A high-flow-rate, high-pressure sinusoidal pressure generator and its damping test method

Abstract

This invention discloses a high-flow-rate, high-pressure sinusoidal pressure generator and a damping testing method, belonging to the field of fluid supply control. The high-flow-rate, high-pressure sinusoidal pressure generator includes a drive motor, a sinusoidal pressure generator, a coupling, a cooling fan, a protective cover, and a flat base. This pressure generator can be installed upstream of the test object as a component of a gas supply system, introducing unstable disturbances of specific frequency and amplitude to the test object, thereby evaluating the test object's response or stability. The rotor is made of stainless steel with a chrome-plated surface. The sinusoidal pressure generator has active cooling and wear compensation functions, enabling stable operation for extended periods and meeting various testing requirements. Based on the aforementioned high-flow-rate, high-pressure sinusoidal pressure generator, this invention also provides a rocket engine nozzle damping testing method. This method enables accurate measurement of nozzle damping under conditions of gas flow within the engine, high pressure, and the nozzle throat reaching the speed of sound.

Description

Technical Field

[0001] This invention relates to a high-flow-rate, high-pressure sinusoidal pressure generator, and more particularly to a high-flow-rate, high-pressure sinusoidal pressure generator with active cooling and wear compensation functions, capable of stable operation for a long time, serving as a gas supply component in a supersonic nozzle damping measurement system for rocket engines, belonging to the field of fluid supply control. Background Technology

[0002] With the continuous improvement of my country's aerospace technology, more and more high-performance turbojet engines and rocket engines are being used in engineering fields. These engines operate under complex conditions of high temperature and high pressure, which can easily lead to combustion and flow instability, causing problems such as surge, pressure oscillation, structural resonance, and localized ablation, seriously affecting the normal operation and safety of the engine. To conduct research on the combustion stability and operational reliability of engines, combustion, flow, and acoustic evaluation tests are required. A common practice is to use a sinusoidal pressure generator to introduce an unstable disturbance of a specific frequency into the system under test, thereby examining the system's response or stability.

[0003] Currently, common sinusoidal pressure generators include piston-type, rotary-type, and jet-type, but they generally suffer from the following problems: 1. Most existing sinusoidal pressure generators are used for dynamic pressure calibration of sensors, only considering high operating frequency or low distortion requirements. Their pressure or flow rate is relatively low, failing to meet the need for providing high-flow, high-pressure, and highly unstable flow for engine testing. 2. Existing sinusoidal pressure generators do not consider the needs of long-term operation, resulting in significant heat generation and severe wear. Increased leakage and significant performance degradation follow wear. 3. Existing sinusoidal pressure generators are generally located at the end of the system, with the working gas directly discharged to the outside. There are no sinusoidal pressure generators suitable for gas supply systems, therefore they are unsuitable for combustible gases, etc.

[0004] In rocket engines, the nozzle plays a crucial role in suppressing unstable combustion; this function is known as nozzle damping. Nozzle damping is typically measured experimentally and is of significant guiding importance for rocket engine design. Currently, pulse generators or loudspeakers are commonly used as excitation sources for nozzle damping measurements. However, the former suffers from rapid attenuation at low pulse intensities and the generation of high-order harmonics at high pulse intensities, while the latter can only be tested under normal pressure and stagnant conditions. Both methods exhibit substantial errors. By using a sinusoidal pressure generator to apply a specific frequency of unstable disturbance to the incoming gas flow, accurate measurement of nozzle damping can be achieved even when the nozzle flow reaches the speed of sound and the engine internal pressure is high.

[0005] In conclusion, it is essential to design a high-flow-rate, high-pressure sinusoidal pressure generator with active cooling and wear compensation functions, which can operate stably for a long time and serve as a component of a gas supply system, in accordance with actual scientific research needs. Summary of the Invention

[0006] To conduct engine combustion, flow, and acoustic evaluation tests, one of the main objectives of this invention is to provide a high-flow-rate, high-pressure sinusoidal pressure generator. This pressure generator can be installed upstream of the test object as a component of a gas supply system, introducing unstable disturbances of specific frequency and amplitude into the test object to evaluate its response or stability. The sinusoidal pressure generator of this invention features a large flow rate and high operating pressure, enabling engine testing under high-pressure and supersonic flow conditions. Furthermore, the sinusoidal pressure generator incorporates active cooling and wear compensation functions, allowing for stable operation over extended periods and meeting diverse testing requirements.

[0007] Another major objective of this invention is to provide a method for testing the nozzle damping of a rocket engine based on the aforementioned high-flow-rate, high-pressure sinusoidal pressure generator. This method enables accurate measurement of nozzle damping under conditions where there is gas flow inside the engine, the pressure is high, and the nozzle throat reaches the speed of sound.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] The present invention discloses a high-flow-rate, high-pressure sinusoidal pressure generating device, comprising a drive motor, a sinusoidal pressure generator, a coupling, a cooling fan, a protective cover, and a flat base.

[0010] The drive motor and the sinusoidal pressure generator are bolted to the flat base. The output shaft of the drive motor is connected to the rotor shaft of the sinusoidal pressure generator via a coupling. The cooling fan and the rotor shaft are keyed together, and the axial position of the cooling fan is limited by a step on the rotor shaft and the coupling. A protective cover encloses the output shaft of the drive motor, the coupling, the rotor shaft of the sinusoidal pressure generator, and the cooling fan, and the cover is bolted to the flat base.

[0011] The sinusoidal pressure generator includes a housing, shaft end cover, inlet end cover, rotor shaft, outlet end cover, stator assembly, rotor, bearings, and dynamic seals.

[0012] The housing is approximately cylindrical, with a mounting base welded to the bottom and heat sinks and lifting rings on the top. The rotor shaft, rotor, and bearings are installed inside the housing. Shaft end covers and air inlet end covers are installed on the front and rear sides of the housing, respectively. Two sets of stator assemblies are symmetrically installed in the mounting holes of the bosses on the left and right sides of the housing, and the stator assemblies are fixed by air outlet end covers installed on the bosses. The shaft end covers, air inlet end covers, and air outlet end covers are bolted to the housing, and O-ring seals are used between the three and the housing. The shaft end covers, air inlet end covers, and air outlet end covers are disc-shaped. The shaft end covers have a shaft hole in the center, through which the rotor shaft passes. The air inlet end covers and air outlet end covers have threaded holes in the center. Heat sinks are located on the outer sides of the shaft end covers and air inlet end covers. The rotor shaft is thinner at one end and thicker at the other. The thinner end of the rotor shaft has a keyway, a step, and an annular groove. A dynamic seal is installed in the annular groove, forming a seal with the shaft hole in the center of the shaft end cover. The thicker end of the rotor shaft is hollow, with bearings mounted on both sides. A strip-shaped through-hole and threaded hole are circumferentially formed in the middle. The rotor itself is annular, with evenly distributed circular through-holes along its circumference. The rotor is secured to the rotor shaft by anti-loosening bolts located on both sides of these through-holes, allowing it to rotate. The inner side of the rotor has annular grooves.

[0013] The stator assembly includes a compensating stator, a retaining stator, a spring, an outer end seal, a gasket, and a side seal.

[0014] The compensating stator is cylindrical with a boss at the bottom and a cylindrical groove at the top. It has annular and straight grooves on the sides and a square through-hole in the center. The compensating stator is located at the innermost end of the stator assembly, and the lower surface of the boss is an arc surface that conforms to the outer surface of the rotor. The retaining stator has a flat upper part and a cylindrical lower part, with the same square through-hole in the center as the compensating stator. The flat upper part of the retaining stator is engaged with the outermost step of the mounting hole in the stator assembly, and the outer side of the lower cylindrical part of the retaining stator has a groove for installing a side sealing ring. The lower cylindrical part of the retaining stator is inserted into the cylindrical groove of the upper part of the compensating stator, and the two are sealed by the side sealing ring. A spring is fitted over the lower cylindrical part of the retaining stator. The outer end sealing ring is installed in the groove on the upper surface of the retaining stator, and the sealing gasket is installed on the lower surface of the flat upper part of the retaining stator.

[0015] Preferably, the drive motor is a three-phase asynchronous motor, which has the characteristics of high power, high torque and speed, and convenient speed adjustment, which can meet the drive requirements of this device, and generate sinusoidal pressure fluctuations of different frequencies by adjusting the speed.

[0016] Preferably, the rotor is made of stainless steel with a chrome-plated surface. Stainless steel has good corrosion resistance and thermomechanical properties. The rotor and the compensating stator are in close contact and experience high-speed friction during operation. The chrome plating treatment improves the hardness and wear resistance of the rotor surface, thereby extending the rotor's service life.

[0017] Preferably, the bearing is a deep groove ball bearing, which has a low coefficient of friction, high limiting speed, low noise and vibration, requires no frequent maintenance, and is suitable for the high-speed rotation requirements of this device.

[0018] Preferably, the dynamic seal uses a high-speed rotating bore toothed combination seal, which is composed of a low-friction polytetrafluoroethylene (PTFE) composite slip ring and an O-ring. Compared with traditional O-rings, the combination seal has the characteristics of long service life, low friction, no leakage, and strong adaptability, and can effectively reduce the resistance of the seal rotation under high pressure conditions.

[0019] Preferably, the compensating stator is made of isostatic graphite, which has a dense texture, can ensure sealing performance, has good wear resistance and shock absorption, good thermomechanical properties, and the friction coefficient between graphite and stainless steel is small, which can reduce operating resistance and improve service life.

[0020] The operating method of the high-flow-rate, high-pressure sinusoidal pressure generator disclosed in this invention is as follows: After assembling the high-flow-rate, high-pressure sinusoidal pressure generator according to the connection relationship, the high-pressure gas source is connected to the inlet end cap, and the object under test is connected to the outlet end cap. During operation, a frequency converter controls the drive motor to run at a certain speed, and the drive motor drives the rotor shaft to rotate through the coupling. The high-pressure gas flowing out from the high-pressure gas source passes through the pressure reducing valve to generate a stable working pressure source, and enters the sinusoidal pressure generator from the inlet end cap through the inlet pipe. The gas inside the sinusoidal pressure generator is discharged from the housing through the intermittent opening and closing state of the circular holes on both sides of the rotor and the rectangular holes of the stator assembly. Since the stator assemblies on both sides are relatively distributed and spaced 180° apart, the state of the exhaust channels on both sides changes synchronously with the rotation of the rotor. When the circular holes on the rotor and the square holes of the stator assembly are completely misaligned, the exhaust channel area is 0, that is, no gas flows to the outlet, and the downstream pressure is at its lowest value; when the circular holes on the rotor and the square holes of the stator assembly are completely aligned, the exhaust channel area reaches its maximum value, and the corresponding downstream pressure is at its highest value. During uniform rotation, the ventilation area between the circular holes on the rotor and the square holes in the stator assembly changes sinusoidally, generating a sinusoidal pressure wave downstream of the sinusoidal pressure generator. Compared to single-sided exhaust, the symmetrically arranged gas outlets on both sides double the exhaust flow rate while avoiding lateral forces generated by single-sided exhaust of large-flow gas, preventing bearing overload, and improving the operational stability of the high-flow-rate, high-pressure sinusoidal pressure generator. The cavity inside the rotor shaft reduces the flow velocity of the incoming high-pressure gas, stabilizing the upstream pressure, optimizing gas flow, and thus reducing the distortion of the sinusoidal pressure waveform. The amplitude of the sinusoidal pressure generated by the sinusoidal pressure generator is changed by adjusting the upstream gas pressure. The frequency of the sinusoidal pressure is determined by the number of circular exhaust holes on the rotor and their rotational speed. The frequency of the sinusoidal pressure can be adjusted by controlling the speed of the drive motor through a frequency converter.

[0021] Based on the aforementioned high-flow-rate, high-pressure sinusoidal pressure generating device, this invention also discloses a method for testing the damping of a rocket engine nozzle:

[0022] The nozzle under test is mounted on the engine, with the engine head connected to the main and branch intake pipes. A pressure sensor is installed on the engine. Gas from the main intake, after exiting the high-pressure gas source, flows into the engine through a pressure reducing valve and flow meter, maintaining a constant high pressure within the engine. Gas from the branch intake, after exiting the high-pressure gas source and being depressurized by the pressure reducing valve, enters a sinusoidal pressure generator. This generator drives a motor to rotate the rotor shaft at a certain speed, generating sinusoidal pressure that is introduced into the engine, causing steady-state wave disturbances. Pressure signals are collected by the pressure sensors, converted and processed by a data acquisition instrument, and then imported into a computer for analysis, thereby measuring nozzle damping. This method improves the accuracy of nozzle damping measurement.

[0023] The collected pressure signals are converted and processed by a data acquisition instrument and then imported into a computer for analysis and processing, thereby measuring nozzle damping. The method is as follows:

[0024] The pressure signal is filtered to obtain the pressure oscillation curve. Since the pressure oscillation decays exponentially, the envelope of the peak value of the oscillation curve is taken. Then, the natural logarithm of the envelope of the pressure peak value is taken to obtain the ln(p)-t relationship curve. The ln(p)-t relationship curve is linear, and the slope of this linear relationship is the measured nozzle damping attenuation coefficient.

[0025] Beneficial effects:

[0026] 1. The present invention discloses a high-flow-rate, high-pressure sinusoidal pressure generating device and a damping test method, which, when used, is a component of a gas supply system. It is connected upstream to a high-pressure gas source and downstream to the object to be tested that requires sinusoidal pressure. It does not directly discharge gas to the outside world and can carry out related experiments on combustible gases, harmful gases, etc.

[0027] 2. This invention discloses a high-flow-rate, high-pressure sinusoidal pressure generator and a damping test method. The generator is equipped with a cooling fan and heat sinks on its outer surface, which enhances heat dissipation, controls temperature rise caused by friction between dynamic seals and bearings, extends component life, and ensures stable long-term operation of the sinusoidal pressure generator. The heat sinks also act as reinforcing ribs, enabling the sinusoidal pressure generator to withstand higher pressures.

[0028] 3. This invention discloses a high-flow-rate, high-pressure sinusoidal pressure generator and a damping testing method, optimized for high gas flow and high operating pressure. It employs symmetrical exhaust from both sides. Compared to single-sided exhaust, the symmetrical arrangement of gas outlets on both sides doubles the original gas flow rate while fundamentally avoiding the lateral forces generated by single-sided exhaust of large-flow-rate gas, preventing bearing imbalance, and improving system operational stability. The rotor shaft has an internal cavity that reduces the flow velocity of the incoming high-pressure gas, stabilizing the upstream pressure and storing the gas, optimizing gas flow, and thus reducing the distortion of the sinusoidal pressure waveform.

[0029] 4. This invention discloses a high-flow-rate, high-pressure sinusoidal pressure generating device and a damping testing method. Its stator assembly includes a compensating stator, a retaining stator, and springs. The compensating stator is made of isostatically pressed graphite, which has good wear resistance and vibration damping properties, and a low coefficient of friction. Under the spring clamping force, the compensating stator can still remain in close contact with the rotor after wear occurs, thus providing wear compensation. It is reliable in operation, stable in operation, and has a long maintenance cycle.

[0030] 5. Compared to existing domestic testing methods, the rocket engine nozzle damping testing method and damping test method disclosed in this invention can solve the problems that the loudspeaker excitation method can only be used to conduct tests under normal pressure and no flow conditions, and the pulse excitation method has large errors and poor attenuation characteristics. This invention establishes high-pressure operating conditions for the engine through the main gas path, and the branch path intermittently supplies air through a sinusoidal pressure generator, generating pressure oscillations of a certain frequency in the engine, while simultaneously making the flow at the nozzle throat reach the speed of sound, simulating the working state of a real engine and achieving accurate measurement of nozzle damping. Attached Figure Description

[0031] Figure 1 A schematic diagram of a specific embodiment of a high-flow-rate, high-pressure sinusoidal pressure generator;

[0032] Figure 2 for Figure 1 A schematic diagram of the external shape of a sinusoidal pressure generator;

[0033] Figure 3 A horizontal cross-sectional schematic diagram of a sinusoidal pressure generator;

[0034] Figure 4 An exploded view of the sinusoidal pressure generator, omitting the bearing;

[0035] Figure 5 for Figure 4 Schematic diagram of the middle stator assembly;

[0036] Figure 6 This is a comparative cross-sectional view of the stator assembly before and after wear.

[0037] Among them, 101-sine pressure generator, 102-cooling fan, 103-coupling, 104-protective cover, 105-drive motor, 106-flat base, 201-housing, 202-shaft end cover, 203-inlet end cover, 204-rotor shaft, 205-outlet end cover, 206-stator assembly, 207-rotor, 208-bearing, 209-dynamic seal, 301-compensating stator, 302-retaining stator, 303-spring, 304-outer end seal ring, 305-sealing gasket, 306-side seal ring. Detailed Implementation

[0038] To better illustrate the purpose and advantages of the present invention, the present invention will be further described in detail below with reference to the figures and specific embodiments.

[0039] like Figures 1 to 4 As shown, this embodiment discloses a high-flow-rate, high-pressure sinusoidal pressure generator, including a drive motor 105, a sinusoidal pressure generator 101, a coupling 103, a cooling fan 102, a protective cover 104, and a flat base 106. The sinusoidal pressure generator 101 includes a housing 201, a shaft end cover 202, an air inlet end cover 203, a rotor shaft 204, an air outlet end cover 205, a stator assembly 206, a rotor 207, a bearing 208, and a dynamic seal 209.

[0040] The drive motor 105 and the sinusoidal pressure generator 101 are bolted to the flat base 106. The drive motor 105 is a three-phase asynchronous motor with a rated power of 15kW, a rated speed of 2935rpm, and a rated torque of 48.8Nm. Its speed can be adjusted by a frequency converter, which can meet the drive requirements of this device. The output shaft of the drive motor 105 is connected to the rotor shaft 204 of the sinusoidal pressure generator 101 via a coupling 103. The coupling 103 is a plum blossom type coupling, which has a simple structure, is easy to maintain, and has a high load-bearing capacity. The cooling fan 102 and the rotor shaft 204 are connected by a key, and its axial position is limited by the step on the rotor shaft 204 and the coupling 103. The output shaft of the drive motor 105 drives the rotor shaft 204 of the sinusoidal pressure generator 101 and the cooling fan 102 to rotate synchronously. The airflow generated by the cooling fan 102 can cool the sinusoidal pressure generator 101. The protective cover 104 encloses the output shaft of the drive motor 105, the coupling 103, the rotor shaft 204 of the sine pressure generator 101, and the cooling fan 102. The protective cover 104 is fixed to the flat base 106 with bolts, serving a protective and safety function. The protective cover 104 has several large holes to facilitate the flow of cooling air.

[0041] The housing 201 of the sinusoidal pressure generator 101 is approximately cylindrical, with a mounting base welded to the lower part and heat sinks and lifting rings on the upper part. The housing 201 primarily serves as structural support and a seal, ensuring the safe and stable operation of the overall structure and preventing gas leakage within the cavity. The rotor shaft 204, rotor 207, and bearing 208 are installed inside it. Shaft end caps 202 and inlet end caps 203 are installed on the front and rear sides of the housing 201, respectively. Two sets of stator assemblies 206 are symmetrically installed in the mounting holes of the bosses on the left and right sides of the housing 201. The stator assemblies 206 are fixed by outlet end caps 205 installed on the bosses. The shaft end caps 202, inlet end caps 203, and outlet end caps 205 are bolted to the housing 201, and O-rings are used for sealing between them and the housing 201. The shaft end caps 202, inlet end caps 203, and outlet end caps 205 are disc-shaped. The shaft end cap 202 has a central shaft hole through which the rotor shaft 204 passes. The inlet end cover 203 and the outlet end cover 205 have threaded holes in their centers for connecting the inlet and outlet pipes, respectively. High-pressure gas flowing from the high-pressure gas source enters the sinusoidal pressure generator 101 through the inlet pipe and inlet end cover 203. The shaft end cover 202 and the inlet end cover 203 have heat sinks on their outer sides, which also act as reinforcing ribs, allowing the sinusoidal pressure generator 101 to withstand higher pressures. The rotor shaft 204 is thinner at one end and thicker at the other. The thinner end of the rotor shaft 204 has a keyway for mounting the coupling 103 and the cooling fan 102, a step for limiting the axial position of the cooling fan 102, and an annular groove for mounting the dynamic seal 209. The dynamic seal 209 uses a high-speed rotary bore toothed combination seal, which is composed of a low-friction polytetrafluoroethylene (PTFE) composite slip ring and an O-ring. Compared with traditional O-rings, it features long service life, low friction, no leakage, and strong adaptability, effectively reducing rotational resistance under high pressure conditions. The dynamic seal 209 forms a seal with the shaft hole at the center of the shaft end cover 202, ensuring that the working gas inside the sinusoidal pressure generator 101 does not leak during operation. The thicker end of the rotor shaft 204 is hollow, with bearings 208 mounted on both sides. The bearings 208 are deep groove ball bearings, which have a low coefficient of friction, high limiting speed, low noise and vibration, and require minimal maintenance, making them suitable for the high-speed rotation requirements of this device. A strip-shaped through-hole for working gas flow and a threaded hole for rotor mounting are circumferentially opened in the middle of the thicker end of the rotor shaft 204. When the incoming high-pressure gas enters the cavity at the thicker end of the rotor shaft 204, the flow velocity decreases, thereby stabilizing the pressure and reducing the distortion of the sinusoidal pressure waveform. The rotor 207 has a ring structure, is made of stainless steel, and has a chrome-plated surface. The rotor 207 and the compensating stator 301 are closely fitted and rub against each other at high speed during operation. The chrome plating treatment improves the hardness and wear resistance of the rotor 207 surface, thereby extending the service life of the rotor 207.The rotor 207 has 16 evenly distributed circular through holes along its circumference, each with a diameter of 9 mm. When the rotor 207 rotates one revolution, the through holes of the rotor 207 coincide with the through holes of the stator assembly 206 16 times. This means that when the rotor 207 rotates at 1 r / s, it can generate a 16 Hz ventilation disturbance. The rotor 207 is fixed to the rotor shaft 204 by anti-loosening bolts located on both sides of the through holes, and rotates accordingly. The inner side of the rotor 207 has an annular groove to facilitate smooth flow of working gas.

[0042] The stator assembly 206 includes a compensating stator 301, a retaining stator 302, a spring 303, an outer end sealing ring 304, a sealing gasket 305, and a side sealing ring 306.

[0043] The compensating stator 301 is cylindrical in shape, with a boss at the bottom and a cylindrical groove at the top. It also has annular and straight grooves on its sides and a 9mm × 13.5mm rectangular through-hole in the center. The compensating stator 301 is made of isostatic graphite, which is dense and ensures sealing performance. It also has good wear resistance and shock absorption. Furthermore, the low coefficient of friction between the graphite and the stainless steel rotor 207 reduces operating resistance and extends service life. The compensating stator 301 is located at the innermost end of the stator assembly 206. The lower surface of its boss is an arc surface that conforms to the outer surface of the rotor 207, allowing it to fit tightly with the rotor 207 under the action of the spring 303 to form a seal. Gas can only flow out when the square hole of the compensating stator 301 coincides with the circular hole of the rotor 207. The annular and straight grooves on the sides of the compensating stator 301 mate with tooling for easy disassembly, assembly, and positioning. The upper part of the retaining stator 302 is a flat plate, and the lower part is a cylinder. A square through-hole, identical to that of the compensating stator 301, is located in the center of the retaining stator 302, and these holes are aligned. The upper flat plate of the retaining stator 302 is a circle with square-cut edges, which fits onto the outermost step of the mounting hole in the stator assembly 206, providing concentric positioning and horizontal positioning of the square hole. A groove for mounting the side sealing ring 306 is located on the outer side of the lower cylinder of the retaining stator 302. The lower cylinder of the retaining stator 302 is inserted into the cylindrical groove on the upper part of the compensating stator 301, and the two are sealed by the side sealing ring 306. A spring 303 is fitted over the lower cylinder of the retaining stator 302. After the stator assembly 206 is assembled and installed in the housing 201, the spring 303 receives a certain amount of compression, and a clamping force is applied to the compensating stator 301. When the compensating stator 301 wears down after prolonged operation, the length of its lower boss shortens. Under the pressure of the spring 303, the compensating stator 301 moves downward as a whole, still maintaining a tight fit with the rotor 207. Simultaneously, its sealing relationship with the retaining stator 302 remains unchanged, and leakage does not increase. The outer end sealing ring 304 is installed in a groove on the upper surface of the retaining stator 302 to achieve a seal between the stator assembly 206 and the outlet end cover 205. The sealing gasket 305 is installed on the lower surface of the upper plate of the retaining stator 302 to achieve a seal between the stator assembly 206 and the housing 201. The gas inside the sinusoidal pressure generator 101 is discharged outside the housing 201 through the intermittent opening and closing of the circular hole on the rotor 207 and the square holes on both sides of the stator assembly 206. When the circular hole on rotor 207 is completely misaligned with the square hole on stator assembly 206, the exhaust channel area is 0, meaning no gas flows to the outlet, and the downstream pressure is at its lowest value. When the circular hole on rotor 207 is completely aligned with the square hole on stator assembly 206, the exhaust channel area reaches its maximum value, corresponding to the highest downstream pressure. During uniform rotation, the ventilation area between the circular hole on rotor 207 and the square hole on stator assembly 206 changes according to a sinusoidal law, thus generating a sinusoidal pressure wave downstream of the sinusoidal pressure generator.

[0044] Based on the high-flow-rate, high-pressure sinusoidal pressure generator disclosed in this embodiment, this embodiment also discloses a method for testing the nozzle damping of a rocket engine: the nozzle under test is installed on the engine, the engine head is connected to the main and branch intake pipes, and a pressure sensor is installed on the engine. Gas from the main intake flows out of the high-pressure gas source and enters the engine through a valve assembly including a pressure reducing valve and a flow meter, maintaining a constant high pressure inside the engine. Gas from the branch intake flows out of the high-pressure gas source, is reduced in pressure by the pressure reducing valve, and then enters the sinusoidal pressure generator 101. The drive motor 105 drives the rotor shaft 204 to rotate at a certain speed, generating sinusoidal pressure that enters the engine, causing steady-state wave disturbances within the engine. The pressure signal is collected by the pressure sensor, converted and processed by a data acquisition instrument, and then imported into a computer for analysis and processing, thereby measuring the nozzle damping. The specific operating procedure is as follows: (1) Check the connection status of the pipeline and circuit and the working status of the data acquisition system, and confirm that all valves are closed; (2) Open the high-pressure gas cylinder valve, and the gas flows into the main line and the branch line equipped with the sine pressure generator 101. Adjust the pressure after the valve of the pressure reducing valve of the main line and the branch line to the design value according to the experimental conditions; (3) Start the drive motor 105, adjust the frequency converter control knob to make the speed of the drive motor 105 reach the design value, and the data acquisition system starts to collect data; (4) Open the solenoid valve on the main line to make the gas in the main line flow into the engine to establish a high-pressure environment until the internal pressure of the engine stabilizes; (5) Open the branch line (6) Close the solenoid valve on the branch line. The gas in the branch line is intermittently supplied to the engine through the sinusoidal pressure generator 101. At this time, the pressure in the engine will oscillate and rise with the average pressure until the average pressure and the pressure oscillation amplitude reach stability. (7) Close the solenoid valve on the branch line. The engine pressure oscillation will decrease. After the flow stabilizes, close the solenoid valve on the main line and stop the drive motor 105. (8) The data acquisition system stops data acquisition, closes the high-pressure gas cylinder valve, discharges the high-pressure residual gas in the pipeline, and ends the experiment. (9) Select the pressure oscillation attenuation segment data in step (6) for processing. First, filter the pressure signal to obtain the pressure oscillation curve. Since the pressure oscillation decays exponentially, take the envelope of the peak value of the oscillation curve. Then take the natural logarithm of the envelope of the pressure peak value to obtain the ln(p)-t relationship curve. The two are linearly related. The slope of this linear relationship is the nozzle damping attenuation coefficient.

[0045] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-flow-rate, high-pressure sinusoidal pressure generating device, characterized in that: Includes drive motor, sinusoidal pressure generator, coupling, cooling fan, protective cover, and flat base; The drive motor and the sinusoidal pressure generator are bolted to the flat base. The output shaft of the drive motor is connected to the rotor shaft of the sinusoidal pressure generator via a coupling. The cooling fan and the rotor shaft are connected by a key. The axial position of the cooling fan is limited by the step on the rotor shaft and the coupling. The cover encloses the output shaft of the drive motor, the coupling, the rotor shaft of the sinusoidal pressure generator, and the cooling fan. The cover is bolted to the flat base. The sinusoidal pressure generator includes a housing, shaft end cover, inlet end cover, rotor shaft, outlet end cover, stator assembly, rotor, bearings, and dynamic seals; The housing is approximately cylindrical, with a mounting base welded to the bottom and heat sinks and lifting rings on the top. The rotor shaft, rotor, and bearings are installed inside the housing. Shaft end covers and air inlet end covers are installed on the front and rear sides of the housing, respectively. Two sets of stator assemblies are symmetrically installed in the mounting holes of the bosses on the left and right sides of the housing. The stator assemblies are fixed by the air outlet end covers installed on the bosses. The shaft end covers, air inlet end covers, and air outlet end covers are bolted to the housing, and O-rings are used to seal between the three and the housing. The shaft end covers, air inlet end covers, and air outlet end covers are disc-shaped. The shaft end covers have a shaft hole in the center, through which the rotor shaft passes. The intake and exhaust end caps have threaded holes in the center; the shaft end caps and intake end caps have heat sinks on the outside; one end of the rotor shaft is thinner and the other end is thicker; the thinner end of the rotor shaft has a keyway, a step, and an annular groove; the dynamic seal is installed in the annular groove and forms a seal with the shaft hole in the center of the shaft end cap; the thicker end of the rotor shaft is a hollow structure with bearings installed on both sides, and a strip-shaped through hole and a threaded hole are opened in the middle along the circumference; the rotor has an annular structure with evenly distributed circular through holes along the circumference, and the rotor is fixed to the rotor shaft by anti-loosening bolts located on both sides of the through holes and rotates accordingly; there is an annular groove on the inner side of the rotor; The stator assembly includes a compensating stator, a retaining stator, a spring, an outer end seal ring, a sealing gasket, and a side seal ring; The compensating stator is cylindrical with a boss at the bottom and a cylindrical groove at the top. It has annular and straight grooves on the sides and a square through-hole in the center. The compensating stator is located at the innermost end of the stator assembly. The lower surface of the boss at the bottom of the compensating stator is an arc surface that matches the outer surface of the rotor. The retaining stator has a flat upper part and a cylindrical lower part, with the same square through-hole in the center as the compensating stator. The flat upper part of the retaining stator is engaged with the outermost step of the mounting hole in the stator assembly. The outer side of the lower cylindrical part of the retaining stator has a groove for installing a side sealing ring. The lower cylindrical part of the retaining stator is inserted into the cylindrical groove at the top of the compensating stator, and the two are sealed by the side sealing ring. A spring is sleeved on the outside of the lower cylindrical part of the retaining stator. The outer end sealing ring is installed in the groove on the upper surface of the retaining stator, and the sealing gasket is installed on the lower surface of the flat upper part of the retaining stator.

2. The high-flow-rate, high-pressure sinusoidal pressure generating device as described in claim 1, characterized in that: The drive motor is a three-phase asynchronous motor, which generates sinusoidal pressure fluctuations of different frequencies by adjusting the speed.

3. The high-flow-rate, high-pressure sinusoidal pressure generating device as described in claim 1, characterized in that: The rotor is made of stainless steel with a chrome-plated surface. The rotor and the compensating stator are closely fitted and rub against each other at high speed during operation. The chrome plating treatment improves the hardness and wear resistance of the rotor surface, thereby extending the rotor's service life.

4. The high-flow-rate, high-pressure sinusoidal pressure generating device as described in claim 1, characterized in that: The bearing used is a deep groove ball bearing.

5. The high-flow-rate, high-pressure sinusoidal pressure generating device as described in claim 1, characterized in that: The dynamic seal uses a high-speed rotary bore toothed combination seal, which is composed of a low-friction polytetrafluoroethylene composite slip ring and an O-ring.

6. The high-flow-rate, high-pressure sinusoidal pressure generating device as described in claim 1, characterized in that: The compensation stator is made of isostatic graphite.

7. A high-flow-rate, high-pressure sinusoidal pressure generating device as described in any one of claims 1-6, characterized in that: Connect the high-pressure gas source to the inlet end cap and the object under test to the outlet end cap. During operation, a frequency converter controls the drive motor to run at a certain speed, and the drive motor drives the rotor shaft to rotate through the coupling. The high-pressure gas flowing out of the high-pressure gas source passes through the pressure reducing valve to generate a stable working pressure source, and enters the sinusoidal pressure generator through the inlet pipe from the inlet end cap. The gas inside the sinusoidal pressure generator is then discharged from the housing through the intermittent opening and closing of the round holes on both sides of the rotor and the square through holes of the stator assembly. Due to the relative distribution of the two stator assemblies, which are spaced 180° apart, the gas is discharged from the housing. As the rotor rotates, the state of the exhaust channels on both sides changes synchronously. When the circular hole on the rotor is completely misaligned with the square through hole of the stator assembly, the exhaust channel area is 0, meaning no gas flows to the outlet, and the downstream pressure is at its lowest value. When the circular hole on the rotor is completely aligned with the square through hole of the stator assembly, the exhaust channel area reaches its maximum value, corresponding to the highest downstream pressure. During uniform rotation, the ventilation area between the circular hole on the rotor and the square through hole of the stator assembly changes according to a sinusoidal law, generating a sinusoidal pressure wave downstream of the high-flow-rate, high-pressure sinusoidal pressure generator. Compared to single-sided exhaust, the symmetrical arrangement of gas outlets on both sides doubles the original gas flow rate while avoiding lateral forces generated by single-sided exhaust of large-flow gas, preventing bearing overload, and improving the operational stability of the high-flow-rate high-pressure sinusoidal pressure generator. The cavity inside the rotor shaft reduces the flow velocity of the incoming high-pressure gas, stabilizing the upstream pressure, optimizing gas flow, and thus reducing the distortion of the sinusoidal pressure waveform. The amplitude of the sinusoidal pressure generated by the sinusoidal pressure generator can be changed by adjusting the upstream gas pressure. The frequency of the sinusoidal pressure is determined by the number of circular exhaust holes on the rotor and their rotational speed. The frequency of the sinusoidal pressure can be adjusted by controlling the speed of the drive motor through a frequency converter.

8. A method for testing the damping of a rocket engine nozzle, based on a high-flow-rate, high-pressure sinusoidal pressure generator as described in claim 7, characterized in that: The nozzle under test is mounted on the engine, with the engine head connected to the main and branch intake pipes. A pressure sensor is installed on the engine. Gas from the main intake flows out of the high-pressure gas source and enters the engine through a pressure reducing valve and a flow meter, maintaining a constant high pressure inside the engine. Gas from the branch intake flows out of the high-pressure gas source, is reduced in pressure by the pressure reducing valve, and then enters a sinusoidal pressure generator. The drive motor rotates the rotor shaft at a certain speed, generating sinusoidal pressure that enters the engine, causing steady-state wave disturbances within the engine. Pressure signals are collected by the pressure sensor, converted and processed by a data acquisition instrument, and then imported into a computer for analysis and processing, thereby measuring nozzle damping and improving the accuracy of nozzle damping measurement.

9. The method for testing the damping of a rocket engine nozzle as described in claim 8, characterized in that: The collected pressure signals are converted and processed by a data acquisition instrument and then imported into a computer for analysis and processing, thereby measuring nozzle damping. The method is as follows: The pressure signal is filtered to obtain the pressure oscillation curve. Since the pressure oscillation decays exponentially, the envelope of the peak value of the oscillation curve is taken. Then, the natural logarithm of the envelope of the pressure peak value is taken to obtain the ln(p)-t relationship curve. The ln(p)-t relationship curve is linear, and the slope of this linear relationship is the measured nozzle damping attenuation coefficient.

Images