最新刊期
卷 54 ， 期 4 ， 2020
- 摘要：A time-dependent reliability evaluation method is proposed to predict the failure life of harmonic drive precisely. Considering the dynamic contact interference, a transient dynamic finite element model of harmonic drive is established to solve dynamic stress at the critical position of flexspline in harmonic drive. The accelerated life tests of harmonic drive are conducted, and degradation parameters are identified by failure life samples via maximum likelihood estimation. Combined with residual strength model, stochastic perturbation method and Edgeworth series, the time-dependent reliability evaluation method of harmonic drive is proposed. Taking the XB-60 harmonic drive as a case study, both finite element analysis and failure life samples show that the critical position of stress concentration is at the tooth root of rear section of gear ring in flexspline. Compared with the time-dependent reliability methods with equivalent circular-shell static stress or empirical degradation pa676|6|9更新时间：2025-07-09
- 摘要：An efficient online control method of the electromagnetic damper damping coefficient is proposed to deal with the problem that the damping adjustment of damper in suspension of present new energy vehicle is complicated and energy consuming, and the vibration energy is recovered at the same time. The method uses an electromagnetic damper that consists of a DC motor and a ball screw mechanism. First, a damping adjustment circuit based on a high-frequency DC-DC converter is designed. Its output voltage is adjusted based on input voltage by adjusting the duty cycle of the PWM signal that drives the power MOSFET. Then the target electromagnetic torque is calculated during the working process of the damper, and the armature current required to reach the reference torque is calculated. On the other hand, the actual armature current is continuously collected during the working process, and the current is sent to a PI controller for PI closed-loop adjustment to output the duty cycle of the driv关键词：new energy vehicle;electromagnetic suspension damper;online control;vibration energy recovery339|5|7更新时间：2025-07-09
- 摘要：A multiple-action radial piston pump scheme with a revolving outer ring featuring low speed and high volumetric efficiency is proposed to solve the problem of rotating speeds mismatch between the seawater hydraulic pump and the hydro-turbine in the reverse osmosis desalination system driven by tidal current energy. The pump is composed of a moving shell, a cylinder, a distributing valve, a plunger component, a liquid spring, a pipeline shaft, and a pressure regulator, etc. When the pump is working, the tidal current energy hydro-turbine drives the shell directly and the multi-row misaligned axisymmetric plunger component is closely attached to the inner wall of the shell under the action of the liquid spring, moves reciprocally along the multi-action curve of the inner wall relative to the cylinder hole, and completes seawater suction and compression through the distribution valve. The pump reali-es multiple actions within single rotation to raise the frequency and velocity of the pist244|4|1更新时间：2025-07-09
- 摘要：A test rig based on falling film on the vertical aluminium plate is designed and built to obtain the film thickness characteristics under high Reynolds number(Re>700)on the plate and the wetting properties with overflow type distributor. The instantaneous film thickness of cold water without heating is measured by the capacitance probe technology under Re ranging from 660 to 1 390. Effects of flow length and Re on the average film thickness are emphatically analy-ed by comparing with literature data. The wetted area in wetting process is measured by the image processing technology. Experimental results show that the maximum value, minimum value, mean value, standard deviation and fluctuation amplitude of liquid film thickness all show an upward trend with the increase of Re within the studied Re conditions. The thickness of liquid film varies greatly at different flow lengths. An empirical correlation of average liquid film thickness at flow length 0.43 m is obtained by fitting, and关键词：falling film;vertical plate;film thickness;wetting;overflow;distributor222|4|2更新时间：2025-07-09
- 摘要：A detailed reaction mechanism model involving 34 species and 115 elementary reactions is developed to reveal the reaction mechanism of H2S formation during coal combustion from the level of free radical. Furthermore, numerical simulation and experimental methods are applied to verify the credibility of the model and to analy-e the rate-of-production(ROP)of main sulfur species and important free radicals, and the sensitivity of H2S formation. A comparison between the experimental and the predicated results shows that the errors of CO2, CO, H2, H2S, SO2 and COS are all within 5%, and that the maximum error of CS2 is 25%. Therefore, the model has a high reliability. Rate-of-production(ROP)analysis indicates that H2S is mainly generated via elementary reactions ofH2S+H-SH+H2,CS2+H2O-H2S+COS, andCOS+H2O-H2S+CO2.SO<关键词：detailed mechanism;H2S formation;pulveri-ed coal combustion;high-temperature248|4|3更新时间：2025-07-09
- 摘要：A direct torque control method with a new -ero vector for two-three conduction brushless DC motors is proposed to solve the problem of large torque ripple amplitude in brushless DC motors. The method uses an alternate conduction driving mode of two-phase and three-phase and a direct torque control method to form 12 sectors, and defines a new type of -ero vector to improve the space voltage vector selection table and to reduce torque pulsation amplitude. MATLAB simulation results and a comparison with the system using traditional -ero vector show that the proposed system using the new -ero vector reduces the torque ripple amplitude by about 40.94% when the motor is running without load at a rated speed of 2 000 r/min; when the motor is running with a 4.3 N-m load at a low speed of 500 r/min, the proposed method reduces the torque ripple amplitude by about 47.40%; and when the motor is running with a 4.3 N-m load at a rated high speed of 2 000 r/min, the proposed method reduces the tor关键词：new -ero vector;two-three conduction;direct torque control;brushless DC motor214|4|2更新时间：2025-07-09
- 摘要：To optimi-e the performance of the parallel-connected double-effect mechanical vapor recompression(MVR)evaporation crystalli-ation system while meeting production requirements, a method for optimi-ation design of the system based on the strength Pareto evolution algorithm(SPEA2)was proposed to further exploit the energy saving potential of the system. A mathematical model of the optimi-ation problem was established by analy-ing the effects of the operating variables on the system performance, and the constraints of mass and energy balances of the model were also imposed. The mathematical model was calculated by SPEA2 multi-objective evolutionary algorithm, where the minimi-ation of total power consumption and heat transfer area was taken as the optimi-ation object, and the optimal combination of evaporation temperature and compression temperature rise was obtained following the fu--y set theory. The results show that the total power consumption of the system is lowered by 22.1 kW and t223|4|3更新时间：2025-07-09
- 摘要：A defogging algorithm for dense fog images based on low-rank and dictionary expression decomposition is proposed to improve the problem that the existing image defogging algorithm is not ideal for image defogging of ha-e scene. Based on the atmospheric scattering physical model and the global low-rank characteristics of -fog- in the ha-e scene image, the degraded image is assumed as a composition of a low-rank -fog- image and an original clear image. Then the -fog- image is expressed as a product of a dictionary matrix and a sparse matrix, so that the -fog- image can be decomposed through the low-rank and dictionary expression decomposition model. The decomposed local -fog- image is extended to a global level by combining the bicubic interpolation. The clear image is finally recovered by subtracting the -fog- image. Experimental results and comparisons with existing mainstream image defogging algorithms on 194 real dense fog images show that the proposed algorithm has bette376|5|5更新时间：2025-07-09
- 摘要：In order to reali-e automatic reasoning with the original relations of rectangular cardinal direction relations between regions and then to improve model-s power of intelligent reasoning and prediction for direction relations, corresponding inference rules are given and their correctness is proved. An algorithm is proposed to automatically compute the original relations of the rectangular cardinal direction relations defined by a direction relation matrix and to reali-e automatic reasoning and calculation of the original relationship of the cardinal direction of the two-dimensional rectangle under the direction relation matrix model. The algorithm searches and prunes the solution space with the help of a queue. Theoretical analysis and experimental results show that the algorithm is correct and complete. This algorithm effectively solves the problem of automatic reasoning with the original relations of the rectangular cardinal direction relations, avoids the complicated manual reasoni关键词：rectangular cardinal direction relation;original relation;direction relation matrix;automatic reasoning;spatial database225|4|3更新时间：2025-07-09
- 摘要：The osmotic destruction characteristics of tailings sand with a fine particle content of 30% are tested on a self-made small-scale permeation deformer. The evolution features of meso-structure pores and particle distribution in the process of osmotic destruction of the fine-grained tailings are discussed. In the process of osmotic destruction, the sample is loaded with 4 stages of water heads step by step by the method of water head difference until the sample is destroyed. Adopting CT(computeri-ed tomography)technology, the tailing sand samples under four head pressures are scanned, the vg studio max 3.0 and 3D avi-o 9.0.1 visuali-ation softwares are used to reconstruct the scanned sample data in three dimensions, and the distribution of particles and the mesoscopic changes of pore structure are investigated microscopically with the newly established digital image information after tailings sand osmotic failure. The microscopic process of osmotic destruction and the meso-structural fe关键词：CT scanning;fine-grained tailings sand;osmotic destruction;meso-structure198|4|3更新时间：2025-07-09
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A Study on Flow Characteristics of Pressure-Controlled Propellant Crossfeed in Liquid Rocket Systems
摘要：A numerical model is developed to study the dynamic characteristics of the propellant cross-feeding process. The model is based on the software AMEsim and adopts the modulari-ation idea to model the pressuri-ation, storage tank, pipeline feeding system and other functional modules. The crossfeed model is validated by experimental data, and consistency between the calculated and measured data is found. Then, the flow characteristics and the corresponding influencing factors during the pressure-controlled crossfeed process are analy-ed. The results show that there is a critical pressure to guarantee the full tank of core stage after booster separation, and the critical value is dependent on the initial propellant amount, the flight overload, and the volume flow rate. The initial refueling amount of the boost stage has no significant influence on the water hammer pressure under the critical pressure. However, an increase in the volume flow rate leads to an increase of water hammer pressur关键词：crossfeed;pressure control;critical pressure;liquid rocket226|4|3更新时间：2025-07-09 - 摘要：To expand the influence range of flow control technology and further improve the performance of rotor, a combined casing structure with axial skewed slots and suction slots is presented, and the influences of the combination of two flow control technologies on the flow field characteristics and performance of the transonic compressor are investigated numerically by steady state simulation. The results show that the stall margin is increased by 5.52% while the peak efficiency reduces by 2.5%, which indicates the significantly improved performance of the rotor. In addition, the flows at both blade tip and end wall are ameliorated; the combined effect of the two structures weakens shock wave intensity and fluid separation, and reduces the area of low velocity region. Although the interaction between the two structures can provide energy for the low-energy fluid, the mixing of the jet flow and the mainstream flow causes a certain mixing loss and increases the tangential momentum and second关键词：transonic compressor;axial skewed slot;end-wall suction slot;combined casing treatment195|4|0更新时间：2025-07-09
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