Numerical simulation of flow and heat transfer characteristic in straight-through labyrinth seals of aeroengines under eccentric and rotating conditions

Xin Wei,Zhaohui Yao,Feng Jin,Zhixiong Wang,Honghu Ji 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

In order to investigate the leakage and heat transfer of eccentric labyrinth seals, the flow and heat transfer process of eccentric and rotating straight-through labyrinth seals were numerically simulated. The research results show that the influence of eccentricity and rotation on the leakage coefficient is very small, and the change range is less than 2 %. Under the condition of non-eccentricity, the influence of rotating speed on the leakage coefficient depends on the rotating Taylor number. When the Taylor number is greater than 34.2, the leakage coefficient decreases slightly with the increase of rotating speed. At the same pressure ratio and rotating speed, the average Nusselt number of stator is greater than that of rotor. With the increase of eccentricty, the average Nusselt number of the section with larger clearance increases gradually, while the average Nusselt number of the section with smaller clearance decreases gradually.

SONG CHINA’S ROLE IN SHAPING LATE KORYŎ LITERATURE: AN ANALYTICAL SURVEY OF THE TONGMUNSŎN

XIN WEI 계명대학교 한국학연구원 2007 Acta Koreana Vol.10 No.1

This article explores Koryŏ-Song literary relations by conducting an extensive survey of the Tongmunsŏn, the largest literary collection of pre-modern Korea. The chronological distribution of contributions by outstanding Korean writers in the Tongmunsŏn follows a pattern that is hard to explain solely from the point of view of Korean internal political developments. Rather, the pattern reflects the historical and diplomatic contact between Korea and China and connects Koryŏ literature to the broad scope of Chinese literary trends. Yi Kyu-bo and Yi Che-hyŏn, widely known today as two of the best Korean hanmun writers from late Koryŏ, receive focus as being exemplars of Song influences on late Koryŏ literature. In general, Northern Song played an indirect role and Southern Song played a direct role in shaping late Koryŏ literature. The purpose of this study is to open up literary studies on Koryŏ Korea to comparative research and examine the wider civilization of East Asia in a pluralistic manner.

Dark Soliton Solution of the Three-dimensional Gross-Pitaevskii Equation with an Isotropic Harmonic Potential and Nonlinearity in Polytropic Approximation

Xinwei Fan,Yu Zhou,Yalun Li,Ying Wang,Shuyu Zhou 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.3

We study the three-dimensional Fermi gas in an isotropic harmonic trap during the Bardeen- Cooper-Schrieffer superfluid to Bose-Einstein condensate (BCS-BEC) crossover, which is modeled by using the generalized Gross-Pitaevskii equation (GGPE) in the polytropic approximation. We analytically solved the 3D GGPE with a coupled modulus-phase transformation without introducing any additional integrability constraint, reaching the dark soliton-like solution. We find that the dark soliton identified undergoes an oscillation with a constant period over the whole BCS-BEC crossover region, although the amplitude of the dark soliton varies with polytropic index, demonstrating the peculiar nonlinear properties for the system modeled by using the 3D GGPE.

Span limit and parametric analysis of cable-stayed bridges

Xinwei Zhao,Ru-Cheng Xiao,Bin Sun 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.71 No.3

The span record of cable-stayed bridges has exceeded 1,000 m, which makes research on the maximum possible span length of cable-stayed bridges an important topic in the engineering community. In this paper, span limit is discussed from two perspectives: the theoretical span limit determined by the strength-to-density ratio of the cable and girder, and the engineering span limit, which depends not only on the strength-to-density ratio of materials but also on the actual loading conditions. Closed form equations of both theoretical and engineering span limits of cable-stayed bridges determined by the cable and girder are derived and a detailed parametric analysis is conducted to assess the engineering span limit under current technical conditions. The results show that the engineering span limit of cable-stayed bridges is about 2,200 m based on materials used available today. The girder is the critical member restricting further increase in the span length; its compressive stress is the limiting factor. Approaches to increasing the engineering span limit are also presented based on the analysis results.

PROLONG THE SERVICE LIFE OF SWITCH RAIL BY IMPROVED INDUCTION HEAT TREATMENT

Xinwei Zhan,Shuqing Wang 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-

Switch rail is a very important part on the railway track, which not only accounts for the safety of the passing trains but also greatly influences the speed of the train. The higher the speed and the loads of the train the more it demands on the properties of the switch rail. Research shows that the higher mechanical properties of switch rail the longer the service life. Induction heat treatment is a good way of improving the mechanical properties of metallic materials. But the switch rail’s section area changes gradually across the lengthways, which is difficult for induction heating especially for the small section. And the mechanical property of small section of the switch rail is the most important for its service life. The induction heat treatment used past always brings the low hardness on small section which can cause low service life of switch for wearing, or too high hardness because of martensite microstructure which can cause the shelling or even breaking of the switch rail. To prolong the service life of switch rail by higher mechanical properties, we researched the improved induction heat treatment for switch rail by adjusting speed of heating, and adopting compressed air cooling. The results showed that switch rail obtain almost the same high hardness across the length way after the improved induction heat treatment, which is very helpful to extend the service life of switch rail.

Design of Balanced Dual-Band Bandpass Filter with Self-Feedback Structure

Xinwei Chen,Guorui Han,Runbo Ma,Jiangrui Gao,Wenmei Zhang 한국전자통신연구원 2009 ETRI Journal Vol.31 No.4

A balanced dual-band bandpass filter based on λ/2 stepped-impedance resonators and open-loop resonators is proposed in this letter. By employing a type of self-feedback structure, an extra transmission zero is introduced near the common-mode resonance frequency, and the common-mode signal is suppressed. The measured results indicate that the filter can operate in 2.46 GHz and 5.6 GHz bands, and the insertion loss is 1.85 dB and 1.9 dB, respectively. Also, better common-mode suppression is achieved.

Study of Deflection Routing from an Information-theoretic Perspective

Xinwei Zheng,Yuping Hu,Dongjun Luo,Xiaoyun Wu 보안공학연구지원센터 2015 International Journal of Future Generation Communi Vol.8 No.1

Deflection routing is an effective way to improve the efficiency and reliability of data transmission in the network. Information theory, which is the foundation of channel communications, has not yet had a direct impact on network communications. In this paper, we study the deflection routing processes of point-to-point networks from an information-theoretic perspective. It is found that the packet routing processes, which can further be divided into path determination and path switching, are quite analogous to channel communications. And such a corresponding relationship makes it possible to analyze routing processes and its performance with models and concepts in the information theory.

THE PREDICTIVE CODING FOR GEOMETRY IMAGES OF 3D MODELS BASED ON ERROR SENSITIVITY

Xinwei Xue,Masahiro Okuda 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7

In this paper we introduce a predictive coding for the geometry image of 3D models. Based on a fact that in a smooth surface the sensitivity of the error in the normal direction of each vertex is higher than the one in its tangent direction, we propose a predictive coding method for the geometry image. We have compared our proposed method with the conventional method and show that our proposed method is able to decrease the error in the same compressibility.

Micromechanical modeling for viscoplastic properties of enzyme degradable semi-crystalline poly (ε-caprolactone)

Xinwei Yang,Cheng Yang,Shujuan Hou,Yiqi Mao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.11

This work provide theoretical understandings for the enzyme-degradable PCL, and assist its structural designs and engineering applications. An energy-dependent evolution model is developed to reflect the enzyme-triggered decrystallization of crystals and the further dissolution by applying a chain-broken chemical reaction. Then, the mechanical properties of the enzyme-degradable semicrystalline PCL is modelled through the homogenization-based procedure by the volume-average of a collection of laminated inclusions with crystals and amorphous phase. A dual-phase-lag diffusion model is advanced to solve the enzyme concentrations in the PCL. The model is calibrated by the experiments and then applied for the chemomechanical properties of the PCL when under enzyme conditions. Some numerical examples are conducted to discuss effects of the enzyme concentration and the crystallinity on the crystallographic axe evolution as well as the overall chemomechanical properties of the semicrystalline PCL.

Approximate calculation of the static analysis of a lifted stay cable in super-long span cable-stayed bridges

Xinwei Zhao,Ru-Cheng Xiao,Bin Sun 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.5

The sag effect of long stay cables is one of the key factors restricting further increase in the span of cable-stayed bridges. Based on the formerly proposed concept of long stay cables lifted by an auxiliary suspension cable in cross-strait cable-stayed bridges, corresponding static approximate calculations and analytical theory based on catenary and parabolic cable configurations are established. Taking a main span 1400 m cable-stayed bridge as the research object, three typical lifting conditions and the whole process of auxiliary cable lifting are analyzed and discussed. The results show that the sag effect is effectively reduced. The support efficiency is only improved when the cables are lifted above the original cable chord. Reduction of the horizontal component force of the cable is limited. The equivalent elastic modulus and the vertical support stiffness of the lifted cables are significantly increased with increased horizontal projection length and not sensitive to the change of the lifting point position. The scheme of lifting the cable to the chord midpoint is more economical because of the less steel required for the auxiliary suspension cable, but its effect on improving the vertical support efficiency is limited. The support efficiency is better when the cable is lifted to the cable end tangential to the original cable chord, but the lifting force and the cross-sectional area of the auxiliary suspension cable are doubled. The approximate calculation results of the lifted cables are very close to the numerical analysis results, which verifies the applicability of the approximation method proposed in this study. The results of parabolic approximation calculations are approximately equal to that of catenary cable geometry. As the parabolic approximation analysis theory of lifted cables is more convenient in mathematical processing, it is feasible to use parabolic approximation analysis theory as the analytical method for the conceptual design of lifted cables of super-long span cable-stayed bridges.