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Liu Z.,China Agricultural University | Xiao R.,China Agricultural University | Lu T.,China Agricultural University | Li S.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2012

A swept blade was designed based on changing the stacking line in the meridional plane of an axial flow pump impeller. The high speed fuel axial flow pumps, with swept blades and datum blades respectively, were simulated in the overall operation by the code of computational fluid dynamics (CFD) and the overall efficiency and pump head performance curves were obtained. Using the full cavitation model, the cavitation performances of pumps were predicted under the designed point condition and near stall point condition to investigate the effects of swept blade on the cavitation performance and distribution of pressure on blade surfaces of an axial flow pump. According to the numerical results, the swept blade changes the hump characteristic of the axial flow pump, controls the onset and growth of the secondary flows, and recovers the low-energy fluid on the endwalls. Therefore, the stability of operation in the hump zones is improved. Near stall point condition, the swept blade improves the cavitation characteristic of the pump, changes the pressure distribution on the impeller inlet, and avoids the separated flow on the endwalls. While under the design point condition, the swept blade reduces the cavitation characteristic, the blade surface pressure distribution also presents the pressure difference of the datum blade is higher than the swept blade, resulting in the ability of doing work of the former is better than the latter.


Wang X.,Nanjing Southeast University | Wang Z.,Nanjing Southeast University | Chen J.,Nanjing Southeast University | Cheng M.,Nanjing Southeast University | Xu L.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
2016 IEEE 8th International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016 | Year: 2016

In this paper, a space vector modulation (SVM) based DTC scheme is proposed for the dual three-phase PMSM. This scheme provides an effective solution for multiphase drives by inheriting the advantages of fast dynamic performance and robust control architecture of DTC. Besides, the proposed scheme can suppress the current harmonics induced not only from inherent property of dual three-phase PMSM, but also from nonlinear factors such dead-time and asymmetry in drives. The vector synthesis process in the scheme has been simplified compared to conventional SVM-DTC scheme. The experimental results are given to verify the validity of the proposed SVM-DTC scheme. © 2016 IEEE.


Wang Z.,Nanjing Southeast University | Liu B.,Nanjing Southeast University | Zhang Y.,Nanjing Southeast University | Cheng M.,Nanjing Southeast University | And 2 more authors.
Energies | Year: 2016

Three-port isolated (TPI) bidirectional DC/DC converters have three energy ports and offer advantages of large voltage gain, galvanic isolation ability and high power density. For this reason this kind of converters are suitable to connect different energy sources and loads in electric and hybrid vehicles. The purpose of this paper is to propose chaotic modulation and the related control scheme for TPI bidirectional DC/DC converters, in such a way that the switching harmonic peaks can be suppressed in spectrum and the conducted electromagnetic interference (EMI) is reduced. Two chaotic modulation strategies, namely the continuously chaotic modulation and the discretely chaotic modulation are presented. These two chaotic modulation strategies are applied for TPI bidirectional DC/DC converters with shifted-phase angle based control and phase-shifted PWM control. Both simulation and experiments are given to verify the validity of the proposed chaotic modulation-based control schemes. © 2016 by the authors.


Wang Z.,Beihang University | Xing Y.,Beihang University | Liu X.,Beihang University | Zhao L.,Beihang University | Ji Y.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
Applied Thermal Engineering | Year: 2016

The heat transfer process among droplet, film and bubble is selected as the local characteristic process of spray cooling to build a multiphase flow model. Volume of fluid (VOF) method is employed to simulate the transient process, in which single or multiple droplets impact on a liquid film with a vapor bubble growing, considering the effects of surface tension, gravity and vapor-liquid phase transition. The effect of vibration environment is analyzed by setting vibration boundary condition, and a far broader range of vibration condition is calculated in light spray and dense spray to identify the effect. Heat is mainly removed by strong convection due to the droplet impact. It is significant to form stabilized and intact film during spray cooling. Heat transfer process can be mainly separated into four stages: 1. before the impact; 2. droplet impacts on the surface and forms thinner film on the surface; 3. film extends outwards; 4. film breakage. In dense spray cases, the third stage is barely observed due to continuous impacting of droplets, and mainly all the cases show that vibration has invigorating effect on heat transfer. © 2016 Elsevier Ltd


Wang Z.,Nanjing Southeast University | Wu B.,Ryerson University | Xu D.,Ryerson University | Cheng M.,Nanjing Southeast University | Xu L.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
IEEE Transactions on Industrial Electronics | Year: 2016

The purpose of this paper is to develop a model and propose control strategies to mitigate dc-link current ripple for current-source grid-connected converter (CSGCC) under unbalanced grid conditions. Based on the model of instant active power under unbalanced grid conditions, this paper proposes the optimized negative-sequence current references for eliminating the double-frequency oscillations on active power at ac side of CSGCC. Both the single CSGCC and the paralleled CSGCCs are considered in this paper. In order to track the asymmetric current references more accurately while maintaining LC resonance damping, the hybrid current controller is proposed by combining the closed-loop fundamental current controller under double synchronous frames and the closed-loop high-bandwidth harmonic current controller under stationary frame. The design of the hybrid current controller is analyzed. Finally, the experimental results are shown to verify that the control strategies can mitigate the dc-link current ripple effectively, and also provide good LC resonance damping performance for grid currents. © 1982-2012 IEEE.


Wang Y.,Beihang University | Qin Y.,Beihang University | Guo S.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2013

Single joint performance of hydraulic robot directly affected the overall performance of the robot control. The uncertainty and time-varying of hydraulic system parameters decreased the control precision and response speed of single joint, which requested the single joint controller had robustness. A mathematic model of servo valve controlling swaying hydraulic cylinder was established and the system parameter uncertainty was analyzed. Based on quantitative feedback theory (QFT), a single joint robust controller was designed. Simulation shows that the controller has strong robustness against the slope interference and sine interference. Experimental results verify the correctness of the robust controller.


Ouyang X.,Zhejiang University | Li F.,Zhejiang University | Zhu Y.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration | Yang S.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration | Yang H.,Zhejiang University
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2016

Heavy load aviation load simulator is the ground simulation platform, which is used to simulate the real work load of the heavy-duty aircrafts such as C919 and Yun-20. A heavy-duty aviation load simulator is developed to achieve large load in limited space and the asymmetric cylinder is used as the actuator. In order to eliminate the influence of surplus force on the loading precision of the overloaded simulator, the influence of the bidirectional motions of the cylinder and the nonlinear flow gain coefficient of the servo valve for the feedforward compensation function are analyzed, and the nonlinear parameter estimation controller has been proposed. Meanwhile, the influence of dynamic parameters' variation (such as acceleration) and static parameter error for eliminating the excessive force is analyzed, and the parameter optimal controller is developed. Both simulation and test results show that the performance of the developed feedforward compensation controller has been improved by more than 50% in the loading precision and the eliminating ability of the surplus force, compared to the traditional feedforward compensation controllers. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.


Tian L.,Nanjing University of Aeronautics and Astronautics | Fu Y.,Nanjing University of Aeronautics and Astronautics | Yang L.,Nanjing University of Aeronautics and Astronautics | Xu J.,Nanjing University of Aeronautics and Astronautics | And 3 more authors.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2013

In order to investigate the influence law of chip formation process affected by grinding speed, the single-grain tests are carried out on the difficult to cut materials superalloy GH4169. The single-grain grinding forces are measured. The trances and chips morphologys of the single-grain grinding tests are observed and analyzed to calculate the critical thickness of chips formation. The speed effect on the grinding process scratches and grinding forces are studied systematically in the grinding wheel velocity range 20 m/s to 165 m/s. The results show that the grinding speed affects the division of grinding process and the critical thickness of chip formation, and the single-grain grinding forces first increase then decrease and increase finally with the increasing grinding velocity. Machinability changes due to the speed effect, and these changes caused by the alternative variation of the leading position between the strain rate strengthening effects and the thermal softening effects on the difficult to cut materials. Serrated chip occurs during single-grain grinding superalloy, as the grinding speed increases, the grade of serrated tooth grows and the pile up rate of the single-grain grinding grooves decrease first then increases, these phenomenon indicated that mechanism of chip formation due to the speed effect. © 2013 Journal of Mechanical Engineering.


Liu Y.,Nanjing University of Aeronautics and Astronautics | Yao E.,Nanjing University of Aeronautics and Astronautics | Xu H.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2012

Aiming at the monitoring problem of running state of axial plunger pump used on some airplanes, a new fault diagnostic method based on analyzing and processing the vibration signals of hydraulic pump shell was presented. Through modeling the original data sequence obtained with accelerometers, using optimized particle filtering to reduce noise, extracting the eigenvalue of the autoregressive spectral of the filtered signals and analyzing the working conditions of the hydraulic pump according to its working principle, the fault analysis and diagnosis of hydraulic pump are achieved. The study shows that particle filtering can effectively follow the original signal and filter out noise jamming; and the proposed fault diagnosis method can effectively extract the fault characteristic value and achieve fault diagnosis and identification.


Nie J.,Northwestern Polytechnical University | Nie J.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration | Pan Q.,Northwestern Polytechnical University | Shi G.,Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration
Nanjing Li Gong Daxue Xuebao/Journal of Nanjing University of Science and Technology | Year: 2014

This paper discusses the performance of the designed digital electro-pneumatic cabin pressure control system for a cabin pressure schedule of transport aircraft. For the purpose of this study, an experimental setup consisting of simulated hermetic cabin and altitude simulated chamber is configured for cabin pressure control system operation. A series of experimental tests are executed to evaluate the performance of cabin pressure control system. The parameters of proportional integration differentiation (PID) controller are optimized. In the optimization process, the variation regularity of the rate of cabin pressure change under various conditions is considered. An approach that makes the rate of cabin pressure change priority control based on the flight status model is proposed and verified experimentally. Experimental results show that the proposed approach can be adapted to the designed digital electro-pneumatic cabin pressure control system and that better cabin pressure schedule and rate of cabin pressure change can be obtained.

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