Closed-loop control high-precision nitrous oxide flow regulating valve and control method

Abstract

The invention provides a closed-loop control high-precision nitrous oxide flow regulating valve and a control method, belongs to the technical field of spaceflight propulsion, mainly meets the flow control application requirement of a liquid rocket engine, and improves the accuracy of nitrous oxide flow regulation. The movable pintle rod is adopted, the throat circulation area can be adjusted, and the wide flow range can be adjusted; a direct driving motor and a high-precision screw rod are adopted, so that high-precision movement of the pintle rod can be ensured; a high-precision displacement sensor is used for feeding back the position to realize the closed-loop control of the position movement of the pintle rod, and the stroke error and the gap error are controlled within a certain range; nitrous oxide temperature and pressure information is detected and collected at an inlet, a controller controls a motor to conduct adjustment, and real-time flow adjustment and control are achieved according to real-time physical property parameters of nitrous oxide. The flow control device is good in flow control consistency, high in precision and particularly suitable for high-saturated vapor pressure liquid such as ammonia, carbon dioxide, nitrogen dioxide, sulfur dioxide and formaldehyde.

Description

Technical Field

[0001] This invention belongs to the field of aerospace propulsion technology, specifically relating to a closed-loop control high-precision nitrous oxide flow regulating valve and control method. Background Technology

[0002] Nitrous oxide is a green and non-toxic propellant with advantages such as high saturated vapor pressure, stable properties, catalytic decomposition, and low cost. It can be used in monopropellant and bipropellant propulsion systems and has great application potential in attitude and orbit control engines. However, in actual use, as the ambient temperature increases, the saturated vapor pressure of nitrous oxide increases significantly, while the liquid phase density decreases significantly. Figure 1 As shown, according to the cavitation venturi flow formula, the nitrous oxide supply flow rate will be significantly reduced, thus affecting the stable operation of the engine. Furthermore, in application, multiple replacements of the fixed cavitation tube (flow control element) are required for debugging to achieve the target flow rate, leading to reduced experimental efficiency and increased testing costs. However, when the engine is performing a space mission, it is impossible to replace the fixed cavitation tube, and existing control valves cannot meet the application requirements. Therefore, it is necessary to design a closed-loop adjustable cavitation tube that can precisely adjust the nitrous oxide flow rate at different temperatures to adapt to space missions with varying temperatures, while simultaneously improving the efficiency of ground testing and debugging. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, meet the flow control requirements of liquid rocket engines at different temperatures, and improve the accuracy of nitrous oxide flow rate regulation at different temperatures, this invention provides a closed-loop control high-precision nitrous oxide flow rate regulating valve and control method.

[0004] The technical solution adopted by the present invention to solve its technical problem is a closed-loop control high-precision nitrous oxide flow regulating valve, including a needle rod 4, a valve body 5, a lead screw transmission part, a drive motor part, and a controller 24; The drive motor unit includes a direct drive motor 20, a motor protective cover 11, and a motor base plate 12; The motor protective cover 11 includes a lead screw protective section, a motor protective section, and a protective base; the motor protective section and the lead screw protective section are arranged sequentially from bottom to top on the top surface of the protective base; a base through hole is provided in the center of the protective base; a base through hole is provided in the center of the motor base plate 12; both the motor protective section and the lead screw protective section are thin-walled barrel-shaped; the motor protective section, the lead screw protective section, and the base through hole are all coaxial with the base through hole; a direct drive motor 20 is nested inside the motor protective section; the motor base plate 12 is fixedly installed on the bottom surface of the protective base; The valve body 5 is a column; a cavity is provided axially between the two end faces of the valve body 5; a coaxial straight section, a throat section, and an expansion section are arranged sequentially in the cavity; the throat section includes a contraction section and a transition section arranged sequentially; the transition section is smoothly connected to the expansion section; the contraction section is smoothly connected to the straight section. A liquid outlet is provided on one end face of the valve body 5; the liquid outlet is a through hole; the liquid outlet is connected to the outlet of the expansion section; A first countersunk hole is provided on the other end face of the valve body 5; an end cap 8 is provided in the first countersunk hole; the first countersunk hole is connected to the inlet of the straight section; The inner wall of the straight section is provided with a radial liquid inlet through hole; a liquid inlet pipe is fixedly installed in the liquid inlet through hole; a temperature sensor 2 and a pressure sensor 3 are respectively installed on the inner wall of the liquid inlet pipe; The end cap 8 has an end cap hole at its center; the end cap hole is a through hole; the end cap hole and the first countersunk hole are both coaxial with the cavity; The needle rod includes a plug and a needle rod arranged coaxially; the plug is a cone; the bottom surface of the plug is fixedly connected to one end face of the needle rod; the other end face of the needle rod is fixedly connected to the lead screw drive part; the plug is coaxially nested in the cavity of the valve body; The pin slide is nested inside the end cap hole of the end cap; The lead screw transmission unit is nested and coaxially fixed on the shaft of the direct drive motor; the lead screw transmission unit converts the rotational motion of the direct drive motor into the linear motion of the lead screw transmission unit, thereby driving the pin slide rod to move linearly. The controller 24 is connected to the direct drive motor 20, the high-precision laser displacement sensor 10, the temperature sensor 2, and the pressure sensor 3, respectively. A dynamic position monitoring plate 9 is installed on the needle bolt slide bar; a high-precision laser displacement sensor 10 is installed on the outer wall of the motor protection section; and the controller 24 is connected to the high-precision laser displacement sensor 10.

[0005] Furthermore, the cone angle of the plug is... The range of the plug cone angle is .

[0006] Furthermore, a sealing bushing 7 is provided at one end of the straight section near the end cover 8; The sealing bushing 7 includes a sealing bushing base and a shaft sealing sleeve; both the sealing bushing base and the shaft sealing sleeve are hollow cylinders; the shaft sealing sleeve is coaxially disposed on the end face of the sealing bushing base; the inner diameter of the sealing bushing base is smaller than the inner diameter of the shaft sealing sleeve; the outer diameter of the shaft sealing sleeve is smaller than the outer diameter of the sealing bushing base; the outer diameter of the shaft sealing sleeve is the same as the inner diameter of the straight section. The outer wall of the shaft seal sleeve is provided with a first annular groove; a shaft seal ring is provided in the annular groove; The inner wall of the sealing bushing base is provided with a second annular groove; a base sealing ring is provided in the second annular groove; Both the bushing seal and the base seal are O-rings, which effectively improve the valve's sealing performance.

[0007] An end cap groove is provided on the outer wall of the end cap hole; the end cap groove is coaxial with the valve body 5; a buffer rubber pad is provided inside the end cap groove.

[0008] Furthermore, the lead screw drive includes a pin connection structure and a transmission structure; The pin-bolt connection structure includes a bushing 25 and a fisheye connector 16; the fisheye connector is a rod end spherical bearing; the bushing 25 is a cylinder; the top surface of the bushing 25 has a first blind hole along the axial direction at its center; the first blind hole is fixedly connected to the pin-bolt slide rod by a thread; the outer wall of the bushing 25 has a radial fisheye groove; the bearing head of the fisheye connector 16 is disposed in the fisheye groove; the outer wall of the bushing 25 has a fixing through hole perpendicular to the axis of the bushing 25; a first bolt is disposed in the fixing through hole; after the bearing head of the fisheye connector 16 is disposed in the fisheye groove, the first bolt limits and fixes the fisheye connector to the bushing 25 by passing through the mounting hole of the bearing head of the fisheye connector; The transmission structure includes a lead screw 17, a lead screw nut 18, a bushing 13, an adapter plate 19, an anti-rollover shaft 21, a first slider 22, and a second slider 22'. The lead screw nut 18 includes a stud and a stud flange; the stud is a hollow cylinder, and the inner wall of the stud is provided with internal threads; the outer wall of the lead screw 17 is provided with external threads; the diameter of the inner wall of the stud is the same as the diameter of the lead screw; the stud flange is fixedly installed on the outer wall of the stud; the end face of the stud flange is provided with several stud fixing holes; The adapter plate 19 is an annular flange; several adapter plate fixing holes are respectively provided on the end face of the adapter plate 19 along the outer circumference and the inner circumference; the adapter plate 19 is fixedly connected to the shaft of the direct drive motor by bolts through the adapter plate fixing holes on the outer circumference of the adapter plate 19; the adapter plate 19 is fixedly connected to the stud flange by bolts through the adapter plate fixing holes on the inner circumference of the adapter plate 19; the adapter plate 19 is used to connect the lead screw nut 18 and the direct drive motor 20, and transmit the torque of the motor to the lead screw 17; The anti-roll shaft 21 is a hollow cylinder; the outer wall of the anti-roll shaft 21 is respectively provided with a first slider groove and a second slider groove; a first slider 22 is fixedly installed in the first slider groove; a second slider 22' is fixedly installed in the second slider groove; the anti-roll shaft 21 ensures that the lead screw 17 only moves in a linear motion and does not rotate relative to the direct drive motor; The bushing 13 includes a bushing column and a bushing flange; the bushing column is a hollow cylinder; the bushing flange is fixedly installed on the outer wall of the bushing column; a plurality of bushing flange bolt holes are provided on the end face of the bushing flange; the inner wall of the bushing column is provided with a first groove and a second groove along the axial direction. The inner diameter of the anti-rollover shaft 21 is the same as the diameter of the lead screw 17; A displacement blind hole is provided on one end face of the lead screw 17; an anti-rollover shaft 21 is provided on the outer wall of the other end face of the lead screw 17; a thread is provided in the displacement blind hole; the displacement blind hole is fixedly connected to the threaded rod end of the fisheye connector by the thread. The lead screw 17 is nested from left to right with a motor protective cover 11, a lead screw nut 18, an adapter plate 19, a direct drive motor 20, a motor base plate 12, an anti-rollover shaft 21, and a shaft sleeve 13. The lead screw nut 18 and lead screw 17 are connected by threads to convert rotational motion into linear motion; the lead screw 17 and anti-roll shaft 21 are clearance-fitted; the adapter plate 19 is fixedly connected to the stud flange of the lead screw nut 18 by screws; the stud flange of the lead screw nut 18 is fixedly connected to the shaft of the direct drive motor 20 by screws; the anti-roll shaft 21 is nested in the bushing 13, and the end face of the anti-roll shaft 21 is flush with the end face of the lead screw 17; the bushing 13 and the anti-roll shaft 21 are clearance-fitted; the first slider of the anti-roll shaft 21 is embedded in the first groove; the second slider of the anti-roll shaft 21 is embedded in the second groove; the sleeve flange of the bushing 13 is fixedly connected to the motor base plate 12 by bolts; the end face of the bushing 13 away from the motor base plate 12 is provided with a bushing cover 14.

[0009] Furthermore, a photoelectric detection plate is fixedly installed on the end face of the lead screw 17 that is flush with the anti-rollover shaft 21; a photoelectric detector 15 is installed on the inner wall of the bushing cover 14; and the photoelectric detector 15 is connected to the controller 24.

[0010] The control method for the high-precision nitrous oxide flow regulating valve using closed-loop control includes the following steps: Step S0: Initialization. When the plug is fully in contact with the transition section of the throat, the flow area corresponding to the throat is zero. At this time, when the plug stroke is zero, the position of the dynamic position detection plate is zero. Step S1: The controller collects pressure data from the pressure sensor and temperature data from the temperature sensor in real time, and calculates the inlet liquid density; based on the inlet liquid density, the target flow area corresponding to the target nitrous oxide flow rate is calculated using the liquid cavitation venturi flow rate formula; the target nitrous oxide flow rate is a known quantity. Step S2: Calculate the blockage travel distance based on the target flow area; Step S3: The controller drives the high-precision laser displacement sensor to detect the real-time position of the dynamic position detection plate; When the real-time position of the dynamic position detection plate is greater than the end cap stroke, the controller drives the needle rod to move closer to the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. When the real-time position of the dynamic position detection plate is less than or equal to the end cap stroke, the controller drives the needle rod to move further away from the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. Step S4: When the plug moves, the controller simultaneously drives the high-precision laser displacement sensor to detect the real-time position of the dynamic position detection plate. When the absolute value of the difference between the real-time position of the dynamic position detection plate and the stroke of the plug is less than the displacement threshold, it is considered that the plug has moved to the target position corresponding to the target flow area. Repeat steps S1-S4 to achieve closed-loop control of the high-precision nitrous oxide flow regulating valve.

[0011] Furthermore, the step of calculating the target flow area corresponding to the target flow rate of nitrous oxide using the liquid cavitation Venturi flow formula is as follows: The formula for the flow rate of a liquid cavitation venturi tube is: ; in, The target flow rate for nitrous oxide; For flow coefficient; For the throat circulation area; To collect pressure data from the pressure sensor in real time; This is the saturated vapor pressure of the liquid under local temperature conditions; Given the inlet liquid density; calculate the flow area at the throat. Throat circulation area This refers to the target flow area corresponding to the target flow rate of nitrous oxide.

[0012] Furthermore, the step of calculating the plug stroke is as follows: (1) in, Target circulation area; The length of the plug. For the end of the journey, This refers to the length of the transition segment of the larynx. The diameter of the throat inlet. The diameter of the throat exit. The cone angle of the plug; in, ; The relationship between the plug length and the throat inlet diameter is as follows: ; Will and Substituting into equation (1), the target circulation area is obtained as follows:

[0013] Take the length of the transition segment of the larynx ,but: (2) The stroke of the plug can be obtained according to formula (2).

[0014] This invention utilizes the cavitation principle, remaining unaffected by downstream pressure changes and ensuring a stable flow supply. A movable needle rod allows for throat area adjustment, enabling a wide range of flow rate adjustment. A direct-drive motor and high-precision lead screw ensure high-precision needle rod movement. A high-precision displacement sensor provides position feedback for closed-loop control of the needle rod's position, keeping stroke and clearance errors within a certain range. Temperature and pressure information of nitrous oxide are detected and collected at the inlet, and the controller adjusts the motor accordingly, achieving real-time flow rate regulation based on the real-time physical properties of nitrous oxide. A closed-loop control method coupling pressure and temperature improves the accuracy of flow rate regulation. The invention employs a hollow direct-drive motor configuration with a bushing, housing the lead screw inside the motor for a more compact design and reduced motor size. Due to its closed-loop control method, this invention offers advantages such as high control accuracy, a wide flow rate adjustment range, and fast adjustment speed, making it suitable as a flow control valve for variable-thrust rocket engines. This invention is also applicable to high saturated vapor pressure liquids such as ammonia, carbon dioxide, nitrogen dioxide, sulfur dioxide, and formaldehyde, and is equally applicable to ordinary liquids such as kerosene and water. Attached Figure Description

[0015] Figure 1 This is a schematic diagram showing the changes in saturated vapor pressure and density of nitrous oxide with temperature; Figure 2 This is an isometric view of the present invention; Figure 3 This is a longitudinal cross-sectional view of the present invention; Figure 4 This is a cross-sectional view of the present invention; Figure 5 This is an exploded view of the valve components of the present invention; Figure 6 This is an exploded view of the connecting parts between the drive motor and the pin rod of the present invention; Figure 7 This is a schematic diagram of the anti-rollover shaft installation of the present invention; Figure 8 This is a schematic diagram of the connection between the lead screw and the lead screw nut of the present invention; Figure 9This is a schematic diagram of the fisheye connection of the present invention; Figure 10 This is a cross-sectional view of the installation of the bushing and the anti-rollover shaft of the present invention; Figure 11 This is a schematic diagram of the sealing of the sealing bushing of the present invention; Figure 12 This is a schematic diagram of the sliding groove of the bushing of the present invention; Figure 13 This is a schematic diagram of the fixing of the bushing and the anti-rollover shaft of the present invention; Figure 14 This is a schematic diagram of the installation of the photoelectric detector of the present invention; Figure 15 This is a schematic diagram of the structure of the sealing bushing of the present invention; Figure 16 This is a schematic diagram of the end cap structure of the present invention; Figure 17 This is a graph showing the experimental data relating the flow rate and needle cone stroke of this invention; Figure 18 This is a schematic diagram illustrating the principle of calculating the throat flow area in this invention; Figure 19 This is the theoretical calculation relationship between the stroke and flow rate of the flow regulating valve of the present invention; 1-Threaded connector inlet; 2-Temperature sensor; 3-Pressure sensor; 4-Needle rod; 5-Valve body; 6-Threaded connector outlet; 7-Sealing bushing; 8-End cover; 9-Dynamic position monitoring plate; 10-High-precision laser position sensor; 11-Motor protective cover; 12-Motor base plate; 13-Bushing sleeve; 13'-First slide groove; 14-Bushing sleeve cover; 15-Photoelectric detector; 16-Fisheye connector; 17-Lead screw; 18-Lead screw nut; 19-Adapter plate; 20-Direct drive motor; 21-Anti-rollover shaft; 22-First slider; 22'-Second slider; 23-Set bolt; 24-Controller; 25-Bushing sleeve. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] A closed-loop control high-precision nitrous oxide flow regulating valve includes a needle rod 4, a valve body 5, a lead screw transmission part, a drive motor part, and a controller 24; like Figures 2 to 16 As shown, the drive motor unit includes a direct drive motor 20, a motor protective cover 11, and a motor base plate 12; The motor protective cover 11 includes a lead screw protective section, a motor protective section, and a protective base; the motor protective section and the lead screw protective section are arranged sequentially from bottom to top on the top surface of the protective base; a base through hole is provided in the center of the protective base; a base through hole is provided in the center of the motor base plate 12; both the motor protective section and the lead screw protective section are thin-walled barrel-shaped; the motor protective section, the lead screw protective section, and the base through hole are all coaxial with the base through hole; a direct drive motor 20 is nested inside the motor protective section; the motor base plate 12 is fixedly installed on the bottom surface of the protective base; The valve body 5 is a column; a cavity is provided axially between the two end faces of the valve body 5; a coaxial straight section, a throat section, and an expansion section are arranged sequentially in the cavity; the throat section includes a contraction section and a transition section arranged sequentially; the transition section is smoothly connected to the expansion section; the contraction section is smoothly connected to the straight section. A liquid outlet is provided on one end face of the valve body 5; the liquid outlet is a through hole; the liquid outlet is connected to the outlet of the expansion section; A first countersunk hole is provided on the other end face of the valve body 5; an end cap 8 is provided in the first countersunk hole; the first countersunk hole is connected to the inlet of the straight section; The inner wall of the straight section is provided with a radial liquid inlet through hole; a liquid inlet pipe is fixedly installed in the liquid inlet through hole; a temperature sensor 2 and a pressure sensor 3 are respectively installed on the inner wall of the liquid inlet pipe; The end cap 8 has an end cap hole at its center; the end cap hole is a through hole; the end cap hole and the first countersunk hole are both coaxial with the cavity; The needle rod 4 includes a plug and a needle slide rod arranged coaxially; the plug is a cone; the bottom surface of the plug is fixedly connected to one end face of the needle slide rod; the plug is coaxially nested in the cavity of the valve body 5; The cone angle of the plug is The range of the plug cone angle is The smaller the cone angle of the plug, the higher the control precision. The other end face of the pin slide rod passes through the end cap hole and is fixedly connected to the lead screw drive part; The lead screw transmission unit is nested and coaxially fixed on the shaft of the direct drive motor; the lead screw transmission unit converts the rotational motion of the direct drive motor into the linear motion of the lead screw transmission unit, thereby driving the pin slide rod to move linearly. The controller 24 is connected to the direct drive motor 20, the high-precision laser displacement sensor 10, the temperature sensor 2, and the pressure sensor 3, respectively. A dynamic position monitoring plate 9 is installed on the needle bolt slide rod; a high-precision laser displacement sensor 10 is installed on the outer wall of the motor protection section; the controller 24 is connected to the high-precision laser displacement sensor 10. The dynamic position monitoring plate 9 and the high-precision laser displacement sensor 10 are used together to detect the actual position of the needle bolt rod. If the position information differs from the set position parameters, the direct drive motor is activated to move until the error is less than the requirement, thus completing the position information detection and feedback, and realizing the control of the error.

[0018] A sealing bushing 7 is provided at one end of the straight section near the end cover 8; The sealing bushing 7 includes a sealing bushing base and a shaft sealing sleeve; both the sealing bushing base and the shaft sealing sleeve are hollow cylinders; the shaft sealing sleeve is coaxially disposed on the end face of the sealing bushing base; the inner diameter of the sealing bushing base is smaller than the inner diameter of the shaft sealing sleeve; the outer diameter of the shaft sealing sleeve is smaller than the outer diameter of the sealing bushing base; the outer diameter of the shaft sealing sleeve is the same as the inner diameter of the straight section. The outer wall of the shaft seal sleeve is provided with a first annular groove; a shaft seal ring is provided in the annular groove; The inner wall of the sealing bushing base is provided with a second annular groove; a base sealing ring is provided in the second annular groove; Both the bushing seal and the base seal are O-rings, which effectively improve the valve's sealing performance.

[0019] An end cap groove is provided on the outer wall of the end cap hole; the end cap groove is coaxial with the valve body 5; a buffer rubber pad is provided inside the end cap groove.

[0020] The lead screw transmission unit includes a pin connection structure and a transmission structure; The pin-bolt connection structure includes a bushing 25 and a fisheye connector 16; the fisheye connector is a rod end spherical bearing; the bushing 25 is a cylinder; the top surface of the bushing 25 has a first blind hole along the axial direction at its center; the first blind hole is fixedly connected to the pin-bolt slide rod by a thread; the outer wall of the bushing 25 has a radial fisheye groove; the bearing head of the fisheye connector 16 is disposed in the fisheye groove; the outer wall of the bushing 25 has a fixing through hole perpendicular to the axis of the bushing 25; a first bolt is disposed in the fixing through hole; after the bearing head of the fisheye connector 16 is disposed in the fisheye groove, the first bolt limits and fixes the fisheye connector to the bushing 25 by passing through the mounting hole of the bearing head of the fisheye connector; The pin bolt 4 and the lead screw 17 need to maintain a straight line during movement. However, due to the machining process, there will still be a certain deviation in their concentricity. The use of a fisheye connector can adjust the machining deviation and ensure straight movement. The pin bolt 4, bushing 25, fisheye connector 16 and lead screw 17 are rigidly connected and connected with anti-loosening nuts to eliminate the gap error at the connection. The transmission structure includes a lead screw 17, a lead screw nut 18, a bushing 13, an adapter plate 19, an anti-rollover shaft 21, a first slider 22, and a second slider 22'. The lead screw nut 18 includes a stud and a stud flange; the stud is a hollow cylinder, and the inner wall of the stud is provided with internal threads; the outer wall of the lead screw 17 is provided with external threads; the diameter of the inner wall of the stud is the same as the diameter of the lead screw; the stud flange is fixedly installed on the outer wall of the stud; the end face of the stud flange is provided with several stud fixing holes; The adapter plate 19 is an annular flange; several adapter plate fixing holes are respectively provided on the end face of the adapter plate 19 along the outer circumference and the inner circumference; the adapter plate 19 is fixedly connected to the shaft of the direct drive motor by bolts through the adapter plate fixing holes on the outer circumference of the adapter plate 19; the adapter plate 19 is fixedly connected to the stud flange by bolts through the adapter plate fixing holes on the inner circumference of the adapter plate 19; the adapter plate 19 is used to connect the lead screw nut 18 and the direct drive motor 20, and transmit the torque of the motor to the lead screw 17; The anti-roll shaft 21 is a hollow cylinder; the outer wall of the anti-roll shaft 21 is respectively provided with a first slider groove and a second slider groove; a first slider 22 is fixedly installed in the first slider groove; a second slider 22' is fixedly installed in the second slider groove; the anti-roll shaft 21 ensures that the lead screw 17 only moves in a linear motion and does not rotate relative to the direct drive motor; The bushing 13 includes a bushing column and a bushing flange; the bushing column is a hollow cylinder; the bushing flange is fixedly installed on the outer wall of the bushing column; a plurality of bushing flange bolt holes are provided on the end face of the bushing flange; the inner wall of the bushing column is provided with a first groove and a second groove along the axial direction. The inner diameter of the anti-rollover shaft 21 is the same as the diameter of the tail end of the lead screw 17; A displacement blind hole is provided on one end face of the lead screw 17; an anti-rollover shaft 21 is provided on the outer wall of the other end face of the lead screw 17; a thread is provided in the displacement blind hole; the displacement blind hole is fixedly connected to the threaded rod end of the fisheye connector by the thread. The lead screw 17 is nested from left to right with a motor protective cover 11, a lead screw nut 18, an adapter plate 19, a direct drive motor 20, a motor base plate 12, an anti-rollover shaft 21, and a shaft sleeve 13. The lead screw nut 18 and lead screw 17 are connected by threads to convert rotational motion into linear motion; the lead screw 17 and anti-roll shaft 21 are clearance-fitted; the adapter plate 19 is fixedly connected to the stud flange of the lead screw nut 18 by screws; the stud flange of the lead screw nut 18 is fixedly connected to the shaft of the direct drive motor 20 by screws; the anti-roll shaft 21 is nested inside the bushing 13, and the end face of the anti-roll shaft 21 is flush with the end face of the lead screw 17; the bushing 13 and the anti-roll shaft 21 are clearance-fitted; the first slider of the anti-roll shaft 21 is embedded in the first groove; the second slider of the anti-roll shaft 21 is embedded in the second groove; the sleeve flange of the bushing 13 is fixedly connected to the motor base plate 12 by bolts; the end face of the bushing 13 away from the motor base plate 12 is provided with a bushing cover 14; A photoelectric detection plate is fixedly installed on the end face of the lead screw 17 that is flush with the anti-rollover shaft 21; a photoelectric detector 15 is installed on the inner wall of the bushing cover 14; the photoelectric detector 15 is connected to the controller 24; The photoelectric detection board and photoelectric detector 15 are used for emergency stop to prevent the lead screw from moving beyond its range and damaging the motor. When the photoelectric detector 15 detects the photoelectric detection board, it will trigger the beam of the photoelectric detector. When the beam of the photoelectric detector is blocked by the photoelectric detection board, the photoelectric detector sends a signal to the controller, thereby stopping the operation of the direct drive motor 20 and protecting the direct drive motor 20.

[0021] The closed-loop control method for the high-precision nitrous oxide flow regulating valve includes the following steps: Step S0: Initialization. When the plug is fully in contact with the transition section of the throat, the flow area corresponding to the throat is zero. At this time, when the plug stroke is 0, the position of the dynamic position detection plate is zero. Step S1: The controller collects pressure data from the pressure sensor and temperature data from the temperature sensor in real time, and calculates the inlet liquid density; based on the inlet liquid density, the target flow area corresponding to the target nitrous oxide flow rate is calculated using the liquid cavitation venturi flow rate formula; the target nitrous oxide flow rate is a known quantity. Step S2: Calculate the blockage travel distance based on the target flow area; Step S3: The controller drives the high-precision laser displacement sensor 10 to detect the real-time position of the dynamic position detection piece 9; When the real-time position of the dynamic position detection plate is greater than the end cap stroke, the controller drives the needle rod to move closer to the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. When the real-time position of the dynamic position detection plate is less than or equal to the end cap stroke, the controller drives the needle rod to move further away from the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. Step S4: When the plug moves, the controller simultaneously drives the high-precision laser displacement sensor 10 to detect the real-time position of the dynamic position detection piece 9. When the absolute value of the difference between the real-time position of the dynamic position detection piece and the stroke of the plug is less than the displacement threshold, it is considered that the plug has moved to the target position corresponding to the target flow area. Repeat steps S1-S4 to achieve closed-loop control of the high-precision nitrous oxide flow regulating valve.

[0022] The steps for calculating the target flow area corresponding to the target flow rate of nitrous oxide using the liquid cavitation Venturi flow formula are as follows: The formula for the flow rate of a liquid cavitation venturi tube is: ; in, The target flow rate for nitrous oxide; For flow coefficient; For the throat circulation area; To collect pressure data from the pressure sensor in real time; This is the saturated vapor pressure of the liquid under local temperature conditions; Given the inlet liquid density; calculate the flow area at the throat. Throat circulation area This refers to the target flow area corresponding to the target flow rate of nitrous oxide.

[0023] The steps to calculate the plug stroke are as follows: (1) in, Target circulation area; The length of the plug. For the end of the journey, This refers to the length of the transition segment of the larynx. The diameter of the throat inlet. The diameter of the throat exit. The cone angle of the plug; in, ; The relationship between the plug length and the throat inlet diameter is as follows: ; Will and Substituting into equation (1), the target circulation area is obtained as follows:

[0024] Take the length of the transition segment of the larynx ,but: (2) The stroke of the plug is obtained according to formula (2); Formula (2) represents the target circulation area. The relationship with the journey h, and determines the target circulation area. The parameter is the throat inlet diameter. d 1 and the cone angle of the plug ； The nitrous oxide flow rate formula from QJ 1783A-96 "General Specification for Cavitation Venturi Tubes in Liquid Rocket Engines":

[0025] in The target flow rate for nitrous oxide; For flow coefficient; For the throat circulation area; To collect pressure data from the pressure sensor in real time; This is the saturated vapor pressure of the liquid under local temperature conditions; The density of the liquid at the valve inlet; The density of the liquid at the valve inlet is calculated using pressure data from the pressure sensor and temperature data from the temperature sensor. The throat flow area in the formula Replace the value with the target circulation area That is, to obtain the nitrous oxide flow rate under cavitation conditions. The value of is: ; Under the condition of a steady inflow, in the formula , , , , ,and All are constants, flow rate It's about the itinerary. A quadratic function in one variable, when the end cap angle θ Take 6 o When the quadratic term is negligible, the flow rate... It's about the itinerary. It is a linear function; from the formula, it can be seen that when other conditions remain unchanged, the flow area and flow rate of the closed-loop control high-precision nitrous oxide flow regulating valve are linearly related, and the flow rate can be changed by adjusting the flow area of ​​the closed-loop control high-precision nitrous oxide flow regulating valve. The direct drive motor 20 is an ultra-thin DC direct drive servo motor. It is directly connected to the load to achieve direct drive. By using a direct drive motor, all mechanical transmission components are eliminated, such as ball screw pairs, racks and pinions, transmission belts, pulleys, and gearboxes. This eliminates problems like backlash and flexibility caused by mechanical transmission, improving transmission accuracy. The hollow configuration of the direct drive motor, in conjunction with the bushing 13, houses the lead screw 17 inside the motor, making the space more compact and reducing the motor's size.

[0026] The lead screw 17 and lead screw nut 18 are of grade C3, with an error accuracy of 300mm and an error within ±0.001mm.

[0027] Using deionized water as the simulation liquid and high-pressure nitrogen as the extrusion gas source, the repeatability of the closed-loop control high-precision flow regulating valve, the accuracy of reciprocating adjustment and positioning control, and the linear relationship between the needle rod stroke and the flow rate were tested.

[0028] Repeatability tests were conducted on the valve. The specific process involved fixing the valve opening and upstream pressure, and calibrating the flow rate. The calibration results are shown in Table 1. Data processing yielded an average value of 272.17 g / s, a sample variance of 0.063, a sample standard deviation of 0.252, a population variance of 0.042, and a population standard deviation of 0.205. The flow rates in the three tests were almost identical, with an error within the generally permissible 5% range in the aerospace industry, indicating high precision in the valve's closed-loop control position adjustment.

[0029] Table 1 Valve Repeatability Tests

[0030] An accuracy test was conducted on the reciprocating adjustment and positioning control of the motor. The specific process involved reciprocating adjustment of the valve opening and calibrating its flow rate. The calibration results are shown in Table 2. The test results show that, under the same opening conditions, the flow rate error is less than 5% of the typical allowable error in the aerospace industry, indicating that the motor positioning is accurate and has good repeatability.

[0031] Table 2 Accuracy Test of Motor Reciprocating Adjustment Positioning Control

[0032] A verification test was conducted to demonstrate the linear relationship between the needle plunger stroke and flow rate, and multiple calibration tests were performed. The calibration results are as follows: Figure 17 As shown, the experimental data are distributed almost linearly, indicating that the flow rate and the needle rod stroke maintain a basically linear relationship, realizing linear adjustment of the flow rate and facilitating adjustment of the throat flow area.

[0033] Taking the operating conditions of 10 MPa upstream pressure, 0.95 flow coefficient, and 300 K temperature as an example, the theoretical relationship between stroke and flow rate is calculated, and the results are as follows: Figure 19 As shown, the flow regulation exhibits a good linear relationship.

Claims

1. A closed-loop control high-precision nitrous oxide flow regulating valve, characterized in that: It includes a needle rod, valve body, lead screw drive unit, drive motor unit, and controller; The drive motor unit includes a direct drive motor, a motor protective cover, and a motor base plate; The motor protective cover includes a lead screw protection section, a motor protection section, and a protective base; the motor protection section and the lead screw protection section are arranged sequentially from bottom to top on the top surface of the protective base; a base through hole is provided in the center of the protective base; a base through hole is provided in the center of the motor base plate; both the motor protection section and the lead screw protection section are thin-walled barrel-shaped; the motor protection section, the lead screw protection section, and the base through hole are all coaxial with the base through hole; a direct drive motor is nested inside the motor protection section; the motor base plate is fixedly installed on the bottom surface of the protective base; The valve body is a cylinder; an axial cavity is provided between the two end faces of the valve body; a coaxial straight section, a throat section, and an expansion section are sequentially arranged in the cavity; the throat section includes a sequentially arranged contraction section and a transition section; the transition section is smoothly connected to the expansion section; the contraction section is smoothly connected to the straight section. A liquid outlet is provided on one end face of the valve body; the liquid outlet is a through hole; the liquid outlet is connected to the outlet of the expansion section; A first countersunk hole is provided on the other end face of the valve body; an end cap is provided in the first countersunk hole; the first countersunk hole is connected to the inlet of the straight section; The inner wall of the straight section is provided with a radial liquid inlet through hole; a liquid inlet pipe is fixedly installed in the liquid inlet through hole; a temperature sensor and a pressure sensor are respectively installed on the inner wall of the liquid inlet pipe. The end cap has a center hole; the end cap hole is a through hole; the end cap hole and the first countersunk hole are both coaxial with the cavity; The needle rod includes a plug and a needle rod arranged coaxially; the plug is a cone; the bottom surface of the plug is fixedly connected to one end face of the needle rod; the other end face of the needle rod is fixedly connected to the lead screw drive part; the plug is coaxially nested in the cavity of the valve body; The pin slide is nested inside the end cap hole of the end cap; The lead screw transmission unit is nested and coaxially fixed on the shaft of the direct drive motor; the lead screw transmission unit converts the rotational motion of the direct drive motor into the linear motion of the lead screw transmission unit, thereby driving the pin slide rod to move linearly. The controller is connected to a direct drive motor, a high-precision laser displacement sensor, a temperature sensor, and a pressure sensor, respectively. A dynamic position monitoring plate is installed on the needle bolt slide bar; a high-precision laser displacement sensor is installed on the outer wall of the motor protection section; the controller is connected to the high-precision laser displacement sensor.

2. The closed-loop control high-precision nitrous oxide flow regulating valve according to claim 1, characterized in that, The cone angle of the plug is The range of the plug cone angle is .

3. The closed-loop control high-precision nitrous oxide flow regulating valve according to claim 1, characterized in that, A sealing bushing is provided at one end of the straight section near the end cover; The sealing bushing includes a sealing bushing base and a shaft sealing sleeve; both the sealing bushing base and the shaft sealing sleeve are hollow cylinders; the shaft sealing sleeve is coaxially disposed on the end face of the sealing bushing base; the inner diameter of the sealing bushing base is smaller than the inner diameter of the shaft sealing sleeve; the outer diameter of the shaft sealing sleeve is smaller than the outer diameter of the sealing bushing base; the outer diameter of the shaft sealing sleeve is the same as the inner diameter of the straight section.

4. The closed-loop control high-precision nitrous oxide flow regulating valve according to claim 1, characterized in that, The lead screw transmission unit includes a pin connection structure and a transmission structure; The pin-bolt connection structure includes a bushing and a fisheye connector; the fisheye connector is a rod end spherical bearing; the bushing is a cylinder; the top surface of the bushing has a first blind hole along the axial direction at its center; the first blind hole is fixedly connected to the pin-bolt slide rod by a thread; the outer wall of the bushing has a radial fisheye groove; the bearing head of the fisheye connector is disposed in the fisheye groove; the outer wall of the bushing has a fixing through hole perpendicular to the axis of the bushing; a first bolt is disposed in the fixing through hole; after the bearing head of the fisheye connector is disposed in the fisheye groove, the first bolt limits and fixes the fisheye connector to the bushing by passing through the mounting hole of the bearing head of the fisheye connector; The transmission structure includes a lead screw, a lead screw nut, a bushing, an adapter plate, an anti-rollover shaft, a first slider, and a second slider. The lead screw nut includes a stud and a stud flange; the stud is a hollow cylinder, and the inner wall of the stud is provided with internal threads; the outer wall of the lead screw is provided with external threads; the diameter of the inner wall of the stud is the same as the diameter of the lead screw; the stud flange is fixedly mounted on the outer wall of the stud; the end face of the stud flange is provided with several stud fixing holes; The adapter plate is a circular flange; several adapter plate fixing holes are respectively provided on the end face of the adapter plate along the outer circumference and the inner circumference; the adapter plate is fixedly connected to the shaft of the direct drive motor by bolts through the adapter plate fixing holes on the outer circumference of the adapter plate; the adapter plate is fixedly connected to the stud flange by bolts through the adapter plate fixing holes on the inner circumference of the adapter plate; the adapter plate is used to connect the lead screw nut and the direct drive motor, and transmit the torque of the motor to the lead screw; The anti-roll shaft is a hollow cylinder; the outer wall of the anti-roll shaft is respectively provided with a first slider groove and a second slider groove; a first slider is fixedly installed in the first slider groove; a second slider is fixedly installed in the second slider groove; the anti-roll shaft ensures that the lead screw only undergoes linear motion and does not rotate relative to the direct drive motor; The bushing includes a bushing column and a bushing flange; the bushing column is a hollow cylinder; the bushing flange is fixedly installed on the outer wall of the bushing column; a plurality of bushing flange bolt holes are provided on the end face of the bushing flange; a first groove and a second groove are respectively provided on the inner wall of the bushing column along the axial direction. The inner diameter of the anti-rollover shaft is the same as the diameter of the lead screw; A displacement blind hole is provided on one end face of the lead screw; an anti-roll shaft is provided on the outer wall of the other end face of the lead screw; a thread is provided in the displacement blind hole; the displacement blind hole is fixedly connected to the threaded rod end of the fisheye connector by the thread. The lead screw is nested from left to right as follows: motor protective cover, lead screw nut, adapter plate, direct drive motor, motor base plate, anti-roll shaft and shaft sleeve. The lead screw and nut are connected by threads to convert rotational motion into linear motion; the lead screw and anti-roll shaft are clearance-fitted; the adapter plate is fixedly connected to the stud flange of the lead screw and nut by screws; the stud flange of the lead screw and nut is fixedly connected to the shaft of the direct drive motor by screws; the anti-roll shaft is nested inside the bushing, and the end face of the anti-roll shaft is flush with the end face of the lead screw; the bushing and anti-roll shaft are clearance-fitted; the first slider of the anti-roll shaft is embedded in the first groove; the second slider of the anti-roll shaft is embedded in the second groove; the sleeve flange of the bushing is fixedly connected to the motor base plate by bolts; a bushing cover is provided on the end face of the bushing away from the motor base plate.

5. A closed-loop control high-precision nitrous oxide flow regulating valve according to claim 4, characterized in that, A photoelectric detection plate is fixedly installed on the end face of the lead screw that is flush with the anti-rollover shaft; a photoelectric detector is installed on the inner wall of the bushing cover; the photoelectric detector is connected to the controller.

6. The closed-loop control high-precision nitrous oxide flow regulating valve according to claim 1, characterized in that, An end cap groove is provided on the outer wall of the end cap hole; the end cap groove is coaxial with the valve body; a buffer rubber pad is provided inside the end cap groove.

7. A closed-loop control high-precision nitrous oxide flow regulating valve according to claim 3, characterized in that, The outer wall of the shaft sealing sleeve is provided with a first annular groove; a shaft sleeve sealing ring is provided in the annular groove; the inner wall of the sealing shaft sleeve base is provided with a second annular groove; a base sealing ring is provided in the second annular groove; both the shaft sleeve sealing ring and the base sealing ring are O-rings, which effectively improves the sealing performance of the valve.

8. The control method for a closed-loop control high-precision nitrous oxide flow regulating valve includes the following steps: Step S0: Initialization. When the plug is fully in contact with the transition section of the throat, the flow area corresponding to the throat is zero. At this time, when the plug stroke is zero, the position of the dynamic position detection plate is zero. Step S1: The controller collects pressure data from the pressure sensor and temperature data from the temperature sensor in real time, and calculates the inlet liquid density; Based on the inlet liquid density, the target flow area corresponding to the target flow rate of nitrous oxide is calculated using the liquid cavitation venturi flow formula. The target flow rate of nitrous oxide is known. Step S2: Calculate the blockage travel distance based on the target flow area; Step S3: The controller drives the high-precision laser displacement sensor to detect the real-time position of the dynamic position detection plate; When the real-time position of the dynamic position detection plate is greater than the end cap stroke, the controller drives the needle rod to move closer to the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. When the real-time position of the dynamic position detection plate is less than or equal to the end cap stroke, the controller drives the needle rod to move further away from the throat; the moving distance is the difference between the real-time position of the dynamic position detection plate and the end cap stroke. Step S4: When the plug moves, the controller simultaneously drives the high-precision laser displacement sensor to detect the real-time position of the dynamic position detection plate. When the absolute value of the difference between the real-time position of the dynamic position detection plate and the stroke of the plug is less than the displacement threshold, it is considered that the plug has moved to the target position corresponding to the target flow area. Repeat steps S1-S4 to achieve closed-loop control of the high-precision nitrous oxide flow regulating valve.

9. A closed-loop control high-precision nitrous oxide flow regulating valve according to claim 8, characterized in that, The steps for calculating the target flow area corresponding to the target flow rate of nitrous oxide using the liquid cavitation Venturi flow formula are as follows: The formula for the flow rate of a liquid cavitation venturi tube is: ； in, The target flow rate for nitrous oxide; For flow coefficient; For the throat circulation area; To collect pressure data from the pressure sensor in real time; This is the saturated vapor pressure of the liquid under local temperature conditions; Given the inlet liquid density; calculate the flow area at the throat. Throat circulation area This refers to the target flow area corresponding to the target flow rate of nitrous oxide.

10. A closed-loop control high-precision nitrous oxide flow regulating valve according to claim 8, characterized in that, The steps for calculating the plug stroke are as follows: ； （1） in, Target circulation area; The length of the plug. For the end of the journey, The length of the transition segment of the larynx. The diameter of the throat inlet. The diameter of the throat exit. The cone angle of the plug; in, ; The relationship between the plug length and the throat inlet diameter is as follows: ； Will and Substituting into equation (1), the target circulation area is obtained as follows: ； Take the length of the transition segment of the larynx ,but: ；（2） The stroke of the plug can be obtained according to formula (2).

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