Grid Independence in the Study of Boundary Layer and Its Application in Hypergolic Propellants

Hong Xiao,Zhe-Zhu Xu,Dong-Yang Li,류성기 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.7

Numerical simulation and experimental validation of a hypersonic flat plate and isothermal turning wall flow were conducted in the current study. The investigation was based on three kinds of grids (Grid1, Grid2, and Grid3) with laminar flow and three types of turbulence models (BL, SA, and SST). Under the same initiation and different turbulence models, the convergence process of the friction drag coefficient CP and the Stanton number St of a hypersonic flat plate flow revealed four results. First, the flow turbulence effect in the BL model simulation was responsive to CP and St. Second, the SA and SST model simulations both reflected the development process of flow turbulence. Third, the flow turbulence effect in the SST model simulation did not gradually emerge until the laminar flow simulation was sufficient. Moreover, the SA model simulation did not exist on such obvious hysteresis. Fourth, by comparing CP and St of a hypersonic flat-plate laminar simulation under the three grids, the errors of the calculation results of Grid2 and Grid3 were small.

Optimization Scheme of Genetic Algorithm and Its Application on Aeroengine Fault Diagnosis

Hong Xiao,Zhe-Zhu Xu,김래성,Dong-Yang Li,류성기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.4

An adaptive model is proposed based on genetic algorithm to predict the characteristic map of aeroengine components. The differencefunctions, of the primary performance parameters between numerical model and test data, are taken as objective function. Thecoupled factors of component characteristics' map as optimized parameters are considered.The difference of the main performanceparameters and process parameters between the adaptive model and the test data are shown to be within the range of0.05%.Meanwhile, the section's total temperature and pressure are controlled within 1%. Furthermore, an aerongine fault diagnosismodel is developed by the small deviation equation method in which the gas path analysis is implemented and the symptom andmeasuring parameters represent engine performance parameters' variation. It shows that the selection and relatively variable valueof symptom parameter have great effect on fault diagnosis error, and the best selection of value is 1/3 of threshold. The relative errorof variable value between the symptom parameter of fault diagnosis model and the real fault can be found to be controlled within5% and it can do the correct evaluation of fault type. And the fault diagnosis model has no misdiagnosis in all the performedconditions.

Quasi-Steady-State Scheme and Application on Prewhirl Flow and Heat Transfer in Aeroengine

Hong Xiao,Zhe-Zhu Xu,류성기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.2

For solving three-dimensional complex unsteady flow to predict aerodynamic characteristics of turbine disc cavity in aeroengine, aquasi-steady-state scheme is proposed. To validate and get reliable turbulence model, three-dimensional numerical studies, of turbinedisc cavity prewhirl flow and heat transfer, are conducted. For comparison, unsteady state computational fluid dynamics simulationsof prewhirl flow are also performed. Five turbulence models, including standard k-å model, RNG k-å model, Realizable k-å model,SST k-ù model and RSM model, are applied both quasi-steady-state scheme and unsteady CFD. Then, reliable quasi-steady-statescheme is obtained and the feasibility, instead of unsteady-state CFD simulation for reducing time resource, is verified. Furthermore,investigations of prewhirl flow and heat transfer in turbine disc cavity of aeroengine are conducted by the proposed quasi-steady-statescheme. It was found that the rotation Reynolds number should be increased to strengthen the blade cooling and weaken the heattransfer in turbine disc cavity. All the results are applied in the design of aeroengine. Also, it proves that quasi-steady-state schemeis effective in the prediction of aerodynamic characteristics in aeroengine.

Atomization Characteristics of Gelled Hypergolic Propellant Simulants

Hong Xiao,Yang-Yang Shi,Zhe-Zhu Xu,김래성,Dong-Yang Li,류성기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.4

Gelled propellants are attractive candidates due to their desirable physical and chemical properties which reduced hazardoussituations while providing significant flexibility over solid propellants. However, complications were raised by injection andatomization due to their non-Newtonian rheological and flow properties caused due to its high viscosity. In this paper, the simulationmethod and experimental system were proposed, and the atomized characteristics of gelled-hypergolic-propellant stimulants withimpinging jet injector were also investigated. The influence law was studied to investigating the injection angle and velocity. Theeffects of the generalized Reynolds number on the jet velocity are presented in a regime diagram. It was observed that spray patternswere depended on the jet exit velocity from the shadowgraph images. And then, it was found that the impingement angle and the jetvelocity play the important role in the near-field jet stream characteristics in this paper

Study on Flow and Heat Transfer of Small Scale Gas Flow for Air Cooling System

Hong Xiao,Yang-Yang Shi,Zhe-Zhu Xu,Dong-Yang Li,류성기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol.16 No.12

The small scale pipe plays an important role in the heat and mass transfer of industrial application. For the study of the flow characteristics in small scale pipe, a modal mixed Discontinuous Galerkin (DG) method was proposed for solving axial-symmetrical Navier-Stokes (NS) equations with solid slip boundary conditions. A new limiter of modal DG was proposed. And, the special treatments of velocity slip and temperature jump in wall solid boundary were given in the numerical scheme. Extensive numerical studies for the flow characteristics of small scale pipe were conducted. For validation, the comparison between the present study and experiment data were performed. The heat transfer coefficients and frictional factor are found to be increased with the diameter decreasing. Furthermore, it is observed that the frictional factor of small scale pipe is larger than that of macro scale pipe. And, the proposed DG-NS method provides a new way for the investigation of the flow characteristics in small scale flow.

Microstructure characteristics and hydrogen storage kinetic of nano MgNi‑REO alloys

Hongxiao Tian,Xinghu Yan,Xia Li,Feng Hu,Yongzhi Li,Zengwu Zhao 한국탄소학회 2023 Carbon Letters Vol.33 No.7

Mg81Ni19-8wt.% REO (oxides of Lanthanum and Cerium) alloys were successfully prepared using mechanical alloying method with Mg-Ni alloy and REO powder. Phase analysis, structural characterization, and microstructure imagine of the alloys were conducted using X-ray diffraction (XRD), metallurgical microscope, and transmission electron microscopy (TEM) methods. Multi-phase structures, including the primary phase of Mg2Ni and several secondary phases of Mg + Mg2Ni, MgNi-LaO, and MgNi-CeO, were found in in the as-cast Mg81Ni19- 8wt.% REO alloys. XRD and TEM results showed that Ce exhibits variable valence behavior at various stages, and the addition of REO promotes the nanocrystalline of the alloy. The hydrogen absorption capacity of ball-milled Mg81Ni19 and Mg81Ni19- 8wt.%REO alloy for 2 h at 343 K is 1.34 wt.% and 1.83 wt.%, which are much larger than 0.94 wt.% of as-cast Mg81Ni19 alloy. The addition of REO led to a decrease of the thermal decomposition temperature of the alloy hydride by approximately 20 K and a reduction of the activation energy of the hydrogen desorption reaction by 10% and 13%, respectively.

SYNTHESIS OF MAGNETIC SBA-15 AND Fe–SBA-15 MESOPOROUS NANOCOMPOSITES WITH COBALT FERRITES

HONGXIAO JIN,LIANG LI,MIN CHEN,JINGCAI XU,BO HONG,BAO HUANG,DINGFENG JIN,HONGLIANG GE,XINQING WANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.3

A new nanocomposite based on SBA-15 mesoporous materials combined with Fe_2O_3 and CoFe_2O_4 nanoparticles was prepared via sol–gel growth. The nanostructures and magnetic properties of the SBA-15 nanocomposite were investigated by X-ray diffraction topography, high resolution transmission electron microscopy, and vibrating sample magnetometer. Results indicate that α-Fe_2O_3 nanoparticles are present in the frame or micropores of SBA-15 (denoted as Fe–SBA-15 below) and that CoFe_2O_4 nanoparticles are confined in the mesoporous channels of Fe–SBA-15. Our results also reveal that the addition of CoFe_2O_4 and α-Fe_2O_3 magnetic nanoparticles critically affects their magnetic properties. The saturation magnetization of the SBA-15 nanocomposite is attributed to ferrimagnetic CoFe_2O_4 nanoparticles and antiferromagnetic α-Fe_2O_3 nanoparticles, whereas the coercivity increases with the content of CoFe_2O_4. Moreover, the presence of the couple exchange interaction between the magnetic nanoparticles is confirmed, which can enhance the magnetic properties of the SBA-15 nanocomposite.

One-Step CVD Synthesis of Few-Layer SnS2/MoS2 Vertical Heterostructures

Hongxiao Zhao,Yong Yan,Xiaohui Song,Aodi Dong,Jian Su,Huimin Jia 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.10

Constructing van der Waals (vdW) heterostructures with various-layered two-dimensional (2D) materials is attractive to design various materials and devices. For controllable fabrication of vdW heterostructures, it is very important to make the growth process clear. In this work, SnS2/MoS2 vertical heterostructures were synthesized by the one-step chemical vapor deposition (CVD) method. The bottom MoS2 triangle layers can be partially or completely covered by SnS2 layers. The interlayer charge separation was also observed in the heterostructures by photo-luminescence (PL) spectroscopy. The growth mechanism of SnS2/MoS2 vertical heterostructures was also discussed for the first time. MoS2 triangle layers form on the substrates at first and then grow a top layer of SnS2. This study will provide an important and practical method, as a guidance to prepare high-quality vertical heterostructures.

Synthesis and Photocatalytic Properties of SnSe2/Se Heterojunction Films

Jing Li,Hongxiao Zhao,Yan Lei,Qingyuan Yang,Zhi Zheng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.4

SnSe2/Se heterojunction films were successfully grown on fluorine-doped tin oxide (FTO) glass for the first time via a one-step solvothermal route using magnetron sputtered Sn metallic precursors, Se powders as selenium source, cyclohexanol as solvent and cyclohexanol as auxiliary solvent, respectively. The SnSe2/Se heterojunction films consisted of Se nanoparticles or nanorods cluster and SnSe2 network surface layers. The crystalline phase and morphology of SnSe2/Se films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), respectively. The photocatalysis measurements of the products for rhodamine Blue (RhB) demonstrated that SnSe2/Se heterojunction films revealed better dye degradation properties than SnSe2 nanosheet films due to the higher separation rates of photogenerated electron–hole pairs of SnSe2/Se heterojunction films, which can be confirmed by surface transient photovoltage (TPV) analyzer.

The Application Research of Light and Shadow Art in Immersive Experiencess

张寓(Yu ZHANG),崔鸿霄(Hongxiao CUI) Korea Institute for Humanities and Social Sciences 2023 Journal of Global Arts Studies (JGAS) Vol.1 No.1

【背景】当前光影艺术在创造沉浸式空间体验方面逐渐受到重视,成为现代空间设计领域的创新趋势。【目的】本文旨在深入分析光影艺术在创造沉浸式体验中的作用。【方法】通过界定光影艺术和沉浸式体验的概念,探讨光影艺术在沉浸式体验设计中的关键角色,并通过分析多个现代案例,展示其在实际应用中的表现和优势。【结果】研究发现光影艺术能通过塑造环境氛围和加强感官参与,极大地丰富观众的体验。此艺术形式在沉浸式环境中不仅提供视觉美感,还融合了功能性、意识性与交互性。【结论】光影艺术在沉浸式体验设计中扮演着重要角色,其在当前和未来空间设计中展现出显著的潜力和发展趋势,对现代空间设计的创新性和独特性起到了关键推动作用。 [Background] Currently the art of light and shadow is gradually being emphasized in creating immersive spatial experiences and has become an innovative trend in the field of modern spatial design.[Objective] This paper aims to deeply analyze the role of light and shadow art in creating immersive experiences. [Method]By defining the concepts of light and shadow art and immersive experience, the study explores the key role of light and shadow art in the design of immersive experience and demonstrates its performance and advantages in practical application by analyzing a number of modern cases. [Results] The study finds that light and shadow art can greatly enrich the audience's experience by shaping the environmental atmosphere and enhancing sensory engagement. This art form not only provides visual aesthetics in immersive environments, but also combines functionality, awareness and interactivity. [Conclusion] Light and shadow art plays an important role in the design of immersive experiences, and it shows significant potential and development trends in current and future spatial design, playing a key role in promoting innovation and uniqueness in modern spatial design.