最新刊期
卷 43 ， 期 11 ， 2009
- 摘要：From the characteristics of waste heat in exhaust, cooling water and lubricant, a new thermodynamic cycle for waste heat recovery of vehicle engines was proposed. The present system consists of two cycles, organic Rankine cycle(ORC)for recovering the waste heat in high-temperature exhaust and lubricant and Kalina cycle for recovering the waste heat in low-temperature cooling water. Based on P-R equation of state, the thermodynamic performance of the cycle was theoretically calculated with a self-written computing program. Then the overall performance of the cycle with different organic working fluids was analyzed individually. Compared with the conventional cycle configuration used for only recovering the exhaust heat, the present cycle has higher waste heat recovery efficiency. The overall efficiency of the cycle with cyclopentane and R113 is 20.83% and 16.51%, respectively.关键词：vehicle engine;waste heat recovery;new thermodynamic cycle;thermodynamic performance3340|4|9更新时间：2025-07-09
- 摘要：An effective and simple way to reconstruct the lattice Boltzmann method(LBM)distribution functions by macro-scale parameters has been proposed on the basis of the mathematical multiscale-approach in this paper. The reconstruction operator offers a fundamental approach to multiscale computation in engineering application. The numerical computation on lid-driven cavity flow by the coupling between the results of LBM and the finite-volume method(FVM)is performed to verify the proposed reconstruction operator. The computation results are in agreement with the data in literature, and the smoothness of the streamlines in the coupled region is reasonable and the velocity vectors have an exact overlap. In addition, the results show that the present reconstruction operator can be adopted in the coupling computation of LBM and the macro-scale method easily and reliably.关键词：LBM;FVM;reconstruction operator;distribution functions;multiscale;coupling2835|4|4更新时间：2025-07-09
- 摘要：An adaptive unstructured grid generation algorithm, which adopts Cartesian grid to decompose a background domain and adopts a cut cell approach to express curvilinear boundaries, is presented for solving steady incompressible Navier-Stokes equations. By using quadtree data structure to store mesh data, simplifying cut types into six schemes, and employing the curl and divergence of velocity as criteria of grid refinement, this approach can implement mesh generation and adaptive refinement for arbitrary complex geometries automatically. A solution of N-S equations via finite volume method for this mesh is derived. The SIMPLE based smoothing pressure correction is chosen to suppress the checkerboard pressure oscillation due to collocated variables arrangement. The present method is applied to two benchmark problems and is verified to be accurate and efficient.关键词：quadtree;Cartesian grid;cut cell;grid adaptation3272|4|3更新时间：2025-07-09
- 摘要：A velocity-measurement equipment was developed to study the influence of fluid subcooling degree on the nozzle operation performance. The mass flow rate and the impact force were measured and the average mixing velocity of the two-phase fluid was obtained based on the momentum theorem. The influence of fluid subcooling degree on the average mixing velocity of the two-phase fluid at the outlet of LAVAL nozzles and the efficiencies of the nozzles was investigated on a refrigeration system with R410A. The experimental results show that the mass flow rate increased with the increase of the refrigerant subcooling degree at the inlet of the nozzles. However, the increase of upstream subcooling degree resulted in the significant decrease of the refrigerant mixing velocity and the nozzle efficiency. Under test conditions, the refrigerant mixing velocity at the outlet of the nozzle and the nozzle efficiency decreased by 35.7% and 33.9%, respectively, when the upstream subcooling degree increased from 0 ℃ to 11 ℃ for No.2 nozzle.关键词：refrigeration;nozzle;velocity;efficiency3333|4|1更新时间：2025-07-09
- 摘要：An alternating frequency/time domain method(AFT)is presented to calculate the dynamic characteristics of damping blade systems accurately. The dynamic response of damping blade systems is predicted based on the microslip dry friction model, and the computational accuracy and efficiency are compared with those by the time domain method and the frequency domain method. The results indicate of that under certain parameter conditions, the calculation time of AFT method is similar to that of the one-term harmonic balance method(HBM)and is just ten percent of that of the fourth-order Runge-Kutta method, and the relative error of the result with the AFT method is less than half that with HBM. These findings confirm the practicability of the AFT method in computing dynamic response of damping blade systems based on the microslip dry friction model. Unlike HBM, the AFT method can achieve the accuracy of microslip dry friction model in dynamics analysis and has high computational efficiency.关键词：blade;vibration;dry friction damping;microslip model;alternating frequency/time domain method.4158|4|2更新时间：2025-07-09
- 摘要：To study the influences of the exhaust gas recirculation(EGR)rate on the emissions and performance of dimethyl ether(DME)engines, an experimental investigation was conducted on a 2-cylinder DME engine with EGR. Under the various operating conditions, the fuel consumption and emissions of HC, CO, and NOx were measured. The results show that the maximum EGR rate of the DME engine can reach 60% approximately, however, under high load conditions, too large EGR rate will result in obvious deterioration in the engine brake specific fuel consumption. EGR has significant effects on NOx emissions. NOx emissions decrease clearly with the increase in the EGR rate, especially under high load conditions. HC and CO emissions increase with the increase in the EGR rate, particularly under high load conditions. When the EGR rate is over a certain value, the increase of the EGR rate will lead to a quick increase in HC and CO emissions. It is suggested that the optimal EGR rate should be near 30% under low load conditions while the engine should run with low EGR rates under high load conditions.关键词：dimethyl ether engine;exhaust gas recirculation;performance;emission characteristics3208|4|1更新时间：2025-07-09
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Aerodynamic Optimization Design of Vaned Diffuser for Centrifugal Compressor under Stage Environment
摘要：The vaned diffuser profile designed preliminarily has been optimized using artificial neural network and genetic algorithm under stage environment to improve the aerodynamic performance at the design operation condition. The aerodynamic performance of the stage composed of the vaned diffuser optimized and the original impeller at the design and off-design operation conditions is predicted using the numerical method. The results show that the static pressure recovery coefficient of the vaned diffuser and the isentropic efficiency of the stage was increased by 11.7% and 1.64%, respectively. The total pressure loss coefficient of the vaned diffuser was decreased by 21.12%, and the isentropic efficiency of the stage was 86.1% at the design operation condition. Moreover, the aerodynamic performances of the stage at the off-design operation conditions was improved significantly. In addition, the surge margin of the stage was increased, and the choke margin was decreased slightly.关键词：centrifugal compressor;vaned diffuser;aerodynamic optimization;artificial neural network;genetic algorithm3190|4|2更新时间：2025-07-09 - 摘要：A quasi-steady state simulation was conducted on the cooling process of a freeze-dryer with an auto-cascade refrigerating system using a rectification column. It is found that, unlike the system with a pure refrigerant, a peak value of the volumetric refrigerating capacity occurs as the cycle pressure level varies at a specified mixture composition and a pressure ratio. Optimization of the cycle refrigerating capacity was also performed at the different mixture compositions and the influence of the mixture composition on the cycle refrigerating capacity at different temperature levels in the cooling process was analyzed. The two new concepts, total unit cooling time and unit cooling time, were applied for the detailed analysis on a special case in which the heat capacity of a freeze-drying sample was much smaller than that of the shelf evaporator. An experimental freeze-dryer with an auto-cascade refrigerating system using a rectification column was designed and it operated steadily from -60 ℃ to -80 ℃. The simulation results are in consistency with the experimental data.关键词：mixed refrigerant;rectification;auto-cascade;freeze-dryer;optimization3056|4|4更新时间：2025-07-09
- 摘要：Spinnable mullite precursor sols were prepared by sol-gel process from an aqueous solution of aluminum nitrate, aluminum isopropoxide and tetraethylorthosilicate. A 4:1 molar ratio of aluminum isopropoxide and aluminum nitrate was optimized to obtain spinnable precursor sols for fibres synthesis. The mullite fiber was obtained with smooth surface and uniform diameter after calcination at 1 200 ℃ for one hour. The active energy of mullite crystallization is 993.5 kJ/mol and 1 014.2 kJ/mol by the calculation of Kissinger equation and Ligero equation, respectively.关键词：mullite;sol-gel process;fibre;active energy532290|8|6更新时间：2025-07-09
- 摘要：Dielectric elastomer(DE), a kind of electronic electroactive polymer(EAP), was made as a circular actuator and investigated for displacement response of the different voltage waveform, amplitude and frequency as driven by AC voltage and pulsating DC voltage. The influences that the above factors bring to electroactive displacement of DE actuator were investigated through experiments. The experimental results lead to the following conclusions. The displacement differs with different wave of voltage, which decreases driven by square, sine and triangular wave of voltage respectively with other conditions remained while the reduction speed increases with the increasing frequency. The displacement increases with the increasing amplitude of voltage and decreases with the increasing frequency of voltage. The relation between displacement and amplitude as well as frequency of drive voltage gets nonlinear. The drive process is more stable driven by pulsating DC voltage than that driven by AC voltage. Comparing the experimental results of DE actuators with 2×2,3×3 and 4×4 pre-strain, the conclusion shows that the electric field strength for DE actuator with 4×4 pre-strain is higher than that for the DE actuator with 2×2 and 3×3 pre-strain. The DE actuator with 4×4 pre-strain is more desirable the actuator with 2×2 and 3×3 pre-strain for the deformation stability, response speed and frequency of voltage that the DE actuator can endure.关键词：electroactive polymer;dielectric elastomer;actuator;displacement response2906|4|5更新时间：2025-07-09
- 摘要：An experimental water heater system using a transcritical CO2 heat pump with an ejector was designed, and a measurement and control system was developed. Experiments were conducted to assess the effects of cooling water flow rate and inlet temperature on the system performance. The changes of the heating coefficient of performance(Cr), heating capacity, pressure ratio, entrainment ratio, pressure lift were and ejector efficiency were analyzed. The experimental results show that the entrainment ratio and the pressure lift were increased while the ejector efficiency was decreased with the decrease in the cooling water flow rate or the increase in the inlet temperature. Under the experimental working conditions, the ejector efficiency was up to 34%, and the pressure lift was up to 1.165. The Cr reached about 3.0 when the evaporation temperature was -5 ℃. Compared with that of a conventional system with an expansion valve, the pressure ratio of the compressor in the present water heater system is decreased by 12%-14%. It appears that the ejector can improve the system performance of transcritical CO2 heat pump water heaters effectively.关键词：ejector;CO2;transcritical cycle;ejector efficiency3099|4|11更新时间：2025-07-09
- 摘要：A dynamic job scheduling method is proposed, where radio frequency identification technology is adopted to collect the real-time production information related to workpieces, operations and facilities produced at the manufacturing spots; on the basis, to deal with the three types of uncertain events including new jobs arrival, facility breakdown and delivery-time change occurred in the manufacturing cell production, taking the shortest finishing time of jobs as the scheduling objective, a dynamic job scheduling mathematical model is established and solved with hybrid genetic algorithm designed by introducing hill-climbing searching method. Four evolution operators consisting of selection, crossover, mutation and hill-climbing are designed to effectively improve the convergence speed of the algorithm. A prototype system of dynamic job scheduling based on real-time production information is developed. The job scheduling case study is carried out and the results show that the proposed job scheduling method enables to deal with the dynamic job scheduling problems for uncertain events efficiently to improve the consistency between scheduling solutions and practical requirements of manufacturing cell production.关键词：job scheduling;radio frequency identification;uncertain events;hybrid genetic algorithm3334|4|1更新时间：2025-07-09
- 摘要：To improve the adaptability and effectiveness of recognition on abnormal condition, a self-adaptive alarm method for equipment condition based on one-class support vector machine(OC-SVM)is proposed. The optimum distribution area of monitoring parameters in high-dimensional feature space is dynamically estimated with on-line algorithm of OC-SVM. The abnormal index, determined by the relative distance between the new data and the distribution area at the previous moment, describes the statistical feature variation of monitoring parameters and identifies the abnormal condition of the equipments. The characteristics, such as the sensitivity in abnormal condition recognition, the toleration in slow deterioration and the adaptability in condition alternation, are verified by simulation data. The present method is further applied to the vibration monitoring of heating furnace fan. The alarms under the actual abnormal condition meet the demand of equipment monitoring.关键词：one-class support vector machine;self-adaptive alarm;abnormal condition3151|4|5更新时间：2025-07-09
- 摘要：The computational fluid dynamics(CFD)technique combined with the acoustic analogy theory is employed to study the blade passing frequency(BPF)noise caused by the volute casing surface dipole and the blade rotating dipole in a centrifugal fan. A 3D unsteady turbulent internal flow is obtained by CFD at three different flow rates. The volute surface dipole is extracted based on the FW-H equation and the blade noise is modeled by the Lowson's formula. The multi-domain direct boundary element method is applied to study the noise propagation including the interior acoustic problem and the exterior acoustic problem, and these two models established are coupled together at the casing inlet and outlet openings. It is considered that the interior noise will spread outside through the casing openings by the sound scattering effect of the casing. The results show that the pressure fluctuation on the casing surface had the clear BPF component while there was no obvious BPF fluctuation on the blade. The volute tongue was the main contributor to the BPF fan noise. In addition, the casing noise strength was increased dramatically with the flow rate and the BPF blade noise was smaller than the casing noise, especially at large flow rates.关键词：centrifugal fan;blade passing frequency;noise;dipole source3417|4|8更新时间：2025-07-09
- 摘要：The weakening, enhancement and fracture mode of the interface between ceramic particulate reinforcement and metal(P/M)in transient liquid phase(TLP)bonded joint of aluminum matrix composite are investigated to optimize the design of alloying system of interlayer. From the fracture surface of the TLP bonded joint of Al2O3p/Al using pure copper foil, it can be seen that the Al2O3 particulates exhibit smooth surface without adhesives or disruption, and some areas of metal on fracture surface also appear smooth. The results indicate that the P/M interface bonding gets weak showing interfacial debonding fracture mode. A novel process of active-transient liquid phase(A-TLP)bonding with an interlayer containing both melting point depressant(MPD)and active alloying element is hence proposed to improve the interfacial wettability between weak P/M interface. When the Ti content is lower, a large amount of discontinuous adhesives with small size are present on the Al2O3 particulate surfaces in the A-TLP bonded joint as a result of reaction, while the P/M interfacial bonding becomes so strong that many Al2O3 particulates are disrupted during shear test in the case of higher Ti content.关键词：metal matrix composite;transient liquid phase bonding;active alloying element;interfacial reaction;fracture mode3363|4|2更新时间：2025-07-09
- 摘要：Aiming at the demerit of the gradient projection method and numerical optimization methods as performing additional work at displacement level, a novel two-step strategy of motion planning for redundant manipulators from the perspective of self-motion manifold is proposed, where a precise posture tracking of the end-effector is carried out by employing non-redundant joint, then the redundant joint is adjusted with the gradient of additional work on redundant joint displacement, and the additional work is performed via the self-motion of manipulator. The simulation result shows that this method can remarkably accelerate the solution process while performing the main task and additional task in a more efficient manner to suit the case of the additional work at the displacement level for redundant manipulator.关键词：redundant manipulators;self-motion;motion planning2976|4|1更新时间：2025-07-09
- 摘要：The function of environment effecting creature evolution, the process of immune clone algorithm and some operators of genetic algorithm are considered synthetically. An environment-based synergic immune genetic algorithm(ESIGA)is presented to improve the searching rate and global searching ability of optimal algorithm. The clone-environment operator and self adaptive search operator are designed to make the algorithm possess learning capability to accelerate the searching rate and avoid prematurity. And three groups of sub-population are used for improving the global searching ability, where the interaction between main sub-population and synergic sub-population improves the environment and exerts clone-environment operator effect, and the elitist sub-population enhances the neighborhood searching. Then 13 classical benchmarks of non-constraint optimal problem are executed by the proposed algorithm. The test results demonstrate that ESIGA searching rate is twice as QGA/Q. ESIGA is suit to deal with 1 000-dimension non-constraint optimal problems.关键词：environment;immune;genetic algorithm;synergy3021|4|3更新时间：2025-07-09
- 摘要：Phase unwrapping methods are discussed for water fat separation in magnetic resonance imaging(MRI). Weighted multi-grid algorithm is applied to solve the discrete partial differential equation of phase array. A new weight method is propased, which is composed from maximum gradient array and phase differential coefficient array.The residues and discontinuous points are labeled by this composed weight array, where the error propagation the process of can be restrained by residues and noises during solving the discrete partial differential equation. By means of the weighted least squares solutions for partial differential equations,the phase unwrapping starts from the high-quality regions and avoids the low-quality regions effectively to improve the reliability. The simulation data and experiments for brain scan on 0.3 T low field MRI system show the validity.关键词：magnetic resonance imaging;water fat separation;phase unwrapping3274|4|1更新时间：2025-07-09
- 摘要：A UV-based nano imprint lithography(NIL)method is developed to fabricate thin film with controlled TiO2 nanocrystal island array on the transparent conductive glass substrate for dye sensitive solar cells(DSSC). The UV curable TiO2 sol is prepared to form TiO2 thin film with 3 μm critical dimension TiO2 nanocrystal island array by mixing TiO2 powder, dispersant, emulsifier, alcohol and UV-curable resin. Ultimately, TiO2 thin film with orderly island array is fabricated by the pressure holding replica optimized technique. The thin film is further heated up to 600 ℃ to wipe off the adulterant like UV-curable resist and cooled down to 450 ℃, then the TiO2 nanocrystal island on the thin film is changed to the anatase TiO2. The experimental results show that DSSC equipped with TiO2 nanocrystal island array is endowed with conversion efficiency over 2.7% under AM 1.5 illumination(0.1 W/cm2), which infers that the NIL method can be employed to fabricate highly stable DSSC with quasi-solid-state or solid state electrolyte.关键词：nano imprint lithography;nanocrystal island;photo anode;solar cell3542|4|0更新时间：2025-07-09
- 摘要：To acquire the impact component aroused by mechanical fault, a new feature extraction method based on manifold learning is proposed. After embedding the raw vibration signal into a high dimensional phase space to reconstruct a dynamical manifold, the local target space alignment algorithm is employed for extracting nonlinear low dimensional manifold. According to the characteristics of the kurtosis index and skewness index, the adaptive selection criterion of local neighborhood parameters in phase space is introduced to reflect the optimal impacts. The experimental results and industrial measurements show that this approach, compared with the soft-threshold method, is more effective to extract the weak periodic impacts from mechanical signals.关键词：manifold learning;feature extraction;impact response3450|4|8更新时间：2025-07-09
- 摘要：A small power generator test system with low-temperature waste heat was built using R123 as working fluid and a scroll expander as a power recovery machine on the basis of the theory of organic Rankine cycle. The influence of the rotating speed of the scroll expander on the system performance was analyzed at the same inlet temperature and mass flow rate of heat source, and the two different mass flow rates of working fluid. The results show that the suction pressure and the suction temperature of the scroll expander decreased but the discharge pressure and the discharge temperature increased with the increase in the rotating speed. The power generated and the total efficiency decreased while the volumetric efficiency of the scroll expander increased with the increase in the rotating speed. Under the two test conditions, the maximum power generated was 0.66 kW and 0.62 kW, respectively; both the maximum total efficiencies were 2.1%; the range of volumetric efficiency was 38.5%-56.5% and 39.7%-60.0%, respectively.关键词：low-temperature waste heat;organic Rankine cycle;scroll expander2966|4|10更新时间：2025-07-09
- 摘要：To ensure cavern tightness and safety, the models of heat transfer between oil, brine and surrounding rock, thermal pressurization rate, halite creep, and seepage were established and TDMA algorithm was adopted to solve them. The results suggest that the temperature and the pressure will increase by 8.635 ℃ and 8.97 MPa in seven years storage process, respectively, i.e., an approximate value of 1 MPa/℃. The creep rate will decrease with the increase in storage time, and the penetration could be neglected due to little penetrability. In addition, temperature will have significant influence on the cavern pressure and the influence will be determined by the ratio between the thermal expansion coefficient and the compressibility factor(α/β)of both oil and brine. It appears that the thermal expansion coefficient and the compressibility factor of both oil and brine should be measured precisely so that the liquid temperature and pressure in caverns can be predicted accurately.关键词：cavern oil storage;underground oil storage;heat exchange;creep;permeation3243|4|10更新时间：2025-07-09
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Bubble Packing Method Based Unstructured Grid Generation of Curved-Edge Polygon with Its Application
摘要：An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is mapped into a straight line to allow bubble adding and moving. Then the bubble position is mapped into the curve boundary by the arc-length parameterization method. Combined with conventional methods, a new method to judge a point in a given curved-edge polygon is proposed. Local grid refinement is realized by adding different size bubbles to the real and artificial vertices and setting the bubble's radius by the weighted average method. Moreover, the SIMPLE algorithm on unstructured collocated grid systems is developed and applied to simulate the lid-driven flow in a polar cavity. The numerical simulation results agree well with the experimental data under different Reynolds numbers.关键词：bubble packing method;unstructured grid;curved-edge polygon;numerical simulation3254|4|1更新时间：2025-07-09 - 摘要：PM10 samples were collected in Xi'an from 19 Dec 2006 to 15 Jan 2007 and the polycyclic aromatic hydrocarbons(PAHs)concentration was measured using a gas chromatography-mass spectrometric(GC-MS). The total PAHs concentration ranged 174.6-455.0 ng·m-3 in the daytime and 193.9-515.4 ng·m-3 in the night. PAHs profiles were predominated by high rings components with 4-5 rings. The carcinogenic power of atmospheric PM10 PAHs was evaluated using benzo(a)pyrene(BaP)and benzo(a)pyrene-equivalent carcinogenic concentration(BaPE). The results show that the average concentration of BaP was 30.0 ng·m-3 in the daytime and 34.8 ng·m-3 in the night. The average concentration of BaPE was 45.3 ng·m-3 in the daytime and 51.0 ng·m-3 in the night. The concentration of BaP observed in Xi'an was 4.5 times greater than that in Chinese standard of environment air quality. PAHs sources were identified using source profiles of previous studies and it is likely that diesel vehicle exhaust and coal combustion are the main sources of PM10 PAHs in Xi'an during winter.关键词：PM10;PAHs;BaPE;assessment3491|5|9更新时间：2025-07-09
- 摘要：A soluble polymer was synthesized by chemical oxidative polymerization based on N-vinylpyrrole. The structure of the resulting polymer was characterized by FT-IR and 1H-NMR. The results revealed that the polymer was comprised by polypyrrole and poly ethylene. The investigation to the polymer morphologies by scanning electron microscopy(SEM)showed that the film formed by casting from organic solutions was uniform and smooth. The photoluminescence spectra of the polymer in organic solutions were also analyzed. At 430 nm excitation, the polymer in THF solution exhibited a strong green-emission band at around 520 nm. The emission peak in THF solution exhibited red-shift with the increasing concentration of the solution, while the relationship of polymer intensity and concentration was nonlinear. The polymer intensity reached a maximum value at a mass fraction of 0.03% of the solution.关键词：polypyrrole;photoluminescence;synthesis2896|4|2更新时间：2025-07-09
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