of the recovery zone 150 can be set to about 9 mm, the diameter (D1Nd) of the inner peripheral surface of the first member can be set to about 35 mm, and the diameter (D1Kd) of the rear opening of the first member can be set to about 14 mm. Also, as an example, the thickness (D1) of the body part of the first member can be set to about 7 mm and (D2) can be set to about 3 mm.

[0056] 1-2-5. Configuration of the First Member (Cross-Sectional View A-A) (Fig. 7) Fig. 7 is a view showing an example of the configuration of the first member of the present invention and is a cross-sectional view A-A. Since the configuration of each part is the same as that in Figs. 5 and 6, the description of overlapping parts will be omitted. As described above, the cooling channels can be provided for each channel, and the number of channels n can be appropriately set as an integer of 1 or more. In Figs. 5 to 7, the case where the number of channels n = 3 is illustrated (hereinafter, the channel may be abbreviated as "CH" in some cases). Therefore, in Fig. 7, the cooling channel inlet (CH1) 131 and the cooling channel inlet (CH3) 133 are shown. It is desirable that the inlets of each cooling channel be arranged at equal intervals. For example, when the number of channels n = 3 CH, they are arranged at equal intervals every 120 degrees (see Fig. 20(2)). In the prior art, there is no description or suggestion regarding the point that "by configuring the cooling channels for each channel and then adjusting the number of channels, it is possible to contribute to the cooling performance and prevention of overheating of the coolant" (see the specifications of Patent Document 1 and Patent Document 2, and Figs. 1 and 2 of the drawings of the present application).

[0057] 1-3. Configuration of the Second Member 1-3-1. Configuration of the Second Member (Perspective View, Front View) (Fig. 8) Fig. 8 is a diagram showing an example of the configuration of the second member of the present invention, where Fig. 8(1) is a perspective view and Fig. 8(2) is a front view. The second member has a smooth outer peripheral surface 260 and is inserted inside the first member. By fitting the inner peripheral surface 160 of the first member and the inner peripheral surface 260 of the second member flush, it is used to form a cooling channel through which the coolant passes. According to Fig. 8(1), it can be seen that the outer peripheral surface 260 of the second member has substantially the same shape (cylindrical shape) as the inner peripheral surface 160 of the first member. Also, a nozzle portion 280 through which the high-temperature combustion gas of the rocket engine passes may be provided inside the second member, and a nozzle exit 284 is shown in Fig. 8(1).

[0058] According to Fig. 8(2), when the second member has a substantially cylindrical shape, it can be seen that it has a substantially rectangular shape when viewed from the front. Therefore, since the plan view, rear view, and bottom view are all of the same shape, the description is omitted.

[0059] 1-3-2. Configuration of the Second Member (Cross-sectional View, Right Side View) (Fig. 9) Fig. 9 is a diagram showing an example of the configuration of the second member of the present invention, where Fig. 9(1) is a C-C cross-sectional view and Fig. 9(2) is a right side view. According to Fig. 9(1), an example is described when a nozzle portion 280 is provided inside the second member. As a general rule, the shape of the nozzle inside the second member adopts a tapered shape with a circular cross-section. The diameter (nsd) of the throat portion 290 is configured to be constricted with respect to the diameter (nid) of the nozzle inlet 282. This is to increase the pressure in the combustion chamber on the left side of the nozzle and to increase the flow velocity of the injected combustion gas by constricting the diameter, thereby improving the thrust.

[0060] The dimensions of each part can be freely determined according to the size and output of the rocket. As an example, when the total length (nL) of the second member is about 60 mm and the diameter is about 35 mm, the inlet diameter (nid) can be set to 10 - 30 mm, the throat diameter (nsd) to 5 - 8 mm, the outlet diameter (nod) to 10 - 30 mm, etc. Also, as an example, the distance (dsl) from the inlet to the throat part can be set to 25 - 35 mm, and the distance (D2ds) from the outer peripheral surface 260 of the second member to the throat part 290 can be set to about 10 - 15 mm.

[0061] Here, it can be seen that the distance (D2ds) from the outer peripheral surface 260 of the second member to the throat part 290 is approximately equal to the predetermined distance (ds) from the cooling channel to the nozzle throat part 290. Note that although details will be described later, the distance (D2ds) from the outer peripheral surface 260 of the second member to the throat part 290, or the distance (ds) from the cooling channel to the throat part (not shown in Fig. 9, refer to Fig. 15) is an important parameter for balancing the cooling performance of the nozzle part and preventing the coolant from overheating in relation to the thermal conductivity of the material of the second member.

[0062] Fig. 9(2) is a right side view of the second member, showing the shape of the outer peripheral surface 26 of the second member (substantially cylindrical), the shape of the nozzle outlet 284 (substantially circular), and the shape of the throat part 290 existing at the back (substantially circular).

[0063] 1-3-3. Configuration of the second member (left side view, cross-sectional view) (Fig. 10) Fig. 10 is a diagram showing an example of the configuration of the second member of the present invention, where Fig. 10(1) is a left side view and Fig. 10(2) is a D-D cross-sectional view. According to Fig. 10, the nozzle inlet 282, the throat part 290, and the shape of the outer peripheral surface of the second member are shown.

[0064] 2. Regarding the configuration in a state where the first member and the second member are combined 2-1. Overview The above has described the first member and the second member individually. Next, the cooling device for a rocket engine nozzle of the present invention in a state where both are combined will be described below.

[0065] 2-2. Fitting between the first member and the second member (Fig. 11) Fig. 11 is a diagram showing an example of the state when the first member and the second member of the present invention are fitted together. By setting the diameter (D1Nd) of the inner peripheral surface of the first member and the diameter (D2Gd) of the outer peripheral surface of the second member to be substantially the same, the two members are fitted flush. In practice, considering the workability during fitting, it is desirable to set the diameter (D1Nd) of the inner peripheral surface of the first member to be slightly larger than the diameter (D2Gd) of the outer peripheral surface of the second member by a micron unit.

[0066] 2-3. Appearance when the first member and the second member are combined (Fig. 12) Fig. 12 is a perspective view showing an example of the nozzle cooling device in which the first member and the second member of the present invention are combined. According to Fig. 12, an example of the positional relationship between the coolant inlet 110 and the outlet 170 is shown. Also, the state where the shape of the nozzle outlet 284 of the nozzle portion 280 provided inside the second member can be seen from the rear opening 104 of the first member is shown. Note that bolt holes (through holes) for fixing the nozzle case may be provided in the flange portion 102.

[0067] 2-4. Internal structure when the first member and the second member are combined (cross-sectional perspective view) (Figs. 13 and 14) Fig. 13 is a perspective view of the B-B cross-section showing an example of the nozzle cooling device in which the first member and the second member of the present invention are combined. FIG. 14 is a view showing an example of a B-B cross section of a cooling channel formed by flush fitting a helical groove or protrusion of a first member of the present invention with an outer peripheral surface of a second member, and is an enlarged view (perspective view). According to FIGS. 13 and 14, a state where the inner peripheral surface 160 of the first member and the outer peripheral surface 260 of the second member are flush-fitted is shown.

[0068] Further, a helical groove 130 and a helical protrusion (fin) 140 are provided on the inner peripheral surface of the first member, and it is shown that the helical groove 130 functions as a cooling channel 135 by the helical protrusion (fin) 140 being in surface contact with the outer peripheral surface 260 of the second member. Here, "helical" means a coiled shape, and "helical cooling channel" means a coiled cooling channel composed of one or a predetermined number of channels.

[0069] It is also shown that an introduction zone 120 (or a recovery zone) is formed by a widened groove provided on the inner peripheral surface 160 of the first member and the outer peripheral surface 260 of the second member. The introduction zone (or recovery zone) 120 has an annular structure without twist, unlike the helical cooling channel, and plays a role of introducing the coolant to the inlets of the individual cooling channels by once pooling the coolant (see FIG. 17). The recovery zone (or introduction zone) 150 plays a role of recovering the coolant from the outlets of the individual cooling channels and has the same configuration as the introduction zone (or recovery zone) 120.

[0070] It can be seen that the coolant supplied from the inlet 110 flows into the introduction zone 120 formed by the groove provided on the inner peripheral surface 160 of the first member and the outer peripheral surface 260 of the second member. The coolant that has flowed into the introduction zone 120 flows into each cooling channel through cooling channel inlets (CH1) 131, (CH2) 132,... provided for each channel (not shown in FIG. 13, so refer to FIGS. 6 and 7). Further, the heated coolant after cooling the nozzle by passing through the cooling channels is discharged to the outlet 170 through a recovery zone 150 having the same structure as the introduction zone 120. As shown in FIG. 13, the introduction zone 120 and the recovery zone 150 are configured in an annular shape so as to surround the outer peripheral surface 260 of the second member.

[0071] The dimensions of each part can be freely determined according to the size and output of the rocket. As an example, when the length (nL) of the second member is about 60 mm and the diameter is about 35 mm, the depth (chd) of the cooling channel 135, the width (wch) of the cooling channel, and the width (wf) of the fin can be set to about 1 mm.

[0072] 2-5. Internal Structure (Cross-Sectional View) When the First Member and the Second Member are Combined (FIG. 15) FIG. 15 is a view showing an example of a nozzle cooling device in which the first member and the second member of the present invention are combined, and is a cross-sectional view taken along line B-B. According to FIG. 15, it can be seen that in the cooling device of the present invention, a predetermined distance (ds) (substantially equal to the distance (D2ds) from the outer peripheral surface of the second member to the throat portion) is ensured from the cooling channel 135 to the throat portion 290 of the nozzle. In this regard, it can be seen that this is significantly different from the prior art Patent Document 1 (see FIG. 1) and Patent Document 2 (see FIG. 2), in which the cooling channels are formed in close contact with the nozzle portion along the tapered shape of the nozzle portion.

[0073] Also, in the cooling device of the present invention, it can be seen that the portion where the helical cooling channel 135 is formed is set to a predetermined effective width (hw) with a short width with respect to the total length (nL) of the second member (corresponding to the nozzle). In this regard, it can be seen that this is significantly different from the prior art Patent Document 1 (see FIG. 1) and Patent Document 2 (see FIG. 2), in which the cooling channels are provided over the entire length of the nozzle portion or the combustion chamber.

[0074] Next, looking at the positional relationship between the arrangement of the helical cooling channel 135 and the throat portion 290 of the nozzle, it can be seen that the arrangement of the helical cooling channel 135 is configured to include the center of the throat portion of the nozzle. This is because the vicinity of the throat portion 290 of the nozzle becomes the hottest, and cooling this portion as the center helps prevent erosion of the throat portion.

[0075] Also, in the prior art, if the effective width of the helical cooling channel 135 is made longer than necessary, the coolant flowing through the cooling channel will be overheated. Therefore, when nitrous oxide is used as the coolant, there is a specific problem that an explosive phenomenon occurs in the nitrous oxide, and there is a risk of destruction of the cooling channel and the nozzle portion (especially the throat portion). Therefore, setting the effective width (hw) of the cooling channel to a width shorter than the total length (nL) of the nozzle, for example, 1 / 3 to 1 / 2 of the total length (nL) of the nozzle, is a consideration in view of such problems.

[0076] 2-6. Regarding the flow of the coolant in the cooling device of the present invention (FIG. 16) FIG. 16 is a diagram showing an outline of the flow of the coolant using FIG. 13 which shows an example of a nozzle cooling device combining the first member and the second member of the present invention. When a coolant in a cooled state (thick white arrow) is supplied to the inlet 110, it shows a state where the coolant in a warmed state after absorbing the heat of the nozzle and exhibiting a cooling function is discharged from the outlet 170 (not shown).

[0077] 2-7. Regarding the flow of the coolant in the cooling device of the present invention (schematic diagram with the second member made transparent) (FIG. 17) Since the flow of the coolant inside the cooling device is difficult to understand when the second member is present, the second member is made transparent and the flow of the internal coolant is described using FIG. 17. FIG. 17 is a diagram obtained by making the second member transparent in FIG. 16 and visualizing the flow of the internal coolant. According to FIG. 17, it shows how the coolant is supplied from the inlet 110 and introduced into the inlet of the cooling channel for each channel through the introduction zone 120. More specifically, it shows how it is introduced into the inlet 132 of the cooling channel of channel 2 (CH2).

[0078] It should be noted that the coolant (thick white arrow) introduced into the cooling channel flows through the cooling channel at a position a predetermined distance (ds) away from the nozzle part 280 and the throat part 290 provided inside the second member, so it will not be overheated (see FIG. 15). Also, through heat exchange via the second member composed of a material with a predetermined thermal conductivity, the nozzle part 280 and the throat part 290 can be sufficiently cooled, so it is possible to suppress erosion of the throat part. The coolant (thick gray arrow) heated by the heat from the nozzle part is output for each channel from the outlet of the cooling channel, recovered through the recovery zone 150, and discharged to the outside of the cooling device from the outlet 170.

[0079] Here, considering the case where there is no introduction zone 120, since cooling channels are provided for each channel and there are multiple inlets to the cooling channels, it can be seen that it is somewhat difficult to introduce the coolant evenly. Therefore, by providing the introduction zone 120, it becomes possible to introduce the coolant evenly into the inlets (CH1, CH2, ···) of the cooling channels of each channel. Regarding the recovery zone 150 as well, since it is the same in terms of covering the recovery of the heated coolant from the cooling channels provided for each channel, the description is omitted.

[0080] 2-8. Enlarged view of the helical structure (in the case of 3CH) (FIG. 18) FIG. 18 is an enlarged view of the "introduction part to the inlet of the cooling channel" (dotted line part) in FIG. 17, and it is a diagram showing the configuration of the helical cooling channel composed of helical groove parts and convex parts. It is also a diagram showing an example of the flow of the coolant in each cooling channel when the number of channels n of the cooling channels is 3.

[0081] According to FIG. 18, the state where the coolant is introduced from the channel inlet (CH1) of the cooling channel of channel 1 is shown. When the number of channels n = 3, it can be seen that the helical cooling channels are arranged in order from the top for channel 1, for channel 2, and for channel 3. This is shown by the thick white arrows, and it is shown that the coolant flows only through the helical cooling channels of channel 1 arranged every other one.

[0082] It is shown that the width of the channel inlet (CH1) of the cooling channel is substantially the same as the width of the cooling channel (see FIG. 14), but it is not limited to this. For example, when the number of channels is small, since there is a distance to the inlet of the next channel, it may be expanded to some extent in the expanding direction (dotted arrow) of the opening of the channel inlet in FIG. 18 to form a wider width of the inlet.

[0083] 2-9. Enlarged view of the helical structure (in the case of 2CH) (FIG. 19) FIG. 19 is an enlarged view of the "introduction part to the inlet of the cooling channel" (dotted part) in FIG. 17, and it is a diagram showing the configuration of the helical cooling channel composed of a helical groove part and a convex part. At the same time, it is a diagram showing an example of the flow of the coolant in each cooling channel when the number of channels of the cooling channel is 2. The difference between FIG. 19 and FIG. 18 is the difference in whether the number of channels n of the cooling channel is 3 or 2. When the number of channels n = 2, it can be seen that the helical cooling channels are arranged in order from the top for channel 1 and for channel 2. This is shown by the thick white arrows, and it is shown that the coolant flows only through the helical cooling channels of channel 1 arranged every other one. As described above, examples for the cases of the number of channels n = 2 and 3 have been shown in FIGS. 18 and 19, but the same applies to the case where the number of channels n is 4 or more.

[0084] 2-10. Image of the difference in configuration due to the difference in the number of helical cooling channels (FIG. 20) FIG. 20 is a diagram showing an example of an image of the difference in the configuration of the cooling channels due to the difference in the number of the cooling channels. FIG. 20(1) illustrates an image in which a coolant flows through one cooling channel in the case where the number of channels n = 1. FIG. 20(2) illustrates an image in which a coolant flows through three cooling channels in the case where the number of channels n = 3. Each channel is arranged in a staggered pattern, and it is illustrated so as to be able to image how the arrangement of each channel shown in FIG. 18 is three-dimensionally configured. In this case, it can be seen that it is preferable to arrange the inlets of each channel every 120 degrees.

[0085] 2-11. Example of a cross-sectional view when the first member and the second member are combined in the case where the second member has a two-part structure (FIG. 21) FIG. 21 is a diagram showing an example of a cooling device in which the first member and the second member of the present invention are combined, and is a perspective cross-sectional view taken along line B-B. As the second member, in addition to the case where it has an integral structure up to the internal nozzle portion, as shown in FIG. 21, it may have a structure that is divided into two parts separately from the nozzle portion. For example, an annular member is provided outside the second member to adjust the thermal conductivity or the like.

[0086] 2-12. Example of a cross-sectional view when the first member and the second member are combined in the case where the second member has a two-part structure (FIG. 22) FIG. 22 is a diagram showing an example of a cooling device in which the first member and the second member of the present invention are combined, and is a cross-sectional view taken along line B-B. A modified example of the two-part structure of the second member is shown.

[0087] 2-13. Configuration Example of the Second Member in the Case where the Second Member has a Two-part Structure (Fig. 23) Fig. 23 is a diagram showing an example of the second member of the present invention, and is a diagram showing an example of a modified example of a two-part structure of the second member. In addition, in Figs. 21 to 23, the case where the second member has a two-part structure is shown as an example. In short, as long as the inside of the first member includes a structure whose outer peripheral surface is flush with the inner peripheral surface of the first member and a structure corresponding to the nozzle, that is sufficient.

[0088] 2-14. Example of the First Member in a Modified Example of a Tapered Shape where the Entrance is Wide and Narrows towards the Exit (Figs. 24, 25) Figs. 24 and 25 are diagrams showing an example of the first member of the present invention, and are diagrams showing an example of a modified example in the case of a tapered shape where the entrance is wide and narrows towards the exit on the inner peripheral surface of the first member. Fig. 24 is a perspective view of the B-B cross section, and Fig. 25 is a cross-sectional view of the B-B cross section. According to Figs. 24 and 25, it can be seen that even in the case of a tapered shape where the entrance (front open portion 105) is wide and narrows towards the exit, a helical groove portion and a convex portion can be formed.

[0089] 2-15. Example of the Second Member in a Modified Example of a Tapered Shape where the Entrance is Wide and Narrows towards the Exit (Figs. 26, 27) Fig. 26 is a diagram showing an example of the second member of the present invention, and is a diagram showing an example of a modified example in the case of a tapered shape where the entrance is wide and narrows towards the exit on the outer peripheral surface of the second member. (1) is a cross-sectional view of the C-C cross section, and (2) is a perspective view. Also in the second member combined with the first member of Figs. 24 and 25, by making the shape tapered where the entrance is wide and narrows towards the exit, the two can be combined.

[0090] In this case, when the two are combined, the configuration as shown in Fig. 27 is obtained. FIG. 27 is a view showing an example of a cooling device in which a first member and a second member of the present invention are combined, and is a B-B cross-sectional view showing an example in the case of a tapered shape in which the inlet is wide and the outlet is narrow on the inner peripheral surface of the first member, and a modified example in the case of a tapered shape in which the inlet is wide and the outlet is narrow on the outer peripheral surface of the second member are combined. According to FIG. 27, it can be seen that by combining the first member and the second member, a helical cooling channel 135 can be formed, and an introduction zone 120 and a recovery zone 150 can be formed.

[0091] 2-16. Modified example of a tapered shape in which the inlet is narrow and the outlet is wide (FIGS. 28 to 30) FIGS. 28 and 29 are views showing an example of a first member of the present invention, and are a B-B cross-sectional perspective view and a B-B cross-sectional view showing an example of a modified example in the case of a tapered shape in which the inlet is narrow on the inner peripheral surface of the first member. Further, FIG. 30 is a view showing an example of a second member of the present invention, and is a view showing an example of a modified example in the case of a tapered shape in which the inlet is narrow and the outlet is wide on the outer peripheral surface of the second member. (1) is a C-C cross-sectional view, and (2) is a perspective view. According to FIGS. 28 to 30, it can be seen that even in the case of a tapered shape in which the inlet is narrow and the outlet is wide, a helical cooling channel 135 can be formed, and an introduction zone 120 and a recovery zone 150 can be formed.

[0092] 3. Configuration of the regenerative cooling system Next, the configuration when the nozzle cooling device of the present invention is used in a regenerative cooling system will be described. 3-1. Configuration example when the nozzle cooling device of the present invention is combined with a hybrid rocket engine body (FIGS. 31 to 33)

[0093] FIGS. 31 and 32 are views showing an example of the use of a nozzle cooling device in which a first member and a second member of the present invention are combined, and are a perspective view and a plan view showing an example when combined with a hybrid rocket engine body. As shown in FIGS. 31 and 32, the nozzle cooling device of the present invention is connected to the hybrid rocket engine via the flange portion 102.

[0094] FIG. 33 is a diagram showing a usage example of the nozzle cooling device in which the first member and the second member of the present invention are combined, and is a cross-sectional view showing an example when combined with the hybrid rocket engine main body. The hybrid rocket engine 400 includes an injector 410 that injects an oxidizer, an ignition device 420 that ignites the oxidizer and fuel, a solid fuel 430, a combustion chamber 440, and an oxidizer inlet 450. In the combustion chamber 440, high-temperature combustion gas is generated by the reaction of the solid fuel and the oxidizer.

[0095] By narrowing down at the throat portion 290 which is the narrowest portion of the nozzle portion 280, the pressure in the combustion chamber 440 is increased to promote combustion, and the speed of the combustion gas after passing through the throat portion 290 is accelerated to supersonic speed to increase the thrust. Therefore, the vicinity of the throat portion 290 is exposed to high-temperature combustion gas, and there is a risk of thermal shock damage and erosion deformation, and as a result, it may have a fatal impact on its propulsion performance. Therefore, it is necessary to suppress the erosion of the nozzle portion 280 (especially the throat portion 290) by using the nozzle cooling device of the present invention as described above.

[0096] On the other hand, in the case of a hybrid rocket engine, after all, combustion is maintained by the phenomenon of boundary layer combustion occurring in the boundary layer several millimeters from the surface of the solid fuel. Therefore, different from the combustion where the flame and the fuel are several tens of micrometers as in the case of solid propellants and liquid propellants, the heat supply to the fuel is not always sufficient.

[0097] In order to improve this, as an oxidizer, instead of relatively safe liquid oxygen or hydrogen peroxide, it is effective to supply a high amount of heat to the fuel by using nitrous oxide, which becomes a mixed gas with an oxygen partial pressure higher than that of the atmosphere when thermally decomposed. However, on the other hand, nitrous oxide may cause explosive phenomena due to a rapid temperature rise, which may lead to fatal damage to the cooling channels and nozzle parts.

[0098] Although the combination of the above-mentioned multiple problems makes it difficult to solve the problems, the research team of the present invention has attempted to solve the problems by making the following improvements in order to suppress the rapid temperature rise while using nitrous oxide. <List of Improvements> First, providing a helical cooling channel Second, providing a distance between the cooling channel and the nozzle part Third, adjusting the effective width of the cooling channel to an appropriate range Fourth, providing a helical cooling channel for each channel Fifth, optimizing the number of channels of the helical cooling channel Sixth, adjusting the thermal conductivity of the material around the nozzle to an appropriate range Seventh, optimizing the position of the orifice to stably use nitrous oxide in the cooling channel

[0099] In addition, it should be further noted that in the prior art, for example, in Patent Document 1 and Patent Document 2, it is considered that at least the above-mentioned second to seventh problems have not been recognized (see FIGS. 1 and 2). In short, the main purpose is to enhance the cooling performance. Considering the necessity of using nitrous oxide in consideration of the combustion characteristics of the hybrid rocket engine and the risks associated with using nitrous oxide, it can be evaluated that there is no consideration for the specific problems of the hybrid rocket engine, such as achieving both cooling performance and prevention of overheating of the coolant.

[0100] Since the first to fourth improvements have been described above, in the following, the fifth to seventh improvements will be mainly described.

[0101] 3-2. Configuration Example of the Regenerative Cooling System of the Present Invention (FIGS. 34 to 36) Figure 34 is a diagram showing an example of use of a nozzle cooling device that combines the first and second members of the present invention, and is a perspective view showing an example of a regenerative cooling system configuration that is combined with the hybrid rocket engine body and includes piping for the coolant and oxidizer.

[0102] In FIG. 34, the piping up to the inlet 110 is omitted, but the outlet 170 is connected to the oxidizer inlet 450 of the hybrid rocket engine 400 by an oxidizer piping section 530 . The coolant is supplied to the inlet 110, and after cooling the nozzle, it is discharged from the outlet 170 and delivered to the oxidizer inlet 450, and is ultimately used as an oxidizer to promote combustion in the rocket engine in space. In that sense, it is referred to as a coolant (and oxidizer).

[0103] Next, an example of the configuration of the regenerative cooling system of the present invention will be described with reference to FIGS. FIG. 35 shows an example of the use of a nozzle cooling device that combines the first and second members of the present invention, and is a diagram showing an example of a regenerative cooling system configuration that includes piping for coolant or oxidizer and the arrangement of a phase change orifice in combination with the hybrid rocket engine body. In Figure 35, the dotted arrows indicate the coolant in the liquid phase, the hollow arrows indicate the coolant in the vapor phase, and the gray arrows indicate the warmed coolant (vapor phase).

[0104] FIG. 36 shows a comparative experiment example in which the position of the orifice in FIG. 35 is changed and the coolant used for regenerative cooling is used in liquid phase. In FIG. 36, the dotted, filled thick arrows indicate coolant in the liquid phase, and the gray thick arrows indicate coolant in the warmed state (liquid phase or gas phase).

[0105] In Figures 35 and 36, the symbol T indicates the location of the temperature sensor, and P indicates the location of the pressure sensor. There are multiple temperature sensors near the nozzle because they are placed at different distances to the nozzle. The temperature sensors are installed in multiple holes drilled inside the second member at each distance to the nozzle. In FIG. 35, it can be seen that the phase change orifice 510 is located between the coolant (and oxidant) tank 500 and the nozzle cooling device 300 . When the liquid-phase coolant passes through the phase change orifice 510, it vaporizes and changes to a gas phase. Therefore, in the configuration of Figure 35, the coolant is supplied to the inlet 110 of the nozzle cooling device 300 in a gas phase (gaseous state). This is different from the case in Figure 36, in which the phase change orifice 510 is placed after the nozzle cooling device 300 and just before the hybrid rocket engine 400, and the fuel is supplied to the inlet 110 in a liquid phase state (liquid state), the same as the state inside the tank.

[0106] Generally speaking, it is estimated that the cooling effect is higher in the liquid phase due to specific heat, so it was estimated that the configuration in Figure 36 is more advantageous for cooling than the configuration in Figure 35, which supplies water in a gas phase. However, the research team of the present invention has demonstrated that the gas phase state of FIG. 35 has a high cooling effect (the experimental results will be described later), so it is desirable to adopt the configuration of FIG.

[0107] The reason for the high cooling effect in the gas phase is thought to be that after the coolant is supplied to the inlet 110, its temperature rises due to heat exchange with the nozzle section in the helical cooling channel 135, which is closely related to the following properties of nitrous oxide: Nitrous oxide has a high vapor pressure (approximately 50 bar) at room temperature, so as the temperature rises due to heat exchange, the rate at which it vaporizes increases. At the same time, bubbles are generated by the vapor pressure of the vaporized nitrous oxide, resulting in a mixture of liquid and bubbly states, which is thought to be the cause of the decline in cooling performance. However, when comparing the two, the cooling performance of the configuration in Fig. 35 is higher than that of the configuration in Fig. 36. In any case, the effects of the nozzle cooling device of the present invention can be fully expected.

[0108] 4. Regarding the configuration of the helical cooling channel and the range of the number of channels 4-1. Regarding the difference in structure due to the difference in the number of channels Next, regarding the configuration of the helical cooling channel and the number of channels of the present invention, it will be described with reference to Figs. 37 to 40. Fig. 37 is a diagram showing the difference in the configuration of the helical cooling channel due to the difference in the number of channels of the cooling channel. (1) shows the case where the number of channels is a predetermined number, and (2) is a diagram showing the case where the number of channels is increased compared to (1). Fig. 38 is a diagram showing the relationship between the number of channels n and the turning angle α in the case of a helical cooling channel.

[0109] As shown in Fig. 37, in the case of a helical cooling channel, even if the number of channels n increases, the flow path cross-sectional area (proportional to the width Wch of the channel) does not change. However, it can be seen that the larger the number of channels n, the smaller the wetting surface (Wca, dx), and the larger the turning angle α. Fig. 38 shows the relationship between the number of channels n and the turning angle α. According to Fig. 38, when the total length of the nozzle is 60 mm and the width of the channel (Wch) is 1 mm, when the number of channels n reaches 60 CH, the turning angle α becomes 90 degrees, indicating that it has the same structure as the cooling channel in the axial direction (straight) of the nozzle.

[0110] Fig. 39 is a diagram showing the difference between the case of a helical cooling channel and the case of an axial cooling channel, and is a diagram showing the change tendency of the pressure loss (Δp) and the Nusselt number (Nu). As described in the explanation of the balloon in the figure, according to FIG. 39, in the case of a helical cooling channel, since the Nusselt number (heat transfer by convection × representative length / thermal conductivity of the fluid) is constant, even if the number of channels is increased, only the axial projection of the channel cross-sectional area decreases, and the cross-sectional area perpendicular to the flow velocity is constant, so it is shown that the rate of heat transfer does not change. Also, in the case of a helical cooling channel, it is shown that increasing the number of channels reduces the pressure loss (makes the flow easier).

[0111] Therefore, according to FIGS. 37 to 39, in the case of a helical cooling channel, even if the number of channels is increased, while the rate of heat transfer does not change and the pressure loss decreases, the wet surface (Wca, dx) decreases and the cooling efficiency decreases. So, it can be said that a small number of channels, for example, about 2 to 8 channels, is preferable (refer to the results of the experimental examples described later).

[0112] FIG. 40 is a diagram showing a calculation formula related to the configuration of a helical cooling channel. Equation (1) shows a calculation formula for the turning angle α, which corresponds to the graph in FIG. 38. [[ID=!4]]For example, when the number of channels n = 3, the turning angle α can be calculated to be about 3 degrees. Equation (2) shows a calculation formula for the pitch (Lp) of the helical groove. Equation (3) shows a calculation formula for the total number of pitches (Np). Equation (4) shows a calculation formula for the channel length (Lch). When substituting Equations (2) and (3), when the length of the nozzle (Ln) is 60 mm, the channel length (Lch) of the helical cooling channel is calculated to be about 1 m. From this, it can be seen that the channel length (flow path length) of the helical cooling channel is about 17 times the axial flow path length.

[0113] Further, Equation (5) is an equation regarding the pressure loss Δp of turbulent flow in the pipe (definition of Darcy-Weisbach friction coefficient) and the convective heat transfer coefficient (Dittus-Boelter equation) as a calculation formula for evaluating the influence of the number of channels n on the capacity of the cooling system, and corresponds to the graph in FIG. 39.

[0114] 4-2. Regarding the nozzle temperature, fluid heat transfer coefficient, and pressure loss due to the difference in the number of channels Next, with reference to FIG. 41, the nozzle temperature, liquid heat transfer coefficient, and pressure loss when the number of channels n is changed will be described. FIG. 41 shows (a) the nozzle temperature, (b) the heat absorption per unit flow rate, (c) the fluid heat transfer coefficient (coolant heat transfer coefficient), and (d) the pressure loss and gas volume fraction due to the difference in the number of channels when the pressure and temperature of the coolant at the inlet 110 are 23 bar and 119 K (about -154°C).

[0115] Hereinafter, based on FIG. 41, the number of channels n will be examined for three patterns of 3, 6, and 8. FIG. 41(a) shows the nozzle temperature at each position corresponding to a nozzle length of 60 mm for each number of channels. According to FIG. 41(a), the case of the number of channels n = 3 has the highest cooling effect. Even in the case of the number of channels n = 8, the maximum temperature is slightly lower than 1400 K (about 1127°C), which is the critical temperature for nozzle erosion, indicating that a certain cooling performance can be ensured.

[0116] Although the data for the case of the number of channels n = 2 are not shown, since the cooling performance is considered to be equivalent to that of the case of the number of channels n = 3, the research team of the present invention has determined that it is practical in the range of the number of channels n = 2 to 8. Next, in relation to the pressure loss, when used as an oxidizer for a hybrid rocket engine, the problem is the range in which it can withstand practical use without using a pressurizing pump.

[0117] Regarding this point, as described above, in the case of a helical cooling channel, based on FIGS. 37 to 39, even if the number of channels is increased, while the rate of heat transfer remains unchanged and the pressure loss decreases, the wetting surface (Wca, dx) decreases and the cooling efficiency decreases. Therefore, it was shown that it is preferable to have a small number of channels, for example, about 2 to 8 channels. Certainly, as shown in FIG. 41(b), it can be seen that as the number of channels n increases, there is a tendency for the amount of heat absorbed per unit flow rate to decrease, which is consistent with the relationship that the wetting surface (Wca, dx) decreases.

[0118] Also, FIG. 41(c) shows the tendency of change in the liquid heat transfer rate (for the cases of the number of channels n = 3, 6, 8) at each position corresponding to the axial length of 60 mm of the nozzle.

[0119] Further, FIG. 41(d) shows the tendency of change in pressure and gas volume fraction (for the cases of the number of channels n = 3, 6, 8) at each position corresponding to the axial length of 60 mm of the nozzle. Regarding the tendency of pressure change, as expected, it significantly decreases in the case of 3CH, but does not decrease much for 6CH and 8CH. More specifically, it can be seen that the pressure loss decreases as the number of channels n increases, being 13.5 bar (3CH), 1.0 bar (6CH), and 0.5 bar (8CH). Also, regarding the gas volume fraction, it can be seen that it gradually decreases from 0.96 (3CH) to 0.70 (6CH) and 0.4 (8CH).

[0120] As described above, by increasing the number of channels in the cooling system, advantages can be observed in terms of pressure loss, but it can be seen that the cooling performance gradually decreases and the probability of nozzle erosion increases. Therefore, although it may be possible to withstand practical use up to about 1 to 10 channels or so, it is considered preferable to have about 2 to 8 channels. Also, in this case, the range of the swirl angle α is about 2 to 10 degrees (see FIG. 38).

[0121] 5. Regarding the thermal conductivity of the members constituting the nozzle When the nozzle portion 280 is formed inside the second member, the cooling performance changes depending on the material of the second member, and the performance of preventing erosion of the nozzle portion 280 also changes. Also, when the nozzle portion is formed inside the second member, depending on the material of the second member, the performance of suppressing the coolant from being excessively heated by heat exchange with the nozzle portion 280 (especially the throat portion 290) and causing an explosive phenomenon to occur changes. In the nozzle cooling device of the present invention, graphite is selected as the material of the second member.

[0122] Graphite is a mass of carbon formed by being subjected to high-temperature heat treatment called graphitization and having a regular arrangement. Graphite is an anisotropic material with different properties depending on the direction, because the Z-axis direction is the bonding by intermolecular bonds, resulting in a lower thermal conductivity compared to the X-axis and Y-axis directions. Therefore, although the thermal conductivity of graphite as a single material is generally 100 - 250 W / (m·K), the thermal conductivity varies depending on the laminated state and thickness of graphite. Also, graphite using isotropic graphite formed by applying equal pressure from all directions has been put into practical use, and the thermal conductivity can be controlled to some extent depending on the manufacturing method and thickness.

[0123] In the present invention, experiments were conducted in the range where the thermal conductivity between the throat portion and the cooling channel is about 20 - 130 W / (m·K) using graphite using isotropic graphite. Regarding this point, for example, in the case of copper, the thermal conductivity is as high as about 370 W / (m·K), and in the case of Inconel alloy, the thermal conductivity is as low as about 10 W / (m·K). Different from these, it has advantageous conditions for achieving a balance between cooling performance and not excessively heating the coolant in the cooling channel.

[0124] Also, regarding the heat resistance of graphite, as a single material, it is -200°C to 450°C in the air and 3000°C in a non-oxidizing atmosphere. The temperature of the combustion gas of a rocket engine is as high as 2500 °C or more. However, graphite is resistant to rapid thermal changes and its strength increases at high temperatures, so it is also suitable for the nozzle of a rocket engine.

[0125] 6. Regarding the coolant and oxidizer Figure 42 shows the convective heat transfer rate profile calculated using Bartz's correlation when the diameter of the nozzle throat region (nsd) is 10 mm, the exit diameter (nod) is 20 mm, and a nozzle skirt (corresponding to the nozzle part) is attached at the position of r (dashed line). According to Figure 42, it can be seen that the heat input (hO2) when using liquid oxygen is greater than that when using nitrous oxide as the oxidizer (hN2O).

[0126] Figure 43 summarizes the property comparison between liquid oxygen and liquid nitrous oxide. More specifically, it summarizes the main calculation results for determining whether a steady-state wall temperature Tw = 1500 K can be maintained under an oxidizer flow rate with a chamber pressure Pc = 2 MPa and an equivalence ratio φ = 1.4.

[0127] According to Figure 43, first, it is worth noting that nitrous oxide has a higher cooling capacity because it has a higher specific heat and latent heat of vaporization than liquid oxygen. Combined with the decrease in heat input to the throat part, the cooling capacity of the N2O / HDPE hybrid rocket is considered to be higher than that of the similar O2 / HDPE hybrid rocket. Also, in terms of mass, to regeneratively cool an O2 / HDPE hybrid rocket, twice as much oxidizer must be vaporized as compared to an N2O / HDPE hybrid rocket. This can also be quantified in terms of the ratio of the oxidizer flow rate that must be vaporized to achieve steady-state heat transfer at the throat.

[0128] As described above, nitrous oxide (N2O) has a critical temperature close to normal temperature at 36.5°C and there is a risk of thermal decomposition with increasing temperature. Therefore, although care is required for heating, it can be seen that it has a high effect as a coolant.

[0129] 7. Performance Evaluation of the Nozzle Cooling Device and the Regenerative Cooling System of the Present Invention Next, the performance evaluation (effects) of the nozzle cooling device and the regenerative cooling system of the present invention will be described with reference to FIGS. 44 to 49.

[0130] Graphite nozzles using isotropic graphite were used in the experiments. Three holes for inserting sheath-type thermocouple lead wires were provided in this nozzle, and the nozzle temperature was measured at positions 3, 5, 8.5, and 12 mm from the inner surface of the throat section. The total length of the nozzle was 60 mm, and the throat was configured to be located approximately in the center. The diameters of the converging inlet section, the throat section, and the outlet section were 30 mm, 6 mm, and 14 mm, respectively (see FIGS. 8 to 10).

[0131] The width and height of the helical groove portion and the convex portion were 1 mm, and the number of channels n was three channels (see FIGS. 3 to 7, 13 to 19). The helical groove portion 130 can be manufactured by a 3D printer. The coolant flows in the direction opposite to the exhaust gas of the nozzle. The heated coolant is injected into the oxidizer inlet 450 by the oxidizer piping section 530 and then into the main chamber of the hybrid rocket engine body 400 (see FIG. 34).

[0132] FIG. 44(1) is a table showing the experimental conditions. The conditions of the mass flow rates of the coolant (also serving as the oxidizer) being 8.8 g / s, 13 g / s, 21 g / s, and 27 g / s, respectively, are shown in the table of FIG. 44. For example, it can be seen that a chamber pressure of 1.6 MPa can be obtained at a mass flow rate of 27 g / s. This value is considered high for this thrust scale and can be regarded as the upper limit of this setting. In addition, additional tests without using a regenerative cooling system were also conducted and described as "Test NC (no cooling)".

[0133] As a result of the experiment, erosion of the nozzle (throat section) was not observed in all tests using regenerative cooling (see Fig. 44(2)), while erosion of the nozzle (throat section) (a part of the throat section with a circular cross-section expanded by about 20% with respect to the diameter and deformed into an ellipse, and the area also expanded by nearly 10%) was confirmed in the test without using cooling (see Fig. 44(3)).

[0134] The performance evaluation results in Figs. 45 to 46 describe the results of Test 4 in the system configuration of Fig. 35, and Fig. 47 describes the results of Test NC (no cooling) and Test 2 in the system configuration of Fig. 35. Fig. 48 shows the results of Test NC (no cooling) in the system configuration of Fig. 35. Fig. 49 shows the test results in the system configuration of Fig. 36.

[0135] Fig. 45 is a diagram showing the performance of the cooling device and the regenerative cooling system of the present invention. Fig. 45(1) shows the chamber pressure of the coolant tank during the experiment and the pressures measured upstream and downstream of the regenerative cooling system. Fig. 44(2) shows the temperatures measured upstream and downstream of the cooling system. According to Fig. 45(1), during the experiment, it shows that the pressure along the cooling system and the pressure in the chamber of the coolant tank are constant, indicating that no local decomposition or explosion phenomenon has occurred.

[0136] Also, Fig. 45(2) shows the temperatures measured upstream (Upstream) and downstream (Downstream) of the cooling system. Here, the upstream of the cooling system refers to the piping section 520 for the cooling channel, the downstream refers to the vicinity immediately after exiting the nozzle of the piping section 530 for the oxidizer, and the chamber refers to the vicinity of the oxidizer inlet 450 of the hybrid rocket engine main body 400. According to Fig. 45(2), although a steady state has not been reached at the end of the combustion time of about 25 seconds, it can be seen that there is a considerable margin up to the activation temperature of the dissociation reaction that occurs between 700 - 900 K (about 427 - 627 °C), which is the highest temperature reached, around 300 K (about 27 °C). In addition, since the injection time for one time is short, often several seconds to about 10 seconds, it is considered that there is actually an even greater margin.

[0137] Fig. 46 is a diagram showing the performance of the cooling device and the regenerative cooling system of the present invention. Fig. 46(1) shows the distance from the nozzle and the temperature. Fig. 46(2) is a diagram showing the thrust of the rocket engine during the experiment to confirm that a constant fuel injection was continuing. According to Fig. 46(1), it shows the temperature inside the nozzle (inside the second member) measured by changing the distance from the throat portion 290. Due to the implementation of the cooling system, the temperature field inside the nozzle has reached a steady state. The innermost thermocouple (close to the throat portion) has reached a steady temperature of about 900 K (about 627 °C), and the outermost thermocouple (far from the throat portion) has reached a steady temperature of about 500 K (about 227 °C). Since erosion of the throat portion 290 can be suppressed up to about 1400 K (about 1127 °C), it is considered that the experimental results fully meet the expected performance.

[0138] Also, according to Fig. 46(2), during the experiment, it shows a stable and continuous motor thrust (rocket engine output) of about 50 N, indicating that combustion at the same level has continued and that the coolant (also an oxidant) of the same flow rate has continued. Therefore, it can be inferred that the above - shown performance during the experiment can continue to be exhibited even when operating for a longer time.

[0139] FIG. 47 is a diagram for verifying the performance of the cooling device and the regenerative cooling system of the present invention. FIG. 47(1) shows the temperature (distance from the nozzle and temperature) when the cooling system is not used. FIG. 47(2) is a diagram showing the cooling effect (distance from the nozzle and temperature) by the cooling system of the present invention under the same conditions. According to FIG. 47(1), since the temperature rise continues, it can be seen that a steady state has not been achieved in this test.

[0140] Also, according to FIG. 47(1), it can be seen that the highest temperature near the throat portion 290 of the nozzle is about 1200 K (about 927 ° C), and the temperature near the metal case outside the motor (rocket engine main body) is as high as about 1000 K (about 727 ° C). Therefore, it can be seen that there is little difference from the temperature at which erosion of the throat portion 290 of the nozzle starts, and there is not enough margin. According to FIG. 47(2), when the cooling system of the present invention is used, it can be seen that an effect of a temperature drop of 800 K (800 ° C) is obtained compared with the case where it is not used.

[0141] FIG. 48 is a diagram for verifying the performance of the cooling device and the regenerative cooling system of the present invention, and shows the pressure recorded in the chamber and downstream of the cavitation point when the cooling device is not used. Cavitation refers to a state in which a liquid is vaporized by an orifice. Comparing FIG. 48 without cooling with FIG. 45(1) with cooling, it can be seen that in the test NC (without cooling) of FIG. 48, due to erosion of the nozzle, the pressure recorded in the chamber and downstream of the bubble point during combustion has decreased. The decrease in the chamber pressure reduces the function as an oxidant and inhibits combustion, which also leads to a decrease in the performance of the propulsion system.

[0142] FIG. 49 is a diagram showing the performance of the cooling device and the regenerative cooling system of the present invention when the arrangement of the orifices is changed and the cavitation point is changed as shown in FIG. 36. Fig. 49(1) shows the chamber pressure of the coolant tank. Fig. 49(2) is a diagram showing the temperature at a distance of 12 mm from the nozzle. According to Fig. 49(1), it is shown that in the system configuration of proportionality, combustion becomes unstable and pressure vibration occurs in the chamber. According to Fig. 49(2), it is shown that the cooling performance is inferior compared to Fig. 46(1) with cooling.

[0143] 8. Regarding the predetermined distance (ds) between the throat portion of the nozzle and the cooling channel, and the effective width (hw) of the cooling channel The relationship between the predetermined distance (ds) between the throat portion of the nozzle and the cooling channel and the diameter of the throat portion, and the relationship between the effective width (hw) of the cooling channel and the total length of the nozzle will be described with reference to Figs. 50 and 51. Fig. 50 is a diagram showing the positional relationship between the cooling channel and the throat portion and the effective width (hw) with respect to the total length (in the case where the second member is cylindrical).

[0144] Fig. 51 is a diagram showing the positional relationship between the cooling channel and the throat portion and the effective width with respect to the total length (in the case where the second member is tapered). In Fig. 51, although a tapered shape with a wide inlet and a narrow outlet is illustrated, since the pattern with a narrow inlet and a wide outlet is the same, the figure is omitted. As shown in Figs. 51 and 52, in order to obtain the cooling performance of the present invention, the predetermined distance (ds) between the cooling channel and the throat portion 290 is desirably 2 to 3 times the diameter (nsd) of the throat portion based on the diameter (nsd) of the throat portion.

[0145] Also, the effective width (hw) of the helical cooling channel is desirably 1 / 3 to 1 / 2 of the total length (nL) of the second member (nozzle) based on the total length (nL) of the second member. The reason for using the diameter (nsd) of the throat portion and the total length (nL) of the second member (nozzle) as a reference is that it is an important parameter that determines the temperature of the combustion mass and the velocity of the combustion gas in terms of how much the diameter of the throat portion is narrowed with respect to the total length of the nozzle.

[0146] 9. Parentheses As described above, in the configuration of the present invention, first, a helical cooling channel is provided; second, the distance between the cooling channel and the nozzle portion is provided; third, the effective width of the cooling channel is adjusted to an appropriate range; fourth, a helical cooling channel is provided for each channel; fifth, the number of helical cooling channels is optimized; sixth, the thermal conductivity of the material around the nozzle is adjusted to an appropriate range; seventh, the position of the orifice is optimized to stably use nitrous oxide in the cooling channel. With these considerations and contrivances, according to the present invention, even when nitrous oxide is used as an oxidizer in a hybrid rocket engine, it is possible to provide a cooling system with high safety without explosive phenomena. Further, according to the present invention, it is possible to suppress erosion of the nozzle while achieving a balance between cooling performance and temperature rise of the coolant.

Industrial Applicability

[0147] The nozzle cooling device and the regenerative cooling system of the present invention can also be used as a nozzle cooling device or a cooling system for liquid fuel rockets and solid fuel rockets other than hybrid rocket engines.

Explanation of Reference Numerals

[0148] 100 First member 101 Body portion of the first member 102 Flange portion of the first member 104 Rear opening 105 Front opening 110 Inlet (or outlet) of coolant 120 Introduction zone (or recovery zone) for introducing coolant into the cooling channel 130 Helical groove portion 131 Inlet of the cooling channel of CH1 132 Inlet of the cooling channel of CH2 133 CH3 cooling channel entrance 135 Helical cooling channel 140 Helical convex part (fin) 150 Recovery zone (or introduction zone) for recovering coolant from the cooling channel 160 Inner peripheral surface of first member 170 Outlet (or Inlet) 180 flange 200 Second member 260 Outer surface of second member 280 Nozzle part 282 Nozzle inlet 284 Nozzle outlet 290 throat 300 Nozzle cooling device formed by fitting a first member and a second member 400 Hybrid rocket engine body 410 injector 420 Ignition system 430 Solid fuel 440 Combustion Chamber 450 Oxidant inlet 500 Coolant (and oxidizer) tank 510 Phase change orifice 520 Cooling channel piping section 530 Oxidant piping section <Parameters of the first member> Length of the first member's body (L1) Thickness of the flange of the first part (D2) Total length of first member (L1+D2) Diameter of the first member's body (D1Dd) Diameter of the coolant inlet of the first component (C1) Diameter of the coolant outlet of the first component (C2) Diameter of the inner surface of the first member (D1Nd) Thickness of the body part of the first member (D1) Diameter of rear opening of first member (D1Kd) Thickness (D2) of the rear opening of the first member Width (K1) of the introduction zone Width (K2) of the recovery zone <Parameters of the second member Total length (nL) of the second member Diameter (nid) of the inlet of the nozzle Distance (dsl) from the inlet of the nozzle to the throat portion Diameter (nod) of the outlet of the nozzle Diameter (D2Gd) of the second member Diameter (nsd) of the throat portion Distance (D2ds) from the outer peripheral surface of the second member to the throat portion <Parameters of the cooling channel Width (wf) of the fin Width (wch) of the cooling channel Depth (chd) of the cooling channel <Parameters in the state where the first member and the second member are combined Predetermined distance (ds) from the cooling channel to the throat portion (Basically, D2ds ≒ ds) Effective width (hw) of the helical cooling channel

Claims

1. A cooling device having a coolant inlet and a coolant outlet for cooling a nozzle of a rocket engine, a member having a cylindrical or tapered shape on the inner peripheral surface thereof, a first member provided with helical grooves for each of channels with a channel number I (I = 1 to n, where n is an integer of 1 or more) on a part or all of the inner peripheral surface of the member, a member having a cylindrical or tapered outer shape, the shape of the outer peripheral surface of the member being substantially the same as the shape of the inner peripheral surface of the first member, when the member is fitted to the inner peripheral surface of the first member, having a shape such that the outer peripheral surface of the member becomes substantially flush with the inner peripheral surface of the first member, having a nozzle-shaped cavity for forming a nozzle portion of a rocket engine inside the member, a second member having a predetermined distance (ds) secured between the throat portion of the nozzle portion of the member and the outer peripheral surface of the member, means for forming a helical cooling channel between the inner peripheral surface of the first member and the outer peripheral surface of the second member by combining the first member and the second member, the helical grooves provided on the inner peripheral surface of the first member, forming a hole corresponding to the shape of the helical groove between the helical groove and the outer peripheral surface of the second member to form the helical cooling channel, and since the helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, means for preventing the coolant flowing through the helical cooling channel from being excessively heated when the combustion gas of the rocket engine passes through the nozzle portion and for exhibiting a predetermined cooling function, A cooling device for a rocket engine nozzle, characterized by the above.

2. In the cooling device for a rocket engine nozzle according to Claim 1, in the first member, a part of the inner peripheral surface of the first member, at a position corresponding to the throat portion of the nozzle portion, the helical groove is provided, when the helical cooling channel is formed by forming a hole corresponding to the shape of the helical groove between the helical groove and the outer peripheral surface of the second member, in addition to forming the helical cooling channel at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, making the effective width (hw) of the helical cooling channel shorter than the total length of the nozzle portion, A cooling device for a rocket engine nozzle, characterized by **Claim 3** In the cooling device for a rocket engine nozzle according to Claim 2, By using a predetermined heat-conductive material containing graphite as the material of the second member, When the combustion gas of the rocket engine passes through the nozzle portion, the heat received by the nozzle portion of the second member is transmitted through the predetermined heat-conductive material to the coolant flowing through the helical cooling channel, The heat exchange function of the coolant exerts a predetermined cooling function on the nozzle portion, and The helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, By using the predetermined heat-conductive material, it has a function of gradually decreasing the temperature according to the distance from the nozzle portion which is the heat source, When the combustion gas of the rocket engine passes through the nozzle portion, preventing the coolant flowing through the helical cooling channel from being excessively heated, A cooling device for a rocket engine nozzle, characterized by **Claim 4** In the cooling device for a rocket engine nozzle according to any one of Claims 2 or 3, When nitrous oxide is used as the coolant flowing through the helical cooling channel, In order to prevent the phenomenon that the nitrous oxide as the coolant is rapidly heated by the combustion gas of the rocket engine and an explosive phenomenon occurs, and the helical cooling channel or the nozzle portion is destroyed, In addition to forming the helical cooling channel at a position having a predetermined distance ds from the throat portion of the nozzle portion formed inside the second member, Making the effective length of the helical cooling channel shorter than the total length of the nozzle portion, A cooling device for a rocket engine nozzle, characterized by **Claim 5** In the cooling device for a rocket engine nozzle according to any one of Claims 2 or 3, A predetermined distance (ds) provided between the helical cooling channel and the throat portion of the nozzle portion is not less than twice the diameter (nsd) of the throat portion of the nozzle portion, and The effective width (hw) of the helical cooling channel is 1 / 3 to 1 / 2 of the total length (nzl) of the second member, A cooling device for a rocket engine nozzle, characterized by **Claim 6** In the cooling device for a rocket engine nozzle according to any one of Claims 2 or 3, In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member. When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member. The turning angle α of the helical groove portion is 2 to 10 degrees. A cooling device for a rocket engine nozzle, characterized in that.

7. In the cooling device for a rocket engine nozzle according to any one of Claims 2 or 3. In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member. When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member. The number of channels I of the helical groove portion is 2 to 8. A cooling device for a rocket engine nozzle, characterized in that.

8. In the cooling device for a rocket engine nozzle according to Claim 7. In the first member, on a part of the inner peripheral surface of the first member. While providing an introduction zone for introducing a coolant to the cooling channel, By providing a recovery zone for recovering the coolant whose temperature has risen after passing through the cooling channel, Even when the number of channels I of the cooling channel is as small as 2 to 8, the introduction and recovery of the coolant to the cooling channel are performed smoothly. A cooling device for a rocket engine nozzle, characterized in that.

9. A regenerative cooling system for regeneratively cooling a nozzle portion of a hybrid rocket engine, comprising a liquid-phase oxidizer, an oxidizer storage portion for storing the liquid-phase oxidizer, an oxidizer injection portion for injecting the oxidizer, a solid fuel portion serving as a propellant of the rocket, an ignition portion for causing a combustion reaction between the oxidizer and the solid fuel, a nozzle portion for accelerating the combustion gas generated by the combustion of the solid fuel to supersonic speed, and a cooling channel for using the oxidizer for cooling the nozzle portion. As a member for regenerative cooling. A member having a cylindrical or tapered shape on the inner peripheral surface of the member. A first member provided with helical groove portions for each of channels having a channel number I (I = 1 to n, where n is an integer of 1 or more) on a part or all of the inner peripheral surface of the member. As a member including the nozzle portion to be regeneratively cooled. a member having a cylindrical or tapered outer shape, wherein the shape of the outer peripheral surface of the member is substantially the same as the shape of the inner peripheral surface of the first member, and when the member is fitted to the inner peripheral surface of the first member, the outer peripheral surface of the member has a shape such that it is substantially flush with the inner peripheral surface of the first member, a nozzle-shaped cavity for forming a nozzle portion of a rocket engine is provided inside the member, a second member having a predetermined distance (ds) secured between the throat portion of the nozzle portion of the member and the outer peripheral surface of the member, means for forming a helical cooling channel between the inner peripheral surface of the first member and the outer peripheral surface of the second member by combining the first member and the second member, a helical groove provided on the inner peripheral surface of the first member, by forming a hole corresponding to the shape of the helical groove between the outer peripheral surface of the second member and the helical groove, the helical cooling channel is formed, and since the helical cooling channel is formed at a position spaced a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, means for preventing the coolant flowing through the helical cooling channel from being overheated when the combustion gas of the rocket engine passes through the nozzle portion and for exhibiting a predetermined cooling function, a pipe portion for the cooling channel for guiding the oxidizer from the oxidizer storage portion to the cooling channel and functioning as an oxidizer, and a pipe portion for the oxidizer for refluxing the oxidizer that has passed through the cooling channel to the oxidizer injection portion and functioning as an oxidizer, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

10. In the regenerative cooling system for a hybrid rocket engine according to claim 9, in the first member, a part of the inner peripheral surface of the first member, a helical groove is provided at a position corresponding to the throat portion of the nozzle portion, when the helical cooling channel is formed by forming a hole corresponding to the shape of the helical groove between the helical groove and the outer peripheral surface of the second member, in addition to forming the helical cooling channel at a position spaced a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, making the effective width (hw) of the helical cooling channel shorter than the total length of the nozzle portion, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

11. In the regenerative cooling system for a hybrid rocket engine according to claim 10, by using a predetermined heat conductive material containing graphite as the material of the second member, when the combustion gas of the rocket engine passes through the nozzle portion, the heat received by the nozzle portion of the second member is transmitted through the predetermined heat conductive material to the coolant flowing through the helical cooling channel, the heat exchange function of the coolant is used to exert a predetermined cooling function on the nozzle portion, and the helical cooling channel is formed at a position having a predetermined distance (ds) from the throat portion of the nozzle portion formed inside the second member, by using the predetermined heat conductive material, a function of gradually reducing the temperature according to the distance from the nozzle portion as the heat source is provided, preventing the coolant flowing through the helical cooling channel from being excessively heated when the combustion gas of the rocket engine passes through the nozzle portion, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

12. In the regenerative cooling system for a hybrid rocket engine according to claim 10, when nitrous oxide is used as the coolant flowing through the helical cooling channel, in order to prevent the phenomenon that the nitrous oxide as the coolant is rapidly heated by the combustion gas of the rocket engine and an explosive phenomenon occurs, and the helical cooling channel or the nozzle portion is destroyed, in addition to forming the helical cooling channel at a position having a predetermined distance ds from the nozzle portion formed inside the second member, making the effective length of the helical cooling channel shorter than the total length of the nozzle portion, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

13. In the regenerative cooling system for a hybrid rocket engine according to claim 10, a predetermined distance (ds) provided between the helical cooling channel and the throat portion of the nozzle portion is twice or more the diameter nzd of the second member, and the effective width (hw) of the helical cooling channel is 1 / 3 to 1 / 2 of the diameter (nsd) of the throat portion of the nozzle portion, A regenerative cooling system for a hybrid rocket engine, characterized by the above.

14. In the regenerative cooling system for a hybrid rocket engine according to claim 10, In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member. When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member. The turning angle α of the helical groove portion is 2 to 10 degrees. A regenerative cooling system for a hybrid rocket engine, characterized in that.

15. In the regenerative cooling system for a hybrid rocket engine according to claim 10. In the first member, a helical groove portion is provided at a position corresponding to the throat portion of the nozzle portion, which is a part of the inner peripheral surface of the first member. When forming the helical cooling channel by forming a hole portion corresponding to the shape of the helical groove portion between the helical groove portion and the outer peripheral surface of the second member. The number of channels of the helical groove portion is 2 to 8. A regenerative cooling system for a hybrid rocket engine, characterized in that.

16. In the regenerative cooling system for a hybrid rocket engine according to claim 15. In the first member, on a part of the inner peripheral surface of the first member. An introduction zone for introducing a coolant into the cooling channel is provided, and By providing a recovery zone for recovering the coolant whose temperature has risen after passing through the cooling channel. Even when the number of channels I of the cooling channel is as small as 2 to 8, the introduction and recovery of the coolant into the cooling channel are smoothly performed. A regenerative cooling system for a hybrid rocket engine, characterized in that.

17. In the regenerative cooling system for a hybrid rocket engine according to claims 9 to 16. A phase change orifice is arranged in the piping portion for the cooling channel from the oxidizer storage portion to the cooling channel, and the oxidizer stored in the oxidizer storage portion in a liquid phase state is changed to a gaseous state and then delivered to the helical cooling channel. A regenerative cooling system for a hybrid rocket engine, characterized in that.

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