最新刊期
卷 53 ， 期 7 ， 2019
- 摘要：In the present study, the transient thermal characteristics of cryogenic target during the thermal shield removal process are numerically studied, and optimal temperature control schemes are proposed to improve the target temperature distribution and to avoid ice quality deterioration.An unsteady numerical model is established for the cryogenic target with multiple thermal shields based on the Boussinesq assumption and the discrete coordinate radiation model.The transient thermal characteristics of the cryogenic target during the removal of thermal shield are analy-ed under different hohlraum pressures and sealing film transmittances, and the numerical results of removal thermal shield under different control schemes of cooling rings are analy-ed.The results show that the temperature on the capsule surface rises precipitously in accompany with the deterioration of temperature uniformity after removing the thermal shield.As the helium pressure in hohlraum increases, the maximum temperat关键词：cryogenic target;thermal shield;transmittance;transient characteristic;numerical simulation428|5|5更新时间：2025-07-09
- 摘要：In recent years, more and more attention has been paid to the development of ocean resource.Especially in the deep ocean, the development of the resource and energy usually depends on the large floating structures.Multibody platforms are usually used in VLFS(very large floating structure)to ensure the stability of the floating structure under the impact of sea waves.Because of the multibody structure, the hydrodynamic characteristics of the platform are very complex.This paper proposes a full Lagrangian algorithm by coupling moving particle semi-implicit method(MPS)and discrete element method(DEM).A two-dimensional numerical wave tank was established and the wave generation model was modified to enhance the accuracy of the numerical wave.Moreover, the wave absorption model was improved and the computation cost was reduced by 12.1%.Furthermore, the motion response of moored multibody platforms under the influence of regular waves was analy-ed, and the dynamic relationship between sub-pl关键词：MPS-DEM;multibody platform;numerical wave tank;wave generation;wave absorption306|5|2更新时间：2025-07-09
- 摘要：In order to investigate the effect of ethanol blending in iso-octane on the ignition delay times(IDT)under high temperature conditions, the auto-ignition characteristics of ethanol/isooctane mixtures were studied.High temperature ignition characteristics and chemical reaction mechanism were investigated using a shock-tube platform at two initial pressures of 0.2 MPa and 1 MPa, with a temperature range from 1 100 to 1 900 K and a stoichiometric ratio of 1:1, for isooctane blended with different molar percentages of ethanol(pure isooctane, E50, E75 and pure ethanol).The results showed that the IDT of ethanol/isooctane mixtures decreases with the ethanol blending ratio and pressure, and decreases with the increase of temperature at high temperatures.The logarithm of the IDT is approximately linear to the reciprocal of the temperature.The Arrhenius formula was fitted by multivariate linear regression and verified that the Nour Atef mechanism agreed well with experiment.Through the analyses关键词：isooctane-ethanol blended fuel;ignition delay time;shock-tube;chemical kinetics283|5|0更新时间：2025-07-09
- 摘要：To solve the problem of low working efficiency and high energy loss caused by high negative pressure hydraulic cylinder systems, this paper proposes a method for redesigning the flow regenerating hydraulic valve in high negative pressure hydraulic cylinder system.Taking the common hydraulic valve used in a common type of earthmoving mechanical cylinder as the research object and using factorial analysis approach, it was found that the fixed liquid resistance parameter of the non-regenerative hydraulic circuit has a significant effect on the efficiency of flow regenerating hydraulic valve.To solve the problem of low oil supply efficiency, a novel method was proposed, which can change the fixed liquid resistance of the non-regenerative hydraulic circuit to a variable liquid resistance and hence forming a differential control combined with the variable liquid resistance of the regenerative hydraulic circuit.Based on the method, the structural redesign of the hydraulic valve, with four str关键词：high negative pressure cylinder;flow regeneration;energy efficiency analysis;response surface methodology;liquid resistance295|5|4更新时间：2025-07-09
- 摘要：To study the characteristics of flow resistances in a stratified debris packed bed after severe accident in nuclear reactor, the paper reports an experimental study on the pressure drops of single-/two-phase flow through the vertically and hori-ontally stratified beds.Three types of particular beds were designed and constructed with different si-es of glass spheres.Type-1 bed is a homogeneous bed consisting of single si-e spheres.While Type-2 bed and Type-3 bed are stratified beds with the structure of hori-ontal stratification and vertical stratification, respectively.Both single- and two-phases flow tests were carried out, and the pressure drops were measured.The results showed that, for a hori-ontally stratified bed with larger particles atop and smaller particles down, the pressure drops in each part of hori-ontally stratified bed are almost the same as those of homogeneous bed packed with the same si-e spheres.It seems that the stratification has less effect on the pressure drops关键词：stratified packed bed;flow characteristics;pressure drop;porous media280|5|0更新时间：2025-07-09
- 摘要：In order to study the frosting behavior on the cold surface at -60 -, a test rig based on cascade refrigeration system for frosting visuali-ation on the surface of hori-ontal circular tube is designed and built.The frosting behavior on the outer surface of the hori-ontal tube in the channel of double-pipe heat exchanger was tested when the moist air was sweeping down the tube.The thickness and growth rate of frost were emphatically analy-ed.The results showed that the growth rate of the frost thickness on the surface at -60 - is faster than that on the cold surface at ambient temperature, which is about twice as fast as that on the cold surface at -15 -.However, the growth trends of both are similar.In addition, two different melting processes, i.e., the periodic melting and the rapid falling of the frost caused by collapse, were found and analy-ed.The thickness of the frost layer is greatly reduced due to collapse and melting.The frosting behavior on the hori-ontal tube surface at关键词：channel frosting;hori-ontal circular tube;growth rate;melting204|5|3更新时间：2025-07-09
- 摘要：To study the flow instability of an ultra-supercritical boiler under low load operation, this study established a one-dimensional single-channel model, and a general numerical model for the flow instability analysis of the ultra-supercritical boiler with different geometric structures and thermal parameters was established.Based on the good agreement between numerical and experimental results, the flow instability of water wall system of a 1 000 MW ultra-supercritical boiler in Qinyang Power Generation Company was numerically calculated(40% turbine heat acceptance).The influences of thermal line density on the import and export flow amplitude and time stability were analy-ed when the dynamic flow instability occurred in the circuit No.9 of the shortest tube on the front wall, the circuit No.32 of the longest tube on the left wall, and the circuit No.107 of the strongest heating tube in the upper furnace.The results showed that with the increase of the disturbance intensity of heat load关键词：ultra supercritical boiler;time-domain method;low-load operation;flow instability233|5|15更新时间：2025-07-09
- 摘要：Aiming at the problem of insufficient output power and torque caused by the large spark of a ship main converter unit, the influence of large spark on the operating characteristics of the unit was studied.The mathematical model of synchronous motor and direct current(DC)motor and the mechanical coupling equation of synchronous motor and DC motor were constructed by the equivalent circuit model, and the mathematical model of main converter unit was established.The simulation experiment showed that the main converter unit model had better control effect on the unit speed and terminal voltage amplitude under rated conditions.By analy-ing the commutation process of the DC motor armature current, the mechanism of spark generation in the main converter unit was clarified.Approximating the Cassie arc as a spark mathematical model, it was connected in series to the armature circuit of the DC motor to reali-e the virtual injection of large sparks.The simulation result showed that under the same关键词：main converter unit;spark;Cassie arc model;ripple coefficient;fault diagnosis316|5|0更新时间：2025-07-09
- 摘要：A combined method of customi-ed musculoskeletal multi-body dynamics(MBD)and finite element(FE)modelling is proposed to overcome the difficulties for evaluating the failure of implant under in vivo physiological loading conditions.Following the related data from an adult male, the subject-specific upper extremity musculoskeletal MBD model and the corresponding scapular fracture fixation FE model are established to simulate arm abduction and forward flexion movements with the musculoskeletal MBD software AnyBody and the FE software Abaqus.The glenohumeral joint forces and all muscle forces calculated by the MBD analysis are applied to the FE model, and von Mises stresses are obtained to investigate the validity of the new-designed locking plate compared with the traditional reconstruction plate under in vivo physiological loading conditions.The maximum glenohumeral joint forces reach 428 N and 379 N observed at 90- of abduction and 45- of flexion respectively.The corresponding maximum关键词：subject-specific;scapular locking plate;in vivo loading;musculoskeletal multi-body dynamics;finite element;biomechanics365|5|0更新时间：2025-07-09
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