Periodic follow-up test system applied to multi-point measurement of internal pressure of tail cavitation of navigation body

Abstract

The invention provides a periodic follow-up test system applied to multi-point measurement of internal pressure of a tail cavity of a navigation body, and belongs to the technical field of ocean engineering tests. The problems that the internal pressure distribution cannot be accurately obtained and the dynamic process of the space distribution load propelled by the back jet flow cannot be captured due to the fact that the wall surface pressure of the center point of the surface of the model is mostly measured in the existing underwater vehicle water outlet test are solved. The device comprises a navigation body tail main body assembly, a follow-up guide assembly, a probe sensor assembly and a sensor motion sealing assembly which are all installed at the tail of a navigation body, and the probe sensor assembly is installed in the navigation body tail main body assembly through the follow-up guide assembly and is sealed through the sensor motion sealing assembly. When the navigation body is ejected out of the cylinder, the spring and the follow-up assembly are excited by acceleration pulses to drive the multiple probe sensors to stretch into the tail cavity from the bottom to obtain internal pressure, and the probe sensors do periodic reciprocating motion. The device is applied to a measurement test of internal pressure distribution and backjet flow slamming of water tail cavitation bubbles when a navigation body is catapulted.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater vehicle testing, and in particular relates to a periodic servo testing system for multi-point measurement of the internal pressure of a tail cavity of a vehicle. Background Art

[0002] The out-of-water vehicle is rapidly propelled by the high-temperature and high-pressure gas in the launch tube, completing the out-of-tube movement from the carrier located at a certain water depth. After experiencing the underwater free navigation stage, it crosses the air-water interface and enters the air flight stage. During this period, complex multiphase flow phenomena such as the formation and development of the tail cavitation at the bottom of the vehicle, jet impact, air cavity pulsation, and collapse and shedding are involved. It has unsteady and nonlinear characteristics, especially the pressure change in the bubble directly affects the underwater motion state of the vehicle. In addition, the back jet formed by the closure of the cavitation end continues to propel toward the bottom of the vehicle in the vehicle motion coordinate system, forming a spatial load. Conducting research on the tail cavitation flow mechanism and internal pressure evolution is a key link in exploring the motion load boundary of the out-of-water vehicle, and has important engineering significance for the fluid dynamic design in equipment development.

[0003] With the application of existing test equipment and technological innovation, numerous types of experimental studies on the tail cavitation of attached vehicles have been conducted, driving the development of underwater launch technology for vehicles. However, to obtain the internal pressure of the tail cavitation, a sensor is often installed at the center point of the model's bottom surface to measure the wall pressure. On the one hand, the sensor probe cannot be inserted into the bubble and is easily affected by the wall flow field disturbance, resulting in errors in the measured pressure changes of the gas-liquid mixed phase within the bubble. On the other hand, the pressure within the bubble includes the pressure of the gas medium entrained from the cylinder, the jet return pressure, and the fluid micro-cluster disturbance pressure. In particular, the jet return splash direction is highly random, making it difficult to capture its pressure load with a single sensor at the center point. PVDF piezoelectric film sensors offer high dynamic response, strong environmental stability, and versatile sensitivity. They can be easily fabricated into microprobe-type pressure sensors that can be inserted into the tail cavitation. Multiple monitoring points can be arranged to measure the bubble pressure and jet state without affecting the evolution of the tail cavitation flow field. However, if multiple probes were mounted directly on the bottom of the vehicle, the initial state of the vehicle inside the launch tube would be affected. Furthermore, the probe sensors could break during ejection from the tube or during water interception, potentially leading to test failure. Therefore, a multi-point pressure measurement system for the tail cavity's internal pressure was required, in which the probe sensors could expand and contract periodically with the vehicle's launch motion. Summary of the Invention

[0004] In view of this, in order to solve the problem that the existing methods are unable to effectively measure the internal pressure of the tail cavitation of the water-launched vehicle and accurately capture the back jet, the present invention proposes a periodic following test system for multi-point measurement of the internal pressure of the tail cavitation of the vehicle, which is mainly used for the internal pressure distribution of the tail cavitation of the vehicle ejected out of the water and the back jet impact measurement test.

[0005] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: a periodic follow-up test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle, comprising a tail main body component of the vehicle, a follow-up guide component, a probe sensor component, and a sensor motion sealing component; the probe sensor component is installed in the tail main body component of the vehicle through the follow-up guide component, and is sealed by the sensor motion sealing component; when the vehicle is ejected from the tube, the spring and the follow-up component are excited by the acceleration pulse to drive multiple probe sensors to extend from the bottom into the tail cavitation to obtain the internal pressure and perform periodic reciprocating motion.

[0006] The probe sensor assembly includes multiple probe sensors, and the follower guide assembly includes a spring, a spring support, a follower mass block, a connecting rod and a slider. The probe sensor is installed in the threaded hole of the spring support, and the probe end passes through the bottom interlayer plate and the bottom plate in turn. The spring is sleeved on the outside of the probe sensor located in the center, and the two ends are respectively connected to the bottom interlayer plate and the mounting hole end face of the spring support. The spring support is installed in cooperation with the threaded surface below the follower mass block; the two ends of the connecting rod are respectively connected to the follower mass block and the slider by bolts, and the sliding surface of the slider cooperates with the slide groove at the tail of the vehicle. The circumferential probe sensor 5 is installed in the threaded hole below the slider.

[0007] Furthermore, the main assembly of the tail of the vehicle includes the tail of the vehicle, the bottom sandwich plate and the bottom plate which are connected in sequence. The tail of the vehicle, the bottom sandwich plate and the bottom plate respectively have a plurality of bolt mounting threaded holes, through holes and countersunk holes which are circumferentially distributed at a 90° angle. The bottom sandwich plate and the mounting surface of the tail of the vehicle are transitionally matched. The axes of the holes are aligned in sequence and then connected and fixed by countersunk bolts. The side of the bottom sandwich plate has mounting threads which are connected with the inner threaded surface of the tail skirt. After installation, the inner skirt surface of the tail skirt is clearance-matched with the outer end surface of the bottom plate.

[0008] Furthermore, the tail of the navigation body, the bottom sandwich plate and the bottom plate are respectively provided with a plurality of probe sensor guide threaded holes, through holes and probe through holes, which are circumferentially distributed at equal fixed angles with the bolt mounting holes; when a certain measuring point is not needed, the tail threaded hole can be sealed with a bolt.

[0009] Furthermore, the sensor motion sealing assembly includes a small sealing ring and a large sealing ring. A large sealing ring groove is provided at the tail of the navigation body and the bottom sandwich plate respectively, and the large sealing ring is installed to prevent water from entering the interior of the model from the tail skirt during underwater movement; a small sealing ring groove is provided at the lower end surface of the through hole of the bottom sandwich plate and the upper end surface of the probe through hole of the bottom plate, and the small sealing ring is installed and nested on the probe sensor to prevent water from being brought into the interior of the model when the probe of the probe sensor moves back and forth periodically.

[0010] Furthermore, the probe sensor includes a PVDF piezoelectric film, a signal line, a supporting plunger and a hollow tube. The PVDF piezoelectric film is cut into a detection circular surface and leaves a 180° symmetrically distributed terminal margin on both sides. The negative pole of the detection circular surface is insulated and pasted on the plunger support surface, and the terminal surfaces on both sides are bent to form a 90° angle with the circular surface; the plunger is threadedly connected to the hollow tube, the plunger support surface is close to the end face of the hollow tube, and the positive pole of the detection circular surface is insulated and waterproofed to form a pressure sensor probe.

[0011] Furthermore, the positive and negative electrodes at one end of the signal line are respectively welded to the front and back surfaces of the PVDF piezoelectric film terminal, and the other end is connected to the data collector through the wiring groove of the plunger, the wiring hole, the wiring hole of the slider and the wiring hole of the connecting rod in sequence, so as to prevent the signal line from affecting the movement of the follow-up guide assembly.

[0012] Furthermore, when the vehicle model is in the launch tube waiting to be launched, the gravity of the follower guide assembly inside the model is in static balance with the spring support force, and the probe of the probe sensor is located in the through hole of the bottom plate; after the solenoid valve is opened, the high-pressure gas from the gas tank is introduced into the air chamber of the launch tube, and squeezes and drives the vehicle model to overcome the friction of the sealing ring in the tube and the resistance in the water to achieve variable acceleration launch; the follower guide assembly inside the vehicle model simultaneously obtains acceleration pulse excitation, and the linked probe sensor probe extends into the tail cavity and performs periodic reciprocating motion along the axial direction of the model, realizing multi-point follow-up measurement of the pressure inside the bubble.

[0013] A design method for the follower guide assembly specifically includes the following steps:

[0014] S1: First, determine the scale ratio of the vehicle model (small-scale model h:H = 1:40). According to the tail cavitation length to be measured, determine the length of the probe sensor and the spring L = 50 mm. The average outer diameter D, wire diameter d, elastic modulus G of the spring material, and effective number of coils n can all be determined according to the required vibration period, maximum amplitude displacement, etc. The spring stiffness coefficient k is:

[0015]

[0016] S2: Determine the total mass M of the follower mass block, spring support, connecting rod, bolt, slider, and probe sensor. When the vehicle model is in the cylinder waiting to be launched, the gravity of the follower mass block and the spring support force are in static equilibrium, so:

[0017] F t =Mg (2)

[0018] The spring compression in equilibrium is:

[0019]

[0020] By adjusting the mass M of the follower mass m , obtaining different initial compression amounts;

[0021] S3: Based on the input form of the internal ballistic pressure and considering the influence of friction resistance, the acceleration time-varying curve at and internal ballistic related output parameters of the ejection process of the vehicle model are obtained. Based on the time similarity relationship, the time when the vehicle model exits the barrel t1 = 0.17s and the time when it exits the water t2 = 0.23s are determined. Based on the influence of the motion resistance from the vehicle exiting the barrel to underwater, the equivalent slope of the acceleration curve input is determined. The acceleration time-varying curves of the vehicle model exiting the barrel and water are abstractly decomposed into a half-cycle sinusoidal pulse and a decreasing force pulse, and input using different solution methods.

[0022] Among them, in the half-cycle sinusoidal pulse stage,

[0023]

[0024] The underwater cavitation navigation section after the vehicle model leaves the tube is considered as the decreasing force pulse stage.

[0025]

[0026] Where, is the static displacement generated by P0,

[0027] Substitute the above piecewise function into the solution, p(t1) = 7.35N, p(t2) = 2.87N, and calculate the time-varying curve of the relative displacement between the probe and the bottom of the vehicle;

[0028] S4: Use the simple harmonic vibration formula to calculate the motion period T of the follower mass block and probe sensor drive assembly n , so that t1 / T n The value range of is 2-4 to avoid excessive displacement of the spring in the acceleration section in the cylinder or excessive dynamic reaction after leaving the cylinder;

[0029]

[0030] Furthermore, if the working process of the periodic servo test system is regarded as viscous damping vibration, then:

[0031]

[0032] Among them, the damping ratio ζ and the critical damping coefficient are:

[0033]

[0034] When the spring elastic modulus G=12GPa, c cr =57.5; when ζ = 0.05, c = 2.87, at this time,

[0035]

[0036] ω D is the damped vibration natural frequency, and the envelope of the displacement amplitude decaying with time is:

[0037]

[0038] Furthermore, considering the influence of the spring mass on the natural frequency of the system, let the mass of the spring be M s , evenly distributed over the entire spring, the spring is divided into multiple segments, each segment is dx long, and the resulting displacement is The total displacement is Speed is Therefore the kinetic energy of the spring at x is:

[0039]

[0040] The total kinetic energy of the spring is:

[0041]

[0042] Known follower mass So the total kinetic energy of the system is:

[0043]

[0044] The system vibration potential energy is expressed as:

[0045]

[0046] E=E k +E p =const (20)

[0047]

[0048] Will Substituting in and taking the first-order derivative of the above formula at time t, we get:

[0049]

[0050] The natural frequency of the system can be obtained as:

[0051]

[0052] Compared with the prior art, the beneficial effects of the cyclic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle described in the present invention are:

[0053] 1. The present invention can realize multi-point periodic tracking measurement of the internal pressure of the tail cavitation of the water appendage ejected by the navigation body. The multiple monitoring points with wide distribution and variable cross-section can collect the pressure distribution at different positions in the bubble, and at the same time it is convenient to capture the jet return pressure and the fluid micro-cluster disturbance pressure, and has better tolerance for the strong randomness of the jet return splash direction, thereby effectively studying the flow instability problem caused by the multi-order pulsation of the tail cavitation wall and the multiphase flow coupling.

[0054] 2. The present invention can realize the periodic reciprocation of the probe sensor in and out of the tail cavitation with the acceleration pulse excitation obtained when the vehicle is ejected from the tube, thereby solving the problems in the existing pressure testing technology of the tail cavitation of the vehicle ejected from the tube, in which the sensor probe cannot be extended into the bubble and is easily affected by the wall flow field disturbance, or cannot be actively extended and retracted, and the probe is easily damaged by impact.

[0055] 3. The navigation body model assembly of the present invention has strong adaptability and flexibility. Each component can be independently processed and easy to install. The sliding surface of the slider slides in close cooperation with the tail slide groove. The bottom through hole has a guiding effect on the probe sensor. The follow-up guide assembly can adapt to test conditions with multiple ejection conditions such as calm waters and incoming flow disturbances, ensuring that the probe sensor always reciprocates along the axis of the navigation body without oscillation or jamming.

[0056] 4. The probe sensor guide and double-layer sealing structure composed of the tail of the navigation body, the bottom sandwich plate and the bottom plate of the present invention can effectively prevent external water from entering the model from the connection between the components or when the probe sensor moves back and forth, avoiding the risks of sudden changes in model quality, affected movement characteristics, and short-circuit damage to electrical components caused by internal water ingress.

[0057] 5. The tail skirt of the present invention is replaceable. By changing the length of the skirt, experiments can be conducted to investigate the effects of different tail skirt configurations on the characteristics of the tail cavitation flow field and the dynamic evolution of the pressure inside the bubble.

[0058] 6. The probe sensor assembly of the present invention encapsulates the PVDF piezoelectric film, retaining its characteristics of high dynamic response and strong environmental stability, while realizing multi-configuration, low-cost pressure sensor packaging and manufacturing.

[0059] 7. The servo system design method provided by the present invention has strong adaptability to different ejection conditions, multi-scale model structural components and other conditions. It can adjust and design parameters such as springs and mass blocks according to conditions such as model scale ratio and ejection acceleration pulse excitation input, thereby facilitating the similarity test of the flow field and dynamic pressure evolution in the tail bubble of the ejection tube appendage of a multi-scale vehicle model. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0061] Figure 1 This is a structural cross-sectional view of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0062] Figure 2 This is a top view of the structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0063] Figure 3 This is an exploded view of the structural components of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0064] Figure 4 A top view of the tail structure of a vehicle according to the present invention, which is a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle;

[0065] Figure 5 A rotating cross-sectional view of the tail structure CC of a vehicle according to the present invention, which is a periodic follow-up test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle;

[0066] Figure 6 A bottom view of the tail structure of a vehicle according to the present invention, a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle;

[0067] Figure 7 This is a top view of the sandwich plate structure at the bottom of a vehicle body according to the present invention, which is a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation bubble of the vehicle body;

[0068] Figure 8 This is a rotating cross-sectional view of the sandwich plate structure DD at the bottom of a vehicle body, according to a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle body, as described in the present invention;

[0069] Figure 9This is a top view of the bottom plate structure of a vehicle body according to the present invention, which is a periodic servo test system for measuring the internal pressure of the tail cavitation of a vehicle body at multiple points;

[0070] Figure 10 This is a rotating cross-sectional view of the bottom plate structure EE of a vehicle body according to the present invention, which is a periodic servo test system for measuring the internal pressure of the tail cavitation of a vehicle body at multiple points;

[0071] Figure 11 This is a schematic diagram of the structure of a tail skirt of a vehicle according to the present invention, which is a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle;

[0072] Figure 12 This is a schematic diagram of the overall packaging structure of a probe sensor of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0073] Figure 13 This is a cross-sectional view BB of a probe sensor structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0074] Figure 14 This is a schematic diagram of the probe sensor plunger structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0075] Figure 15 This is a schematic diagram of the cutting structure of the PVDF membrane of the probe sensor of the periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0076] Figure 16 This is a top view of the small slider structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0077] Figure 17 This is a sectional view of the small slider structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0078] Figure 18 This is a schematic diagram of the connecting rod structure of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0079] Figure 19 This is a schematic structural diagram of a central slider of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation bubble of a vehicle according to the present invention;

[0080] Figure 20This is a schematic diagram of the overall structure and working principle of a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to the present invention;

[0081] Figure 21 The input of the time-varying curve of the acceleration of the ejected vehicle out of the barrel is a periodic servo test system design method for multi-point measurement of the internal pressure of the tail cavitation of the vehicle described in the present invention;

[0082] Figure 22 Output of a time-varying curve of the relative displacement between the probe and the bottom of the vehicle in the method for designing a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle described in the present invention;

[0083] Figure 23 The invention discloses a method for designing a periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle, which outputs a time-varying curve of the relative displacement between the probe and the bottom under viscous damping.

[0084] In the figure: 1 - tail of the vehicle; 2 - bottom sandwich plate; 3 - bottom plate; 4 - tail skirt; 5 - probe sensor; 6 - spring; 7 - spring support; 8 - slider; 9 - connecting bolt; 10 - connecting rod; 11 - follower mass block; 12 - small sealing ring; 13 - large sealing ring; 14 - vehicle model body; 15 - data collector; 16 - launch tube; 17 - sealing ring inside the tube; 18 - air chamber inside the tube; 19 - solenoid valve; 20 - high-pressure gas tank;

[0085] 1-1 - Slider slot; 1-2 - Probe threaded through hole; 1-3 - Sandwich panel mounting mating surface; 1-4 - Threaded hole; 1-5 - Large sealing ring groove;

[0086] 2-1-No. 1 probe through hole; 2-2-Bolt mounting through hole; 2-3-Tail skirt mounting thread; 2-4-Small sealing ring groove; 2-5-Large sealing ring groove;

[0087] 3-1-No. 2 probe through hole; 3-2-countersunk bolt hole; 3-3-outer end surface; 3-4-small sealing ring groove;

[0088] 4-1-Mounting thread; 4-2-Skirt;

[0089] 501-hollow tube; 502-support plunger; 503-signal line; 504-PVDF piezoelectric film;

[0090] 501-1-Mounting thread; 501-2-Wire duct;

[0091] 502-1 - Wire duct; 502-2 - Wire hole; 502-3 - Support surface; 502-4 - Mounting thread;

[0092] 504-1- detection circular surface; 504-2- terminal; 504-3- PVDF membrane positive electrode; 504-4- PVDF membrane negative electrode;

[0093] 8-1 - Connecting rod mounting slot; 8-2 - Threaded hole; 8-3 - Sliding surface; 8-4 - Probe mounting threaded hole; 8-5 - Wiring hole;

[0094] 10-1-Connecting rod mounting block; 10-2-Through hole; 10-3-Threading hole;

[0095] 11-1-Connecting rod mounting slot; 11-2-Threaded hole; 11-3-Support mounting thread. DETAILED DESCRIPTION

[0096] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict, and the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0097] See also Figure 1-23 To describe this embodiment, a periodic follow-up test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle comprises a tail main body assembly of the vehicle, a follow-up guide assembly, a probe sensor assembly, and a sensor motion sealing assembly; the probe sensor assembly is installed in the tail main body assembly of the vehicle through the follow-up guide assembly, and is sealed by the sensor motion sealing assembly; when the vehicle is ejected from the tube, the spring and the follow-up assembly are excited by the acceleration pulse to drive multiple probe sensors to extend from the bottom into the tail cavitation to obtain the internal pressure and perform periodic reciprocating motion.

[0098] The probe sensor assembly includes multiple probe sensors 5, and the follower guide assembly consists of a spring 6, a spring support 7, a follower mass block 11, a connecting rod 10 and a slider 8. The probe sensor 5 at the center axis of the model is installed in the threaded hole of the spring support 7, and the probe end passes through the hole 2-1 in the bottom sandwich plate and the hole 3-1 in the bottom plate in sequence; the spring 6 is sleeved on the outside of the probe sensor 5 located in the center, and the two ends are respectively connected to the bottom sandwich plate 2 and the mounting hole end face of the spring support 7, and the spring support 7 and the threaded surface 11 below the follower mass block 11 -3 is installed in cooperation; the two ends of the connecting rod 10 are respectively connected to the follower mass block 11 and the slider 8 by bolts 9, the slider sliding surface 8-3 cooperates with the slide groove 1-1 of the tail 1 of the navigation body, and the circumferential probe sensor 5 is installed in the threaded hole 8-4 below the slider 8, and the probe end passes through the tail threaded through hole 1-2, the bottom sandwich plate through hole 2-1 and the bottom plate through hole 3-1 in sequence; the probe sensor 5 is driven by the spring 6 and the mass block 11, and is guided by the through holes, the slider sliding surface 8-3 and the tail slide groove 1-1 to realize periodic reciprocating motion along the axial direction of the navigation body.

[0099] In this embodiment, only the probe sensor 5 at the center is provided with a spring 6 , and one spring drives the entire slider and the probe sensor to perform periodic reciprocating motion.

[0100] Implementation method 2: See Figure 2-10 To illustrate this embodiment, the main assembly of the tail of the vehicle is composed of a tail of the vehicle 1, a bottom sandwich plate 2, a bottom plate 3 and a tail skirt 4 connected in sequence. The tail of the vehicle 1, the bottom sandwich plate 2 and the bottom plate 3 are respectively provided with 4 bolt mounting threaded holes 1-4, through holes 2-2 and countersunk holes 3-2, which are circumferentially distributed at an angle of 90°. The bottom sandwich plate 2 is transitionally matched with the mounting surface 1-3 of the tail of the vehicle, and the axes of the holes are aligned in sequence and then connected and fixed by countersunk bolts 9. The side of the bottom sandwich plate 2 is provided with mounting threads 2-3, which are connected with the internal threaded surface 4-1 of the tail skirt 4. After installation, the inner skirt surface 4-2 of the tail skirt is clearance-matched with the outer end surface 3-3 of the bottom plate.

[0101] Implementation method three: See Figure 4-10 To illustrate this embodiment, the tail 1 of the navigation body, the bottom sandwich plate 2 and the bottom plate 3 are respectively provided with four probe sensor guide threaded holes 1-2, a through hole 2-1 and a probe through hole 3-1, which are circumferentially distributed at an angle of 45° to the bolt mounting holes. When a certain measuring point is not needed, the tail threaded hole 1-2 can be sealed with a bolt. If more measuring points are required, the number of probes can be increased to 8, 12, etc. by referring to the above-mentioned follow-up guide component structure design method.

[0102] Implementation 4: See Figure 4-10 To illustrate this embodiment, the tail portion 1 of the navigation body and the bottom sandwich plate 2 are respectively provided with a large sealing ring groove 1-5, and a large sealing ring 13 is installed to prevent water from entering the interior of the model from the tail skirt 4 during underwater movement; the lower end surface of the through hole of the bottom sandwich plate 2 and the upper end surface of the probe through hole of the bottom plate 3 are provided with small sealing ring grooves 2-4, and a small sealing ring 12 is installed and nested on the probe sensor 5 to prevent water from being brought into the interior of the model when the probe moves back and forth periodically.

[0103] Implementation 5: See Figure 11 To illustrate this embodiment, the tail skirt 4 is a replaceable part. By changing the length of the skirt surface 4-2, experiments can be carried out to explore the effects of different tail skirt configurations on the tail cavitation flow field characteristics and the dynamic evolution of the pressure inside the bubble.

[0104] Implementation method six: See Figure 12-15To illustrate this embodiment, the probe sensor 5 is composed of a PVDF piezoelectric film 504, a plunger 502 and a hollow tube 501 package. The PVDF piezoelectric film 504 is cut into a circular shape 504-1 and has a 180° symmetrically distributed terminal 504-2 margin on both sides. The negative electrode 504-4 of the detection circular surface is insulated and glued to the support surface of the plunger, and the double-sided terminal surfaces 504-2 are bent to form a 90° angle with the circular surface 504-1; the plunger 502 is threadedly connected to the hollow tube 501, and the support surface 502-3 is close to the end surface of the hollow tube. The positive electrode 504-3 of the detection circular surface is insulated and waterproofed to form a pressure sensor probe.

[0105] In addition, the PVDF piezoelectric film 504 is equivalent to a pressure sensor and can be replaced by an acceleration sensor. The acceleration sensor is packaged with the hollow tube 501 to synchronously monitor the impact load and movement state of the follow-up guide assembly.

[0106] Implementation method seven: See Figure 12-19 To illustrate this embodiment, the positive and negative electrodes at one end of the signal line 503 are respectively welded to the front and back surfaces of the PVDF piezoelectric film terminal 504-2, and the other end is connected to the data collector 15 through the wiring groove 502-1 of the plunger, the wiring hole 502-2, the wiring hole 8-5 of the slider and the wire hole 10-3 of the connecting rod in sequence, so as to prevent the signal line 503 from affecting the movement of the follow-up guide assembly.

[0107] Implementation 8: See Figure 20 To illustrate this embodiment, when the vehicle model 14 is in the launch tube 16 to be launched, the gravity of the follower guide assembly inside the model 14 is in static equilibrium with the supporting force of the spring 6, and the probe of the probe sensor 5 is located in the through hole 3-1 of the base plate 3; after the solenoid valve 19 is opened, the high-pressure gas from the gas tank 20 is introduced into the launch tube air chamber 18, and squeezes and drives the vehicle model 14 to overcome the friction of the sealing ring 17 in the tube and the resistance in the water to achieve variable acceleration launch; the follower guide assembly inside the model 14 simultaneously obtains acceleration pulse excitation, and the probe of the linked probe sensor 5 extends into the tail cavity and performs periodic reciprocating motion along the axial direction of the model, thereby realizing multi-point follow-up measurement of the pressure inside the bubble.

[0108] Implementation method nine: See Figure 18 In this embodiment, the distance L between the end faces of the two mounting blocks 10-1 of the connecting rod 10 is l It is adjustable, thereby changing the relative position of the corresponding probe sensor 5 probe and the bottom 3 of the vehicle and other probes, and realizing the pressure tracking measurement of different tail cavitation distance sections in a single-shot test.

[0109] Implementation Method 10: See Figure 20 To illustrate this embodiment, the design method of the follower guide assembly is as follows:

[0110] S1: First, determine the scale ratio of the vehicle model 14 (small-scale model h:H=1:40). According to the tail cavitation length to be measured, determine the length L of the probe sensor 5 and the spring 6 = 50 mm. The average outer diameter D, wire diameter d, elastic modulus G of the spring material, and effective number of turns n of the spring 6 can all be determined according to the required vibration period, maximum amplitude displacement, etc. The stiffness coefficient k of the spring 6 is:

[0111]

[0112] S2: Determine the total mass M of the follower mass block 11, spring support 7, connecting rod 10, bolt 9, slider 8, and probe sensor 5. When the model 14 is in the barrel to be launched, the gravity of the follower mass block 11 and other driving components is in static equilibrium with the support force of the spring 6. Then:

[0113] F t =Mg (2)

[0114] The compression amount of spring 6 in the equilibrium state is:

[0115]

[0116] By adjusting the mass M of the mass block 11 m , different initial compression amounts can be obtained.

[0117] S3: According to the input form of the internal ballistic pressure, taking into account the influencing factors such as friction resistance, the acceleration time-varying curve at of the ejection process of the vehicle model 14 and the internal ballistic related output parameters are obtained. According to the time similarity relationship, the time when the vehicle 14 exits the tube t1 = 0.17s and the time when it exits the water t2 = 0.23s are determined. According to the influence of the vehicle's motion resistance from the tube to underwater, the equivalent slope of the acceleration curve input is determined; the acceleration time-varying curve of the vehicle model 14 exiting the tube and the water is abstractly decomposed into a half-cycle sinusoidal pulse and a decreasing force pulse, and input using different solution methods, such as Figure 21 shown.

[0118] Among them, in the half-cycle sinusoidal pulse stage,

[0119]

[0120] The underwater cavitation section of the model 14 after leaving the tube is considered as the decreasing force pulse stage.

[0121]

[0122] Where, is the static displacement generated by P0.

[0123] Substitute the above piecewise function into the solution, p(t1) = 7.35N, p(t2) = 2.87N, and the calculated relative displacement time-varying curve between the probe and the bottom of the vehicle is as follows: Figure 22 shown.

[0124] S4: Calculate the motion period T of the follower mass block 11 and the probe sensor 5 drive assembly using the simple harmonic vibration formula n , so that t1 / T n The value range of is 2-4 to avoid excessive displacement of the spring in the acceleration section in the cylinder or excessive dynamic reaction after leaving the cylinder;

[0125]

[0126] Implementation method eleven: See Figure 23 To illustrate this embodiment, consider the operation of the various components of the servo test system. On the one hand, the relative motion of the slider 8 and the chute 1-1, and the probe sensor 5 and the small sealing ring 12, generates a certain amount of friction. On the other hand, the probe 5 experiences resistance from the low-pressure gas, then the high-pressure gas, and finally the mixture of high-pressure gas and water vapor. Therefore, the entire servo system operation process can be considered as viscous damped vibration (an underdamped system). Thus:

[0127]

[0128] Among them, the damping ratio ζ and the critical damping coefficient are:

[0129]

[0130] When the spring elastic modulus G=12GPa, c cr =57.5; when ζ = 0.05, c = 2.87, at this time,

[0131]

[0132] ω D is the damped vibration natural frequency, and the envelope of the displacement amplitude decaying with time is:

[0133]

[0134] Implementation 12: Considering the influence of the spring mass on the natural frequency of the system, let the mass of the spring 6 be M s , evenly distributed over the entire spring. Because the spring has mass, it has kinetic energy when vibrating, so its velocity distribution needs to be analyzed. Divide the spring into multiple segments, each of length dx, and the resulting displacement is The total displacement is Speed is Therefore the kinetic energy of the spring at x is:

[0135]

[0136] The total kinetic energy of the spring is:

[0137]

[0138] Known follower mass So the total kinetic energy of the system is:

[0139]

[0140] The system vibration potential energy is expressed as:

[0141]

[0142] E=E k +E p =const (20)

[0143]

[0144] Will Substituting in and taking the first-order derivative of the above formula at time t, we get:

[0145]

[0146] The natural frequency of the system can be obtained as:

[0147]

[0148] It can be seen that after considering the mass of the spring 6, the natural frequency response of the system is reduced. However, since the mass of the spring is relatively small, the impact on the natural frequency of the system can be ignored.

[0149] The embodiments of the present invention disclosed above are intended only to illustrate the present invention. The embodiments do not describe all details in detail, nor do they limit the present invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle, characterized by: The vehicle comprises a tail main body assembly, a follower guide assembly, a probe sensor assembly, and a sensor motion sealing assembly; the probe sensor assembly is installed in the tail main body assembly of the vehicle through the follower guide assembly and is sealed by the sensor motion sealing assembly; The probe sensor assembly includes a plurality of probe sensors (5), and the follower guide assembly includes a spring (6), a spring support (7), a follower mass block (11), a connecting rod (10) and a slider (8). The probe sensor (5) is installed in the threaded hole of the spring support (7), and the probe end passes through the bottom sandwich plate (2) and the bottom plate (3) in sequence. The spring (6) is sleeved on the outside of the probe sensor (5) located in the middle, and the two ends are respectively connected to the bottom sandwich plate (2) and the mounting hole end face of the spring support (7). The spring support (7) is installed in cooperation with the threaded surface (11-3) below the follower mass block (11); the two ends of the connecting rod (10) are respectively connected to the follower mass block (11) and the slider (8) through bolts (9). The slider sliding surface (8-3) of the slider (8) is matched with the slide groove (1-1) of the tail of the vehicle (1). The circumferential probe sensor (5) is installed in the threaded hole (8-4) below the slider (8).

2. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 1 is characterized in that: The tail main body component of the navigation body includes a navigation body tail (1), a bottom sandwich plate (2) and a bottom plate (3) connected in sequence. The navigation body tail (1), the bottom sandwich plate (2) and the bottom plate (3) are respectively provided with a plurality of bolt mounting threaded holes (1-4), through holes (2-2) and countersunk holes (3-2), which are circumferentially distributed at an angle of 90 degrees. The bottom sandwich plate (2) and the navigation body tail mounting surface (1-3) are transitionally matched. The axes of the holes are aligned in sequence and then connected and fixed by countersunk bolts (9). The side surface of the bottom sandwich plate (2) is provided with mounting threads (2-3), which are matched and connected with the internal thread surface (4-1) of the tail skirt (4). After installation, the inner skirt surface (4-2) of the tail skirt and the outer end surface (3-3) of the bottom plate are clearance-matched.

3. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 2 is characterized in that: The tail (1), bottom sandwich plate (2) and bottom plate (3) of the navigation body are respectively provided with a plurality of probe sensor guide threaded holes (1-2), through holes (2-1) and probe through holes (3-1), and are respectively distributed circumferentially at equal fixed angles with the bolt mounting holes; when a certain measuring point is not needed, the tail threaded hole (1-2) can be blocked with a bolt.

4. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 1 is characterized in that: The sensor motion sealing assembly comprises a small sealing ring (12) and a large sealing ring (13); a large sealing ring groove (1-5) is respectively provided on the tail portion (1) of the navigation body and the bottom sandwich plate (2); the large sealing ring (13) is installed to prevent water from entering the interior of the model from the tail skirt (4) during underwater movement; a small sealing ring groove (2-4) is provided on the lower end surface of the through hole of the bottom sandwich plate (2) and the upper end surface of the probe through hole of the bottom plate (3); the small sealing ring (12) is installed and nested on the probe sensor (5) to prevent water from entering the interior of the model when the probe of the probe sensor (5) moves back and forth periodically.

5. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 1 is characterized in that: The probe sensor (5) comprises a PVDF piezoelectric film (504), a signal line (503), a supporting plunger (502) and a hollow tube (501); the PVDF piezoelectric film (504) is cut into a detection circular surface (504-1) and has a margin of connection terminals (504-2) symmetrically distributed at 180° on both sides; the negative electrode (504-4) of the detection circular surface is insulated and adhered to the plunger support surface (502-3); the connection terminals (504-2) on both sides are bent to form an angle of 90° with the detection circular surface (504-1); the supporting plunger (502) is threadedly connected to the hollow tube (501); the plunger support surface (502-3) is in close contact with the end face of the hollow tube; and the positive electrode (504-3) of the detection circular surface is insulated and waterproofed to form a pressure sensor probe.

6. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 5, characterized in that: The positive and negative electrodes at one end of the signal line (503) are respectively welded to the front and back surfaces of the PVDF piezoelectric film terminal (504-2), and the other end is connected to the data acquisition device (15) through the wiring groove (502-1) of the support plunger (502), the wiring hole (502-2), the wiring hole (8-5) of the slider (8) and the threading hole (10-3) of the connecting rod (10) in sequence, so as to prevent the signal line (503) from affecting the movement of the follower guide component.

7. The periodic servo test system for multi-point measurement of the internal pressure of the tail cavitation of a vehicle according to claim 1 is characterized in that: When the navigation body model (14) is in the launch tube (16) and is ready to be launched, the gravity of the follower guide assembly inside the navigation body model (14) is in static equilibrium with the support force of the spring (6), and the probe of the probe sensor (5) is located in the through hole (3-1) of the bottom plate (3); after the electromagnetic valve (19) is opened, the high-pressure gas from the gas storage tank (20) is introduced into the launch tube air chamber (18), and squeezes and drives the navigation body model (14) to overcome the friction force of the sealing ring (17) in the tube and the resistance in the water to achieve variable acceleration launch; the follower guide assembly inside the navigation body model (14) is simultaneously excited by the acceleration pulse, and the probe of the linkage probe sensor (5) is extended into the tail cavity and performs periodic reciprocating motion along the axial direction of the model, thereby realizing multi-point follow-up measurement of the pressure inside the bubble.

8. A design method for a follower guide assembly according to claim 1, characterized in that: The specific steps include: S1: First, determine the scale ratio of the vehicle model (14). The length L of the probe sensor (5) and the spring (6) is determined according to the tail cavitation length to be measured. The average outer diameter D, wire diameter d, elastic modulus G of the spring material, and effective number of turns n of the spring (6) are all determined according to the required vibration period and maximum amplitude displacement. The stiffness coefficient k of the spring (6) is: S2: Determine the total mass M of the follower mass block (11), the spring support (7), the connecting rod (10), the bolt (9), the slider (8) and the probe sensor (5). When the vehicle model (14) is in the cylinder to be launched, the gravity of the follower mass block (11) and the supporting force of the spring (6) are in static equilibrium, and then: F t =Mg (2) The compression of the spring (6) in the equilibrium state is: By adjusting the mass M of the follower mass block (11) m , obtaining different initial compression amounts; S3: According to the input form of the internal ballistic pressure, considering the influence of friction resistance, the acceleration time-varying curve at of the ejection process of the navigation body model (14) and the internal ballistic related output parameters are obtained. According to the time similarity relationship, the time t1=0.17s and the time t2=0.23s of the navigation body model (14) out of the tube are determined. According to the influence of the movement resistance of the navigation body from the tube to the underwater, the equivalent slope of the acceleration curve input is determined. The acceleration time-varying curve of the navigation body model (14) out of the tube and out of the water is abstractly decomposed into a half-cycle sine pulse and a decreasing force pulse, and inputted using different solution methods. Among them, in the half-cycle sinusoidal pulse stage, The underwater cavitation section of the model 14 after leaving the tube is considered as the decreasing force pulse stage. Where, is the static displacement generated by P0, Substitute the above piecewise function into the solution, p(t1) = 7.35N, p(t2) = 2.87N, and calculate the time-varying curve of the relative displacement between the probe and the bottom of the vehicle; S4: Use the simple harmonic vibration formula to calculate the motion period T of the follower mass block (11) and the probe sensor (5) drive assembly n , so that t1 / T n The value range of is 2-4 to avoid excessive displacement of the spring in the acceleration section in the cylinder or excessive dynamic reaction after leaving the cylinder; 9. The design method of the follower guide assembly according to claim 8, characterized in that: Considering the working process of the periodic servo test system as viscous damped vibration, then: Among them, the damping ratio ζ and the critical damping coefficient are: When the spring elastic modulus G=12GPa, c cr =57.5; when ζ = 0.05, c = 2.87, at this time, ω D is the damped vibration natural frequency, and the envelope of the displacement amplitude decaying with time is:

10. The design method of the follower guide assembly according to claim 8, characterized in that: Considering the influence of the mass of spring (6) on the natural frequency of the system, let the mass of spring (6) be M s , evenly distributed over the entire spring, the spring is divided into multiple segments, each segment is dx long, and the resulting displacement is The total displacement is Speed is Therefore, the kinetic energy of spring (6) at x is: The total kinetic energy of spring (6) is: The known follower mass (11) So the total kinetic energy of the system is: The system vibration potential energy is expressed as: E=E k +E p =const (20) Will Substituting in and taking the first-order derivative of the above formula at time t, we get: The natural frequency of the system can be obtained as:

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