Hybrid rocket injector to increase fuel regression rate and combustion stability

Abstract

The invention relates to a hybrid fuel rocket engine (1) having at least one casing (10), at least one solid fuel compartment (11) on a side facing the internal cavity (12) of said casing (10), at least one manifold (20) to supply a liquid oxidizer to said internal cavity (12), and at least one nozzle (30) to at least partially limit the discharge of the burning liquid oxidizer from the internal cavity (12). The novelty of the invention is characterized in that said oxidizer manifold (20) comprises at least one tube injector (21) extending at least partially along the internal cavity (12) to supply a liquid into the internal cavity (12) and at least one injector hole (22) on a lateral surface of said tube injector (21) to supply the liquid oxidizer. The fuel regression rates could be increased to a record level and a high engine combustion stability was also achieved, due to the internal ballistics of that rocket engine (1). In this way, the field of use of hybrid rocket engines (1) have been expanded, and they have become an alternative to solid fuel engines.

Description

[0001] HYBRID ROCKET INJECTOR TO INCREASE FUEL REGRESSION RATE AND COMBUSTION STABILITY

[0002] TECHNICAL FIELD

[0003] The invention relates to a hybrid fuel rocket engine having at least one solid fuel compartment on a side facing the internal cavity of said casing, at least one manifold to supply a liquid oxidizer to said internal cavity, and at least one nozzle to at least partially limit the discharge of the products formed as a result of the combustion from the internal cavity.

[0004] PRIOR ART

[0005] Chemical rockets are generally systems which generate high-enthalpy gases as a result of the combustion reaction of fuel and an oxidizer and generate propellant power through these gases. Chemical propulsion rocket engines are divided into three subgroups according to the physical phase of the fuel and oxidizer used:

[0006] - Solid Fuel Rocket Engines: the fuel and oxidizer are kept in the engine combustion chamber in a solid phase. Low specific impact performance and high propulsion intensity are its general characteristics. These engines are preferred especially in military systems due to their relatively simple design and ease of use. These systems have high explosive conjugates. Therefore, it is necessary to work with special precautions in all processes from production to use. This brings with it relative disadvantages in terms of cost and schedule.

[0007] - Liquid Fuel Rocket Engines: the fuel and oxidizer are kept in two separate tank in a liquid phase. The fuel and oxidizer are delivered to the combustion chamber by pressurizing the tanks, or using a pump. Here, the mixed fuel and oxidizer are subjected to a combustion reaction, and the high-enthalpy gases required for propulsion are generated. . These engines have a more complex design architecture than the solid and hybrid fuel rocket engines. High specific impact performance and low propulsion intensity are its general characteristics. They are mostly used in large-scale rocket systems, which are space access vehicles. They are relatively more costly systems than the other chemical propulsion systems.

[0008] Hybrid Rocket Engines: The fuel in the solid phase is kept in the combustion chamber, and the oxidizer in the liquid phase is kept in the tank. The oxidizer is combined with the fuel in the combustion chamber by pressurizing the tank, or using a pump. They have higher specific impact performance than the solid fuel rocket engines. However, hybrid rocket engines have a characteristic of having a lower propulsion intensity than the solid ones. The system architecture of the hybrid rocket engines ensures these propulsion systems to be safer and more economical.

[0009] Apart from the Chemical Propulsion Rockets mentioned above, there are also Electric Rocket Propulsion Systems and Nuclear Rocket Propulsion systems. Hybrid rocket engines may be configured in three different types. These are as follows:

[0010] Hybrids with a conventional configuration: It is a configuration where the oxidizer is kept in the tank in the liquid phase and the fuel is kept in the engine in the solid phase.

[0011] Hybrids with a reverse configuration: It is a configuration where the fuel is kept in the tank in the liquid phase and the oxidizer is kept in the engine in the solid phase.

[0012] Hybrids with a mixed configuration: It is the configuration in which a small amount of the oxidizer in the solid phase is added to the fuel of the hybrid engines the solid phase in the conventional configuration.

[0013] Rocket injectors are one of the main parts of the rocket engines and are often complex parts that require high precision and accuracy. The rocket injector ensures the fuel and / or oxidizer taken from the tank in the liquid phase to be delivered to the combustion chamber at a desired flow rate and in a desired atomization quality. Injectors are considered a critical component that determines the performance and reliability of the rocket engine. Therefore, some technical problems may be encountered during the production, assembly and use of injectors. The technical problems frequently seen in rocket injectors are as follows: Pressure drop: In order for the liquid taken from the tank to be atomized into small particles, the liquid should be forced into a certain flow area in the injector and discharged into the combustion chamber at a certain pressure drop. Pressure drop is an important parameter which should be anticipated in internal ballistic designs.

[0014] - Injector clogging: Injector sprayers are generally designed to have small outlet holes in order to provide the desired atomization quality. . These holes may become clogged or dirty, reducing the efficiency of the injector.

[0015] - Abrasion: Abrasion and wear problems may occur as the injectors should withstand high temperatures and pressures. This may cause a malfunction in the injector, or reduce its performance.

[0016] - Instability: Injectors require a specific flow pattern to mix fuel and oxidizer in a correct ratio. However, in some cases, the flow pattern in the injector may become instable, resulting in the reduced performance of the rocket engine.

[0017] - Dirtiness: Parts operating near the injectors may be subject to fuel or oxidizer leaks. This may cause the injector to become dirty and reduce its performance.

[0018] These problems can be described as general injector problems. These problems are prevented or reduced by careful consideration during the design, production and use of the rocket engine. However, injector problems remain a significant factor for the reliability and performance of the rocket engine.

[0019] However, the slow regression rate of fuel and the resulting combustion instabilities, which have existed since the 1950s and have not been resolved to date, have posed an obstacle to the use of hybrid rocket engines in a practical application. There are dozens of solution suggestions in the literature to solve this problem, and the fuelspecific studies have found solutions that are scalable and provide some improvement. However, the improvements in the fuel regression rate achieved with the fuel-specific solutions were insufficient when compared to the solid fuel rockets. In this context, it can be said that another field of study aimed at increasing the fuel regression rate is for the injector designs. The conventional type injector used in the hybrid rocket engines supplies the oxidizer axially from the head of the engine to the internal fuel cavity. Conventional injection was also used by Marxman, who explained the combustion theory of hybrid rocket engines in the 1960s. Many different types of injector designs were tried between the 1960s and the 2020s to increase the fuel regression rate. When the reasons why no tangible results have been obtained from these studies to date are examined, some common characteristics have been identified. Accordingly:

[0020] • Inability to scale the proposed technology: In the designs which have achieved extremely high fuel regression rates on a laboratory scale, when switched to a large-scale engine (practically real rocket sizes) the mechanism that improves the regression rate in the engine lost its effect and the values obtained on a small scale could not be achieved.

[0021] • Working with a gaseous phase oxidizer: Designs which have been made on a laboratory scale using gaseous phase oxidizers and have achieved extremely high regression rates do not have any meaning as they are not practically used in a real rocket application (for example, a rocket requiring 5 tons of oxygen creates a tank size difference of roughly 10 times between the storage of an oxidizer in the liquid phase and storage of the same in the gaseous phase, which is not acceptable in a real rocket application).

[0022] • Its applicability is very difficult and impractical: Although scalability is technically possible in certain injectors developed, its applicability and healthy operation in the entire engine combustion process are not considered possible. Consequently, all the above-mentioned problems and the inadequacy of the solutions proposed to them have made it necessary to make an innovation in the relevant technical field.

[0023] SUMMARY OF THE INVENTION

[0024] The present invention relates to a rocket injector in order to eliminate the above mentioned disadvantages and provide the related technical field with new advantages.

[0025] An object of the invention is to significantly increase the fuel regression rate in hybrid rockets, regardless of the rocket scale. Another object of the invention is to eliminate the combustion instability problem, which is one of the general problems in hybrid rocket engines, regardless of the rocket scale. In order to achieve all the objects mentioned above and that will be appreciated from the detailed explanation below, the present invention is a hybrid fuel rocket engine having at least one casing, at least one solid fuel compartment on a side facing the internal cavity of said casing, at least one fuel injection head to supply a liquid oxidizer to said internal cavity (combustion chamber), and at least one nozzle to at least partially limit the discharge of the burning liquid fuel from the internal cavity. Unlike conventional, axially injecting injectors, the novelty of this injector is that it includes at least one tube extending at least partially along the internal cavity of the combustion chamber, so as to spray the oxidizer into the combustion chamber in all desired directions (axial, radial and / or tangential), and at least one opening on the lateral surface thereof on said tube for spraying the liquid oxidizer. Thus, the solid fuel in the liquid oxidizer combustion chamber is provided with the ability to be supplied in a radial direction throughout the engine, and as a result, the internal ballistics of the radial engine are completely differentiated from the conventional configuration and ultimately, the fuel regression rate is increased due to the increase in heat transfer to the fuel.

[0026] A possible embodiment of the invention is characterized in that the tube is configured to rotate at least partially around itself and includes at least one drive member with which the tube is associated to rotate it around itself. Thus, near-perfect geometric use of fuel is achieved in the fuel combustion profile by rotating the tube around itself.

[0027] Another possible embodiment of the invention is characterized in that the tube is cylindrical in shape and the tube extends throughout the internal cavity. Thus, the oxidizer flux can be fed uniformly throughout the solid fuel. This ensures homogeneous combustion throughout the fuel.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Fig. 1 shows a representative cross-sectional view of the rocket motor of the invention.

[0030] Fig. 2 shows a representative cross-sectional view of the rocket motor of the invention.

[0031] DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the subject matter of the invention is described with examples only for a better understanding of the subject in a non-limiting sense.

[0032] Fig. 1 shows a representative cross-sectional view of the rocket motor (1 ) of the invention. Accordingly, the hybrid rocket engine (1 ) is a type of chemical rocket based on the combustion reaction occurred by supplying a liquid oxidizer onto the solid fuel to obtain propulsion power. The hybrid rocket engine (1) includes at least one injector (21 ). Said injector (21) is considered a critical component that determines the performance and reliability of the rocket engine (1). The injector (21) of the invention has been developed to be used in the hybrid rocket engines (1).

[0033] The hybrid rocket engine (1) includes at least one casing (10). Said casing (10) is essentially cylindrical in shape and has at least one internal cavity (12) in its center. Said casing (10) is made of a metal-based material and provides strength during combustion. The internal cavity (12) of the casing (10) is, in fact, the joining zone of the solid fuel and oxidizer. There is a solid fuel compartment (11 ) on a wall of the body (10) facing the internal cavity (12). Said solid fuel is essentially a paraffin-based combustion element and is burned in the rocket engine (1 ) to provide propulsion power to the rocket.

[0034] The rocket engine (1) includes at least one fuel injection head on one side of the casing (10). There is at least one rear casing (30) and at least one nozzle (31 ) on the opposite side of the casing (10). Said fuel injection head allows the liquid oxidizer to be supplied. Said nozzle (31 ) is configured to both determine the engine operating pressure and ensure the combustion products to be accelerated and exited from the rocket engine (1). In this way, the required propulsion production is achieved. There is a rear casing (30) part at the rear of the rocket engine (1) so that the nozzle (31 ) can be structurally connected to the engine casing (10).

[0035] The engine manifold (20) is associated with the rocket injector (21) of at least one tube geometry. Said injector (21 ) is associated with the manifold (20) on one side and extends towards the internal cavity (12) of the casing (10) on the other side. The injector (21 ) allows the liquid oxidizer supplied from the manifold (20) to be carried to the inner surface of the solid fuel compartment (11). For this, the injector (21) is preferably cylindrical in shape and comprises at least one injector hole (22). Said injector hole (22) is provided in multiple numbers on the injector (21) wall. In other words, the injector holes (22) are configured to allow injection in the radial direction. In this way, the oxidizer injection is performed perpendicularly to the internal wall (11 ) of the solid fuel. In this way, the combustion reaction takes place by providing the desired flow area in the internal cavity (12) of the engine. The injector holes (22) may be opened in different geometric forms, directions and distributions on the injector (21). This provides the ability to create solutions that can adapt to different needs.

[0036] Fig. 2 shows another representative cross-sectional view of the rocket motor (1 ) of the invention. Accordingly, in a possible embodiment of the invention, the injector (21 ) is configured to be rotated at least partially around itself in order to increase the regression rate in the rocket engine (1). To this end, at least one drive member (23) is located on the manifold (20). Said drive member (23) allows the injector (21) to be rotated around itself. By rotating the injector (21 ) around itself, a tangential velocity component is provided during the joining of the liquid oxidizer and the solid fuel, thus increasing the use of fuel (11 ) by up to 100% at the end of engine ignition. This increases the overall system efficiency.

[0037] The solid fuel (11) used in the rocket injector (1) is paraffin, which is a derivative of petroleum and has a wide industrial use. A paraffin-based solid fuel (11 ) is used in the engine (1) as it burns at 3-4 times faster regression rate than the conventional type polymeric fuels (HTPB, HDPE, etc.) regardless of the injector and also the fuel specific impact performance is higher than the conventional fuels. The liquid oxidizer used in the rocket injector (21) is nitrogen protoxide. This liquid was chosen for use in this system as it has a high vapor pressure at room temperature, is easily available, can be stored, is economical and has relatively high performance.

[0038] The scope of protection of the invention is specified in the attached claims and cannot be limited to what is explained in this detailed description for the exemplary purposes. That is because it is clear that a person skilled in the art may represent similar embodiments in the light of what has been explained above without departing from the main spirit of the invention.

[0039] REFERENCE NUMBERS IN THE DRAWINGS I Rocket Engine

[0040] 10 Casing

[0041] I I Solid Fuel Compartment 12 Inner Cavity

[0042] 20 Manifold

[0043] 21 Injector

[0044] 22 Injector Hole 23 Drive member

[0045] 30 Rear Casing

[0046] 31 Nozzle

Claims

CLAIMS1 . A hybrid fuel rocket engine (1 ) having at least one casing (10), at least one solid fuel compartment (11 ) on a side facing the internal cavity (12) of said casing (10), at least one manifold (20) to supply a liquid oxidizer to said internal cavity (12), and at least one nozzle (30) to at least partially limit the discharge of the burning liquid oxidizer from the internal cavity (12), characterized in that said oxidizer manifold (20) comprises at least one tube injector (21) extending at least partially along the internal cavity (12) to supply a liquid into the internal cavity (12) and at least one injector hole (22) on a lateral surface of said tube injector (21) to supply the liquid oxidizer.

2. A rocket engine (1 ) according to claim 1 , characterized in that the injector (21 ) is configured to rotate at least partially around itself.

3. A rocket engine (1) according to claim 1 , characterized in that it has a structure such that the injector holes (22) may be designed axially, radially and / or tangentially on the injector (21).

4. A rocket engine (1) according to claim 2, characterized in that it has a structure such that the injector holes (22) may be designed axially, radially and / or tangentially on the injector (21).

5. A rocket engine (1) according to claim 2, characterized in that it comprises at least one drive member (23) with which the injector (21 ) is associated to be rotated around itself.

6. A rocket engine (1 ) according to claim 1 , characterized in that the injector (21) is cylindrical.

7. A rocket engine (1 ) according to claim 1 , characterized in that the injector (21 ) extends through the internal cavity (12).

8. A rocket engine (1 ) according to claim 1 , characterized in that it comprises nitrogen protoxide as a liquid oxidizer.

9. A rocket engine (1 ) according to claim 1 , characterized in that it comprises paraffin as fuel.5

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