High-speed water entry impact test system and test method

Abstract

The invention discloses a high-speed water-entry impact test system and a high-speed water-entry impact test method. The test system comprises a carbon dioxide phase change acceleration module and a test structure assembly. The test structure assembly comprises an air cylinder, a piston rod assembly, an electromagnetic chuck and a counterweight limiting plate. A pressure sensor and a high-speed camera are mounted in a test structure falling area in the test water tank, and a temperature sensor is mounted in the carbon dioxide phase change acceleration module; in an initial state, the electromagnetic chuck fixes the counterweight limiting plate, the piston rod assembly and the test structure body at initial positions; when the test is started and the test structure body does not enter water, the counterweight limiting plate, the piston rod assembly and the test structure body move downwards in an accelerated manner until the test structure body is accelerated to a target speed; and when the test structural body enters water, the gas in the cylinder releases pressure and stops accelerating the test structural body, and the test structural body falls into the water body of the test water tank at a target speed. High-speed water entry of the structure can be achieved without a high water entry height.

Description

Technical Field

[0001] The present invention relates to a structural water-entry impact test, and specifically to a high-speed water-entry impact test system and a test method. Background Art

[0002] When a structure enters the water, it inevitably undergoes a violent relative impact with the water surface. In a short time, the structure will be subjected to a huge impact pressure, which will cause large plastic deformation or even damage to the local structure. Especially when the water-entry structure enters the water obliquely and the reaction force of the water does not pass through the center of gravity of the water-entry structure, a moment around the center of gravity will be generated, and it will shake under the action of hydrodynamic forces, affecting the stability of the water-entry structure and posing a serious threat to the reliability and safety of the overall structure. Therefore, there is an urgent need to carry out high-speed water-entry impact research.

[0003] Chinese Patent Application CN116558761A discloses a high-speed water-entry impact test device for a structure based on spring acceleration. It pre-accelerates the water-entry test structure through a set spring acceleration module and then accelerates it using gravity to achieve high-speed water-entry impact of the structure. However, this spring acceleration module is limited by the spring force and the effective action length of the spring, and it is difficult to meet the requirements of the indoor height of a conventional laboratory for the water-entry height while ensuring a relatively high water-entry speed. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a high-speed water-entry impact test system and a test method that can be carried out in a laboratory.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A high-speed water-entry impact test system includes a test bench and a test water tank. The test bench is erected above the test water tank, and a carbon dioxide phase change acceleration module and a test structure assembly are installed on the test bench. Among them:

[0007] The carbon dioxide phase change acceleration module is used to generate high-pressure carbon dioxide mixed gas through carbon dioxide phase change. The carbon dioxide phase change acceleration module includes at least one phase change tube and a pressure equalizing chamber, and each phase change tube is connected to the pressure equalizing chamber in chronological order;

[0008] The test structure assembly includes:

[0009] A cylinder, inside which a piston rod assembly is installed. The piston rod assembly includes a piston and a push rod. The piston divides the inner cavity of the cylinder along the axial direction of the cylinder into a first chamber and a second chamber. The first chamber is connected to the air outlet of the pressure equalizing chamber of the carbon dioxide phase change acceleration module. The push rod is installed in the second chamber. One end of the push rod is connected to the piston, and the other end extends out of the second chamber and is connected to the test structure body;

[0010] An electromagnetic chuck for fixing the initial position of the test structure body;

[0011] A counterweight limit plate is slidably mounted on the push rod, and is attracted to the electromagnetic chuck, and a counterweight installation area for installing a counterweight is provided on the counterweight limit plate;

[0012] A pressure sensor for monitoring the change of water pressure in the test water tank and a high-speed camera for monitoring the water entry speed, water entry angle and the change of the surface of the test structure body during the underwater movement process are installed near the falling area of the test structure body in the test water tank. A temperature sensor is installed in the carbon dioxide phase change acceleration module for monitoring the temperature of the high-pressure carbon dioxide mixture gas;

[0013] In the initial state, the electromagnetic chuck fixes the counterweight limit plate, the piston rod assembly and the test structure body at the initial position;

[0014] After the test starts and before the test structure body enters the water, under the action of the gas output by the carbon dioxide phase change acceleration module, the counterweight limit plate, the piston rod assembly and the test structure body move downward with acceleration until the test structure body accelerates to the target speed;

[0015] When the test structure body enters the water, the gas in the cylinder is depressurized and the acceleration of the test structure body stops. The test structure body falls into the water body of the test water tank at the target speed. At the same time, the pressure sensor monitors the water pressure when the test structure body enters the water, and the high-speed camera monitors the water entry speed, water entry angle and the change of the surface of the test structure body.

[0016] Preferably, the test structure assembly further includes a guide rail installed on the test bench, and the counterweight limit plate is slidably mounted on the guide rail.

[0017] Preferably, a spring buffer is installed at the bottom of the guide rail, and the spring buffer is installed at the end of the stroke of the counterweight limit plate.

[0018] Preferably, an angle adjustment unit is installed between the counterweight limit plate and the test structure body. The angle adjustment unit includes a plurality of angle adjustment bolts installed around the push rod. The head of the angle adjustment bolt is placed on the upper surface of the counterweight limit plate and fastened with a fixing nut. The screw part of the angle adjustment bolt passes through the counterweight limit plate and is rotatably connected to the test structure body.

[0019] Preferably, a pressure relief hole area is provided at the lower end of the second chamber of the cylinder, and a plurality of pressure relief holes are distributed in the pressure relief hole area. During the process of the test structure body entering the water, the piston of the piston rod assembly moves to the pressure relief hole area.

[0020] Preferably, a phase change module fixing layer, an electromagnetic adsorption layer, a test buffer braking layer and a base are sequentially arranged on the test bench from top to bottom. The carbon dioxide phase change acceleration module is installed above the phase change module fixing layer, and the cylinder is installed below it. The electromagnetic chuck is fixedly installed at the bottom of the electromagnetic adsorption layer. The weight limiting plate is installed between the electromagnetic adsorption layer and the test buffer braking layer. The base is placed in the test water tank.

[0021] Based on the same inventive concept, the present invention also provides a test method for the high-speed water entry impact test system, which includes the following steps: 1). According to the actual water entry speed requirement of the test structure, calculate the pressure P(t) of the high-pressure carbon dioxide mixed gas required in the cylinder, so as to determine the number of phase change tubes of the carbon dioxide phase change acceleration module and the release time interval of multiple phase change tubes , where: The relationship between the pressure P(t) in the cylinder, the inner diameter D of the cylinder, the effective actuation stroke L of the cylinder, and the water entry speed of the test structure is as follows: , , In the formula is the total mass of the piston rod assembly, the angle adjustment bolt, and the weight limiting plate, with the unit of kg; is the mass of the test structure, with the unit of kg; D is the inner diameter of the cylinder, with the unit of mm; P(t) is the pressure at time t in the cylinder, with the unit of MPa; L is the effective actuation stroke of the cylinder, with the unit of m; g is the acceleration due to gravity, with the unit of m / s²; 2). Install the test structure below the weight limiting plate and set the water entry angle; 3). Connect the initial position maintaining module of the water entry structure to the weight limiting plate to fix the weight limiting plate, the test structure, and the piston rod assembly in the initial position; 4). The high-speed camera, pressure sensor, and temperature sensor start collecting data; 5). Connect the carbon dioxide phase change acceleration module to an external power supply and release the high-pressure carbon dioxide mixed gas. The high-pressure carbon dioxide mixed gas is instantly released into the cylinder and generates a thrust on the piston rod assembly. Under the thrust of the piston rod assembly, the weight limiting plate disengages from the initial position maintaining module of the water entry structure, and the weight limiting plate, the piston rod assembly, and the test structure accelerate downward together under the action of the high-pressure carbon dioxide mixed gas; 6). After the test structure accelerates to the target speed, it enters the water. During the water entry process of the test structure, the cylinder is depressurized, and the test structure stops accelerating; 7), The high-speed camera, pressure sensor, and temperature sensor stop collecting data, and the test ends.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention reduces the implementation difficulty and test cost of high-speed water entry of the structure. By using the liquid-gas phase change of carbon dioxide to provide a high-pressure gas source, it realizes the short-distance acceleration of the test structure and high-speed water entry. 2) The present invention can accurately determine the water entry speed of the test structure through the number of phase change tubes and the release time interval of the carbon dioxide phase change acceleration module. 3) The present invention can achieve the rapid braking of the test structure through the reasonable arrangement of the pressure relief holes and the setting of the spring buffer. 4) The high-speed water entry impact test system developed by the present invention can achieve high-speed water entry of the structure without a high water entry height, with low implementation difficulty and low test investment cost. It can provide test and verification for the high-speed water entry impact of the structure in the above application scenarios in the laboratory, which has great engineering significance for the design of the structure's anti-water surface impact protection and ensuring the structural safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the overall structure of the test system of the present invention; Figure 2 It is a schematic diagram of the structure of the carbon dioxide phase change acceleration module of the present invention; Figure 3 It is a schematic diagram of the test structure assembly of the present invention; Figure 4 It is a schematic diagram of the internal structure layout of the present invention; Figure 5 It is a schematic diagram of the layout of the counterweight limit plate of the present invention; Figure 6 It is a schematic diagram of the layout of the test components of the present invention.

[0025] In the figure: 1. Carbon dioxide phase change acceleration module, 11. Equal pressure chamber, 12. Phase change tube; 2. Diaphragm valve; 31. Cylinder, 32. Piston rod assembly, 33. Electromagnetic chuck, 34. Counterweight limit plate, 35. Angle adjustment bolt, 36. Guide rail, 37. Spring buffer, 38. Test structure body, 311. First chamber, 312. Second chamber, 313. Pressure relief hole, 321. Push rod, 322. Piston, 341. Guide hole, 342. Angle adjustment bolt through hole, 343. Piston rod assembly through hole, 344. Electromagnetic chuck action area, 345. Counterweight installation area, 351. Screw part, 352. Fixed ring, 353. Fixed nut; 4. Test bench, 41. Phase change module fixing layer, 42. Electromagnetic adsorption layer, 43. Test buffer braking layer, 44. Base; 5. Test component, 51. High-speed camera, 52. Acquisition terminal, 53. Pressure sensor; 6. Test water tank. Specific implementation mode

[0026] The present invention will be further described below in conjunction with specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0027] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0029] Such as Figure 1As shown in the figure, an embodiment of the high-speed water-entry impact test system of the present invention includes a carbon dioxide phase change acceleration module 1, a diaphragm valve 2, a test structure assembly 3, a test bench 4, a test component 5, and a test water tank 6. The carbon dioxide phase change acceleration module 1 is installed on the top of the test bench 4 and is used to generate high-pressure carbon dioxide mixed gas through the phase change of carbon dioxide (generating high-pressure carbon dioxide mixed gas through the phase change of carbon dioxide is a prior art, for example, Chinese Patent Application CN111457787A specifically introduces it); the carbon dioxide phase change acceleration module 1 is connected to the test structure assembly 3 through the diaphragm valve 2; the test structure assembly 3 is installed on the test bench 4; a test water tank 6 is arranged below the test structure assembly 3, and the test structure assembly 3 moves downward at high speed under the action of the high-pressure carbon dioxide mixed gas released by the carbon dioxide phase change acceleration module 1; a test component 5 is arranged in the test water tank 6, and the test component 5 is used to detect the water-entry speed and impact pressure of the test structure assembly 3.

[0030] As Figure 2 shown, the carbon dioxide phase change acceleration module 1 includes a pressure equalizing chamber 11 and at least one phase change tube 12 communicated with the pressure equalizing chamber 11. The phase change tube 12 is used to generate high-pressure carbon dioxide mixed gas through the liquid-gas phase change of liquid carbon dioxide, and each phase change tube 12 releases high-pressure carbon dioxide mixed gas into the pressure equalizing chamber 11 in chronological order.

[0031] The diaphragm valve 2 remains closed during the test preparation process. At the start of the test, the pressure of the high-pressure carbon dioxide mixed gas released by the phase change tube 12 of the carbon dioxide phase change acceleration module 1 enters the pressure equalizing chamber 11. When the pressure of the pressure-equalized high-pressure carbon dioxide mixed gas exceeds the pressure threshold of the diaphragm valve 2, the diaphragm valve 2 automatically opens, and the high-pressure carbon dioxide mixed gas enters the cylinder 31 to push the piston rod assembly 32 to move downward.

[0032] As Figure 3 、 Figure 4 shown, the test structure assembly 3 includes a cylinder 31, a piston rod assembly 32, an electromagnetic chuck 33, a weight limiting plate 34, an angle adjusting bolt 35, a guide rail 36, a spring buffer 37, and a test structure body 38. The cylinder 31 is vertically installed downward on the test bench 4, and the piston rod assembly 32 is installed inside the cylinder 31. The piston rod assembly 32 includes a piston 322 and a push rod 321. The piston 322 divides the inner cavity of the cylinder along the axial direction of the cylinder into a first chamber 311 and a second chamber 312. The first chamber 311 is connected to the air outlet of the pressure equalizing chamber 11 of the carbon dioxide phase change acceleration module 1, and the push rod is installed. One end of the push rod 321 extends into the second chamber 312 and is connected to the piston 322. The other end of the push rod 321 penetrates through the weight limiting plate 34 and is rotatably connected to the middle part of the test structure body 38. When the push rod 321 moves downward, the test structure body 38 can drive the weight limiting plate 34 to move up and down along the axial direction of the cylinder 31 together.

[0033] The guide rail 36 is vertically installed on the test bench 4. The counterweight limit plate 34 is slidably installed on the guide rail 36. A spring buffer 37 is installed at the bottom of the guide rail 36. When the counterweight limit plate 34 moves downward into the water along the guide rail 36, the stroke finally lands on the spring buffer 37, and buffering and limiting are achieved through the spring buffer 37.

[0034] A pressure relief hole 313 is provided in the lower end area of the second chamber 312 of the air cylinder 31. During the process of the test structure body 38 entering the water, when the piston 322 moves to the area of the pressure relief hole 313, the gas in the first chamber 311 of the air cylinder 31 is quickly released from the pressure relief hole 313, stopping the acceleration of the movement of the test structure body 38, so that the test structure body 38 is in a freely up-and-down state after entering the water.

[0035] During the test process, the piston 322 slides axially and sealingly in the air cylinder 31. The piston 322 plays a guiding role to make the push rod 321 move along the axis of the air cylinder 31. The push rod 321 pushes the test structure body 38 downward to accelerate the movement until it stops accelerating rapidly after reaching the horizontal plane, so that the test structure body 38 is in a freely up-and-down state after entering the water.

[0036] The test component 5 includes a high-speed camera 51, a collection terminal 52, a pressure sensor 53, and a temperature sensor (not shown in the figure). The high-speed camera 51 is used to photograph the water entry speed of the test structure body 38 and transmit it to the collection terminal 52. The temperature sensor is arranged in the carbon dioxide phase change acceleration module 1 to monitor the temperature of the high-pressure carbon dioxide mixed gas. The pressure sensor 53 is arranged in the test water tank 6 to collect the water pressure data in the test water tank 6 and transmit it to the collection terminal 52. The collection terminal 52 is connected to the high-speed camera 51, the pressure sensor 53, and the temperature sensor. By receiving the water entry speed obtained by the high-speed camera 51, the pressure data collected by the pressure sensor 53, and the temperature data collected by the temperature sensor, and performing corresponding analysis and calculation (this part is the prior art), the relevant data of the test structure body 38 at different times can be obtained.

[0037] As Figure 5 shown, for the convenience of installing the counterweight limit plate 34, guide holes 341 are provided at the four corners of the counterweight limit plate 34. The counterweight limit plate 34 is slidably installed on the guide rail 36 through the guide holes 341. In addition, an angle adjustment bolt through hole 342 for facilitating the passing of the angle adjustment bolt 35, a piston rod assembly through hole 343 for facilitating the passing of the push rod 321, an electromagnetic chuck action area 344, and a counterweight installation area 345 are also provided on the counterweight limit plate 34. An electromagnetic chuck 33 is installed above the electromagnetic chuck action area 344, and the counterweight limit plate 34 is adsorbed by the electromagnetic chuck 33 to position the counterweight limit plate 34 at the initial position. During the experiment, the counterweight can also be installed in the counterweight installation area 345 according to the requirements of the test conditions, and the counterweight mass can be adjusted as needed.

[0038] The angle adjustment bolt 35 includes a screw rod portion 351, a fixing ring 352, and a fixing nut 353. When the angle adjustment bolt 35 is installed, one end of the screw rod portion 351 passes through the angle adjustment bolt through hole 342 and is rotatably connected to the top of the test structure body 38 through a universal joint, and the other end passes through the fixing ring 352 on the upper and lower surfaces of the counterweight limiting plate 34 and is fastened to the counterweight limiting plate 34 through the fixing nut 353. In this way, the fixing ring 352 is arranged on both the upper and lower surfaces of the counterweight limiting plate 34 for the angle adjustment bolt 35, which can limit the up and down sliding of the angle adjustment bolt 35 relative to the counterweight limiting plate 34, so that the water entry load of the test system is the test structure body 38, the piston rod assembly 32, the angle adjustment bolt 35, and the counterweight limiting plate 34.

[0039] The screw rod portion 351 has a clearance fit with the angle adjustment bolt through hole 342 and the fixing ring 352 respectively, so that the screw rod portion 351 can move up and down relative to the counterweight limiting plate 34 through the angle adjustment bolt through hole 342. The test structure body 38 is fixedly connected to the counterweight limiting plate 34 through a plurality of angle adjustment bolts 35, and the angle adjustment bolts 35 are evenly distributed around the push rod 321. By adjusting the effective action length of each angle adjustment bolt 35 (i.e., the distance between the corresponding point on the test structure body 38 and the counterweight limiting plate 34), the water entry angle of the test structure body 38 can be changed.

[0040] As Figure 6 shown, for the convenience of installation of each component, the test bench 4 is provided with four layers, which are the phase change module fixing layer 41, the electromagnetic adsorption layer 42, the test buffer braking layer 43, and the base 44 from top to bottom. Each layer is connected into one body through a truss. The base 44 is fixedly arranged at the bottom of the test water tank 6. Four of the guide rails 36 are installed between the phase change module fixing layer 41 and the test buffer braking layer 43. The carbon dioxide phase change acceleration module 1 is installed on the phase change module fixing layer 41. The cylinder 31 is suspended between the phase change module fixing layer 41 and the electromagnetic adsorption layer 42. The electromagnetic chuck 33 is fixedly arranged under the electromagnetic adsorption layer 42. And in the initial state, the counterweight limiting plate 34 is adsorbed to the bottom of the electromagnetic adsorption layer 42 by the electromagnetic force of the electromagnetic chuck 33, and the counterweight limiting plate 34 is slidably installed on the guide rail 36 between the electromagnetic adsorption layer 42 and the test buffer braking layer 43.

[0041] The test method of the high-speed water entry impact test system of the present invention includes the following steps: 1. According to the actual water entry speed requirement of the test structure body 38, calculate the pressure P(t) of the high-pressure carbon dioxide mixed gas in the cylinder 31 after pressure equalization, so as to determine the number of phase change tubes 12 of the carbon dioxide phase change acceleration module 1 and the release time interval of multiple phase change tubes 12 ; 2. Install the test structure body 38 below the counterweight limit plate 34 through the angle adjustment bolt 35 and set the water entry angle; 3. Lift the counterweight limit plate 34 to be attracted to the electromagnetic chuck 33. During the lifting process, the test structure body 38 and the piston rod assembly 32 rise synchronously; 4. Under the suction force of the electromagnetic chuck 33, fix the counterweight limit plate 34, the piston rod assembly 32, and the test structure body 38 at the starting position; 5. The high-speed camera 51, the pressure sensor 53, and the temperature sensor start to collect data; 6. Connect the carbon dioxide phase change acceleration module 1 to an external power supply and release the high-pressure carbon dioxide mixed gas. The high-pressure gas is instantaneously released into the first chamber 311 of the cylinder 31, generating a thrust on the piston rod assembly 32. Under the thrust of the piston rod assembly 32, the counterweight limit plate 34 breaks free from the suction force of the electromagnetic chuck 33, and the counterweight limit plate 34, the piston rod assembly 32, and the test structure body 38 accelerate downward together under the thrust of the piston rod assembly 32; 7. After the test structure body 38 accelerates to the target speed, it enters the water. After entering the water to a certain depth, it stops moving downward after being buffered and decelerated by the spring buffer 37; during the process of the test structure body 38 entering the water, the piston 322 of the piston rod assembly 32 moves to the pressure relief area of the cylinder 31, and the gas pressure in the cylinder is instantaneously released, stopping the accelerated motion; 8. The high-speed camera 51, the pressure sensor 53, and the temperature sensor 54 stop collecting data, and the test ends.

[0042] In the above step 1, the calculation method of the high-pressure carbon dioxide mixed gas pressure P(t) in the cylinder 31 is as follows: Without considering resistance, the relationship between the pressure P(t) in the cylinder 31, the inner diameter dimension D of the cylinder, the effective working stroke L of the cylinder, and the water entry speed of the test structure body is as follows: , , In the formula is the total mass of the piston rod assembly 32, the angle adjustment bolt 35, and the counterweight limit plate 34, with the unit of kg; is the mass of the test structure body 38, with the unit of kg; D is the inner diameter of the cylinder, with the unit of mm; P(t) is the pressure at time t in the cylinder, with the unit of MPa; L is the effective working stroke of the cylinder, with the unit of m; g is the acceleration due to gravity, with the unit of m / s².

[0043] After calculation and analysis, for example: the mass of the test structure body 38 , and the total mass of the piston rod assembly 32, the angle adjustment bolt 35, and the counterweight limit plate 34 , the effective actuation stroke (immersion height) L of the cylinder 31 is 3 m, and the inner diameter dimension D of the cylinder 31 is 500 mm. The technical parameters of the supercritical carbon dioxide phase change-driven high-speed water entry impact test system are determined as shown in the following table:

[0044] Technical Parameters of the Supercritical Carbon Dioxide-Driven High-Speed Water Entry Impact Test System

[0045] Compared with the traditional free-fall water entry impact test method, when the water entry speed of the test structure 38 is required to be 30 m / s, the immersion height needs to reach 45 m. When the present invention is adopted, when the test structure 38 is to reach a water entry speed of 30 m / s, only the effective actuation stroke (immersion height) L = 3 m of the cylinder 31 needs to be provided. It can be seen that the high-speed water entry impact test system of the present invention can achieve high-speed water entry of the structure with short-distance acceleration compared with the traditional water entry impact test method, and the water entry speed can also be adjusted greatly. Moreover, the high-speed water entry impact test system of the present invention is convenient to operate and meets the requirements of economy, processability, practicability and operability.

[0046] In the above method, the number of phase change tubes 12 of the carbon dioxide phase change acceleration module 1 and the release time interval of multiple phase change tubes 12 are determined according to the pressure P(t) of the high-pressure carbon dioxide mixture in the cylinder 31 after pressure equalization The method is:

[0047] It is known that the radius of the cylinder 31 is , the weight of the test body (the test body includes the test structure 38, the piston rod assembly 32, the angle adjustment bolt 35, and the weight limiting plate 34) is , the radius of the pressure acting surface is , the volume of the pressure equalization chamber 11 is , the effective stroke of the test body is , the friction coefficient is , the vertical acceleration angle is and is 90°.

[0048] The sum of the work energy of a single phase change tube 12 and the initial energy of the air in the pressure equalization chamber 11 is equal to the sum of the energy of the liquid carbon dioxide in the phase change tube 12, the kinetic energy of the test body, and the gravitational potential energy of the test structure: (1) In the formula, is the energy of the working medium in the pressure equalization chamber, J; is the moving speed of the test body, m / s; is the gravitational acceleration, m / s²; h is the moving height of the test structure, m; is the initial energy of the air in the pressure equalization chamber, J; is the energy of the gas released from a single phase change tube 12 entering the pressure equalization chamber, J.

[0049] (2) Wherein, is the air mass in the pressure equalizing chamber 11, kg; is the initial enthalpy value of the air in the pressure equalizing chamber 11, is the molar volume of air, equal to 22.414 L / mol, is the molar mass of air, equal to 28.97 g / mol.

[0050] The density of the air in the pressure equalizing chamber at time : (3) Wherein, is the amount of air in the pressure equalizing chamber 11, is the amount of substance entering the pressure equalizing chamber 11 from the phase change tube 12 at time t, is the travel distance of the test body at time t, m.

[0051] The density of the working medium entering the pressure equalizing chamber 11 from the phase change tube 12 at time t : (4) Wherein, is the mass of liquid carbon dioxide entering the pressure equalizing chamber 11 from the phase change tube 12 at time t.

[0052] (5) (6) Wherein, is the mass flow rate of the released working medium, kg / s; is the area of the release port, ; is the pressure in the phase change tube 12, MPa; is the density of liquid carbon dioxide in the phase change tube 12, kg / m 3 ; is the adiabatic coefficient of the working medium. For convenience of calculation, the adiabatic coefficient of CO2, 1.289, is taken.

[0053] If the working medium entering the pressure equalizing chamber 11 from the phase change tube 12 is CO2, then (7) Wherein, is the molar mass of CO2, equal to 44 g / mol.

[0054] Without considering air resistance, the acceleration of the test body movement : (8) In the formula, is the pressure in the pressure equalizing chamber 11 at time t, MPa; is the initial pressure of the air in the equalizing chamber 11, i.e., atmospheric pressure, MPa; is 90°.

[0055] Movement speed of the test subject : (9)

[0056] Test body movement range : (10)

[0057] The air and working gas in the equalizing chamber 11 are at the same temperature and pressure. The density of the air in the equalizing chamber 11 at time t is known. , the density of the working fluid entering the pressure equalizing chamber 11 from the phase change tube 12 at time t , the phase change tube 12 releases the energy entering the pressure equalizing chamber 11 , combined with the test body motion equation, the pressure in the equalizing chamber 11 can be calculated .

[0058] When a single phase change tube 12 does not meet the test body speed requirement, the test body speed can be increased by increasing the number of phase change tubes 12 .

[0059] i phase change tubes 12 release carbon dioxide into the equalizing chamber 11 in sequence at a certain interval. The motion equation of the test body is different from that of a single phase change tube 12 in that the carbon dioxide entering the equalizing chamber 11 from the phase change tube 12 is not completed at one time, but the carbon dioxide energy released by n phase change tubes 12 is accumulated at a certain time interval. The carbon dioxide energy in the equalizing chamber 11 is : (11) In the formula, is the work energy of the first phase change tube 12 entering the pressure equalizing chamber 11 at time t0, is the work energy of the second phase change tube 12 entering the pressure equalizing chamber 11 at time t1, is the work done by the i-th phase change tube 12 entering the pressure equalizing chamber 11 at time ti.

[0060] The carbon dioxide energy released by a single phase change tube 12 can be regarded as a Time series: (12) In the formula, is the time it takes for a single phase change tube 12 to release energy, is the energy released at time t0, is the energy released at time is the time step of the carbon dioxide energy sequence (i.e., the release time interval of the phase change tube), is the energy released at time. Assume there are i phase change tubes 12 releasing working fluid into the pressure equalizing chamber 11 in sequence at the time sequence, and the time series of the total work energy is: (13)

[0061] The mass of carbon dioxide released by a single phase change tube 12 is regarded as a time sequence: (14)

[0062] In the formula, is the mass of carbon dioxide released by a single phase change tube 12, is the time when a single phase change tube 12 releases energy, is the mass of carbon dioxide released at time t0, is the energy released at time is the time step of the carbon dioxide mass sequence (i.e., the release time interval of the phase change tube), is the mass of carbon dioxide released at time. Assume there are i phase change tubes 12 releasing carbon dioxide into the low-pressure chamber in sequence at the time sequence, and the time series of the total carbon dioxide mass is: (15) In the formula, is the mass of carbon dioxide of the phase change tube 12 entering the pressure equalizing chamber 11 at time t0, is the mass of carbon dioxide of the phase change tube 12 entering the pressure equalizing chamber 11 at time t1, is the mass of carbon dioxide of the phase change tube 12 entering the pressure equalizing chamber 11 at time ti.

[0063] Substituting into formulas (3) to (10), the density of the air in the pressure equalizing chamber 11 at time t , and the density of the carbon dioxide entering the pressure equalizing chamber 11 from the phase change tube 12 at time t can be obtained. Combining with the motion equation of the test body, the pressure in the pressure equalizing chamber 11 is then obtained.

[0064] The process of determining the pressure of the pressure equalizing chamber 11 in the single phase change tube 12 test. Calculate the air quantity, mass, and energy in the pressure equalizing chamber 11, then import the output mass and energy of the single phase change tube 12. Combine with the air state in the pressure equalizing chamber 11 to calculate the CO2 density and air density. Substitute them together with the pressure into Refprop_Example_main.VI (the physical property parameters of CO2 and air refer to the Refprop database of the National Institute of Standards and Technology (NIST) in the United States. The Refprop software includes support for dynamic link libraries, allowing other applications to utilize the functions of Refprop). Calculate the energy increments of CO2 and air. Add them to the kinetic energy of the test body and compare with the energy increment output by the phase change tube 12. When the two are equal, the pressure at this time is the pressure in the pressure equalizing chamber 11. Combine with the motion equation of the test body to obtain the motion acceleration, velocity, and displacement of the test body at this time, and update the volume of the pressure equalizing chamber 11. When the travel of the test body is completed, stop the calculation, and finally obtain the pressure curve of the pressure equalizing chamber 11.

[0065] As described above, during the calculation process, continuously assume the number of phase change tubes and the release time interval of the phase change tube 12 for calculation. For example, assume the number is 5, and the time sequence is 0 - 20ms - 40ms - 56ms - 76ms, and the time step is assumed to be 1ms. Through such step-by-step iterative calculation, an expected pressure value, velocity value, and displacement value can be obtained. Then, according to the required high-pressure carbon dioxide mixture pressure P(t) in the cylinder corresponding to the water entry velocity requirement of the test body required by the test, the number of phase change tubes 12 and the release time interval of multiple phase change tubes 12 of the carbon dioxide phase change acceleration module 1 required for the test can be determined. .

[0066] As mentioned above, the above are only specific implementation schemes of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed technical content, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-speed water-entry impact test system, comprising a test bench and a test water tank, wherein the test bench is erected above the test water tank, and a carbon dioxide phase change acceleration module and a test structure assembly are installed on the test bench. It is characterized in that the carbon dioxide phase change acceleration module is used to generate high-pressure carbon dioxide mixed gas through carbon dioxide phase change. The carbon dioxide phase change acceleration module includes at least one phase change tube and a pressure equalizing chamber, and each phase change tube is communicated with the pressure equalizing chamber in chronological order; the test structure assembly includes: a cylinder, inside which a piston rod assembly is installed. The piston rod assembly includes a piston and a push rod. The piston divides the inner cavity of the cylinder along the axial direction of the cylinder into a first chamber and a second chamber. The first chamber is connected to the air outlet of the pressure equalizing chamber of the carbon dioxide phase change acceleration module. The push rod is installed in the second chamber. One end of the push rod is connected to the piston, and the other end extends out of the second chamber and is connected to the test structure; an electromagnetic chuck for fixing the initial position of the test structure; a counterweight limiting plate, which is slidably installed on the push rod, is attracted to the electromagnetic chuck, and a counterweight installation area for installing a counterweight is provided on the counterweight limiting plate; a guide rail installed on the test bench, and the counterweight limiting plate is slidably installed on the guide rail; a pressure sensor for monitoring the change of water pressure in the test water tank and a high-speed camera for monitoring the water-entry speed, water-entry angle, and the change of the surface of the test structure during the underwater movement process are installed near the test structure falling area in the test water tank. A temperature sensor is installed in the carbon dioxide phase change acceleration module for monitoring the temperature of the high-pressure carbon dioxide mixed gas; In the initial state, the electromagnetic chuck fixes the counterweight limiting plate, the piston rod assembly, and the test structure in the initial position; After the test starts and before the test structure enters the water, under the action of the gas output by the carbon dioxide phase change acceleration module, the counterweight limiting plate, the piston rod assembly, and the test structure move downward and accelerate together until the test structure accelerates to the target speed; When the test structure enters the water, the gas in the cylinder is depressurized and the acceleration of the test structure stops. The test structure falls into the water body of the test water tank at the target speed. At the same time, the pressure sensor monitors the water pressure when the test structure enters the water, and the high-speed camera monitors the water-entry speed, water-entry angle, and the change of the surface of the test structure.

2. The high-speed water entry impact test system according to claim 1, wherein The test structure assembly further includes a guide rail installed on the test bench, and the counterweight limiting plate is slidably installed on the guide rail.

3. The high-speed water entry impact test system according to claim 2, characterized in that, A spring buffer is installed at the bottom of the guide rail, and the spring buffer is installed at the end of the stroke of the counterweight limiting plate.

4. The high-speed water-entry impact test system according to claim 1, characterized in that, An angle adjustment unit is installed between the counterweight limiting plate and the test structure. The angle adjustment unit includes a plurality of angle adjustment bolts installed around the push rod. The heads of the angle adjustment bolts are placed on the upper surface of the counterweight limiting plate and fastened with fixing nuts. The screw parts of the angle adjustment bolts pass through the counterweight limiting plate and are rotatably connected to the test structure.

5. The high-speed water-entry impact test system according to claim 1, characterized in that, A pressure relief hole area is provided at the lower end of the second chamber of the cylinder. A plurality of pressure relief holes are distributed in the pressure relief hole area. During the process of the test structure entering the water, the piston of the piston rod assembly moves to the pressure relief hole area.

6. The high-speed water-entry impact test system according to claim 1, wherein, A phase change module fixing layer, an electromagnetic adsorption layer, a test buffer braking layer and a base are sequentially arranged on the test bench from top to bottom. The carbon dioxide phase change acceleration module is installed above the phase change module fixing layer, and the cylinder is installed below it. The electromagnetic chuck is fixedly installed at the bottom of the electromagnetic adsorption layer. The counterweight limit plate is installed between the electromagnetic adsorption layer and the test buffer braking layer. The base is placed in the test water tank.

7. A test method for the high-speed water entry impact test system according to any one of claims 1-6, characterized in that, Including the following steps: 1), Calculate the pressure P(t) of the high-pressure carbon dioxide mixture required in the cylinder according to the actual water entry speed requirement of the test structure, so as to determine the number of phase change tubes of the carbon dioxide phase change acceleration module and the release time interval of multiple phase change tubes , where: The in-cylinder pressure P(t), the cylinder inner diameter D, the effective stroke L of the cylinder, and the water entry velocity of the test structure The relationship among them is as follows: ； ； In the formula is the total mass of the piston rod assembly, angle adjustment bolt, and weight limit plate, with the unit of kg; is the mass of the test structure, with the unit of kg; D is the inner diameter of the cylinder, with the unit of mm; P(t) is the pressure in the cylinder at time t, with the unit of MPa; L is the effective stroke of the cylinder, with the unit of m; g is the acceleration due to gravity, with the unit of m / s²; 2) Install the test structure below the counterweight limit plate and set the water entry angle. 3) Connect the initial position maintaining module of the water entry structure to the counterweight limit plate to fix the counterweight limit plate, the test structure and the piston rod assembly in the initial position. 4) The high-speed camera, the pressure sensor and the temperature sensor start to collect data. 5) Connect the carbon dioxide phase change acceleration module to an external power supply and release high-pressure carbon dioxide mixed gas. The high-pressure carbon dioxide mixed gas is instantaneously released into the cylinder and generates a thrust on the piston rod assembly. Under the thrust of the piston rod assembly, the counterweight limit plate disengages from the initial position maintaining module of the water entry structure, and the counterweight limit plate, the piston rod assembly and the test structure accelerate downward together under the action of the high-pressure carbon dioxide mixed gas. 6) After the test structure accelerates to the target speed, it enters the water. During the process of the test structure entering the water, the cylinder is depressurized, and the test structure stops accelerating. 7) The high-speed camera, the pressure sensor and the temperature sensor stop collecting data, and the test ends.

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