A rocket engine with variable nozzle exit area

Abstract

The present invention discloses a rocket engine with a variable nozzle outlet area, comprising a combustion chamber, an altitude compensation nozzle, and a pressure monitoring sensor. The altitude compensation nozzle comprises a fixed section nozzle, a telescopic section nozzle, and a telescopic drive device. The telescopic section nozzle comprises N inner blades and N outer blades arranged circumferentially and staggered, the two blades being circumferentially sealed and fitted, and the top ends being connected by a connecting sleeve. The top end of each telescopic drive device is mounted on the upper middle portion of the outer blade, and each can actively extend and retract. The pressure monitoring sensor comprises a nozzle outlet pressure sensor and a back pressure sensor. The present invention can ensure that the engine nozzle outlet area can be continuously changed without changing the flow rate. By continuously changing the nozzle area ratio at each altitude, the outlet pressure is matched with the ambient pressure, thereby achieving a change in the thrust of the engine under different ambient pressures, improving combustion efficiency, reducing fuel waste, saving propellant, and increasing payload capacity.

Description

Technical Field

[0001] The present invention relates to the field of propulsion technology, in particular to a rocket engine with a variable nozzle outlet area. Background Art

[0002] The nozzle is an important component that generates thrust in liquid rocket engines. It can convert the high-temperature gas thermal energy generated by the combustion of propellant in the combustion chamber into pressure potential energy, and then into kinetic energy, to achieve supersonic discharge of gas and generate thrust by the momentum of the gas jet.

[0003] The nozzle is an important energy conversion device in rocket engines. Its performance is directly related to the performance of the entire rocket propulsion system. Improving nozzle performance will enable more efficient energy utilization, improve the rocket's ability to transport payloads into orbit, save propellant, reduce launch costs, and promote the sustainable development of the space industry. s And thrust F are two important parameters that can measure the performance of the engine.

[0004] The actual exhaust velocity of the engine is not completely uniform on the nozzle outlet cross section. For one-dimensional calculation problems, it can be assumed that the nozzle outlet axial velocity c is uniformly distributed. The axial velocity c is also called the effective (or equivalent) exhaust velocity, which is related to the specific impulse I s The relationship is

[0005]

[0006] Where: F is the engine thrust; is the nozzle mass flow rate; v2 is the actual average exhaust velocity of the nozzle, p2 is the nozzle outlet pressure, p3 is the back pressure (atmospheric pressure), and A2 is the nozzle outlet area.

[0007] c and I s The unit is m / s, specific impulse I s It is actually the thrust generated by the unit mass flow rate of the propellant. The larger the specific impulse value, the better its performance. It can be seen from formula (1) that the specific impulse and thrust have a high degree of characteristic, such as Figure 1 The RS-27 engine thrust F and specific impulse I are shown. s The trend of change with altitude, specific impulse I s It gradually increases with the increase of altitude and eventually approaches a constant value. When the nozzle mass flow rate is constant, this trend is caused by the change of total thrust with altitude.

[0008] At present, the rocket engine nozzles used in space launches of various countries almost all use nozzles with fixed geometric shapes. However, due to the change in the altitude of the rocket during flight, the engine nozzle back pressure (i.e. atmospheric pressure) will change significantly. The change trend is as follows: Figure 1As shown in the figure, it is clear that atmospheric pressure drops rapidly with altitude from sea level, approaching 0.001 MPa at around 30 kilometers, which is 1% of the standard atmospheric pressure at sea level. Therefore, the change in total thrust with altitude is closely related to the large changes in atmospheric pressure P3. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and to provide a rocket engine with a variable nozzle outlet area. The rocket engine with a variable nozzle outlet area adjusts the outlet area of ​​the tail end of the telescopic section nozzle by controlling the active telescopic amount of M telescopic drive devices, thereby adjusting the exhaust pressure at the tail end outlet of the telescopic section nozzle, so that the exhaust pressure is equal to the back pressure at the current altitude, thereby realizing height compensation of thrust.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A rocket engine with a variable nozzle outlet area comprises a combustion chamber, an altitude compensation nozzle and a pressure monitoring sensor.

[0012] The height compensation nozzle comprises a fixed section nozzle, a telescopic section nozzle and a telescopic driving device.

[0013] The fixed section nozzle coaxial seal is arranged at the tail end of the combustion chamber.

[0014] The telescopic section nozzle coaxial seal is arranged at the tail end of the fixed section nozzle.

[0015] The telescopic section nozzle comprises an inner layer nozzle and an outer layer nozzle which are coaxially arranged in sequence from the inside to the outside.

[0016] The inner layer nozzle includes N inner layer blades uniformly distributed along the circumference; wherein N ≥ 8; the bottom of each inner layer blade is sealed and connected to the tail end of the fixed section nozzle.

[0017] The outer layer nozzle comprises N outer layer blades uniformly distributed along the circumference; the bottom of each outer layer blade is sealed and connected to the tail end of the fixed section nozzle.

[0018] N outer fan blades and N inner fan blades are arranged circumferentially in an alternating manner, and the inner wall surfaces of the N outer fan blades fit in contact with the outer wall surfaces of the N inner fan blades; the top ends of the N outer fan blades are connected to the top ends of the N inner fan blades through several connecting sleeves.

[0019] The number of telescopic drive devices is M, and M≤N; the M telescopic drive devices are evenly arranged along the circumference of the fixed section nozzle; the fixed end of each telescopic drive device is installed on the fixed section nozzle, and the telescopic end of each telescopic drive device is installed in the middle and upper part of the corresponding outer fan blade, and each telescopic drive device can actively retract and retract.

[0020] The pressure monitoring sensor includes a nozzle outlet pressure sensor and a back pressure sensor; among them, the nozzle outlet pressure sensor can be used to monitor the exhaust pressure P2 at the tail end outlet of the telescopic section nozzle; the back pressure sensor can be used to monitor the atmospheric pressure P3 of the environment in which the rocket engine is located.

[0021] When p2=p3, the effective exhaust velocity c of the altitude compensation nozzle is equal to the actual average exhaust velocity v2 of the propellant gas. At this time, the altitude compensation nozzle can achieve optimal expansion of the gas and thus have the best thrust.

[0022] The atmospheric pressure P3 will change with the altitude of the rocket engine. By controlling the active extension and contraction amount of the M telescopic drive devices, the outlet area of ​​the tail end of the telescopic section nozzle is adjusted, thereby adjusting the exhaust pressure P2 at the tail end outlet of the telescopic section nozzle, so that P2 = P3, and the altitude compensation nozzle always has the optimal thrust, realizing the altitude compensation of the thrust.

[0023] The inner nozzle formed by N inner fan blades is a regular polygon.

[0024] The height compensation nozzle is a tapered tube.

[0025] The taper of the fixed section nozzle is 15°.

[0026] N≥20, 6≤M≤N.

[0027] Each inner fan blade and each outer fan blade includes two V-shaped straight blades; and the V-shaped angle is not less than 160°.

[0028] By controlling the V-shaped angle, the number N of inner blades or outer blades can be adjusted.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention can achieve continuous change of the nozzle outlet area mainly by continuous actuation of the telescopic nozzle without affecting the normal flight of the carrier rocket, can significantly increase the nozzle area ratio, achieve high thrust compensation, and improve engine performance.

[0031] 2. By controlling the active extension and retraction of the M telescopic drive devices and adjusting the outlet area of ​​the telescopic nozzle tail, the present invention can ensure that the exhaust pressure at the telescopic nozzle tail outlet is equal to the back pressure at the current altitude. This allows the effective exhaust velocity c of the altitude compensation nozzle to be equal to the actual average exhaust velocity v2 of the propellant gas. This controllable velocity reduces the difficulty of ground recovery and reduces reuse costs. Furthermore, it effectively prevents damage to the fairing and rocket body caused by overload during fairing recovery, and allows the fairing to be recovered intact, thereby improving fairing recovery reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shows the RS-27 engine thrust F and specific impulse I s Trend graph with altitude.

[0033] Figure 2 A schematic diagram showing the curve of atmospheric pressure P3 changing with the altitude of the rocket engine.

[0034] Figure 3 A schematic structural diagram of a rocket engine with a variable nozzle outlet area according to the present invention is shown.

[0035] Figure 4 A schematic diagram of the structure of the inner fan blade or the outer fan blade in the present invention is shown.

[0036] Figure 5 The cross-sectional shape of the tail end of the telescopic nozzle is shown; (a) is a regular decagon; (b) is a regular icosagon.

[0037] Figure 6 Shown is a schematic structural diagram of the connecting sleeve in the present invention.

[0038] Figure 7 A graph showing the change in altitude of the ideal altitude-compensated nozzle exit area ratio.

[0039] Figure 8 A graph showing the change in nozzle exit area ratio and nozzle exit pressure for the height-compensated nozzle is shown.

[0040] Figure 9 A graph showing the change of thrust coefficient with altitude at different area ratios is shown.

[0041] Figure 10 A graph showing the change of thrust with altitude at different area ratios is shown.

[0042] Among them are:

[0043] 10. Combustion chamber;

[0044] 21. Fixed section nozzle;

[0045] 22. Telescopic nozzle; 221. Outer fan blades; 222. Inner fan blades; 223. Connecting sleeve;

[0046] 23. Telescopic drive device. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific preferred embodiments.

[0048] In the description of the present invention, it should be understood that the terms "left side," "right side," "upper," "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Terms such as "first" and "second" do not indicate the importance of components and therefore should not be construed as limitations on the present invention. The specific dimensions used in this embodiment are intended only to illustrate the technical solution and do not limit the scope of protection of the present invention.

[0049] like Figure 1 As shown, a rocket engine with a variable nozzle outlet area includes a combustion chamber 10, an altitude compensation nozzle and a pressure monitoring sensor.

[0050] The height compensation nozzle includes a fixed section nozzle 21 , a telescopic section nozzle 22 and a telescopic drive device 23 .

[0051] The fixed section nozzle coaxial seal is arranged at the tail end of the combustion chamber, and is preferably a tapered tube with a taper of preferably 15°.

[0052] The telescopic section nozzle coaxial seal is arranged at the tail end of the fixed section nozzle.

[0053] The telescopic section nozzle comprises an inner layer nozzle and an outer layer nozzle which are coaxially arranged from the inside to the outside. The telescopic section nozzle has the same shape as the fixed section nozzle, and is also preferably a tapered tube with a taper of 15 degrees.

[0054] The inner layer nozzle includes N inner layer blades 222 uniformly distributed along the circumference, wherein N is greater than or equal to 8, and further, N is greater than or equal to 20. The bottom of each inner layer blade is sealed to the tail end of the fixed section nozzle.

[0055] The outer layer nozzle comprises N outer layer blades 221 uniformly distributed along the circumference; the bottom of each outer layer blade is sealed and connected to the tail end of the fixed section nozzle.

[0056] N outer fan blades and N inner fan blades are arranged circumferentially in an alternating manner, and the inner wall surfaces of the N outer fan blades fit together with the outer wall surfaces of the N inner fan blades, thereby forming a circumferentially sealed telescopic section nozzle.

[0057] In this embodiment, each inner fan blade and each outer fan blade includes two V-shaped straight blades, as shown in FIG. Figure 4 As shown; and the V-shaped angle is not less than 160°.

[0058] By controlling the V-shaped angle, the number N of inner blades or outer blades can be adjusted.

[0059] The inner nozzle formed by N inner blades is Figure 5 The regular polygon shown.

[0060] like Figure 6 As shown, the top ends of the N outer blades are connected to the top ends of the N inner blades via a plurality of connecting sleeves 223. In this embodiment, the connecting sleeves are straight sleeves with the same shape as the straight blades on the outer or inner blades. Alternatively, the connecting sleeves may be flexible sleeves.

[0061] The connecting sleeve allows the outer blades to cover the inner blades, forming a flexible whole with the outer and inner blades. This allows the telescopic drive device to drive only the outer blades to achieve the coordinated movement of the inner blades. Furthermore, the number of telescopic drive devices can be significantly reduced, as they no longer need to correspond one to each outer blade.

[0062] In the present invention, the number of telescopic drive devices is M, and M≤N, further, 6≤M≤N; the M telescopic drive devices are evenly arranged along the circumference of the fixed section nozzle; the fixed end of each telescopic drive device is installed on the fixed section nozzle, and the telescopic end of each telescopic drive device is installed on the upper middle part of the corresponding outer fan blade. Each telescopic drive device can actively extend and retract, and can be a telescopic cylinder or a telescopic motor, etc.

[0063] The pressure monitoring sensor includes a nozzle outlet pressure sensor and a back pressure sensor; among them, the nozzle outlet pressure sensor can be used to monitor the exhaust pressure P2 at the tail end outlet of the telescopic section nozzle; the back pressure sensor can be used to monitor the atmospheric pressure P3 of the environment in which the rocket engine is located.

[0064] The thrust generated by the engine nozzle can be divided into two components: momentum thrust and differential pressure thrust. The sum of these two components is the total thrust of the engine. Momentum thrust is the product of the propellant mass flow rate and its corresponding rocket engine exhaust velocity; differential pressure thrust is the product of the difference between the nozzle outlet pressure and the ambient pressure and the nozzle outlet area.

[0065] In the prior art, the optimal state of a nozzle with a fixed area ratio only exists at a specific height, specifically:

[0066] A. When the nozzle outlet pressure P2 is slightly lower than the atmospheric pressure P3, that is, when the nozzle outlet pressure P2 is 40% to 100% of the ambient pressure P3, the nozzle is still in a full flow state, but the expansion efficiency is slightly reduced, and the specific impulse and thrust coefficient are also slightly reduced.

[0067] B. When the nozzle outlet pressure P2 is much lower than the atmospheric pressure P3, the nozzle operates in an over-expanded state, and airflow separation occurs in the nozzle expansion section. The gas jet diameter is smaller than the actual nozzle outlet diameter. At this time, the pressure differential thrust is negative, the thrust decreases, and the severe lateral load generated by the strong unsteady and asymmetric flow field inside the nozzle will endanger the nozzle structure and the rocket's orbital accuracy.

[0068] C. When the nozzle outlet pressure P2 is greater than the atmospheric pressure P3, the nozzle operates in an under-expanded state, the gas in the nozzle does not expand completely, and the specific impulse and thrust coefficient are less than those in the fully expanded state.

[0069] However, for nozzles with fixed geometry, the inlet pressure P1 and outlet pressure P2 are generally kept stable, while the atmospheric pressure P3 varies greatly with altitude, causing the nozzle to be unable to operate in the optimal state most of the time, reducing the engine specific impulse and engine thrust.

[0070] In the present invention, by controlling the active extension and contraction of the M telescopic drive devices, the outlet area of ​​the telescopic nozzle tail end is adjusted, thereby adjusting the exhaust pressure P2 at the outlet of the telescopic nozzle tail end to achieve P2 = P3. At this point, the effective exhaust velocity c of the altitude compensation nozzle is equal to the actual average exhaust velocity v2 of the propellant gas. The altitude compensation nozzle can achieve optimal expansion of the gas, thereby providing optimal thrust, thereby achieving thrust compensation.

[0071] The above-mentioned atmospheric pressure P3 can be measured by a back pressure sensor or a pressure gauge, so that the outlet area can be calculated. Therefore, the required outlet diameter can be calculated based on the fitting circle of the nozzle, and then the extension amount of each extension drive device can be calculated.

[0072] Furthermore, the present invention achieves that the outlet airflow velocity does not change (or changes only slightly) with changes in back pressure by changing the outlet area of ​​the nozzle, and the thrust generated by the nozzle is determined by its outlet flow velocity, so the nozzle can improve efficiency and achieve altitude compensation.

[0073] Generally, the first stage engine of a rocket shuts down and separates at an altitude of about 70 kilometers, and the second stage ignites and continues to accelerate. The separation time of the first and second stages is about 2 minutes and 52 seconds. At 60 kilometers, the atmospheric density is 8.1056×10 -13 Times the atmospheric pressure at sea level (the atmospheric pressure at sea level is 0.101325 MPa).

[0074] In this embodiment, the RS-27 engine is taken as an example. It is a Delta II space launch booster, which uses RP-19 (kerosene) / liquid oxygen bipropellant with a mixing ratio of 2.35. Its combustion chamber pressure is 3.68 MPa (534 Psi), the combustion chamber contraction ratio is 1.67, the nozzle outlet area ratio is 8, and the thermal calculation shows that it takes 294 seconds. The takeoff mass is 200,000 kg, and the working time of one engine is 140 seconds.

[0075] Assuming that the engine design outlet pressure is 0.101325 MPa (i.e., sea level atmospheric pressure), and the combustion chamber pressure remains unchanged at 10.1325 MPa, that is, when the pressure ratio p1 / p2 is 100, the ideal nozzle exhaust velocity is obtained according to the formula:

[0076]

[0077] In the above formula, k is the specific heat ratio of the nozzle exhaust; R is the universal gas constant, which is a known quantity; and p1 is the throat pressure of the height-compensated nozzle.

[0078] In this embodiment, the fixed p1 is 10Mpa, R is 300, and T1 is 3000K, and the curve can be obtained as follows: Figures 7 to 10 As shown. Among them, Figure 7 The curve showing the outlet area ratio changing with altitude under ideal conditions is shown; Figure 8 The curves showing the nozzle outlet area ratio and nozzle outlet pressure P2 of the height compensation nozzle are shown; Figure 9 A graph showing the change of thrust coefficient with altitude at different area ratios is shown; Figure 10 The following graph shows the thrust variation with altitude at different area ratios. t ; A2 is the height compensation nozzle outlet area, A t To compensate for the nozzle throat area.

[0079] from Figures 7 to 10 As can be seen, the altitude-compensating nozzle of the present invention decreases in outlet area ratio and nozzle outlet pressure as altitude increases. During operation, the continuously variable area nozzle experiences reduced outlet pressure, significantly impacting its design, manufacturing costs, and reusability. Furthermore, the continuously variable area nozzle has a greater thrust coefficient than a fixed area ratio nozzle, generating greater thrust.

[0080] The present invention can ensure that the engine nozzle outlet area can be continuously changed without changing the flow rate. By continuously changing the nozzle area ratio at various heights, the outlet pressure is matched with the ambient pressure, so as to achieve a change in the thrust size of the engine under different ambient pressures, improve combustion efficiency, reduce fuel waste, save propellant, and increase payload capacity.

[0081] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A rocket engine with a variable nozzle outlet area, characterized in that: Includes combustion chamber, altitude compensation nozzle and pressure monitoring sensor; The height compensation nozzle includes a fixed section nozzle, a telescopic section nozzle and a telescopic drive device; The fixed section nozzle coaxial seal is set at the tail end of the combustion chamber; The telescopic section nozzle coaxial seal is arranged at the tail end of the fixed section nozzle; The telescopic section nozzle comprises an inner layer nozzle and an outer layer nozzle which are coaxially arranged in sequence from the inside to the outside; The inner nozzle includes N inner blades uniformly distributed along the circumference; wherein N ≥ 8; the bottom of each inner blade is sealedly connected to the tail end of the fixed section nozzle; The outer nozzle includes N outer blades evenly distributed along the circumference; the bottom of each outer blade is sealed and connected to the tail end of the fixed section nozzle; N outer fan blades and N inner fan blades are arranged circumferentially in an alternating manner, with the inner wall surfaces of the N outer fan blades fitting the outer wall surfaces of the N inner fan blades; the top ends of the N outer fan blades are connected to the top ends of the N inner fan blades via a plurality of connecting sleeves; The number of the telescopic drive devices is M, and M≤N; the M telescopic drive devices are evenly arranged along the circumference of the fixed section nozzle; The fixed end of each telescopic drive device is installed on the fixed section nozzle, and the telescopic end of each telescopic drive device is installed on the upper middle part of the corresponding outer fan blade. Each telescopic drive device can actively extend and retract; The pressure monitoring sensor includes a nozzle outlet pressure sensor and a back pressure sensor; among them, the nozzle outlet pressure sensor can be used to monitor the exhaust pressure P2 at the tail end outlet of the telescopic section nozzle; the back pressure sensor can be used to monitor the atmospheric pressure P3 of the environment in which the rocket engine is located.

2. The rocket engine with variable nozzle outlet area according to claim 1, characterized in that: When p2=p3, the effective exhaust velocity c of the altitude compensation nozzle is equal to the actual average exhaust velocity v2 of the propellant gas. At this time, the altitude compensation nozzle can achieve optimal expansion of the gas and thus have the best thrust.

3. The rocket engine with variable nozzle outlet area according to claim 2, characterized in that: The atmospheric pressure P3 will change with the altitude of the rocket engine. By controlling the active extension and contraction amount of the M telescopic drive devices, the outlet area of ​​the tail end of the telescopic section nozzle is adjusted, thereby adjusting the exhaust pressure P2 at the tail end outlet of the telescopic section nozzle, so that P2 = P3, and the altitude compensation nozzle always has the optimal thrust, realizing the altitude compensation of the thrust.

4. The rocket engine with variable nozzle outlet area according to claim 1, characterized in that: The inner nozzle formed by N inner fan blades is a regular polygon.

5. The rocket engine with variable nozzle outlet area according to claim 1, characterized in that: The height compensation nozzle is a tapered tube.

6. The rocket engine with variable nozzle outlet area according to claim 5, characterized in that: The taper of the fixed section nozzle is 15°.

7. The rocket engine with variable nozzle outlet area according to claim 1, characterized in that: N≥20, 6≤M≤N.

8. The rocket engine with variable nozzle outlet area according to claim 1, characterized in that: Each inner fan blade and each outer fan blade includes two V-shaped straight blades; and the V-shaped angle is not less than 160°.

9. The rocket engine with variable nozzle outlet area according to claim 8, characterized in that: By controlling the V-shaped angle, the number N of inner blades or outer blades can be adjusted.

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