Optimization of impedance boundarycontrolled casing treatment on subsonic compressors

Dakun Sun,Yuqing Wang,Jia Li,Zihan Shen,ChunWang Geng,Xu Dong,Xiaoyu Wang,Xiaofeng Sun 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

Foam-metal casing treatment (FMCT) has the potential to enhance the stall margin while attenuating the broadband noise of compressors. An optimized structure of FMCT backed with an air gap was developed in this study with the basis of a prediction model. The eigenvalue theory with a linear perturbation assumption was employed to judge the stability of the compression system, where the casing treatment was considered as an impedance boundary condition. The effect of this kind of casing treatment on the compression system is introduced through the equivalent surface source method. The transfer element method was applied to match the relations between perturbation parameters on the surface of each section. Prediction results showed that the double-layer configuration has better stall margin improving ability, with experimental results on the steady characteristics confirming a 39.5 % stall margin improvement. The mechanism of exerting damping on the system and thus suppressing stall precursors was proved.

Parameter Sensitivity Study on Static and Dynamic Mechanical Properties of the Spatial Y-shaped Tied Arch Bridge

Jianpeng Sun,Zihan Tan,Jiaju Zhang,Wenwu Sun,Li Zhu 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2

The spatial Y-shaped tied arch bridge is a rare form of innovative bridge on arch bridges around the world. It has important reference significance for the design and construction of bridge engineering worldwide. This arch bridge is novel in design and adopts single and double arch ribs combined structure. However, as a novel bridge type, its force situation is indetermination, so it is very important to study its mechanical properties and parameter sensitivity. In order to study the mechanical properties of the spatial Y-shaped tied arch bridge and the influence of structural parameters, this paper takes a spatial Y-shaped tied arch bridge under construction in China as the research object. The finite element software MIDAS Civil is used to establish the bridge model. The finite element model is used to analyze the static and dynamic performance of the spatial Y-shaped tied arch bridge under the use stage and the mechanical change trend under the influence of different rise-span ratios and double arch bifurcation angles. The results of single arch rib and double arch rib under constant load and live load are compared under different structural parameters in this paper, and the parameter sensitivity analysis of statics and dynamics is carried out. These analyses provide the adjustment basis and design reference for the design of the special-shaped arch bridge in the future.

Key Construction Technology and Monitoring of Long-Span Steel Box Tied Arch Bridge

Jianpeng Sun,Jinbin Li,Yingbiao Jiang,Xiaogang Ma,Zihan Tan,Gaolin Zhufu 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.1

As a composite system bridge, half-through steel box tied arch bridge combines the arch mainly bearing pressure and the beam mainly bearing bending moment, gives full play to their respective advantages, and has the two characteristics of large span capacity of arch bridge and strong adaptability of simply supported beam bridge to foundation. However, in the construction process, due to the complex construction technology and structural stress behavior, the hoisting of arch rib, the tensioning of tie rod and suspender are accompanied by the change of internal load, which is a challenge for bridge construction. Taking the Lancang River Liming Bridge in Xishuangbanna, Yunnan Province as an example, this paper introduces a new construction scheme of arch bridge, introduces the structural characteristics of cable hoisting system, and puts forward the construction monitoring method. The response of arch rib, suspender, tie rod and main beam is monitored by health monitoring system and compared with the analysis results of finite element model to ensure that the stress and deformation of the structure under various working conditions are in a reasonable state. The results show that the proposed construction scheme can meet the safety and quality requirements of bridge construction, and the finite element model can reasonably predict the bridge behavior in construction. This study is expected to promote the construction of long-span half through steel box tied arch bridge.

Seismic Resilience Assessment of the Hybrid Bridge Pier Based on Fragility Analysis

Jianpeng Sun,Weichao Xu,Zihan Tan 한국강구조학회 2024 International Journal of Steel Structures Vol.24 No.2

At present, the seismic structure of recoverable functional bridges based on seismic resilience is one of the hotspots in bridge seismic engineering research. Therefore, a new type of hybrid piers is designed in this paper, which mainly relies on replaceable components to achieve repairable structural performance after earthquakes. At the same time, four-level seismic fortifi cation objectives based on seismic resilience is proposed, and the follow-up stiff ness phenomenon is found on this basis. The fi nite element software OPENSEES was used to perform IDA analysis on a hybrid pier and an ordinary reinforced concrete (RC) pier. The fragility curves and seismic resilience curves of two piers were compared, and the seismic resilience performance and the follow-up stiff ness phenomenon of the hybrid pier were studied. The results show that under the action of diff erent seismic waves, the top displacement angle of the pier of the hybrid pier is slightly larger than that of the ordinary RC pier, but the overall diff erence is not large. The fragility curve of the hybrid pier is slightly larger than that of the ordinary RC pier. However, with the damage to the hybrid pier, the follow-up stiff ness phenomenon impacts the seismic performance, which reduces the seismic force acting on the structure and improves the seismic resilience of the structure. The post-earthquake recovery time of two piers under diff erent damage states was determined. Combined with the fragility curves, the seismic resilience curves of two piers were presented. The resilient index of the hybrid pier was always maintained at 0.9–1, and the seismic resilience performance was excellent.

Seismic Resilience-Based Design Method for Hybrid Bridge Pier Under Four-Level Seismic Fortifications

Jianpeng Sun,Zihan Tan 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.5

The hybrid bridge pier can be damaged in stages under earthquakes, and have great repairability after earthquakes, but the existing seismic fortifi cation objectives cannot refl ect the superiority of the hybrid bridge pier. Therefore, higher seismic fortifi cation objectives and the corresponding seismic design method are needed for the hybrid bridge pier. A design example of the hybrid bridge pier was presented. Combined with the seismic ground motion parameter zonation map of China, the four-level seismic fortifi cation objective of the hybrid bridge pier based on seismic resilience is proposed. By formulating the material and structural parameters of the hybrid bridge pier, the seismic force of the pier under the four-level earthquake resistance is calculated. It is shown that with the deepening of the damage degree of the pier, the decrease of the structural stiff ness leads to the increase of the natural period of vibration of the structure, which leads to the decrease of the seismic force acting on the structure, and thus the concept of the follow-up stiff ness is proposed.

Preparation of Fe-Co-P-Gr/NF coating via electroless composite plating as efficient electrocatalysts for overall water splitting

Kaihang Wang,Kaili Sun,Zihan Li,Zunhang Lv,Tianpeng Yu,Xin Liu,Guixue Wang,Guangwen Xie,Luhua Jiang 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.2

The development of electrocatalysts with high activity and low Tafel slope for overall water splitting has become a crucialchallenge to exploit the sustainable energy. Herein, we construct a Fe–Co–P–Gr catalyst on nickel foam (NF) support throughelectroless composite plating to realize the co-deposition of Fe–Co–P alloys and graphene quantum dots. Interestingly,graphene quantum dots exhibit obvious eff ects on electron mobility and active sites of Fe–Co–P–Gr/NF catalyst. In oxygenevolution reaction, the Fe–Co–P–Gr/NF catalyst exhibits a small overpotential of 230 mV at 10 mA cm −2 and fast kineticswith Tafel slope of 37.8 mV dec −1 . Meanwhile, the Fe–Co–P–Gr/NF also has a superior hydrogen evolution reaction performancein 1.0 M KOH. Compared with the Fe–Co–P alloys, the Fe–Co–P–Gr/NF both as the anode and cathode requireonly 1.58 V to reach a current density of 10 mA cm −2 . The successful preparation of Fe–Co–P–Gr/NF electrode throughelectroless composite deposition provides a new path to manufacture electrocatalysts for overall water splitting.

Winding strategy of driving cable based on dynamic analysis of deployment for deployable antennas

Yiqun Zhang,Dongwu Yang,Zihan Sun,Na Li,Jianghua Du 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.11

An optimization method for the winding strategy of the driving cable is proposed based on a dynamic analysis of the AstroMesh antenna deployment. First, considering the effects of the cable net and friction, the driving force for deployment is deduced according to energy conservation. Thereafter, an optimization model is constructed, with the objective of minimum deployment driving power, using design variables consisting of control parameters of the winding length curve of the driving cable; this curve is described by the Bezier curve. Moreover, corresponding to the winding process of the driving cable before and after optimization, deployment experiments for a 2-m aperture deployable antenna prototype are conducted. Finally, the validity and rationality of the optimization method are verified by comparing the simulation and experimental results.

Preparation and sinterability of submicron titanium carbide powders synthesized with phenolic resin as carbon source by carbothermal reduction

Huijuan Qiu,Hongkang Wei,Shifeng Ren,Lingjun Sun,Jia Li,Zihan Wang,Lin Zhao,Chang-an Wang,Zhipeng Xie 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.2

Titanium carbide powders were synthesized under an argon atmosphere using titanium dioxide and pyrolysis carbon derivedfrom pyrolyzed phenolic resin as raw materials. The effects of synthesis temperature, holding time, and C/Ti molar ratio onthe phase composition and morphology of the synthesized powders were investigated. The results show that the pyrolyzedphenolic resin at 1000 ℃ is a carbon source composed of amorphous and crystalline carbon. Increasing the C/Ti molar ratio ofthe mixed powder can reduce the content of titanium oxide impurity, indicating the improvement in the purity of TiC powder. In addition, the C/Ti molar ratio can also significantly affect the morphology of the synthesized TiC powders. SEM and EDSresults exhibit that the atomic content on the surface of TiC particles is closely correlated with the atomic distribution on thesurface of the particles. TiC powder with a median particle size of 384 nm could be synthesized at 1500 ℃ for 30 min at the C/Ti molar ratio of 2.3:1. In addition, the sinterability of the synthesized TiC powder was preliminarily discussed. The hardnessand fracture toughness of the TiC ceramic sintered at 2000 ℃ under 40 MPa with a dwell time of 2 h are 15.92 GPa and 3.22MPa·m1/2, respectively.