Analysis and verification of electrodynamic force,thermal stress and current sharing for CRAFT converter structure design

In the design realm of fusion power supplies,structural components play a pivotal role in ensuring the safety of fusion devices.To verify the reliability of the converter structure design at the Comprehensive Research Facility for Fusion Technology(CRAFT),meticulous analysis of the converter's dynamic impact is carefully performed based on the worst fault current(400k A),firstly.Subsequently,the thermal stress analysis based on the maximum allowable steadystate temperature is finished,and the equivalent thermal stress,thermal deformation,maximum shear stress of a single bridge arm and the whole converter are studied.Furthermore,a simple research method involving the current-sharing characteristics of a bridge arm with multithyristor parallel connection is proposed using a combination of Simplorer with Q3D in ANSYS.The results show that the current-sharing characteristics are excellent.Finally,the structural design has been meticulously tailored to meet the established requirements.

Operation optimization of prefabricated light modular radiant heating system:Thermal resistance analysis and numerical study

The utilization of prefabricated light modular radiant heating system has demonstrated significant increases in heat transfer efficiency and energy conservation capabilities.Within prefabricated building construction,this new heating method presents an opportunity for the development of comprehensive facilities.The parameters for evaluating the effectiveness of such a system are the upper surface layer’s heat flux and temperature.In this paper,thermal resistance analysis calculation based on a simplified model for this unique radiant heating system analysis is presented with the heat transfer mechanism’s evaluation.The results obtained from thermal resistance analysis calculation and numerical simulation indicate that the thermal resistance analysis method is highly accurate with temperature discrepancies ranging from 0.44℃ to−0.44℃ and a heat flux discrepancy of less than 7.54%,which can meet the requirements of practical engineering applications,suggesting a foundation for the prefabricated radiant heating system.

Effect of FeSi additive in dual-chamber sample cup on thermal analysis characteristic values and vermiculating rate of compacted graphite iron

Thermal analysis plays a key role in the online inspection of molten iron quality.Different solidification process of molten iron can be reflected by thermal analysis curves,and silicon is one of important elements affecting the solidification of molten iron.In this study,FeSi75 was added in one chamber of the dual-chamber sample cup,and the influences of FeSi75 additive on the characteristic values of thermal analysis curves and vermiculating rate were investigated.The results show that with the increase of FeSi75,the start temperature of austenite formation TALfirstly decreases and then increases,but the start temperature of eutectic growth TSEF,the lowest eutectic temperature TEU,temperature at maximum eutectic reaction rate TEM,and highest eutectic temperature TERkeep always an increase.The temperature at final solidification point TEShas little change.The FeSi75 additive has different influences on the vermiculating rate of molten iron with different vermiculation,and the vermiculating rate increases for lower vermiculation molten iron while decreases for higher one.According to the thermal analysis curves obtained by a dual-chamber sample cup with 0.30wt.%FeSi75 additive in one chamber,the vermiculating rate of molten iron can be evaluated by comparing the characteristic values of these curves.The time differenceΔtERcorresponding to the highest eutectic temperature TERhas a closer relationship with the vermiculating rate,and a parabolic regression curve between the time differenceΔtERand vermiculating rateηhas been obtained within the range of 65%to 95%,which is suitable for the qualified melt.

Static and Thermal Analysis of Aluminium (413,390,384 and 332) Piston Using Finite Element Method

The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.

Research Characteristics of Thermal Comfort of Urban Block Landscape Based on Knowledge Graph Analysis

The landscape environment of urban blocks plays a significant role in improving the comfort of urban thermal environment and promoting green and high-quality development.The 342 papers related to the research on the impact of urban block landscape environment on thermal comfort in China,collected by CNKI(China National Knowledge Infrastructure)from 2002 to 2022,are used as the research object.Through bibliometric statistical analysis,LLR algorithm,and cluster analysis,the current research status of the impact of urban block landscape environment on thermal comfort in China is analyzed and processed,and its external characteristics are identified.Using the information visualization software CiteSpace,the research topics in the field of the impact of urban block landscape environment on thermal comfort are presented in the form of knowledge graphs.Through co-occurrence analysis of keywords and trend of word frequency changes,the development trends of research hotspots and cutting-edge fields of the impact of urban block landscape environment on thermal comfort are determined,hoping to provide reference for future research in this field.

Modal and Thermal Analysis of a Modified Connecting Rod of an Internal Combustion Engine Using Finite Element Method

The connecting rod is one of the most important moving components in an internal combustion engine. The present work determined the possibility of using aluminium alloy 7075 material to design and manufacture a connecting rod for weight optimisation without losing the strength of the connecting rod. It considered modal and thermal analyses to investigate the suitability of the material for connecting rod design. The parameters that were considered under the modal analysis were: total deformation, and natural frequency, while the thermal analysis looked at the temperature distribution, total heat flux and directional heat flux of the four connecting rods made with titanium alloy, grey cast iron, structural steel and aluminium 7075 alloy respectively. The connecting rod was modelled using Autodesk inventor2017 software using the calculated parameters. The steady-state thermal analysis was used to determine the induced heat flux and directional heat flux. The study found that Aluminium 7075 alloy deformed more than the remaining three other materials but has superior qualities in terms of vibrational natural frequency, total heat flux and lightweight compared to structural steel, grey cast iron and titanium alloy.

Non-isothermal Kinetic Analysis on the Thermal Decomposition of the Phase 517 from Hydration Product of Magnesium Sulfide Cement

In order to better understand the thermodynamic properties of magnesium oxysulfate(MOS)cement,pure reagent was analyzed to prepare magnesium sulfide cement,non-isothermal kinetics calculation of the main hydration products was also carried out,and the conversion process of magnesium sulfide cement 517 phase at different temperatures was investigated.Composition of magnesium sulfide cement prepared was measured by XRD technique,and decomposed by a comprehensive thermal analyzer,and DSC curves of magnesium sulfide cement under different temperature rising rates were processed by Kinssinger method and Dolye-Ozawa method.According to the TG-DSC curves of magnesium sulfide cement,the thermal decomposition reaction process can be divided into five stages under normal conditions.The DSC curve was processed by Kinssinger method and Dolye-Ozawa method,and the kinetic analysis was carried out to calculate the 517 phase activation energy of magnesium sulfide cement.The three stages correspond to different activation energies.Therefore,flame retardant mechanism and thermal decomposition mechanism of magnesium sulfide cement based materials are deduced.

Analysis of influence of heat exchangerfouling on heat transfer performancebased on thermal fluid coupling

A study on heat transfer performance by thermal fluid coupling simulation for the fouling in a shell-tube heat exchanger used in engineering was presented. The coupling simulation was performed in a fluid and solid domains under three different fouling conditions: fouling inside the tube, fouling outside the tube, and fouling inside the shell. The flow field, temperature, and pressure distributions in the heat exchanger were solved numerically to analyze the heat transfer performance parameters, such as thermal resistance. It is found that the pressure drop of the heat exchanger and the thermal resistance of the tube wall increase by nearly 30% and 20%, respectively, when the relative fouling thickness reaches 10%. The fouling inside the tube has more impact on the heat transfer performance of the heat exchanger, and the fouling inside the shell has less impact.

Thermal Analysis of Turbine Blades with Thermal Barrier Coatings Using Virtual Wall Thickness Method

Avirtual wall thicknessmethod is developed to simulate the temperature field of turbine bladeswith thermal barrier coatings(TBCs),to simplify the modeling process and improve the calculation efficiency.The results show that the virtualwall thickness method can improve themesh quality by 20%,reduce the number ofmeshes by 76.7%and save the calculation time by 35.5%,compared with the traditional real wall thickness method.The average calculation error of the two methods is between 0.21%and 0.93%.Furthermore,the temperature at the blade leading edge is the highest and the average temperature of the blade pressure surface is higher than that of the suction surface under a certain service condition.The blade surface temperature presents a high temperature at both ends and a low temperature in themiddle height when the temperature of incoming gas is uniformand constant.The thermal insulation effect of TBCs is the worst near the air film hole,and the best at the blade leading edge.According to the calculated temperature field of the substrate-coating system,the highest thermal insulation temperature of the TC layer is 172.01 K,and the thermal insulation proportions of TC,TGO and BC are 93.55%,1.54%and 4.91%,respectively.

Study of main factors influencing unsteady-state temperature drop in oil tank storage under dynamic thermal environment coupling

With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperature drop in storage tanks under actual dynamically changing environments, this paper considers the influence of dynamic thermal environment and internal crude oil physical properties on the fluctuating changes in crude oil temperature. A theoretical model of the unsteady-state temperature drop heat transfer process is developed from a three-dimensional perspective. According to the temperature drop variation law of crude oil storage tank under the coupling effect of various heat transfer modes such as external forced convection, thermal radiation, and internal natural convection, the external dynamic thermal environment influence zone, the internal crude oil physical property influence zone, and the intermediate transition zone of the tank are proposed. And the multiple non-linear regression method is used to quantitatively characterize the influence of external ambient temperature, solar radiation, wind speed, internal crude oil density, viscosity, and specific heat capacity on the temperature drop of crude oil in each influencing zone. The results of this paper not only quantitatively explain the main influencing factors of the oil temperature drop in the top, wall, and bottom regions of the tank, but also provide a theoretical reference for oil security reserves under a dynamic thermal environment.

Variational analysis of thermomechanically coupled steady-state rolling problem

A steady-state, rigid-plastic rolling problem for temperature and strain-rate dependent materials with nonlocal friction is considered. A variational formulation is derived, coupling a nonlinear variational inequality for the velocity and a nonlinear vari- ational equation for the temperature. The existence and uniqueness results are obtained by a proposed fixed point method.

EFFICIENT STEADY-STATE ANALYSIS METHOD FOR CLOSED-LOOP PWM SWITCHING CONVERTERS

An analysis technique of steady state and stability for closed-loop PWM DC/DC switching converters is presented. Using this method, the closed-loop switching converter is transformed into an open-loop system. By means of the fact that in steady state, the two boundary values are equal in one switching period. The exponential matrix is evaluated by precise time-domain-integration method, and then the related curve between feedback duty cycle and the input one is obtained. Not only can the steady-state duty cycle be found from the curve, but also the stability and stable domain of the system. Compared with other methods, it features with simplicity and less calculation, and fit for numerical simulation and analysis for closed-loop switching converters. The simulation results of examples indicate the correctness of the presented method.

Thermal analysis for brake disks of SiC/6061 Al alloy co-continuous composite for CRH3 during emergency braking considering airflow cooling

The mass of high-speed trains can be reduced using the brake disk prepared with SiC network ceramic frame reinforced 6061 aluminum alloy composite （SiCn/Al）. The thermal and stress analyses of SiCn/Al brake disk during emergency braking at a speed of 300 km/h considering airflow cooling were investigated using finite element （FE） and computational fluid dynamics （CFD） methods. All three modes of heat transfer （conduction, convection and radiation） were analyzed along with the design features of the brake assembly and their interfaces. The results suggested that the higher convection coefficients achieved with airflow cooling will not only reduce the maximum temperature in the braking but also reduce the thermal gradients, since heat will be removed faster from hotter parts of the disk. Airflow cooling should be effective to reduce the risk of hot spot formation and disc thermal distortion. The highest temperature after emergency braking was 461 °C and 359 °C without and with considering airflow cooling, respectively. The equivalent stress could reach 269 MPa and 164 MPa without and with considering airflow cooling, respectively. However, the maximum surface stress may exceed the material yield strength during an emergency braking, which may cause a plastic damage accumulation in a brake disk without cooling. The simulation results are consistent with the experimental results well.

Non-isothermal kinetic analysis of thermal dehydration of La_2(CO_3)_3·3.4H_2O in air

The single phase La2（CO3）3·3.4H2 O was synthesized by hydrothermal method. The thermal decomposition and intermediates and final solid products of La2（CO3）3·3.4H2O from 30 to 1000 °C were characterized by XRD, FTIR and DTA-TG. The kinetics of dehydration of La2（CO3）3·3.4H2O in the temperature range of 30-366 °C was investigated under non-isothermal conditions. Flynn-Wall-Ozawa and Friedman isoconversion methods were used to calculate the activation energy and analyze the reaction steps; multivariate non-linear regression program was applied to determine the most probable mechanism and the kinetic parameters. The results show that the thermal dehydration of La2（CO3）3·3.4H2O is a kind of three-step competitive reaction, and controlled by an n-order initial reaction followed by n-order competitive reaction（FnFnFn model）. The activation energy matching with the most probable model is close to value obtained by Friedman method. The fitting curves match the original TG-DTG curves very well.

NUMERICAL PREDICTION OF AIRCRAFT HYDRAULIC SYSTEM BASED ON THERMAL DYNAMIC ANALYSIS

A mathematical model of principal elements of the aircraft hydraulic system is presented based on the heat transfer theory. The dynamic heat transfer process of the hydraulic oil and the pump shells within an aircraft hydraulic system are analyzed by the difference method. A kind of means for the prediction to variational trends of the aircraft hydraulic system temperature is provided during operation. The numerical prediction and simulation under the operational conditions are presented for ground trial running and the decelerated operation in flight. Computational results show that there is a good coincidence between the experimental data and the numerical predictions.

THERMAL ANALYSIS OF FRICTIONAL DISK IN SPEEDING WET CLUTCH

Multi-frictional disks are employed to transmit the torque in speeding wetclutch, and the oil thickness within frictional disks could be adjusted for practical outputspeeding. As oil combined with alpha-hydrocarbon or polyester is getting widely used as lubricantand the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundarylubrication and contact situation, established the thermal analysis model for investigating thebehavior of frictional disks in speeding wet clutch, which covers the power-law fluid model,Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, meanenergy equation, and heat conduction equation. The formulas in the model are deduced. The numeralcalculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and loadare presented. Thermal effect should be considered during the hydrodynamic lubrication and largertransmitting torque makes earlier entrance to mixture lubrication.

Thermal–hydraulic analysis of space nuclear reactor TOPAZ-Ⅱ with modified RELAP5

With the advantages of high reliability, power density, and long life, nuclear power reactors have become a promising option for space power. In this study, the Reactor Excursion and Leak Analysis Program 5(RELAP5), with the implementation of sodium–potassium eutectic alloy(NaK-78) properties and heat transfer correlations, is adopted to analyze the thermal–hydraulic characteristics of the space nuclear reactor TOPAZ-Ⅱ.A RELAP5 model including thermionic fuel elements(TFEs), reactor core, radiator, coolant loop, and volume accumulator is established. The temperature reactivity feedback effects of the fuel, TFE emitter, TFE collector,moderator, and reactivity insertion effects of the control drums and safety drums are considered. To benchmark the integrated TOPAZ-Ⅱ system model, an electrical ground test of the fully integrated TOPAZ-Ⅱ system, the V-71 unit,is simulated and analyzed. The calculated coolant temperature and system pressure are in acceptable agreement with the experimental data for the maximum relative errors of 8 and 10%, respectively. The detailed thermal–hydraulic characteristics of TOPAZ-Ⅱ are then simulated and analyzed at the steady state. The calculation results agree well with the design values. The current work provides a solid foundation for space reactor design and transient analysis in the future.

MINERALIZATION AGES OF GOLD-HYDROTHERMAL DEPOSITS IN NORTHERN ZONE OF EASTERN KUNLUN MOUNTAINS BASED ON FISSION TRACK ANALYSIS

The age of mineralization in a mining area is a primary factor in various researches related to ore\|forming process. It is that the uncertainty of mineralization ages of gold ore deposits in northern zone of eastern Kunlun Mountains, Qinghai Province, restrains to probe the relationship of the deposits to the regional tectonic evolution. This paper documents the fission track method used to determine the ages of gold ore deposits in eastern Kunlun Mountains and considers the implication for the origin of the deposits.Eastern Kunlun Mountains is the northern part of the Qinghai—Tibet Plateau and is of three deep\|seated fault belts in about EW extension. This work mainly includes three gold ore districts. All of them, in the north of Mid\|Kunlun fault belt, belong to northern part of eastern Kunlun Mountains. The Yanjingou district, with geographical coordinate 96°00’E and 36°10’N, is located 60 km north of Hongqigou district . Both of them are large, typical tectonoalteration gold deposits and were formed in similar geological setting. Hongshuihe ore district is located 50 km east of Yanjingou district and includes tectonoalteration and magmatic cryptoexplosive gold deposits. Outcroped strata are dominantly Jinshuikou Group metamorphic rocks of Lower Proterozoic erathem. The occurrence area of igneous rocks, especially granitoid, accounts for about 90% in first two districts and become less in Hongshuihe district. The gold deposits occur in NW\|striking fault belts. The Rb\|Sr isochron age and K\|Ar isotopic age of Moyite relevant to the gold mineralization are respectively 228 25Ma and 207 1Ma. Rb\|Sr dating of diorite porphyrite is 209 09Ma. Sericite selected from Yanjingou orebody has 252 9Ma K\|Ar age. The ore in Hongqigou district has 197Ma K\|Ar age and 210Ma model age of Pb isotope of galena.

Thermal deformation of aluminum alloy casting materials for tire mold by numerical analysis

Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial field.The temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature results.The thermal deformation was closely related to the temperature difference between the surface and inside of the casting.The numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting material.Also,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.

3D FE Analysis of Thermal Behavior of Billet in Rod and Wire Hot Continuous Rolling Process

An FE model was developed to study thermal behavior during the rod and wire hot continuous rolling process. The FE code MSC. Marc was used in the simulation using implicit static arithmetic. The whole rolling process of 30 passes was separated and simulated with several continuous 3D elastic-plastic FE models. A rigid pushing body and a data transfer technique were introduced into this model. The on-line experiments were conducted on 304 stainless steel and GCr15 steel hot continuous rolling process to prove the results of simulation by implicit static FEM. The results show that the temperature results of finite element simulations are in good agreement with experiments, which indicate that the FE model developed in this study is effective and efficient.