Method and device for determining critical crushing speed of partial melting ice crystal impact

Abstract

The invention belongs to the technical field of ice crystal particle impact experiments, and provides a method and a device for determining the critical breaking speed of partial melting ice crystal impact, aiming at the impact problem of partial melting ice crystals, the experimental research of partial melting ice crystals is carried out, and experimental data is combined with an impact kinetic model to determine the critical breaking speed of partial melting ice crystal impact. A dimensionless model of the critical breaking speed of the partially melted ice crystals is obtained; the method has important guiding significance in many fields related to ice crystals; for example, in the aviation field, the method can help to research the safety of parts such as an engine and the like when the aircraft passes through a cloud layer and is impacted by a part of melted ice crystals, and provides key parameters for design and optimization of an anti-icing and deicing system of the aircraft.

Description

Technical Field

[0001] The invention belongs to the technical field of ice crystal particle impact experiments, and in particular relates to a method and a device for determining a critical crushing speed of a partially melted ice crystal impact. Background Art

[0002] After high-altitude ice crystals enter the engine, they will form ice accumulation inside the engine, which may cause engine failure in severe cases. After ice crystals enter the engine, they will form partially melted ice crystals in the engine's thermal environment. The partially melted ice crystals will break, rebound, and adhere to the engine surface when they hit the engine surface. At present, there is no experimental research on the impact behavior of partially melted ice crystals encountered in the flight environment, nor is there a model or correlation for the impact dynamics.

[0003] In order to accurately simulate the breakage of partially melted ice crystals, the present invention carries out experimental research on partially melted ice crystals to address the impact problem of partially melted ice crystals, combines the experimental data with the impact dynamics model, and obtains a dimensionless model of the critical breakage velocity of partially melted ice crystals. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method and device for determining the critical crushing speed of partially melted ice crystals, so as to solve the problems in the prior art. The technical solution adopted by the present invention is: A method for determining the critical crushing speed of partially melted ice crystals, comprising the following steps: Step 1, suspending distilled water droplets above the suspender to form suspended particles, and freezing the suspended particles by low-temperature airflow; Step 2: Real-time measurement of the diameter and melting rate of suspended particles; Step 3: Turn off the low-temperature airflow, and the suspended particles gradually melt; Step 4: When the melting rate of the suspended particles reaches a specified value, the suspended particles are impacted by a high-speed impact rod, and a high-speed camera records the impact process; Step 5, setting different impact speeds of the high-speed impact rod, suspended particle diameters, and suspended particle melting rates and repeating steps 1 to 4 to conduct multiple impact experiments; Step 5: Collect experimental data, including the melting rate of suspended particles, the diameter of suspended particles, the impact speed of the high-speed impact rod, and the fragmentation of suspended particles; Step 6: By integrating the experimental data and the ice crystal breakage model based on impact dynamics and fracture mechanics, the expression of the critical breakage velocity of suspended particles is obtained: ; In the formula, is the critical crushing speed, is the diameter of the suspended particles, kis the critical crushing coefficient; For completely frozen suspended particles, the melting rate is 0. k To determine the constant; For partially melted suspended particles, the melting rate is greater than 0, and the experimental data are fitted to obtain k The value of k The value of is positively correlated with the melting rate of suspended particles.

[0005] Furthermore, in step 2, the diameter of the suspended particles is obtained by a monitoring camera; and the melting rate of the suspended particles is obtained by a heat transfer method.

[0006] Furthermore, in step 6, for completely frozen suspended particles: Logarithmically processing both sides of formula (4), we get: ; Use the hinge loss function as the optimization criterion for fitting the experimental correlation: ; Where i is the serial number and n is the total number of experimental groups; argmin f(x) Represents the objective function f(x) The variable value when it takes the minimum value, f sign is a sign function, e loss,i Represents the loss function of the experimental point with sequence number i, v i represents the impact velocity of the experimental point with serial number i, d ice,i Represents the ice nucleus diameter of the experimental point numbered i.

[0007] Further, in step 6, for the partially melted suspended particles: The diameter of the suspended particles in the mixed phase is , the diameter of the ice core , water film thickness , melting rate ; Defining the relative water film thickness coefficient to measure the effect of water film thickness on the impact and breakage of partially melted ice crystals, where The expression is: ; By exponential fitting, the relative water film thickness coefficient is obtained and critical crushing coefficient k The correlation formula is: .

[0008] A device for determining the critical crushing speed of partially melted ice crystal impact, the device comprising: a nitrogen tank, a nitrogen bath, a cryogenic gas channel, an ultrasonic levitator, a high-speed impact rod, a high-speed camera, a monitoring camera and two thermocouples; The ultrasonic levitator is used to suspend distilled water droplets to form suspended particles; The nitrogen tank is connected to the low-temperature gas channel through a gas pipeline, and a portion of the gas pipeline is immersed in a nitrogen bath; The exhaust end of the low-temperature gas channel faces the suspended particles and is used to eject the low-temperature gas flow to freeze the suspended particles; The high-speed impact rod is located on one side of the suspended particles and is used to impact the suspended particles; The high-speed camera is used to record the impact process; The monitoring camera is used to obtain the diameter of the suspended particles; Two thermocouples are respectively arranged on the front and rear sides of the suspended particles. The two thermocouples are located on the flow path of the low-temperature gas. The temperature of the low-temperature gas before and after passing through the suspended particles is measured by the two thermocouples to obtain the ambient temperature around the suspended particles.

[0009] The present invention has the following beneficial effects: (1) The present invention suspends and freezes distilled water droplets and then controls their melting, which can simulate the actual state of ice crystals in the high-altitude atmosphere entering the warm engine main flow channel and partially melting. The real-time measurement of the diameter and melting rate of the suspended particles provides precise initial conditions and process parameters for subsequent experiments, making the experimental data more accurate and reliable; (2) The experiment was repeated with different high-speed impact rod impact speeds, suspended particle diameters, and melting rates, taking into account the impact of multiple factors on ice crystal fragmentation. This multivariate research method helps to gain a deeper understanding of the relationship between various factors and the critical fragmentation speed, and reveals the inherent laws of impact fragmentation of partially melted ice crystals; (3) The present invention has carried out experimental research and theoretical analysis on the problem of partially melted ice crystal impact, and finally obtained a model and correlation formula for the critical breakage speed of ice crystal impact, which has important guiding significance for many fields involving ice crystals. For example, in the aviation field, it can help study the safety of aircraft engines and other components when they are hit by partially melted ice crystals when passing through clouds, and provide key parameters for the design and optimization of aircraft anti-icing and de-icing systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural diagram of the device of the present invention; Figure 2 It is a schematic diagram of ice crystal melting rate verification; Figure 3 This is the experimental data graph of impact results at 0% melting rate; Figure 4 This is the experimental data graph of the impact result at a 20% melting rate; Figure 5 This is the experimental data graph of the impact result at 40% melting rate; Figure 6 This is the experimental data graph of the impact result at 60% melting rate; Figure 7 This is the experimental data graph of the impact result at 80% melting rate; Figure 8 It is a schematic diagram of the structure of a partially melted ice crystal; Fig. 9 It is the critical fragmentation coefficient fitting schematic diagram; Fig.10 It is an ice crystal breakage model. DETAILED DESCRIPTION

[0011] The following will be combined with the embodiments of the present invention Figure 1-Figure 10 , the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0012] A method for determining the critical crushing speed of partially melted ice crystals, comprising the following steps: Step 1, suspending distilled water droplets above the suspender to form suspended particles, and freezing the suspended particles by low-temperature airflow; Step 2: Real-time measurement of the diameter and melting rate of suspended particles; Step 3: Turn off the low-temperature airflow, and the suspended particles gradually melt; Step 4: When the melting rate of the suspended particles reaches a specified value, the suspended particles are impacted by a high-speed impact rod, and a high-speed camera records the impact process; Step 5, setting different impact speeds of the high-speed impact rod, suspended particle diameters, and suspended particle melting rates and repeating steps 1 to 4 to conduct multiple impact experiments; Step 5: Collect experimental data, including the melting rate of suspended particles, the diameter of suspended particles, the impact speed of the high-speed impact rod, and the fragmentation of suspended particles; Step 6: By integrating the experimental data and the ice crystal breakage model based on impact dynamics and fracture mechanics, the expression of the critical breakage velocity of suspended particles is obtained: ; In the formula, is the critical breaking speed, which is also the normal speed of the high-speed impact rod along the impact plane when the suspended particles are broken; is the diameter of the suspended particles; kis the critical crushing coefficient, which is used to indicate the influence of physical parameters of materials such as yield strength and ice crystal particle density in ice crystal materials; For completely frozen suspended particles, the melting rate is 0. k To determine the constant; For partially melted suspended particles, the melting rate is greater than 0, and the experimental data are fitted to obtain k The value of k The value of is positively correlated with the melting rate of suspended particles.

[0013] The following experimental data can be used as a reference. A total of 308 impact experiments were conducted. The experimental parameters are shown in Table 1. In addition to the dry ice crystal experiment group, 4 different melting rate experiment groups were set up at equal intervals.

[0014] Table 1 Experimental parameters

[0015] In addition, in step six, based on the ice crystal crushing model of impact dynamics and fracture mechanics, consider the process of ice crystal particles with a radius of R0 hitting a dry surface at a relative speed v0. Since the impact surface is made of aluminum alloy, its strength and stiffness are much greater than those of the ice crystal particles, and the impact surface is considered to be a completely rigid plate. The impact process is similar to the impact problem of a long plastic Taylor rod, and the propagation of plastic waves causes the deformation of the rod. The ice crystal particles are regarded as semi-brittle materials. The deformed ice crystal particles during the impact process can be divided into crack zones, plastic deformation zones, and crushing zones, such as Fig.10 shown.

[0016] The distance traveled by the ice crystal along the normal direction of the impact plane is expressed as the dimensionless distance It is expressed as the ratio of the normal motion distance to the radius. When the ice crystal particle is not deformed much, the force on the particle during the collision is approximately equal to the contact area Multiply by the yield strength of the material , we get the equation of motion of the particle in the direction of the impact velocity: ; Where t represents the contact time, V represents the volume of the ice crystal particles, and the maximum indentation radius after the impact is obtained. : ; The indentation radius a and the material properties of the ice crystal particles determine the crack development of the particles. The crack length is estimated using the model of Ghadiri

[29] , and the expression for the critical particle breakage velocity is finally obtained: .

[0017] Furthermore, in step 2, the length corresponding to each pixel of the monitoring camera is calibrated in advance while the camera position and the levitator position are fixed. The diameter of the suspended particles is obtained by inversion of the two-dimensional particle image captured by the monitoring camera; the melting rate of the suspended particles is obtained by heat transfer method.

[0018] Furthermore, in step 6, for completely frozen suspended particles: For the obtained ice crystal breakage data, it can be found that the experimental results of breakage and non-breakage are distributed alternately in a certain range. For most cases, there is no clear dividing line to distinguish between breakage and non-breakage. Figure 3-Figure 7 As shown in the figure, the collision cracking results of particles are divided into broken and unbroken. However, according to the analysis of experimental results, there is no clear dividing line, that is, there is no line that can completely separate them. Artificially dividing this dividing line is very subjective and lacks the rigor of scientific research. In order to find the corresponding k value in the empirical formula, we use this soft margin support vector machine method to determine k. With the experimental results, k is the only one that is determined.

[0019] Therefore, a new method needs to be considered to complete the fitting of the critical breakage velocity: Logarithmically processing both sides of formula (4), we get: ; Since then, the original problem has been transformed into a two-dimensional plane binary classification problem, but considering only the critical fragmentation coefficient k To be determined, critical fragmentation coefficient cannot be obtained using soft margin support vector machine k Therefore, this paper uses the hinge loss function as the optimization criterion for fitting the experimental correlation: ; Where i is the serial number and n is the total number of experimental groups; argmin f(x) Represents the objective function f(x) The variable value when it takes the minimum value, f sign is a sign function, e loss,i Represents the loss function of the experimental point with sequence number i, v i represents the impact velocity of the experimental point with serial number i, d ice,i Represents the ice nucleus diameter of the experimental point numbered i.

[0020] Further, in step 6, for the partially melted suspended particles: In order to explore the effect of melting rate on critical breakage velocity, the impact breakage of partially melted ice crystals at different melting rates was sorted out according to the experimental results. The experimental results can be divided into two cases, namely rebound and breakage. Further, these experimental data were statistically analyzed, and the impact breakage of ice core diameter and impact velocity at different melting rates was shown in Figure 2. Figure 3-Figure 7 As shown, the experimental correlation equation of critical breakage velocity under different melting rates was obtained by fitting method.

[0021] According to the experimental results, it can be preliminarily concluded that as the melting rate increases, the critical crushing speed required for ice nuclei also increases. When the average melting rate is 20%, the critical crushing speed coefficient increases by 114.3%, and when the melting rate is 60%, the critical crushing speed coefficient increases by 173.5%. As the melting rate further increases, the speed required for crushing also increases further.

[0022] In order to further reveal the influence of liquid water on the impact results of partially melted ice crystals and enhance the applicability of the critical breakage velocity correlation of ice crystal impact in the presence of liquid water, the following equation is proposed: Figure 8 Ice crystal impact model under partial melting.

[0023] The model assumes the following: the melting process of ice crystals is simplified to a regular uniform melting process, that is, there is no eccentric melting problem in the melting process, and the ice nucleus is a uniform spherical shape. The diameter of the suspended particles in the mixed phase is , the diameter of the ice core , water film thickness , melting rate ; Considering the melting rate and ice core diameter The change is nonlinear. When the melting rate is high, the ice nucleus diameter will become very small and the water film will be very thick.

[0024] Therefore, the relative water film thickness coefficient is defined as to measure the effect of water film thickness on the impact and breakage of partially melted ice crystals, where The expression is: ; Among them, the melting rate and relative water film thickness coefficient The relationship is nonlinear. When it approaches 100%, will increase dramatically, so consider using the relative water film thickness coefficient to fit and critical fragmentation coefficient k The experimental correlation formula is a more reasonable choice. The critical crushing coefficient obtained from the previous experimental results k Fitting, such as Fig. 9 shown. Fig. 9The red experimental points correspond to the relative water film thickness coefficient and critical crushing coefficient k The relationship between the melting rate and the water film is that the higher the melting rate, the thicker the water film and the smaller the ice nucleus diameter. The corresponding relative water film thickness coefficient is higher and the critical crushing coefficient is larger, resulting in a higher impact speed required for crushing.

[0025] By exponential fitting, the relative water film thickness coefficient is obtained and critical crushing coefficient k The correlation formula is: .

[0026] The present invention conducts experimental research and theoretical analysis on the problem of partially melted ice crystal impact, and finally obtains a model and correlation formula for the critical crushing speed of ice crystal impact.

[0027] The present invention also relates to a device for determining the critical crushing speed of partially melted ice crystal impact, the device comprising: a nitrogen tank, a nitrogen bath, a cryogenic gas channel, an ultrasonic levitator, a high-speed impact rod, a high-speed camera, a monitoring camera and two thermocouples; The ultrasonic levitator is used to suspend distilled water droplets to form suspended particles; The nitrogen tank is connected to the low-temperature gas channel through a gas pipeline, and a portion of the gas pipeline is immersed in a nitrogen bath; The exhaust end of the low-temperature gas channel faces the suspended particles and is used to eject the low-temperature gas flow to freeze the suspended particles; The high-speed impact rod is located on one side of the suspended particles and is used to impact the suspended particles; The high-speed camera is used to record the impact process; The monitoring camera is used to obtain the diameter of the suspended particles; Two thermocouples are respectively arranged on the front and rear sides of the suspended particles. The two thermocouples are located on the flow path of the low-temperature gas. The temperature of the low-temperature gas before and after passing through the suspended particles is measured by the two thermocouples to obtain the ambient temperature around the suspended particles.

[0028] In order to prepare partially melted ice crystals, measure the melting rate and carry out impact experiments, this paper designed and built a partially melted ice crystal high-speed impact test bench. The schematic diagram of the test bench is shown in the figure. Figure 1 The experimental platform mainly includes: ice crystal suspension freezing system, ice crystal melting rate measurement system and high-speed impact system.

[0029] The low-temperature suspension freezing system is mainly composed of a nitrogen bottle, a copper coil heat exchanger, and a flow meter. It is used to provide a low-temperature airflow to freeze the suspended droplets. The speed and temperature of the outlet airflow are controlled by adjusting the pressure reducing valve and the needle valve. The airflow speed can be calculated in real time according to the gas flow meter reading. A T-type thermocouple is set at the outlet of the airflow to measure the outlet airflow temperature. The ultrasonic levitator provides stable suspension conditions for the particles.

[0030] The ice crystal melting rate measurement system mainly includes a monitoring camera, a thermocouple thermometer and several T-type thermocouples. The average temperature around the suspended particles is measured by several T-type thermocouples. The volume of the particles can be further calculated using the image information captured by the monitoring camera. After the low-temperature airflow is turned off, the particles melt in a natural convection environment, and the real-time measurement of the ice crystal melting rate is achieved through heat transfer methods.

[0031] The high-speed impact system includes a self-developed high-speed impact rod, a high-brightness programmed light source, a digital time-delay pulse generator and a high-speed camera. A digital time-delay pulse generator is used as a signal generator to achieve synchronous control of the high-brightness programmed light source, the high-speed camera and the high-speed impact rod. The melting rate of suspended particles is measured in real time using a melting rate measurement method based on heat transfer. When the ice crystals melt to reach the specified melting rate, a signal is sent to synchronously turn on the light source, start the high-speed camera and start the high-speed impact rod. After the solenoid valve of the high-speed impact rod is activated, the impact rod is pushed out by high-pressure gas and hits the suspended ice crystals. The speed of the impact rod can be changed by adjusting the pressure of the high-pressure gas tank. The light source is placed in a backlit position, and a high-speed camera is used to capture the impact process of partially melted ice crystals.

[0032] In addition, in the present invention, a heat transfer method is used to achieve real-time measurement of ice crystal melting rate. Along the direction of the cold air flow, thermocouples are installed at the front and rear sides of the suspended particles, and the air flow temperature is accurately measured at a frequency of 10 Hz using a thermocouple thermometer. The temperature is weighted to obtain the ambient temperature around the suspended particles. .

[0033] After the freezing is stable, the low-temperature airflow is turned off to allow the ice crystals to melt in a natural convection environment. The diameter of the melted ice crystals is obtained through the monitoring camera. , at a known ambient temperature In this case, the heat transfer method can be used to calculate the melting rate of ice crystals. Specifically, the real-time measurement of ice crystal melting rate using heat transfer methods includes the following methods: The phase change process of ice crystal particles can be divided into three stages. (1) Solid state stage: particle temperature Below melting temperature ,Right now The particles are pure solid ice crystals, and the ice crystal particles conduct convection heat exchange with the external environment until the temperature reaches the melting temperature. (2) Melting stage: particle temperature Equal to melting temperature ,Right now , under further heat exchange, the ice crystals begin to melt from the outside, and the temperature remains unchanged. (3) Liquid stage: particle temperature Above melting temperature ,Right now , the ice crystal particles completely melted and became droplets. This study only focused on the solid phase and the melting phase.

[0034] The heat and mass transfer equations in the solid state are as follows: ; In the formula, is the mass of ice crystals, is the specific heat capacity of ice crystals, is the particle diameter, is the Nusselt number, is the thermal conductivity of air, is the air temperature. is the sublimation mass flow rate, and They are latent heat of melting and latent heat of vaporization. is the Sherwood number, is the air density, is the vapor diffusion rate in air. and Represent the mass fraction of vapor on the particle surface and the free surface respectively.

[0035] The heat and mass transfer equations in the melting stage are as follows: ; In the formula, is the evaporation mass flow rate, is the melt mass flow rate. and are the mass and diameter of the ice nucleus during the melting process, respectively.

[0036] The measured data such as temperature, humidity and ambient atmospheric pressure are input into the program, and the heat transfer of ice crystals can be calculated through the heat transfer model, thereby calculating the melting rate of ice crystals in real time.

[0037] Considering that it is a natural convection problem, the empirical correlation formula for natural convection heat transfer of spherical objects is used: ; in Nu is the Nusselt number, Pr is the Prandtl number of air,Gr is the Grashof number.

[0038] In order to verify the accuracy of this measurement method, we used two different ice crystal melting rate measurement methods for cross-validation. These two methods are a direct measurement method based on impacting ice cores and an indirect measurement method based on heat transfer. The melting rate obtained by the direct measurement method based on impacting ice cores is recorded as "melting rate measured by impact method" , the melting rate obtained by the indirect measurement method based on heat transfer is recorded as "melting rate measured by heat transfer method" .

[0039] The principle of the direct measurement method based on impacting ice cores is that ice crystals melt from the outside to the inside under natural convection. They are in a mixed phase state during the melting process. By controlling the impact speed and using an appropriate speed, the impact rod can impact the partially melted ice crystals to separate the unmelted ice cores from the outer water film. The volume of the ice core is calculated. After that, the melting rate of partially melted ice crystals can be further obtained. In the experiments in this study, considering the possible eccentric melting and surface melt water film flow, ice nuclei often present irregular shapes.

[0040] Therefore, for the “impact method to measure melting rate” , the present invention uses a stereological method to calculate the volume of ice nuclei.

[0041] Assume that the diameter of the mixture before impact is , the volume of the ice core is According to the law of conservation of mass, we can get: ; in is the impact method to measure the melting rate, and denote the densities of water and ice respectively, is the equivalent diameter of the ice nucleus, expressed as: ; 54 groups of ice crystal melting rate verification experiments were conducted. and For comparison, Figure 2 As shown. Most of the experimental points fall near the consistency line. In order to obtain the accurate volume of the ice nucleus, a lower impact velocity of 3 m / s to 6 m / s was used to ensure that the ice nucleus inside the partially melted ice crystals would not be broken after being impacted. Affected by the viscosity of the liquid, some liquid water in the form of a water film will adhere to the surface of the ice nucleus after the impact, which amplifies the measurement error of the direct measurement method based on the impact of ice nuclei at low melting rates, resulting in the impact method measuring the melting rate at low melting rates. Deviation from the true melting rate From the linear fitting results and the calibration results at higher melting rates (greater than 40%), it can be seen that and The absolute error is within 17%. In summary, the heat transfer method is used to measure the melting rate. Estimating the true melt rate It is feasible to a certain extent and it is believed that the melting rate measurement method can be used to measure the melting rate of suspended partially melted ice crystals.

[0042] The embodiments described above are only descriptions of the preferred modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, and substitutions made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for determining the critical crushing speed of partially melted ice crystals, characterized in that: The following steps are involved: Step 1, suspending distilled water droplets above the suspender to form suspended particles, and freezing the suspended particles by low-temperature airflow; Step 2: Real-time measurement of the diameter and melting rate of suspended particles; Step 3: Turn off the low-temperature airflow, and the suspended particles gradually melt; Step 4: When the melting rate of the suspended particles reaches a specified value, the suspended particles are impacted by a high-speed impact rod, and a high-speed camera records the impact process; Step 5, setting different impact speeds of the high-speed impact rod, suspended particle diameters, and suspended particle melting rates and repeating steps 1 to 4 to conduct multiple impact experiments; Step 5: Collect experimental data, including the melting rate of suspended particles, the diameter of suspended particles, the impact speed of the high-speed impact rod, and the fragmentation of suspended particles; Step 6: By integrating the experimental data and the ice crystal breakage model based on impact dynamics and fracture mechanics, the expression of the critical breakage velocity of suspended particles is obtained: ； In the formula, is the critical crushing speed, is the diameter of the suspended particles, k is the critical crushing coefficient; For completely frozen suspended particles, the melting rate is 0. k To determine the constant; For partially melted suspended particles, the melting rate is greater than 0, and the experimental data are fitted to obtain k The value of k The value of is positively correlated with the melting rate of suspended particles.

2. A method for determining the critical crushing speed of partially melted ice crystals according to claim 1, characterized in that: In step 2, the diameter of the suspended particles is obtained by a monitoring camera; as for the melting rate of the suspended particles, the melting rate of the suspended particles is obtained by a heat transfer method.

3. A method for determining the critical crushing speed of partially melted ice crystals according to claim 1, characterized in that: In step 6, for completely frozen suspended particles: Logarithmically processing both sides of formula (4), we get: ； Use the hinge loss function as the optimization criterion for fitting the experimental correlation: ； Where i is the serial number and n is the total number of experimental groups; argmin f(x) Represents the objective function f(x) The variable value when it takes the minimum value, f sign is a sign function, e loss,i Represents the loss function of the experimental point numbered i, v i represents the impact velocity of the experimental point with serial number i, d ice,i Represents the ice nucleus diameter of the experimental point numbered i.

4. A method for determining the critical crushing speed of partially melted ice crystals according to claim 1, characterized in that: In step 6, for partially melted suspended particles: The diameter of the suspended particles in the mixed phase is , the diameter of the ice core , water film thickness , melting rate ; Defining the relative water film thickness coefficient to measure the effect of water film thickness on the impact and breakage of partially melted ice crystals, where The expression is: ； By exponential fitting, the relative water film thickness coefficient is obtained and critical crushing coefficient k The correlation formula is: 。 5. A device for determining the critical crushing speed of partially melted ice crystals, using a method for determining the critical crushing speed of partially melted ice crystals according to any one of claims 1 to 4, characterized in that: The apparatus includes: a nitrogen tank, a nitrogen bath, a cryogenic gas channel, an ultrasonic levitator, a high-speed impact rod, a high-speed camera, a monitoring camera, and two thermocouples; The ultrasonic levitator is used to suspend distilled water droplets to form suspended particles; The nitrogen tank is connected to the low-temperature gas channel through a gas pipeline, and a portion of the gas pipeline is immersed in a nitrogen bath; The exhaust end of the low-temperature gas channel faces the suspended particles and is used to eject the low-temperature gas flow to freeze the suspended particles; The high-speed impact rod is located on one side of the suspended particles and is used to impact the suspended particles; The high-speed camera is used to record the impact process; The monitoring camera is used to obtain the diameter of the suspended particles; Two thermocouples are respectively arranged on the front and rear sides of the suspended particles. The two thermocouples are located on the flow path of the low-temperature gas. The temperature of the low-temperature gas before and after passing through the suspended particles is measured by the two thermocouples to obtain the ambient temperature around the suspended particles.

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