Low opening and closing pressure difference safety valve for ultrahigh-temperature high-flow fuel steam medium for spaceflight

Abstract

The invention discloses a low opening and closing pressure difference safety valve for ultrahigh-temperature large-flow fuel oil steam media for spaceflight, which comprises a shell, an inlet pipe nozzle, an inlet locking nut, a large-flow valve core, a low-rigidity spring, a spring seat, a locking nut and an adjusting nut are arranged in the shell from front to back, and a flexible graphite sealing ring is embedded at the tail end of the inlet pipe nozzle. The large-flow valve element slides in the shell in the axial direction, and the front end of the large-flow valve element is designed to be an arc-shaped conical surface matched with an arc chamfer. The two ends of the spring abut against the spring seat and the tail of the large-flow valve element respectively, a safety valve exhaust hole is formed in the front end of the shell, and the safety valve exhaust hole is communicated with an inlet of the inlet pipe nozzle when the large-flow valve element is in a retreating state. The pressure relief function of a 380 DEG C ultra-high-temperature fuel oil steam medium can be achieved, the ultralow opening and closing pressure difference of 0.005 MPa under the dynamic and static environments is achieved, and the exhaust stability is guaranteed under the vibration and impact environments.

Description

Technical Field

[0001] The invention relates to a fuel gas circuit power system for aerospace use, and in particular to a fuel vapor medium low opening and closing pressure difference safety valve under ultra-high temperature and large flow conditions. Background Art

[0002] In the aerospace fuel gas power system, the aviation / aerospace fuel in the fuel tank needs to be pushed by gas to supply the scramjet engine in the working state to provide power for the spacecraft. In this power system, various reasons will cause the system to generate 380℃ high-pressure and ultra-high temperature fuel vapor, resulting in abnormal operation of the system and failure to meet the power propulsion requirements of the aerospace vehicle. The safety valve is a common valve product in the oil / gas system. It is generally installed in parallel at the key position of the system. Its function is to keep the safety valve in a non-operating state when the oil / gas system is working normally, and the safety valve does not leak the working medium to the outside; when the pressure in the oil / gas system increases abnormally, the safety valve opens and discharges the abnormally high-pressure liquid / gas in the system to the outside of the system, so that the pressure in the system returns to normal, achieving the safety protection function of the oil / gas system; when the pressure in the system is relieved by the safety valve and returns to the normal value, the safety valve can return to the seat and close, and continue to achieve the back pressure function of sealing without exhausting. However, traditional gas safety valves cannot withstand the fuel vapor medium of 380°C. Such high temperature will cause the non-metallic rubber ring to melt. Moreover, there is no relative guide between the moving parts and the fixed parts of the traditional safety valve, or the guide is unreliable, and it cannot withstand the mechanical environment such as vibration and impact brought by the operation of the spacecraft. At the same time, traditional aerospace safety valves cannot meet the ultra-large flow index of 80L / s, and can only work within the range of 3L / s. Moreover, traditional safety valves cannot meet the low opening and closing pressure difference requirement of 0.005MPa. If it is sealed at 0.05MPa and opened at 0.055MPa, it is difficult to return to the seat and continue to seal at 0.05MPa.

[0003] At present, the gas safety pressure relief valve used in aerospace is mainly a plunger-type structure with a fixed throttling gap. The spring compresses the barrel plug and the rubber ring performs radial sealing on the side. Although this "plunger" type of safety valve can achieve exhaust pressure relief under the specified pressure, the gas passage area of ​​the safety valve is only the throttling gap on the plunger, and the throttling gap is small, and the maximum pressure relief flow can only reach 3L / s, which cannot meet the large-flow exhaust demand of 80L / s. In addition, this type of safety valve also adopts non-metallic rubber ring sealing. Under normal circumstances, the maximum temperature of the rubber ring can only withstand up to 250℃, and it cannot withstand the continued increase in ambient / medium temperature. If the temperature continues to rise, the non-metallic rubber ring will melt and lose its sealing function.

[0004] For example, a high-reliability overpressure control safety valve disclosed in CN 219121378 U is a flat-plate safety valve structure, which adopts a valve core inlaid with sealing material, and the inlet nozzle and the flat surface are sealed by spring force. However, the opening sensitive area of ​​this structure is only the size of the vent area in the inlet nozzle. Although the diameter of the valve core is larger than the diameter of the passage, only a smaller vent area can be used for calculation when calculating the flow rate, which cannot meet the actual working conditions of large flow rates. At the same time, the valve core of the safety valve of this structure adopts non-metallic rubber embedded in the entire sealing surface, that is, the sealing surface is in direct contact with the working medium. In the sealed state, it is directly in contact with the working medium. In the aerospace gas path power system, if the ultra-high temperature fuel vapor medium of 380°C directly contacts this part of the non-metallic rubber material, it will directly cause the non-metal to melt, the seal to fail, and the safety protection function to be lost; moreover, the structure of the valve core is a flat structure. At the upper limit of the flow rate, the medium flow has no guiding structure. When the exhaust pressure is released at a large flow rate, eddy currents are easily generated, making the pressure relief process unstable and causing abnormal consequences such as a sudden drop in flow rate. The shell opening method also does not have a medium guiding function; furthermore, the adjusting nut of this structure is large in size and heavy in weight. Compared with my invention, this adjustment structure is not suitable for the lightweight and miniaturization development requirements of aerospace valves. Finally, this type of safety valve cannot meet the requirements of low opening and closing pressure difference, because its sensitive area is the inner diameter area of ​​the inlet nozzle. After the safety valve is opened, the force-bearing area of ​​the entire safety valve becomes the area of ​​the valve core. As the area increases, the force on the valve core also increases. When the safety valve wants to return to its seat and close, it needs a larger spring force to return to its seat. As the spring force increases, the gas pressure that needs to be overcome must be smaller, so the closing pressure will be lower, which will lead to a large opening and closing pressure difference of the safety valve. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a low opening and closing pressure difference safety valve for aerospace ultra-high temperature and large flow fuel vapor medium, which can withstand ultra-high temperature fuel vapor medium and has a low opening and closing pressure difference, thereby ensuring the safety of the fuel power system of the spacecraft.

[0006] The technical solution adopted by the present invention is a low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use, comprising a housing, an inlet nozzle, an inlet locking nut, a large flow valve core, a low stiffness spring, a spring seat, a locking nut and an adjusting nut are installed in the housing from front to back, a flexible graphite sealing ring is inlaid at the tail end of the inlet nozzle, the tail end of the inlet nozzle is screwed into the housing and stuck at the housing limit block, the inlet locking nut locks the inlet nozzle to prevent loosening, the large flow valve core slides axially in the housing, the front end of the large flow valve core is a circular arc cone surface, and the top of the cone surface is a circular arc chamfer. The tail end of the large flow valve core is pressed by a spring, and the other end of the spring touches the spring seat. A raised spherical surface is provided on the end face of the rear of the spring seat, and the spherical surface is adapted to the inner cone surface of the adjusting nut to form a friction pair. A safety valve exhaust hole is provided at the front end of the housing, and the safety valve exhaust hole is connected to the inlet of the inlet nozzle when the large flow valve core is in the backward state. The large-flow valve core can move axially inside the housing. The spring is clamped between the spring seat and the large-flow valve core. After the adjusting nut is screwed into the rear end of the housing, it can be assembled through the assembly relationship of adjusting nut → spring seat → spring → large-flow valve core → flexible graphite sealing ring → inlet nozzle.

[0007] There are six exhaust holes of the safety valve, which are evenly distributed on the circumference of the shell. The angle between the axial direction of the exhaust holes of the safety valve and the opening direction of the valve core is 30°-60°, preferably 45°.

[0008] The beneficial effects of the present invention are that it can be applied to the safety protection of aerospace fuel power systems. Under conditions of large-scale vibration and impact of spacecraft, the valve core itself can be guided, which makes it insensitive to the mechanical environment and can perform normal pressure relief work; it can realize the pressure relief function of 380°C ultra-high temperature fuel vapor medium; it can exhaust and pressure relieve a large flow rate of 80L / s fuel vapor medium, and no eddy effect will be generated at the valve core during exhaust; during large-flow exhaust and pressure relief, the gas flow can be guided throughout the process, further increasing the exhaust flow rate; the safety valve can achieve an ultra-low opening and closing pressure difference of 0.005MPa under dynamic and static environments; the opening pressure of the safety valve can be adjusted within a certain range; and rapid exhaust can be achieved when the back pressure of the safety valve is large. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the structure of the present invention.

[0010] Figure 2 It is a schematic diagram of the pressure relief state.

[0011] Figure 3 Schematic diagram of the line seal structure between the large flow valve core and the flexible graphite seal ring of the inlet nozzle.

[0012] Figure 4 This is a schematic diagram of the large flow valve core structure.

[0013] Figure 5It is an exploded view of the assembly relationship of two parts of the present invention.

[0014] Markings in the figure are: 1-locking nut, 2-adjusting nut, 3-spring seat, 4-housing, 41-back pressure vent, 42-safety valve exhaust hole, 43-housing limiter, 5-low stiffness spring, 6-large flow valve core, 61-protrusion, 62-arc cone surface, 63-apex chamfer, 7-flexible graphite sealing ring, 8-inlet locking nut, 9-inlet nozzle. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings.

[0016] The low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use of the present invention includes three states of operation, namely, closed state → open pressure relief exhaust → return to seat and seal. The specific implementation of the whole process and the relationship between parts and assembly are introduced as follows:

[0017] like Figure 1 and Figure 5 As shown, the low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use of the present invention comprises: a locking nut 1, an adjusting nut 2, a spring seat 3, a housing 4, a low stiffness spring 5, a large flow valve core 6, a flexible graphite sealing ring 7, an inlet locking nut 8, and an inlet nozzle 9. The inlet of the inlet nozzle 9 adopts a threaded outer cone structure, and the internal diameter is φ25mm. The inlet end of the housing 4 is designed as an internal thread. The inlet nozzle 9 is connected to the housing 4 in such a way that the external thread is screwed into the internal thread of the housing 4. The tail section of the internal thread at the inlet end of the housing 4 has a threaded back cutter groove, as shown in FIG. Figure 1 As shown, the position of the thread backing groove is also a shell limit platform 43. When the inlet nozzle 9 is continuously screwed into the shell 4, the shell limit platform 43 is used to ensure the limitation of the inlet nozzle 9. At the same time, the "flexible graphite sealing ring" groove at the tail end of the inlet nozzle 9 exceeds the shell limit platform 43, which can ensure the contact seal with the large flow valve core 6. After the inlet nozzle 9 is screwed into the shell 4 and the limitation is completed, the inlet locking nut 8 is screwed into the inlet nozzle 9 until it contacts the shell 4, and a torque is applied to ensure that the thread between the inlet nozzle 9 and the shell 4 is prevented from loosening.

[0018] Six oblique safety valve exhaust holes 42 are arranged on the front circumference of the housing 4, with a diameter of 10 mm, at an angle of 45° to the horizontal direction, and evenly distributed, such as Figure 2 , Figure 1When the safety valve is assembled into the system, when the high-temperature fuel vapor pressure in the system does not reach 0.05MPa, the large-flow valve core 6 is pressed against the flexible graphite sealing ring 7 embedded in the inlet nozzle 9 by the spring force of the low-rigidity spring 5 to achieve a sealing effect, and the high-temperature fuel vapor will not be discharged outside the system through the safety valve. When the high-temperature fuel vapor pressure in the system reaches or exceeds 0.05MPa, the large-flow valve core 6 is subjected to a greater air pressure, which overcomes the preload value of the low-rigidity valve core 5 and generates displacement, as shown in FIG. Figure 2 As shown, the high-temperature and high-pressure fuel vapor in the system will be guided by the large-flow valve core 6 and enter the side exhaust inclined hole of the safety valve housing 4. This is also a gas exhaust guide, which allows the fuel vapor medium to complete safe pressure relief without changing the flow direction, further ensuring the exhaust flow rate.

[0019] The front end of the large flow valve core 6 is designed with a "circular arc conical surface" for the part in contact with the working medium. The arc conical surface 62 is R20 in size, and the top of the conical surface is a vertex chamfer 63, which is chamfered with R1 for smooth transition. The design form of the arc conical surface and the chamfer, plus the large-diameter safety valve exhaust hole 42 on the shell, can ensure that the large flow valve core 6 can achieve the "exhaust guide" of the large flow working medium when it is opened for pressure relief. Figure 2 , Figure 4 As shown, this structure can achieve large flow pressure relief state without generating vortex in the valve, thus ensuring the pressure relief flow and making the exhaust pressure relief smoother.

[0020] The sealing form of the large flow valve core is a flat edge arc line sealing structure, such as Figure 3 As shown, a circle of arc-shaped protrusions 61 are designed on the edge of the end face of the large flow valve core 6, and the protrusions 61 are in contact and pressed with the flexible graphite sealing ring 7 embedded in the inlet nozzle 9 to achieve a stable and reliable "line seal". The material performance of the flexible graphite sealing ring is very stable, and it will not undergo chemical changes in a fuel vapor environment at 380°C, which can meet the sealing requirements.

[0021] In addition, if Figure 1 As shown, the large flow valve core 6 and the housing 4 are ground together, and the gap is about 0.01mm, so as to ensure that the large flow valve core 6 can move smoothly in the housing 4 without eccentricity, jamming and other problems. Figure 1 As shown, a guide section is designed between the large flow valve core 6 and the housing 4, the guide section is lengthened, and the ratio of the guide section to the valve core diameter is greater than 1, so as to ensure that the safety valve can still reliably open the valve core and exhaust and release pressure under the vibration and impact environment on the spacecraft.

[0022] A low-rigidity spring 5 is placed inside the large-flow valve core 6. The spring is limited by a hollow cylindrical cylinder inside the large-flow valve core 6. The other side of the low-rigidity spring 5 contacts the spring seat 3. A hollow cylindrical cylinder is also provided inside the spring seat 3 to limit the other side of the low-rigidity spring 5. The limits on both sides ensure that the spring does not suffer from overall bending, offset and other faults in the working state. The other side of the spring seat 3 is a spherical surface. The spherical surface contacts and cooperates with the inner conical surface of the adjusting nut 2 during assembly to form a spherical friction pair, such as Figure 1 As shown, during the assembly and debugging process of the safety valve, the adjusting nut 2 needs to be gradually screwed into the tail end internal thread of the housing 4. In order to ensure that the low-rigidity spring 5 will not drive the spring to rotate due to the circumferential rotation of the adjusting nut 2 during the assembly and debugging process, the spherical friction pair is designed. During the screwing-in process of the adjusting nut 2, the adjusting nut 2 moves relative to the spring seat 3 through the friction pair, while the spring seat 3 and the low-rigidity spring 5 are relatively static. The low-rigidity spring only completes the pressing and will not produce circumferential movement. When the debugging of the safety valve is completed, the locking nut 1 is screwed into the adjusting nut 2 until it contacts the valve body 4, and a tightening torque is applied to ensure that the adjusting nut 2 is prevented from loosening.

[0023] Six circumferentially evenly distributed back-pressure vents 41 with a diameter of 3 are provided on the side of the rear end of the shell 4 to ensure that the air pressure in the spring chamber of the large-flow valve core 6 in the safety valve cannot be discharged in the process of overcoming the spring force displacement, thereby generating "back pressure" and destroying the force balance of the large-flow valve core 6 in the working state. Moreover, in order to reduce the opening and closing pressure difference of the safety valve and achieve the opening and closing pressure difference of 0.005MPa, the large-flow valve core 6 and the shell 4 are assembled in a matching grinding manner, and no sealing rubber ring is arranged between the two. During the opening process of the safety valve, some decompressed fuel vapor may enter the spring chamber, which will also cause the "back pressure" to increase. The six evenly distributed back-pressure vents 41 further ensure the low opening and closing pressure difference of 0.005MPa of the safety valve.

[0024] When the safety valve has released pressure, the fuel vapor pressure in the system decreases, and the pressure acting on the large flow valve core 6 also decreases, which cannot overcome the compressed spring force. Then the low-rigidity spring 5 drives the large flow valve core to overcome the air pressure and return to its seat, and continues to press the large flow valve core 6 against the flexible graphite sealing ring 7 to complete the return seal.

[0025] In summary, a low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use can achieve three working states: closed state → open pressure relief exhaust → return to seat and seal, thus ensuring the safety of aerospace fuel power system.

[0026] In order to achieve the pressure relief of 80L / s of 380℃ high-temperature fuel steam and meet the aerospace valve with the indicators of 0.05MPa sealing and 0.055MPa full opening, the best implementation method is that the diameter of the large-flow valve core is 50mm. Because in order to meet the pressure relief of 80L / s high-temperature fuel steam flow, the large-flow valve core and the sealing surface need to be opened at least 3mm. According to 0.05MPa sealing and 0.055MPa full opening, that is, the opening and closing pressure difference is 0.005MPa, the product of the opening and closing pressure difference and the large-flow valve core can be calculated that the force on the large-flow valve core under the opening and closing pressure difference is 9.8N. If If you want to meet the minimum opening height of 3mm, the spring stiffness should be designed to be relatively low, less than 9.8N / 3mm or 3.26N / mm. For the design of the spring, the spring middle diameter is 35mm, the wire diameter is 3.5mm, the effective number of turns is 15, the pitch is 8mm, and the wire is 60Si2MnA silicon-manganese spring steel wire. After calculation, the spring stiffness is 2.3N / mm, which is less than the calculated stiffness of 3.26N / mm. This shows that when it is opened at 0.055MPa, the displacement of the large flow valve core can exceed 3mm, meeting the 80L / s large flow fuel vapor pressure relief index. When sealing, the force area of ​​the large flow valve core is φ50mm, and when opening, due to the plunger-type large valve port diameter structure, the force area is still φ50mm. The force of the large flow valve core when opening and closing is basically unchanged, which ensures the low opening and closing pressure difference characteristics of the safety valve product, and does not require a larger spring force / smaller air flow pressure for sealing and returning due to changes in the force area.

[0027] To sum up, the low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use of the present invention can be opened to release pressure when a large amount of fuel vapor with abnormal pressure appears in the engine, ensuring that a large amount of ultra-high temperature fuel vapor can be quickly exhausted to the outside, thereby realizing the safety protection of the gas path power. When the pressure in the system returns to normal, it can quickly return to its seat and close, ensuring that the gas volume and fuel in the gas path system will not be lost too much, thereby improving the working efficiency of the entire aerospace gas path power system. It is suitable for the safety protection of aerospace fuel power systems. Under the conditions of large-scale vibration and impact of spacecraft, it can be guided by the valve core itself, is insensitive to the mechanical environment, and can perform normal pressure relief work; it can realize the pressure relief function of 380℃ ultra-high temperature fuel vapor medium; it can exhaust and pressure relieve the large flow rate of 80L / s fuel vapor medium, and no eddy effect will be generated at the valve core during exhaust; during large flow exhaust pressure relief, the whole process of gas flow can be guided to further increase the exhaust flow rate; through the design of low-rigidity springs and large-flow valve cores, 0.05MPa sealing, 0.055MPa safety valve fully open (380℃ fuel vapor flow rate reaches 80L / s), and 0.005MPa opening and closing pressure difference can be achieved; the opening pressure of the safety valve can be adjusted within a certain range; rapid exhaust when the back pressure of the safety valve is large can be achieved. The present invention is superior to the prior art in terms of the volume and weight of the entire valve body, large flow adaptability, adaptability to high-temperature steam media, selection of non-metallic materials, sealing method, valve core structure, exhaust and pressure relief hole angle of the safety valve housing, and comparison of the opening and closing pressure difference of the safety valve.

Claims

1. Low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel steam medium for aerospace use, characterized by: The utility model comprises a shell, in which an inlet nozzle, an inlet locking nut, a large-flow valve core, a low-rigidity spring, a spring seat, a locking nut and an adjusting nut are installed from front to back. A flexible graphite sealing ring is inlaid at the tail end of the inlet nozzle. The tail end of the inlet nozzle is screwed into the shell and stuck at the limit block of the shell. The inlet locking nut locks the inlet nozzle to prevent loosening. The large-flow valve core slides axially in the shell. The front end of the large-flow valve core is an arc-shaped conical surface, and the top end of the conical surface is an arc chamfer. The tail end of the large-flow valve core is pressed by a spring, and the other end of the spring touches the spring seat. A raised spherical surface is provided on the end face of the rear part of the spring seat, and the spherical surface is matched with the inner conical surface of the adjusting nut to form a friction pair. A safety valve exhaust hole is provided at the front end of the shell. When the large-flow valve core is in the retreated state, the safety valve exhaust hole is connected to the inlet of the inlet nozzle.

2. The low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use as claimed in claim 1 is characterized by: The safety valve has six exhaust holes evenly distributed on the circumference of the shell.

3. The low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use as claimed in claim 2 is characterized by: The angle between the axial direction of the exhaust hole of the safety valve and the opening direction of the valve core is 30°-60°.

4. The low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use as claimed in claim 1 is characterized by: A back pressure vent hole is provided at a position of the shell corresponding to the spring cavity.

5. The low opening and closing pressure difference safety valve for ultra-high temperature and large flow fuel vapor medium for aerospace use as claimed in claim 1 is characterized by: The large flow valve core is designed with a guide section matched with the housing, and the ratio of the guide section to the valve core diameter is greater than 1.

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