最新刊期
卷 41 ， 期 7 ， 2007
- 摘要：Following the theoretical research on working process of screw compressors, the mathematical models for simulation of the thermodynamic performance and dynamic characteristics of the screw compressor are proposed, which are experimentally verified by means of recording the indicator diagrams(p-V diagrams)with a small pressure sensor embedded in the female rotor, the measurement of pressure pulsation in the discharge chamber and the forces acting on the rotors, and the visualization experiment on oil distribution in the compressor. It indicates the relation between the performance and the design parameters of the screw compressor. Simultaneously, the key technology for screw compressor is developed including profile design method, the cutter design, the soft package of SCCAD. Up to now, more than 50 models of twin screw compressor products have been developed and mass manufactured to meet the requirement of refrigeration, aerodynamic and petrochemical industry.关键词：screw compressor;design theory;key technology;development of series products4241|5|18更新时间：2025-12-08
- 摘要：With slot hot gas blowing, the secondary water droplet diameters and its distributions downstream of the hollow stationary blade were measured by Malvern droplet and particle size analysers. The tests were conducted at inlet gas wetness of 7.94%, an outlet gas velocity of 170 m/s, a slot width of 1.0 mm, a slot angle of 45°, temperature difference between hot gas and main gas of 50 ℃, and the slot position on concave or convex of the hollow stationary blade surface. The results show that the slot hot gas blowing could reduce the minimum and maximum diameters of secondary water droplets downstream of the stationary blade, The Sauter mean diameter of secondary water droplets could be reduced by 33.4%, and the water droplet diameter distribution became narrow. The larger the blowing pressure difference, the smaller the secondary water droplets, and the narrower the water droplet diameter distribution. This may be beneficial to reducing or preventing the rotational blade erosion. In addition, the slot located on the convex surface of hollow stationary blade was better than that on the concave surface in water removal.关键词：slot gas blowing;secondary water droplet;water removal performance3350|5|5更新时间：2025-12-08
- 摘要：采用数值求解基于多孔介质模型的Reynolds-averaged Navier-Stokes方程技术,对刷式密封内泄漏流动特性进行了详细的数值研究.根据刷式密封的泄漏量试验数据,确定了刷丝束多孔介质的渗透率系数.利用所确定的渗透率系数,数值计算和分析了7种压比和5种径向间隙条件下的某轴端刷式密封的泄漏量和泄漏流动形态,并且与迷宫式密封进行了比较.结果表明:在相同的压比下,刷式密封的泄漏量小于迷宫式密封;压比影响刷式密封的泄漏量,但对泄漏流动形态的影响可以忽略;径向间隙不仅影响刷式密封的泄漏量,而且影响泄漏流动形态;在相同的径向间隙下,压比越大则泄漏量越大;在相同的压比条件下,径向间隙越小则泄漏量越小.研究工作可对刷式密封在汽轮机中的应用提供理论依据和技术参考.关键词：刷式密封;多孔介质模型;泄漏流动;数值模拟3486|5|12更新时间：2025-12-08
- 摘要：分别采用激光全息摄影技术和高速数字摄影技术观察了柴油、甲醇和水乳化液喷雾在高温高压(773 K,3.1 MPa)环境中发生微爆现象的瞬间和全过程,证实了微爆现象的存在.由于微爆机理的复杂性,尚难以用数学方法准确描述该过程.实验分析表明:若环境温度处于“最佳温度”范围内,乳化液滴表面首先形成“无水层”,液滴内部形成一个水滴的概率很小,可能形成几个相对较大的水滴,只要其中一个较大水滴的蒸汽压力大于液滴的表面张力和环境压力之和,液滴就有可能发生微爆,微爆不仅与液滴直径、组分的质量分数和组分间的沸点差等乳化液的本身特性有关,而且环境温度和压力的影响也不容忽视.该研究可以为乳化液喷雾微爆过程的数学模拟提供参考.关键词：激光全息摄影;高速数字摄影;乳化液;微爆2936|4|5更新时间：2025-12-08
- 摘要：The experimental apparatus of micro-space ignition and combustion are designed to investigate the size effects of micro-space ignition and combustion by reducing the sizes of the combustors with premixed hydrogen/air. The experimental results in the micro-space show that the smaller the ignitable hydrogen concentration range, the shorter the gas fuel residence time. When the sizes of the combustors decrease from centimeter scale down to millimeter scale, the heat transfer loss increases obviously due to the growing of the ratio of surface to volume and the stable combustion is difficult to maintain due to flame quenching. It is suggested to adopt hydrogen possessing low quenching distance and ignition energy associated with pressure, insulation and catalysts. The plate capacitor spark electrodes for micro-space combustion with cantilever beam structures are designed and fabricated by evaporation, where the gap between two spark electrodes gets more than 10 μm and the thickness less than 0.2 μm. Smaller capacitance of the electrode leads to a longer igniting time. Electroplating is proposed after evaporation to deposit in relatively large volumes for microfabrication,thus 4 μm thickness of the electrode is obtained with increased single discharge energy.关键词：micro-engine;ignition;combustion;micro-size effect2970|5|1更新时间：2025-12-08
- 摘要：A novel radial flat heat pipe(RFHP)integrated with high power module instead of metal substrate was developed. Compared with metal substrate, the RFHP uses two-phase boiling heat transfer to diffuse heat in power module, and thus improve the thermal performance of the power module. The transient and steady heat transfer performance of the RFHP was experimentally measured and compared with that of copper substrate. Experiment result indicates that the RFHP has greater thermal diffusivity, and can reduce junction-to-case thermal resistance of the module. When power density is 176 W/cm2, the temperature difference on the condensation section is within 3 ℃. The longer time period for the chip to reach the same temperature during RFHP module start-up can avoid power uprush and raise the ability of resisting thermal impact.关键词：radial flat heat pipe(RFHP);heat transfer;substrate3166|6|1更新时间：2025-12-08
- 摘要：A TY1100 direct-injection diesel engine was equipped with an electronic controlled methanol low-pressure injection system. Methanol is injected into the induction port. The premixed mixture of methanol and air is ignited by pilot diesel. The experimental results show that the polytropic index of compression process of dual fuel engine decreases linearly while the ignition delay increases with the increase of the methanol mass fraction. Compared with the conventional diesel engine, the ignition delay increment of the dual fuel engine is about 1.5° at a methanol mass fraction of 62%,a speed of 1 600 r/min, and full load. With the elevation of the intake charge temperature from 20 ℃ to 40 ℃ and then to 60 ℃, the ignition delay of dual fuel engine decreases and is more obvious at high temperature. Moreover, with the increase of engine speed, the ignition delay of the dual fuel engine by time scale(ms)decreases clearly at all engine operating conditions. However, the ignition delay of the dual fuel engine increases remarkably by advancing the delivery timing of pilot diesel, especially at light engine loads.关键词：ignition delay;compression process;methanol;pilot diesel;dual fuel engine3005|5|4更新时间：2025-12-08
- 摘要：The nanoscale phenomenon of two identical circular cylinders arranged in a side-by-side configuration in steady cross-flow was investigated using molecular dynamics simulations with the Lennard-Jones potential model at a low Reynolds number(Re=22). L*/D*, the centre-to-centre pitch ratio, ranged from 1.0 to 2.0. Three basic flow patterns were observed and the results indicate that the characteristic ranges of the microscopic flow patterns are different from those of the macroscopic phenomenon. Single bluff-body vortex shedding range is L*/D*<1.1. Biased flow with synchronized vortex shedding range is 1.1关键词：molecular dynamics;flow around cylinders;bistable;Reynolds number3192|5|0更新时间：2025-12-08
- 摘要：Gas lubrication technology applied in a cryogenic turbo-refrigerator is outlined and discussed on the basis of the investigations of externally-pressurized gas bearing turbo-expander. In particular, the valuable experience to develop several different kinds of external-pressurized gas bearings including double row radial gas supply, double row tangential gas supply, multi-row tangential gas supply is presented and summarized. Moreover, the relationship between gas supply bearing clearance and whirling speed is deduced. The optimal bearing clearance is also obtained. It is found that the optimal bearing clearance will increase by 75% when a common radial feeding-hole bearing is changed to tangential feeding-hole bearing. Correspondingly, the whirling speed can be improved by 30%.关键词：气体润滑;静压气体轴承;透平膨胀机;制冷机;多排切向2936|5|5更新时间：2025-12-08
- 摘要：The kinetic property affected by the clearance between the outer rotor and the cylinder was analyzed with ignoring the influence of other clearances. The influence of the gap between gears was studied in detail. Numerical iterative method was employed in calculation for an example. The deflection angle of the outer rotor, the sequence number of teeth on the outer rotor taking part in the meshing process and the actual generating angle of the inner rotor were obtained. The result shows that the clearance between the outer rotor and cylinder will cause impact effect during the start-up process and the gap between gears will transform the ideal multi-point mesh into the actual one-point mesh. If the rotate speed of the shaft was constant, the gap would cause the speed fluctuation of the outer rotor.关键词：internal-meshing;rotary compressor;cycloid;kinetic relationship3122|5|0更新时间：2025-12-08
- 摘要：A novel framework for computer aided process planning is presented, where the whole procedure of process planning is divided into a sequence of stages or subtasks. Analyzing the characteristics of tasks like the requirement of design environment and safety, the browser/server or client/server is applied to the corresponding module so as to speed up the execution of the process planning task and improve the productivity. To communicate the manufacturing documents among different systems, a new data structure with three different segments to define the planning data is presented,and the manufacturing information can be transformed and stored as special format files to transfer the process planning documents over the internet. In addition, a special browser is developed for browsing the specified format files. Some operations on the planning procedure such as checking and verifying processes, can be carried out off-line.关键词：process planning;workflow;numeric control;feature category3010|5|0更新时间：2025-12-08
- 摘要：Analyzing the structural vulnerability of the process industry system, a new method for system safety based on the complex networks theory is proposed. The network model of the process industry system is constructed and the inherent topological structure characteristics are investigated. Subsequently, to study the cascade effect caused by the fault of a node in the network, a cascading failure model based on the basic characteristic parameters of the network is proposed, and then the damage of cascading failure triggered by a single node in the system is simulated. A case study of Tennessee-Eastman process is provided to illustrate the feasibility of the proposed method. The simulation results show that the mechanism of cascading failures can be analyses and understood from a complex network perspective, and the method enables to find the critical node and the crisp node of the process industry system for design the system of the safety control and failure prevention.关键词：流程工业系统;复杂网络;安全性分析;连锁故障2931|5|5更新时间：2025-12-08
- 摘要：The dynamic characteristics of negative stiffness Duffing system with delayed feedback control are investigated. Choosing time delay as the control parameter, the stability of trivial equilibrium is discussed by analyzing distribution of the roots of the associated characteristic equation. It is found that Hopf bifurcation occurs from trivial equilibrium when the delay passes through critical values, then the critical values and their relations with system control parameters are obtained. The effect of time delay on the forced vibration of system is evaluated with numerical method. The results show that the amplitude of stable period motion increases, some complex dynamical behaviors such as quasi-periodic motion and multiple periodic motion may occur, and the system gets out of control with the increase of time delay. Therefore the effect of time delay ought to be taken into sufficient consideration in the design of system control loop.关键词：Duffing system;negative stiffness;time delay;bifurcation;stability3218|5|0更新时间：2025-12-08
- 摘要：分析了基于交错轴传动的珩齿原理,导出珩磨轮与被珩齿轮在啮合点处的相对滑动速度的数学模型,根据该数学模型可以判定珩磨轮的节锥面是由珩磨轮齿数、公法线和与珩磨轮轴线平行的平面夹角所确定.在建立的珩磨轮齿面准均布网格点上,采用法线投影法计算各点的极限拨模导程,并通过比较凸齿面上最小拔模导程的最大值和凹齿面上最大拔模导程的最小值来判定是否存在拔模干涉.针对出现的拨模干涉,提出了拨模导程的优化方法,以及干涉的修正方案和齿面光顺过程.给出的珩磨轮设计的部分计算实例表明,珩齿技术可以在工业精加工方面得到广泛应用.关键词：螺旋锥齿轮;珩齿;拔模干涉3046|4|2更新时间：2025-12-08
- 摘要：The mathematical models of mechanical system, thermodynamic system and electromagnetic system of a compressor driven by moving-magnet linear motor were established on the basis of the control method that piston's displacement is changed by changing the triac's time of flow. The dynamic performance of the linear compressor was simulated. The voltage and current curves of the motor coil, and the stroke and top dead center of the piston were presented at different time of flow. The simulation results are in good agreement with experimental data. Considering influence of equivalent damping coefficient's changeability, motor parameter's veracity and algorithm, the deviation of the simulation results from the experimental data is less than 10%.关键词：compressor;moving-magnet linear motor;simulation;mathematical model;time of flow2867|5|4更新时间：2025-12-08
- 摘要：采用数值模拟方法研究湿地对周边区域空气的降温增湿效应,建立了空气、水气的流动与扩散混合模型,描述给定空间的传热传质过程.控制方程包括连续方程、动量方程、能量方程和水气守恒方程.对每一相各自的流动,采用k-ε双方程模型;对于两相的湍流流动,采用混合湍流模型.用FLUENT软件进行数值计算,得出给定区域的空气温度、相对湿度的空间分布.对实测案例进行了数值模拟,计算值与测定值符合良好,表明所建立的模型和计算方法可以很好地描述湿地对周边区域空气温度和湿度的影响.由等温线可以看到,低温空气的扩散在近湿地处,影响最大的区域距地面一定高度.冷空气从湿地边沿向远处及上下扩散,在温度最低区略有上升,到一定远处又下降至地面.对于相对湿度,在靠近湿地区域水气对地面附近的影响比气温影响明显,而远处水气对地面附近的影响不及气温影响大.关键词：湿地;降温增湿效应;数值模拟3260|4|4更新时间：2025-12-08
- 摘要：利用改进的激光三角测量法获得图像采集时丢失的高度信息,其相对误差小于0.4%,将该信息集成到伺服控制方程中就可以利用视觉信息来控制机械手在空间做三维运动.在图像空间控制机械手运动时,利用光学流方法获得每个采样周期后注射针在图像空间的位置,就可以消除系统存在的误差,使注射针沿预定的轨迹运动,完成细胞的注射.实验结果表明,利用该方法可以将轨迹误差从(11,10)像素,减小为(0,2)像素,从而方便地控制机械手在三维空间做精确定位和运动.关键词：细胞注射;光学流;激光三角测量;伺服控制2872|4|1更新时间：2025-12-08
- 摘要：An operator splitting method was developed to solve the incompressible Navier-Stokes equations defined in a rotating frame of reference. Based on the operator splitting, this method provides an efficient way to decouple the three main difficulties of the problem, the incompressibility, the nonlinearity and the numerical oscillations due to the presence of the dominated Coriolis forces. The sub-grid scale stabilized method was used to eliminate the oscillations caused by incompressibility and dominated Coriolis forces when Galerkin method was employed. Least-squares conjugate gradient algorithms were applied to solve for the nonlinear instability, which avoids the necessity of introducing the upwind scheme to discrete the convective term. Compared with other numerical methods, the present method ensures the resulting coefficient matrices to be positive definite and invariable, which can be efficiently stored and solved. Several numerical examples indicate that the method displays improved stability, fast convergence and high accuracy.关键词：Coriolis force;operator splitting;stabilized method;sub-grid scale;conjugate gradient algorithm3505|5|2更新时间：2025-12-08
- 摘要：Fuzzy theory is employed to establish the control systems based on the knowledge of object and controlling. Genetic algorithm is utilized to obtain the data o optimal combination mode of these two systems within different time interval to eliminate the subjectivity and uncertainty. Then the adaptive laws which adjust the free parameters of the fuzzy systems are developed with Lyapunov function, and the stability and convergence of the whole control system is proved. The proposed method is validated with the Duffing forced-oscillation system, and the simulation results illustrate that the proposed method enables every state variable to trace the object more quickly and accurately than the composed adaptive method.关键词：adaptive fuzzy control;fuzzy theory;genetic algorithm3065|5|0更新时间：2025-12-08
- 摘要：To solve the difficulties of the discretization and application of fractional order controllers(FOC), evaluation strategies of digital realization of FOC are investigated. The realization principle and process of various discretization methods are discussed. One position control system is introduced as the objective controlled by FOC. Based on Mittag-Leffler function, the fractional order control system with full memory length is adopted as evaluation criterion, and an approximation performance function of discretization methods is proposed. Analyzing the time domain error and approximation performance, the investigation to various discretization methods is carried out comparatively in detail. The result verifies that the discrete model with power series direct discretization method requires 100 memory length to obtain the better approximation, while one with continued fraction direct discretization method requires only 10 order. Thus the continued fraction direct discretization method is preferable to digital realization of fractional order control algorithms in engineering applications.关键词：分数阶控制器;离散方法;评估策略;分数阶微积分3044|5|10更新时间：2025-12-08
- 摘要：Ceramic coatings were fabricated on magnesium by micro-arc oxidation(MAO)under constant potential in NaAlO2 solution, and the effects of NaAlO2 concentration on the surface morphologies, phase composition and surface hardness of the MAO coatings were investigated. Corrosion resistance of the coatings in different NaAlO2 concentrations and the untreated magnesium were evaluated with the potentiodynamic polarization tester. The results show that with increasing NaAlO2 concentration the micro-pores of MAO coating decrease, while the average surface hardness increases. The MAO coating is mainly composed of MgO and MgAl2O4, and the content of MgAl2O4 increases with the increasing NaAlO2 concentration. With NaAlO2 concentration increasing, the corrosion potential of the MAO coating in 3.5% NaCl solution increases. MAO coating enables to effectively improve the corrosion resistance of magnesium.关键词：magnesium;micro-arc oxidation;corrosion resistance;microstructure2830|6|1更新时间：2025-12-08
- 摘要：A two-parameter earthquake damage model of multi-ribbed composite wall is presented based on the damage mechanics and the characteristics of multi-ribbed slab structure. Two modeling parameters are obtained by analyzing the dynamic response and hysteretic curves from the pseudo-dynamic experiment of multi-ribbed composite wall. The performance objective of three-level seismic design for multi-ribbed composite wall is classified in the light of the calculation of damage indices range to different damage levels. It is shown that the multi-ribbed composite wall has steady lateral capacity and good energy dissipation character when subjected to minor or medium earthquake and expected anti-collapse performance when exposed in great earthquake.关键词：multi-ribbed composite wall;pseudo-dynamic;earthquake damage model;damage index4397|5|4更新时间：2025-12-08
- 摘要：In order to apply the unified strength theory taking tension as positive to the rock and soil engineering customarily taking compression as positive, the experimental conditions of simple compression and simple tension tests are substituted in the expression of the unified strengththeory, and the relative parameters are determined, hence an expression of unified strength theory is derived for rock and soil materials, where compression is regarded as positive, and the difference of tension and compression strength of rock and soil materials and the effect of intermediate principal stress are taken into account. The presented unified strength theory is then introduced to establish an elasto-plastic softening constitutive model of triaxial state in strain space for a sort of diatom soft rock. A numerical simulation is carried out along with the test data of the diatom soft rock, and the result shows that the simulation of the unified elasto-plastic softening constitutive model coincides well with the test and describes the strain softening accurately.关键词：软岩;应变软化;本构模型;应变空间;统一强度理论2861|5|2更新时间：2025-12-08
- 摘要：A new apparatus was developed to investigate solubility characteristics of refrigerant-absorbent. It consists of a temperature measurement system(253.15 -363.15 K, temperature uncertainty less than ±14 mK), a pressure measurement system(0 - 3.5 MPa, pressure uncertainty less than ±1.6 kPa),a water thermostat bath(293.15 - 363.15 K),an alcohol thermostat bath(253.15 - 293.15 K),a vacuum system, and a mixture make-up system. In order to check the reliability and accuracy of the system, several test measurements were conducted on the vapor pressure of R134a and p-T diagram for the binary mixture of R22+DMF. The test results are in good agreement with the reference data.关键词：solubility;refrigerant;experimental system3044|6|1更新时间：2025-12-08
- 摘要：Choosing pure nickel foil as the transition layer, Al/0Cr18Ni9Ti bimetallic composite is prepared with the vacuum warm compaction diffusion method under the condition of 480 ℃ compaction temperature, 10 MPa pressure and 1.0×10-2 Pa vacuum. The structures and performances of the two bimetallic composite bonding interfaces and matrix are analyzed respectively with scanning electron microscope, X-ray diffractometer and Vickers microhardness scale. It is found that under the condition of diffusion bonding, three kinds of intermetallic compounds, Al3Ni2, Al3Ni and Al3Ni5, form in the Al/Ni interface less than 4 μm in thickness; and no intermetallic compound forms in the Ni/0Cr18Ni9Ti diffusion zone with about 8 μm in thickness.关键词：composite;intermetallic compound;interface;diffusion bonding2964|5|1更新时间：2025-12-08
- 摘要：The cross-flow induced vibration of a row of cylinders at sub-critical Reynolds number Re=2.67×104 is simulated based on surface vorticity method and a fluid-structure interaction model incorporating the effects of cylinder motions and displacements. The computational results of the vorticity map, fluid force, vibration response, and shedding frequency are presented. The non-uniform flow behind a rigid cylinder row with a small pitch ratio T/D=1.5 is characterized by narrow and wide near wakes and multiple frequencies, and the vortex shedding behind a rigid cylinder row with T/D=2.0 is replicated properly by the simulation results. Furthermore, the flow induced vibration of a flexible cylinder row with T/D=2.0 is also investigated. The numerical results show that the coupling between x- and y-direction occurs obviously for large-amplitude vibration, and declines rapidly with the reduced vibration amplitude to be expected to choose single DOF dynamic model for the flow-induced vibration of a cylinder row.关键词：surface vorticity method;cylinder array;flow induced vibration3232|5|0更新时间：2025-12-08
- 摘要：A Chebychev spectral elements approximation of the acoustic wave equation with first-order Clayton-Engquist-Majda absorbing boundary conditions was derived. Its discretization is based on spectral elements in space and central differences method in time. The numerical result, shows that this approximation has spectral accuracy in space and up to second-order in time. Compared with the same wave problems with conventional Dirichlet boundary conditions, the absorbing boundary conditions can reduce the numerical reflection on boundaries and avoid solution distortion. In addition, the central differences method is economic in memory requirement and computing time compared with implicit integral method.关键词：absorbing boundary condition;wave equation;spectral element;central difference method3199|5|3更新时间：2025-12-08
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