A liquid oxygen-methane turbine pump step pressure regulating dynamic seal structure

Abstract

The application discloses a liquid oxygen and methane turbine pump grading pressure regulating dynamic sealing structure, which comprises a sealing shell, a rotating shaft penetrating in the sealing shell, a main sealing rotating assembly, a contact ring, a buffer throttling module, an end face compensation module located downstream of the buffer throttling module and a backflow channel communicated with a low-pressure cavity of a pump body; the buffer throttling module is used for grading pressure reduction, buffer flow stabilization and cavitation weakening of the leakage fluid after passing through a dynamic and static contact sealing pair; the contact ring, the buffer throttling module and the end face compensation module are positioned and connected and detachably installed through a penetrating screw rod and a screw thread locking mechanism. Through the composite structure design of the "contact type main sealing + non-contact type grading throttling", the buffer throttling module performs grading pressure reduction, buffer flow stabilization and cavitation weakening on the small amount of leakage fluid after the main sealing, and the problems that the leakage fluid cannot be timely treated, local pressure fluctuation is easily caused and cavitation bubble collapse impact is caused in the prior art sealing are solved.

Description

Technical Field

[0001] This invention relates to the field of cryogenic propellant delivery and sealing technology for liquid rocket engines, and particularly to a staged pressure regulating dynamic sealing structure for a liquid oxygen-methane turbopump. Background Technology

[0002] The turbopump in a liquid rocket engine is a core component of the liquid oxygen and liquid methane propellant supply system. Its sealing system typically needs to operate stably in a complex environment characterized by extremely low temperatures (around 90 K), high pressures (10–16 MPa), high-speed rotation (20,000–50,000 rpm), and the risk of cavitation. In liquid oxygen, some conventional elastic sealing materials are prone to cryogenic embrittlement, shrinkage deformation, or insufficient compatibility with liquid oxygen, leading to a decline in sealing performance. Simultaneously, high pressure differentials, high rotational speeds, and cryogenic thermal cycling exacerbate wear on the sealing surfaces and fluctuations in preload. If leaked fluid within the sealing cavity cannot be depressurized, stabilized, and discharged in a timely manner, local pressure fluctuations and impact loads generated by the collapse of cavitation bubbles may further damage the sealing structure, thereby affecting the reliability and service life of the turbopump.

[0003] Currently, commonly used sealing methods in liquid oxygen-methane turbopumps include lip seals, mechanical face seals, labyrinth seals, and combined seals. Among these, contact seals offer good initial sealing performance, but under high pressure, high speed, and cryogenic cycling conditions, the dynamic and static seal pairs are prone to frictional wear. Their sealing performance gradually declines with increasing operating time and start-stop cycles, making it difficult to meet the requirements of reusable liquid rocket engines for multiple services and rapid maintenance. Furthermore, existing contact seals often rely on passive pre-tightening or face compensation, which still results in insufficient stability of the contact state and sealing gap under the combined effects of cryogenic contraction, pressure fluctuations, and vibration shocks. In contrast, non-contact sealing structures rely on gap throttling to achieve flow restriction and pressure reduction, offering advantages such as low wear and long service life. However, when used alone, they exhibit significant leakage, making it difficult to independently fulfill the main sealing function in the high-pressure propellant environment of liquid oxygen-methane turbopumps. In addition, existing turbo pump sealing structures mostly adopt an integral installation method, with the sealing components highly integrated with the pump body or end cover. Once the contact sealing pair wears or its performance degrades, it is often necessary to disassemble the entire sealing component or even the related pump body structure, resulting in long maintenance cycles, high consumption of spare parts, and difficulty in reusing some throttling, guiding, and supporting components that have not yet failed.

[0004] Therefore, there is an urgent need to provide a dynamic sealing structure that combines the reliability of contact-type main seals with the advantages of non-contact throttling and pressure reduction. While ensuring sealing capability under low temperature and high pressure environments, it can also perform graded pressure regulation, buffering and stabilizing, cavitation reduction, and low-pressure backflow for a small amount of leaked fluid after the main seal. Furthermore, it can enable modular maintenance of easily worn contact seals and reuse of non-contact throttling structures to meet the engineering application requirements of liquid oxygen methane turbopumps. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a staged pressure regulating dynamic sealing structure for a liquid oxygen methane turbopump.

[0006] To address the problems in the prior art, the present invention adopts the following technical solution: a staged pressure regulating dynamic sealing structure for a liquid oxygen methane turbopump, comprising a sealing housing, a rotating shaft passing through the sealing housing, a main sealing rotating assembly cooperating with and rotating synchronously with the rotating shaft, a contact ring fixedly disposed within the sealing housing, a buffer throttling module fixedly disposed within the sealing housing and located downstream of the contact ring, an end face compensation module located downstream of the buffer throttling module, and a return channel communicating with the low-pressure chamber of the pump body; the main sealing rotating assembly and the contact ring form a dynamic and static contact sealing pair; the buffer throttling module is used to stage-depressurize, buffer and stabilize the flow, and reduce cavitation of the leaked fluid after passing through the dynamic and static contact sealing pair; the return channel is used to guide the residual leaked fluid after passing through the buffer throttling module to the low-pressure chamber of the pump body; the contact ring, buffer throttling module, and end face compensation module are positioned and connected and detachably installed through a through screw and a threaded locking mechanism.

[0007] Preferably, the main sealing rotating assembly includes a sealing inner ring that mates with the rotating shaft, a main sealing ring located on one side of the sealing inner ring and in contact with the contact ring, and a dynamic sealing ring disposed on the main sealing ring and in contact with the inner side of the sealing housing; the sealing inner ring, the main sealing ring, and the dynamic sealing ring together constitute the dynamic sealing section.

[0008] Preferably, the sealing housing is a NiTi shape memory alloy sealing housing. The NiTi shape memory alloy sealing housing undergoes temperature response deformation in a low-temperature environment, thereby applying radial preload compensation to the main sealing rotating assembly to improve the stability of the axial end face fit between the main sealing ring and the contact ring in the main sealing rotating assembly.

[0009] Preferably, the buffer throttling module includes an initial throttling section, an intermediate diversion throttling section, and an end stabilizing throttling section. The initial throttling section includes a pre-tightened metal bellows. The intermediate diversion throttling section includes several axially connected Venturi diverter blocks, forming a continuously varying throttling channel between the Venturi diverter blocks and the sealing shell. The end stabilizing throttling section includes a gradient throttling gap and a buffer guide, with a buffer guide groove provided on the outer surface of the buffer guide. One end of the pre-tightened metal bellows is pressed and fixed to a contact ring, and the other end abuts against an adjacent Venturi diverter block. The pre-tightened metal bellows works in conjunction with the elastic element provided in the end face compensation module to provide a limited axial pressure relief displacement for the intermediate diversion throttling section under pressure fluctuations, so that the effective gap and pressure difference distribution of the throttling channel tend to stabilize.

[0010] The flow area of ​​the gradient throttling gap changes gradient along the axis of rotation. The leaking fluid after being diverted by the Venturi diverter block is further stabilized and depressurized under the action of the gradient throttling gap and the buffer guide channel, and is then guided to the inlet of the guide end face compensation module and the return channel.

[0011] Preferably, the throttling channel formed between the Venturi diverter block and the sealing housing includes a front conical contraction section, a throat, and a rear diffuser section. The equivalent flow area at the inlet of the front conical contraction section is larger than that at the throat, and the equivalent flow area at the outlet of the rear diffuser section is larger than that at the throat. Adjacent Venturi diverter blocks are connected to form an asymmetric diversion and pressure reduction channel with Tesla valve-like characteristics, which is used to dissipate energy of the leaking fluid step by step during contraction, diversion, diffusion, and reversal, thereby increasing the flow resistance of the leaking fluid and weakening the reverse impact of the leaking fluid.

[0012] Preferably, the tail end of the Venturi divider block forms a swirling buffer chamber, in which the leaking fluid forms a low-speed vortex zone, causing the air bubbles entrained in the leaking fluid to migrate to the downstream low-pressure area and reducing the retention of air bubbles near the throttling channel and the dynamic-static contact sealing interface; the swirling buffer chamber is connected to the return channel through a degassing guide channel, which is used to guide the migrated air bubbles and the depressurized leaking fluid into the return channel.

[0013] Preferably, the flow rate of the leaking fluid in the throttling channel and the flow area at the throat satisfy the following condition: ; In the formula, The volumetric flow rate of the leaking fluid. This refers to the flow area of ​​the throat. For flow coefficient, The inlet pressure of the front conical contraction section, For throat pressure, The density of the leaking fluid; throat pressure The following conditions must be met: ; This is the saturated vapor pressure of the liquid oxygen medium at the current operating temperature. For safety pressure margin.

[0014] Preferably, the gradient throttling gap is divided into several stages of throttling gaps along the direction of leakage fluid flow, the first... Equivalent flow area of ​​the throttling gap satisfy: ; in, The gap flow coefficient, For the first Pressure drop across the throttling gap, The density of the leaking fluid; No. Radial gap height of the throttling gap for: ; In the formula, For the first The average radius of the throttling gap; The radial gap height dimensions of two adjacent throttling gaps must satisfy the following condition: ; in, For the first The radial gap height of the throttling gap. For the first The average radius of the throttling gap; For the first Pressure drop in the throttling gap.

[0015] Preferably, the end-face compensation module includes a drainage collar, an elastic element, and an elastic sealing gasket. The drainage collar is provided with an annular guide surface, which guides the leaked fluid after pressure reduction by the buffer throttling module to the return channel. The elastic sealing gasket is sleeved on the rotating shaft, and the outer side of the elastic sealing gasket is fixedly connected to one end of the sealing housing. An end-face static sealing ring is provided between the elastic sealing gasket and the sealing housing. The elastic element is provided between the drainage collar and the elastic sealing gasket, and applies elastic pressure toward the buffer throttling module to the drainage collar.

[0016] Preferably, the main sealing rotating assembly, the buffer throttling module, and the end face compensation module are all provided with through holes through which the through screw can pass. One end of the through screw passes through the end face compensation module and the buffer throttling module in sequence and is then fixedly connected to the contact ring. The through screw is locked and fixed to the end face of the end face compensation module by a nut.

[0017] The beneficial effects of this invention are: 1. This invention employs a composite structural design of "contact-type main seal + non-contact graded throttling". On one hand, the dynamic and static contact sealing pair formed by the rotating main seal assembly and the contact ring continues the advantage of the excellent initial sealing performance of the contact seal, which can directly resist the impact of high-pressure propellant in the liquid oxygen methane turbopump, prevent large-scale leakage, and ensure the sealing stability of the turbopump's core operating conditions. On the other hand, the buffer throttling module performs graded pressure reduction, buffering and stabilizing, and cavitation reduction on the small amount of leaked fluid after the main seal, completely solving the problems of the inability to handle leaked fluid in time and the easy occurrence of local pressure fluctuations and cavitation bubble collapse impacts in existing seals.

[0018] 2. The initial throttling section, intermediate diversion throttling section, and final stabilizing throttling section in the buffer throttling module work together to gradually reduce the pressure of the leaking fluid from high pressure to a level matching the low-pressure chamber of the pump body through the elastic buffering of the pre-tightened metal bellows, the step-by-step pressure reduction of the Venturi diversion blocks, and the stabilizing flow guidance of the gradient throttling gaps. This effectively dissipates the energy of the leaking fluid and reduces its impact on the sealing surfaces. At the same time, the asymmetric diversion and pressure reduction channel with Tesla valve-like characteristics formed between the Venturi diversion blocks can suppress the reverse impact of the leaking fluid, further improving the anti-interference capability of the sealing system. The swirling buffer chamber allows cavitation bubbles entrained in the leaking fluid to migrate to the low-pressure area, reducing the retention of bubbles in the throttling channel and the dynamic-static contact sealing interface, avoiding damage to the sealing structure from the impact load generated by bubble collapse, and reducing the risk of seal failure from the root.

[0019] 3. The NiTi shape memory alloy sealing housing achieves adaptive preload compensation in low-temperature environments, which can apply a stable radial preload to the main sealing rotating assembly, reduce the radial clearance, eccentricity and tilting tendency of the main sealing rotating assembly during operation, thereby improving the uniformity and stability of the end face contact between the main sealing ring and the contact ring, and thus improving the fit effect of the dynamic and static contact sealing pairs.

[0020] 4. Through the design of the through screw and threaded locking mechanism, this invention realizes the positioning connection and detachable installation of the contact ring, buffer throttling module and end face compensation module, realizing a modular installation and maintenance system, which greatly improves maintenance convenience and reduces operation and maintenance costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 This is a schematic diagram of the Venturi splitter block.

[0023] Figure 3 This is a front view of the Venturi splitter block.

[0024] Figure 4 This is an exploded view of the present invention.

[0025] Figure 5 This is a schematic diagram of the flow of the leaking fluid in this invention.

[0026] In the diagram: 1. Sealing shell; 2. Inner sealing ring; 3. Sealing cavity; 4. Main sealing ring; 5. Pre-tightened metal bellows; 6. Venturi diverter block; 6-1. Inner ring body; 6-2. Outer ring body; 6-3. Connecting column; 7. Degassing guide groove; 8. Strain sensor; 9. Temperature sensor; 10. Gradient throttling gap; 11. Buffer guide groove; 12. Drainage collar; 13. Elastic sealing gasket; 14. Flexible metal bellows; 15. Spring; 16. Dynamic sealing ring; 17. Silicon nitride ceramic ring; 18. Sealing block; 19. Return channel; 20. Nut; 21. Through screw; 22. End face static sealing ring; 23. Fixing bolt; 24. Rotating shaft. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0028] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0029] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0030] like Figures 1 to 5As shown, a staged pressure regulating dynamic sealing structure for a liquid oxygen methane turbopump includes a sealing housing 1, a rotating shaft 24 passing through the sealing housing 1, a main sealing rotating assembly that cooperates with and rotates synchronously with the rotating shaft 24, a contact ring 17 fixedly disposed within the sealing housing 1, a buffer throttling module fixedly disposed within the sealing housing 1 and located downstream of the contact ring 17, an end face compensation module located downstream of the buffer throttling module, and a return channel 19 communicating with the low-pressure chamber of the pump body. The main sealing rotating assembly and the contact ring 17 form a dynamic and static contact sealing pair. The buffer throttling module is used to stage and reduce the pressure of the leaked fluid after passing through the dynamic and static contact sealing pair, buffer and stabilize the flow, and reduce cavitation. The return channel 19 is used to guide the residual leaked fluid after passing through the buffer throttling module to the low-pressure chamber of the pump body. The contact ring 17, the buffer throttling module, and the end face compensation module are positioned and connected and can be detachably installed through a through screw 21 and a threaded locking mechanism.

[0031] The sealing housing 1 is fixedly installed at the end cover flange of the turbine pump body and is connected to the pump body by end face positioning, interference fit or threaded locking. After the sealing housing 1 is installed, a closed installation interface is formed between the sealing housing 1 and the pump body. The working medium does not flow through the outside of the sealing housing 1, but flows in a controlled manner in the space formed between the sealing housing 1 and the rotating shaft 24.

[0032] The main sealing rotating assembly includes a sealing inner ring 2 that mates with the rotating shaft 24, a main sealing ring 4 located on one side of the sealing inner ring 2 and in contact with the contact ring 17, and a dynamic sealing ring 16 disposed on the main sealing ring 4 and in contact with the inner side of the sealing housing 1; the sealing inner ring 2, the main sealing ring 4, and the dynamic sealing ring 16 together constitute a dynamic sealing section. The dynamic sealing ring 16 is disposed in the main sealing area, and the sealing inner ring 2, the main sealing ring 4, and the dynamic sealing ring 16 all rotate synchronously with the rotating shaft 24, together forming the dynamic sealing section. Both the sealing inner ring 2 and the main sealing ring 4 are made of PTFE-based composite material, which can reduce friction and wear at the dynamic and static contact sealing interface and improve its adaptability in liquid oxygen cryogenic media. The PTFE-based composite material is an engineering material made by blending polytetrafluoroethylene (PTFE) as a matrix with added fibers, inorganic materials, metals, nanofillers, or polymers. The cavity inside the sealing housing 1 is the sealing cavity 3.

[0033] The contact ring 17 is made of silicon nitride ceramic material, which has high wear resistance. One side of the contact ring 17 contacts one side of the main sealing ring 4. The contact ring 17 is fixedly installed in the sealing housing 1 and remains stationary, not rotating with the rotating shaft 24. The contact ring 17 and the main sealing ring 4, which rotates with the shaft, form a dynamic-static contact sealing pair, which performs the main sealing function. The contact ring 17 and its downstream buffer throttling module and end face compensation module together constitute the static sealing section. The static sealing section contacts and engages with the main sealing ring 4 in the dynamic sealing section through the contact ring 17, thereby achieving a dynamic-static sealing transition. Silicon nitride ceramic material has good low-temperature resistance, wear resistance, and erosion resistance, which can improve the reliability of the contact sealing pair under conditions of high-speed rotation, low-temperature cycling, and leakage fluid erosion.

[0034] The sealing shell 1 of this application adopts NiTi shape memory alloy sealing shell 1. NiTi shape memory alloy is an intermetallic compound composed of nickel (Ni) and titanium (Ti) in a near equiatomic ratio (about 1:1). It has both shape memory effect (SME) and superelasticity (SE) and is currently the most widely used and best performing memory alloy.

[0035] The NiTi shape memory alloy sealing housing 1 undergoes temperature-responsive deformation at low temperatures, thereby applying radial preload compensation to the main sealing rotating assembly. The radial deformation of the NiTi shape memory alloy sealing housing 1 does not directly generate axial compression displacement, but rather improves the radial constraint state of the main sealing rotating assembly through the preload compensation (radial deformation) of the NiTi shape memory alloy sealing housing 1. By reducing the radial clearance and axial movement of the main sealing ring 4 through radial constraint, the stability of the axial end face fit between the main sealing ring 4 and the contact ring 17 in the main sealing rotating assembly is indirectly improved.

[0036] The NiTi shape memory alloy sealing housing 1 undergoes temperature-responsive deformation within the liquid oxygen cryogenic operating temperature range, primarily manifested as recoverable shrinkage along the radial direction of the sealing housing 1. This radial shrinkage deformation applies additional radial preload compensation to the main sealing rotating assembly, reducing the radial clearance, eccentricity, and tilting tendency of the main sealing rotating assembly during operation. This improves the uniformity and stability of the end-face contact between the main sealing ring 4 and the contact ring 17, thereby enhancing the fit of the dynamic and static contact sealing pairs.

[0037] In this embodiment, the NiTi shape memory alloy sealing shell is considered as an annular thin shell, and the radial inward shrinkage is taken as a positive value, then its radial displacement Equivalent strain in the circumferential direction It can be represented as: ; In the above formula, The average radius of the sealed housing, Operating temperature The circumferential equivalent stress is for sealing the shell.

[0038] The circumferential equivalent strain consists of a thermal shrinkage strain term and a phase transformation recovery strain term, namely: ; In the formula, For reference assembly temperature, This represents the equivalent linear expansion coefficient of the NiTi shape memory alloy sealing shell within the corresponding temperature range. This is the equivalent phase transition recovery strain that can be used for radial contraction after training. This represents the volume fraction of martensite under temperature-stress coupling.

[0039] During the cooling process, the martensite volume fraction in the NiTi shape memory alloy sealing shell... The following segmentation relationship is satisfied: ; in: ; In the formula, and These are the initiation and termination temperatures of the martensitic phase transformation during the cooling process under stress-free conditions, respectively. and To seal the housing under circumferential stress The initiation and termination temperatures of the martensitic phase transformation under the action. When the operating temperature is from... Descending to During the interval, the volume fraction of martensite in the sealed shell gradually increases, thereby driving the sealed shell to produce radial recovery shrinkage deformation. Let be the stress-temperature slope constant of the cooling branch, and The positive direction should be chosen based on the direction that promotes the martensitic phase transformation.

[0040] Therefore, the radial displacement of the NiTi shape memory alloy sealing shell The following conditions must be met with the operating temperature: ; Correspondingly, the inner diameter of the sealing housing is reduced by It can be represented as: ; When the operating temperature decreases from the reference assembly temperature to the liquid oxygen operating temperature range, the martensite volume fraction increases with decreasing temperature, and the radial shrinkage of the sealing shell increases accordingly; when the temperature is below... At this point, the phase transformation recovery strain tends to saturate, and the sealing shell can still maintain radial preload compensation through the thermal shrinkage term and the already formed phase transformation recovery term. Through the above temperature-radial displacement relationship, the main sealing ring of the main sealing rotating assembly can maintain a stable radial constraint and end face fit under low temperature and high pressure conditions.

[0041] The above parameters , , , and This can be obtained through differential scanning calorimetry, free cooling shrinkage testing, and low-temperature constrained calibration testing. Among these, and It can be determined by differential scanning calorimetry. and It can be obtained by fitting the free cooling shrinkage test. It can be obtained through low-temperature thermo-mechanical coupling calibration tests under constrained preload conditions. The composition ratio and heat treatment state of the NiTi shape memory alloy sealing shell can be adjusted according to the target liquid oxygen low-temperature operating range so that its temperature response deformation matches the preload compensation requirements of the main seal.

[0042] Specifically, the buffer throttling module includes an initial throttling section, an intermediate diversion throttling section, and an end stabilizing throttling section. The initial throttling section includes a pre-tightened metal bellows 5. The intermediate diversion throttling section includes several axially connected Venturi diverter blocks 6, forming a continuously varying throttling channel between the Venturi diverter blocks 6 and the sealing housing 1. The end stabilizing throttling section includes a gradient throttling gap 10 and a buffer guide groove. One end of the pre-tightened metal bellows 5 is pressed and fixed to the contact ring 17, and the other end is connected to the adjacent Venturi diverter block 6. The pre-tightened metal bellows 5 works in conjunction with the elastic element in the end face compensation module to provide a limited axial pressure relief displacement for the intermediate diversion and throttling section under pressure fluctuations, so as to stabilize the effective gap and pressure difference distribution of the throttling channel; the flow area of ​​the gradient throttling gap 10 changes gradient along the axis of the rotation axis 24, and the leakage fluid after being diverted by the Venturi diverting block 6 is further stabilized and depressurized under the action of the gradient throttling gap 10 and the buffer guide groove and is guided to the inlet of the guide end face compensation module and the return channel 19.

[0043] The throttling channel formed between the Venturi divider block 6 and the sealing shell 1 comprises a front conical contraction section, a throat, and a rear diffuser section. The equivalent flow area at the inlet of the front conical contraction section is larger than that at the throat, and the equivalent flow area at the outlet of the rear diffuser section is larger than that at the throat. After being guided by contraction, local pressure regulation, and diffuser stabilization, the leaking fluid migrates downstream to the low-pressure region along the continuously changing throttling channel, thereby reducing the retention of air bubbles near the dynamic-static contact sealing interface.

[0044] The geometric parameters of the Venturi manifold are designed to match the target leakage flow rate, inlet pressure, backflow pressure, saturated vapor pressure of the medium, and installation space. The equivalent flow area at the inlet, throat, and outlet of the throttling channel formed between the Venturi manifold and the sealing shell are denoted as follows: , and The corresponding equivalent hydraulic diameters are denoted as follows: , and Its throat diameter is larger than satisfy: ; Wherein, the inlet cross-section of the front conical contraction section is larger than the throat cross-section, and the outlet cross-section of the rear diffuser section is larger than the throat cross-section, that is: ; The following condition must be satisfied between the flow rate of the leaking fluid in the throttling channel and the throat flow area: ; In the formula, The volumetric flow rate of the leaking fluid. This refers to the flow area of ​​the throat. For flow coefficient, The inlet pressure of the front conical contraction section, For throat pressure, Let be the density of the leaking fluid. The throat area can be determined based on the target leakage flow rate and allowable pressure drop using the above relationship. This allows the leaking fluid to achieve flow restriction and pressure reduction during the contraction, throat throttling, and diffusion processes.

[0045] To reduce the risk of cavitation, throat pressure The following conditions must be met: ; This is the saturated vapor pressure of the liquid oxygen medium at the current operating temperature. To ensure a safe pressure margin, by controlling the throat area, the angle of the contraction section, and the angle of the diffusion section, it is possible to avoid excessively low local pressure in the throat, which could induce severe cavitation.

[0046] Furthermore, the connection between adjacent Venturi diverter blocks forms an asymmetric diversion and pressure reduction channel with Tesla-like characteristics. This channel allows the leaking fluid to dissipate energy step by step during contraction, diversion, diffusion, and reversal, increasing the flow resistance of the leaking fluid, weakening the reverse impact, and reducing the flow velocity and pressure fluctuations. The forward resistance coefficient and the reverse disturbance resistance coefficient are denoted as... and asymmetric drag ratio Satisfy the following formula: ; This asymmetric diversion and pressure reduction channel allows the leaking fluid to gradually reduce pressure and consume energy during forward flow, while also mitigating reverse impacts and pressure fluctuations.

[0047] The Venturi divider block 6 has a continuous, smooth transition structure in its outer profile, creating a continuous curvature connection between the front conical contraction section, the throat, and the rear diffuser section of the throttling channel. This reduces local flow separation, erosion, and bubble retention. The Venturi divider block 6 includes an inner ring 6-1 and an outer ring 6-2, which are connected by six circumferentially distributed connecting posts 6-3 to maintain stable spacing and connection strength between the inner ring 6-1 and the outer ring 6-2. The inner ring 6-1 has a shaft hole through which the rotating shaft 24 can pass.

[0048] The tail end of the Venturi divider block 6 forms a swirling buffer chamber. Within this chamber, the leaking fluid forms a low-speed vortex zone, causing entrained air bubbles to migrate downstream to a low-pressure region and reducing bubble retention near the throttling channel and the dynamic-static contact sealing interface. The swirling buffer chamber is connected to the return channel 19 via a degassing guide channel, which guides the migrated air bubbles and the depressurized leaking fluid into the return channel 19. Neither the swirling buffer chamber nor the degassing guide channel 7 is directly connected to the external environment of the sealing housing 1 to prevent cryogenic propellant leakage.

[0049] A gradient throttling gap 10 and a buffer guide 11 are provided downstream of the Venturi diverter block 6. The buffer guide 11 has a circular annular structure and is sleeved on the outside of the rotating shaft 24. A buffer guide groove is provided on the outer surface of the buffer guide 11. The gradient throttling gap 10 is formed on the inner wall of the outer side of the stationary throttling member, and the buffer guide groove is formed on the outer wall of the inner side of the adjacent stationary member. Together, they form a continuously changing leakage fluid flow channel. Through the stepped cross-sectional change of the gradient throttling gap and the guiding effect of the continuous groove of the buffer guide groove, the leakage fluid after the Venturi diversion can be further stabilized and depressurized, and then guided to the end face compensation module and the inlet of the return channel.

[0050] The grooves of the buffer guide 11 are arranged sequentially along the flow direction of the leaking fluid, and the groove depth is... and slot width The depth gradually increases from upstream to downstream to form a progressively expanding buffer channel. Preferably, the depth increase of adjacent buffer guide channels 11 satisfies the following condition: ; The increase in slot width satisfies: ; in, and The first The depth and width of the toothed grooves. Through the aforementioned gradually expanding groove structure, the local velocity and pressure gradient of the leaking fluid are gradually reduced during the flow process, and a local low-velocity backflow zone and vortex buffer zone are formed inside the groove, thereby weakening the impact of high-speed leaking fluid on downstream structures and improving the fluid stabilization and buffering effect.

[0051] The buffer throttling module can be machined from Inconel 718 nickel-based alloy to improve its dimensional stability, fatigue resistance and cavitation erosion resistance under conditions of liquid oxygen cryogenic, high pressure and leakage fluid scouring.

[0052] Furthermore, the gradient throttling gap is divided into several stages of throttling gaps along the direction of leakage fluid flow, denoted as the th stage. The inlet and outlet pressures of the throttling gap are respectively and Then the first Pressure drop of the throttling gap for: ; No. Equivalent flow area of ​​the throttling gap satisfy: ; in, The gap flow coefficient, For the first Pressure drop across the throttling gap, The density of the leaking fluid.

[0053] In the scheme, the gradient throttling gap is an annular gap, the first... Radial gap height of the throttling gap for: ; In the formula, For the first The average radius of the throttling gap; The radial gap height dimensions of two adjacent throttling gaps must satisfy the following condition: ; in, For the first The radial gap height of the throttling gap. For the first The average radius of the throttling gap; For the first Pressure drop in the throttling gap.

[0054] By using the above-mentioned size matching relationship, the gradient throttling gap can achieve differential pressure distribution along the flow direction, avoid local pressure drop concentration, and reduce the risk of cavitation bubble retention and pressure pulsation.

[0055] Specifically, the end-face compensation module includes a drainage collar 12, an elastic element, and an elastic sealing gasket 13. The drainage collar 12 has an annular guide surface that directs the leaked fluid, after being depressurized by the buffer throttling module, to the return channel 19. The elastic sealing gasket 13 is fitted onto the rotating shaft 24, and its outer side is fixedly connected to one end of the sealing housing 1, secured by a fixing bolt 23. A static end-face sealing ring 22 is provided between the elastic sealing gasket 13 and the sealing housing 1. The elastic element is positioned between the drainage collar 12 and the elastic sealing gasket 13, applying elastic pressure towards the buffer throttling module to the drainage collar 12. A sealing block 18, with an annular structure, is provided between the drainage collar 12 and the elastic sealing gasket 13. Both ends of the sealing block 18 are respectively pressed against the drainage collar 12 and the elastic sealing gasket 13.

[0056] A flexible metal corrugated sheet 14 is provided on the side of the elastic sealing gasket 13 facing the drainage collar. The flexible metal corrugated sheet 14 is used to compensate for axial displacement caused by low temperature shrinkage, pressure fluctuations, and assembly errors. The elastic sealing gasket is used to improve the fit between the stationary end faces and absorb minor vibration impacts. Among them, the end face compensation module does not serve as the main pressure-bearing sealing unit, but rather works with the buffer throttling module and the return channel to maintain pressure stability at the sealing end.

[0057] The flexible metal corrugated sheet 14 adopts a thin-walled corrugated structure that is elastically deformable along the axial direction, with its crests and troughs continuously distributed along the circumference. When the sealing structure is affected by low-temperature shrinkage, axial pressure fluctuations, or assembly deviations, the flexible metal corrugated sheet 14 generates axial micro-displacement compensation through the elastic expansion and contraction of the corrugated structure to maintain a stable fit between the end-face compensation module and the adjacent stationary structure. When the leakage fluid pressure experiences transient fluctuations, the flexible metal corrugated sheet 14 can absorb part of the axial impact load through elastic deformation and reduce the direct transmission of pressure pulsations to the stationary end-face area, thereby reducing local contact stress concentration and structural vibration. Because the corrugated structure has low axial stiffness and high radial stability, it can still maintain stable elastic compensation capability in the low-temperature environment of liquid oxygen and together with the spring 15, it forms an axially compliant compensation mechanism.

[0058] In this embodiment, the elastic element is spring 15.

[0059] The return channel 19 is correspondingly configured with the guide ring 12. The inlet of the return channel 19 is connected to the low-pressure chamber downstream of the buffer throttling module, and the outlet of the return channel 19 is connected to the low-pressure chamber inside the turbine pump body. During operation, the residual leakage fluid after being depressurized by the buffer throttling module enters the return channel 19 under the action of pressure difference and is guided back to the low-pressure chamber inside the pump body. This achieves pressure balance between the sealing chamber 3 inside the sealing housing 1 and the low-pressure chamber inside the pump body, preventing the leakage fluid from stagnating in the sealing chamber 3 inside the sealing housing 1 for a long time. A one-way valve is installed in the return channel 19 to suppress the backflow of fluid from the low-pressure chamber of the pump body to the sealing chamber 3.

[0060] The main sealing rotating assembly, the buffer throttling module, and the end face compensation module are all provided with through holes through which the through screw 21 can pass. One end of the through screw 21 passes through the end face compensation module and the buffer throttling module in sequence and is then fixedly connected to the contact ring 17. The through screw 21 is locked and fixed to the end face of the end face compensation module by a nut 20. Specifically, the flow guiding ring 12, the sealing block 18, the elastic sealing gasket 13, the buffer guide 11, the Venturi diverter block 6, and the pre-tightened metal bellows 5 are all provided with through holes. The contact ring 17 is provided with a threaded hole that matches the through screw 21, and the through screw 21 is fastened to the threaded hole on the contact ring 17.

[0061] The through screw 21 is made of A286 stainless steel and can be subjected to low-temperature toughness strengthening, fatigue life strengthening or surface anti-seize treatment. The threaded area can be coated with a low-temperature anti-jamming coating to ensure reliability under multiple disassembly and assembly conditions.

[0062] A strain sensor 8 and a temperature sensor 9 are installed on the outside of the sealing housing 1. The strain sensor 8 is used to collect changes in the force applied to the sealing housing 1, and the temperature sensor 9 is used to monitor the thermal state under low-temperature operating conditions. The signals collected by the sensors can be transmitted to an external control unit to assist in judging the pre-tightening state of the sealing structure, pressure fluctuations, and abnormal impacts. When the monitored parameters exceed the preset range, an early warning signal can be sent to the control system so that measures such as deceleration, shutdown, or maintenance inspection can be taken.

[0063] The installation process of this invention is as follows: Before installation, the rotary shaft 24, sealing housing 1, main sealing rotating assembly, contact ring 17, and other components of the liquid oxygen methane turbopump staged pressure regulating dynamic sealing structure of the present invention are cleaned, de-iced, and inspected for foreign objects. During installation, the inner sealing ring 2 and the main sealing ring 4 are first assembled at the corresponding positions on the rotary shaft 24 so that they can rotate synchronously with the rotary shaft 24; then the contact ring 17, pre-tightened metal bellows 5, Venturi diverter block 6, drainage sleeve 12, and end face compensation component are sequentially installed into the corresponding positions in the sealing housing 1; subsequently, the through screw 21 is sequentially passed through the through holes on the elastic sealing gasket 13, sealing block 18, drainage sleeve 12, buffer guide 11, Venturi diverter block 6, and pre-tightened metal bellows 5 and then fastened to the threaded hole on the contact ring 17. A gasket and nut 20 are then fitted onto the through screw 21, and the locking and fixing between the through screw 21 and the end face compensation module is achieved by tightening the nut 20.

[0064] During equipment operation, the high-pressure, low-temperature medium first acts on the main sealing rotating assembly; the inner sealing ring 2 and the main sealing ring 4 rotate synchronously with the rotating shaft 24, and the main sealing ring 4 and the contact ring 17 form a dynamic and static contact sealing pair; the shape memory response generated by the sealing housing 1 at low temperature provides pre-tightening compensation for the dynamic and static sealing pair, so that the contact interface maintains a stable fit; a small amount of leakage fluid through the main sealing rotating assembly enters the buffer throttling module, and then passes through the pre-tightening metal bellows 5, the Venturi diverter block 6, the gradient throttling gap 10, and the buffer guide groove in sequence, under the action of initial buffering, Tesla-like valve-type diversion pressure reduction, gradient throttling, and flow stabilization, the pressure is reduced step by step. The fluid after pressure reduction enters the end face compensation module, and is guided by the guide collar 12 to the return channel 19, and finally returns to the low-pressure chamber of the pump body.

[0065] After the equipment stops operating, the residual fluid in the sealing cavity 3 inside the sealing housing 1 can continue to slowly flow back to the low-pressure cavity of the pump body through the return channel 19 under the action of residual pressure difference. The one-way valve can restrict the fluid in the low-pressure cavity from flowing back into the sealing cavity 3, and the buffer throttling module can still play a role in flow limiting and buffering during the shutdown phase, thereby reducing the impact of instantaneous backflow impact on the sealing structure.

[0066] During maintenance of this device, loosening the nut 20 at the tail end of the through screw 21 and pulling out the through screw 21 allows for easy disassembly of the buffer throttling module and end face compensation module, exposing the maintenance space for the relevant contact parts of the main seal. In actual maintenance, depending on wear or damage, the Venturi diverter block 6, end face compensation components, elastic sealing gasket 13, or contact seals can be inspected, replaced, or maintained without replacing the entire sealing structure. This shortens the maintenance cycle, reduces spare parts consumption, and improves the reusability of the sealing system.

[0067] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A staged pressure regulating dynamic seal structure for a liquid oxygen-methane turbopump, characterized in that, The system includes a sealing housing, a rotating shaft passing through the sealing housing, a main sealing rotating assembly that cooperates with and rotates synchronously with the rotating shaft, a contact ring fixedly disposed within the sealing housing, a buffer throttling module fixedly disposed within the sealing housing and located downstream of the contact ring, an end face compensation module located downstream of the buffer throttling module, and a return channel communicating with the low-pressure chamber of the pump body. The main sealing rotating assembly and the contact ring form a dynamic and static contact sealing pair. The buffer throttling module is used to perform graded pressure reduction, buffer flow stabilization, and cavitation reduction on the leaking fluid after passing through the dynamic and static contact sealing pair. The return channel is used to guide the residual leaking fluid after passing through the buffer throttling module to the low-pressure chamber of the pump body. The contact ring, buffer throttling module, and end face compensation module are positioned and connected and can be detachably installed through a through screw and a threaded locking mechanism. The buffer throttling module includes an initial throttling section, an intermediate diversion throttling section, and an end stabilizing throttling section. The initial throttling section includes a pre-tightened metal bellows. The intermediate diversion throttling section includes several axially connected Venturi diverter blocks, forming a continuously varying throttling channel between the Venturi diverter blocks and the sealing shell. The end stabilizing throttling section includes a gradient throttling gap and a buffer guide, with a buffer guide groove provided on the outer surface of the buffer guide. One end of the pre-tightened metal bellows is pressed and fixed to the contact ring, and the other end is connected to... Adjacent Venturi diverter blocks abut against each other; the pre-tightened metal bellows and the elastic element set in the end face compensation module work together to provide a limited axial pressure relief displacement for the intermediate diverting and throttling section under pressure fluctuations, so as to stabilize the effective gap and pressure difference distribution of the throttling channel; the flow area of ​​the gradient throttling gap changes gradient along the axis of rotation, and the leaked fluid after being diverted by the Venturi diverter blocks is further stabilized and depressurized under the action of the gradient throttling gap and the buffer guide groove and is guided to the inlet of the end face compensation module and the return channel.

2. The staged pressure regulating dynamic sealing structure for the liquid oxygen-methane turbopump according to claim 1, characterized in that, The main sealing rotating assembly includes a sealing inner ring that mates with the rotating shaft, a main sealing ring located on one side of the sealing inner ring and in contact with the contact ring, and a dynamic sealing ring disposed on the main sealing ring and in contact with the inner side of the sealing housing; the sealing inner ring, the main sealing ring, and the dynamic sealing ring together constitute the dynamic sealing section.

3. The staged pressure regulating dynamic sealing structure for the liquid oxygen-methane turbopump according to claim 1, characterized in that, The sealing housing is a NiTi shape memory alloy sealing housing. The NiTi shape memory alloy sealing housing undergoes temperature response deformation in a low-temperature environment, thereby applying radial preload compensation to the main sealing rotating assembly to improve the stability of the axial end face fit between the main sealing ring and the contact ring in the main sealing rotating assembly.

4. The staged pressure regulating dynamic seal structure for the liquid oxygen-methane turbopump according to claim 1, characterized in that, The throttling channel formed between the Venturi diverter block and the sealing shell includes a front conical contraction section, a throat, and a rear diffuser section. The equivalent flow area at the inlet of the front conical contraction section is larger than that at the throat, and the equivalent flow area at the outlet of the rear diffuser section is larger than that at the throat. Adjacent Venturi diverter blocks are connected to form an asymmetric diversion and pressure reduction channel with Tesla valve-like characteristics. This channel is used to dissipate energy of the leaking fluid step by step during contraction, diversion, diffusion, and reversal, thereby increasing the flow resistance of the leaking fluid and weakening the reverse impact of the leaking fluid.

5. The staged pressure regulating dynamic seal structure for the liquid oxygen-methane turbopump according to claim 4, characterized in that, The tail end of the Venturi divider forms a swirling buffer chamber, in which the leaking fluid forms a low-speed vortex zone, causing the air bubbles entrained in the leaking fluid to migrate downstream to the low-pressure area and reducing the retention of air bubbles near the throttling channel and the dynamic-static contact sealing interface; the swirling buffer chamber is connected to the return channel through a degassing guide channel, which is used to guide the migrated air bubbles and the depressurized leaking fluid into the return channel.

6. The staged pressure regulating dynamic sealing structure for the liquid oxygen-methane turbopump according to claim 4, characterized in that, The following condition must be satisfied between the flow rate of the leaking fluid in the throttling channel and the throat flow area: ； In the formula, The volumetric flow rate of the leaking fluid. This refers to the flow area of ​​the throat. For flow coefficient, The inlet pressure of the front conical contraction section, For throat pressure, The density of the leaking fluid; This refers to the ratio of the throat diameter; throat pressure The following conditions must be met: ； This is the saturated vapor pressure of the liquid oxygen medium at the current operating temperature. For safety pressure margin.

7. The staged pressure regulating dynamic seal structure for the liquid oxygen-methane turbopump according to claim 6, characterized in that, The gradient throttling gap is divided into several stages of throttling gaps along the direction of leakage fluid flow. Equivalent flow area of ​​the throttling gap satisfy: ； in, The gap flow coefficient is... For the first Pressure drop across the throttling gap, The density of the leaking fluid; No. Radial gap height of the throttling gap for: ； In the formula, For the first The average radius of the throttling gap; The radial gap height dimensions of two adjacent throttling gaps must satisfy the following condition: ； in, For the first The radial gap height of the throttling gap. For the first The average radius of the throttling gap; For the first Pressure drop in the throttling gap.

8. The staged pressure regulating dynamic seal structure for the liquid oxygen-methane turbopump according to claim 1, characterized in that, The end-face compensation module includes a drainage collar, an elastic element, and an elastic sealing gasket. The drainage collar has an annular guide surface that guides the leaked fluid after pressure reduction by the buffer throttling module to the return channel. The elastic sealing gasket is sleeved on the rotating shaft, and its outer side is fixedly connected to one end of the sealing housing. An end-face static sealing ring is provided between the elastic sealing gasket and the sealing housing. The elastic element is located between the drainage collar and the elastic sealing gasket and applies elastic pressure toward the buffer throttling module to the drainage collar.

9. The staged pressure regulating dynamic seal structure for the liquid oxygen-methane turbopump according to claim 1, characterized in that, The main sealing rotating assembly, the buffer throttling module, and the end face compensation module are all provided with through holes through which the through screw can pass. One end of the through screw passes through the end face compensation module and the buffer throttling module in sequence and is then fixedly connected to the contact ring. The through screw is locked and fixed to the end face of the end face compensation module by a nut.

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