A rocket engine nozzle with a semi-extended nozzle and a method of designing the same

Abstract

The present application relates to a rocket engine nozzle, in particular to a rocket engine nozzle with a semi-extended nozzle and a design method thereof, which solves the technical problem that the use of an axisymmetric nozzle with a fixed area ratio will cause additional performance loss in the under-expanded state, and the use of a large area ratio nozzle will cause structural interference, thereby limiting the improvement of the comprehensive performance of the rocket. The present application is based on the original parallel nozzle, and the outer nozzle is designed to be semi-extended, thereby achieving the purpose of increasing the area ratio of the outer nozzle and improving the comprehensive performance of the rocket, increasing the effective wind area of the rocket, providing additional lateral moment when the engine swings, being more conducive to the flight control of the rocket, and having the advantages of simple structure, no actuator, high reliability and the like. The profile of the semi-extended nozzle is designed by using the characteristic line method, and the wall cooling scheme adopts the combination of ablation cooling and radiation cooling, which has high compatibility with the traditional bell-shaped nozzle technology and is more realizable.

Description

Technical Field

[0001] This invention relates to rocket engine nozzles, and more specifically to a rocket engine nozzle with a semi-extended nozzle and its design method. Background Technology

[0002] As a key component of rocket engines, the nozzle bears the crucial responsibility of ejecting exhaust gases to generate thrust. The nozzle's specific impulse determines the engine's economy, thus significantly impacting the rocket's payload capacity. Current rocket engines commonly use axisymmetric nozzles with a fixed area ratio, which have only one design state. The nozzle is in its optimal performance state when the exit pressure equals the ambient atmospheric pressure. However, the ambient pressure varies considerably during rocket flight, making it impossible for the nozzle to always be at or near its optimal design state. This results in additional performance losses, limiting the improvement of rocket payload capacity. Height-compensating nozzles, such as double-bell nozzles and slotted nozzles, have multiple design states, allowing the effective exit pressure to more closely approximate ambient pressure during flight, thereby improving the rocket engine's overall performance across the entire flight profile. However, these height-compensating nozzles typically have a large area ratio, making them prone to structural interference problems.

[0003] For current booster rockets, to achieve maximum takeoff thrust, the nozzle area ratio is limited to a level that ensures the exit pressure is close to the atmospheric pressure at sea level. As the rocket flies, the mismatch between environmental pressure and nozzle exit pressure increases, leading to greater performance losses due to nozzle underexpansion. For single-nozzle booster rockets, height-compensating nozzles such as double-bell nozzles or slotted nozzles can largely compensate for these performance losses during flight. However, for parallel multi-nozzle booster rockets, the increased area ratio of complete double-bell nozzles or slotted nozzles introduces structural interference problems, limiting performance improvements throughout flight. Furthermore, when multi-nozzle rocket engines like the RD-180 and RD-170 are used in second-stage rockets, a higher nozzle area ratio is needed to achieve higher specific impulse, but large area ratio nozzles also suffer from structural interference. Therefore, it is necessary to increase the nozzle area ratio while avoiding structural interference to improve the overall performance of multi-nozzle rockets in the flight profile. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem that axisymmetric nozzles with a fixed area ratio will cause additional performance loss in the underexpansion state, while nozzles with a large area ratio will cause structural interference, thus limiting the improvement of the overall performance of rockets. The invention provides a rocket engine nozzle with a semi-extended nozzle and its design method.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A rocket engine nozzle with a semi-extended nozzle, characterized in that it includes a semi-extended nozzle and N basic nozzles connected in parallel, where N is an integer greater than or equal to 2.

[0007] Definition: Among N parallel basic nozzles, the basic nozzle located on the outer side is called the outer nozzle;

[0008] The number of outer nozzles is M, where M is an integer greater than or equal to 2 and M≤N;

[0009] Each of the M outer nozzles has a semi-extended nozzle at its outlet end, and each semi-extended nozzle is located in the circumferential position near the outer side of the outlet end of its respective outer nozzle.

[0010] The profile of the semi-extended nozzle is the circumferentially cut profile of the fully extended nozzle at the outlet end of the outer nozzle.

[0011] The fully extended nozzle is a reverse pressure gradient nozzle designed using the method of characteristics, and the exit section of each fully extended nozzle intersects the exit section of its adjacent fully extended nozzles in pairs.

[0012] The circumferential cutting surface is the outer circumferential cutting surface corresponding to the inner angle of the intersection of the exit section;

[0013] The intersecting interior angle of the exit sections refers to the angle formed by the two intersecting lines of one of the fully extended nozzle exit sections and the adjacent fully extended nozzle exit section.

[0014] The area of ​​the exit cross-section of the N basic nozzles is the effective expansion area of ​​the rocket engine under sea-level operating conditions; the total area of ​​the exit cross-sections of the N basic nozzles and the M semi-extended nozzles is the effective expansion area of ​​the engine under high-altitude conditions; the connection point between the M basic nozzles and the M semi-extended nozzles is the profile inflection point at the location of the separation point under sea-level conditions.

[0015] Furthermore, the N basic nozzles include one central nozzle and M outer nozzles, where M = N - 1;

[0016] The central nozzle is located at the center of the N basic nozzles, and the M outer nozzles are located outside the central nozzle.

[0017] Furthermore, N=7 and M=6.

[0018] Furthermore, all N basic nozzles are single bell-shaped nozzles.

[0019] Furthermore, the walls of the M semi-extended nozzles are made of high-temperature alloys or composite materials, and their inner walls are provided with an ablation coating.

[0020] Furthermore, the pressure rise of the M semi-extended nozzles is 5 kPa to 10 kPa.

[0021] Furthermore, the length of each of the M semi-extended nozzles is 70% to 80% of the length of the corresponding 15° conical nozzle.

[0022] A design method for a rocket engine nozzle with a semi-extended nozzle, used to design the aforementioned rocket engine nozzle with a semi-extended nozzle, is characterized by including the following steps:

[0023] Step 1: Design N parallel basic nozzles according to preset requirements, with equal gaps between the N parallel basic nozzles according to preset requirements;

[0024] Step 2: Using the method of characteristics, design the profile of the M outer nozzles among the N basic nozzles with reverse pressure gradient to obtain M fully extended nozzles; the exit section of each fully extended nozzle 6 intersects the exit section of its adjacent fully extended nozzle 6 in pairs.

[0025] Step 3: Cut along the intersection line of the exit section of the fully extended nozzle. The outer circumferential cutting surface corresponding to the inner angle of the intersection of the exit section of the fully extended nozzle is the surface of the semi-extended nozzle, thus obtaining M semi-extended nozzles.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] 1. The present invention provides a rocket engine nozzle with a semi-extended nozzle, which, based on the original parallel nozzle, has an additional semi-extended design on the outer nozzle, thereby increasing the area ratio of the outer nozzle, improving the overall performance of the rocket, reducing the loss of gas performance caused by nozzle underexpansion, increasing the effective frontal area of ​​the rocket, providing additional lateral torque when the engine oscillates, which is more conducive to rocket flight control, and has a simple structure and high reliability.

[0028] 2. The present invention provides a rocket engine nozzle with a semi-extended nozzle. The profile of the semi-extended nozzle is designed using the characteristic line method, and the wall cooling scheme combines ablation cooling and radiation cooling. It has high compatibility with traditional bell-shaped nozzle technology and is more feasible. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of a rocket engine nozzle with a semi-extended nozzle proposed in this invention.

[0030] Figure 2 This is a schematic diagram of the bottom structure of a rocket engine nozzle with a semi-extended nozzle proposed in this invention.

[0031] Figure 3 This is a schematic diagram of the semi-extended nozzle structure design of a rocket engine nozzle with a semi-extended nozzle proposed in this invention.

[0032] Figure 4 This is a schematic diagram of the semi-extended nozzle structure of a rocket engine nozzle with a semi-extended nozzle proposed in this invention.

[0033] Figure 5 Mach number cloud diagram of the center section of the exhaust flow field of a rocket engine nozzle with a semi-extended nozzle proposed in this invention under sea level conditions.

[0034] Figure 6 Mach number cloud diagram of the center section of the exhaust flow field of a rocket engine nozzle with a semi-extended nozzle under vacuum conditions, as proposed in this invention.

[0035] Figure 7 This is a comparative curve of the overall performance of the basic nozzle used in this invention and a rocket engine nozzle with a semi-extended nozzle proposed in this invention.

[0036] The annotations in the attached figures are explained as follows:

[0037] 1-Basic nozzle, 2-Semi-extended nozzle, 3-Outer nozzle, 4-Center nozzle, 5-Surface transition point, 6-Fully extended nozzle, 7-Exit section of fully extended nozzle, 8-Intersecting interior angle of exit sections. Detailed Implementation

[0038] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of a rocket engine nozzle with a semi-extended nozzle and its design method, as proposed in this invention. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this invention and are not intended to limit the scope of protection of this invention.

[0039] A rocket engine nozzle with a semi-extended nozzle includes a semi-extended nozzle 2 and N basic nozzles 1 connected in parallel, where N is an integer greater than or equal to 2. The outermost basic nozzle 1 among the N parallel basic nozzles 1 is defined as the outer nozzle 3, and the number of outer nozzles 3 is M, where M is an integer greater than or equal to 2, and M ≤ N. Each of the M outer nozzles 3 has a semi-extended nozzle 2 at its exit end, and each semi-extended nozzle 2 is located circumferentially near the outer side of the exit end of its corresponding outer nozzle 3.

[0040] The profile of the semi-extended nozzle 2 is the circumferentially cut profile of the fully extended nozzle 6 at the exit end of the outer nozzle 3. The fully extended nozzle 6 is a reverse pressure gradient nozzle designed using the method of characteristics, and the exit section of each fully extended nozzle 6 intersects the exit sections of its adjacent fully extended nozzle 6 pairwise. The circumferentially cut profile is the outer circumferentially cut profile corresponding to the interior angle 8 of the exit section intersection. The interior angle 8 of the exit section intersection refers to the angle formed by the two intersecting lines of the exit section of one of the fully extended nozzles 6 and the exit section of its adjacent fully extended nozzle 6. The exit sections of the M semi-extended nozzles 2 do not intersect.

[0041] like Figure 1 , Figure 2 As shown, in a rocket engine, there are usually more than three basic nozzles 1, which can be divided into outer nozzles 3 and a central nozzle 4. All basic nozzles 1 are traditional single bell-shaped nozzles. N basic nozzles 1 include one central nozzle 4 and M outer nozzles 3, where M = N-1. The central nozzle 4 is located at the center of the N basic nozzles 1, and the M outer nozzles 3 are located outside the central nozzle 4.

[0042] The semi-extended nozzle 2 is an additional bend and extension of the profile based on the outer nozzle 3. The area of ​​the exit cross-section of the N basic nozzles 1 is the effective expansion area of ​​the rocket engine under sea-level operating conditions. The total area of ​​the exit cross-sections of the N basic nozzles 1 and the M semi-extended nozzles 2 is the effective expansion area of ​​the engine under high-altitude conditions. The connection point between the M basic nozzles 1 and the M semi-extended nozzles 2 is the profile bend point 5 at the location of the separation point under sea-level conditions.

[0043] The wall cooling method of the semi-extended nozzle 2 is a combination of ablation cooling and radiation cooling. That is, the wall of the semi-extended nozzle 2 is made of high-temperature alloy or composite material, and the inner wall is coated with ablation material to achieve the purpose of thermal protection of the nozzle structure.

[0044] The design principle of the semi-extended nozzle 2 is as follows: using the characteristic line method, the outer nozzle 3 of the base nozzle 1 is designed with a reverse pressure gradient for the full extension nozzle 6, with the pressure rise value in the range of 5kPa to 10kPa, and then the entire full extension nozzle 6 is trimmed.

[0045] This embodiment also provides a design method for a rocket engine nozzle with a semi-extended nozzle, used to design the aforementioned rocket engine nozzle with a semi-extended nozzle, including the following steps:

[0046] Step 1: Design N parallel basic nozzles 1 according to the preset requirements, and leave equal gaps between the N parallel basic nozzles 1 according to the preset requirements.

[0047] Step 2: Use the method of characteristics to design the profile of the M outer nozzles 3 with reverse pressure gradient to obtain M fully extended nozzles 6; the exit section of each fully extended nozzle 6 intersects the exit section of its adjacent fully extended nozzle 6 in pairs.

[0048] Step 3: Cut along the intersection line of the exit section of the full extension nozzle 6. The outer circumferential cutting surface corresponding to the inner angle 8 of the exit section of the full extension nozzle 6 is the surface of the semi-extension nozzle 2, thus obtaining M semi-extension nozzles 2.

[0049] like Figure 3 As shown, in this embodiment, the geometric parameters of the semi-extended nozzle 2 are selected based on the following principle: ensuring that the area of ​​the uncut fully extended nozzle 6 is large enough to allow intersection of the exit sections 7 of the fully extended nozzle, and designing the length of the uncut fully extended nozzle 6 to be 70% to 80% of the length of the corresponding 15° conical nozzle. Then, the profile of the fully extended nozzle 6 is trimmed within the range of the intersecting interior angle 8 of the exit sections, ensuring that after trimming, the exit sections of the remaining semi-extended nozzle 2 profile do not intersect. The structure of the outer nozzle 3 after the semi-extended design is as follows: Figure 4 As shown.

[0050] For multi-nozzle rockets, only the outermost nozzle 3 has a semi-extended outer profile; the inner profile of the outer nozzle 3 and the center nozzle 4 are not extended. The semi-extended design of the outer nozzle 3 is not limited to launch vehicles with a fixed number of nozzles; launch vehicles with at least two nozzles connected in parallel can also have a semi-extended outer profile of the outer nozzle 3.

[0051] The semi-extended nozzle 2 increases the area ratio of airflow expansion without altering the original rocket structure. When the rocket flies at low altitudes, only the parallel basic nozzle 1 is fully flown, while the outer semi-extended nozzle is in a symmetrically separated state, effectively suppressing lateral loads. When the rocket flies at high altitudes, both the basic nozzle 1 and the semi-extended nozzle 2 are fully flown, effectively improving engine performance. The rocket engine nozzle with a semi-extended nozzle provided by this invention can effectively improve the engine's overall performance throughout flight, while also providing additional control torque to the rocket during engine swaying. It also boasts advantages such as simple structure, high compatibility with traditional nozzle technologies, and strong scalability and applicability. Compared to height-compensating nozzles with variable geometry, the fixed-geometry semi-extended nozzle offers advantages such as simple structure, no actuation mechanism, and high reliability.

[0052] Figure 5 , Figure 6The figures show Mach number cloud diagrams of the central cross-section of the exhaust flow field of a multi-nozzle launch vehicle with a semi-extended outer nozzle, under sea level and vacuum conditions, respectively. As can be seen from the figures, the rocket engine nozzle with a semi-extended nozzle proposed in this invention can achieve symmetrical control of the separated flow under sea level conditions and increase the expansion degree of the combustion gases under vacuum conditions. Figure 7 The graph shows a comparison of the overall performance of the basic nozzle used in this invention with that of a rocket engine nozzle with a semi-extended nozzle proposed in this invention. As can be seen from the graph, the overall performance of the rocket engine is significantly improved after the outer nozzle is semi-extended, indicating that the solution disclosed in this invention is feasible.

Claims

1. A rocket engine nozzle with a semi-extended nozzle, characterized in that: It includes a semi-extended nozzle (2) and N basic nozzles (1) connected in parallel, where N is an integer greater than or equal to 2; Define the outermost basic nozzle (1) among N parallel basic nozzles (1) as the outer nozzle (3); The number of the outer nozzles (3) is M, where M is an integer greater than or equal to 2 and M≤N; Each of the M outer nozzles (3) has a semi-extended nozzle (2) at its outlet end. Each semi-extended nozzle (2) is located in the circumferential position near the outer side of the outlet end of the outer nozzle (3). The profile of the semi-extended nozzle (2) is the circumferentially cut profile of the fully extended nozzle (6) at the outlet end of the outer nozzle (3). The fully extended nozzle (6) is a reverse pressure gradient nozzle designed using the method of characteristics, and the exit section of each fully extended nozzle (6) intersects with the exit section of its adjacent fully extended nozzle (6) in pairs. The circumferential cutting surface is the outer circumferential cutting surface corresponding to the inner angle (8) of the intersection of the exit sections; The intersecting interior angle (8) of the exit sections refers to the angle formed by the two intersecting lines of the exit section of one of the fully extended nozzles (6) and the exit section of the adjacent fully extended nozzle (6).

2. A rocket engine nozzle with a semi-extended nozzle according to claim 1, characterized in that: The N basic nozzles (1) include a central nozzle (4) and M outer nozzles (3), where M = N-1; The central nozzle (4) is located at the center of N basic nozzles (1), and the M outer nozzles (3) are located outside the central nozzle (4).

3. A rocket engine nozzle with a semi-extended nozzle according to claim 2, characterized in that: The N=7 and M=6.

4. A rocket engine nozzle with a semi-extended nozzle according to any one of claims 1-3, characterized in that: All N basic nozzles (1) are single bell-shaped nozzles.

5. A rocket engine nozzle with a semi-extended nozzle according to claim 4, characterized in that: The walls of the M semi-extended nozzles (2) are made of high-temperature alloy or composite material, and their inner walls are provided with an ablation coating.

6. A rocket engine nozzle with a semi-extended nozzle according to claim 5, characterized in that: The pressure rise of each of the M semi-extended nozzles (2) is 5 kPa to 10 kPa.

7. A rocket engine nozzle with a semi-extended nozzle according to claim 6, characterized in that: The length of each of the M semi-extended nozzles (2) is 70% to 80% of the length of the corresponding 15° conical nozzle.

8. A design method for a rocket engine nozzle with a semi-extended nozzle, used to design a rocket engine nozzle with a semi-extended nozzle as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Design N parallel basic nozzles (1) according to the preset requirements, and leave equal gaps between the N parallel basic nozzles (1) according to the preset requirements; Step 2: The characteristic line method is used to design the profile of the M outer nozzles (3) with reverse pressure gradient to obtain M fully extended nozzles (6); the exit section of each of the fully extended nozzles (6) intersects the exit section of its adjacent fully extended nozzles (6) in pairs. Step 3: Cut along the intersection line of the exit section of the full extension nozzle (6). The outer circumferential cutting surface corresponding to the inner angle (8) of the exit section of the full extension nozzle (6) is the surface of the semi-extension nozzle (2), and M semi-extension nozzles (2) are obtained.

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