Regulation and control method for realizing rapid and uniform temperature change of low-temperature liquid cavitation experiment table

Abstract

The invention discloses a regulation and control method for realizing rapid and uniform temperature change of a low-temperature liquid cavitation experiment table, and belongs to the field of low-temperature liquid cavitation experiments. The implementation method comprises the following steps: constructing the relationship between the ultralow-temperature liquid environment temperature T1 and the saturated vapor pressure pv; when the ultralow-temperature liquid needs to be cooled, a target saturated vapor pressure value ptarget corresponding to the target liquid environment temperature value Ttarget is obtained according to the relation; the environment pressure is adjusted to ptarget, the ultralow-temperature liquid can automatically evaporate and absorb heat, and then the temperature T1 of the ultralow-temperature liquid is reduced to a target value Ttarget; when the ultralow-temperature liquid needs to be heated, according to the relation between the ultralow-temperature liquid environment temperature T1 and the saturated vapor pressure pv, a target saturated vapor pressure value ptarget corresponding to the target liquid environment temperature value Ttarget is obtained, and the environment pressure is stably kept at the target value ptarget; normal-temperature helium is introduced into the bottom of the ultralow-temperature liquid; and rapid temperature rise and temperature regulation and control of the ultralow-temperature liquid are realized by utilizing the principle of convective heat exchange.

Description

Technical Field

[0001] This invention relates to a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation experimental platform, and more particularly to a method for controlling the temperature of cryogenic liquids over a wide range, rapidly, uniformly, and precisely, belonging to the field of cryogenic liquid cavitation experimental technology. Background Technology

[0002] Rapid transport of cryogenic liquids such as liquid hydrogen and liquid oxygen is a core issue in liquid rocket engines and on-orbit refueling. During rapid transport of cryogenic liquids, the sudden pressure drop inevitably leads to cavitation, generating cavitation bubbles. These cavitation bubbles trigger transient impact loads, damaging the surfaces of flow-through components and severely impacting the efficient and safe operation of the system. The generation and evolution of single cavitation bubbles are fundamental building blocks of complex phase change flows, and the high-speed jets and shock waves generated by their collapse are the main forms of load causing damage and instability. Revealing the generation and evolution mechanism of single cavitation bubbles is a fundamental issue for understanding the characteristics of cryogenic cavitation fluids, developing theoretical analysis methods and numerical calculation models, and also a basic scientific problem for improving the safety of liquid rocket engines and on-orbit refueling systems.

[0003] Experimental research has always been the most direct means of studying cavitation evolution. Existing cryogenic liquid cavitation experimental devices primarily use pressurized heating based on heat conduction, which is too inefficient. Furthermore, placing the heating source at the bottom of the experimental device causes the cryogenic liquid to vaporize instantly, leading to a sharp increase in environmental pressure and compromising experimental safety. Simultaneously, the continuous evaporation of the cryogenic liquid during the experiment makes it difficult to maintain a stable pressure above the liquid (air cushion pressure) for extended periods. Moreover, existing cryogenic liquid cavitation experimental devices cannot systematically reveal the evolution process of cavitation bubbles in cryogenic liquids, the heat and mass transfer mechanisms, and the distribution characteristics of impact loads. To address the limitations of existing cryogenic liquid cavitation experimental devices in achieving large-scale, rapid, and uniform temperature changes and measuring transient cavitation collapse loads, it is necessary to invent a control method for achieving rapid and uniform temperature changes in cryogenic liquid cavitation experimental platforms. This is of great significance for revealing the cavitation mechanism and establishing a theoretical framework for cryogenic liquid cavitation. Summary of the Invention

[0004] To address the problems of slow efficiency, low safety, and transient collapse load measurement in existing cryogenic liquid cavitation experimental devices, the present invention aims to provide a control method for rapid and uniform temperature change in a cryogenic liquid cavitation experimental platform. This method integrates a fully enclosed cryogenic liquid experimental platform, an air cushion pressure control system, a large-scale rapid temperature change system, a pulsed laser-based cavitation excitation device, and a synchronous acquisition system for cavitation evolution and transient impact pressure. Utilizing the principles of evaporative heat absorption and convective heat transfer, it achieves rapid and uniform temperature change in the cryogenic liquid and enables transient measurement of cavitation collapse pressure in cryogenic liquids at different temperatures.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention discloses a method for controlling rapid and uniform temperature change in a low-temperature liquid cavitation experimental stage. The method is as follows:

[0007] When cryogenic liquids need to be cooled:

[0008] Cryogenic liquid environment temperature T l With saturated vapor pressure p v The relationship is:

[0009] (1)

[0010] The target liquid ambient temperature T can be obtained according to equation (1). target The corresponding target saturated vapor pressure value p target Adjust the environmental pressure to p target Cryogenic liquids will automatically evaporate and absorb heat, thereby lowering the temperature of the cryogenic liquid T. l Reduce to target value T target ;

[0011] When cryogenic liquids need to be heated:

[0012] The target liquid environment temperature T can be obtained according to equation (1). target The corresponding target saturated vapor pressure value p target And maintain the environmental pressure stably at the target value p target Room temperature helium gas is introduced into the bottom of the cryogenic liquid. Utilizing the principle of convection heat transfer, rapid heating and temperature control of the cryogenic liquid are achieved.

[0013] The amount of helium introduced at room temperature was obtained by the following method:

[0014] Step 1: The temperature of a cryogenic liquid with a volume of V2 is increased from T1 to the target value T. target At that time, the required heat Q1 is:

[0015] (2)

[0016] Where, ρ l C is the density of cryogenic liquids. Pl (T l The isobaric specific heat capacity of a cryogenic liquid as a function of liquid temperature T is... l The changing function is specifically:

[0017] (3)

[0018] Step 2: A volume of room-temperature helium gas, V1, is cooled from temperature T2 to the target value T. targetAt that time, the heat Q2 released is:

[0019] (4)

[0020] Where, ρ l C is the density of cryogenic liquids. Pv (T v The isobaric specific heat capacity of helium varies with gas temperature T. v The changing function is specifically:

[0021] (5)

[0022] Step 3: The heat Q2 released by room-temperature helium is equal to the heat Q1 required for the cryogenic liquid to increase its temperature. Based on the thermal equilibrium relationship, the required volume V1 of room-temperature helium to be introduced is obtained:

[0023] (6)

[0024] Introducing room-temperature helium gas of volume V1 can rapidly raise the temperature of the cryogenic liquid to T. l Increase to target value T target .

[0025] The apparatus for implementing the method mainly includes: a fully enclosed cryogenic liquid experimental platform, an air cushion pressure control system, a wide-range rapid temperature change system, a pulsed laser-based cavitation excitation device, and a synchronous acquisition system for cavitation evolution and transient impact pressure. The fully enclosed cryogenic liquid experimental platform is used to stably place the cryogenic liquid; the air cushion pressure control system is used to adjust and control the pressure above the liquid during the cryogenic liquid cavitation experiment; the wide-range rapid temperature change system is used to adjust the temperature of the cryogenic liquid; the pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform; and the synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of the generated cavitation bubbles and their corresponding impact loads.

[0026] The fully enclosed cryogenic liquid experimental stage mainly consists of a cylindrical vacuum tank and a test tank; a vacuum insulation layer separates the vacuum tank and the test tank; multiple layers of insulation material are used to wrap the test tank to reduce heat leakage; each of the vacuum tank and the test tank has four circular vacuum observation windows and four circular cryogenic observation windows, all of which are coaxial and parallel, used to guide pulsed laser and high-speed camera visualization observation. During the experiment, the vacuum level of the vacuum insulation layer is maintained at 10°C using a first vacuum pump. -5 The pressure is below Pa, which allows the cryogenic liquid to exist stably in the test tank.

[0027] The gas pillow pressure control system specifically includes: a computer control terminal, a first control cabinet, an inlet solenoid valve, an exhaust solenoid valve, a static pressure sensor, a second high-pressure helium cylinder, and a vacuum pump. Connections: The static pressure sensor, inlet solenoid valve, and exhaust solenoid valve are all located at the top of the fully enclosed cryogenic liquid experimental platform; the second high-pressure helium cylinder is connected to the inlet solenoid valve via a pipeline to increase the ambient pressure above the cryogenic liquid in the test tank; the vacuum pump is connected to the exhaust solenoid valve via a pipeline to decrease the ambient pressure above the cryogenic liquid in the test tank; the computer control terminal is connected to the first control cabinet via wiring, and the first control cabinet is connected to the inlet and exhaust solenoid valves via wiring.

[0028] The large-range rapid temperature change system specifically includes: an electromagnetic flowmeter, a second control cabinet, a first high-pressure helium cylinder, and a temperature sensor. Connections: The temperature sensor is located inside the test tank and is used to measure the temperature of the cryogenic liquid. The first high-pressure helium cylinder is connected to the fully enclosed cryogenic liquid experimental platform via a pipeline through the electromagnetic flowmeter. The helium outlet is located at the bottom of the test tank, and the high-purity, room-temperature helium discharged from the outlet serves as a heating source. Utilizing the principle of convection heat transfer, the cryogenic liquid is rapidly heated.

[0029] The pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform. Specifically, it includes a YAG laser, a lens, and a laser pulse signal generator. Connection: The laser pulse signal generator is connected to the YAG laser via wiring to control the laser energy, wavelength, and duration of the YAG laser. The laser light generated by the YAG laser is focused in the cryogenic liquid through the lens to generate cavitation bubbles.

[0030] The synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of cavitation generated by the pulsed laser-based cavitation excitation device in the cryogenic liquid within the fully enclosed cryogenic liquid test rig, and its corresponding impact load. It includes: a rigid wall, a dynamic pressure sensor, fixed steel columns, an IPC signal amplifier, a synchronous acquisition instrument, an LED cold light source, and a high-speed camera. Connections: The rigid wall is located below the cavitation bubble and is fixedly connected to the upper wall of the test tank via four fixed steel columns; the fully enclosed cryogenic liquid test rig is connected to subject the cavitation bubble to Bjerkness force, causing it to impact the rigid wall; the dynamic pressure sensor is located at the center of the rigid wall, with its top end level with the upper surface of the rigid wall, and is used to acquire the impact pressure of the cavitation bubble on the rigid wall; the dynamic pressure sensor is connected to the synchronous acquisition instrument via a circuit through the IPC signal amplifier; the LED cold light source, high-speed camera, vacuum observation window, cryogenic observation window, and cavitation bubble are coaxially parallel and located on both sides of the fully enclosed cryogenic liquid test rig, used to acquire the transient evolution process of the cavitation bubble.

[0031] When the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform needs to be cooled:

[0032] Input the target temperature value T on the computer control terminal. target The first control cabinet opens the exhaust solenoid valve, using a vacuum pump to reduce the environmental pressure inside the test tank to p. target When the temperature of the cryogenic liquid is T l Reduce to target value T target At that time, the first control cabinet closes the exhaust solenoid valve.

[0033] When the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform needs to be heated:

[0034] Input the target temperature value T on the computer control terminal. target The first control cabinet maintains the ambient pressure of the test tank stably at the target value p by controlling the exhaust solenoid valve and the intake solenoid valve. target The second control cabinet opens the electromagnetic flowmeter, allowing room-temperature helium gas to be introduced into the bottom of the test tank through the helium outlet. The specific relationship between the volume of room-temperature helium gas (V1) and the volume of the cryogenic liquid (V2) is obtained according to the formula. When the cryogenic liquid temperature T... l Increase to target value T target At that time, the second control cabinet shuts down the electromagnetic flowmeter.

[0035] When the temperature of the cryogenic liquid in the fully enclosed cryogenic liquid test bench is adjusted to the target value T target Subsequently, the computer control unit sends a step signal to trigger the YAG laser to focus the laser beam through a lens into the cryogenic liquid, generating cavitation bubbles. Simultaneously, a high-speed camera and a dynamic pressure sensor are triggered to collect data on the evolution of the cavitation bubbles and the impact pressure on the rigid wall.

[0036] Beneficial effects:

[0037] 1. The present invention provides a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation test platform, which is based on an automatic control system and can automatically adjust and control the pressure of the air cushion inside the tank during the cryogenic liquid cavitation experiment.

[0038] 2. The present invention provides a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation experimental platform. Based on room temperature helium as a heating source, it utilizes the principles of evaporative heat absorption and convective heat transfer, combined with an automatic control system, to achieve automatic, large-scale, rapid, uniform, and accurate temperature changes of the cryogenic liquid.

[0039] 3. The present invention provides a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation test bench, which can simultaneously collect the transient evolution process of cavitation in cryogenic liquid and its transient impact load distribution characteristics.

[0040] 4. The present invention provides a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation test platform. Within the temperature range of 20~120K, the method utilizes the principles of evaporative heat absorption and convective heat transfer to achieve rapid and uniform temperature change of the cryogenic liquid and to perform transient measurement of the cavitation collapse pressure in cryogenic liquids at different temperatures. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the overall system of a control method for achieving rapid and uniform temperature change on a cryogenic liquid cavitation experimental platform according to the present invention.

[0042] Figure 2 This is an internal structural diagram of the device system for a method of controlling rapid and uniform temperature change in a cryogenic liquid cavitation experimental platform according to the present invention.

[0043] Figure 3 Flowchart of the operation of a large-scale, rapid, and uniform temperature change system;

[0044] Figure 4 This is a flowchart illustrating the operation of a method for controlling rapid and uniform temperature change in a cryogenic liquid cavitation experimental platform according to the present invention.

[0045] Figure 5 The transient evolution and impact load distribution of low-temperature cavitation are shown in the diagram.

[0046] Wherein: 1—First high-pressure helium cylinder, 2—Electromagnetic flowmeter, 3—Second control cabinet, 4—Laser pulse signal generator, 5—First control cabinet, 6—High-speed camera, 7—Synchronous acquisition instrument, 8—Computer control terminal, 9—Vacuum pump, 10—IPC signal amplifier, 11—LED cold light source, 12—Exhaust solenoid valve, 13—Second high-pressure helium cylinder, 14—Inlet solenoid valve, 15—YAG laser, 16—Lens, 17—Static pressure sensor, 18—Temperature sensor, 19—Cavitation, 20—Rigid wall, 21—Dynamic pressure sensor, 22—Helium outlet, 23—Fixed steel column, 24—Vacuum tank, 25—Test tank, 26—Vacuum insulation layer, 27—Insulation material, 28—Vacuum observation window, 29—Low-temperature observation window. Detailed Implementation

[0047] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0048] Example 1:

[0049] As attached Figure 1 , 2As shown in this embodiment, a method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation test platform is disclosed. This method is characterized by utilizing the principles of evaporative heat absorption and convective heat transfer to automatically achieve large-scale, rapid, uniform, and precise control of the temperature of cryogenic liquids such as liquid nitrogen and liquid oxygen within the cryogenic liquid cavitation test system.

[0050] When cryogenic liquids need to be cooled:

[0051] Cryogenic liquid environment temperature T l With saturated vapor pressure p v The relationship is:

[0052] (1)

[0053] The target liquid ambient temperature T can be obtained according to equation (1). target The corresponding target saturated vapor pressure value p target Adjust the environmental pressure to p target Cryogenic liquids will automatically evaporate and absorb heat, thereby lowering the temperature of the cryogenic liquid T. l Reduce to target value T target ;

[0054] When cryogenic liquids need to be heated:

[0055] The target liquid environment temperature T can be obtained according to equation (1). target The corresponding target saturated vapor pressure value p target And maintain the environmental pressure stably at the target value p target Room temperature helium gas is introduced into the bottom of the cryogenic liquid. Utilizing the principle of convection heat transfer, the cryogenic liquid is rapidly heated.

[0056] The amount of helium introduced at room temperature was obtained using the following method.

[0057] Step 1: The temperature of a cryogenic liquid with a volume of V2 is increased from T1 to the target value T. target At that time, the required heat Q1 is:

[0058] (2)

[0059] Where, ρ l C is the density of cryogenic liquids. Pl (T l The isobaric specific heat capacity of a cryogenic liquid as a function of liquid temperature T is... l The changing function is specifically:

[0060] (3)

[0061] Step 2: A volume of room-temperature helium gas, V1, is cooled from temperature T2 to the target value T. target At that time, the heat Q2 released is:

[0062] (4)

[0063] Where, ρ l C is the density of cryogenic liquids. Pv (T v The isobaric specific heat capacity of helium varies with gas temperature T. v The changing function is specifically:

[0064] (5)

[0065] Step 3: The heat Q2 released by room-temperature helium is equal to the heat Q1 required to raise the temperature of the cryogenic liquid. Based on the thermal equilibrium relationship, the required volume V1 of room-temperature helium to be introduced is obtained:

[0066] (6)

[0067] Introducing room-temperature helium gas of volume V1 can rapidly raise the temperature of the cryogenic liquid to T. l Increase to target value T target .

[0068] As attached Figure 1 As shown, the apparatus for implementing the method mainly includes: a fully enclosed cryogenic liquid experimental platform, an air cushion pressure control system, a wide-range rapid temperature change system, a pulsed laser-based cavitation excitation device, and a synchronous acquisition system for cavitation evolution and transient impact pressure. The fully enclosed cryogenic liquid experimental platform is used to stably place the cryogenic liquid; the air cushion pressure control system is used to adjust and control the pressure above the liquid during the cryogenic liquid cavitation experiment; the wide-range rapid temperature change system is used to adjust the temperature of the cryogenic liquid; the pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform; and the synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of the generated cavitation bubbles and their corresponding impact loads.

[0069] The fully enclosed cryogenic liquid experimental stage mainly consists of a cylindrical vacuum tank 24 and a test tank 25; a vacuum insulation layer 26 separates the vacuum tank 24 and the test tank 25; the test tank 25 is wrapped with multi-layer insulation material 27 to reduce heat leakage; the vacuum tank 24 and the test tank 25 each have four circular vacuum observation windows 28 and cryogenic observation windows 29, which are coaxial and parallel to guide the pulsed laser 15 and the high-speed camera 6 for visualization observation. During the experiment, the vacuum level of the vacuum insulation layer 26 is maintained at 100 kJ / L based on the first vacuum pump 9. -5The pressure is below Pa, which allows the cryogenic liquid to exist stably in the test tank 25.

[0070] The air cushion pressure control system specifically includes: a computer control terminal 8, a first control cabinet 5, an inlet solenoid valve 14, an exhaust solenoid valve 12, a static pressure sensor 17, a second high-pressure helium cylinder 13, and a vacuum pump 9. Connections: The static pressure sensor 17, the inlet solenoid valve 14, and the exhaust solenoid valve 15 are all located at the top of the fully enclosed cryogenic liquid experimental platform; the second high-pressure helium cylinder 13 is connected to the inlet solenoid valve 14 via a pipeline to increase the ambient pressure above the cryogenic liquid in the test tank 25; the vacuum pump 9 is connected to the exhaust solenoid valve 12 via a pipeline to decrease the ambient pressure above the cryogenic liquid in the test tank 25; the computer control terminal 8 is connected to the first control cabinet 5 via wiring, and the first control cabinet 5 is connected to the inlet solenoid valve 14 and the exhaust solenoid valve 12 via wiring.

[0071] The large-range rapid temperature change system specifically includes: an electromagnetic flowmeter 2, a second control cabinet 3, a first high-pressure helium cylinder 1, and a temperature sensor 18. Connections: The temperature sensor 18 is located inside the test tank 25 and is used to measure the temperature of the cryogenic liquid. The first high-pressure helium cylinder 1 is connected to the fully enclosed cryogenic liquid experimental platform via a pipeline through the electromagnetic flowmeter 2. The helium outlet 22 is located at the bottom of the test tank 25. The high-purity, room-temperature helium discharged from the helium outlet 22 serves as a heating source, utilizing the principle of convection heat transfer to achieve rapid heating of the cryogenic liquid.

[0072] The pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform. Specifically, it includes: a YAG laser 15, a lens 16, and a laser pulse signal generator 4. Connection: The laser pulse signal generator 4 is connected to the YAG laser 15 via a circuit and is used to control the laser energy, wavelength, and duration of the YAG laser 15. The laser light generated by the YAG laser 15 is focused in the cryogenic liquid through the lens 16 to generate cavitation bubbles 19.

[0073] The synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of cavitation generated by the pulsed laser-based cavitation excitation device in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform, as well as the corresponding impact load. It includes: a rigid wall 20, a dynamic pressure sensor 21, a fixed steel column 23, an IPC signal amplifier 10, a synchronous acquisition instrument 7, an LED cold light source 11, and a high-speed camera 6. Connection relationship: The rigid wall 20 is located below the cavitation bubble 19 and is fixedly connected to the upper wall of the test tank 25 through four fixed steel columns 23; the fully enclosed cryogenic liquid test stage is connected to allow the cavitation bubble 19 to be subjected to Bjerkness force, so that the cavitation bubble 19 impacts the rigid wall 20; the dynamic pressure sensor 21 is located at the center of the rigid wall 20, and the top of the dynamic pressure sensor 21 is kept at the same level as the upper surface of the rigid wall 20, and is used to collect the impact pressure of the cavitation bubble 19 on the rigid wall 20; the dynamic pressure sensor 21 is connected to the synchronous acquisition instrument 7 through the IPC signal amplifier 10 via a line; the LED cold light source 11, the high-speed camera 6, the vacuum observation window 28, the low temperature observation window 29, and the cavitation bubble 19 are coaxial and parallel, respectively located on both sides of the fully enclosed cryogenic liquid test stage, and are used to collect the transient evolution process of the cavitation bubble 19.

[0074] As per the instruction manual Figure 3 As shown, when the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform needs to be cooled:

[0075] Input the target temperature value T at the computer control terminal 8 target The first control cabinet 5 opens the exhaust solenoid valve 12, and uses the vacuum pump 9 to reduce the environmental pressure inside the test tank 25 to p. target When the temperature of the cryogenic liquid is T l Reduce to target value T target At that time, the first control cabinet 5 closes the exhaust solenoid valve 15.

[0076] When the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform needs to be heated:

[0077] Input the target temperature value T at the computer control terminal 8 target The first control cabinet 5 controls the exhaust solenoid valve 12 and the intake solenoid valve 14 to stably maintain the ambient pressure of the test tank 25 at the target value p. target The second control cabinet 3 opens the electromagnetic flowmeter 2, allowing room-temperature helium gas to be introduced into the bottom of the test tank 25 through the helium outlet 22. The specific relationship between the volume V1 of the introduced room-temperature helium gas and the volume V2 of the cryogenic liquid is obtained according to equation 6. When the cryogenic liquid temperature T... l Increase to target value T target At that time, the second control cabinet 3 shuts down the electromagnetic flowmeter 2.

[0078] As per the instruction manual Figure 4As shown, when the temperature of the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform is adjusted to the target value T... target Subsequently, the computer control terminal 8 controls the synchronous acquisition instrument 7 to send a step signal, triggering the laser generated by the YAG laser 15 to be focused by the lens 16 in the cryogenic liquid to generate a cavitation bubble 19. Simultaneously, the high-speed camera 6 and the dynamic pressure sensor 21 are triggered to acquire the evolution process of the cavitation bubble 19 and the impact pressure on the rigid wall 20, respectively. The acquisition results are shown in the attached figure. Figure 5 As shown.

[0079] To address the problems of slow efficiency, low safety, and inability to measure transient collapse loads in existing cryogenic liquid cavitation experimental devices, a method for controlling rapid and uniform temperature changes in a cryogenic liquid cavitation experimental platform is proposed. This invention utilizes the principles of evaporative heat absorption and convective heat transfer to achieve automatic, rapid, and uniform temperature changes of any cryogenic liquid over a wide range. The main apparatus of this invention includes: a fully enclosed cryogenic liquid experimental platform, an air cushion pressure control system, a large-range rapid temperature change system, a pulsed laser-based cavitation excitation device, and a synchronous acquisition system for cavitation evolution and transient impact pressure. Specifically, the fully enclosed cryogenic liquid experimental platform is used to stably hold the cryogenic liquid; the air cushion pressure control system is used to adjust and control the pressure above the liquid during the cryogenic liquid cavitation experiment; the large-range rapid temperature change system is used to adjust the temperature of the cryogenic liquid; the pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform; and the synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of the generated cavitation bubbles and their corresponding impact loads. This invention is versatile, safe and reliable, and can be used for any cryogenic liquid within a temperature range of 20~120K.

[0080] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the rapid and uniform temperature change of a cryogenic liquid cavitation experimental stage, characterized in that: When cryogenic liquids need to be cooled: Cryogenic liquid environment temperature T l With saturated vapor pressure p v The relationship is: (1) The target liquid ambient temperature T is obtained according to equation (1). target The corresponding target saturated vapor pressure value p target Adjust the environmental pressure to p target Cryogenic liquids will automatically evaporate and absorb heat, thereby lowering the temperature of the cryogenic liquid T. l Reduce to target value T target ; When cryogenic liquids need to be heated: The target liquid environment temperature T is obtained according to equation (1). target The corresponding target saturated vapor pressure value p target And maintain the environmental pressure stably at the target value p target Room temperature helium gas is introduced into the bottom of the cryogenic liquid; the principle of convection heat transfer is used to achieve rapid heating and temperature control of the cryogenic liquid.

2. The method as described in claim 1, characterized in that: The amount of helium introduced at room temperature was obtained using the following method. Step 1: The temperature of a cryogenic liquid with a volume of V2 is increased from T1 to the target value T. target At that time, the required heat Q1 is: (2) Where, ρ l C is the density of cryogenic liquids. Pl (T l The isobaric specific heat capacity of a cryogenic liquid as a function of liquid temperature T is... l The changing function is specifically: (3) Step 2: A volume of room-temperature helium gas, V1, is cooled from temperature T2 to the target value T. target At that time, the heat Q2 released is: (4) Where, ρ l C is the density of cryogenic liquids. Pv (T v The isobaric specific heat capacity of helium as a function of gas temperature T is... v The changing function is specifically: (5) Step 3: The heat Q2 released by room-temperature helium is equal to the heat Q1 required for the cryogenic liquid to increase its temperature. Based on the thermal equilibrium relationship, the required volume V1 of room-temperature helium to be introduced is obtained: (6) Introducing room-temperature helium gas of volume V1 can rapidly raise the temperature of the cryogenic liquid to T. l Increase to target value T target .

3. An apparatus for implementing the method as described in claim 1 or 2, characterized in that: The system includes a fully enclosed cryogenic liquid experimental platform, an air cushion pressure control system, a wide-range rapid temperature control system, a pulsed laser-based cavitation excitation device, and a synchronous acquisition system for cavitation evolution and transient impact pressure. The fully enclosed cryogenic liquid experimental platform is used to stably place the cryogenic liquid. The air cushion pressure control system is used to adjust and control the pressure above the liquid during the cryogenic liquid cavitation experiment. The wide-range rapid temperature control system is used to adjust the temperature of the cryogenic liquid. The pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform. The synchronous acquisition system for cavitation evolution and transient impact pressure is used to synchronously acquire the transient evolution process of the generated cavitation bubbles and their corresponding impact loads.

4. The apparatus as described in claim 3, characterized in that: The fully enclosed cryogenic liquid experimental platform mainly consists of a cylindrical vacuum tank (24) and a test tank (25); a vacuum insulation layer (26) is placed between the vacuum tank (24) and the test tank (25); the test tank (25) is wrapped with multi-layer insulation material (27) to reduce heat leakage; the vacuum tank (24) and the test tank (25) each have four circular vacuum observation windows (28) and low temperature observation windows (29), and each vacuum observation window (28) and low temperature observation window (29) are kept coaxial and parallel to guide the pulsed laser (15) and the high-speed camera (6) for visualization observation; during the experiment, the vacuum degree of the vacuum insulation layer (26) is maintained at 10 based on the first vacuum pump (9). -5 The pressure is below Pa, which allows the cryogenic liquid to exist stably in the test tank (25).

5. The apparatus as described in claim 3, characterized in that: The air cushion pressure control system includes a computer control terminal (8), a first control cabinet (5), an inlet solenoid valve (14), an exhaust solenoid valve (12), a static pressure sensor (17), a second high-pressure helium cylinder (13), and a first vacuum pump (9). The static pressure sensor (17), the inlet solenoid valve (14), and the exhaust solenoid valve (15) are all located on the top of the fully enclosed cryogenic liquid test bench. The second high-pressure helium cylinder (13) is connected to the inlet solenoid valve (14) through a pipeline to increase the ambient pressure above the cryogenic liquid in the test tank (25). The first vacuum pump (9) is connected to the exhaust solenoid valve (12) through a pipeline to reduce the ambient pressure above the cryogenic liquid in the test tank (25). The computer control terminal (8) is connected to the first control cabinet (5) through a line, and the first control cabinet (5) is connected to the inlet solenoid valve (14) and the exhaust solenoid valve (12) through lines respectively.

6. The apparatus as described in claim 3, characterized in that: The wide-range rapid temperature change system includes an electromagnetic flowmeter (2), a second control cabinet (3), a first high-pressure helium cylinder (1), and a temperature sensor (18). The temperature sensor (18) is located inside the test tank (25) and is used to measure the temperature of the cryogenic liquid. The first high-pressure helium cylinder (1) is connected to the fully enclosed cryogenic liquid test bench through a pipeline via the electromagnetic flowmeter (2). The helium outlet (22) is located at the bottom of the test tank (25). The high-purity room-temperature helium discharged from the helium outlet (22) serves as a heating source. By utilizing the principle of convection heat transfer, the cryogenic liquid is rapidly heated.

7. The apparatus as described in claim 3, characterized in that: The pulsed laser-based cavitation excitation device is used to generate cavitation bubbles in the cryogenic liquid within the fully enclosed cryogenic liquid experimental platform. The pulsed laser-based cavitation excitation device includes a YAG laser (15), a lens (16), and a laser pulse signal generator (4). The laser pulse signal generator (4) is connected to the YAG laser (15) via a circuit and is used to control the laser energy, wavelength, and action time of the YAG laser (15). The laser generated by the YAG laser (15) is focused in the cryogenic liquid through the lens (16) to generate cavitation bubbles (19).

8. The apparatus as described in claim 3, characterized in that: The synchronous acquisition system for cavitation evolution and transient impact pressure includes a rigid wall (20), a dynamic pressure sensor (21), fixed steel columns (23), an IPC signal amplifier (10), a synchronous acquisition instrument (7), an LED cold light source (11), and a high-speed camera (6); the rigid wall (20) is located below the cavitation bubble (19) and is fixedly connected to the upper wall of the test tank (25) through four fixed steel columns (23); the fully enclosed cryogenic liquid test bench is connected to allow the cavitation bubble (19) to be subjected to Bjerkness force, so that the cavitation bubble (19) impacts the rigid wall (20); the dynamic pressure sensor ( 21) The top of the dynamic pressure sensor (21) located at the center of the rigid wall (20) is at the same level as the upper surface of the rigid wall (20) to collect the impact pressure of the cavitation bubble (19) on the rigid wall (20); the dynamic pressure sensor (21) is connected to the synchronous acquisition instrument (7) through the line via the IPC signal amplifier (10); the LED cold light source (11), the high-speed camera (6), the vacuum observation window (28), the low temperature observation window (29), and the cavitation bubble (19) are coaxial and parallel, respectively located on both sides of the fully enclosed ultra-low temperature liquid experimental platform, to collect the transient evolution process of the cavitation bubble (19).

9. A method for rapid and uniform temperature change using the apparatus described in claim 3, 4, 5, 6, 7, or 8, characterized in that: When the cryogenic liquid in the fully enclosed cryogenic liquid experimental platform needs to be cooled: Input the target temperature value T at the computer control terminal (8). target The first control cabinet (5) opens the exhaust solenoid valve (12) and uses the first vacuum pump (9) to reduce the environmental pressure inside the test tank (25) to p. target ; When the temperature of the low-temperature liquid is T l Reduce to target value T target At that time, the first control cabinet (5) closes the exhaust solenoid valve (15); When the cryogenic liquid inside the fully enclosed cryogenic liquid experimental platform needs to be heated: Input the target temperature value T at the computer control terminal (8). target The first control cabinet (5) controls the exhaust solenoid valve (12) and the intake solenoid valve (14) to stably maintain the ambient pressure of the test tank (25) at the target value p. target The second control cabinet (3) opens the electromagnetic flowmeter (2) and introduces room temperature helium gas into the bottom of the test tank (25) through the helium gas outlet (22); the specific relationship between the volume V1 of room temperature helium gas and the volume V2 of the cryogenic liquid is obtained according to formula (6); when the temperature T of the cryogenic liquid is... l Increase to target value T target At that time, the second control cabinet (3) shuts down the electromagnetic flowmeter (2); When the temperature of the cryogenic liquid in the fully enclosed cryogenic liquid test bench is adjusted to the target value T target Then, the computer control terminal (8) controls the synchronous acquisition instrument (7) to send a step signal, triggering the laser generated by the YAG laser (15) to be focused in the cryogenic liquid through the lens (17) to generate a cavitation bubble (19); at the same time, the high-speed camera (6) and the dynamic pressure sensor (21) are triggered to collect the evolution process of the cavitation bubble (19) and the impact pressure on the rigid wall (20) respectively.

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