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RISS 인기검색어
- 검색키워드
- 저자 : Kaicheng Zhang (검색결과 4 건)
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Kaicheng Ding,Yan Zhang,Jinjun Liu,Rui Cao,Yuetao Hou,Xin Meng 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper, a boost type Power Factor Corrector is proposed to deal with the inherent issue of double line frequency power ripple, namely power coupling, in single-phase AC/DC conversion systems. The proposed converter is embedded with an active buffer circuit and the redundant capacitor and power switches enable active power decoupling and an all-film-capacitor implementation. The active power decoupling control scheme in this paper is based on the direct control of ac power and dc power and is therefore relatively easy to implement. The former one helps to achieve unit power factor at ac side while the latter one helps to regulate dc side output voltage and as a result the double line frequency power ripple could be automatically transferred onto the buffer capacitor of the converter. Theoretical analysis, simulation and experiment results are provided in the paper.
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Gu Kaicheng,Shao Shaojin,Zhang Yongbin 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.2
In itself, there is a very thin boundary layer physically adsorbed to the bearing surface. When the bearing clearance is far larger than the thickness of this layer, the boundary layer effect in the bearing is negligible, and conventional hydrodynamic lubrication theory just addresses on this topic. However, with the worsening of the operating condition, the bearing clearance can be largely reduced and comparable to the thickness of the adsorbed boundary layer. For this case, the effect of the adsorbed boundary layer must be considered. The present paper presents the multiscale analysis for the performance of the hydrodynamic journal bearing in a wide range of bearing clearance considering the effect of the physically adsorbed boundary layer. The calculation results indicate for how low bearing clearances the adsorbed boundary layer effect should be incorporated. When the minimum bearing clearance is on the same scale with the thickness of the adsorbed boundary layer, the hydrodynamic pressure in the bearing is locally largely increased by the effect of the adsorbed boundary layer, and the load-carrying capacity of the bearing is correspondingly largely increased. This is particularly significant for a strong fluid-bearing surface interaction. The study shows the great contribution of the physically adsorbed boundary layer to the performance of the hydrodynamic journal bearing in the condition of low surface clearances, and indicates the necessity of the multiscale analysis for this bearing.
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BaoLing Cui,Kaicheng Zhu,Yuliang Zhang,Peifeng Lin 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10
Cavitation is a problem that must be considered when designing and operating a pump. This study proposes an active method using a jetting device to improve its cavitation performance. The influence of jetting flow rate on the external characteristics and cavitation performance of a centrifugal pump is analyzed through numerical simulation and experiment. Results show that the jetting fluid can improve the cavitation performance of a pump and the effect is most evident in the 6 % jetting flow rate. The distribution of entropy generation at the inlet pipe before the impeller shows that jetting flow can increase hydraulic loss in the pipe, thereby diminishing the performance of the centrifugal pump. An analysis of the transient cavitation flow in the centrifugal impeller under 6 % jetting flow rate reveals that the generation, development, and rupture of bubbles deteriorate the flow structure in the passage, thereby resulting in unstable flows and forces.
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Wendong Yang,Yiwei Li,Ling Wang,Kaicheng Zhang,Zhicheng Gong 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.6
Most of the rock mass in nature contains a large number of joints, faults and other defects, which make the rock mass have the characteristics of discontinuity and anisotropy, and easily lead to instability and failure of rock engineering. A great quantity of engineering practices show that the bolt has a significant supporting effect on jointed rock mass. Therefore, it is of great significance to study the deformation and failure characteristics of jointed rock mass and the crack arrest effect of bolt for the safety and stability of engineering. A reasonable numerical model of bolted rock samples with non-persistent joints is established by using a three-dimensional Particle Flow Code (PFC) based on the laboratory rock specimens, and the uniaxial compression numerical test is carried out. The results indicate that (1) the numerical simulation results are in good agreement with the laboratory test results, and the variation trend of strength is basically consistent; (2) the different joint angles and anchorage angles result in variations in the mechanical properties of bolted specimens with non-persistent joints; (3) the joint angle has a significant effect on the failure mode of the specimen; (4) the existence of bolts can effectively limit the initiation and propagation process of micro-cracks, and greatly improve the mechanical properties of the specimen containing non-persistent joints.
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