Changes In Temperature Field Research Articles

Temperature field analysis and equal-amplitude temperature rise constraint current control method under open-circuit fault-tolerant operation for five-phase permanent magnet motor

The phase redundancy and freedom of the five-phase permanent magnet motor (FPPMM) enhance the reliability of the motor system. However, the temperature rise and torque reduction issues of the motor during open-circuit fault operation need to be further studied. In order to study the temperature distribution characteristics and the output capability of the motor under fault operation subject to temperature rise constraints, a 3-D global temperature field model containing a complex heat dissipation structure has been established. And the equal-amplitude temperature rise constraint current control method is proposed under open-circuit fault-tolerant operation to improve its output capability. The temperature distribution of the motor during steady state operation under rated operating conditions is analyzed with emphasis. Based on this, the temperature field changes of the motor during single-phase and two-phase open-circuit fault-tolerant operation are investigated. Then, the proposed equal-amplitude temperature rise constrained current method is introduced in detail to ensure the safe operation of the motor. An experimental platform is built, which verifies the accuracy of the temperature field calculation, as well as the correctness of equal-amplitude temperature rise constrained current method.

Influence of Monolith Length on Temperature Field of Concrete Gravity Dams

This paper examines the influence of monolith length on the temperature field of concrete gravity dams built using the block method. The developed 3D model is capable of conducting a thermal analysis of a 95.0 m high concrete gravity dam built using the block method, where each newly cast block represents a new analysis phase. The calculation accounts for the period of construction, the filling of the reservoir, and the service for a total duration of about 5 years. The thermal properties of the material, the influence of cement hydration heat, the temperature of the surrounding rock mass, the temperature of the fresh concrete mixture, and the corresponding boundary conditions defining a heat transfer were taken into account. The height and width of the blocks, as well as the sequence of concreting, were considered invariable, while the length of the blocks (dimension in the direction of the dam’s axis equal to the monolith length) varied, with values of 10.0, 12.5, 15.0, and 20.0 m. The obtained calculation results for the control nodes showed that the maximum reduction in the monolith length (from 20.0 m to 10.0 m) caused a decrease in the maximum temperature values of the concrete (from 1.6 to 3.4 °C, depending on the control node). Also, the results showed that, by reducing the length of the monolith, there was a delay in the moment at which the maximum temperature values of the concrete appeared in the selected control node. The delay in reaching the maximum, in relation to the 10.0 m long monolith, was from 7 days (for points on the crest dam) to 49 days (for points in the central zone of the monolith) for the other considered monolith lengths. The above indicates the importance of concrete temperature control for longer monoliths, especially during construction in extreme air temperatures. The main contribution of the conducted analysis is the development of insight into temperature field changes depending on monolith length, which can help engineers during the design and construction of new, as well as the maintenance of existing, dams.

Phase field simulations on the rate‐ and grain‐size‐dependent crack propagation of polycrystalline NiTi shape memory alloy

AbstractA three‐dimensional non‐isothermal phase field model of polycrystalline NiTi shape memory alloy (SMA) was established based on the Ginzburg–Landau's theory, which considered the interaction between crack growth and martensite transformation (MT). Then, the crack propagation of polycrystalline NiTi SMA and its dependence on the system's grain size and loading rate were studied by the phase field simulations. The results show that the proposed phase field model can characterize the MT behavior, temperature field changes, and stress‐displacement response of NiTi SMA during the crack growth with different grain sizes and loading rates. That is the higher the loading rate, the higher the fracture toughness is; the larger the grain size, the higher the fracture toughness is and the more significant the influence of grain boundary on the crack growth path becomes. Meanwhile, as the grain size increases, the fracture mode gradually changes from the transgranular fracture (for the fine‐grained alloy with a grain size ≈ 15 nm) to the intergranular one (for the coarse‐grained alloy with a grain size ≈ 100 nm).

Unconventional magnetotransport properties of two-dimensional ferromagnet Fe5GeTe2

Two-dimensional (2D) van der Waals FexGeTe2 metallic ferromagnets have Curie temperature near or even higher than room temperature, showing great prospects in the field of spintronics. Here, we study the magnetotransport properties of Fe5GeTe2 nanoflakes. Multiple sign changes of angle-dependent magnetoresistance (ADMR) are observed with changing temperature or magnetic field. The high field-induced negative to positive MR transition in low temperatures (T < 50 K) and the temperature-induced sign reversal of anisotropic MR at T = 130 K are responsible for these exotic and complex characteristics of ADMR. In addition, the electron–magnon scattering induced negative MR exhibits abnormal nonmonotonic temperature dependence, which is related to the nonmonotonic variation of anomalous Hall resistance and the transition of the carrier types at T = 150 K. The exotic magnetotransport properties of Fe5GeTe2 revealed in this work may help pave the way for the practical application of this 2D magnetic material.

Simulation study on effect of flame cutting speed on temperature field and residual stress distribution

Due to the advantages of flame cutting in thick plate cutting and cutting cost, it is widely used in the metal cutting process of shipbuilding and machinery manufacturing. But at the same time, the local heating of flame cutting will cause residual stress inside the steel plate. Residual stress is an important reason for deformation and cracking of components. The change of temperature field is the premise of affecting the distribution of residual stress. Cutting speed has an important effect on the distribution of temperature field and residual stress field. In this paper, ABAQUS is used to create a finite element model for flat flame cutting of Q345D low-alloy steel. Based on the working principle of flame cutting, the model of flame cutting composite heat source is established and the subprogram of composite heat source is written. The thermal-mechanical direct coupling method is used to simulate and analyze the effect of different cutting speeds on the temperature and residual stress field distribution of the flat flame cutting process, to provide a reference for the subsequent processing.

Microstructure and mechanical properties of Cu-Cr-Zr alloy prepared by electron beam additive manufacturing and laser-MIG hybrid welding

Cu-Cr-Zr alloys are widely used as medium-strength and high-conductivity copper alloys in aerospace, transportation and electronic information fields. The application of additive manufacturing technology is expected to realize the preparation of Cu-Cr-Zr alloy parts with complex structure and superior property. However, the commonly used laser additive manufacturing technology is not applicable to the preparation of copper alloys due to its intrinsic high reflection to laser. In this study, we adopted two technologies, i.e., electron beam additive manufacturing (EBAM) and laser-metal inert gas hybrid welding (laser-MIG), for the preparation of Cu-Cr-Zr alloys. Finite element simulation was employed to simulate the temperature field and residual stress field of the material during solidification. The microstructure, relative density, microhardness, tensile properties and electrical conductivity of the as-fabricated samples were characterized. The results showed that samples with better moldability were obtained by both methods at a line energy density of 600 J/mm. In the top area, both methods exhibit medium-sized equiaxed grains with more precipitated phases, showing the best comprehensive properties. The EBAM method demonstrates superior formability, better relative density and electrical conductivity due to more stable temperature field changes. On the other hand, the laser-MIG method obtains finer grains and higher mechanical properties because of a faster cooling rate, but leads to a decrease in relative density and electrical conductivity. This study presents new experimental data for Cu-Cr-Zr alloys prepared by EBAM and laser-MIG methods, contributing to extend the application of additive manufacturing in the preparation of Cu alloys.

Research on the multi-parameter-based detection scheme for current transformers

Oil-immersed current transformers are commonly used as a type of electrical equipment, but they may experience some faults and defects during actual operation. When detecting these faults and defects, the usual detection object is temperature, which is a single detection quantity and easily leads to misjudgment. This article introduces typical defects in oi-limmersed current transformers, conducts simulation analysis, studies the temperature field changes of current transformers when three typical defects occur, and studies the relationship between temperature and pressure to determine the feasibility of using temperature and pressure as the detection object, to improve the accuracy of detection. The results show that by using temperature and pressure as measurement values of a new detection method, the problem of single measurement parameters that cannot determine the internal condition of the equipment can be solved. By monitoring changes in temperature and pressure in real-time, misjudgment due to external factors can be avoided based on the relationship between temperature and pressure.

Multi-objective optimization of heat charging performance of phase change materials in tree-shaped perforated fin heat exchangers

To enhance the convective heat transfer and overall thermal performance of horizontal latent heat storage (LHS) units, an innovative tree-shaped fin structure with perforations was introduced. A numerical simulation study examined the impact of perforation layers on the unit's overall performance. For a comprehensive analysis of the perforations' cumulative effect on the LHS unit, the Response Surface Methodology (RSM) was utilized to assess the influence of variations in perforation diameter and number on material consumption and heat exchange targets, deriving predictive correlations. The results indicated that compared to a non-perforated structure, the maximum improvement was observed with three layers of perforations, reducing material usage by 0.93%, while increasing the Nusselt number (Nu) and heat exchange by 10.19% and 36.51%, respectively. Moreover, the average temperature of the phase change material (PCM) in one and three perforated layers was higher than in the non-perforated tree-shaped fins, with complete melting times reduced by 5.37% and 2.51%, respectively. RSM results showed a negative linear correlation between increased perforation diameter and number with reduced material consumption, with the number of perforations having a more significant impact on heat exchange than their diameter. The Pareto optimal points obtained using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) demonstrated lower material usage and higher heat exchange. Compared to the non-perforated tree-shaped fins, the Pareto-optimized solutions reduced material consumption by 2%–2.68% and increased heat exchange by 79.42%–94.45%. Analysis of the flow field, temperature field, and phase change process revealed that perforations significantly enhanced the mixing of PCM in different areas of the tree-like fins and secondary flow, with temperatures near the perforations increasing by 5–7K and flow velocity by 3–4 times, significantly promoting convective heat transfer.

Simulation of Temperature Field in Railway Embankment Filling in Seasonal Frozen Areas

In order to examine the temperature field changes of railway roadbed in seasonal frozen areas under different filling heights, a typical cross-sectional model of Chagan Lake Station railway was established using the finite element numerical simulation software ANSYS. The temperature parameters of the roadbed were calculated based on the atmospheric temperature of local meteorological data, and the temperature fitting curve was used as the temperature boundary condition. Under different filling quantities, the temperature field of the roadbed was simulated for a freeze-thaw cycle, and the temperature curve changes were analyzed. The results indicate that as the filling height increases, the freezing depth line also increases accordingly. When the filling height is 2.5m, the maximum freezing depth at the roadbed is 1.7m. In a freeze-thaw cycle, the freezing process of soil develops from top to bottom, and the melting process develops in two directions: from top to bottom and from a certain depth of soil upwards, with the characteristics of "unidirectional freezing and bidirectional melting". The freezing period starts from early December of each year to the end of March of the following year, and completely melts until the end of April. Melting develops faster than freezing.

Analysis of Residual Stresses in Curved Cutouts of Steel Box Girder Transverse Diaphragms

In order to analyze the characteristics of cutting residual stress distribution at the arc‐shaped cutout of steel box girder diaphragm and to study its fatigue cracking mechanism. Taking Xia Zhang Bridge as the engineering background, this paper proposes a systematic method for calculating the residual stress field at the arc‐shaped cutout of the diaphragm. First, a mathematical model of the cutting heat source was established for predicting the temperature field changes during the cutting process of the diaphragm. Then, a 3D thermoelastic‐plastic finite element model was established using Abaqus to parametrically analysis the residual stresses during the fabrication of the transverse spacer. The results show that the cutting heat source creates a “thermal stagnation” effect at the curved notch, which leads to the local metallurgical transformation of the metal surface layer, which is unfavorable to its fatigue performance. The residual stresses are mainly concentrated near the cutting line, and the transverse residual stresses are lower at the free edge of the cutting line, which is easy to crack, and higher in the middle of the arc section of the arc notch. Inside the transverse bulkhead, at 14.5 mm from the free edge of the cut, in addition to the existence of high longitudinal residual tensile stress, its transverse residual tensile stress is also high, with a peak value of 199.3 MPa. Thermal cutting produces high residual tensile stress at the free edge, and the tensile stress cycle formed under the combined effect of wheel load is one of the reasons for the formation of initial fatigue cracks.

Heat transfer performance of phase change energy storage building materials and its application in energy efficient buildings

The author proposes a phase change heat storage component combined with the light wall interior to improve the heat storage performance. Numerical modelling of the composite wall was performed using the finite element program COMSOL connected to Multiphysics simulation, and its accuracy was verified. In order to optimize the use of phase change data and the benefit of phase change temperature, the phase change of the heating device was carried out, and the difference in the development efficiency of the thermal storage performance of the two types of light walls was obtained from the ribs in the thermal phase phase exchanger compared. The results show that the long and thin fins adjust the temperature and flow field changes of the paraffin to the corresponding fin gap and improve the heat transfer rate, 44.8 and 26.3, respectively, the aerated concrete combined wall heat storage and heat release time, added short ribs known need, and the connected wall delay time is not affected by external heat. The mature thermal insulation and thermal insulation time of the polystyrene board composite wall were shortened by 20.8 and 52.9, respectively. Ribs are able to improve heating efficiency and retain heat in the broken walls of polystyrene panels. The author?s research can provide a rationale for the design and use of phase change thermal storage.

FEM model optimization study of mechanical properties and material selection in stamping process

Abstract This paper establishes a finite element model of stamping and forming and proposes solution algorithms for static and dynamic forces. The finite element simulation of the hot stamping process is carried out to analyze the thermophysical parameters of BR1500HS ultra-high-strength steel sheet material and H13 steel mold material. Set the temperatures of austenitic material in the transfer process and molding process, obtain the rheological stress data of BR1500HS ultra-high-strength steel plate during plastic deformation at high temperature, and determine the basic mechanical properties of the material at high temperature. A geometric finite element model of thermal-force-phase coupling of the hot stamping and forming process is established to simulate the temperature field change of the steel plate during the hot stamping and forming process by combining the process conditions and process parameters. At the same time, the ultra-high-strength boron steel 22MnB5 is selected to simulate the hot forming and tempering process of U-shaped parts made of high-strength steel sheet material, and the feasibility of the finite element model is verified. Different hot stamping process parameters are set to analyze the forming quality of both BR1500HS ultra-high strength steel and ultra-high-strength boron steel 22MnB5. When the stamping speed is increased from 50mm/s to 100mm/s, the maximum equivalent force of BR1500HS ultra-high strength steel decreases, and thus, when the stamping speed is 100mm/s and the holding time is 5s, the part forming performance is better, which meets the requirements of the gradient performance hot stamping process.

Numerical simulation of fracture temperature field distribution during oil and gas reservoir hydraulic fracturing based on unsteady wellbore temperature field model

In the hydraulic fracturing oil and gas reservoir, the temperature variation of the fracturing fluid has a great impact on its flow and rheology, affecting the sand-carrying capacity and friction resistance of the fracturing fluid, and also affecting the settling speed of proppant in the fracture, thus changing the sand setting profile and sand laying concentration, and finally affecting the geometry of the fracture. Based on the energy balance and continuity equations, a numerical model for the distribution of wellbore temperature field in an extended-reach well is developed, and a variation law for the wellbore and reservoir temperature fields during fracturing also is formulated. A 3D mathematical model of the temperature distribution in hydraulic fracture and near-fracture formations has been developed based on heat transfer theory and finite-difference methods, taking into account the temperature gradients of fracture length and height according to the energy balance principle and fracture fluid continuity equations. The sensitivity factors of the temperature field are clarified, the wellbore temperature field and the fracture matrix temperature field model are coupled, and the influence rule of the temperature field change of the construction layer on the fracture shape while fracturing is revealed, which provides a theoretical basis for the hydraulic fracturing design optimization.

Monitoring experiment and simulation on solidification of DNAN based melt‐cast explosive with FBG sensors

AbstractIn order to obtain the change rule of the temperature field and the mechanism of defect formation during the solidification process of melt‐cast explosive, the temperature field change data were tested during the solidification process of DNAN based melt‐cast explosive by using an arrayed spatially distributed Fiber Bragg Grating (FBG) temperature sensor device. The temperature field variation during the solidification experiment was obtained under the condition that the cooling rate of the boundary water‐bath temperature was 0.2 °C/min. On the basis of the solidification experiments, the macroscopic solidification process of small‐caliber grenade at different boundary cooling rates was simulated using ProCAST software. The simulation results show that when the boundary cooling rate is 0.2 °C/min, the temperature fields during the solidification process of DNAN based melt‐cast explosive are in good agreement with that of the experimental monitoring points; the size of the melt‐cast charge defects decreases as the boundary cooling rate becomes smaller; and the location of the charge defects is closer to the tail of the grenade as the cooling rate decreases. In addition, a mesoscopic model of DNAN based melt‐cast explosive was established in the paper. At the mesoscopic level, the generation, formation, and evolution of charge defects in DNAN based melt‐cast explosive during solidification were investigated. The study results provide theoretical guidance for the formulation design and process optimization of DNAN based melt‐cast explosives, as well as for improving the charge quality of ammunition.

Geosynthetic materials properties analysis suitable for controlling reflective cracks in asphalt concrete

Reflective cracks appearing in the new asphalt concrete layer laid during reconstruction over the existing concrete or asphalt concrete pavement is the main cause of premature highways failure. Cracks of this type appear over defects in the old pavement and grow through the new pavement under the influence of vehicle loads and fluctuations in the temperature field. One of the common ways to combat reflective cracks is the use of an intermediate reinforcing layer made of special geosynthetic material, redistributing part of the loads. The paper proposes a multilayer pavement structural model and a temperature field change model based on the design documentation of the M-11 «Neva» highway and data from the temperature monitoring station. Temperature stresses сalculation arising in reinforced asphalt concrete layers in the existing crack vicinity of the old pavement is performed by the finite element method using the approximate method of Hills and Brien, reducing the calculation to the sequence of solving problems of linear elasticity theory. The dependencies of asphalt concrete rigidity modulus on temperature and time of load action are calculated on the basis of penetrative index and the binder softening temperature, taking into account the inevitable aging of the binder during paving and pavement operation. It is shown that significant reduction of dangerous tensile stresses in asphalt concrete is possible at reinforcement with geogrids with maximum tensile strength not lower than 100 kN/m, made on the basis of high-modulus glass or carbon fibers, under condition of joint work of asphalt concrete and reinforcing layers in the absence of mutual slippage.

Magnetic behavior of a ferrimagnetic MXene-like lattice: Monte Carlo study

In this study, we performed extensive Monte Carlo simulations to comprehensively analyze the magnetic properties of a single-layer MXene-like lattice. Our investigation involved the exploration of transition temperatures and the behavior of hysteresis cycles, all influenced by a series of key physical parameters. Additionally, we carefully mapped the magnetization as a function of temperature and crystal field, introducing variations in the exchange coupling to unveil their impact on the transition temperature. Furthermore, we investigated the behavior of hysteresis loops, complexly dissecting their responses to changes in exchange coupling, temperature, and crystal field. Significantly, our results highlight the central role of the crystal field in the formation of magnetization plateaus, thus providing promising avenues for applications in nanotechnology and advanced memory storage systems.

Study on the leakage morphology and temperature variations in the soil zone during large-scale buried CO2 pipeline leakage

In the CCUS technology chain, buried CO2 pipelines are inevitable under special terrain conditions. Due to the concealment and the complexity of the soil, they have a higher possibility of leakage. However, there is limited research on buried CO2 pipeline leakage processes. In this study, authors used existing industrial-scale pipelines as CO2 storage containers and constructed a large-scale buried CO2 pipeline experimental system. The leakage hole size and direction were considered to investigate the leakage morphology and temperature changes in the soil. The results showed that during the small-hole leakage, dry ice spheres were formed, which adhered to the pipeline. According to the change of temperature field, the dry ice spheres expanded towards weak areas in the soil, rather than strictly along the jet direction. The volume of dry ice spheres generated in the upward leakage process was the largest, while the volume was the smallest in the downward leakage process. Due to the soil resistance, the volume of dry ice spheres generated in the 3 mm leakage process was always greater than 9 times that of the 1 mm leakage process. The experimental results provide important references for optimizing leakage detection systems and conducting leakage risk assessments.

Experimental investigation of in situ combustion (ISC) in heavy oil thermal recovery

With the intensification of global climate change, there is an urgent need to change the energy structure of oil and gas to reduce the impact on the environment. As a thermally enhanced oil recovery technique, in situ combustion (ISC) is very important for reducing carbon emissions in the petroleum industry through the comprehensive utilization of oil displacement and storage in reservoirs. In this paper, the similarity parameters of a three-dimensional (3D) physical simulation of ISC were determined, the temperature field changes in the combustion process were monitored in real time, and a 3D field map was obtained. The oxidation characteristics of heavy oil were examined via thermogravimetry (TG), and the results showed that the oxidation process of heavy oil had three stages. The experimental results indicated that ISC could greatly increase the reservoir temperature, improve the quality of crude oil through high-temperature cracking, reduce the viscosity of crude oil and enhance the oil fluidity. The recovery factor from the ISC reached 53.27%. The formation of the coking zone was caused by various chemical and physical changes that occurred at high temperatures. Moreover, the formation process led to a concentration of the remaining oil in the small-aperture channels in the coking zone; this reduced the fluidity and increased the production difficulty. This study could provide guidance for the development of heavy oil reservoirs.

Effects of laser power and printing speed on the temperature field during selective laser melting of aluminum alloy

Additive manufacturing (AM) has significantly transformed the manufacturing industry and found diverse applications. Selective laser melting (SLM), as a common and valuable rapid prototyping technology in AM, is also a very important technology. In SLM, temperature is a very important parameter, and parameters such as melting time and manufacturing speed are highly correlated with temperature. However, temperature is not easy to measure in real-time, and it is convenient to study the changes in temperature field through numerical simulation. This paper explores the quantitative impact of printing speed and laser power on the temperature field through simulation. The peak temperature decreases with increasing printing speed, but increases with increasing laser power. The high temperature affected area is mainly related to the printing speed and decreases as the printing speed increases. The relevant results can provide guidance and reference for the application of SLM engineering.

Fluctuation of Magnetic Field in Magnetic Nano-Particles Thermometer

In this study, some important factors have been identified for the fluctuation of the magnetic field over time, which provides a basis for improving the temperature measurement accuracy and long-term stability of the magnetic nanoparticles thermometer (MNPT). We improved the mathematical model between the relative error of the magnetic induction intensity and the temperature measurement error of MNPT. The simulation founded that when the relative error of the magnetic induction intensity is kept within the range of <0.01%, the temperature measurement error is less than 0.1 K. Then, the multi-physics (magnetic field, temperature field, and thermal stress field) coupling relationship in the Helmholtz coil is established. During the coupling process, the temperature field of the Helmholtz coil affects the resistance of coil wire, and its thermal stress field is affected by the temperature field, which also changes the coil radius. After the temperature field and thermal stress field change, the magnetic field fluctuates immediately. Further simulation found that the problem of coil temperature rise becomes more serious as the size of the Helmholtz coil increases. The method of forced air cooling can make the fluctuation of the large Helmholtz coil magnetic field < 0.01%, and improve the measurement accuracy of MNPT.