Method and system for lunar soil water-ice drilling process sample temperature rise simulation prediction

Abstract

The application discloses a lunar soil water ice drilling process sample temperature rise simulation prediction method and system, belongs to the moon water ice detection and temperature field simulation technical field, wherein the method comprises the following steps: matching lunar soil characteristic parameters according to the polar lunar soil properties, and establishing a lunar soil water ice particle system according to the lunar soil characteristic parameters; acquiring the inner diameter, the outer diameter and the wall thickness of a drill rod, and the heat output and the heating power input of an instantaneous heat source, and inputting the EDEM simulation software to establish a drill theoretical temperature rise model; performing a single-tooth cutting simulation test based on the water ice particle system and the drill theoretical temperature rise model, and determining a heat source point and a heat generation energy distribution ratio; and integrating the lunar soil water ice particle system, the drill theoretical temperature rise model and the heat generation energy distribution ratio to establish a moon-land interaction discrete element temperature rise model. The method increases the simulation of heat transfer forms such as convection and thermal radiation, the established simulation model is closer to the actual situation, and then the simulation model can predict the temperature rise of the drill and the lunar soil water ice in the drilling process.

Description

Technical Field

[0001] This invention relates to the fields of lunar water ice detection and temperature field simulation technology, and in particular to a method and system for simulating and predicting the temperature rise of samples during lunar soil water ice drilling. Background Technology

[0002] The CE-7 mission plans to obtain in-situ lunar regolith water ice samples through drilling and sampling, and then conduct in-situ analysis of their composition and abundance using scientific instruments such as mass spectrometry. Due to the extremely low temperature environment and the adhesion of water ice, polar lunar regolith exhibits characteristics such as high strength and sensitivity to local temperature rises. Therefore, the drilling load determines the total heat input of the drilling tool, creating a mutually restrictive and contradictory relationship between the properties of polar lunar regolith, the drilling capacity requirements, and sample temperature control. How to rationally control the temperature rise of the lunar regolith and drilling tool under limited load capacity to complete drilling and retrieve high-fidelity lunar regolith water ice is a key problem hindering the project's implementation.

[0003] Currently, ground-based experiments can provide some information about lunar water ice drilling, but they cannot fully reveal the heat generation characteristics and heat conduction patterns of the lunar water ice sampling process. Furthermore, there is no corresponding simulation model for the temperature rise during lunar water ice drilling. Only some researchers have established inter-particle heat conduction models for heat transfer; however, no models have been established for other heat transfer mechanisms during lunar water ice drilling, such as convection (heat transfer occurs during particle flow during drilling) and thermal radiation (the drill bit and surrounding particles radiate electromagnetic waves under vacuum conditions). Simulation models based on existing models and theories will produce biased results and are not suitable for studying the temperature rise during lunar water ice sampling. In addition, current simulation platforms have limitations in simulating heat transfer mechanisms; for example, EDEM software can only simulate heat conduction and cannot simulate heat convection and thermal radiation.

[0004] Therefore, there is an urgent need for a method to solve the above problems and then establish a simulation model of the temperature rise during the drilling process of lunar soil water ice through simulation software and ground tests, so as to achieve the goal of predicting the temperature rise of drilling tools and samples during the drilling process. Summary of the Invention

[0005] This invention provides a method and system for simulating and predicting the temperature rise of samples during lunar soil water ice drilling. While existing ground-based experiments can obtain some information about lunar soil water ice drilling, they cannot fully reveal the heat generation characteristics and heat conduction laws of the lunar soil water ice sampling process. Although EDEM software can simulate heat conduction, it cannot simulate the technical problems of heat convection and heat radiation.

[0006] One embodiment of the present invention provides a method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling, comprising the following steps:

[0007] Step S1: Match lunar soil characteristic parameters according to polar lunar soil properties, and establish a lunar soil water-ice particle system according to the lunar soil characteristic parameters, wherein the lunar soil characteristic parameters include mechanical characteristic parameters and thermal characteristic parameters;

[0008] Step S2: Obtain the drill pipe's inner diameter, outer diameter, wall thickness, and the heat generation and power of the instantaneous heat source, and input them into the EDEM simulation software to establish a theoretical temperature rise model for the drill bit.

[0009] Step S3: Based on the water-ice particle system and the theoretical temperature rise model of the drill bit, a single-tooth cutting simulation test is conducted to determine the heat source point and the distribution ratio of heat generation energy.

[0010] Step S4: Integrate the lunar soil water-ice particle system, the theoretical temperature rise model of the drilling tool, and the heat generation energy distribution ratio to establish a discrete element temperature rise model of the machine-soil interaction.

[0011] Another embodiment of the present invention provides a simulation and prediction system for temperature rise of samples during lunar soil water ice drilling, comprising: constructing a lunar soil water ice particle system module for matching lunar soil characteristic parameters according to polar lunar soil properties, and establishing a lunar soil water ice particle system according to the lunar soil characteristic parameters, wherein the lunar soil characteristic parameters include mechanical characteristic parameters and thermal characteristic parameters;

[0012] A module for constructing a theoretical temperature rise model for drilling tools is used to obtain the inner diameter, outer diameter, wall thickness of the drill pipe, as well as the heat generation and heating power of the instantaneous heat source, and input them into the EDEM simulation software to establish a theoretical temperature rise model for drilling tools.

[0013] The module for determining the heat generation energy distribution ratio is used to conduct single-tooth cutting simulation tests based on the water-ice particle system and the theoretical temperature rise model of the drill bit to determine the heat source point and the heat generation energy distribution ratio.

[0014] An integration module is used to integrate the lunar soil water-ice particle system, the theoretical temperature rise model of the drilling tool, and the heat generation energy distribution ratio to establish a discrete element temperature rise model of the machine-soil interaction.

[0015] Another embodiment of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the simulation prediction method for temperature rise of lunar soil water ice drilling process samples as described in the above embodiment.

[0016] In another aspect, this invention provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the simulation prediction method for temperature rise of lunar soil water ice drilling process samples as described in the above embodiments.

[0017] The technical solution of the present invention achieves at least the following beneficial technical effects:

[0018] The EDEM model was further developed to address the specific characteristics of the target object, incorporating heat transfer calculations for convection, thermal radiation, and geometric structures, resulting in a simulation model that more closely approximates reality. The model's simulation data exhibits high correlation with actual experimental data and high parameter matching accuracy. This simulation model can be used to predict the temperature rise of the drilling tool and lunar regolith water ice during drilling, filling a gap in domestic research on predicting lunar regolith water ice temperature rise during drilling. It provides a basis for further evaluating the impact of drilling on sample quality, designing drilling tool configurations for profile sampling devices, and optimizing procedures, demonstrating significant engineering guidance value.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0021] Figure 1 A flowchart illustrating a method for simulating and predicting temperature rise in lunar soil water ice drilling processes according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram illustrating the establishment of a discrete element temperature rise model of the machine-soil interaction during the drilling process according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the local force chain distribution during a direct shear test according to an embodiment of the present invention;

[0024] Figure 4 The following is a state diagram for measuring thermal parameters using the transient method according to an embodiment of the present invention: (a) before heating, and (b) after heating.

[0025] Figure 5 This is a simplified schematic diagram of a semi-infinite drill pipe according to an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the temperature field calculation process considering the effects of radiative heat transfer according to an embodiment of the present invention.

[0027] Figure 7 This is a schematic diagram of the heat distribution between particles and between blades and particles according to an embodiment of the present invention;

[0028] Figure 8 A schematic diagram of a three-stage magnified variable particle diameter model according to an embodiment of the present invention;

[0029] Figure 9 This is a schematic diagram of a discrete element temperature rise model of the machine-soil interaction according to an embodiment of the present invention;

[0030] Figure 10 The following is a simulation diagram of heat generation and process according to a specific embodiment of the present invention, wherein (a) is a schematic diagram of the application of heat generation energy, and (b) is the drilling process;

[0031] Figure 11 This is a schematic diagram of a simulation prediction system for temperature rise during lunar soil water ice drilling according to an embodiment of the present invention. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0033] The following describes, with reference to the accompanying drawings, a method and system for simulating and predicting the temperature rise of samples during lunar soil water ice drilling according to an embodiment of the present invention. First, the method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0034] Figure 1 This is a flowchart of a method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling, according to an embodiment of the present invention.

[0035] like Figure 1 As shown, based on the EDEM simulation platform, a preliminary simulation analysis of machine-soil heat generation and temperature rise was conducted using a drill bit with a conical matrix and a straight cutting edge configuration for the rotary drilling process. The simulation prediction method for temperature rise of samples during lunar soil water ice drilling includes the following steps:

[0036] In step S1, lunar soil characteristic parameters are matched according to the polar lunar soil properties, and a lunar soil water-ice particle system is established based on the lunar soil characteristic parameters. The lunar soil characteristic parameters include mechanical characteristic parameters and thermal characteristic parameters.

[0037] Furthermore, in one embodiment of the present invention, step S1 specifically includes:

[0038] Step S101: Apply a constant horizontal speed to the lower box of the machine to conduct a direct shear test on a preset soil sample containing water-containing ice-moon soil, and capture the shear strength of the preset soil sample at shear loss.

[0039] Step S102: Determine the cohesion, internal friction angle, elastic modulus, and Poisson's ratio of the pre-set soil sample;

[0040] Step S103: Place the preset soil sample in a preset insulating cylinder and heat it to simulate the temperature field;

[0041] Step S104: After the simulation is completed, the diameter, length and heat source of the preset insulating cylinder are input into the EDEM simulation software for transient processing to obtain the effective thermal conductivity. The preset insulating cylinder is a flat plate and a cylinder containing preset soil, both of which are 0K and insulated. A front heat source with a temperature of 1000K is set at the flat plate.

[0042] Step S105: Determine the thermal conductivity and specific heat capacity of the pre-set soil sample at normal pressure and at low temperature, and at low temperature under vacuum.

[0043] Step S106: Mechanical property parameters are matched using shear strength, cohesion, internal friction angle, elastic modulus and Poisson's ratio; thermal property parameters are matched using effective thermal conductivity, ambient pressure low temperature thermal conductivity and specific heat capacity, vacuum low temperature thermal conductivity and specific heat capacity; and then a lunar soil water ice particle system is established.

[0044] It should be noted that, due to the complexity of coupled simulation of heat generation and heat transfer information, the amount of parameter matching involved is enormous and the cost of related performance testing is high. Therefore, this embodiment of the invention proposes to use a decoupled simulation approach for heat generation and heat transfer, as detailed below:

[0045] like Figure 2 As shown, the drilling target is water-bearing lunar regolith, therefore, it is necessary to first model the lunar regolith according to the properties of polar lunar regolith. The drilling force during drilling determines the total energy input, while the temperature rise of the drill bit and the lunar regolith depends on the heat generation information. Therefore, it is necessary to match mechanical and thermal parameters and verify this through ground tests.

[0046] Matching of mechanical property parameters:

[0047] The application is based on drilling and sampling of water-bearing lunar soil. The primary interaction between the drilling equipment and the lunar soil is shearing; therefore, direct shear test data is selected as the target for mechanical parameter matching. The implementation process is as follows: A constant horizontal velocity is applied to the lower chamber of the drilling equipment. Through simulation post-processing, the change in horizontal shear stress with the displacement of the lower chamber is observed, capturing the peak shear load at which the sample fails. During the shearing process, as the relative shear deformation between the upper and lower chambers develops, the shear stress in the soil sample gradually increases until the shear stress equals the shear strength of the soil, at which point the soil sample fails under shear stress. Figure 3As shown, the direct shear experiment simulation model forms interparticle force chains under the action of gravity and external loads when shear failure occurs. These strong force chains mainly exist on the shear failure surface, indicating that the shear failure surface is the main bearer of the external load in the direct shear experiment. Furthermore, when the shear force on the shear surface exceeds the shear strength of the ice-cement bond between lunar regolith, shear failure occurs. The shear strength can be obtained by processing and analyzing the simulation results, and this is used as the basic parameter for discrete element method (DEM) parameter matching. Other parameters, such as cohesion, internal friction angle, elastic modulus, and Poisson's ratio, are measured using prepared lunar regolith water-ice samples. Finally, the mechanical property parameters are matched using shear strength, cohesion, internal friction angle, elastic modulus, and Poisson's ratio.

[0048] Matching of thermal property parameters:

[0049] It should be noted that the heat conduction between the two particles i and j is calculated according to the following formula:

[0050]

[0051] In the formula, Q ij k is the heat transfer rate from particle j to particle i (unit: W); s F is the thermal conductivity of the particulate material (unit: W / m·K); n E* represents the normal contact force between the particles (unit: N); E* represents the equivalent Young's modulus of the two particles. (Unit: Pa), where E i E j Let ν be the Young's modulus (in Pa) of particles i and j, respectively. i ν j , where are the Poisson's ratios of particles i and j, respectively; r* is the equivalent radius of the two particles. (Unit: m), where r i r j T represents the radii (in meters) of particles i and j, respectively; i T j Particle temperature (unit: °C).

[0052] The above model only considers heat conduction between particles, ignoring convective and radiative heat transfer. Other forms of heat transfer can be equivalent to the effective heat conduction of the particles, simplifying the heat transfer model. It is generally assumed that only air convection exists in a pure particle system, and its impact is minimal. For particles in close contact at relatively low temperatures, the effect of radiative heat transfer between particles is also small, even negligible. However, these effects are gradually amplified as the vacuum level increases.

[0053] Based on the heat transfer relationship between the two particles, if particle i is in contact with n particles, the temperature change of particle i can be calculated using the following formula:

[0054]

[0055] In the formula, t is time (unit: s), n is the number of contacting particles, and ρ i Density of particle i (unit: kg / m³) 3 ), c i V represents the specific heat of particle i (unit: J / kg·℃). i The volume of particle i (unit: m) 3 ).

[0056] The above formula shows that the effective thermal conductivity of a granular system is a macroscopic parameter of the system, which is affected by many parameters. In order to match it, in addition to measuring the effective thermal conductivity of the real simulated lunar soil, it is also necessary to measure the effective thermal conductivity of a granular system in the discrete element method.

[0057] Based on the above analysis, the embodiment of the present invention uses the transient method in EDEM software to calculate the effective thermal conductivity of the particulate system, as detailed below:

[0058] like Figure 4 As shown, to measure the effective thermal conductivity of a particle system, the system is considered as a one-dimensional, semi-infinite object. The particles are placed in an insulated cylinder, where the temperature of the hot plate at the front heat source is 1000K, and the other plate and the cylinder containing the particle system are both 0K and insulated. After a period of heat transfer, the temperature field of the particle system is obtained. Ignoring the change in thermal conductivity with temperature, the temperature field of this one-dimensional, semi-infinite object can be expressed as:

[0059]

[0060]

[0061] In the formula, erf is the error function, which can be obtained by looking up a table, and a is the thermal diffusivity of the semi-infinite object (unit: m). 2 / s), ρ is the density of a semi-infinite object (unit: kg / m³). 3 For a granular system, λ is equivalent to the bulk density, and λ is the thermal conductivity (unit: W / m·K) of a semi-infinite object. For a granular system, λ is equivalent to the effective thermal conductivity.

[0062] After the simulation is completed, the temperature and axial position of all particles in the particle system are exported, and the mass and volume of the particles and the bulk density of the particle system are calculated. The effective thermal conductivity of the particle system can be calculated using the above formula. In addition, other thermal characteristic parameters such as specific heat are directly determined by experiments. Finally, the effective thermal conductivity and specific heat capacity are mainly used to match the thermal characteristic parameters.

[0063] In step S2, the drill pipe's inner diameter, outer diameter, wall thickness, and the heat generation and power of the instantaneous heat source are obtained and input into the EDEM simulation software to establish a theoretical temperature rise model for the drill bit.

[0064] Furthermore, in one embodiment of the present invention, step S2 specifically includes:

[0065] Step S201: Obtain the drill pipe's inner diameter, outer diameter, wall thickness, and the heat generation and power of the instantaneous heat source and input them into the EDEM simulation software. Calculate the temperature field generated by the continuous heat source conduction at the drill pipe's front end based on the temperature at different positions along the axial direction of the drill pipe over a preset time.

[0066] Step S202: Establish an initial theoretical temperature rise model for the drilling tool based on the temperature field;

[0067] Step S203: Consider convection, radiation, drill string configuration, and non-constant heat sources to modify the initial theoretical temperature rise model of the drill string, and obtain the theoretical temperature rise model of the drill string.

[0068] When considering radiation, the temperature field of the drill pipe is regarded as the superposition of heat conduction generated by the heat source at the front end of the drill pipe and the radiation effect of the drill pipe itself. Then, time discretization is used. After discretization, the temperature drop caused by radiative heat dissipation of any infinitesimal element of the drill pipe within one step time is determined. When considering the drill string configuration, the fixed cross-sectional area is replaced with a constant whose cross-sectional area varies with length, and the drill bit and drill pipe threads of the initial theoretical temperature rise model of the drill string are corrected. When considering non-constant heat sources, a function of heat source variation with time is established to correct the initial theoretical temperature rise model of the drill string.

[0069] Understandably, during drilling, heat is generated at the contact surface between the drill string and the lunar regolith; some of the heat enters the drill string, and some enters the lunar regolith. To conduct simulation analysis, a simulation model of the drill string needs to be built in simulation software, as follows:

[0070] First, we will only consider the heat conduction problem of a one-dimensional hollow drill pipe under the influence of a constant heat source. We assume the entire drill string consists of only a hollow drill pipe, neglecting the drill bit and threads, and that the length of the drill pipe is much greater than its diameter. Furthermore, we assume that the temperature is the same at every cross-section of the drill pipe along its semi-infinite axial length. That is, we simplify the heat transfer of the drill string into a one-dimensional, semi-infinite, unsteady-state heat conduction problem with constant physical properties and no internal heat source, such as... Figure 5As shown. In the EDEM, the drill pipe inner diameter r1, outer diameter r2, wall thickness d, and the heat generation Q and heating power q of the instantaneous heat source (x=0) are set. Based on the temperature of the drill pipe at different positions along the axial direction over a certain period of time, the temperature field generated by the continuous heat source at the front end of the drill pipe is calculated. Based on the temperature field, the initial theoretical temperature rise model of the drill tool is established.

[0071] Furthermore, the initial theoretical temperature rise model of the drill string is a simplified simulation model that does not consider the effects of convection, radiation, drill string configuration, and non-constant heat sources. Therefore, it is necessary to revise the initial theoretical temperature rise model of the drill string based on the aforementioned convection, radiation, drill string configuration, and non-constant heat sources, as follows:

[0072] While the EDEM software provides a model for calculating the heat conduction of particles, it does not include calculations for other forms of heat transfer (convection, thermal radiation) or the heat transfer of geometric structures. Therefore, to achieve the desired result, this simulation method is based on EDEM and involves secondary development to create contact models between particles and between particles and the drill bit, which are then imported into EDEM to replace the original contact models.

[0073] like Figure 6 As shown, the calculation process for the effects of convection and radiation on the simplified drill string model is similar, taking radiation under actual working conditions in vacuum as the main method as an example. The effect of radiation on the temperature field is divided into two parts: the first part is the temperature drop caused by heat loss due to radiation, which is called radiative heat dissipation; the second part is the additional heat conduction between points due to the different temperature changes caused by radiative heat dissipation at various points of the drill string, which is called secondary heat conduction. When considering radiation, the temperature field of the drill string can be regarded as the superposition of heat conduction generated by the heat source at the front end of the drill string and the radiation effect of the drill string itself. Radiative heat transfer and heat source heat conduction are coupled, and time discretization is used, that is, temperature is calculated step by step. At the same time, in order to calculate the effect of secondary heat conduction on the temperature field, the drill string is spatially discretized. After discretization, the temperature drop caused by radiative heat dissipation in any infinitesimal element of the drill string within one step time is determined by Stefan Boltzmann's law. The calculation of secondary heat conduction uses Taylor expansion method in traditional numerical heat transfer calculation methods.

[0074] Considering the influence of drill string configuration and non-constant heat sources on the modeling of the drill string temperature field, and correcting the model accordingly, the theoretical temperature rise model of the drill string is obtained as follows:

[0075] The complex configuration of the drill bit has a certain impact on the temperature field. Therefore, it is simplified to assume that heat transfer is only related to the cross-sectional area of ​​the drill bit. The drill bit is divided into l segments according to its complexity. Then, the constant cross-sectional area in step S201 is replaced with a constant whose cross-sectional area varies with length. The same method is used to correct the thread of the drill rod. In addition, the simplified model in step S201 is a constant heat source. Considering the actual situation, the heat source is also discretized, and a function of the heat source changing with time is established and substituted into the simplified model for correction.

[0076] In step S3, a single-tooth cutting simulation test is conducted based on the water-ice particle system and the theoretical temperature rise model of the drill bit to determine the heat source point and the distribution ratio of heat generation energy.

[0077] Furthermore, in one embodiment of the present invention, step S3 specifically includes:

[0078] Step S301: Based on the water-ice particle system and the theoretical temperature rise model of the drill bit, a single-tooth cutting simulation test is carried out. Input the volume scale, cutting depth, cutting edge feed speed, cutting edge radius, cutting edge rake angle, simulated lunar soil physical model, particle radius and periodic boundary to obtain particle-particle and cutting edge-particle heat generation distribution maps.

[0079] Step S302: Based on the distribution of heat sources caused by the interaction between particles, the heat sources are concentrated on the edge surface of the cutting tool near the tip radius and on the contact interface between the cutting edge and the cutting edge to determine the heat source points.

[0080] Step S303: The intensity of the heat source points is accumulated, and the cumulative energy dissipation between particles and between particles and the drill bit is tracked and statistically analyzed using the data superposition method. The two are then compared to obtain the heat generation energy distribution ratio.

[0081] Specifically, steps S1 and S2 established theoretical temperature rise models for the water ice particle system and the drill bit, respectively. Based on these models, the heat source points and heat distribution ratios during the interaction between the drill bit and simulated lunar regolith were studied. During drilling, the total input for heat generation is the drilling rotation load power, and the heat generation pathways include heat generation through soil-machine interaction and soil-soil interaction. The main structure causing lunar regolith water ice fragmentation is the cutting edge; therefore, to simplify the calculations, a single-tooth cutting simulation model was used for the experiment. Input parameters included: volume size, cutting depth, feed rate, tip radius, rake angle, simulated lunar regolith physical model, particle radius, and periodic boundary. The particle material properties were referenced to plagioclase, and the cutting edge parameters were set according to cemented carbide materials. The simulation output showed the particle-particle and cutting tool-particle heat generation distributions as follows: Figure 7As shown, the heat sources generated by the interaction between particles are mainly distributed near the tip radius of the cutting edge; the heat sources on the cutting edge-soil contact interface are concentrated on the tool boundary surface, especially at the tool radius. Based on the simulation results, by accumulating the heat source intensities, the cumulative energy dissipation between particles and between particles and the drill bit is tracked and statistically analyzed using a data superposition method, and the two are compared to obtain the heat generation energy distribution ratio.

[0082] In step S4, a discrete element temperature rise model of the interaction between the machine and the soil is established by integrating the lunar soil water ice particle system, the theoretical temperature rise model of the drilling tool, and the heat generation energy distribution ratio.

[0083] Specifically, based on the aforementioned theoretical temperature rise model and heat generation energy distribution ratio of the lunar soil water-ice particle system drilling tool, an integrated simulation model of overall soil-machine interaction temperature rise is established. Furthermore, a method for modeling the simulated lunar soil with variable particle diameters is proposed to reduce computational load. Specifically, such as... Figure 8 As shown, the simulated lunar regolith is divided into several regions, with flexible boundaries between them, allowing only heat exchange and no particle flow. The first region is the area directly interacting with the drill bit and its vicinity, where the particle diameter is relatively small. Then, the remaining simulated lunar regolith is further divided into two to three regions from the inside out. In these regions, the simulated lunar regolith mainly serves as boundary conditions, experiencing less stress and weaker fluidity. Moreover, since the particle diameter has little effect on the thermal conductivity, the particle diameter is relatively large in these regions.

[0084] Finally, as Figure 9 As shown, by importing the drilling tool from the outside, and adding drilling heat generation and drilling tool heat conduction and heat dissipation modules to the Herts-Mindlin model and Parrallel-Bond model (particle contact model), a discrete element simulation model of drilling simulation of lunar soil is finally obtained, namely the discrete element temperature rise model of machine-soil interaction.

[0085] To more clearly describe the simulation and prediction method for temperature rise during lunar soil water ice drilling in this embodiment of the invention, examples are given below in conjunction with specific application scenarios:

[0086] To explore the actual temperature rise during on-orbit drilling, an established parameter matching method was used to conduct parameter matching work on the thermal parameters of lunar soil water ice under vacuum (1.6 Pa) and low temperature (-180℃). Then, a temperature rise simulation analysis was carried out in the vacuum low temperature environment. The ambient pressure was set to 10-2 Pa, the initial temperatures of the drilling tool were -135℃, -60℃, and -103.15℃, and the lunar soil and ambient temperatures were -240℃ and -183.15℃. Different water contents and different drilling procedures were also set. All other parameters were consistent with the standard test conditions under normal pressure.

[0087] To verify the feasibility of the simulation model, a standard drilling test was conducted at normal pressure and low temperature. For example... Figure 10 As shown, the experimental procedure was input into the simulation model to obtain the simulated temperature rise results of the drill string samples with different water cuts and different procedures. The details of energy supply and drilling process in the temperature rise model are as follows:

[0088] For the aforementioned working conditions with a moisture content of 0–10%, the drill bit temperature rise data curves from the simulation model closely approximate the trends of the actual experimental data curves. The calculated correlation coefficients (r) are all above 0.9, indicating a very high correlation between the two. The relative error of the maximum temperature rise can be controlled within 36%, thus demonstrating the simulation model's reliability.

[0089] For the different operating conditions with a moisture content of 8.5 wt%, the temperature rise data curves of the drill bit in the simulation model are quite close to the trends of the actual experimental data curves. The correlation coefficients (r) obtained from the extraction and calculation are all above 0.5, indicating that there is a correlation between the two. The relative error of the maximum temperature rise can be controlled within 20%, thus the simulation model has a certain degree of reliability.

[0090] The simulation results show the temperature rise of the drill string under vacuum conditions and a comparison with that under ambient temperature conditions:

[0091] 1) The temperature rise of drilling tools when drilling lunar soil with different moisture contents under vacuum conditions, from largest to smallest, is: 10wt% > 5wt% > dry soil. The temperature rise can reach about 86℃ when drilling 10wt% soil, about 68℃ when drilling 5wt% soil, and about 8℃ when drilling dry soil. When drilling 5wt% soil samples, the temperature rise is even lower when using a low-speed drilling tool, about 24℃.

[0092] 2) The temperature change trend of the drilling tool in a vacuum low-temperature environment is generally consistent with that under normal pressure. When the feed rate is fast, the temperature of the drill bit will continue to drop during the drilling process, indicating that the lunar soil has a strong cooling effect on the drill bit when the feed rate is fast. When the feed rate is slow, the temperature of the drill bit will first rise and then fall during the drilling process, indicating that the temperature will first rise due to the heat generated by drilling friction, and then decrease after reaching thermal equilibrium due to the strong cooling effect of the lunar soil.

[0093] 3) The peak drilling temperature of the drill bit under vacuum low temperature environment is strongly correlated with the initial temperature of the drill bit. When the initial temperature is high, the peak temperature of the drill bit is also high, which can reach 15.86℃ in severe cases.

[0094] 4) Under vacuum and low-temperature conditions, the temperature rise is on the same order of magnitude as under normal pressure. Furthermore, the temperature difference between the drill bit and lunar regolith significantly affects the temperature rise. When the temperature difference between the drill bit and lunar regolith is large, the temperature rise amplitude is smaller during certain stages, but due to the already high initial temperature, the maximum and final temperatures are still the highest. Moreover, the temperature drop is more significant in the later stages of drilling, sometimes even lower than the initial temperature.

[0095] 5) For the continuous cutting edge configuration of the conical surface, under the conditions of -60℃ for the drill bit and -240℃ for lunar soil, the temperature rise in vacuum conditions is smaller than that in atmospheric pressure conditions. Specifically, when the water content is 5wt%, the maximum temperature rise in all three vacuum conditions is smaller than that in atmospheric pressure drilling. The pattern is similar when the water content is 0 and 10wt%. The maximum temperature rise in vacuum conditions at -60℃ for the drill bit is smaller than that in atmospheric pressure conditions, but the temperature rise in vacuum conditions at -135℃ for the drill bit is slightly greater than that in atmospheric pressure conditions, and the temperature rise in vacuum conditions at -103.15℃ for the drill bit is greater than that in atmospheric pressure conditions.

[0096] Therefore, it can be seen that ground simulation experiments cannot fully achieve conditions such as vacuum and low temperature. The temperature rise simulation model established using the simulation method of the present invention can provide a prediction of the temperature rise of the drill-soil under vacuum and low temperature environment conditions, which has certain guiding significance for subsequent research.

[0097] In summary, the lunar soil water ice drilling process temperature rise simulation prediction method proposed in this embodiment of the invention employs a direct shear simulation test method to determine the shear strength of the water ice numerical simulation material under specified parameter conditions, and uses this as the basic parameter for discrete element parameter matching; it performs lunar soil water ice thermal parameter matching based on the transient method; it establishes a drill string temperature rise model; it simulates and analyzes the heat generation characteristics of the lunar soil water ice drilling process, and determines the heat source point and heat distribution ratio; and it innovatively uses a variable particle diameter modeling method to integrate and establish a drilling simulation lunar soil water ice temperature rise simulation model, filling a gap in domestic research on drilling processes. This study fills a gap in the prediction of lunar soil water ice temperature rise during drilling. Due to the specific nature of the target object, the EDEM model was further developed, incorporating heat transfer calculations for convection, thermal radiation, and geometric structures. This resulted in a simulation model that more closely approximates reality, with high correlation between the simulation data and actual experimental data, and high parameter matching accuracy. Furthermore, this simulation model can be used to predict the temperature rise of the drilling tool and lunar soil water ice during drilling, providing a basis for further evaluation of the impact of drilling on sample quality, drilling tool configuration design for profile sampling devices, and process optimization. It has significant engineering guiding value.

[0098] Next, referring to the accompanying drawings, a simulation and prediction system for temperature rise of samples during lunar soil water ice drilling according to an embodiment of the present invention is described.

[0099] Figure 11 This is a schematic diagram of the structure of a simulation and prediction system for the temperature rise of samples during lunar soil water ice drilling, according to an embodiment of the present invention.

[0100] like Figure 11 As shown, the system includes: a module 100 for constructing a lunar soil water ice particle system, a module 200 for constructing a theoretical temperature rise model for drilling tools, a module 300 for determining the distribution ratio of heat generation energy, and an integration module 400.

[0101] The system comprises several modules: Module 100, which constructs a lunar soil-water-ice particle system, is used to match lunar soil characteristic parameters based on polar lunar soil properties and to establish the lunar soil-water-ice particle system based on these parameters. The lunar soil characteristic parameters include mechanical and thermal properties. Module 200, which constructs a theoretical temperature rise model for the drill bit, is used to obtain the drill pipe's inner diameter, outer diameter, wall thickness, and the calorific value and power of the instantaneous heat source, inputting these values ​​into the EDEM simulation software to establish a theoretical temperature rise model for the drill bit. Module 300, which determines the heat generation energy distribution ratio, is used to conduct single-tooth cutting simulation tests based on the water-ice particle system and the theoretical temperature rise model for the drill bit to determine the heat source point and the heat generation energy distribution ratio. Module 400, which integrates the lunar soil-water-ice particle system, the theoretical temperature rise model for the drill bit, and the heat generation energy distribution ratio to establish a discrete element temperature rise model of the machine-soil interaction.

[0102] It should be noted that the explanation of the aforementioned embodiment of the simulation prediction method for temperature rise of samples during lunar soil water ice drilling process also applies to the system of this embodiment, and will not be repeated here.

[0103] The lunar soil water ice drilling process temperature rise simulation prediction system proposed in this embodiment of the invention employs a direct shear simulation test method to determine the shear strength of the water ice numerical simulation material under specified parameter conditions, and uses this as the basic parameter for discrete element parameter matching; it performs lunar soil water ice thermal parameter matching based on the transient method; it establishes a drill string temperature rise model; it simulates and analyzes the heat generation characteristics of the lunar soil water ice drilling process, and determines the heat source point and heat distribution ratio; it innovatively uses a variable particle diameter modeling method to integrate and establish a drilling simulation lunar soil water ice temperature rise simulation model, filling a gap in domestic research on drilling processes. This study fills a gap in the prediction of lunar soil water ice temperature rise. Due to the specific nature of the target object, the EDEM model was further developed, incorporating heat transfer calculations for convection, thermal radiation, and geometric structures. This resulted in a simulation model that more closely approximates reality, with high correlation between the simulation data and actual experimental data, and high parameter matching accuracy. Furthermore, this simulation model can be used to predict the temperature rise of the drilling tool and lunar soil water ice during drilling, providing a basis for further evaluation of the impact of drilling on sample quality, drilling tool configuration design for profile sampling devices, and process optimization. It has significant engineering guiding value.

[0104] To implement the above embodiments, the present invention also proposes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the simulation prediction method for temperature rise of lunar soil water ice drilling process samples as described in the foregoing embodiments.

[0105] To implement the above embodiments, the present invention also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the simulation prediction method for temperature rise of lunar soil water ice drilling process samples as described in the foregoing embodiments.

[0106] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0107] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0108] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more N executable instructions for implementing custom logic functions or processes, and the scope of preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of the invention pertain.

[0109] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0110] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0111] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0112] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0113] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling, characterized in that, Includes the following steps: Step S1: Match lunar soil characteristic parameters according to polar lunar soil properties, and establish a lunar soil water-ice particle system according to the lunar soil characteristic parameters, wherein the lunar soil characteristic parameters include mechanical characteristic parameters and thermal characteristic parameters; Step S2: Obtain the drill pipe's inner diameter, outer diameter, wall thickness, and the heat generation and power of the instantaneous heat source, and input them into the EDEM simulation software to establish a theoretical temperature rise model for the drill bit. Step S3: Based on the water-ice particle system and the theoretical temperature rise model of the drill bit, a single-tooth cutting simulation test is conducted to determine the heat source point and the distribution ratio of heat generation energy. Step S4: Integrate the lunar soil water-ice particle system, the theoretical temperature rise model of the drilling tool, and the heat generation energy distribution ratio to establish a discrete element temperature rise model of the machine-soil interaction.

2. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 1, characterized in that, Step S1 specifically includes: Step S101: Apply a constant horizontal speed to the lower box of the machine to conduct a direct shear test on a preset soil sample containing water-containing ice-moon soil, and capture the shear strength of the preset soil sample at shear loss; Step S102: Measure the cohesion, internal friction angle, elastic modulus, and Poisson's ratio of the preset soil sample; Step S103: The preset soil sample is placed in a preset insulating cylinder and heated to simulate the temperature field; Step S104: After the simulation is completed, the diameter, length and heat source of the preset insulating cylinder are input into the EDEM simulation software for transient processing to obtain the effective thermal conductivity. Step S105: Measure the ambient pressure low-temperature thermal conductivity and specific heat capacity, and the vacuum low-temperature thermal conductivity and specific heat capacity of the preset soil sample. Step S106: The mechanical property parameters are matched using the shear strength, cohesion, internal friction angle, elastic modulus and Poisson's ratio; the thermal property parameters are matched using the effective thermal conductivity, ambient pressure low temperature thermal conductivity and specific heat capacity, vacuum low temperature thermal conductivity and specific heat capacity; and the lunar soil water ice particle system is then established.

3. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 2, characterized in that, The preset insulating cylinder consists of a flat plate and a cylinder containing preset soil, both of which are at 0K and insulated. A front-end heat source with a temperature of 1000K is set at the flat plate.

4. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 1, characterized in that, Step S2 specifically includes: Step S201: Obtain the inner diameter, outer diameter, wall thickness, heat generation of the instantaneous heat source, and heat generation power of the drill rod and input them into the EDEM simulation software. Calculate the temperature field generated by the continuous heat source conduction at the front end of the drill rod based on the temperature at different positions along the axial direction of the drill rod over a preset time. Step S202: Establish an initial theoretical temperature rise model for the drilling tool based on the temperature field; Step S203: Consider convection, radiation, drill string configuration, and non-constant heat sources to modify the initial theoretical temperature rise model of the drill string, and obtain the theoretical temperature rise model of the drill string.

5. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 4, characterized in that, When considering radiation, the temperature field of the drill pipe is regarded as the superposition of heat conduction generated by the heat source at the front end of the drill pipe and the radiation effect of the drill pipe itself. Then, time discretization is used. After discretization, the temperature drop caused by radiative heat dissipation in any infinitesimal element of the drill pipe within one step time is determined.

6. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 4, characterized in that, When considering the drill string configuration, the fixed cross-sectional area is replaced with a constant whose cross-sectional area varies with length, and the drill bit and drill pipe threads of the initial theoretical temperature rise model of the drill string are corrected. When considering a non-constant heat source, a function of the heat source changing with time is established to correct the initial theoretical temperature rise model of the drill bit.

7. The method for simulating and predicting the temperature rise of samples during lunar soil water ice drilling as described in claim 1, characterized in that, Step S3 specifically includes: Step S301: Based on the water-ice particle system and the theoretical temperature rise model of the drill bit, a single-tooth cutting simulation test is carried out. Input the volume scale, cutting depth, cutting edge feed speed, cutting edge radius, cutting edge rake angle, simulated lunar soil physical model, particle radius and periodic boundary to obtain particle-particle and cutting edge-particle heat generation distribution maps. Step S302: Based on the distribution of heat sources caused by the interaction between particles, the heat source points are concentrated on the edge surface of the cutting tool near the tip radius and on the contact interface between the cutting edge and the cutting edge to determine the heat source points. Step S303: The intensity of the heat source points is accumulated, and the cumulative energy dissipation between particles and between particles and the drill bit is tracked and statistically analyzed using a data superposition method. The two are then compared to obtain the heat generation energy distribution ratio.

8. A simulation and prediction system for temperature rise of samples during lunar soil water ice drilling process, characterized in that, include: A lunar soil water-ice particle system module is constructed to match lunar soil characteristic parameters according to the properties of polar lunar soil, and to establish a lunar soil water-ice particle system based on the lunar soil characteristic parameters, wherein the lunar soil characteristic parameters include mechanical characteristic parameters and thermal characteristic parameters; A module for constructing a theoretical temperature rise model for drilling tools is used to obtain the inner diameter, outer diameter, wall thickness of the drill pipe, as well as the heat generation and heating power of the instantaneous heat source, and input them into the EDEM simulation software to establish a theoretical temperature rise model for drilling tools. The module for determining the heat generation energy distribution ratio is used to conduct single-tooth cutting simulation tests based on the water-ice particle system and the theoretical temperature rise model of the drill bit to determine the heat source point and the heat generation energy distribution ratio. An integration module is used to integrate the lunar soil water-ice particle system, the theoretical temperature rise model of the drilling tool, and the heat generation energy distribution ratio to establish a discrete element temperature rise model of the machine-soil interaction.

9. A computer device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the simulation and prediction method for temperature rise of lunar soil water ice drilling process samples as described in any one of claims 1-7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the simulation prediction method for temperature rise of lunar soil water ice drilling process samples as described in any one of claims 1-7.

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