最新刊期
卷 51 ， 期 7 ， 2017
- 摘要：To evaluate the influence of rotating annular seal with eccentric rotor on the operation efficiency and stability of turbomachinery, a novel 3D mesh generation method and a numerical approach were adopted to solve the static gas response forces and static stiffness coefficients for the rotating annular seal at high rotor eccentricity ratios based on the mesh deformation technique and steady RANS solutions. An investigation on the leakage and static destabilizing characteristics of rotating annular seal at high rotor eccentricity ratios was conducted. The leakage flow rate, static gas response(exciting)forces, static stiffness coefficients and flow field characteristics of a fully-partitioned pocket damper seal(FPDS)were computed at three pressure ratios(0.17, 0.35, 0.50), two inlet preswirl ratios(0, 0.5)and seven eccentricity ratios(0.0,0.1,0.3,0.5,0.7,0.8,0.9). The results showed that the leakage flow rate increases with the eccentricity ratio. The rotor eccentricity and inlet preswirl result in a significant destabilizing cross-coupling stiffness, which may give rise to a risk of rotor whirling instability. The FPDS has a positive static direct stiffness as long as it operates at subsonic exit flow conditions, no matter the eccentricity ratio is high or low. For the choked exit condition, the FPDS shows negative static direct stiffness at low eccentricity ratios and then crosses over to positive value at the crossover eccentricity ratio 0.5, following a trend indicative of a parabola. The negative static direct stiffness may result in a full rotor eccentricity and rapid wear of seal due to rubbing contact.关键词：rotating seal;high eccentricity ratio;leakage characteristics;static dynamic characteristics;numerical simulation1079|5|11更新时间：2025-07-09
- 摘要：To conduct in-depth study on the performance of tank pressure control and the ability of heat leakage removing, an experimental rig was built to research the performance of thermodynamic vent system(TVS)with the simulant fluid of R123. The experimental research under three operation modes of tank pressurization, mixing injection depressurization and throttling refrigeration were conducted at the heat load of 800 W and the initial liquid height of 0.595 m. The tank pressure variation and fluid temperature change were analyzed during different operation modes. The results showed that, subjected to the external heat leak, the tank pressure rising rate was about 60.583 kPa/h during the tank pressurization phase; while in the mixing injection phase, increasing the circulation volume flow was beneficial to the reduction of vapor temperature. With the circulation volume flow of 150 L/h and the throttling rate of 11.73%～13.33%, the total venting gas was 20.536 kg for 8 throttling operation cycles. The maximum refrigeration capacity of one throttling operation cycle was 1 362 W. Compared with the direct venting gas approach, TVS has saved 41% exhaust loss for 2 hours' operation. The valuable conclusion could provide a technical reference for a further experiment on the cryogenic fluid thermodynamic vent system.关键词：thermodynamic vent;experimental research;pressure control;venting gas loss925|5|4更新时间：2025-07-09
- 摘要：In order to obtain the film cooling characteristics of odd-shaped film holes with large inclination angle under high mainstream turbulence intensity, three film hole configurations with an inclination angle of 60°, including cylindrical hole, water-drop hole and curved dustpan hole, were studied under the mainstream turbulence intensity of 11.82% using transient liquid crystal measurement technique. At a blowing ratio of 0.5, the film attachment behavior on the wall is good for all the three hole configurations, and the film cooling efficiency in upstream region is higher than that in downstream region. At a blowing ratio of 1.0, the film jets lift off from the wall for the cylindrical hole and water-drop hole, resulting in lower film cooling efficiency in upstream region. With further increase of blowing ratio, the film jets of the curved dustpan hole also lift off from the wall. The increase of blowing ratio will obviously enhance the heat transfer intensity for all the three hole configurations. The heat transfer coefficient ratio of the cylindrical hole and water-drop hole decreases gradually along the streamwise direction. And the heat transfer coefficient ratio of the curved dustpan hole is lower than that of the cylindrical hole and water-drop hole under all blowing ratios, and has an undulation feature at large blowing ratios. The above results indicate that the film cooling performance of the curved dustpan hole is better than that of the cylindrical hole and water-drop hole under all blowing ratios, but the film cooling performance of the cylindrical hole and water-drop hole with large inclination angles is close to each other.关键词：film cooling;shaped film holes;high mainstream turbulence intensity;cooling effectiveness;heat transfer coefficient ratio786|5|4更新时间：2025-07-09
- 摘要：A coupled time-space model is established in a polar coordinate to obtain the propagation characters from some monopole sources distributed evenly on a rigid cylinder. Following the least-squares variational principle, Chebyshev spectral element method is chosen to discretize both the time and space domains and the problem in polar coordinate is transformed into cylindrical coordinate. The validity of this model is verified by the numerical experiment, and the acoustic wave propagation on a rigid cylinder with C-E-M absorbing boundary condition on the edge of computational domain is revealed. The results show that a high-order accuracy can be obtained by the coupled time-space model via matching the numerical accuracy between time and space. The numerical accuracy can be improved by increasing the number of the elements or the interpolation order in each element of time and space. An exponential accuracy rate can be obtained with the increasing interpolation order. The acoustic wave propagation on the surface of a rigid cylinder can be simulated stably by this model, and the C-E-M absorbing boundary condition rewritten as the Dirichlet boundary condition still works well.关键词：time-space coupled;Least-Squares variation;polar coordinate;spectral element method;absorbing boundary686|6|0更新时间：2025-07-09
- 摘要：Four cooling structures, i.e., impingement cooling, traditional vortex cooling, middle-double vortex cooling and tangential-double vortex cooling, were constructed to investigate the influences on blade cooling behavior. The software ANSYS CFX was chosen to comparatively analyze the flow and heat transfer performance in the above structures. The results indicate that in the impingement cooling structure, air velocity changes obviously and pressure on target gets higher with the lowest friction coefficient, high local heat transfer intensity and low average heat transfer coefficient; in the traditional vortex cooling structure, air velocity changes slightly with large friction coefficient, large average heat transfer coefficient and better heat transfer distribution; in the middle-double vortex cooling structure, the highest average heat transfer coefficient and low friction coefficient show the potential application foreground as a new cooling structure for blade leading edge. It is unnecessary to further study the tangential-double vortex cooling structure due to its worse heat transfer performance.关键词：impingement cooling;vortex cooling;double vortex cooling;flow and heat transfer693|7|6更新时间：2025-07-09
- 摘要：Aerodynamic, heat transfer and film cooling performance on the squealer tip with pressure side winglet are numerically investigated. For three different cooling-hole arrangements, i. e. no film cooling hole, single hole-array located at the tip camber line, and two hole-arrays located at the tip camber line and pressure-side winglet, the flow structures, heat transfer and film cooling performance in the pressure-side winglet tip region are obtained. The predicted film cooling and heat transfer performance of the pressure-side winglet tip are also compared with the conventional squealer tip and squealer tip without pressure side rim configurations. The results show that compared with the other two tip configurations, the squealer tip with pressure side winglet is endowed with the superior performance of aerodynamic, heat transfer and film cooling effect in the blade tip region. The total pressure loss in the squealer tip with pressure side winglet gets close to that in squealer tip without pressure side rim, and is about 10% lower than that in the conventional squealer tip. For different cooling-hole arrangements, the average heat transfer coefficient on the squealer tip with pressure side winglet is the lowest, while the averaged film cooling effectiveness of this kind of tip is the highest when the film cooling holes are introduced. For the squealer tip with pressure side winglet, the influence region of coolant is affected by the distribution of the film cooling holes. Coolant from the camber-line cooling holes can effectively cool the cavity floor near the suction side, while coolant from the cooling holes in pressure-side winglet effectively cools the winglet surface and cavity floor near the pressure side.关键词：winglet;squealer tip;heat transfer;film cooling;total pressure loss749|6|7更新时间：2025-07-09
- 摘要：Flow characteristics and heat transfer of impingement/effusion cooling on a flat plane were numerically analyzed by ANSYS-CFX software. The simulation for the working conditions with and without solid domain was carried out to find their influence on the cooling performance. The influence of solid thermal conductivity and effects of blowing ratio on the flow structure, vortex intensity, total cooling efficiency and flow efficiency were discussed. The results show that impingement/effusion cooling has advantages of both impingement and film cooling to protect the solid surface well. When blowing ratio becomes larger, the impingement is more effective, and the film cooling acts adversely. But the impingement cooling is more influential so the total cooling efficiency increases. The film cooling part has the largest local pressure loss coefficient, and total pressure loss coefficient increases with the increasing blowing ratio. When the solid thermal conductivity becomes larger, the impingement cooling is more influential and the total cooling effectiveness increases.关键词：impingement/effusion cooling;numerical simulation;blowing ratio;total cooling effectiveness764|5|4更新时间：2025-07-09
- 摘要：Three-dimensional unsteady Reynolds-averaged Navier-Stokes(URANS)equations coupled with a fully-developed shear stress transport(SST)turbulent model were used to investigate the sealing performance of rim seal. The sealing behaviors of conventional radial rim seal at different pressure ratios and rotational speeds were numerically predicted. Based on solving the turbulence transport governing equation for additional variable used for tracing fluid, the sealing effects of conventional radial rim seal were obtained at four different pressure ratios and rotational speeds. And then the investigation on the effect of relative location of rotor and stator on the sealing performance of the radial rim seal was carried out. Numerical results showed that pressure ratio and rotational speed are the key factor influencing the seal performance of radial rim seal. Pressure ratios and rotational speeds change the sealing efficiency by influencing the blade leading edge's potential field. The seal efficiency decreases with the pressure ratio because of enhancing non-uniformity of the circumferential pressure field. And the seal efficiency increases with the rotational speed because of the improvement on the non-uniformity of circumferential pressure field. The change of relative position between vane blade and rotor blade would induce the variation of interaction between the pressure potential fields at vane blade wake and rotor blade leading edge, and hence influencing the seal efficiency. With the blade rotating, the ingestion in wheel space presents periodic enhancing and weakening.关键词：turbine stage;rim seal;sealing effectiveness;numerical simulations775|5|2更新时间：2025-07-09
- 摘要：In order to reveal the coupling interaction between centrifugal compressor's through flow and hub-shroud labyrinth seal leakage flow, the inlet stage of a centrifugal compressor in natural gas pipeline was studied in this paper. Numerical simulations of internal flow fields of the centrifugal compressor stage with and without labyrinth seal were carried out. The results showed that the model with seal has lower isotropic efficiency and total-to-total pressure ratio than the model without seal, especially at low flow rates. Both the seal cavities with the alternate long-short seal teeth of identical thickness and with the trapezoid seal teeth are capable of dissipating the gas pressure and kinetic energy into heat energy, thus significantly decreasing the leakage flow rate. The mixing of leakage flow and through flow can lead to the separation of through flow near inlet and outlet of centrifugal impeller. Subject to shroud-side leakage flow, the through flow near the impeller inlet suffers significant increase in entropy and hence a deterioration in the aerodynamic performance of the whole stage. The present work would provide a theoretical foundation for the in-depth understanding of the interaction between through flow and hub-shroud side leakage flow and for the improvement in the aerodynamic performance prediction model of the in-service centrifugal compressors.关键词：centrifugal compressor;labyrinth seal;stage environment;through flow;leakage flow885|5|2更新时间：2025-07-09
- 摘要：Aiming at improving the design performance of hydraulic torque convertors, a method of selecting applicable impeller planar flow model was put forward, taking twin-turbine torque converter as the study object, to study the dynamic mapping relationship between the impeller planar flow model and hydraulic torque convertor design performance(starting torque ratio, efficiency and maximal capacity). Nine composite models were designed for computational fluid dynamics simulation tests by orthogonal test method with three classic planar flow models(irrotational flow, uniform flow and rotational flow models)and four impellers. The accuracy of CFD simulation was proved by hydraulic torque convertor bench test. The performance affected by different impeller planar flow models was analyzed quantitatively according to the results of simulation test. The performance could be enhanced by selecting appropriate impeller planar flow model for all the torque converters where the blade angle combinations can meet the basic design performance requirements: considering the evaluation criteria of torque ratio, uniform or rotational flow models should be selected to design the stator and irrotational flow model should be selected to design the first turbine. Focusing on efficiency, uniform or irrotational flow models should be selected to design the stator and irrotational flow model should be selected to design the pump. To get maximal capacity, uniform flow model should be selected to design the stator. With the method proposed in this paper, the performance could be improved by changing the planar flow model without changing the number of blades, the blade angle and blade thickness. The method could be taken as a good reference for improving the performance of hydraulic torque convertors in engineering.关键词：torque convertor;planar flow model;design performance;orthogonal test;computational fluid dynamics807|5|1更新时间：2025-07-09
- 摘要：To further enhance the efficiency of demister in a flue-gas after desulfuration by wet processes for power plant, a new type of partial reflux cyclone separator with two separation stages is proposed. An experiment rig is constructed to test the performance of cyclone separator, and a droplets generator is designed to produce liquid droplets with different diameters. Malvern particle size analyzer is adopted to obtain the droplet diameter distribution at the inlet and outlet of the separator, and the separation efficiency and resistance loss are measured for different separator parameters under various working conditions. The experiments show that the separation efficiency rises with the increasing number of reflux tanks. At the inlet velocity of 3.9 m/s, the efficiency of separator rises by 66.78% in the case of doubled number of reflux tanks. The efficiency of separator with reflux tanks centered on the separator top reaches higher than that with reflux tanks scattered along the separator. At the inlet velocity of 3.94 m/s, the efficiency rises by16.9%. The height of guide tube affects the efficiency of separator and there exists an optimum ratio of 0.32 between the height of guide tube and the separator.关键词：axial-flow cyclone separator;reflux;liquid droplet;droplet diameter distribution;separation efficiency1090|6|2更新时间：2025-07-09
- 摘要：Taking the inner cooling of 150SD grinding motorized spindle as the application background, an innovative cooling method based on the single-loop thermosyphon with high heat transfer efficiency and without external power supplier is suggested, which could avoid the troublesome rotary seal problem on the inner cooling for spindle shafts. In view of the fact that loop thermosyphon is suitable for the cooling space of the spindle shaft, n-pentane is used as the working medium, and the theoretical analysis on the flow and heat transfer characteristics of the working medium in a single-loop thermosyphon under high centrifugal force is conducted, then an experimental study on the heat transfer performance is carried out. The results show that the operating temperature of the single-loop thermosyphon is stable under the experimental condition and the heat transfer performance reaches its peak value when the filling rate is 60%, and the corresponding thermal resistance is only 0.57 ℃/W. The temperature rise of rotor in 150SD grinding motorized spindle is 28.5 ℃, and the temperature rise continuously decreases with the increase of rotary speed. Therefore, the single-loop thermosyphon may have promising application to the inner cooling of motorized spindles.关键词：motorized spindle;shaft cooling;single-loop thermosyphon;pentane;heat transfer characteristics764|5|2更新时间：2025-07-09
- 摘要：To solve the problem of strong impact vibration and frequent overload during the rock break and excavation process of tunnel boring machines, a hybrid magnetic coupler based on flexible drive technology was proposed. According to the structural features of the hybrid magnetic coupler, the calculation formula of air gap magnetic flux density was established by turning “electromagnetic field” into “electric circuit”. Based on the current superposition property, the current was converted to the surface of the copper conductor, and the electromagnetic torque model of the space magnetic field was established by integrating the induced electromotive force along the circumferential direction. To verify the correctness of the theoretical analysis, an experimental prototype of the hybrid magnetic coupler at a scale of 1:2 was designed and produced. Then simulation verification and experimental measurement for its mechanical behavior were performed. Results show that under the same slip ratio, the relative errors among theoretical, experimental and simulation values are less than 10%; and under the condition of same volume size, the transmission ability of the hybrid magnetic coupler is stronger compared with that of the general double-disc type magnetic coupler. Compared with the hard rock boring machine with the same capacity of asynchronous motor, the linear operating region of the hard rock boring machine equipped with the hybrid magnetic coupler is wider, and the mechanical behaviors are soft, so the overload protection ability is stronger. This research may provide a reference for design and application of mechanical equipment under great start impact and frequent overload.关键词：tunnel boring machine;hybrid magnetic coupler;flexible drive;electromagnetic torque model;mechanical behavior877|6|5更新时间：2025-07-09
- 摘要：Focusing on the inaccuracy of state-of-charge estimation of lithium battery, the electrochemical impedance spectroscopy of different state-of-charge stages of lithium battery is analyzed, and a fractional impedance model and a fractional Kalman filter are then proposed following the fractional modeling idea. The parameters of the model are identified in the hybrid pulse power characteristic(HPPC)test, and the state-of-charge estimation of lithium battery is accomplished by fractional Kalman filter. The result shows that the working voltage error is below 0.05 V and the estimation of state-of-charge error is below ±1%, thus the model is accurate enough to describe the characteristic of lithium battery and the fractional Kalman filter improves the accuracy of state-of-charge estimation of lithium battery.关键词：lithium-ion batteries;fractional impedance model;fractional Kalman filter;estimation of state of charge741|5|5更新时间：2025-07-09
- 摘要：To fully tap the fuel saving potential of city plug-in hybrid buses, a variable parameter control strategy according to the influence of driving cycle is proposed to achieve the reasonable distribution of vehicle power. The traffic data of 20 buses are collected and the congestion driving cycle, urban driving cycle, suburban driving cycle and comprehensive driving cycle of the urban buses are fitted with short-stroke analysis method. The vehicle control strategy key parameters of the four driving cycles in the same driving range are optimized with combinatorial optimization algorithm. The selected first three sets construct an identification database which is embedded into the fixed parameter control strategy based on the comprehensive driving cycle optimization. Euclidean distance and proximity criterion are used to judge the type of the current driving cycle in real time and automatically call the variable parameter control strategy of the optimal control parameter. The results show that in the same experimental driving cycle, the integrated fuel consumption of vehicle reduces by 5.12% compared with the fixed parameter control strategy. The rapid control pattern test indicates that the integrated fuel consumption of vehicle in comprehensive driving cycle reduces by 4.9% compared with the fixed parameter control strategy.关键词：plug-in hybrid electric bus;variable parameter control strategy;vehicle control;driving cycle recognition949|5|5更新时间：2025-07-09
- 摘要：The study on the application of multi-sensor cross cueing technology in sensor alliance was conducted, where multi-sensor cross cueing technology is used to build and update sensor alliances to solve the problem of dynamic control of sensor alliances. When building a sensor alliance, the objective function is built aiming at saving sensor resource and enhancing the resource utilization; and when updating a sensor alliance, the sensor management structure predict then update is presented. The multi-sensor cross cueing distributed algorithm based on multi-dimensional consultation was designed for resolving and updating the sensor alliance scheme. The simulation results indicate that the model in this paper is effective. Compared with auction algorithm and particle swarm, the convergence rate of the algorithm proposed in this paper is the fastest and with better results. Compared with the method of detect, then update the method of predict then update is more suitable to the condition where the combat situation often changes quickly.关键词：sensor alliance;dynamic control;multi-sensor cross cueing;target tracking574|5|3更新时间：2025-07-09
- 摘要：Aiming at the problem of the basic prediction algorithm with relative low prediction accuracy, a novel and improved prediction algorithm NLWEPrediction is proposed based on non-linear weighted and ensemble learning. It combines the advantages of linear ensemble learning and the relationship between the base predict algorithms, which corrects the prediction deviation and uses gradient descent method to calculate the model parameters. The experiments proved that the NLWEPrediction's mean squared error in datasets is lower than 250, and the mean absolute difference is lower than 13. The algorithm was compared with its four base prediction algorithms, other two ensemble prediction algorithms Bagging and Stacking and original NLWEPrediction for efficiency analysis. Experimental results showed that NLWEPrediction has obviously low mean square error and average absolute error. The prediction accuracy is improved. So, adding the nonlinear regression terms can improve the capability of ensemble classifier.关键词：software defect series;prediction algorithm;software defect;ensemble learning721|6|1更新时间：2025-07-09
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